Rotary encoder and method of manufacturing the same

The present invention relates to a rotary encoder used for operation of an electronic device, and to a method of manufacturing the encoder.

Rotary encoders have been recently used for input sections, such as menu selectors and volume controllers of various electronic devices, such as car audio systems. The rotary encoders have been required to have small sizes and to control the devices precisely.

FIGS. 10 and 11 are a cross-sectional view and an exploded perspective view of conventional rotary encoder 501 disclosed in JP11-135310, respectively. Operation shaft 6 is made of molding resin and has center columnar section 6 A having a circular column shape and annular flange 6 B protruding from the outer circumference of center columnar section 6 A. The upper part of center columnar section 6 A has cutout 6 C therein adapted for engagement in an operation dial. An upper surface of annular flange 6 B has click grooves 6 D extending radially. A caulking protrusion being crushed, slidable brush 8 is fixed to a lower surface of annular flange 6 B.

Shaft supporter 9 is made of resin and has protruding section 9 A having an octagonal columnar shape, and flat plate section 9 B having an octagonal shape and protruding from an outer circumference of protruding section 9 A. Cylindrical hole 9 C having a cylindrical shape is provided in a center of shaft supporter 9 to penetrate shaft supporter 9 . Center columnar section 6 A of operation shaft 6 is inserted into cylindrical hole 9 C. A caulking protrusion is crushed to fix click spring 10 to a lower surface of flat plate section 9 B.

Center columnar section 6 A of operation shaft 6 is inserted into circular hole 10 A provided in a center of click spring 10 . A spring 10 B is provide along an outer circumference of circular hole 10 A. Spring 10 B elastically contacts click grooves 6 D provided in the upper surface of annular flange 6 B.

Case 1 is made of resin and has recess 1 B therein opening upward. Center hole 1 A is provided in a center of a bottom surface of recess 1 B. A circular columnar protrusion provided at a center of a lower surface of operation shaft 6 is inserted into center hole 1 A. Case 1 supports operation shaft 6 rotatably.

Attachment bracket 7 has a squared U-shape and has a center hole. While protruding section 9 A of shaft supporter 9 protrudes upward from the center hole, attachment bracket 7 has legs 7 A to sandwich shaft supporter 9 and case 1 stacked on each other from above shaft supporter 9 . Tips of legs 7 A are bent at a lower surface of case 1 to accommodate operation shaft 6 and slidable brush 8 between shaft supporter 9 and case 1 .

FIG. 12 is a top view of case 1 of rotary encoder 501 . Center hole 1 A has a circular shape having center 1 D. Common contact 2 and signal contact patterns 3 and 4 are fixed to a bottom surface of recess 1 B by insert molding along circular circumference 1 E about center 1 D of center hole 1 A. Common contact 2 and signal contact patterns 3 and 4 are arranged in arcuate shapes on circumference 1 E.

As shown in FIG. 12 , signal contact pattern 3 includes signal contacts 3 A to 3 F connected electrically with each other. Signal contact pattern 4 includes signal contacts 4 A to 4 F connected electrically with each other. Signal contact patterns 3 and 4 and common contact 2 are embedded in the bottom surface of recess 1 B of case 1 so that upper surfaces of signal contacts 3 A to 3 F and 4 A to 4 F and upper surface of common contact 2 are flush with the bottom surface of recess 1 B of case 1 . Signal contacts 3 A to 3 F and 4 A to 4 F are provided on circumference 1 E. Signal contacts 3 A to 3 F are arranged on circumference 1 E within an angular range smaller than 180 degrees about center 1 D. Signal contacts 4 A to 4 F are arranged on circumference 1 E within an angular range smaller than 180 degrees about center 1 D. The angular range having the signal contacts 3 A to 3 F arranged therein is away from the angular range having signal contacts 4 A to 4 F arranged therein, that is, does not overlap the angular range having signal contacts 4 A to 4 F arranged therein. Common contact 2 has an arcuate shape on circumference 1 E. A center angle of the arcuate shape of common contact 2 is larger than the angular range having signal contacts 3 A to 3 F arranged therein and the angular range having signal contacts 4 A to 4 F arranged therein. Signal contact pattern 3 , signal contact pattern 4 , and common contact 2 are electrically insulated from each other, and are connected to terminals 11 A, 11 B, and 11 C extending to an outside of case 1 , respectively.

FIG. 13 is a top view of case 1 having rotary encoder 501 having slidable brush 8 arranged thereon. Slidable brush 8 is made of conductive elastic metal plate and is rotatable about center 1 D. Slidable brush 8 has contacting sections 81 A, 81 C, 81 E, and 81 G arranged with angular intervals of 90 degrees about center 1 D, and contacting sections 81 B, 81 D, 81 F, and 81 H located further inward than contacting sections 81 A, 81 C, 81 E, and 81 G, respectively.

An operation of conventional rotary encoder 501 will be described below.

Upon operation shaft 6 rotating, slidable brush 8 fixed to the lower surface of annular flange 6 B of operation shaft 6 rotates. The rotation of slidable brush 8 causes contacting sections 81 A to 81 H to slide on the bottom surface of recess 1 B of case 1 along circumference 1 E. Then, contacting sections 81 A to 81 H contact and are removed from signal contacts 3 A to 3 F and 4 A to 4 F and common contact 2 . The center angle of the arcuate shape of common contact 2 along circumference 1 E is larger than 90 degrees. Thus, regardless of the angular position of slidable brush 8 , at least two of contacting sections 81 A to 81 H contact common contact 2 , that is, slidable brush 8 contacts common contact 2 .

The angular range having signal contacts 3 A to 3 F arranged therein is smaller than 90 degrees, and the angular range having signal contacts 4 A to 4 F arranged therein is smaller than 90 degrees. Each of contacting sections 81 A and 81 B simultaneously contacts one of signal contacts 3 A to 3 F and 4 A to 4 F and common contact 2 . Similarly, each of contacting sections 81 C and 81 D simultaneously contacts one of signal contacts 3 A to 3 F and 4 A to 4 F and common contact 2 . Similarly, each of contacting sections 81 E and 81 F simultaneously contacts one of signal contacts 3 A to 3 F and 4 A to 4 F and common contact 2 . Similarly, each of contacting sections 81 G and 81 H simultaneously contacts one of signal contacts 3 A to 3 F and 4 A to 4 F and common contact 2 . Four contacting sections 81 A, 81 C, 81 E, and 81 G are arranged at the angular intervals of 90 degrees, and four contacting sections 81 B, 81 D, 81 F, and 81 H are arranged at the angular interval of 90 degrees. This arrangement causes each of six signal contacts 3 A to 3 F to contact and be removed from common contact 2 via slidable brush 8 repetitively four times while operation shaft 6 rotates by 360 degrees. Since signal contacts 3 A to 3 F are connected electrically with each other as signal contact pattern 3 , signal contact pattern 3 is connected to and disconnected from common contact 2 repetitively 24 times while operation shaft 6 rotates by 360 degrees. Similarly, each of six signal contacts 4 A to 4 F contact and are removed from common contact 2 via slidable brush 8 repetitively 4 times while operation shaft 6 rotates by 360 degrees to rotate slidable brush 8 by 360 degrees. Since signal contacts 4 A to 4 F are connected electrically with each other as signal contact pattern 4 , signal contact pattern 4 is connected to and disconnected from common contact 2 repetitively 24 times while operation shaft rotates by 360 degrees. Thus, rotary encoder 501 outputs rectangular wave A 501 having 24 peaks between terminals 11 A and 11 B due to the connection and disconnection between common contact 2 and signal contact pattern 3 while operation shaft 6 rotates by 360 degrees. Similarly, rotary encoder 501 outputs rectangular wave A 502 having 24 peaks between terminals 11 A and 11 C due to the connection and disconnection between common contact 2 and signal contact pattern 4 while operation shaft 6 rotates by 360 degrees.

The operation dial attached to operation shaft 6 is rotated to input rectangular waves A 501 and A 502 to a controller implemented by e.g. a microcomputer. Rotary encoder 501 is connected to the controller and is used e.g. to adjust the volume of a car audio system. In this case, the controller detects, based on rectangular waves A 501 and A 502 , a rotation direction and a rotation angle of the operation dial (i.e., operation shaft 6 ) to control the volume of the car audio system.

FIG. 14A illustrates rectangular waves A 501 and A 502 output from rotary encoder 501 . In FIG. 14A , rectangular waves A 501 and A 502 are shown by the turning on and off of a switch provided between common contact 2 and signal contact pattern 3 and by the turning on and off of a switch formed between common contact 2 and signal contact pattern 4 , respectively. The angular positions and angular widths of signal contacts 3 A to 3 F and 4 A to 4 F are determined such that rectangular waves A 501 and A 502 are output with a phase difference of 90 degrees. The combination of respective statuses of rectangular waves A 501 and A 502 provides four angular ranges θ 501 to θ 504 : (1) angular range θ 501 in which rectangular wave A 501 represents the turning on and rectangular wave A 502 represents the turning off; (2) angular range θ 502 in which rectangular waves A 501 and A 502 represent the turning on; (3) angular range θ 503 in which rectangular wave A 501 represents the turning off, and rectangular wave A 502 represents the turning on; and (4) angular range θ 504 in which rectangular waves A 501 and A 502 represent the turning off. Based on the order of angular ranges θ 501 to θ 504 , the controller determines a rotation direction of operation shaft 6 and counts the number of the peaks of rectangular waves A 501 and A 502 . The controller controls a controllable object based on the rotation direction and the number of the peaks. In the case that the object is the volume of the car audio system, the controller determines, based on the rotation direction, a changing direction along which the volume is increased or decreased. The controller further determines a change amount based on the number of the peaks. Then, the controller changes the volume by the determined change amount in the determined changing direction.

The widths of angular ranges θ 501 to θ 504 depend on the widths of signal contacts 3 A to 3 D and 4 A to 4 D along circumference 1 E. Signal contact patterns 3 and 4 are formed by punching a metal plate using dies designed to provide predetermined widths of angular ranges θ 501 to θ 504 . Rotary encoder 501 includes signal contact patterns 3 and 4 formed by the punching and embedded in the bottom surface of case 1 . Rotary encoder 501 may output waveforms different from the waveforms shown in FIG. 14A . FIG. 14B shows rectangular waves A 511 and A 512 output from rotary encoder 501 including signal contact patterns 3 and 4 formed by the punching, instead of rectangular waves A 501 and A 502 shown in FIG. 14A . Angular ranges θ 511 , θ 512 , θ 513 , and θ 514 shown in FIG. 14B represent statuses of the turning on and off as angular ranges θ 501 , θ 502 , θ 503 , and θ 504 shown in FIG. 14A , respectively. As shown in FIG. 14A , angular ranges θ 501 to θ 504 are equal to each other ideally. However, angular range θ 512 is particularly narrow out of angular ranges θ 511 , θ 512 , θ 513 , and θ 514 actually, as shown in FIG. 14B . Therefore, upon operation shaft 6 rotating, the microcomputer may not read angular range θ 512 if a duration in which contacting sections 81 A to 81 H of slidable brush 8 slide on in angular range θ 512 is excessively short.

FIG. 15 is a cross-sectional view of signal contact 3 A ( 3 B to 3 F and 4 A to 4 F) of rotary encoder 501 along circumference 1 E. Signal contacts 3 A to 3 F and 4 A to 4 F of signal contact patterns 3 and 4 are formed by punching out the metal plate. When the metal plate for forming signal contact 3 A is punched out with a die, the die pulls an edge of an upper surface of signal contact 3 in a punching direction, and thus, deforms signal contact 3 , thereby producing shear drop portion 14 B at the edge of the upper surface. Shear drop portion 14 B has a round shape like chamfering the edge of the upper surface. The lower surface of signal contact 3 A has burr 14 C produced by pulling a part of the metal downward with the die. Width L 1 of surface 14 A of signal contact 3 A exposed on the bottom surface of recess 1 B is smaller than width L 2 of signal contact 3 A. This structure causes the resin of case 1 to cover shear drop portion 14 B of signal contact 3 A. Width L 2 of signal contact 3 A is determined to provide the predetermined lengths of angular ranges θ 501 to θ 504 . However, width L 1 of surface 14 A of signal contact 3 A exposed on the bottom surface of recess 1 B of case 1 is smaller than determined width L 2 of signal contact 3 A. Thus, the angular range in which slidable brush 8 contacts signal contact 3 A during the rotation of operation shaft 6 is smaller than the predetermined angular range. This reduces the angular ranges in which the switches formed between common contact 2 and signal contact pattern 3 and between common contact 2 and signal contact pattern 4 are turned on. Angular range θ 512 in which rectangular waves A 511 and A 512 represent the turning on is accordingly shorter than other angular ranges θ 511 , θ 513 , and θ 514 , as shown in FIG. 14B .

Under a demand to have a smaller size and operate precisely, rotary encoder 501 is demanded to have smaller widths of signal contacts 3 A to 3 F and 4 A to 4 F and smaller intervals between signal contacts 3 A to 3 F and 4 A to 4 F. The shape of shear drop portion 14 B of signal contacts 3 A to 3 D and 4 A to 4 D changes depending on material of the metal plate or conditions of the punching, thus being unpredictable. Thus, shear drop portion 14 B may be a factor preventing rotary encoder 501 from having a small size and operating precisely.

A rotary encoder includes a case made of insulating resin, a rotatable operation shaft, a slidable brush fixed to the operation shaft, and a signal contact embedded in a surface of the case. The slidable brush has a contacting section sliding on a surface of the case on a predetermined circumference according to a rotation of the operation shaft. The signal contact has an upper surface flush with the surface of the case, a first side surface connected to the upper surface at a first corner having a right angle, a second side surface connected to the upper surface at a second corner having a right angle, and a lower surface opposite to the upper surface. The first and side surfaces are positioned on the predetermined circumference. The lower surface has a width smaller than a width of the upper surface.

This rotary encoder has a small size and outputs a signal precisely.

FIG. 1 is a cross-sectional view of a rotary encoder according to an exemplary embodiment of the present invention.

FIG. 2 is an exploded perspective view of the rotary encoder according to the embodiment.

FIG. 3 is a top view of a case of the rotary encoder according to the embodiment.

FIG. 4 is a top view of the case of the rotary encoder according to the embodiment.

FIG. 5 illustrates a signal output from the rotary encoder according to the embodiment.

FIG. 6 is a cross-sectional view of a signal contact of the rotary encoder according to the embodiment.

FIGS. 7A and 7B are cross-sectional views of the rotary encoder according to the embodiment for illustrating a method of manufacturing the rotary encoder.

FIG. 8 is a top view of a contact plate hoop for preparing a signal contact of the rotary encoder according to the embodiment.

FIGS. 9A and 9B are a cross-sectional view of the signal contact of the rotary encoder according to the embodiment for illustrating a method of manufacturing the signal contact.

FIG. 10 is a cross-sectional view of a conventional rotary encoder.

FIG. 11 is an exploded perspective view of a conventional rotary encoder.

FIG. 12 is a top view of a case of a conventional rotary encoder.

FIG. 13 is a top view of the case of a conventional rotary encoder.

FIGS. 14A and 14B illustrate signals output from the conventional rotary encoder.

FIG. 15 is a cross-sectional view of a signal contact of a conventional rotary encoder.

FIGS. 1 and 2 are a cross-sectional view and an exploded perspective view of rotary encoder 1001 according to an exemplary embodiment of the present invention, respectively. Operation shaft 6 is made of insulating resin. Operation shaft 6 has center columnar section 6 A having a circular columnar shape and annular flange 6 B protruding from an outer circumference of center columnar section 6 A. The upper part of center columnar section 6 A has cutout 6 C therein adapted for engagement in an operation dial. Click grooves 6 D extending radially are formed in an upper surface of annular flange 6 B. A caulking protrusion is crushed to fix slidable brush 8 to a lower surface of annular flange 6 B.

Shaft supporter 9 is made of resin and has protruding section 9 A having an octagonal shape and flat plate section 9 B having an octagonal shape and protruding from an outer circumference of protruding section 9 A. Cylindrical hole 9 C having a cylindrical shape is provided in a center of shaft supporter 9 and penetrates shaft supporter 9 . Center columnar section 6 A of operation shaft 6 is inserted into cylindrical hole 9 C. A caulking protrusion is crushed to fix click spring 10 to a lower surface of flat plate section 9 B.

Center columnar section 6 A of operation shaft 6 is inserted into circular hole 10 A provided at the center of click spring 10 . Spring 10 B having a ring shape is provided around an outer circumference of circular hole 10 A. Spring 10 B elastically contacts click grooves 6 D provided in the upper surface of annular flange 6 B and applies an appropriate torque to operation shaft 6 while operation shaft 6 rotates.

Case 21 is made of insulating resin and has recess 21 B opening upward. Center hole 21 A is provided at a center of a bottom surface 21 F of recess 21 B has center hole 21 A. Circular columnar protrusion 6 E provided at a center of a lower surface of operation shaft 6 is inserted into center hole 21 A. Case 21 supports operation shaft 6 rotatably. Center hole 21 A has a circular shape having center 21 D.

Attachment bracket 7 has a squared U-shape and has a center hole. While protruding section 9 A of shaft supporter 9 protrudes upward from the center hole, attachment bracket 7 has legs 7 A to sandwich shaft supporter 9 and case 21 stacked on each other from above shaft supporter 9 . Tips of legs 7 A are bent at lower surface 21 G of case 21 to accommodate operation shaft 6 and slidable brush 8 between shaft supporter 9 and case 21 .

FIG. 3 is a top view of case 21 of rotary encoder 1001 . Center hole 21 A has a circular shape having center 21 D. Common contact 22 and signal contact patterns 23 and 24 are fixed to a bottom surface of recess 21 B by insert molding along circular circumference 21 E about center 21 D of center hole 21 A. Common contact 22 and signal contact patterns 23 and 24 are arranged in arcuate shapes on circumference 21 E.

As shown in FIG. 3 , signal contact pattern 23 has signal contacts 23 A to 23 F connected electrically with each other, and signal contact pattern 24 has signal contacts 24 A to 24 F connected electrically with each other. Signal contact patterns 23 and 24 and common contact 22 are embedded in bottom surface 21 F of recess 21 B of case 21 so that upper surfaces of signal contacts 23 A to 23 F and 24 A to 24 F and common contact 22 are flush with bottom surface 21 F of recess 21 B of case 21 . Signal contacts 23 A to 23 F and 24 A to 24 F are arranged on circumference 21 E. Signal contacts 23 A to 23 F are provided on circumference 21 E within angular range A 23 smaller than 180 degrees about center 21 D. Signal contacts 24 A to 24 F are arranged on circumference 21 E within angular range A 24 smaller than 180 degrees around center 21 D. Angular range A 23 having signal contacts 23 A to 23 F arranged therein is away from angular range A 24 having signal contacts 24 A to 24 F arranged therein, that is, does not overlap angular range A 24 . Common contact 22 is provided on circumference 21 E and has an arcuate shape. Angular range A 22 , a center angle of the arcuate shape of common contact 22 , is larger than angular range A 23 having signal contacts 23 A to 23 F arranged therein and angular range A 24 having signal contacts 24 A to 24 F arranged therein. Angular ranges A 22 , A 23 , and A 24 are away from each other, that is, do not overlap each other. Signal contact pattern 23 , signal contact pattern 24 , and common contact 22 are electrically insulated from each other, and are connected to terminals 11 A, 11 B, and 11 C extending to an outside of case 21 , respectively.

FIG. 4 is a top view of case 21 of rotary encoder 1001 having slidable brush 8 provided therein. Slidable brush 8 is made of conductive elastic metal plate, and rotatable about center 21 D. Slidable brush 8 has contacting sections 81 A, 81 C, 81 E, and 81 G arranged about center 21 D at angular intervals of 90 degrees, and has contacting sections 81 B, 81 D, 81 F, and 81 H arranged about center 21 D at angular intervals of 90 degrees. Contacting sections 81 B, 81 D, 81 F, and 81 H deviate from contacting sections 81 A, 81 C, 81 E, and 81 G in directions toward center 21 D, respectively, that is, are located further inward than contacting sections 81 A, 81 C, 81 E, and 81 G, respectively. As shown in FIG. 4 , contacting sections 81 A and 81 B contact common contact 22 . Contacting sections 81 C and 81 D contact a center of signal contact 24 C. Contacting section 81 E and 81 F do not contact any of signal contacts 23 A to 23 F, 24 A to 24 F and common contact 22 . Contacting sections 81 G and 81 H contact edge 123 F of signal contact 23 F.

An operation of rotary encoder 1001 will be described below.

Upon operation shaft 6 being rotated, slidable brush 8 fixed to the lower surface of annular flange 6 B of operation shaft 6 rotates. The rotation of slidable brush 8 causes contacting sections 81 A to 81 H to slide on bottom surface 21 F of recess 21 B of case 21 in direction D 1 along circumference 21 E. Then, contacting sections 81 A to 81 H contact and are removed from signal contacts 23 A to 23 F and 24 A to 24 F and common contact 22 . In particular, contacting sections 81 A, 81 C, 81 E, and 81 G slide on bottom surface 21 F, signal contacts 23 A to 23 F and 24 A to 24 F, and common contact 22 on circumference 21 E. Angular range A 22 , the center angle of the circular arcuate shape of common contact 22 , provided along circumference 21 E is larger than 90 degrees. Thus, regardless of an angular position of slidable brush 8 , at least two of contacting sections 81 A to 81 H contact common contact 22 , that is, slidable brush 8 contacts common contact 22 .

Angular range A 23 having signal contacts 23 A to 23 F arranged therein is smaller than 90 degrees. Angular range A 24 having signal contacts 24 A to 24 F arranged therein is also smaller than 90 degrees. Contacting sections 81 A and 81 B simultaneously contact one of signal contacts 23 A to 23 F and 24 A to 24 F. Similarly, contacting sections 81 C and 81 D simultaneously contact one of signal contacts 23 A to 23 F and 24 A to 24 F. Similarly, contacting sections 81 E and 81 F simultaneously contact one of signal contacts 23 A to 23 F and 24 A to 24 F. Similarly, contacting sections 81 G and 81 H simultaneously contact one of signal contacts 23 A to 23 F and 24 A to 24 F and common contact 22 . Four contacting sections 81 A, 81 C, 81 E, and 81 G are arranged at angular intervals of 90 degrees, and four contacting sections 81 B, 81 D, 81 F, and 81 H are arranged at angular interval of 90 degrees. Thus, while operation shaft 6 is rotated 360 degrees to rotate slidable brush 8 by 360 degrees, each of six signal contacts 23 A to 23 F contacts and is removed from common contact 22 via slidable brush 8 repetitively 4 times. Signal contacts 23 A to 23 F are connected electrically with each other as signal contact pattern 3 . Therefore, while operation shaft 6 is rotated by 360 degrees, signal contact pattern 23 are connected with and disconnected from common contact 22 repetitively 24 times. Similarly, while operation shaft 6 is rotated by 360 degrees to rotate slidable brush 8 by 360 degrees, each of six signal contacts 24 A to 24 F contacts and is removed from common contact 22 via slidable brush 8 repetitively 4 times. Signal contacts 24 A to 24 F are connected electrically with each other as signal contact pattern 24 . Therefore, while operation shaft 6 is rotated by 360 degrees, signal contact pattern 24 is connected with and disconnected from common contact 22 repetitively 24 times. Thus, while operation shaft 6 is rotated by 360 degrees, the connection and disconnection between common contact 22 and signal contact pattern 23 allows rotary encoder 1001 to output rectangular wave A 1 having 24 peaks between terminals 11 A and 11 B. Similarly, the connection and disconnection between common contact 22 and signal contact pattern 24 allows rotary encoder 1001 to output rectangular wave A 2 having 24 peaks between terminals 11 A and 11 C.

The operation dial attached to operation shaft 6 is rotated to input rectangular waves A 1 and A 2 to a controller implemented by e.g. a microcomputer. Rotary encoder 1001 is connected to the controller and is used e.g. to adjust the volume of a car audio system. In this case, the controller detects, based on rectangular waves A 1 and A 2 , a rotation direction and a rotation angle of the operation dial (i.e., operation shaft 6 ) to control the volume of the car audio system.

FIG. 5 illustrates rectangular waves A 1 and A 2 output from rotary encoder 1001 . In FIG. 5 , rectangular wave A 1 represents the turning on and off of a switch formed between common contact 22 and signal contact pattern 23 , and rectangular wave A 2 represents the turning on and off of a switch formed between common contact 22 and signal contact pattern 24 , respectively. The angular positions and widths of signal contacts 23 A to 23 F and 24 A to 24 F are determined such that rectangular waves A 1 and A 2 are output with a phase difference of 90 degrees. The combination of rectangular waves A 1 and A 2 provides four angular ranges θ 1 to θ 4 : (1) angular range θ 1 in which rectangular wave A 1 represents the turning on, and rectangular wave A 2 represents the turning off; (2) angular range θ 2 in which rectangular waves A 1 and A 2 represent the turning on; (3) angular range θ 3 in which rectangular wave A 1 represents the turning off, and rectangular wave A 2 represents the turning on; and (4) angular range θ 4 in which rectangular waves A 1 and A 2 represent the turning off. Based on the order of angular ranges θ 1 to θ 4 , the controller determines a rotation direction of operation shaft 6 and counts the number of the peaks of rectangular waves A 1 and A 2 . Based on the rotation direction and the number of the peaks, the controller controls a controllable object. In the case that the object is the volume of the car audio system, the controller determines, based on the rotation direction, a changing direction in which the volume is increased or decreased. The controller also determines a change amount based on the number of the peaks. Then, the controller changes the volume by the determined change amount in the determined changing direction.

In rotary encoder 1001 according to the embodiment, shapes of signal contacts 23 A to 23 F and 24 A to 24 F are determined so as to output ideal rectangular waves A 501 and A 502 shown in FIG. 14A . FIG. 6 is a cross-sectional view of signal contact 23 A ( 23 B to 23 F and 24 A to 24 F) along circumference 21 E. Signal contact 23 A (signal contact pattern 3 ) is embedded in bottom surface 21 F of case 21 , and has upper surface 31 being exposed and being flush with bottom surface 21 F of recess 21 B of case 21 . The lengths of angular ranges θ 1 to θ 4 shown in FIG. 5 depend on width L 11 of upper surface 31 of signal contact 23 A ( 23 B to 23 F and 24 A to 24 F) in direction D 1 along circumference 21 E. Signal contact 23 A ( 23 B to 23 F and 24 A to 24 F) further has side surface 51 connected with upper surface 31 at corner 53 and side surface 52 connected with upper surface 31 at corner 54 . Corners 53 and 54 are positioned opposite to each other across upper surface 31 . Side surfaces 51 and 52 are arranged opposite to each other in direction D 1 . Corners 53 and 54 are positioned on circumference 21 E and contact contacting sections 81 A, 81 C, 81 E, and 81 G of slidable brush 8 . Corners 53 and 54 each have a right angle. Signal contact 23 A further has flat lower surface 55 opposite to upper surface 31 . Lower surface 55 has width L 3 in direction D 1 . Width L 11 of upper surface 31 in direction D 1 along circumference 21 E is larger than width L 3 of lower surface 55 . The cross section of signal contact 23 A along circumference 21 E has substantially a trapezoidal shape. Side surfaces 51 and 52 have recesses 51 A and 52 A therein, respectively. Resin material of case 21 enters recesses 51 A and 52 A and prevents signal contact 23 A ( 23 B to 23 F, 24 A to 24 F) embedded in bottom surface 21 F of case 21 from being removed from bottom surface 21 F of case 21 upward.

Rotary encoder 1001 is not provided with shear drop portions 14 B of conventional rotary encoder 501 shown in FIG. 15 , and each of corners 53 and 54 of signal contact 23 A ( 23 B to 23 F, 24 A to 24 F) defines a right angle. Therefore, resin material of case 21 does not cover upper surface 31 of signal contact 23 A. Thus, width L 11 of upper surface 31 in direction D 1 is equal to width L 2 of the signal contact, thus causing substantially no variation of width L 11 .

A method of manufacturing rotary encoder 1001 will be described.

FIGS. 7A and 7B are cross-sectional views of signal contact patterns 23 and 24 of rotary encoder 1001 for illustrating the method of manufacturing contact patterns 23 and 24 . As shown in FIG. 7A , metal plate 61 , such as a brass plate, is placed on punching stand 25 to punch out metal plate 61 with punching die 26 from upper surface 61 A, as shown in FIG. 7B . This punching processing provides incomplete contacts 33 A and 33 B to become signal contacts 23 A and 23 B, respectively. Incomplete contact 33 A ( 33 B) has upper surface 62 to become upper surface 31 of signal contact 23 A ( 23 B) and lower surface 64 opposite to upper surface 62 . When metal plate 61 is punched out with punching die 26 from upper surface 61 A, die 26 pulls side surface 63 of incomplete contact 33 A ( 33 B) in direction D 2 from upper surface 62 to lower surface 64 . This produces shear drop portions 27 A at a corner connecting upper surface 62 and side surface 63 and burr 27 B protruding in direction D 2 at a corner connecting lower surface 64 and side surface 63 .

FIG. 8 is a top view of contact plate hoop 30 providing signal contact patterns 23 and 24 and common contact 22 . As shown in FIGS. 7A and 7B , contact plate hoop 30 is obtained by punching out metal plate 61 with punching die 26 and punching stand 25 . Contact plate hoop 30 includes contact plates 30 C and outer frame 30 B connected to contact plates 30 C. Contact plates 30 C have incomplete contact patterns 33 and 34 and incomplete contact 32 . Outer frame 30 B has positioning holes 30 A therein arranged at predetermined intervals. Incomplete contact patterns 33 and 34 and incomplete contact 32 provide signal contact patterns 23 and 24 and common contact 22 , respectively. Incomplete contact pattern 33 has incomplete contacts 33 A to 33 F providing signal contacts 23 A to 23 F, respectively. Incomplete contact pattern 34 has incomplete contacts 34 A to 34 F providing signal contacts 24 A to 24 F, respectively. Incomplete contacts 33 C to 33 F and 34 A to 34 F have shear drop portions 27 A and burrs 27 B similarly to incomplete contacts 33 A and 33 B shown in FIG. 7B .

Contact plate hoop 30 further includes incomplete terminals 41 A, 41 B and 41 C providing terminals 11 A and 11 B, 11 C, respectively. Incomplete terminal 41 A is connected to incomplete contact pattern 33 . Incomplete terminal 41 B is connected to incomplete contact pattern 34 . Incomplete terminal 41 C is connected to incomplete contact 32 .

FIGS. 9A and 9B are cross-sectional views of signal contact 23 A ( 23 B to 23 F and 24 A to 24 F) for illustrating a method of manufacturing signal contact 23 A. Incomplete contact 33 A ( 33 B to 33 F and 34 A to 34 F) is formed with dies 28 and 29 to provide signal contact 23 A ( 23 B to 23 F and 24 A to 24 F). Die 29 presses lower surface 64 of incomplete contact 33 A. Upper surface 29 D of die 29 has recess 29 C. Recess 29 C has flat bottom surface 29 A and slope surfaces 29 B extending from bottom surface 29 A to upper surface 29 D. Slope surfaces 29 B are positioned opposite to each other across bottom surface 29 A. Bottom surface 29 A presses a center portion of lower surface 64 of incomplete contact 33 A toward upper surface 62 upward. Slope surfaces 29 B press burrs 27 B toward a center of incomplete contact 33 A so as to press burrs 27 B inward and upward. Lower surface 28 D of die 28 has recess 28 C therein. Recess 28 C has flat bottom surface 28 A and side surfaces 28 B extending from bottom surface 28 A to upper surface 28 D. Bottom surface 28 A presses upper surface 62 of incomplete contact 33 A downward toward lower surface 64 . A corner connecting bottom surface 28 A and each of side surfaces 28 B defines a right angle to form a right angle forming section.

As shown in FIG. 9B , signal contact 23 A is formed by pressing incomplete contact 33 A in recesses 28 C and 29 C of dies 28 and 29 . Each of slope surfaces 29 B of die 29 presses each of burrs 27 B downward towards the center of incomplete contact 33 A. Incomplete contact 33 A is pressed onto the right angle forming sections each defining a right angle. This process provides signal contact 23 A having corners 53 of upper surface 31 each having a right angle. Dies 28 and 29 press incomplete contact 33 A in between, and form recesses 51 A and 52 A in side surfaces 51 and 52 . Signal contacts 23 B to 23 F and 24 A to 24 F are also formed similarly to signal contact 23 A by forming incomplete contacts 33 B to 33 F and 34 A to 34 F with dies 28 and 29 .

Then, contact plate hoop 30 is molded with resin material, thus insert-molding hoop 30 . Then, outer frame 30 B is cut to be removed from signal contact patterns 33 and 34 , common contact 22 , and terminals 11 A to 11 C to provide case 21 . Thus, signal contacts 23 A to 23 F, 24 A to 24 F are molded with resin material, thus insert-molding them. Then, outer frame 30 B is cut to be removed from signal contact patterns 33 and 34 , common contact 22 , and terminals 11 A to 11 C to provide case 21 .

As shown in FIG. 2 , the caulking protrusion is provided on the lower surface of operation shaft 6 is crushed to fix slidable brush 8 to the lower surface of operation shaft 6 . The caulking protrusion provided on the lower surface of shaft supporter 9 to fix click spring 10 to the lower surface of shaft supporter 9 . Then, operation shaft 6 having slidable brush 8 fixed thereto and shaft supporter 9 having click spring 10 fixed thereto are stacked on case 21 . Then, attachment bracket 7 holds a range from the top of shaft supporter 9 to lower surface 21 G of case 21 , and legs 7 A fix attachment bracket 7 to case 21 , thereby providing rotary encoder 1001 .

In rotary encoder 1001 according to this embodiment, width L 11 of upper surface 31 exposed from bottom surface 21 F of recess 21 B of case 21 of signal contact 23 A ( 23 B to 23 F and 24 A to 24 F) is equal to width L 2 of signal contact 23 A. Upper surface 31 is accurately formed with recess 28 C of die 28 . Thus, widths of angular ranges θ 1 to θ 4 shown in FIG. 5 can be predetermined widths to allow the controller to read angular ranges θ 1 to θ 4 reliably, accordingly allowing the rotary encoder 1001 to detect the rotation direction and the rotation amount of operation shaft 6 precisely.

Corners 53 and 54 of upper surface 31 of signal contacts 23 A to 23 F and 24 A to 24 F determine an accuracy of the signals. According to the embodiment, dies 28 and 29 allow each of corners 53 and 54 easily to have a right angle accurately. This process reduces intervals between signal contacts 23 A to 23 F and 24 A to 24 F, and accordingly, allows rotary encoder 1001 to have a small size and to be precise.

According to the embodiment, terms, such as “upper surface”, “lower surface”, “upward”, and “downward”, indicating directions indicate relative directions depending on the positions of components constituting rotary encoder 1001 , and do not indicate absolute directions, such as a vertical direction.