Patent Publication Number: US-2013249538-A1

Title: Rotation angle and torque detection device

Description:
TECHNICAL FIELD 
     The present technical field relates to a rotation angle and torque detection device mainly used for detecting a rotation angle and rotation torque of steering of an automobile. 
     BACKGROUND ART 
     In recent years, a brake, power steering, or the like, of an automobile has been controlled by detecting a rotation angle and rotation torque of steering of an automobile by using a rotation angle detection device or a rotation torque detection device. 
       FIG. 5  is an exploded perspective view of a conventional rotation angle and torque detection device. Cylindrical first rotating body  1  rotates together with steering of an automobile. Cylindrical first magnet  3  includes a plurality of N-poles and S-poles that are formed alternately and adjacently. First magnet  3  is fixed to the outer periphery of a lower end of cylindrical holding body  2 . The outer periphery of an upper part of holding body  2  is fixed to an upper part of the inner periphery of first rotating body  1 . 
     Cylindrical second rotating body  4  is disposed in the lower side of first rotating body  1 . Ring-shaped first magnetic body  5  and ring-shaped second magnetic body  6  are disposed with spacer  7  interposed therebetween on second rotating body  4 . First magnetic body  5  and second magnetic body  6  are disposed with a predetermined space with respect to the outer periphery of first magnet  3 . First magnetic body  5  is provided with a plurality of protruding portions  5 A on the inner periphery thereof. Second magnetic body  6  is provided with a plurality of protruding portions  6 A on the inner periphery thereof. 
     Wiring board  8  is disposed on the side parts of first rotating body  1  and second rotating body  4 . Wiring board  8  has a plurality of wirings (not shown) on both surfaces thereof. First magnetism detecting element  9  such as a Hall element is laid out on the outside of spacer  7  such that it faces first magnet  3 . 
     Spur gear  4 A formed on the lower surface of the outer periphery of second rotating body  4  meshes with spur gear  10 A of first detecting body  10 . Furthermore, spur gear  10 A meshes with spur gear  11 A of second detecting body  11 . The number of cogs of spur gear  10 A is different from the number of cogs of spur gear  11 A. 
     Second magnet  12 A is mounted on the middle of first detecting body  10  by, for example, insert molding. Third magnet  13 A is mounted on the middle of second detecting body  11  by, for example, insert molding. Second magnetism detecting element  12 B such as an AMR (anisotropic magnetic resistance) element is mounted on a surface that faces second magnet  12 A in wiring board  8 . Third magnetism detecting element  13 B such as an AMR element is mounted on a surface that faces third magnet  13 A in wiring board  8 . 
     Wiring board  8  includes control circuit  14  formed of an electronic component such as microcomputer. First magnetism detecting element  9 , second magnetism detecting element  12 B, and third magnetism detecting element  13 B are coupled to control circuit  14  via wirings (not shown). 
     The upper end of connecting body  15  such as a columnar torsion bar made of, for example, copper is fixed to first rotating body  1 , and the lower end thereof is fixed to second rotating body  4 , respectively. The rotation angle and torque detection device configured as mentioned above is attached to a steering shaft of an automobile and mounted on the lower side of the steering. Control circuit  14  is coupled to an electronic circuit (not shown) of an automobile main body via a connector, a lead wire (not shown), or the like. 
     Turning the steering allows first rotating body  1  to rotate and connecting body  15  to twist. Then, second rotating body  4  is rotated after a slight delay from the rotation of first rotator  1 . For example, when a vehicle runs, the delay of second rotating body  4  relative to first rotating body  1  is small because rotation torque is small. On the other hand, when the vehicle is stopping, the delay of second rotating body  4  becomes large because the rotation torque is large. 
     According to the rotation of first rotating body  1 , first magnet  3  is rotated. Then, according to the rotation of second rotating body  4 , first magnetic body  5  and second magnetic body  6  are also rotated after a slight delay from the rotation of first magnet  3 . First magnetism detecting element  9  detects magnetic variations of the N-poles and S-poles formed alternately and adjacently of first magnet  3  via first magnetic body  5  and second magnetic body  6 , and this torque detection signal is input into control circuit  14 . 
     First magnet  3  is fixed to first rotating body  1 . Second magnetic body  6  is fixed to second rotating body  4 . Magnetism detected by first magnetism detecting element  9  is weak when a delay of the rotation of second rotating body  4  is small with respect to first rotating body  1 , and strong when the delay of the rotation is large. 
     Based on strength and weakness of the magnetism detected by first magnetism detecting element  9  via first magnetic body  5  and second magnetic body  6 , control circuit  14  calculates rotation torque of first rotating body  1  (that is, rotation torque of the steering). Then, control circuit  14  outputs a rotation torque signal to an electronic circuit of a vehicle main body. 
     Furthermore, since spur gear  4 A formed on the lower surface of the outer periphery of second rotating body  4  is rotated according to the rotation of second rotating body  4 , first detecting body  10  and second detecting body  11  rotate together with each other. 
     According to the rotation of first detecting body  10  and second detecting body  11 , second magnet  12 A and third magnet  13 A are also rotated. Second magnetism detecting element  12 B detects magnetism by second magnet  12 A. Third magnetism detecting element  13 B detects magnetism by third magnet  13 A. Magnetic variations detected by second magnetism detecting element  12 B and third magnetism detecting element  13 B are input as sine wave, cosine wave, or a saw-tooth angle detection signal into control circuit  14 . 
     The number of cogs of spur gear  10 A of first detecting body  10  is different from that of spur gear  11 A of second detecting body  11 . Therefore, an angle detection signal output from second magnetism detecting element  12 B is different from an angle detection signal output from third magnetism detecting element  13 B in terms of inclining angles and shapes of waveforms, so that those signals are input into control circuit  14  as signals having a phase difference. 
     Then, control circuit  14  calculates a rotation angle of second rotating body  4 , that is, a rotation angle of the steering by carrying out a predetermined arithmetic operation based on the two different angle detection signals from first detecting body  10  and second detecting body  11  and the numbers of spur gear  10 A and spur gear  11 A. Then, control circuit  14  outputs a rotation angle signal to the electronic circuit of an automobile main body. The electronic circuit arithmetically operates the rotation angle signal or the rotation torque signal of the above-mentioned control circuit  14 , and controls power steering, a brake, or the like. 
     In other words, control circuit  14  calculates the rotation torque of the steering based on the torque detection signal from first magnetism detecting element  9 , and calculates the rotation angle based on the angle detection signal from second magnetism detecting element  12 B and third magnetism detecting element  13 B. In response to the rotation torque signal or the rotation angle signal output from control circuit  14 , the electronic circuit carries out control of effectiveness of a brake corresponding to the rotation angle of the steering, control of force to rotate the steering, or the like. 
     SUMMARY 
     A rotation angle and torque detection device includes a first rotating body, a second rotating body, a first magnet, a first magnetism detecting element, a first detecting body, a second magnet, a second magnetism detecting element, a second detecting body, a third magnet, a third magnetism detecting element, and a control circuit. The control circuit outputs a rotation torque signal and a rotation angle signal. The first magnetism detecting element outputs a torque detection signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a rotation angle and torque detection device in accordance with an embodiment. 
         FIG. 2  is an exploded perspective view of the rotation angle and torque detection device shown in  FIG. 1 . 
         FIG. 3  is a view for illustrating relation between a first magnet and third magnetic bodies of the rotation angle and torque detection device when steering is stationary in accordance with this embodiment. 
         FIG. 4  is a view for illustrating the relation between the first magnet and the third magnetic bodies of the rotation angle and torque detection device when the steering is turned in accordance with this embodiment. 
         FIG. 5  is an exploded perspective view of a conventional rotation angle and torque detection device. 
     
    
    
     DETAILED DESCRIPTION 
     In a rotation angle and torque detection device shown in  FIG. 5 , a rotation torque signal and a rotation angle signal are output from control circuit  14  to an electronic circuit of a vehicle. However, when failure such as breakdown occurs in control circuit  14 , neither rotation torque signal nor rotation angle signal is input into the electronic circuit. Consequently, the electronic circuit cannot determine whether control circuit  14  has failure or the steering is not turned. In order to sense this, it is necessary to provide another sensor or the like, and to detect rotation of first rotating body  1 , second rotating body  4 , or the like, resulting in making the configuration complicated and expensive. 
     Hereinafter, a rotation angle and torque detection device in accordance with this embodiment is described.  FIG. 1  is a sectional view of a rotation angle and torque detection device in accordance with an embodiment.  FIG. 2  is an exploded perspective view of the rotation angle and torque detection device shown in  FIG. 1 . 
     The rotation angle and torque detection device includes first rotating body  21 , second rotating body  23 , first magnet  22 , first magnetism detecting element  28 , first detecting body  29 , second magnet  31 A, second magnetism detecting element  31 B, second detecting body  30 , third magnet  32 A, third magnetism detecting element  32 B, and control circuit  33 . Control circuit  33  outputs a rotation torque signal and a rotation angle signal, while first magnetism detecting element  28  outputs a torque detection signal. The rotation angle and torque detection device further includes first magnetic body  24 , second magnetic body  25 , third magnetic body  26 , and wiring board  27 . 
     Cylindrical first rotating body  21  rotates together with steering, and has spur gear  21 A on the outer periphery thereof. First rotating body  21  is made of insulating resin such as polybutylene terephthalate. 
     First magnet  22  is fixed to the outer periphery of first rotating body  21 , and on the lower surface of spur gear  21 A. Cylindrical first magnet  22  includes a plurality of N-poles and S-poles formed alternately and adjacently in the circumferential direction. First magnet  22  is made of ferrite, Nd—Fe—B alloy, or the like. 
     Cylindrical second rotating body  23  is disposed in the lower side of first rotating body  21 . First magnetic body  24  and second magnetic body  25  are disposed so as to surround first magnet  22 . First magnetic body  24  and second magnetic body  25  are formed by winding a belt-like plate material in a ring shape. Second rotating body  23  is made of insulating resin such as polybutylene terephthalate. Both first magnetic body  24  and second magnetic body  25  are made of permalloy, iron, Ni—Fe alloy, or the like. 
     A plurality of rectangular third magnetic bodies  26  are arranged by insert molding, press-hitting, or the like, at a predetermined interval inside second rotating body  23 . Second rotating body  23  is disposed on the outside of first magnet  22  and inside of first magnetic body  24  and second magnetic body  25 . Third magnetic body  26  is made of permalloy, iron, Ni—Fe alloy, or the like. 
     Wiring board  27  made of paper phenol, glass-containing epoxy, or the like, is disposed so as to surround the outer periphery of second rotating body  23 . On the upper and lower surfaces of wiring board  27 , a plurality of wirings (not shown) are formed of, for example, copper foil. A plurality of first magnetism detecting elements  28  are disposed such that they face first magnet  22  between first magnetic body  24  and second magnetic body  25 . First magnetism detecting elements  28  are formed of, for example, a Hall element for detecting magnetism in the vertical direction or a GMR element (giant magnetoresistive element) for detecting magnetism in the horizontal direction. 
     First detecting body  29  is made of insulating resin or metal, and has spur gear  29 A on the outer periphery of the side surface. Second detecting body  30  is made of insulating resin or metal and has spur gear  30 A whose number of cogs is different from that of spur gear  29 A on the outer periphery of the side surface. Spur gear  21 A of first rotating body  21  and spur gear  29 A of first detecting body  29  mesh with each other. Furthermore, spur gear  29 A of first detecting body  29  and spur gear  30 A of second detecting body  30  mesh with each other. 
     Note here that the diameter and the number of cogs of the gear are largest in first rotating body  21 , and they become smaller in first detecting body  29 , and second detecting body  30  in this order. For example, the number of cogs of spur gear  21 A is  48 , the number of cogs of spur gear  29 A is  32 , and the number of cogs of spur gear  30 A is  28 . 
     Furthermore, in the middle part of first detecting body  29 , second magnet  31 A made of ferrite, Nd—Fe—B alloy, or the like, is mounted by, for example, insert molding. In the middle part of second detecting body  30 , third magnet  32 A made of ferrite, Nd—Fe—B alloy, or the like, is mounted by, for example, insert molding. Second magnetism detecting element  31 B such as an AMR (anisotropic magnetic resistance) element is mounted on the surface that faces second magnet  31 A in wiring board  27 . Third magnetism detecting element  32 B such as an AMR element is mounted on the surface that faces third magnet  32 A in wiring board  27 . 
     Wiring board  27  includes control circuit  33  formed of an electronic component such as microcomputer. A plurality of first magnetism detecting elements  28 , second magnetism detecting element  31 B, and third magnetism detecting element  32 B are coupled to control circuit  33  via wirings. 
     Furthermore, case  34  is provided with connect part  34 A. Case  34  is made of insulating resin with its upper surface opened. Connect part  34 A has a plurality of terminals  35  of, for example, copper alloy, attached thereon. The plurality of terminals  35  are connected to wiring board  27 . At least one of second magnetism detecting element  31 B and third magnetism detecting element  32 B, a plurality of first magnetism detecting elements  28 , and control circuit  33  are coupled to a plurality of terminals  35  via wiring. 
     Cover  36  made of insulating resin covers the upper surface of case  34 . First rotating body  21 , second rotating body  23 , wiring board  27 , and the like, are accommodated inside cover  36  and case  34 . 
     Then, connecting body  50  that is a columnar torsion bar made of, for example, copper, is fixed to first rotating body  21  at the upper end (first end) thereof, and fixed to second rotating body  23  at the lower end (second end) thereof, respectively. The rotation angle and torque detection device configured as mentioned above is attached to a steering shaft, and mounted on the lower side of steering of an automobile. First magnetism detecting element  28  and control circuit  33  are coupled to an electronic circuit (not shown) of an automobile main body via a plurality of terminals  35 , lead wires (not shown), or the like. 
     Turning the steering allows first rotating body  21  to rotate and connecting body  50  to twist. Then, second rotating body  23  is rotated after a slight delay from the rotation of first rotator  21 . For example, when a vehicle runs, the delay of second rotating body  23  relative to first rotating body  21  is small because rotation torque is small. On the other hand, when the vehicle is stopping, the delay of second rotating body  23  becomes large because the rotation torque is large. 
     According to the rotation of first rotating body  21 , first magnet  22  is rotated. Then, after a slight delay from the rotation of first rotating body  21 , second rotating body  23  is also rotated. First magnetism detecting element  28  detects magnetic variations of the N-poles and S-poles of first magnet  22  via first magnetic body  24 , second magnetic body  25 , and third magnetic body  26 , and output them as a torque detection signal to control circuit  33  and an electronic circuit of a vehicle. 
       FIG. 3  is a view for illustrating relation between first magnet  22  and third magnetic bodies  26  when steering is stationary. When steering is not turned and is in a neutral position, and an automobile travels straight, each of centers of the plurality of third magnetic bodies  26  faces each of dividing lines between the N-poles and S-poles, which are arranged alternately and adjacently on the outer periphery of first magnet  22 , with a predetermined space. Accordingly, magnetism from the N-pole to the S-pole is in a balanced state. 
     Therefore, since a magnetic flux is not generated between first magnetic body  24  and second magnetic body  25  on the outside of the plurality of third magnetic bodies  26 , the magnetism detected by first magnetism detecting element  28  is 0. 
       FIG. 4  is a view for illustrating the relation between first magnet  22  and third magnetic bodies  26  when the steering is turned. In a state in which the steering is turned to right or left, first magnet  22  is rotated, and each of the centers of third magnetic bodies  26  is displaced relative to each of the division lines of the N-poles and S-poles of first magnet  22 , magnet  22  generates a magnetic flux as a closed magnetic circuit from the N-pole to the S-pole on third magnetic bodies  26 . 
     Furthermore, at the same time, first magnet  22  generates a magnetic flux from the N-pole to the S-pole, also in first magnetic body  24  and second magnetic body  25 . Consequently, first magnetism detecting element  28  detects the magnetism, and a predetermined voltage waveform corresponding to the strength and weakness of the magnetism is output as a torque detection signal to control circuit  33  and the electronic circuit of a vehicle. 
     At this time, when the rotation torque is small, the delay of second rotating body  23  relative to first rotating body  21 , which is expressed by an angle, is about 1°. On the other hand, when the rotation torque is large, the delay expressed by an angle is about 4°. The magnetism detected by first magnetism detecting element  28  is weak when the delay of rotation of second rotating body  23  to which third magnetic bodies  26  are fixed is small relative to first rotating body  21  to which first magnet  22  is fixed, and the magnetism is stronger when the delay of the rotation is large. 
     Then, control circuit  33  calculates the rotation torque of first rotating body  21  (that is, the rotation torque of the steering) from the strength and weakness of the magnetism of first magnetism detecting element  28 , which is detected via first magnetic body  24 , second magnetic body  25 , and third magnetic body  26 ; and outputs the calculated torque as a rotation torque signal to the electronic circuit of a vehicle main body. 
     Furthermore, according to the rotation of first rotating body  21 , first detecting body  29  and second detecting body  30  are rotated. 
     Then, according to the rotation of first detecting body  29 , second magnet  31 A is rotated. Furthermore, according to the rotation of second detecting body  30 , third magnet  32 A is rotated. Second magnetism detecting element  31 B detects magnetic variation of second magnet  31 A. Third magnetism detecting element  32 B detects magnetic variation of third magnet  32 A. The magnetic variation detected by second magnetism detecting element  31 B is input as sine wave, cosine wave, or a saw-tooth angle detection signal (first angle detection signal) into control circuit  33 . Furthermore, the magnetic variation detected by third magnetism detecting element  32 B is input as sine wave, cosine wave, or a saw-tooth angle detection signal (second angle detection signal) into control circuit  33 . 
     The number of cogs of spur gear  29 A of first detecting body  29  is different from that of spur gear  30 A of second detecting body  30 . Therefore, the first angle detection signal output from second magnetism detecting element  31 B and the second angle detection signal output from third magnetism detecting element  32 B are different from each other in terms of inclining angles and shapes of waveforms, so that the signals have a phase difference. 
     Control circuit  33  calculates a rotation angle of first rotating body  21  (that is, a rotation angle of steering) by carrying out a predetermined arithmetic operation based on the two different angle detection signals from first detecting body  29  and second detecting body  30  and the numbers of cogs of the respective spur gears. Then, control circuit  33  outputs a rotation angle signal to an electronic circuit of an automobile main body. The electronic circuit arithmetically operates the rotation angle signal and the above-mentioned control circuit arithmetically operates the rotation torque signal so as to control power steering, a brake, or the like. 
     In other words, the electronic circuit controls the steering in response to a running state or a stopping state of a vehicle. For example, when the rotation torque of the steering is small during running of the vehicle, the electronic circuit loosens the effectiveness of a power steering device so that the steering is turned with large force to some extent. When the rotation torque of the steering is large during stop of the vehicle, the electronic circuit strengthens the effectiveness of the power steering device so that the steering can be turned even with small force. 
     Alternatively, controls of the brake or the like are carried out in response to the turning of the steering based on the rotation angle signal from control circuit  33 . For example, control circuit  33  makes the effectiveness of the brake intermittent when the steering is turned by a large amount, while it makes the effectiveness of the brake constant when the steering is turned by a small amount. 
     Then, in this embodiment, a rotation torque signal and a rotation angle signal of first rotating body  21  are output from control circuit  33  to an electronic circuit of a vehicle via a plurality of terminals  35 . Furthermore, the torque detection signal is output also from first magnetism detecting element  28  via terminals  35 . Therefore, even if failure such as breakdown occurs in control circuit  33 , the electronic circuit can detect the failure. 
     That is to say, when the steering is turned in a state in which failure such as breakdown occurs in control circuit  33 , first rotating body  21 , second rotating body  23 , first detecting body  29  and second detecting body  30  are rotated together with the steering. In this case, a rotation torque signal or a rotation angle signal is not output from control circuit  33 , but a torque detection signal is output to the electronic circuit from first magnetism detecting element  28  via terminals  35 . Therefore, the electronic circuit can detect failure in control circuit  33  based on the torque detection signal. 
     In other words, when a rotation torque signal or a rotation angle signal is not output from control circuit  33  but a torque detection signal is output from first magnetism detecting element  28 , the electronic circuit determines that failure occurs in control circuit  33 . Furthermore, when a rotation torque signal and a rotation angle signal are not output from control circuit  33 , and also a torque detection signal is not output from first magnetism detecting element  28 , the electronic circuit determines that a steering is not turned. 
     Furthermore, a plurality of first magnetism detecting elements  28  are provided between first magnetic body  24  and second magnetic body  25 , and the plurality of first magnetic elements  28  detect magnetism of first magnet  22 . Thereby, when damage, breakdown, or the like, occurs in one of first magnetism detecting elements  28 , control circuit  33  can detect the breakdown or the like. 
     In the above description, a configuration is described in which a rotation torque signal and a rotation angle signal are output from control circuit  33 , and a torque detection signal is output from first magnetism detecting element  28 . However, a configuration may be employed in which a first angle detection signal or a second angle detection signal is output to the electronic circuit of a vehicle from second magnetism detecting element  31 B or third magnetism detecting element  32 B via terminals  35 , thereby allowing the electronic circuit to sense failure of control circuit  33 . 
     Furthermore, this embodiment describes a configuration in which first rotating body  21  and first detecting body  29  mesh with each other, and first detecting body  29  and second detecting body  30  mesh with each other. However, both first detecting body  29  and second detecting body  30  may be allowed to mesh with first rotating body  21 . Alternatively, first detecting body  29  and second detecting body  30  are allowed to mesh with each other, and only one of them may be allowed to mesh with first rotating body  21 . In addition, second rotating body  23  may be provided with a spur gear with which first detecting body  29  and second detecting body  30  may be allowed to mesh. Furthermore, a configuration is not limited to the configuration in which first rotating body  21  and first detecting body  29  mesh with each other, and first detecting body  29  and second detecting body  30  mesh with each other. Any configurations may be employed as long as first rotating body  21 , first detecting body  29 , and second detecting body  30  are rotated together with each other. In addition, second rotating body  23 , first detecting body  29 , and second detecting body  30  may rotate together with each other. The rotating together includes rotating without having a contact portion. For example, as in first rotating body  21  and second rotating body  23 , a configuration in which rotation is carried out via connecting body  50  or the like may be employed. Note here that the rotating together other than meshing includes a configuration in which rotation is carried out via, for example, a rotation belt. 
     In this way, in accordance with this embodiment, the rotation torque signal or the rotation angle signal are output from control circuit  33 , and, at the same time, at least one of the torque detection signal and the angle detection signal is output from at least one of first magnetism detecting element  28 , second magnetism detecting element  31 B, and third magnetism detecting element  32 B. Thus, in addition to the rotation torque signal and the rotation angle signal from control circuit  33 , the torque detection signal from first magnetism detecting element  28 , or the angle detection signal from second magnetism detecting element  31 B and third magnetism detecting element  32 B is also output to the electronic circuit of a vehicle. Therefore, even if failure such as breakdown occurs in control circuit  33 , failure can be sensed based on the torque detection signal from first magnetism detecting element  28 , or the angle detection signal from second magnetism detecting element  31 B and third magnetism detecting element  32 B. As a result, the rotation angle and torque detection device of this embodiment enables a rotation angle and rotation torque to be detected reliably with a simple configuration without necessity of providing, for example, a new sensor. 
     A rotation angle and torque detection device in accordance with this embodiment has an advantageous effect that a rotation angle and rotation torque can be detected reliably with a simple configuration, and is mainly useful in detection of a rotation angle or rotation torque for a steering of an automobile.