Control device of automatic transmission

Embodiments of the present disclosure relate to control devices of automatic transmissions which attain multiple shift speeds by changing a power transmission path of a shift gear mechanism by using engagement elements such as clutches and brakes.

A multi-stage automatic transmission is conventionally proposed in which a simple planetary gear and a dual planetary gear having a common carrier are combined with two simple planetary gears, and which attain ten forward speeds and one reverse speed by changing a power transmission path by using four clutches and two brakes (Patent Document 1).

In this multi-stage automatic transmission, the seventh speed is a direct coupling speed at which input and output portions make the same rotation, and the direct coupling speed is attained by engaging three clutches.

Patent Documents

[Patent Document 1] U.S. Pat. No. 8,096,915

In this multi-stage automatic transmission, one of the clutches is disengaged and one of the brakes is engaged in order to shift from the seventh speed as a direct coupling speed to its adjacent shift speed (the sixth speed or the eighth speed). However, in order to shift from the seventh speed to a shift speed that is two or more speeds higher or lower than the seventh speed (what is called “jump shift”), many engagement elements need to be simultaneously operated in many cases. The shifting operation is therefore complicated, which may impair shifting response.

For example, in the case of shifting from the seventh speed to the fifth speed, it is necessary to disengage two of the three clutches and engage the clutch other than the three clutches and to engage one of the brakes.

It is an object of a preferred embodiment to provide a control device of an automatic transmission which facilitates a shifting operation in many cases in the case of performing shifting after a direct coupling speed is attained.

Means for Solving the Problem

According to a preferred embodiment a control device of an automatic transmission including at least four clutches and two brakes, and a shift gear mechanism that can engage or disengage the clutches and the brakes to change a power transmission path to shift to multiple shift speeds is characterized in that

the automatic transmission attains a direct coupling speed (e.g., a seventh speed), which is a shift speed at which input and output portions of the shift gear mechanism make the same rotation, by engaging three of the at least four clutches and disengaging all of the brakes, and

after the direct coupling speed is attained, the automatic transmission engages the remaining clutch in a disengaged state out of the at least four clutches at the direct coupling speed so that all of the at least four clutches are engaged.

The automatic transmission shifts from the direct coupling speed (e.g., the seventh speed) to a predetermined shift speed (e.g., a fifth, sixth, eighth, ninth, tenth, first, or reverse speed) by disengaging two of the four clutches that are in the engaged state at the direct coupling speed after the direct coupling speed is attained and engaging one of the brakes.

The automatic transmission jump-shifts from the direct coupling speed to a predetermined shift speed (e.g., the fifth or ninth speed) by disengaging two of the three clutches engaged in order to attain the direct coupling speed and engaging one of the brakes with the remaining clutch, which is engaged after the direct coupling speed is attained, being kept in the engaged state.

The automatic transmission shifts to the predetermined shift speed by changing engagement/disengagement states so as to immediately disengage one of the two clutches that are to be disengaged in order to attain the predetermined shift speed out of the four clutches and so as to gradually disengage the other clutch and gradually engage the one brake that is to be engaged in order to attain the predetermined shift speed.

When jump-shifting from the direct coupling speed (e.g., the seventh speed) to a shift speed (e.g., a second or third speed) that is farther than the predetermined shift speed by disengaging three of the four clutches and engaging the two brakes,

the automatic transmission disengages two of the three clutches to be disengaged and engages one of the brakes to first attain the predetermined shift speed (e.g., the sixth or fifth speed), and then

gradually disengages the clutch other than the two disengaged clutches out of the three clutches to be disengaged and gradually engages the remaining brake that has not been engaged.

The automatic transmission jump-shifts from the direct coupling speed to a shift speed (e.g., the third speed) that is farther than the predetermined shift speed (e.g., the fifth speed) that is attained by the jump shift, by first attaining the predetermined shift speed by the jump shift and then gradually disengaging the clutch other than the two disengaged clutches out of the three clutches and gradually engaging the remaining brake that has not been engaged.

Referring to, e.g., FIGS. 1 to 3 , the shift gear mechanism includes a single-pinion type first planetary gear, a single-pinion type second planetary gear, and a Ravigneaux type planetary gear mechanism as a combination of a double-pinion type planetary gear and a single-pinion type planetary gear.

A first carrier of the first planetary gear and a third carrier of the Ravigneaux type planetary gear mechanism are coupled to an input shaft, a second carrier of the second planetary gear is coupled to an output shaft, and a first sun gear of the first planetary gear and a second sun gear of the second planetary gear are coupled together.

A first clutch is interposed between the first and second sun gears coupled together and a third ring gear of the Ravigneaux type planetary gear mechanism. A second clutch is interposed between the first and second sun gears coupled together and a third sun gear of the double pinion type planetary gear of the Ravigneaux type planetary gear mechanism. A third clutch is interposed between a second ring gear of the second planetary gear and the third ring gear of the Ravigneaux type planetary gear mechanism. A fourth clutch is interposed between a first ring gear of the first planetary gear and the output shaft.

A fourth sun gear of the single-pinion type planetary gear of the Ravigneaux type planetary gear mechanism is coupled to a first brake, and the second ring gear is coupled to a second brake.

Ten forward speeds and one reverse speed are attained by engaging or disengaging the first clutch, the second clutch, the third clutch, the fourth clutch, the first brake, and the second brake as appropriate.

The seventh forward speed as the direct coupling speed is attained by engaging the first clutch, the third clutch, and the fourth clutch and disengaging the first brake and the second brake, and the second clutch is engaged at the seventh speed after shifting to the seventh speed is completed.

Reference numerals in the parentheses are merely for reference to the drawings. These reference numerals are not intended to affect in any way the constitution described in the claims.

According to a preferred embodiment, in a multi-stage automatic transmission with, e.g., ten forward speeds etc., the direct coupling speed can be attained by engaging three of the at least four clutches. After shifting to the direct coupling speed is completed, the remaining clutch in a disengaged state is also engaged at the direct coupling speed so that all of the at least four clutches are engaged. This allows the automatic transmission to prepare for shifting from the direct coupling speed (e.g., the seventh speed) to many shift speeds.

According to a preferred embodiment, a shifting operation from the direct coupling speed to many shift speeds (e.g., the first, fifth, sixth, eighth, ninth, and tenth speeds) including the shift speeds (e.g., the sixth and eighth speeds) adjacent to the direct coupling speed can be performed by disengaging two of the four clutches that are in the engaged state at the direct coupling speed and engaging one of the brakes. Accordingly, no clutch needs to be engaged to perform this shifting operation. This facilitates the shifting operation and can improve shifting flexibility and shifting response.

According to a preferred embodiment, in the case of jump-shifting from the direct coupling speed (e.g., the seventh speed) to the predetermined shift speed (e.g., the fifth or tenth speed), the jump shift can be easily and quickly performed by disengaging two of the clutches and engaging one of the brakes with the remaining clutch kept in the engaged state.

According to a preferred embodiment, the shifting operation to the predetermined shift speed is performed by immediately disengaging one of the two clutches that are to be disengaged in order to attain the predetermined shift speed and performing control to gradually disengage the other clutch and to gradually engage one of the brakes. The shifting operation to the predetermined shift speed can thus be easily and quickly performed by smooth shifting with less shift shock.

According to a preferred embodiment, the shifting operation from the direct coupling speed (e.g., the seventh speed) to the shift speed (e.g., the third or second speed) that is farther than the predetermined shift speed (e.g., the sixth, eighth, or fifth speed) can be easily and quickly performed by shifting from the direct coupling speed to the predetermined shift speed and then performing control to gradually disengage one of the clutches and engaging the remaining brake (e.g., B 2 ).

According to a preferred embodiment, the shifting operation from the direct coupling speed to the shift speed (e.g., the third speed) that is farther than the predetermined shift speed (e.g., the fifth speed) that is attained by the jump shift can be easily and quickly performed by first attaining the predetermined shift speed by the jump shift and then performing control to gradually disengage the remaining one clutch and to gradually engage the other brake with the remaining clutch kept in the engaged state.

According to a preferred embodiment, in the automatic transmission that attains the ten forward speeds, the seventh speed as the direct coupling speed is attained by engaging the first clutch, the third clutch, and the fourth clutch, and after shifting to the seventh speed is completed, the second clutch is engaged at the seventh speed. This allows the automatic transmission to easily jump-shift with high responsiveness from this state to many shift speeds with the second clutch kept engaged.

FIG. 1 is a schematic (skeleton) diagram showing an overall power transmission device.

FIG. 2 is an engagement table of engagement elements of an automatic transmission.

FIG. 3 is a speed diagram of the automatic transmission.

FIG. 4 is a schematic diagram of a control unit and a hydraulic control device.

FIG. 5 is a flowchart showing a main part of a preferred embodiment.

FIG. 6 is a timing chart of control oil pressures, showing a shift to the seventh speed as a direct coupling speed (from the sixth speed to the fifth speed) and a shift from the seventh speed to the fifth speed.

FIG. 7 is a timing chart of the control oil pressures, showing a shift from the seventh speed to the third speed.

FIG. 8 is a timing chart of the control oil pressures, showing a shift from the seventh speed to the tenth speed.

FIG. 9 is a timing chart of the control oil pressures, showing a shift from the seventh speed to the fourth speed.

Various embodiments will be described with reference to the accompanying drawings. First, the general configuration of a power transmission device 10 to which a multi-stage automatic transmission of a preferred embodiment can be applied will be described with reference to FIGS. 1 to 4 . The power transmission device 10 of the present embodiment is connected to a crankshaft of an engine (internal combustion engine), not shown, as a driving source mounted longitudinally in the front part of a rear wheel drive vehicle or to a rotor of an electric motor, and can transmit power (torque) from the engine etc. to right and left rear wheels (driving wheels), not shown. The power transmission device 10 includes a starting device (hydraulic transmission device) 3 , an oil pump 9 , an automatic transmission 4 that shifts the power transmitted from the engine etc. to an input shaft 40 to transmit the shifted power to an output shaft 41 , and a transmission case 5 accommodating these components.

The starting device 3 includes a torque converter 20 , a lockup clutch 21 that can connect and disconnect a front cover coupled to the crankshaft of the engine etc. to and from the input shaft 40 of the automatic transmission 4 , and a damper mechanism 22 that is disposed between the front cover and the input shaft 40 of the automatic transmission 4 to damp vibration. The torque converter 20 includes an input-side pump impeller 23 that is coupled to the front cover, an output-side turbine runner 24 that is coupled to the input shaft 40 of the automatic transmission 4 , a stator 25 that is placed inside the pump impeller 23 and the turbine runner 24 to adjust the flow of hydraulic oil from the turbine runner 24 to the pump impeller 23 , and a one-way clutch 26 that is supported by a stator shaft, not shown, and that restricts the rotation of the stator 25 to only one direction. The torque converter 20 may be a fluid coupling that does not have the stator 25 .

The oil pump 9 is configured as a gear pump having a pump assembly including a pump body and a pump cover, an external gear (inner rotor) coupled to the pump impeller 23 of the torque converter 20 via a chain or a gear train, an internal gear (outer rotor) meshing with the external gear, etc. The oil pump 9 is driven by the power from the engine etc. to suction hydraulic oil (ATF) stored in an oil pan, not shown, to pressure-feed the suctioned hydraulic oil to a hydraulic control device 51 (see FIG. 4 ).

The automatic transmission 4 is configured as a ten-speed transmission, and includes a shift gear mechanism formed by: the input shaft 40 ; the output shaft 41 that is coupled to the right and left rear wheels via a differential gear and a drive shaft, both not shown; a single-pinion type first planetary gear 42 and a single-pinion type second planetary gear 43 which are arranged side by side in the axial direction of the input shaft 40 and the output shaft 41 ; and a Ravigneaux type planetary gear mechanism 44 as a compound planetary gear mechanism formed by combination of a double-pinion type planetary gear 45 and a single-pinion type planetary gear 46 . The automatic transmission 4 further includes a first clutch C 1 , a second clutch C 2 , a third clutch C 3 , a fourth clutch C 4 , a first brake B 1 , and a second brake B 2 as six friction engagement elements in order to change a power transmission path from the input shaft 40 to the output shaft 41 .

In the present embodiment, the first and second planetary gears 42 , 43 and the Ravigneaux type planetary gear mechanism 44 are placed in the transmission case 5 so as to be arranged in order of the Ravigneaux type planetary gear mechanism 44 , the second planetary gear 43 , and the first planetary gear 42 from the starting device 3 side, namely from the engine side (the left side in FIG. 1 ). The Ravigneaux type planetary gear mechanism 44 is thus placed on the front side of the vehicle so as to be located near the starting device 3 . The first planetary gear 42 is placed on the rear side of the vehicle so as to be located near the output shaft 41 . The second planetary gear 43 is placed between the Ravigneaux type planetary gear mechanism 44 and the first planetary gear 42 .

The first planetary gear 42 has a first sun gear 42 s as an external gear, a first ring gear 42 r as an internal gear placed concentrically with the first sun gear 42 s , a plurality of first pinion gears 42 p each meshing with the first sun gear 42 s and the first ring gear 42 r , and a first carrier 42 c holding the plurality of first pinion gears 42 p such that the first pinion gears 42 p can rotate (turn). In the present embodiment, the gear ratio λ1 of the first planetary gear 42 (the number of teeth of the first sun gear 42 s /the number of teeth of the first ring gear 42 r ) is set to, e.g., λ1=0.277.

The first carrier 42 c of the first planetary gear 42 is constantly coupled (fixed) to the input shaft 40 . Accordingly, when the power is being transmitted from the engine etc. to the input shaft 40 , the power from the engine etc. is constantly transmitted to the first carrier 42 c via the input shaft 40 . The first carrier 42 c functions as an input element of the first planetary gear 42 . The first ring gear 42 r functions as an output element of the first planetary gear 42 when the fourth clutch C 4 is in an engaged state.

The second planetary gear 43 has a second sun gear 43 s as an external gear, a second ring gear 43 r as an internal gear placed concentrically with the second sun gear 43 s , a plurality of second pinion gears 43 p each meshing with the second sun gear 43 s and the second ring gear 43 r , and a second carrier 43 c holding the plurality of second pinion gears 43 p such that the second pinion gears 43 p can rotate (turn). In the present embodiment, the gear ratio λ2 of the second planetary gear 43 (the number of teeth of the second sun gear 43 s /the number of teeth of the second ring gear 43 r ) is set to, e.g., λ2=0.244.

The second sun gear 43 s of the second planetary gear 43 is integral with (constantly coupled to) the first sun gear 42 s of the first planetary gear 42 and always rotates or stops together with (and coaxially with) the first sun gear 42 s . However, the first sun gear 42 s and the second sun gear 43 s may be formed as separate members and may be constantly coupled together via a coupling member, not shown. The second carrier 43 c of the second planetary gear 43 is constantly coupled to the output shaft 41 and always rotates or stops together with (and coaxially with) the output shaft 41 . The second carrier 43 c thus functions as an output element of the second planetary gear 43 . Moreover, the second ring gear 43 r of the second planetary gear 43 can be held stationary by the second brake B 2 and functions as a fixable element of the second planetary gear 43 .

The Ravigneaux type planetary gear mechanism 44 is a compound planetary gear mechanism formed by combination of the third planetary gear 45 as a double-pinion type planetary gear and the fourth planetary gear 46 as a single-pinion type planetary gear. The planetary gears are placed in the transmission case 5 so as to be arranged in order of the fourth planetary gear 46 , the third planetary gear 45 , the second planetary gear 43 , and the first planetary gear 42 from the engine side.

The Ravigneaux type planetary gear mechanism 44 includes a third sun gear 45 s and a fourth sun gear 46 s as external gears, a third ring gear 45 r as an internal gear placed concentrically with the third and fourth sun gears 45 s , 46 s , a plurality of third pinion gears (short pinion gears) 45 p meshing with the third sun gear 45 s , a plurality of fourth pinion gears (long pinion gears) 46 p meshing with the fourth sun gear 46 s and the plurality of third pinion gears 45 p and meshing with the third ring gear 45 r , and a third carrier 45 c holding the plurality of third pinion gears 45 p and the plurality of fourth pinion gears 46 p such that the plurality of third pinion gears 45 p and the plurality of fourth pinion gears 46 p can rotate (turn).

The third planetary gear 45 is formed by the third sun gear 45 s , the third carrier 45 c , the third pinion gears 45 p , the fourth pinion gears 46 p , and the third ring gear 45 r . The fourth planetary gear 46 is formed by the fourth sun gear 46 s , the third carrier 45 c , the fourth pinion gears 46 p , and the third ring gear 45 r . In the present embodiment, the Ravigneaux type planetary gear mechanism 44 is configured such that the gear ratio λ3 of the third planetary gear 45 (the number of teeth of the third sun gear 45 s /the number of teeth of the third ring gear 45 r ) is, e.g., λ3=0.488 and the gear ratio λ4 of the fourth planetary gear 46 (the number of teeth of the fourth sun gear 46 s /the number of teeth of the third ring gear 45 r ) is, e.g., λ4=0.581.

Of the rotary elements of the Ravigneaux type planetary gear mechanism 44 , the fourth sun gear 46 s can be held stationary by the first brake B 1 and functions as a fixable element of the Ravigneaux type planetary gear mechanism 44 . Moreover, the third carrier 45 c is constantly coupled (fixed) to the input shaft 40 and is constantly coupled to the first carrier 42 c of the first planetary gear 42 . Accordingly, when the power is being transmitted from the engine etc. to the input shaft 40 , the power from the engine etc. is constantly transmitted to the third carrier 45 c via the input shaft 40 . The third carrier 45 c thus functions as an input element of the Ravigneaux type planetary gear mechanism 44 . The third ring gear 45 r can be coupled to the sun gear 43 s of the second planetary gear 43 and the sun gear 42 s of the first planetary gear 42 via the first clutch C 2 and an intermediate shaft 47 and can be coupled to the ring gear 43 r of the second planetary gear 43 via the third clutch C 3 . The third ring gear 45 r functions as a first output element of the Ravigneaux type planetary gear mechanism 44 . The third sun gear 45 s can be coupled to the sun gear 43 s of the second planetary gear 43 and the sun gear 42 s of the first planetary gear 42 via the second clutch C 2 and the intermediate shaft 47 . The third sun gear 45 s functions as a second output element of the Ravigneaux type planetary gear mechanism 44 .

The first clutch C 1 connects and disconnects the first sun gear 42 s of the first planetary gear 42 and the second sun gear 43 s of the second planetary gear 43 , which are constantly coupled together, to and from the third ring gear 45 r of the Ravigneaux type planetary gear mechanism 44 . The second clutch C 2 connects and disconnects the first sun gear 42 s of the first planetary gear 42 and the second sun gear 43 s of the second planetary gear 43 , which are constantly coupled together, to and from the third sun gear 45 s of the Ravigneaux type planetary gear mechanism 44 . The third clutch C 3 connects and disconnects the second ring gear 43 r of the second planetary gear 43 to and from the third ring gear 45 r of the Ravigneaux type planetary gear mechanism 44 . The fourth clutch C 4 connects and disconnects the first ring gear 42 r of the first planetary gear 42 to and from the output shaft 41 .

The first brake B 1 holds (connects) the fourth sun gear 46 s of the Ravigneaux type planetary gear mechanism 44 stationary to the transmission case 5 such that the fourth sun gear 46 s cannot rotate, and disconnects the fourth sun gear 46 s from the transmission case such that the fourth sun gear 46 s can rotate. The second brake B 2 holds (connects) the second ring gear 43 r of the second planetary gear 43 stationary to the transmission case 5 such that the second ring gear 43 r cannot rotate, and disconnects the second ring gear 43 r from the transmission such that the second ring gear 43 r can rotate.

In the present embodiment, multi-plate friction hydraulic clutches that have a hydraulic servo formed by a piston, a plurality of friction engagement plates (e.g., friction plates as annular members having a friction material boned to both surfaces thereof and separator plates as annular members both surfaces of which are smooth), an engagement oil chamber and a centrifugal oil pressure cancel chamber to each of which hydraulic oil is supplied, etc. are used as the first to fourth clutches C 1 to C 4 . Multi-plate friction hydraulic brakes that have a hydraulic servo formed by a piston, a plurality of friction engagement plates (friction plates and separator plates), an engagement oil chamber to which hydraulic oil is supplied, etc. are used as the first and second brakes B 1 , B 2 .

FIG. 2 is an engagement table showing the relationship between each shift speed of the automatic transmission 4 and the operating state of the first to fourth clutches C 1 to C 4 and the first and second brakes B 1 , B 2 . FIG. 3 is a speed diagram showing the ratio of the rotational speed of each rotary element to the rotational speed of the input shaft 40 in the automatic transmission 4 (the rotational speed of the input shaft 40 , i.e., the first carrier 42 c and the third carrier 45 c , is the value of 1).

As shown in FIG. 3 , the three rotary elements of the single-pinion type first planetary gear 42 , namely the first sun gear 42 s , the first ring gear 42 r , and the first carrier 42 c , are arranged in order of the first sun gear 42 s , the first carrier 42 c , and the first ring gear 42 r from the left in the figure at intervals corresponding to the gear ratio λ1 on the speed diagram of the first planetary gear 42 (the left speed diagram in FIG. 3 ). In the present embodiment, according to the order in which the rotary elements are arranged on the speed diagram, the first sun gear 42 s is a first rotary element of the automatic transmission 4 , the first carrier 42 c is a second rotary element of the automatic transmission 4 , and the first ring gear 42 r is a third rotary element of the automatic transmission 4 . Accordingly, the first planetary gear 42 has the first rotary element, the second rotary element, and the third rotary element of the automatic transmission 4 which are sequentially arranged at the intervals corresponding to the gear ratio λ 1 on the speed diagram.

The three rotary elements of the single-pinion type second planetary gear 43 , namely the second sun gear 43 s , the second ring gear 43 r , and the second carrier 43 c , are arranged in order of the second sun gear 43 s , the second carrier 43 c , and the second ring gear 43 r from the left in the figure at intervals corresponding to the gear ratio λ2 on the speed diagram of the second planetary gear 43 (the middle speed diagram in FIG. 3 ). In the present embodiment, according to the order in which the rotary elements are arranged on the speed diagram, the second sun gear 43 s is a fourth rotary element of the automatic transmission 4 , the second carrier 43 c is a fifth rotary element of the automatic transmission 4 , and the second ring gear 43 r is a sixth rotary element of the automatic transmission 4 . Accordingly, the second planetary gear 43 has the fourth rotary element, the fifth rotary element, and the sixth rotary element of the automatic transmission 4 which are sequentially arranged at the intervals corresponding to the gear ratio 2 on the speed diagram.

Moreover, the four rotary elements of the Ravigneaux type planetary gear mechanism 44 , namely the fourth sun gear 46 s , the third carrier 45 c , the third ring gear 45 r , and the third sun gear 45 s , are arranged in this order from the left in the figure at intervals corresponding to the gear ratio λ3 of the single-pinion type fourth planetary gear 46 and the gear ratio 4 of the double-pinion type third planetary gear 45 on the speed diagram of the Ravigneaux type planetary gear mechanism 44 (the right speed diagram in FIG. 3 ). In the present embodiment, according to the order in which the rotary elements are arranged on the speed diagram, the fourth sun gear 46 s is a seventh rotary element of the automatic transmission 4 , the third carrier 45 c is an eighth rotary element of the automatic transmission 4 , the third ring gear 45 r is a ninth rotary element of the automatic transmission 4 , and the third sun gear 45 s is a tenth rotary element of the automatic transmission 4 . Accordingly, the Ravigneaux type planetary gear mechanism 44 has the seventh rotary element, the eighth rotary element, the ninth rotary element, and the tenth rotary element of the automatic transmission 4 which are sequentially arranged at the intervals corresponding to the gear ratios λ3, λ4 on the speed diagram.

As shown in FIG. 4 , a control device U of the automatic transmission includes: a (electronic) control unit (ECU) 50 that receives signals such as a range operation signal from the driver and signals of a vehicle speed and an accelerator operation amount as a torque request from the driver and outputs a control signal; and the hydraulic control device 51 having valves such as a multiplicity of linear solenoid valves. The control unit 50 determines a shift speed based on the signals and outputs signals of control oil pressures PC 1 , PC 2 , PC 3 , PC 4 , PB 1 , PB 2 to the linear solenoid valves of the hydraulic control device 51 . The hydraulic control device 51 outputs oil pressures regulated by the control oil pressure signals to hydraulic servos C 1 , C 2 , C 3 , C 4 , B 1 , B 2 of the clutches and the brakes of the automatic transmission 4 .

In the automatic transmission 4 thus configured, the first to fourth clutches C 1 to C 4 and the first and second brakes B 1 , B 2 shown in the skeleton diagram of FIG. 1 are engaged or disengaged according to the combinations shown in the engagement table of FIG. 2 to attain first to tenth forward speeds (1st to 10th) and a reverse speed (Rev) at the rotational speed ratios shown in the speed diagram of FIG. 3 .

The seventh forward speed is basically attained by engaging the first clutch C 1 , the third clutch C 3 , and the fourth clutch C 4 and disengaging the remaining second clutch C 2 , the first brake B 1 , and the second brake B 2 . That is, when attaining the seventh forward speed, the first sun gear 42 s of the first planetary gear 42 and the second sun gear 43 s of the second planetary gear 43 are connected to the third ring gear 45 r of the Ravigneaux type planetary gear mechanism 44 by the first clutch C 1 , the second ring gear 43 r of the second planetary gear 43 is connected to the third ring gear 45 r of the Ravigneaux type planetary gear mechanism 44 by the third clutch C 3 , and the first ring gear 42 r of the first planetary gear 42 is connected to the output shaft 41 and the second carrier 43 c of the second planetary gear 43 by the fourth clutch C 4 . In the present embodiment, the gear ratio γ7 at the seventh forward speed is γ7=1.000.

An embodiment of the control device of the automatic transmission which is a main part of a preferred embodiment will be described below. As shown in FIG. 5 , a shifting operation to the seventh forward speed as a direct coupling speed is performed (S 2 ), and shifting to the seventh forward speed is completed (S 3 ). For example, as shown in FIG. 6 , in the case of an upshift from the sixth forward speed to the seventh forward speed, the control unit determines that a shifting operation from the sixth speed to the seventh speed is to be performed. According to this determination of the control unit, from the state at the sixth speed where the control oil pressures PC 1 , PC 4 , PB 1 are being supplied, the control unit performs control to release the control oil pressure PB 1 and to supply the control oil pressure PC 3 . In FIG. 6 , PL represents a line oil pressure, and TH represents a throttle opening (accelerator operation amount). By this control of the control unit, from the sixth speed where the first clutch C 1 , the fourth clutch C 4 , and the first brake B 1 are in an engaged state, the first brake B 1 is disengaged and the third clutch C 3 is engaged. Shifting to the seventh speed as a direct coupling speed is thus completed, and the direct coupling speed is attained.

After the shifting operation to the seventh speed is completed, the remaining (other) one clutch other than the three engaged clutches of the four clutches is engaged at the seventh speed (S 4 ). Specifically, as shown in FIG. 6 , with the control oil pressures PC 1 , PC 3 , PC 4 being supplied, the control unit outputs a signal to supply the remaining (other) control oil pressure PC 2 . The second clutch C 2 is thus engaged in addition to the first, third, and fourth clutches C 1 , C 3 , C 4 . Since the seventh speed is a direct coupling speed, engagement of the second clutch C 2 does not affect the direct coupling speed itself in any way. The second clutch C 2 (the remaining one clutch) may be engaged at any time at the seventh speed. That is, the second clutch C 2 may be engaged immediately after shifting to the seventh speed is completed (i.e., when the gear ratio calculated from the rotational speeds of the input shaft and the output shaft becomes equal to 1.000) or may be engaged after the vehicle starts traveling steadily at the seventh speed (e.g., when a predetermined time or more has elapsed after the gear ratio becomes equal to 1.000).

If the control unit determines that a shifting operation to a shift speed (other gear speed) other than the seventh speed is to be performed (S 5 ), the control unit releases the clutches, out of the four clutches, which are not required for the target shift speed (S 6 ) and performs shifting to the target shift speed (S 7 ). For example, as shown in FIG. 6 , if the driver depresses an accelerator pedal to request a downshift and the control unit determines that a jump shift from the seventh speed to the fifth speed is to be performed, the control unit immediately outputs a signal to release the control oil pressure PC 1 for the first clutch C 1 that is not required for the fifth speed. The control unit also performs control to gradually release the control oil pressure PC 3 for the third clutch C 3 and to gradually supply the control oil pressure PB 1 for the brake B 1 that is required for the fifth speed. Shifting to the fifth speed is thus completed by merely disengaging the third clutch C 3 and engaging the first brake B 1 with the second clutch C 2 , namely the clutch additionally engaged after completion of the shifting to the seventh speed, being kept in the engaged state. Conventionally, the operation of disengaging the first and third clutches C 1 , C 3 and the operation of engaging the second clutch C 2 need to be performed at the same time in order to shift from the seventh speed to the fifth speed. In the present embodiment, however, the engagement/disengagement states need only to be changed such that the first clutch C 1 is immediately disengaged, and the third clutch C 3 is controlled to be gradually disengaged and the first brake B 1 is controlled to be gradually engaged. Improvement in shifting flexibility and shifting response can therefore be expected.

FIG. 7 is a diagram showing a shift from the seventh speed as a direct coupling speed to the third speed. At the seventh speed, the first, third, and fourth clutches C 1 , C 3 , C 4 are in an engaged state and the second clutch C 2 is also in an engaged state, as described above. If the control unit determines that a shifting operation from the seventh speed to the third speed is to be performed, the control unit immediately outputs a signal to release the control oil pressure PC 1 and the control oil pressure PC 3 . The control unit also performs control to supply the control oil pressure PB 1 and to release the control oil pressure PC 4 . As a result, the first clutch C 1 and the third clutch C 3 are disengaged. Moreover, the fourth clutch C 4 that is being controlled to be disengaged is still in the engaged state, and the first brake B 1 is being controlled to be engaged. Accordingly, the fifth speed at which the second clutch C 2 , the fourth clutch C 4 , and the first brake B 1 are engaged is temporarily attained.

The control oil pressure PC 4 is gradually released and the control oil pressure PB 2 is controlled to be gradually supplied. The second clutch C 2 is thus kept in the engaged state, and the fourth clutch C 4 is disengaged and the second brake B 2 is engaged, whereby shifting to the third speed is completed. Accordingly, in the case of the shift from the seventh speed to the third speed, the fifth speed is temporarily attained, and the shifting thus proceeds smoothly. Moreover, the engagement/disengagement states of the two elements are changed with the second clutch C 2 kept in the engaged state. Namely, the fourth clutch C 4 is disengaged and the second brake B 2 is engaged with the second clutch C 2 kept in the engaged state. The jump shift can thus be achieved easily and smoothly.

FIG. 8 is a diagram showing a jump shift from the seventh speed as a direct coupling speed to the tenth speed. At the seventh speed, the second clutch C 2 in addition to the first, third, and fourth clutches C 1 , C 3 , C 4 are in an engaged state, as described above. If the control unit determines that a jump shift from the seventh speed to the tenth speed is to be performed, the control unit immediately outputs a signal to release the control oil pressure PC 4 . The control unit also performs control to gradually release the control oil pressure PC 1 and to gradually increase the control oil pressure PB 1 . Accordingly, the first clutch C 1 is disengaged and the first brake B 1 is engaged with the second and third clutches C 2 , C 3 kept in the engaged state. The jump shift from the seventh speed to the tenth speed is thus completed easily and smoothly.

FIG. 9 is a diagram showing a jump shift from the seventh speed as a direct coupling speed to the fourth speed. At the seventh speed, the first, second, third, and fourth clutches C 1 , C 2 C 3 , C 4 are in an engaged state, as described above. If the control unit determines that a jump shift from the seventh speed to the fourth speed is to be performed, the control unit immediately outputs a signal to release the control oil pressures PC 2 , PC 3 . The control unit also performs control to gradually release the control oil pressure PC 1 , supplies the control oil pressure PB 1 , and performs control to gradually supply the control oil pressure PB 2 . Shifting to the fourth speed at which the fourth clutch C 4 , the first brake B 1 , and the second brake B 2 are engaged is thus completed. The second clutch C 2 is disengaged in the case of the jump shift from the seventh speed to the fourth speed, a shift from the seventh speed to its adjacent speed, namely to the sixth speed and the eighth speed, and a shift from the seventh speed to the ninth speed and the second speed. Accordingly, for these shifting operations, it is of no use to engage the second clutch C 2 at the seventh speed as a direct coupling speed. However, the operation of disengaging the second clutch C 2 can be performed quickly and does not hinder the shifting operations. That is, when the seventh speed as a direct coupling speed is attained, the second clutch C 2 is engaged regardless of the next shift speed to be attained, in order to prepare for shifting to the next predetermined shift speed. In the case where a shift signal from the direct coupling speed (the seventh speed) to its adjacent shift speed (the sixth speed or the eighth speed) is being output or it is predicted that such a shift signal is likely to be output, the control to engage the second clutch C 2 may be omitted. Since the first clutch C 1 and the second clutch C 2 are in an engaged state at the seventh speed, a jump shift from the seventh speed to the first speed can be quickly performed by immediately disengaging the third clutch C 3 and the fourth clutch C 4 and performing control to engage the second brake B 2 .

The present embodiment is applied to the ten-forward speed automatic transmission shown in FIGS. 1 to 4 . However, the present invention is not limited to this. The present invention is also applicable to ten-speed transmissions having other shift gear mechanisms and is applicable to automatic transmissions other than ten-speed automatic transmissions, namely automatic transmissions with less than ten shift speeds or more than ten shift speeds.

4 Automatic Transmission

40 Input Shaft

41 Output Shaft

42 First Planetary Gear

42 s First Sun Gear

42 c First Carrier

42 r First Ring Gear

43 Second Planetary Gear

43 s Second Sun Gear

43 c Second Carrier

43 r Second Ring Gear

44 Ravigneaux Planetary Gear Mechanism

45 Double-Pinion Type Planetary Gear

45 s Third Sun Gear

45 c Third Carrier

45 r Third Ring Gear

46 Single-Pinion Type Planetary Gear

46 s Fourth Sun Gear

C 1 First Clutch

C 2 Second Clutch (Remaining Clutch)

C 3 Third Clutch

C 4 Fourth Clutch

B 1 First Brake

B 2 Second Brake

U Control Device