Rotation Angle Detection Device

Abstract

To provide a rotation angle detection device having a small installation space that is capable of detecting an absolute angle of a shaft over a plurality of rotations.SOLUTION: A rotation angle detection device 2 includes: a target 31 integrally rotating in unison with a steering shaft 11; a driven gear 33 rotating at a rotational speed different from the steering shaft 11 as the steering shaft 11 rotates; a first sensor 35 whose output signal changes as the target 31 approaches; a second sensor 36 detecting a rotation angle within one rotation of the driven gear 33; and a computing part 4 which calculates an absolute angle of the steering shaft 11 on the basis of the output signal of the first sensor 35 and a rotation angle of the driven gear 33. The output signal of the first sensor 35 changes at a cycle different from a rotation cycle of the driven gear 33. The computing part 4 detects the absolute angle of the steering shaft 11 at that time from the rotation angle of the driven gear 33 when the output signal of the first sensor 35 changes.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a rotation angle detection device that detects the absolute angle of a rotating shaft over multiple rotations. [Background technology]

[0002] A rotation angle detection device described in Patent Document 1 is known as a device for detecting the rotation angle of a steering shaft connected to a steering member of a vehicle. This rotation angle detection device includes a main gear fixed to the steering shaft, a first gear and a second gear that rotate in mesh with the main gear, a magnet attached to the first gear, a magnet attached to the second gear, a first magnetic detection element that detects the magnetic field of the magnet attached to the first gear, and a second magnetic detection element that detects the magnetic field of the magnet attached to the second gear. The first gear and the second gear have different pitch circle diameters and numbers of teeth, and rotate at different speeds as the steering shaft rotates. As a result, the relative rotation angle relationship between the first gear and the second gear changes depending on the rotation speed of the steering shaft, making it possible to detect the absolute angle of the steering shaft, which rotates multiple times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-56078 Summary of the Invention [Problem to be solved by the invention]

[0004] The rotation angle detection device described in Patent Document 1 requires a large installation space because the first gear and the second gear are arranged on the outer periphery of the shaft whose rotation angle is to be detected. In particular, when the rotation angle detection device described in Patent Document 1 is mounted on a vehicle and used to detect the rotation angle of a steering shaft, the large installation space may cause problems in mounting the device on the vehicle.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotation angle detection device that requires a small installation space. Another object of the present invention is to provide a rotation angle detection device that can be manufactured at low cost. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides Connected to the vehicle's steering member Rotating relative to a non-rotating member Steering A rotation angle detection device for detecting an absolute angle of a shaft over multiple rotations, Steering At least one target that rotates together with the shaft; Steering As the shaft rotates, Steering a rotating member that rotates at a different rotation speed from the shaft; a first sensor whose output signal changes when the target approaches; a second sensor that detects the rotation angle of the rotating member within one rotation; and a second sensor that detects the rotation angle of the rotating member based on the output signal of the first sensor and the rotation angle of the rotating member detected by the second sensor. Steering a calculation unit that calculates the absolute angle of the shaft, Steering When the shaft rotates, the output signal of the first sensor changes at a period different from the rotation period of the rotating member, and the calculation unit after the start switch of the vehicle is turned on, waiting for a change in the output signal of the first sensor; The rotation angle of the rotary member when the output signal of the first sensor changes The rotation speed of the steering shaft is calculated based on the rotation speed and the rotation angle of the rotating member. The aforementioned Steering Detecting the absolute angle of the shaft and thereafter, determining whether or not the output signal of the first sensor has changed at each predetermined control cycle, determining the rotation speed of the steering shaft based on the rotation angle of the rotating member when the output signal of the first sensor has changed, and detecting the absolute angle of the steering shaft from the determined rotation speed and the rotation angle of the rotating member. A rotation angle detection device is provided. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce the installation space of the rotation angle detection device and to reduce the cost of the rotation angle detection device. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a schematic diagram of a vehicle steering device in which a steering angle is detected by a rotation angle detection device according to a first embodiment of the present invention. [Figure 2] 2 is a structural diagram showing a sensor unit of the rotation angle detection device together with a steering shaft and a mounting stay as a non-rotating member. FIG. [Figure 3] FIG. 2 is a perspective view showing a sensor unit. [Figure 4] FIG. [Figure 5] FIG. 5 is an exploded perspective view of the sensor unit as seen from a different direction from FIG. 4. [Figure 6] 1A is a diagram showing the drive gear as viewed from its axial direction, and FIG. 1B is a diagram showing the driven gear together with the magnet as viewed from its axial direction. [Figure 7] 6 is a graph showing the rotation angle of the driven gear and the output signal of the first sensor in the detection range of the absolute angle of the steering shaft. [Figure 8] 10 is a flowchart illustrating an example of processing executed by a CPU of a calculation unit. [Figure 9] FIG. 10 is a perspective view showing a sensor unit and a steering shaft according to a second embodiment of the present invention. [Figure 10] FIG. 2 is a configuration diagram showing the inside of a sensor unit together with a cross section of a steering shaft. [Figure 11] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] 1 is a schematic diagram of a vehicle steering device 1 in which a steering angle is detected by a rotation angle detection device 2 according to a first embodiment of the present invention. The vehicle steering device 1 includes a steering wheel 10 which is a steering member operated by a driver, a steering shaft 11 connected to the steering wheel 10, a rack shaft 12 which is supported so as to be movable forward and backward along the vehicle width direction, a pair of ball joints 13 attached to both ends of the rack shaft 12, a pair of tie rods 14 which are each connected to the pair of ball joints 13 so as to be able to swing to the rack shaft 12, and a steering assist device 15 which applies a steering assist force to the steering shaft 11 to assist the steering operation of the steering wheel 10.

[0010] The steering shaft 11 is a shaft whose rotation angle is to be detected by the rotation angle detection device 2. The steering assist device 15 applies a steering assist force to the steering shaft 11 according to the rotation angle (steering angle) detected by the rotation angle detection device 2 and the steering torque applied to the steering wheel 10.

[0011] One longitudinal end of the steering shaft 11 is connected to the steering wheel 10, and the other longitudinal end is provided with a pinion gear 111. The rack shaft 12 is provided with a rack gear 121 that meshes with the pinion gear 111. When the steering wheel 10 is steered, the steering shaft 11 rotates together with the steering wheel 10, and the rack shaft 12 moves in the vehicle width direction. As a result, the left and right steered wheels 16, 17 are steered.

[0012] The rotation angle detection device 2 has a sensor unit 3 attached near the steering shaft 11, a calculation unit 4, and a cable 20 connecting the sensor unit 3 and the calculation unit 4. The calculation unit 4 has a CPU (Central Processing Unit) 40 and a storage unit 400 configured with a non-volatile memory. The storage unit 400 stores a program 401 executed by the CPU 40 and related information 402, which will be described later.

[0013] Fig. 2 is a configuration diagram showing the sensor unit 3 of the rotation angle detection device 2 together with the steering shaft 11 and a mounting stay 18 as a non-rotating member. Fig. 3 is a perspective view showing the sensor unit 3. Fig. 4 is an exploded perspective view of the sensor unit 3. Fig. 5 is an exploded perspective view of the sensor unit 3 as seen from a different direction than that of Fig. 4.

[0014] The sensor unit 3 includes a target 31 that rotates integrally with the steering shaft 11, a drive gear 32 that is provided on the outer periphery of the steering shaft 11 and rotates integrally with the steering shaft 11, a driven gear 33 that is a rotating member that rotates at a different rotational speed from the steering shaft 11 as the steering shaft 11 rotates, a magnet 34 fixed to the center of the driven gear 33, a first sensor 35 whose output signal changes when the target 31 approaches, a second sensor 36 that detects the rotation angle of the driven gear 33 within one rotation, a substrate 37 on which the first sensor 35 and the second sensor 36 are mounted, a terminal unit 38 that has a plurality of connector pins 381 to 384, and a case member 39 that is fixed to the mounting stay 18 by a bolt 19.

[0015] The mounting stay 18 is, for example, a part of a steering member of the vehicle body, but the mounting object of the case member 39 is not limited to this, and the case member 39 can be mounted to various non-rotating members that do not rotate relative to the vehicle body. The rotation angle detection device 2 detects the absolute angle of the steering shaft 11 over multiple rotations. In this embodiment, the rotation angle of the steering shaft 11 is set to 0° when the steering wheel 10 is in the neutral position (a position where the vehicle travels straight), and the rotation angle detection device 2 can detect the absolute angle of the steering shaft 11 within a range (a range from -1080° to 1080°) in which the steering shaft 11 rotates three times clockwise and three times counterclockwise together with the steering wheel 10.

[0016] In this embodiment, as shown in Fig. 2, two targets 31 are fixed to the outer peripheral surface 11a of the steering shaft 11 at equal intervals in the circumferential direction. In other words, the two targets 31 are fixed 180° apart around the rotation axis O of the steering shaft 11. However, the number of targets 31 is not limited to this, and may be three or more, or may be just one. In other words, it is sufficient that at least one target 31 is fixed to the steering shaft 11.

[0017] In this embodiment, the target 31 is a two-pole magnet in which the surface 31a on the outer peripheral surface 11a side of the steering shaft 11 and the opposite surface 31b have different magnetic properties, and the first sensor 35 is a magnetic field switch that outputs a pulse signal when the target 31 approaches. The target 31 may be, for example, a ferrite, neodymium, samarium cobalt, or alnico magnet. The first sensor 35 may be, for example, a Hall element. Note that the target 31 may also be a ring magnet with multiple magnetic poles that is fitted around the steering shaft 11.

[0018] FIG. 6(a) is a structural diagram of the drive gear 32 as viewed from its axial direction. FIG. 6(b) is a structural diagram of the driven gear 33 as viewed from its axial direction together with the magnet 34. The drive gear 32 and the driven gear 33 are made of a non-magnetic material, more specifically, injection-molded resin. The driven gear 33 meshes with the drive gear 32 and rotates at a faster rotational speed than the drive gear 32 in conjunction with the rotation of the steering shaft 11. The driven gear 33 has fewer teeth than the drive gear 32, and the pitch circle diameter P2 of the driven gear 33 is less than half the pitch circle diameter P1 of the drive gear 32. In this embodiment, the drive gear 32 has 55 teeth, the driven gear 33 has 26 teeth, and the gear ratio between the drive gear 32 and the driven gear 33 (the number of teeth of the drive gear 32 divided by the number of teeth of the driven gear 33) is approximately 2.1.

[0019] The magnet 34 is a two-pole magnet with an N pole 34N and an S pole 34S aligned in the diametric direction of the driven gear 33, and is made of, for example, a ferrite, neodymium, samarium cobalt, or alnico magnet. The second sensor 36 is a magnetic field sensor capable of detecting the strength of magnetic fields in two directions perpendicular to the rotation axis of the driven gear 33, and is disposed opposite the magnet 34. The second sensor 36 may be, for example, a Hall element, a GMR (Giant Magneto Resistive effect) element, or a TMR (Tunneling Magneto Resistive) element.

[0020] 5, when the rotation axis of the driven gear 33 is the Z axis and the two directions of the magnetic field detectable by the second sensor 36 are the X axis and the Y axis, the X axis, the Y axis, and the Z axis are perpendicular to one another. The calculation unit 4 acquires from the second sensor 36 the detection results of the direction and strength of the magnetic field in the X axis direction and the Y axis direction generated by the magnet 34, and is able to calculate the rotation angle of the driven gear 33 within one rotation. The calculation unit 4 calculates the rotation angle of the driven gear 33 by setting the angle of the driven gear 33 when the steering wheel 10 is in the neutral position to 0°.

[0021] The substrate 37 is a printed circuit board whose base material is a flat dielectric material such as glass epoxy, and is housed in a case member 39. The terminal unit 38 has first to fourth connector pins 381 to 384 connected to the substrate 37 and a fixing member 385 made of resin. The first to fourth connector pins 381 to 384 are fixed to the fixing member 385 and are aligned in a row along the edge of the substrate 37. The first to fourth connector pins 381 to 384 are connected to the first sensor 35 and the second sensor 36 by a wiring pattern (not shown) formed on the substrate 37. The first connector pin 381 is, for example, a power pin, and the second connector pin 382 is, for example, an electrically grounded ground pin. The third connector pin 383 is, for example, a signal pin that transmits an output signal of the first sensor 35 to the calculation unit 4, and the fourth connector pin 384 is, for example, a signal pin that transmits an output signal of the second sensor 36 to the calculation unit 4.

[0022] The case member 39 has a resin case body 391 and a case lid 392, which are joined together by, for example, adhesive bonding or ultrasonic welding. The case body 391 has a recess 391a formed therein into which a boss 331 provided at the center of the driven gear 33 fits. The driven gear 33 is rotatably supported relative to the case member 39 by fitting the boss 331 into the recess 391a.

[0023] The case main body 391 is also formed with a connector housing portion 391b and a flange portion 391c. The connector housing portion 391b, together with the terminal portion 38, constitutes a connector portion 390 of the case member 39. The connector portion of the cable 20 is fitted into the connector housing portion 391b, and the conductor wires of the cable 20 are electrically connected to the first to fourth connector pins 381 to 384 of the terminal portion 38. The flange portion 391c is formed with a bolt insertion hole 391d through which a bolt 19 for fixing the case member 39 to the mounting stay 18 is inserted. The bolt insertion hole 391d is reinforced by a metal collar 391e.

[0024] The case cover 392 is formed with a slit-shaped opening 392a for allowing a portion of the driven gear 33 to protrude, and a window 392b for accommodating a portion of the first sensor 35. A portion of the driven gear 33 in the circumferential direction protrudes from the opening 392a to the outside of the case member 39, and this protruding portion meshes with the drive gear 32. The first sensor 35 has a portion accommodated in the window 392b, thereby shortening the minimum distance to the target 31, thereby improving the detection accuracy when detecting the approach of the target 31.

[0025] The calculation unit 4 calculates the absolute angle of the steering shaft 11 within a predetermined angle range (from −1080° to 1080° in this embodiment) based on the output signal of the first sensor 35 and the rotation angle of the driven gear 33 detected by the second sensor 36. The absolute angle of the steering shaft 11 can be found by adding a value obtained by dividing the rotation angle of the driven gear 33 within one rotation detected by the second sensor 36 by the gear ratio to the product of the number of rotations of the steering shaft 11 since the steering wheel 10 was in the neutral position multiplied by 360.

[0026] As described above, the drive gear 32 and the driven gear 33 have different numbers of teeth, so when the steering shaft 11 rotates, the output signal of the first sensor 35 changes at a cycle different from the rotation cycle of the driven gear 33. Furthermore, the gear ratio between the drive gear 32 and the driven gear 33 is a non-integer multiple rather than an integer multiple, so that the rotation angle of the driven gear 33 when the output signal of the first sensor 35 changes is different for each of the first to third rotations clockwise and the first to third rotations counterclockwise from the neutral position of the steering wheel 10. Therefore, the rotation speed of the steering shaft 11 at that time can be determined from the rotation angle of the driven gear 33 detected by the second sensor 36 when the output signal of the first sensor 35 changes.

[0027] Here, the number of rotations of the steering shaft 11 is a positive or negative integer value, and is set to 1 when the steering shaft 11 has completed one rotation (360° rotation) in the right direction from the neutral position of the steering wheel 10, and is set to 2 when the steering shaft 11 has completed two rotations (720° rotation) in the same direction. Also, it is set to -1 when the steering shaft 11 has completed one rotation (-360° rotation) in the left direction from the neutral position of the steering wheel 10, and is set to -2 when the steering shaft 11 has completed two rotations (-720° rotation) in the same direction.

[0028] The calculation unit 4 refers to relationship information 402 stored in the storage unit 400 based on the rotation angle of the driven gear 33 when the output signal of the first sensor 35 changes, and detects the absolute angle of the steering shaft 11 at that time. The relationship information 402 indicates information on the rotation angle of the driven gear 33 when the output signal of the first sensor 35 changes for each of the first to third rotations of the steering wheel 10 to the right and the first to third rotations to the left from the neutral position.

[0029] Here, the conditions for the gear ratio and the angular interval of the targets 31 that enable the calculation unit 4 to calculate the absolute angle of the steering shaft 11 within a predetermined angle range will be described with reference to equations (1) to (3). In equations (1) to (3), α is the gear ratio between the drive gear 32 and the driven gear 33, Ψ is the angular interval of the targets 31 in the circumferential direction of the steering shaft 11 (180° in this embodiment), and N is the number of rotations of the steering shaft 11 (3 in this embodiment) when the rotation angle of the steering shaft 11 ranges from 0° to the maximum absolute value within the predetermined angle range (1080° in this embodiment).

[0030] The amount of rotation R of the driven gear 33 when the steering shaft 11 rotates n times from the neutral position of the steering wheel 10 is given by equation (1).

number

[0031] The angular deviation Δθ from the neutral position of the output signal of the first sensor 35 relative to the rotation amount R at this time is given by equation (2).

number

[0032] In order to detect the absolute angle of the steering shaft 11 from the output signal of the first sensor 35, this Δθ needs to be within the range of one rotation of the driven gear 33 (within the range of ±180°). Therefore, α, Ψ, and N need to be set so as to satisfy equation (3).

number

[0033] 7 is a graph showing the rotation angle of the driven gear 33 and the output signal of the first sensor 35 in the detection range (-1080° to 1080°) of the absolute angle of the steering shaft 11 in this embodiment. The output signal of the first sensor 35 is set to 1 when the first sensor 35 and the target 31 are in close proximity to each other, and set to 0 when they are not in close proximity to each other.

[0034] As shown in this graph, the rotation angle of driven gear 33 when the output signal of first sensor 35 rises from 0 to 1 differs depending on the rotation speed of steering shaft 11. In the example shown in Fig. 7, the rotation angle of driven gear 33 when the output signal of first sensor 35 rises from 0 to 1 increases as the rotation angle of steering shaft 11 increases in a range where the rotation angle of steering shaft 11 is greater than 0, and decreases (closer to -180°) as the rotation angle of steering shaft 11 decreases (closer to -1080°) in a range where the rotation angle of steering shaft 11 is smaller than 0. This enables calculation unit 4 to calculate the absolute angle of steering shaft 11.

[0035] In this embodiment, as shown in Fig. 7, the output signal of the first sensor 35 changes near the neutral position of the steering wheel 10. In the example shown in Fig. 7, when the steering wheel 10 is in the neutral position, the output signal of the first sensor 35 is 1. When the steering wheel 10 is steered to the left or right from the neutral position, the output signal of the first sensor 35 changes to 0, thereby making it possible to detect the absolute angle of the steering shaft 11 at that time. This makes it possible to quickly detect the absolute angle of the steering shaft 11 after the start switch (e.g., ignition switch) of the vehicle is turned on to supply power to the calculation unit 4 and the sensor unit 3 and the vehicle starts to travel. It is desirable that the output signal of the first sensor 35 changes at least once between 0° and 90° as the absolute value of the steering angle.

[0036] Furthermore, in this embodiment, as shown in FIG. 7, the output signal of the first sensor 35 changes at least once during one rotation of the driven gear 33. Therefore, even if the start switch of the vehicle is turned on while the steering wheel 10 is rotated largely to the right or left and the vehicle starts to travel, it is possible to prevent the vehicle from traveling a long distance without being able to detect the absolute angle of the steering shaft 11.

[0037] 8 is a flowchart showing an example of processing executed by the CPU 40 of the calculation unit 4 after the vehicle start switch is turned on. In the processing shown in this flowchart, the CPU 40 first waits for a change in the output signal of the first sensor 35 (step S1). When the output signal of the first sensor 35 changes, the CPU 40 calculates the rotation angle of the driven gear 33 at that time based on the detection result of the second sensor 36 (step S2). Then, the CPU 40 determines the rotation speed of the steering shaft 11 based on the determined rotation angle of the driven gear 33 by referring to the relationship information 402 (step S3). The CPU 40 then detects the absolute angle of the steering shaft 11 from the determined rotation speed and the rotation angle of the driven gear 33 (step S4). The CPU 40 then outputs information on the detection result of the absolute angle of the steering shaft 11 to the outside (step S5).

[0038] After this, the CPU 40 determines whether the output signal of the first sensor 35 has changed at each predetermined control cycle (step S6), and if the output signal of the first sensor 35 has changed since the previous control cycle, executes steps S7 to S10 similar to the processes of steps S2 to S5. On the other hand, if the output signal of the first sensor 35 has not changed since the previous control cycle, the CPU 40 calculates the rotation angle of the driven gear 33 based on the detection result of the second sensor 36 (step S11), detects the absolute angle of the steering shaft 11 from the latest rotation speed of the steering shaft 11 calculated in the previous control cycle or an earlier control cycle and the rotation angle of the driven gear 33 calculated in step S11 (step S12), and outputs information on the detection result of the absolute angle of the steering shaft 11 to the outside (step S13).

[0039] The change in the output signal of the first sensor 35 in the processing of steps S1 and S6 may be a rising edge from 0 to 1, a falling edge from 1 to 0, or both. The time interval (the above-mentioned control cycle) during which the CPU 40 executes the processing of step S1 or step S6 is set shorter than the pulse width of the output signal of the first sensor 35 when the steering wheel 10 is quickly rotated. The output destination of the detection result of the absolute angle of the steering shaft 11 in the processing of steps S5, S10, and S13 is, for example, the steering assist device 15, but is not limited to this, and may also be, for example, a stability control device that performs control to stabilize the behavior of the vehicle.

[0040] According to the first embodiment described above, it is possible to reduce the installation space compared to the conventional rotation angle detection device described above, in which the first gear and the second gear are arranged on the outer periphery of the shaft. Furthermore, since only one driven gear 33 and one second sensor 36 are required, it is also possible to reduce costs.

[0041] [Second embodiment] Next, a rotation angle detection device according to a second embodiment of the present invention will be described. In the rotation angle detection device according to the second embodiment, the configuration of a sensor unit 3A is different from that of the sensor unit 3 of the first embodiment. Hereinafter, the configurations of this sensor unit 3A and a steering shaft 11A, which is a shaft whose rotation angle is to be detected, will be described with reference to FIGS. 9 to 11. In FIGS. 9 to 11, components that are common to those described in the first embodiment are assigned the same reference numerals as those in FIGS. 2 to 5, and redundant description will be omitted.

[0042] Fig. 9 is a perspective view showing a state in which the sensor unit 3A is attached to the steering shaft 11A. Fig. 10 is a configuration diagram showing the inside of the sensor unit 3A together with a cross section of the steering shaft 11A. Fig. 11 is an exploded perspective view of the sensor unit 3A.

[0043] In the first embodiment, the drive gear 32 was disposed outside the case member 39, but in this embodiment, the drive gear 32A is held in a case member 39A of the sensor unit 3A. The case member 39A has a case main body 391A and a case lid 392A, and the first sensor 35, the second sensor 36, and a circuit board 37 on which the terminal unit 38 is mounted, as well as the driven gear 33 are housed between the case main body 391A and the case lid 392A.

[0044] The drive gear 32A is made of, for example, resin, and integrally includes a ring-shaped base portion 321, a gear portion 322 provided on the outer periphery of the base portion 321, and a plurality of locking projections 323 provided on the inner periphery of the base portion 321. The base portion 321 and gear portion 322 of the drive gear 32A are housed in a drive gear housing portion 391f of the case main body 391A and a drive gear housing portion 392c of the case lid 392A. The drive gear housing portions 391f and 392c are each formed in an annular shape surrounding the steering shaft 11A.

[0045] The steering shaft 11A is formed with a plurality of engagement grooves 112 that engage with the plurality of locking protrusions 323 of the drive gear 32A, respectively, and the engagement of the locking protrusions 323 with the engagement grooves 112 prevents the drive gear 32A from rotating relative to the steering shaft 11A. The engagement grooves 112 extend parallel to the axial direction of the steering shaft 11A. When attaching the sensor unit 3A to the steering shaft 11A, the steering shaft 11A is inserted inside the drive gear accommodating portions 391f, 392c, and the plurality of locking protrusions 323 are engaged with the plurality of engagement grooves 112, respectively.

[0046] As in the first embodiment, output signals from the first sensor 35 and the second sensor 36 of the sensor unit 3A are sent to the calculation unit 4, and the absolute angle of the steering shaft 11A is detected based on these output signals. A window 392d for accommodating part of the second sensor 36 is formed in the case cover 392A at part of the circumferential direction of the drive gear accommodating portion 392c.

[0047] The second embodiment also provides the same effects as the first embodiment. In addition, since the drive gear 32A is held in the case member 39A of the sensor unit 3A, it is easy to attach the sensor unit 3A to the steering shaft 11A.

[0048] (Summary of the embodiment) Next, the technical ideas grasped from the first and second embodiments explained above will be described using the reference numerals and the like in each embodiment. However, the reference numerals in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0049] [1] A rotation angle detection device (2) for detecting the absolute angle of a shaft (steering shaft 11, 11A) rotating relative to a non-rotating member (mounting stay 18) over multiple rotations, comprising at least one target (31) that rotates integrally with the shaft (11, 11A), a rotating member (driven gear 33) that rotates at a rotation speed different from that of the shaft (11, 11A) in accordance with the rotation of the shaft (11, 11A), a first sensor (35) whose output signal changes when the target (31) approaches, and a second sensor ( a calculation unit (4) that calculates the absolute angle of the shaft (11, 11A) based on the output signal of the first sensor (35) and the rotation angle of the rotating member (33) detected by the second sensor (36), wherein the output signal of the first sensor (35) changes at a period different from the rotation period of the rotating member (33) when the shaft (11, 11A) rotates, and the calculation unit (4) detects the absolute angle of the shaft (11, 11A) at that time based on the rotation angle of the rotating member (33) when the output signal of the first sensor (35) changes.

[0050] [2] The rotation angle detection device (2) described in [1] above, which has a drive gear (32) provided on the outer periphery of the shaft (11, 11A) and rotating integrally with the shaft (11, 11A), and the rotating member (33) is a driven gear (33) that rotates in mesh with the drive gear (32).

[0051] [3] The rotation angle detection device (2) according to the above [2], wherein the pitch circle diameter (P2) of the driven gear (33) is smaller than half the pitch circle diameter (P1) of the drive gear (32).

[0052] [4] The rotation angle detection device (2) according to the above [2] or [3], further comprising a case member (39, 39A) fixed to the non-rotating member (18), a portion of the rotating member (33) protruding from an opening (392a) formed in the case member (39, 39A), and the protruding portion of the rotating member (33) meshing with the drive gear (32).

[0053] [5] The rotation angle detection device (2) described in [1] above, wherein the target (31) is a magnet fixed to the shaft (11, 11A), and the first sensor (35) is a magnetic field switch that outputs a pulse signal when the target (31) approaches.

[0054] [6] The rotation angle detection device (2) according to the above [5], further comprising a case member (39, 39A) fixed to the non-rotating member (18), and a portion of the first sensor (35) being housed in a window portion (392b) formed in the case member (39, 39A).

[0055] [7] The rotation angle detection device (2) described in [1] above, wherein a magnet (34) is fixed to the center of the rotating member (33), and the second sensor (36) is a magnetic field sensor capable of detecting the strength of magnetic fields in two directions perpendicular to the rotation axis of the rotating member (33).

[0056] [8] The rotation angle detection device (2) described in [1] above, wherein the shaft (11, 11A) is a steering shaft connected to a steering member (steering wheel 10) of a vehicle, and the output signal of the first sensor (35) changes near the neutral position of the steering member (10).

[0057] Although the first and second embodiments of the present invention have been described above, the above-described embodiments do not limit the scope of the invention as claimed. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be appropriately modified and implemented without departing from the spirit of the invention, and can be modified, for example, as follows:

[0058] In the above embodiment, the case has been described where the driven gear 33 as a rotating member rotates by meshing with the drive gear 32, but the rotating member is not limited to this and may be, for example, a member driven by a belt that rotates at a rotational speed different from that of the steering shaft 11 in conjunction with the rotation of the steering shaft 11. Furthermore, the shaft whose rotation angle is to be detected is not limited to the steering shaft 11, and various shafts for vehicles or industrial machines, for example, may be used as the rotation angle detection target.

[0059] Furthermore, in the above embodiment, the target 31 is a two-pole magnet, but the present invention is not limited to this. The target 31 may be, for example, a metal protrusion, and the first sensor 35 may be, for example, a capacitance-type proximity switch. In other words, the first sensor 35 may be, for example, an optical sensor, as long as the output signal changes when the target 31 passes between the steering shaft 11 and the first sensor 35 due to the rotation of the steering shaft 11. If the first sensor 35 is an optical sensor, the target 31 may be, for example, a reflective material. [Explanation of symbols]

[0060] 11, 11A... Steering shaft (shaft) 18... Mounting stay (non-rotating member) 2...Rotation angle detection device 3, 3A...Sensor section 32...Drive gear 33...Driven gear 34...Magnet 35...First sensor 36... Second sensor 39, 39A... Case member 392a...Opening 392b...Window 4...Calculation section P1, P2...Pitch circle diameter

Claims

1. A rotation angle detection device that detects the absolute angle of a steering shaft that is connected to a steering member of a vehicle and rotates relative to a non-rotating member over multiple rotations, comprising: At least one target that rotates integrally with the steering shaft; a rotating member that rotates at a rotational speed different from that of the steering shaft in accordance with the rotation of the steering shaft; a first sensor whose output signal changes when the target approaches; a second sensor for detecting a rotation angle of the rotary member within one rotation; a calculation unit that calculates an absolute angle of the steering shaft based on the output signal of the first sensor and the rotation angle of the rotating member detected by the second sensor, When the steering shaft rotates, the output signal of the first sensor changes at a period different from the rotation period of the rotary member, the calculation unit waits for a change in the output signal of the first sensor after the start switch of the vehicle is turned on, determines the rotation speed of the steering shaft based on the rotation angle of the rotating member when the output signal of the first sensor changes, detects the absolute angle of the steering shaft from the determined rotation speed and the rotation angle of the rotating member, and thereafter determines whether or not the output signal of the first sensor has changed at each predetermined control cycle, determines the rotation speed of the steering shaft based on the rotation angle of the rotating member when the output signal of the first sensor changes, and detects the absolute angle of the steering shaft from the determined rotation speed and the rotation angle of the rotating member; Rotation angle detection device.

2. a drive gear provided on the outer periphery of the steering shaft and rotating integrally with the steering shaft; The rotating member is a driven gear that rotates in mesh with the drive gear. The rotation angle detection device according to claim 1 .

3. The pitch circle diameter of the driven gear is smaller than half the pitch circle diameter of the drive gear. The rotation angle detection device according to claim 2 .

4. a case member fixed to the non-rotating member; a part of the rotating member protruding from an opening formed in the case member, and the protruding part of the rotating member meshes with the drive gear; 4. The rotation angle detection device according to claim 2 or 3.

5. the target is a magnet fixed to the steering shaft, the first sensor is a magnetic field switch that outputs a pulse signal when the target approaches; The rotation angle detection device according to claim 1 .

6. a case member fixed to the non-rotating member; a window formed in the case member, the window portion housing a portion of the first sensor; The rotation angle detection device according to claim 5 .

7. A magnet is fixed to the center of the rotating member, the second sensor is a magnetic field sensor capable of detecting the strength of a magnetic field in two directions perpendicular to the rotation axis of the rotating member; The rotation angle detection device according to claim 1 .

8. The output signal of the first sensor changes near the neutral position of the steering member. The rotation angle detection device according to claim 1 .

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