JP6375156B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device mounted on a vehicle.

  Patent Document 1 discloses an electric power steering device that applies a steering assist force by an electric motor. This electric power steering device rotates in accordance with the rotation of the steering wheel and transmits the rotation to the rack shaft, and the worm wheel mounted on the pinion shaft and transmits the rotation of the steering assist electric motor to the pinion shaft And a steering angle sensor for detecting a steering angle of a steering shaft coupled between the pinion shaft and the steering wheel.

  The rudder angle sensor has a first gear mounted on the steering shaft, a second gear meshing with the first gear, and a sensor case that houses the first gear and the second gear, and rotates as the steering shaft rotates. The steering angle of the steering shaft is detected based on the rotation of the second gear.

JP 2013-174517 A

  In the above conventional technique, the grease applied to the worm wheel arranged below the sensor case enters the sensor case through the gap between the through hole of the sensor case through which the steering shaft passes and the steering shaft, and the first gear. And the grease applied to the second gear may be mixed, and the meshing characteristics of the first gear and the second gear may change.

  The present invention has been made in view of such a technical problem, and provides an electric power steering device capable of preventing the grease of the worm wheel from being mixed into the grease of the gear provided in the sensor case. Objective.

The present invention is an electric power steering device in which a turning force is input to a pinion shaft by an electric motor, and a rack shaft meshing with the pinion shaft is moved in the axial direction of the rack shaft to steer a wheel, and is integrated with the pinion shaft. A worm wheel that is rotatably mounted and to which a turning force is input by an electric motor, and a rotation angle detection unit that is disposed adjacent to the worm wheel and detects a rotation angle of the pinion shaft, the rotation angle detection unit, The rotation angle of the pinion shaft is calculated based on the rotation of the center gear, which is mounted on the outer periphery of the pinion shaft so as to rotate integrally with the pinion shaft and has a gear portion on the outer periphery, the outer gear meshing with the gear portion of the center gear, and the rotation of the outer gear. A sensor having a calculation part, a receiving part for receiving the center gear and the outer gear, and a through hole through which the pinion shaft passes. Includes a case, and around the inner surface and a through-hole of the housing portion of the sensor case grooves are formed, the center gear, between the end face of the gear portion opposed to the opening end surface and the opening end face of the through hole It is characterized by being fixed to the pinion shaft so that a gap communicating with the groove is formed .

  According to the present invention, since a groove is formed on the inner surface of the housing portion of the sensor case and around the through hole, the grease applied to the worm wheel enters the sensor case from the gap between the through hole and the pinion shaft. In this case, the grease can be trapped by the groove. Therefore, it is possible to prevent the meshing characteristics from changing due to the grease of the worm wheel being mixed with the grease used for the center gear and the outer gear in the sensor case.

It is a lineblock diagram of an electric power steering device concerning an embodiment of the present invention. It is a fragmentary sectional view of the electric power steering device concerning the embodiment of the present invention. It is an enlarged view near the upper part of the pinion shaft. It is a perspective view which shows the state which has arrange | positioned the center gear and the outer gear to the sensor case. It is a perspective view which shows only a sensor case.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of an electric power steering apparatus 100 in the present embodiment.

  The electric power steering device 100 is a dual pinion type electric power steering device 100 that inputs a steering force by a driver and an assist driving force by the electric motor 21 to the rack shaft 12 independently of each other.

  The electric power steering apparatus 100 includes a steering mechanism 10 that steers the steered wheels 2 as wheels of a vehicle in response to rotation of the steering wheel 1 to which a steering force is input by a driver, and an assist mechanism that assists the driver's steering force. 20 and a control mechanism 30 that controls the assist amount of the steering force.

  The steering mechanism 10 includes a steering shaft 11 that is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1, and a rack shaft 12 that steers the steered wheels 2 of the vehicle according to the rotation of the steering shaft 11. Have.

  The steering shaft 11 includes an input shaft 13 connected to the steering wheel 1, an intermediate shaft 15 connected to the input shaft 13 via a torsion bar 14, and an end of the intermediate shaft 15 opposite to the torsion bar 14. The output shaft 16 is connected, and a first pinion 17 is provided at the end of the output shaft 16 opposite to the intermediate shaft 15 and meshes with the rack shaft 12.

  The assist mechanism 20 includes an electric motor 21 that is a source of assist force, a pinion shaft 22 that is connected to an output shaft of the electric motor 21 and transmits a driving force of the electric motor 21 to the rack shaft 12, and an electric motor of the pinion shaft 22. The second pinion 23 provided at the end opposite to the shaft 21 and meshed with the rack shaft 12 is serrated to the outer periphery of the pinion shaft 22 so as to rotate integrally with the pinion shaft 22, and the driving force of the electric motor 21 is reduced. Worm wheel 26 (FIG. 2) input via 39 (FIG. 1).

  The control mechanism 30 is a torque sensor 31 that detects a steering torque applied to the torsion bar 14 based on the relative rotation between the input shaft 13 and the output shaft 16, and a rotation angle detection unit that detects the rotation angle of the pinion shaft 22. Rotation angle sensor 32, steering angle sensor 34 that detects the steering angle that is the rotation angle of the steering wheel 1, motor rotation angle sensor 35 that is configured by a resolver and detects the rotation angle of the electric motor 21, and the electric motor 21 And a controller 33 for controlling the operation.

  The controller 33 controls the electric motor 21 based on the steering torque detected by the torque sensor 31 and the rotation angle detected by the motor rotation angle sensor 35. The controller 33 considers the steering angle detected by the steering angle sensor 34 and the rotation angle of the pinion shaft 22 detected by the rotation angle sensor 32 in addition to the steering torque and the rotation angle of the electric motor 21. 21 may be controlled. The steering angle detected by the steering angle sensor 34 and the rotation angle of the pinion shaft 22 detected by the rotation angle sensor 32 are not limited to the control of the electric motor 21, such as a VDC (Vehicle Dynamics Control) that suppresses the side slip of the vehicle. Used in control. In this embodiment, the steering angle sensor 34 is provided, but the steering angle sensor 34 may not be provided.

  FIG. 2 is a partial cross-sectional view mainly showing the pinion shaft 22 of the electric power steering apparatus 100. FIG. 3 is an enlarged view showing the vicinity of the head of the pinion shaft 22 in an enlarged manner.

  The electric power steering device 100 further includes a lower housing 25 in which a part of the rack shaft 12 and the pinion shaft 22 on the rack shaft 12 side is housed, and bearings 24 and 29 are provided to rotatably support the pinion shaft 22. An upper housing 27 that accommodates the wheel 26 and a cover 28 that is fixed to the opening of the upper housing 27 and covers the head 22 a of the pinion shaft 22 are provided. A rotation angle sensor 32 is disposed in the cover 28 so as to be adjacent to the worm wheel 26.

  The pinion shaft 22 is formed in a cylindrical shape at the end opposite to the portion where the second pinion 23 is provided, and a plurality of pinion shafts 22 are formed along the circumferential direction on the inner peripheral surface of the head 22a. A groove portion 22b recessed outward. An annular groove 22c is formed in the circumferential direction on the worm wheel 26 side on the outer peripheral surface of the pinion shaft 22 where a sensor case 46 described later is mounted.

  The rotation angle sensor 32 is attached to the head portion 22a of the pinion shaft 22 and has a center gear 41 having a gear portion 41a on the outer periphery, two outer gears 42 and 43 (FIG. 4) meshing with the center gear 41, and each outer gear 42. , 43, and a substrate portion 44 as a calculation portion that transmits a signal to the controller 33, a center gear 41, outer gears 42, 43, and a housing portion 46 b that houses the substrate portion 44, and the pinion shaft 22. And a sensor case 46 having a through hole 47 through which it penetrates.

  The center gear 41 is fitted to a cylindrical sleeve 41b that covers the outer peripheral surface and the end surface of the head portion 22a of the pinion shaft 22 and the groove portion 22b of the pinion shaft 22 that extends to the inner peripheral side of the sleeve 41b. A plurality of fixing portions 45 that fix 41 to the head portion 22a and restrict movement in the circumferential direction and the radial direction.

  The two outer gears 42 and 43 have different numbers of teeth and rotate at a higher speed in accordance with the rotation of the center gear 41. Further, a magnet (not shown) that rotates together with the outer gears 42 and 43 is fixed to the outer gears 42 and 43.

  The substrate 44 has two sensor ICs (not shown) that are disposed in proximity to the two outer gears 42 and 43 and face the magnets of the outer gears 42 and 43 in a non-contact manner. The board portion 44 calculates the rotation angle of the center gear 41, that is, the rotation angle of the pinion shaft 22 based on the change in magnetic flux accompanying the rotation of the two outer gears 42 and 43, and transmits the calculation result to the controller 33.

  FIG. 4 is a perspective view showing a state in which the center gear 41 and the outer gears 42 and 43 are arranged on the sensor case 46. FIG. 5 is a perspective view showing only the sensor case 46.

  The sensor case 46 is formed in a bottomed cylindrical shape, and has a through hole 47 through which the pinion shaft 22 penetrates in the center of the housing portion 46b. That is, the sensor case 46 has an annular bottom 46a. An annular bottom portion 46a is inserted with an attachment portion 48 that rotatably supports the two outer gears 42 and 43, and a positioning pin 28a (FIG. 2) of the cover 28 when the sensor case 46 is attached to the cover 28. Positioning holes 49 are provided.

  When the pinion shaft 22 penetrates the sensor case 46 and the center gear 41 is attached to the head of the pinion shaft 22, the gear portion 41 a of the center gear 41 is positioned at the bottom portion 46 a of the sensor case 46. When the outer gears 42 and 43 are attached to the attachment portion 48, the center gear 41 and the outer gears 42 and 43 are held in mesh with each other, and the outer gears 42 and 43 rotate in accordance with the rotation of the center gear 41, thereby causing the center gear 41 to rotate. A rotation angle of 41 is detected.

  An annular groove 50 is further formed around the through hole 47 in the bottom 46 a of the sensor case 46. The groove 50 is formed in an annular shape surrounding the through hole, and the inner diameter of the groove 50 is set to be smaller than the outer diameter of the gear portion 41 a of the center gear 41. Further, the bottom portion 46 a of the sensor case 46 is set to be positioned above the lower end of the gear portion 41 a of the center gear 41.

  Here, grease is applied to the center gear 41 and the outer gears 42 and 43 for mutual meshing. The purpose of this grease is to assist the transmission of rotation from the center gear 41 to the outer gears 42 and 43 over the entire operating temperature range.

  Grease is applied to the worm wheel 26 for meshing with a worm (not shown) that rotates in conjunction with the output shaft of the electric motor 21. This grease is used for transmitting force from the worm to the worm wheel 26, and has a high viscosity particularly at low temperatures.

  As described above, since the grease applied to the worm wheel 26 and the grease applied to the center gear 41 and the outer gears 42 and 43 have different characteristics, it is not preferable that they are mixed. In particular, when the grease applied to the worm wheel 26 is mixed into the grease applied to the center gear 41 and the outer gears 42 and 43, the meshing characteristics of the center gear 41 and the outer gears 42 and 43 change, and the rotation angle The detection accuracy of the rotation angle of the pinion shaft 22 by the sensor 32 may be reduced due to hysteresis or the like.

  However, in this embodiment, since the annular groove 50 is formed around the through hole 47 on the bottom surface 46a of the sensor case 46, the grease applied to the worm wheel 26 penetrates as shown in FIG. Even if it enters the sensor case 46 through the gap between the hole 47 and the pinion shaft 22, the grease can be trapped by the groove 50, so that the grease that has entered enters the center gear 41 and the outer gear 42 in the sensor case 46. , 43 is prevented from entering the meshing portion.

  According to the above embodiment, there exist the effects shown below.

  Since the groove 50 is formed on the inner surface of the housing portion 46 b of the sensor case 46 and around the through hole 47, the grease applied to the worm wheel 26 is introduced into the sensor case 46 from the gap between the through hole 47 and the pinion shaft 22. The grease can be trapped by the groove 50 when it enters the groove. Therefore, the grease of the worm wheel 26 can be prevented from being mixed with the grease used for meshing of the center gear 41 and the outer gears 42 and 43 in the sensor case 46 and changing the meshing characteristics. Therefore, it is possible to prevent a decrease in detection accuracy of the rotation angle sensor 32 due to a change in meshing characteristics between the center gear 41 and the outer gears 42 and 43.

  Further, even if contamination such as abrasion powder occurs due to the engagement of the center gear 41 and the outer gears 42 and 43 in the sensor case 46, the contamination can be retained in the groove 50, so that the contamination moves to the worm wheel 26 side. Thus, it is possible to prevent the transmission of the turning force from being blocked by the worm wheel 26.

  Furthermore, since the groove 50 is formed in an annular shape surrounding the through hole 47, the groove 50 prevents the grease applied to the worm wheel 26 from entering any position in the circumferential direction in the through hole 47 into the sensor case 46. Can be trapped. Therefore, it is possible to more reliably prevent a decrease in detection accuracy of the rotation angle sensor 32 due to a change in meshing characteristics between the center gear 41 and the outer gears 42 and 43.

  Further, since the inner diameter of the groove 50 is set to be smaller than the outer diameter of the gear portion 41a of the center gear 41, the grease that enters the sensor case 46 from the worm wheel 26 side is removed from the center gear 41 and the outer gear. It is possible to trap before reaching the meshing portion with 42 and 43. Therefore, the grease of the worm wheel 26 is more reliably prevented from entering the grease used for meshing of the center gear 41 and the outer gears 42 and 43 in the sensor case 46, and the detection accuracy of the rotation angle sensor 32 is reduced. Can be more reliably prevented.

  Further, since the annular groove 22 c is formed on the outer peripheral surface of the pinion shaft 22, the grease applied to the worm wheel 26 can be trapped before entering the gap between the through hole 47 and the pinion shaft 22. Therefore, the grease of the worm wheel 26 can be more reliably prevented from being mixed into the grease in the sensor case 46.

  Furthermore, since the bottom part 46a of the sensor case 46 is set to be positioned above the lower end of the gear part 41a of the center gear 41, the height (depth) of the groove 50 can be increased. Therefore, the grease that has entered the gap between the through-hole 47 and the pinion shaft 22 can be trapped more reliably, and is mixed with the grease used for meshing of the center gear 41 and the outer gears 42 and 43 and has meshing characteristics. It is possible to prevent the change.

  The embodiment of the present invention has been described above. However, the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above-described embodiment, the dual pinion type electric power steering device 100 is taken as an example, but the present invention can also be applied to a single pinion type electric power steering device and a steer-by-wire type electric power steering device.

  Furthermore, in the above embodiment, the case where the groove 50 is formed in an annular shape surrounding the through hole 47 is illustrated, but the groove 50 is not connected in an annular shape, and the meshing portion between the center gear 41 and the outer gears 42 and 43 is illustrated. The grooves may be provided only in the vicinity, or may be provided so as to be scattered around the through holes 47.

  Further, in the above embodiment, the inner diameter of the groove 50 is set to be smaller than the outer diameter of the gear portion 41a of the center gear 41, but the inner diameter of the groove 50 is equal to or larger than the outer diameter of the gear portion 41a of the center gear 41. It may be set to be.

1 Steering wheel 2 Snake wheel
12 rack shaft 21 electric motor 22 pinion shaft 26 worm wheel 32 rotation angle sensor (rotation angle detector)
41 Center gear 41a Gear part 42 Outer gear 43 Outer gear 44 Substrate part (calculation part)
46 sensor case 46b accommodating portion 47 through hole 50 groove 100 electric power steering device

Claims (3)

A steering power is input to a pinion shaft by an electric motor, and an electric power steering device for turning a wheel by moving a rack shaft meshing with the pinion shaft in an axial direction of the rack shaft,
A worm wheel that is mounted on the outer periphery of the pinion shaft so as to be able to rotate integrally with the pinion shaft, and a turning force is input by the electric motor;
A rotation angle detector that is disposed adjacent to the worm wheel and detects a rotation angle of the pinion shaft;
The rotation angle detector includes a center gear that is mounted so as to rotate integrally with the pinion shaft and has a gear portion on an outer periphery, an outer gear that meshes with the gear portion of the center gear, and the pinion based on rotation of the outer gear A calculation unit that calculates the rotation angle of the shaft, and a sensor case that includes a storage unit that stores the center gear and the outer gear and has a through hole through which the pinion shaft passes.
A groove is formed on the inner surface of the housing portion of the sensor case and around the through hole ,
The center gear is fixed to the pinion shaft so that a gap communicating with the groove is formed between an opening end face of the through hole and an end face of the gear portion facing the opening end face.
An electric power steering device. The groove is formed in an annular shape surrounding the through hole.
The electric power steering apparatus according to claim 1. The inner diameter of the groove is set to be smaller than the outer diameter of the gear portion of the center gear.
The electric power steering apparatus according to claim 2.

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