Angular speed detecting device using dual angular position signals to reduce noise

The present application is based on and claims priority from Japanese Patent Application 2004-135252, filed Apr. 30, 2004, the contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to an angular speed detecting device that detects the rotation speed of a rotating object.

2. Description of the Related Art

A magnetic sensor unit that is composed of a pair of magnetic sensing elements and a magnetic field setting member is well-known for a device to detect the rotation angle of a rotating object, as disclosed in JP-A-2002-340511. In such a device, a pair of sensor elements provides signals Va and Vb, as shown in FIG. 16 . Then, a saw-tooth-wave curve of trigonometric values θ′ that correspond to the arctangent of the signals Va and Vb, is provided as shown in FIG. 17 . Then, plural rotation angle ranges of the rotating object between 0 degree and 360 degrees can be known from combinations of the positive and negative signs of the output signals Va and Vb, as shown in FIG. 20 . Therefore, the rotation angle of the rotating object in terms of 360 degrees can be known from the output angle θ, as shown in FIG. 18 , so that the angular speed of the rotating object can be obtained by differentiating the output angle θ in theory. However, when one intends to obtain the angular speed of the rotating object from the rotation angle around 360 degrees from the output angle θ, he will have a difficulty because the output angle θ before or after 360 degrees changes too sharply to differentiate it, as shown in FIG. 19 .

Therefore, it is an object of the invention to provide an improved angular speed detecting device that can accurately detect angular speed irrespective of the angular position.

According to a preferred feature of the invention, an angular speed detecting device for detecting an angular speed of a rotating object includes a magnetic field setting means, sinusoidal signal generating means for generating a pair of first sinusoidal signal Va and a second sinusoidal signal Vb and an angular speed calculating means. The angular speed calculating means calculates the angular speed by a processing program that is composed of the following steps: forming a pair of trigonometric functions of a trigonometric value θ′ from the sinusoidal signals Va and Vb; forming a table showing plus or minus sign of the pair of the sinusoidal signals Va, Vb and the trigonometric values θ′ at a plurality of rotation angles of the rotating object; distinguishing rotation position of the rotating object from combinations of the plus or minus sign of the first and second sinusoidal signals Va, Vb and the trigonometric values θ′; forming a pair of saw-tooth curves of output angles θ 1 , θ 2 in terms of 360-degree angular range that are different in phase to each other by adding offset values to the trigonometric values θ′ according to the rotation position that is distinguished above; and selectively using curves of the output angles θ 1 and θ 2 to calculate the angular speed of a rotating object.

In the angular speed detecting device as described above, one of the pair of trigonometric functions is formed from a sum of the sinusoidal signals Va and Vb; and the other of the pair of trigonometric functions is formed from a difference between the sinusoidal signals Va and Vb. Further, the plus or minus sign of the voltage signals Va and Vbs neglected where the sign changes one from the other when distinguishing rotation position of the rotating object from combinations of the plus or minus sign of the first and second sinusoidal signals Va, Vb and the trigonometric values θ′. The second means may be composed of a pair of Hall elements. In this case, the Hall elements are preferably disposed in the magnetic field inclined with respect to each other at an angle of 90 degrees. The second means may be composed of a pair of magnetic resistance (reluctance) elements instead of the Hall elements.

Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings:

FIG. 1 is a schematic diagram illustrating an angular speed detecting device according to the first embodiment of the invention;

FIG. 2 is a graph showing a relationship between the rotation angle of a rotating object and the output angle of the angular speed detecting device according to the first embodiment of the invention;

FIG. 3 is a graph showing a relationship between the rotation angle of a rotating object and the angular speed thereof;

FIG. 4 is a table of the angular speed detecting device according to the first embodiment of the invention to show a relationship between rotation angle ranges, positive and negative signs of output signals of a magnetic sensor unit, trigonometric values and output angles;

FIG. 5 is another table of the angular speed detecting device according to the first embodiment of the invention to show a relationship between rotation angle ranges, positive and negative signs of output signals of a magnetic sensor unit, trigonometric values and output angles;

FIG. 6 is a graph showing a relationship between the rotation angle of a rotating object and the output voltage of a magnetic sensor unit of an angular speed detecting device according to the second embodiment of the invention;

FIG. 7 is a table of the angular speed detecting device according to the second embodiment of the invention to show a relationship between the rotation angle range and combinations of the plus or minus sign of the sum and difference of output signals of a magnetic sensor unit, trigonometric values and output angles;

FIG. 8 is another table of the angular speed detecting device according to the second embodiment of the invention to show a relationship between the rotation angle range and combinations of the plus or minus sign of the sum and difference of output signals of a magnetic sensor unit, trigonometric values and output angles;

FIG. 9 is a schematic diagram illustrating an angular speed detecting device according to the third embodiment of the invention;

FIG. 10 is a graph showing a relationship between the rotation angle of a rotating object and the output voltages of a magnetic sensor unit of an angular speed detecting device according to the third embodiment of the invention;

FIG. 11 is a graph showing a relationship between the rotation angle of a rotating object and trigonometric values of the angular speed detecting device according to the third embodiment of the invention;

FIG. 12 is a graph showing a relationship between the rotation angle of a rotating object and output angles of the angular speed detecting device according to the third embodiment of the invention;

FIG. 13 is a table of the angular speed detecting device according to the third embodiment of the invention to show a relationship between the rotation angle ranges, combinations of the plus or minus sign of the sum and difference of output signals of a magnetic sensor unit, trigonometric values and output angles;

FIG. 14 is a table of the angular speed detecting device according to the third embodiment of the invention to show a relationship between the rotation angle ranges, combinations of the plus or minus sign of the sum and difference of different output signals of a magnetic sensor unit another trigonometric values and output angles;

FIG. 15 is a table of the angular speed detecting device according to the fourth embodiment of the invention to show a relationship between rotation angle ranges, combinations of positive and negative signs of output signals of the magnetic sensor unit, trigonometric values and output angles;

FIG. 16 is a graph showing a relationship between the rotation angle of a rotating object and the output voltages of a magnetic sensor unit of a prior art angular speed detecting device;

FIG. 17 is a graph showing a relationship between the rotation angle of a rotating object and trigonometric values of the angular speed detecting device of the prior art angular speed detecting device;

FIG. 18 is a graph showing a relationship between the rotation angle of a rotating object and output angles of the prior art angular speed detecting device;

FIG. 19 is a graph showing a relationship between the rotation angle of a rotating object and the angular speed provided by the prior art angular speed detecting device; and

FIG. 20 is a table showing a relationship between rotation angle ranges and combinations of positive and negative signs of output signals of a magnetic sensor unit of the prior art angular speed detecting device.

The present invention will be described with reference to some preferred embodiments that are shown in the appended drawings.

An angular speed detecting device 10 according to the first embodiment of the invention to be used for detecting the angular speed of a rotating object 1 , such as a crankshaft or a vehicle wheel, will be described with references to FIGS. 1-5 , 16 and 17 . The angular speed detecting device 10 includes a pair of permanent magnets 12 and 114 , a pair of Hall elements 20 and 22 and an electronic control unit (hereinafter referred to as the ECU) 30 .

The permanent magnets 12 , 14 provide a generally even magnetic field or a constant magnetic flux density in the space between them. The pair of Hall elements 20 , 22 have the same construction and are disposed in the space between the permanent magnets 12 , 14 inclined with respect to each other at an angle a (e.g. 90 degrees) and to the magnetic field at half the angle α. Therefore, when the rotating object 1 rotates and the Hall elements are electrically powered, the Hall element 20 generates a sinusoidal voltage signal Va and the Hall element 22 generates a sinusoidal voltage signal Vb, as shown in FIG. 16 . The two sinusoidal voltage signals Va, Vb are different in phase from each other by 90 degrees and are defined by the following expressions.

Va=kBI· sin θ′  (1)

Vb=kBI· sin (θ′+90°)= kBI· cos θ′  (2)

The ECU 30 has a memory that stores a processing program for obtaining the angular speed of the rotation object 1 . The ECU 30 calculates tan θ′ by the following expression (3) and an angle θ′ (hereinafter referred to as trigonometric value or base angle), which is described with reference to FIG. 17 , by the following expression (4).

tan θ′=sin θ′/cos θ′= Va/Vb   (3)

θ′= arc tan ( Va/Vb )   (4)

The ECU 30 distinguishes an angular position of the rotating object 1 in terms of 360-degree angular range by a combination of the plus and minus sign of the voltage signals Va, Vb and the trigonometric values θ′. The ECU 30 provides a pair of saw-tooth-wave curves of output angles θ 1 and θ 2 by adding offset angles 180 degrees or 360 degrees to the trigonometric value θ′, as shown in FIGS. 2 , 4 and 5 , in which character N indicates that the plus or minus sign is neglected to distinguish the angular position.

The offset angle for the curve of output angles θ 1 shown in FIG. 4 does not change at rotation angle 180° but changes at rotation angles 0° (360°), 90° and 270° where plus or minus sign of the trigonometric value θ′ changes to one from the other. That is, the offset angle changes from 360° to 0° at rotation angle 0°, from 0° to 180° at rotation angle 90° and from 180 to 360° at rotation angle 270°.

On the other hand, the offset angle for the curve of output angles θ 2 shown in FIG. 5 does not change at rotation angle 0° (360°) but changes at rotation angles 90°, 180° and 270° where the plus or minus sign of the trigonometric value θ′ changes to one from the other. That is, the offset angles change from 360° to 0° at rotation angle 180°, change from 180° to 360° at rotation angle 90° and change from 0 to 180° at rotation angle 270°.

Incidentally, although the trigonometric value θ′ at the rotation angle 90° and 270° can not be calculated because of Va/Vb with Vb=0 according to the expression (4), it can be set to 90° in order to provide the corresponding output angles, 90° and 270°.

Thus, the angular speed of a rotating object in terms of 360-degree angular range can be detected accurately or without noises, as shown in FIG. 3 , if the curves of the output angles θ 1 and θ 2 are selectively used with the plus or minus sign of the voltage signals Va and Vb before and after the rotation angles 0°(360°) and 180° being neglected. That is, when the rotation angle of a rotating object is about 180°, the angular speed is calculated from the curve of the output angle θ 1 . On the other hand, the angular speed is calculated from the curve of the output angle θ 2 when the rotation angle of a rotating object is about 360°.

If the pair of Hall elements 20 , 22 , is disposed in the space between the permanent magnets 12 , 14 inclined with respect to each other at an angle α that is other than 90 degrees, the Hall element 20 generates a sinusoidal voltage signal Va and the Hall element 22 generates a sinusoidal voltage signal Vb, the two sinusoidal voltage signals Va, Vb are different in phase from each other by α and are defined by the following expressions.

tan θ′=cot α·( Va−Vb )/( Va+Vb )   (5)

θ′= arc tan{cotα·( Va−Vb )/( Va+Vb )}  (6)

Therefore, the angular speed can be accurately detected in the same manner as described above.

An angular speed detecting device 10 according to the second embodiment of the invention will be described with reference to FIGS. 6-8 . The angular speed detecting device 10 is substantially the same in construction except for the processing program for obtaining the angular speed of the rotation object 1 , which is installed into the ECU 30 .

The ECU 30 provides a pair of saw-tooth-wave curves of output angles θ 1 and θ 2 by adding offset angles to the trigonometric value θ′, as shown in FIGS. 7 and 8 , in which character N indicates that the plus or minus sign is neglected to distinguish the angular position. In this case, plus and minus sign of the sum (i.e. Va+Vb) and difference (i.e. Va−Vb) of the voltage signals Va and Vb are used to distinguish the angular position of the rotating object instead of the plus and minus sign of each of the voltage signals Va, Vb. The sum and the difference can be expressed as follows:

Va+Vb=kBI ·sin θ+ kBI ·cos θ=√{square root over ( 2 )} kBI ·sin (θ+45)   (7)

Va−Vb=kBI ·sin θ− kBI ·cos θ=√{square root over ( 2 )} kBI ·sin (θ−45)   (8)

Then, the output angles θ 1 and θ 2 can be determined by combining the plus or minus sign of the Va+Vb, Va−Vb and the trigonometric value θ′, as shown in FIGS. 7 and 8 .

Thus, the angular speed of a rotating object in terms of 360-degree angular range can be detected by selectively using curves of the output angles θ 1 and θ 2 while neglecting the plus or minus sign of the voltage signals in the same manner as the first embodiment.

An angular speed detecting device 40 according to the third embodiment of the invention will be described with reference to FIG. 9 .

The angular speed detecting device 40 includes a pair of permanent magnets 12 and 14 , three Hall elements 20 , 22 and 24 and the ECU 30 .

The Hall elements 20 , 22 , 24 have the same construction and are disposed in the space between the permanent magnets 12 , 14 inclined with respect to each other at an angle of 90 degrees. Therefore, when the rotating object 1 rotates and the Hall elements are electrically powered, the Hall elements 20 , 22 and 24 generates sinusoidal voltage signals that are 90 degrees in angle different from another. In other words, the Hall element 20 generates a sinusoidal voltage signal Va, the Hall element 22 generates a sinusoidal voltage Vb, and the Hall element 24 generates a sinusoidal voltage signal Vc, as shown in FIG. 10 .

The ECU 30 calculates, using the expression (5) and (6), a trigonometric value θ 0 ′ from the voltage signals Va and Vb and a trigonometric value θ 1 ′ from the voltage signals Va and Vc, forming a pair of saw-tooth curves as shown in FIG. 11 .

The ECU 30 distinguishes angular positions of the rotating object 1 in terms of 360-degree angular range by combinations of the plus and minus sign of the voltage signals (Va+Vb), (Va−Vb) and the trigonometric values θ 0 ′, θ 1 ′ as shown in FIGS. 13 and 14 , thereby to provide a pair of saw-tooth-wave curves of output angles θ 0 and θ 1 by adding offset angles to the trigonometric values θ 0 ′, θ 1 ′, as shown in FIG. 12 .

Thus, the angular speed of a rotating object in terms of 360-degree angular range can be obtained by selectively using curves of the output angles θ 0 ′ and θ 1 ′ while neglecting the plus or minus sign of the voltage signals Va and Vb before and after the rotation angles 90° and 270′.

If the Hall elements are disposed included with respect to each other at an angle α that is other than 90 degrees, the two sinusoidal voltage signals Va, Vb are different in phase from each other by α and are defined by the expressions (5) and (6). Therefore, the angular speed can be accurately detected in the same manner as described.

An angular speed detecting device according to the fourth embodiment of the invention will be described with reference to FIGS. 1 , 15 and 16 .

The angular speed detecting device includes a pair of Hall elements 20 and 22 as shown in FIG. 1 .

The ECU 30 calculates, using a processing program and the expressions (3) and (4), trigonometric value θ 0 ′ shown in FIG. 11 from the voltage signals Va and Vc, shown in FIG. 16 .

The ECU 30 distinguishes an angular position of the rotating object 1 in terms of 360-degree angular range by a combination of the plus and minus sign of the voltage signals Va, Vb and the trigonometric values θ 0 ′. The ECU 30 provides a saw-tooth-wave curve of another trigonometric value θ 1 ′ by adding an offset angle of 90 degrees to the trigonometric value θ 0 ′, which are used as the output angles. Thus, the angular speed of a rotating object in terms of 360-degree angular range can be detected by selectively using the curves of the trigonometric values θ 0 ′ and θ 1 ′ in substantially the same manner as the above embodiments.

The Hall elements used in the above embodiments can be replaced by magnetic resistance (reluctance) elements.

The trigonometric values θ 0 ′, θ 1 ′ of the angular speed detecting device according to the third embodiment can be used as the output angles in the same manner as the fourth embodiment.

In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense.