Rotation angle detection sensor

Abstract

The present invention provides a rotation angle detection sensor that eliminates the risk of attaching the magnet to the wrong magnet housing and ensures that the magnet is reliably attached to the predetermined position on the driven gear. [Solution] The system comprises a driving gear, two driven gears of the same shape mounted in opposite directions in the direction of rotation on a first plane parallel to the mounting reference plane, two magnets positioned at the midpoint in the direction of rotation of the driven gear on the rotation axis of the driven gear, and two magnetic sensors positioned on a second plane parallel to the mounting reference plane and different from the first plane. The driven gear comprises a shaft portion formed in a hollow cylindrical shape with the rotation axis as the center, and a magnet mounting portion having a bottom portion that protrudes in the direction of rotation from a position close to one end side from the midpoint of the inner wall surface of the shaft portion. The magnet mounting portion has a through hole centered on the rotation axis, and a notch with a chamfered corner is provided at the end of the through hole on the surface on one end side from the midpoint of the bottom portion, and a part of the magnetic sensor is inserted into the inside of the notch in a range where the notch and the magnetic sensor do not come into contact.

Description

Technical Field

[0001] The present invention relates to a rotation angle detection sensor that detects the rotation angle of a steering shaft or the like of a vehicle.

Background Art

[0002] In recent years, in vehicles such as automobiles, various systems for improving running stability, such as a vehicle stability control system and an electronically controlled suspension system, are installed. And in these systems, the steering angle of the steering is acquired as one of the vehicle attitude information, and the vehicle attitude is controlled to be in a stable state based on the attitude information. For this reason, a rotation angle detection sensor for detecting the rotation angle of the shaft is attached to the steering shaft.

[0003] As such a rotation angle detection device, in Patent Document 1, in order to reduce the manufacturing cost, while providing two driving gear portions having different numbers of teeth that rotate about the same axis, the numbers of teeth of the two driven gears are made the same, and a rotation angle detection device is proposed in which the two driven gears are respectively meshed with the two driving gear portions of the driving gear.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the two driven gears of the rotation angle detection device described in Patent Document 1 have magnet housings formed at both ends of the shaft portion, and the magnets are positioned by selecting the magnet housing according to the mounting direction of the driven gear. As a result, there is a risk of attaching the magnet to the opposite side of the designated magnet housing, and if the wrong magnet housing is used, the magnet will be attached out of position. Therefore, the present invention aims to provide a rotation angle detection sensor that eliminates the risk of the magnet being attached to the wrong magnet housing and that can reliably attach the magnet to a predetermined position on the driven gear. [Means for solving the problem]

[0006] The present invention provides the following configuration as a means for solving the above-mentioned problems. A rotation angle detection sensor comprising a driving gear having a large-diameter gear section and a small-diameter gear section, two driven gears meshing with the large-diameter gear section and the small-diameter gear section, two magnets attached to each of the driven gears, and two magnetic sensors for detecting the magnetism of each of the magnets, wherein the rotation axes of the driving gear and the driven gears are perpendicular to the mounting reference plane, the two driven gears are arranged on a first plane parallel to the mounting reference plane, and the two magnetic sensors are arranged on a second plane parallel to the mounting reference plane and different from the first plane, wherein the two driven gears are identical in shape and are mounted in opposite directions in the rotation axis direction, and the magnets are positioned on the rotation axis of the driven gear and at the midpoint position in the rotation axis direction of the driven gear.

[0007] With the above configuration, the relative position of the magnet to the mounting reference surface of the lower case remains unchanged regardless of the orientation of the driven gear in the rotation axis direction. For example, even if a driven gear intended for a large-diameter gear section with a magnet attached is installed as a driven gear for a small-diameter gear section, the installed driven gear for the large-diameter gear section can still function as a driven gear for the small-diameter gear section. The same applies in reverse. Therefore, the occurrence of defective products due to incorrect magnet placement can be eliminated. Furthermore, the same gear can be used for both the large-diameter gear section and the small-diameter gear section. Consequently, the number of parts can be reduced, thereby lowering manufacturing costs and parts management costs.

[0008] The driven gear has a cylindrical shaft portion centered on the rotation axis, and a flange portion that extends from the shaft portion in a disc shape and has gear teeth at its outer peripheral end, wherein the flange portion is provided at a position offset from the midpoint position of the shaft portion in the rotation axis direction, and the magnet may be positioned at the midpoint position of the shaft portion in the rotation axis direction. Furthermore, the flange portion of the driven gear may be positioned to engage with the large-diameter gear portion when mounted on the mounting reference surface with one side of the rotating shaft facing it, and to engage with the small-diameter gear portion when mounted on the mounting reference surface with the other side of the rotating shaft facing it. This configuration allows the position of the flange portion in the rotational axis direction to change by altering the mounting direction of the driven gear relative to the mounting reference surface of the lower case. Therefore, depending on the mounting direction of the driven gear, it is possible to select whether the driven gear engages with the large-diameter gear portion or the small-diameter gear portion.

[0009] The driven gear may be provided with the magnet mounting portion on only one side in the direction of rotation. By providing the magnet mounting portion on only one side of the driven gear, it becomes unnecessary to select the magnet mounting portion when attaching the magnet. Therefore, it is possible to reliably prevent attaching the magnet to the wrong magnet mounting portion.

[0010] The shape of the magnet is a ring, and it is magnetized such that different magnetic poles are arranged alternately along the circumferential direction of the ring. The magnet may be positioned inside or outside the shaft portion such that the center of the ring coincides with the rotation axis of the driven gear. By making the magnet a ring, the center of the ring can be easily positioned at the center of the shaft. Furthermore, the support shaft that supports the driven gear can be inserted through the opening in the magnet. This allows the support shaft to be made longer, thus providing stable support for the driven gear.

[0011] When viewed from the direction of the rotation axis, the outer or inner circumference of the magnet may be polygonal, and when viewed from the direction of the rotation axis, the inner surface of the shaft portion may be shaped to engage with the outer circumference of the magnet, or the outer surface of the shaft portion may be shaped to engage with the inner circumference of the magnet. This configuration makes it easy to stop the rotation of the magnet and position it relative to the driven gear. [Effects of the Invention]

[0012] In the rotation angle detection sensor of the present invention, the magnet is positioned on the rotation axis and at the midpoint in the rotation axis direction of the driven gear. Therefore, regardless of the orientation in which two driven gears of the same shape are mounted, the position of the magnet relative to the mounting reference surface remains unchanged. Consequently, there is no risk of mounting the magnet on the wrong side, and the rotation angle detection sensor can be provided that ensures the magnet is reliably mounted at the predetermined position on the driven gear. [Brief explanation of the drawing]

[0013] [Figure 1] This is a plan view showing the main parts of a rotation angle detection sensor according to an embodiment of the present invention. [Figure 2A] This is a cross-sectional view of a rotation angle detection sensor according to an embodiment of the present invention, shown along line AA in Figure 1. [Figure 2B] This is a cross-sectional view showing a magnified view of some of the components in Figure 2A. [Figure 3] This is a perspective view showing the main parts of a rotation angle detection sensor according to an embodiment of the present invention. [Figure 4A] It is a cross-sectional view of a part corresponding to FIG. 2A of the rotation angle detection sensor according to the reference example. [Figure 4B] It is a cross-sectional view showing an enlarged view of some members in FIG. 4A.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same members in each drawing are denoted by the same reference numerals, and the description will be omitted as appropriate. X - Y - Z coordinates are shown as reference coordinates in each figure.

[0015] FIG. 1 is a plan view showing a main part of the rotation angle detection sensor 1 according to the present embodiment. This figure shows a state in which the upper case (upper case 61) of the case 60 of the rotation angle detection sensor 1 is removed (see FIG. 2A). The rotation angle detection sensor 1 includes a driving gear 2 rotatably held in a case 60, driven gears 3A and 3B that rotate along with the driving gear 2, magnets 4A and 4B that rotate together with the driven gears 3A and 3B, and magnetic sensors 5A and 5B that detect the rotation of the magnets 4A and 4B. The lower case (lower case 62) has a mounting reference surface 6 for the driving gear 2 and the driven gears 3A and 3B, and the rotation axis 2S of the driving gear 2 and the rotation axes 3SA and 3SB of the driven gears 3A and 3B are orthogonal to this mounting reference surface 6.

[0016] The driving gear 2 has a large - diameter gear portion 21 and a small - diameter gear portion 22 around a cylinder formed of synthetic resin. The driving gear 2 rotates along with the rotation of a detected rotating body (not shown). Examples of the detected rotating body include a plurality of rotating shafts such as a steering shaft of a vehicle.

[0017] The large-diameter gear portion 21 and the small-diameter gear portion 22 have different numbers of teeth. Also, as will be described later, the driven gears 3A and 3B are the same parts except for their mounting directions. Therefore, as the driving gear 2 rotates, the rotations generated in the driven gear 3A meshing with the large-diameter gear portion 21 and the rotation generated in the driven gear 3B meshing with the small-diameter gear portion 22 are different. Accordingly, the magnets 4A and 4B attached to the driven gears 3A and 3B rotate as the driven gears 3A and 3B rotate, so the changes in the magnetic fields generated by rotation are different between the magnet 4A and the magnet 4B. By detecting the changes in the magnitude and direction of these magnetic fields with the magnetic sensors 5A and 5B for detecting the magnetic field, the rotation angle of the detected rotating body can be accurately detected. As the magnetic sensors 5A and 5B, sensors in which the magnetic detection portion is composed of a GMR element, an MR element, a TMR element, a Hall element, etc. are used.

[0018] FIG. 2A is a cross-sectional view taken along line AA in the rotation angle detection sensor 1 shown in FIG. 1. FIG. 2B is an enlarged cross-sectional view showing each of the two driven gears 3A and 3B, the magnets 4A and 4B, and the magnetic sensors 5A and 5B in FIG. 2A. As shown in the figure, the driven gears 3A and 3B are arranged on a first plane P1 parallel to the mounting reference surface 6 of the case. In the rotation angle detection sensor 1 in the present embodiment, the mounting reference surface 6 and the first plane P1 are the same plane. The magnetic sensors 5A and 5B are arranged on a second plane P2 parallel to the mounting reference surface 6 and different from the first plane P1.

[0019] In the rotation angle detection sensor 1, the same driven gears 3A and 3B, magnets 4A and 4B, and magnetic sensors 5A and 5B are used. For this reason, hereinafter, regarding matters common to these, the driven gear 3, the magnet 4, and the magnetic sensor 5 will be referred to without appropriately attaching A and B. Similarly, A and B will be omitted as appropriate for each part of the driven gear 3.

[0020] As mentioned above, in the rotation angle detection sensor 1 of this embodiment, the driven gears 3A and 3B are identical parts. In contrast, a rotation angle detection sensor 100 in which the driven gears are not the same parts (driven gears 3A and 3B) but different parts (driven gears 3A and 103) will be given as a reference example, and the two will be explained below in comparison.

[0021] Figure 4A is a cross-sectional view of the portion of the rotation angle detection sensor 100 corresponding to Figure 2A in the reference example, and Figure 4B is an enlarged cross-sectional view showing the driven gears 3A and 103, the two magnets 4A and 4B, and the magnetic sensors 5A and 5B in Figure 4A.

[0022] Here, the driven gears 3A and 103 each have cylindrical shaft portions 33A and 133 of the same size, shape, and internal structure, and flange portions 34A and 134 that protrude from the outer circumferential surface of the shaft portions 33A and 133 in a direction parallel to the mounting reference surface 6 (first plane P1) and engage with the driving gear 2. The flange portion 134 is a disc-shaped part that extends from the shaft portion 133 and has gear teeth 1341 at its outer circumferential end.

[0023] Each of the cylindrical shaft portions 33A and 133 has a magnet mounting portion 35A and 135 at one end, which is an opening into which magnets 4A and 4B can be inserted, and the magnets 4A and 4B can be inserted into the interior through the opening. Alternatively, the cylindrical shaft portions 33A and 133 may be divided into several sections in the circumferential direction of the cylinder. The magnets 4A and 4B placed inside the shaft portions 33A and 133 are positioned at the same location, a predetermined distance from the end portions 31A and 131, which are the ends of the shaft portions 33A and 133. Furthermore, the other ends 32A and 132 of the shaft portions 33A and 133 are positioned facing the mounting reference surface 6 (first plane P1). As a result, the distance between the magnets 4A and 4B with respect to the mounting reference surface 6 (first plane P1) is the same.

[0024] Furthermore, as shown in Figures 2A and 4A, the large-diameter gear portion 21 and the small-diameter gear portion 22 of the drive gear 2 are at different distances from the mounting reference surface 6 of the lower case 62 in the direction of the rotation axis 2S (rotation axis direction, Z-axis direction). For this reason, the rotation angle detection sensor 100 shown in Figures 4A and 4B has a structure in which the position of the flange portion 34A relative to the shaft portion 33A of the driven gear 3A and the position of the flange portion 134 relative to the shaft portion 133 of the driven gear 103 are different. In other words, it was necessary to position the flange portions 34A and 134 differently to match the positions of the large-diameter gear portion 21 and the small-diameter gear portion 22 in the direction of the rotation axis 2S (rotation axis direction, Z-axis direction). Here, the distance from the mounting reference surface 6 to the flange portion 34A refers to the distance between the end portion 32A on the side of the lower case 62 that is in contact with the mounting reference surface 6 and the flange portion 34A in the direction of the rotation axis 2S and 3SA. The distance from the mounting reference surface 6 to the flange portion 134 refers to the distance between the end portion 132 of the lower case 62 that is in contact with the mounting reference surface 6 and the flange portion 134 in the direction of the rotation axes 2S and 103S. Driven gears 3A and 103 are mounted on the mounting reference surface 6 provided on the lower case 62, and magnetic sensors 5A and 5B are located on the side of the driven gears 3A and 103 opposite to the side facing the mounting reference surface 6.

[0025] The rotation angle detection sensor 100 required two different types of driven gears 3A and 103, which increased manufacturing costs. Therefore, in the rotation angle detection sensor 1 of this embodiment, manufacturing and management costs are reduced by using driven gears 3A and 3B of the same shape.

[0026] As shown in Figures 2A and 2B, the driven gear 3 in this embodiment has a shaft portion 33 and a flange portion 34. The shaft portion 33 is a cylindrical part formed around the rotating shaft 3S. The flange portion 34 is a disc-shaped part that extends from the shaft portion 33 and has gear teeth 341 at its outer peripheral end.

[0027] The general configuration of the driven gear 3 will be explained based on the cross-sectional views of the driven gears 3A and 3B shown in Figure 2B. The driven gears 3A and 3B have flange portions 34A and 34B on the side closer to one end 32A and 32B than the midpoint position C of the shaft portions 33A and 33B in the direction along the rotating shafts 3SA and 3SB. The other end 31A and 31B is open, and is configured to hold magnets 4A and 4B inside the shaft portions 33A and 33B.

[0028] The driven gear 3A is mounted on the mounting reference surface 6 of the lower case 62 such that one end 32A of the shaft portion 33A is in contact with the opposite side, and the gear teeth 341A of the flange portion 34A mesh with the large-diameter gear portion 21. The driven gear 3B is mounted on the mounting reference surface 6 of the lower case 62 such that the other end 31B of the shaft portion 33B is in contact with the opposite side, and the gear teeth 341B of the flange portion 34B mesh with the small-diameter gear portion 22.

[0029] The flange portion 34 of the driven gear 3 is positioned offset from the midpoint position C in the rotation axis 3S direction of the shaft portion 33, either to one end or the other end. When the driven gear 3 is positioned so that the end portion 32 of the shaft portion 33 is in contact with the mounting reference surface 6, the distance from the mounting reference surface 6 to the flange portion 34 is the same as the distance from the mounting reference surface 6 to the large-diameter gear portion 21. Also, when the driven gear 3 is positioned so that the end portion 31 of the shaft portion 33 is in contact with the mounting reference surface 6, the distance from the mounting reference surface 6 to the flange portion 34 is the same as the distance from the mounting reference surface 6 to the small-diameter gear portion 22. Thus, the flange portion 34 is positioned so that it can engage with the large-diameter gear portion 21 when mounted on the mounting reference surface 6 with one end portion 32 of the shaft portion 33 in contact, and so that it can engage with the small-diameter gear portion 22 when mounted on the mounting reference surface 6 with the other end portion 31 in contact.

[0030] The magnet 4 is positioned at the midpoint C of the shaft portion 33 of the driven gear 3 in the direction of the rotation axis 3S. The distance L1 from the end portion 31 of the shaft portion 33 to the center 4C (4CA, 4CB) of the magnet 4 in the direction of the rotation axis 3S is equal to the distance L2 from the end portion 32 of the shaft portion 33 to the center 4C of the magnet 4 in the direction of the rotation axis 3S.

[0031] With the above configuration, by changing the mounting direction of the driven gear 3 to the mounting reference surface 6, the position of the flange portion 34 of the lower case 62 relative to the mounting reference surface 6 in the direction of the rotation axis 3S can be changed. Therefore, by changing the mounting direction of the same driven gear 3, it is possible to determine whether to engage with the large-diameter gear portion 21 or the small-diameter gear portion 22, which have different positions relative to the mounting reference surface 6 in the direction of the rotation axis 3S.

[0032] In the rotation angle detection sensor 1, the magnet 4 is positioned on the rotation axis 3S of the driven gear 3 and at the midpoint position C in the direction of the rotation axis 3S of the driven gear 3. Therefore, even when the driven gears 3A and 3B are mounted in opposite directions in the direction of the rotation axis 3S, that is, when the driven gear 3 is mounted upside down, the positional relationship of the magnet 4 with respect to the mounting reference surface 6 of the lower case 3C remains unchanged. Consequently, by changing the orientation in which the driven gear 3 of the same shape is mounted to the mounting reference surface 6 of the lower case 3C, that is, by changing the end that is in contact with the mounting reference surface 6, the driven gear 3 (3A) for the large-diameter gear section 21 and the driven gear 3 (3B) for the small-diameter gear section 22 can be used interchangeably. This reduces the number of parts and lowers costs such as manufacturing and management expenses.

[0033] The driven gear 3 is provided with a magnet mounting portion 35 that opens toward the end 31 only on one end 32 side in the direction of the rotation axis 3S. More specifically, the shaft portion 33 is formed in a hollow cylindrical shape, and the magnet mounting portion 35 is formed on the inner wall surface of the shaft portion 33, with a bottom portion 36 that protrudes in the direction of the rotation axis 3S from a position close to the end 32 side from the midpoint position C in the direction of the rotation axis 3S.

[0034] Furthermore, the magnet mounting portion 35 (35A, 35B) is provided with a through hole 37 (37A, 37B) centered on the rotation axis 3S, and a wall portion 38 (38A, 38B) is provided that protrudes cylindrically from the end of the through hole 37 along the rotation axis 3S toward the other side of the shaft portion 33. This wall portion 38 is not a complete cylinder and may be divided in the direction of the outer circumference of the cylinder.

[0035] Furthermore, the distance L3 from the midpoint position C in the rotation axis 3S direction of the shaft portion 33 to the side of the bottom portion 36 that houses the magnet 4, facing the opening on the other end 31 side of the shaft portion 33, is approximately the same dimension as the distance L4 from one or the other side of the magnet 4 to the center 4C of the magnet 4 in the rotation axis 3S direction. Therefore, by inserting the magnet 4 from the opening on the other end 31 side of the shaft portion 33 and positioning it in contact with the side of the bottom portion 36 that houses the magnet 4, facing the opening on the other end 31 side of the shaft portion 33, the magnet 4 is positioned at the midpoint position C in the rotation axis 3S direction of the shaft portion 33. In other words, the magnet 4 is positioned at a location where the center 4C of the magnet 4 and the midpoint position C in the rotation axis 3S direction of the shaft portion 33 coincide.

[0036] Therefore, when using driven gears 3 of the same shape, there is no need to select the magnet mounting part 35 from multiple mounting parts depending on whether it is meshed with the large-diameter gear part 21 or the small-diameter gear part 22. Thus, errors in mounting the magnets 4A and 4B can be reliably prevented.

[0037] In the driven gear 3A, where end portion 32A is attached to the mounting reference surface 6 of the lower case 3C, the bottom portion 36A of the magnet mounting portion 35A is located between the magnet 4A and the mounting reference surface 6. In contrast, in the driven gear 3B, where end portion 31B is attached to the mounting reference surface 6 of the lower case 3C, the bottom portion 36B of the magnet mounting portion 35B is located between the magnet 4B and the magnetic sensor 5A. However, the bottom portion 36B, located between the driven gear 3B and the magnet 4B, does not affect the magnetic field of the magnet 4B detected by the magnetic sensor 5A.

[0038] Furthermore, on the surface of the bottom portion 36 on the end 32 side, a notch 361 (361A, 361B) with a chamfered corner is provided at the end of the through hole 37. Therefore, even when the other end 31 of the shaft portion 33 is placed in contact with the mounting reference surface 6, and the distance between the bottom portion 36 and the magnetic sensor 5 (5B) is reduced, interference between the driven gear 3 and the magnetic sensor 5 can be prevented. It is also possible to insert a part of the magnetic sensor 5 into the notch 361 in a range where the notch 361 and the magnetic sensor 5 do not come into contact, which can contribute to miniaturization of the product in the direction of the rotation axis 3S. In addition, when the support shaft 63, which will be described later, is inserted into the through hole from the notch 361 side, it also functions as a guide part for the support shaft 63.

[0039] Figure 3 is a perspective view showing the structure of the main part of the rotation angle detection sensor 1 according to this embodiment. The driven gears 3A and 3B and magnets 4A and 4B are identical except for their mounting direction, so in the figure they are referred to as driven gear 3 and magnet 4. As shown in the figure, the shape of the magnet 4 is ring-shaped. The magnet 4 is magnetized such that different magnetic poles are arranged alternately along the circumferential direction of the ring. For example, a configuration in which two different magnetic poles of the same size are arranged along the circumferential direction of the ring may be used. The magnet 4 is positioned on the inner circumferential surface 351 or outer circumferential surface 352 of the magnet mounting portion 35 on the shaft portion 33 so that the center 4C of the ring of the magnet 4 coincides with the rotation axis 3S of the driven gear 3.

[0040] By making the magnet 4 annular, it becomes easier to position the center 4C of the magnet 4 on the rotation axis 3S of the driven gear 3. Furthermore, the support shaft 63 (see Figure 2A), which protrudes from the mounting reference surface 6 and supports the driven gear 3, can be inserted through the central opening of the magnet 4. More specifically, the wall portion 38 (see Figure 2B) of the driven gear 3 into which the support shaft 63 is inserted can be inserted through the central opening of the magnet 4. As a result, compared to the case where the magnet 4 is flat, the support shaft 63 can be made longer by the length required to insert it into the central opening, thus stably supporting the driven gear 3. The center 4C of the magnet refers to the center of the outer shape of the magnet 4 when viewed from the direction of the rotation axis 3S, and also the center in the direction of the rotation axis 3S.

[0041] Furthermore, the magnet 4 has a polygonal outer or inner circumferential shape when viewed from a direction along the rotation axis 3S. When viewed from a direction along the rotation axis 3S, the shape of the inner surface 351 of the magnet mounting portion 35 is such that it can lock onto the outer circumference 41 of the magnet 4. Therefore, positioning the magnet 4 relative to the driven gear 3 becomes easy. Also, the rotation of the magnet 4 relative to the driven gear 3 is prevented, so the magnet 4 can rotate in conjunction with the rotation of the driven gear 3. In the magnet mounting portion 35 shown in Figure 3, the inner circumferential shape of the inner surface 351 is such that it can lock onto the outer circumference 41 of the magnet 4, but the outer circumferential shape of the outer surface 352 may be such that it can lock onto the inner circumference 42 of the magnet 4. [Industrial applicability]

[0042] The present invention can be used, for example, to detect the rotation angle of multiple rotatable parts, such as the steering shaft of a vehicle. [Explanation of Symbols]

[0043] 1: Rotation angle detection sensor 2: Drive gear 2S: Rotation axis 3, 3A, 3B: Driven gear 3S, 3SA, 3SB: Rotating axis 4, 4A, 4B: Magnets 4C, 4CA, 4CB: Center 5, 5A, 5B: Magnetic sensors 6: Mounting reference surface 60: Case 61: Upper case 62: Lower case 63: Support shaft 21: Large diameter gear section 22: Small diameter gear section 31, 31A, 31B: End 32, 32A, 32B: End 33, 33A, 33B: Shaft part 34, 34A, 34B: Flange section 341, 341A, 341B: Gear teeth 35, 35A, 35B: Magnet mounting section 351: Inner surface 352: Outer surface 36, 36A, 36B: Bottom 361, 361A, 361B: Notch 37, 37A, 37B: Through hole 38, 38A, 38B: Wall section 41: Perimeter 42: Inner circumference 100: Rotation angle detection sensor 103: Driven gear 103S: Rotating shaft 131: End 132: End 133: Shaft 134: Flange section 1341: Gear teeth 135: Magnet mounting part C: Midpoint position L1, L2, L3, L4: distance P1: 1st plane P2: 2nd plane

Claims

1. A driving gear having a large-diameter gear section and a small-diameter gear section, Two driven gears that mesh with the large-diameter gear portion and the small-diameter gear portion, Two magnets are attached to each of the driven gears, It comprises two magnetic sensors for detecting the magnetism of each of the aforementioned magnets, The driving gear and the driven gear have their rotation axes perpendicular to the mounting reference surface. The two driven gears are arranged on a first plane parallel to the mounting reference plane, The two magnetic sensors are rotation angle detection sensors arranged on a second plane that is parallel to the mounting reference plane and different from the first plane, The two driven gears are identical in shape and are mounted in opposite directions in the axis of rotation. The magnet is positioned on the rotation axis of the driven gear and at the midpoint in the rotation axis direction of the driven gear. The aforementioned driven gear is A hollow cylindrical shaft portion centered on the aforementioned rotation axis, The inner wall surface of the shaft portion has a bottom portion that protrudes in the direction of the rotation axis from a position close to one end side from the midpoint position, Equipped with, The magnet mounting portion is provided with a through hole centered on the rotation axis, On the bottom portion, on the surface on one end side from the midpoint position, a notch with a chamfered corner is provided at the end of the through hole. A rotation angle detection sensor characterized in that a portion of the magnetic sensor is inserted and positioned inside the notch in a manner that the notch and the magnetic sensor do not come into contact.

2. The mounting reference surface and the first plane are the same plane. It has a support shaft that supports the driven gear and protrudes from the mounting reference surface, The rotation angle detection sensor according to claim 1, wherein when the support shaft is inserted into the through hole from the notched side, the notch functions as a guide for the support shaft.

3. The driven gear has a flange portion that extends outwards in a disc shape from the shaft portion and has gear teeth at its outer peripheral end, The flange portion is provided at a position offset from the midpoint position of the shaft portion in the direction of rotation, The rotation angle detection sensor according to claim 1, wherein the center of the magnet is positioned at the midpoint position in the rotation axis direction of the shaft portion.

4. The flange portion of the driven gear is When the rotating shaft is mounted on the mounting reference surface so that one side faces the other, it is in a position where it can engage with the large-diameter gear portion. When the other side of the rotating shaft is mounted on the mounting reference surface so as to face it, it is in a position where it can engage with the small-diameter gear portion. The rotation angle detection sensor according to claim 3.

5. The driven gear is provided with the magnet mounting portion on only one side in the direction of rotation. The rotation angle detection sensor according to claim 1.

6. The shape of the magnet is a ring, and it is magnetized such that different magnetic poles are arranged alternately along the circumferential direction of the ring. The magnet is positioned either inside or outside the shaft portion such that the center of the ring coincides with the rotation axis of the driven gear. The rotation angle detection sensor according to claim 2 or claim 3.

7. When viewed from the direction of the rotation axis, the outer or inner circumference shape of the magnet is polygonal. When viewed from the direction of the rotation axis, the inner surface of the shaft portion is shaped to be able to engage with the outer circumference of the magnet, or the outer surface of the shaft portion is shaped to be able to engage with the inner circumference of the magnet. The rotation angle detection sensor according to claim 6.

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