JP2016022794A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device that facilitates insertion of a torsion bar into an output shaft and has little defect in a torque sensor.SOLUTION: The electric power steering device comprises: an input shaft 30; a torsion bar 31 one end of which is rotatably connected to the input shaft 30; an output shaft 32 rotatably connected to the other end of the torsion bar 31; a torque sensor 50 that detects steering torque from relative rotation between the input shaft 30 and the output shaft 32; and a housing 10 that supports rotatably the input shaft 30 and the output shaft 32. To an inner periphery of the output shaft 32 is loosely fitted an outer periphery of the other end of the torsion bar 31, and between the inner periphery of the output shaft 32 and the outer periphery of the torsion bar 31 is inserted a ring-like elastic member 39 in order to fill a gap at a loosely fitted part. The output shaft 32 and the torsion bar 31 are rotatably connected to each other through a connection pin arranged in a radial direction of the output shaft 32.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electric power steering apparatus in which an input shaft and an output shaft are rotationally connected via a torsion bar.

  As an electric power steering apparatus, for example, there is one as shown in Patent Document 1, an input shaft having a steering shaft rotationally connected thereto, a torsion bar having one end rotationally connected to the input shaft, and a rotational connection to the other end of the torsion bar. An output shaft, a torque sensor for detecting a steering torque from the relative rotation between the input shaft and the output shaft, and a housing for rotatably supporting the input shaft and the output shaft, and a torsion bar on the inner periphery of the output shaft. The outer periphery of the other end was fitted, and the output shaft and the torsion bar were rotationally connected via a connecting pin arranged in the radial direction of the output shaft.

JP 2014-80991 A

  Since the output shaft and the torsion bar are arranged coaxially, there is not much space between the output shaft and the torsion bar, which makes it difficult to insert the torsion bar into the output shaft. In addition, it is difficult to align the position of the torsion bar in the axial direction with respect to the output shaft, and a deviation occurs between the components of the torque sensor, and a torque sensor failure is likely to occur. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering device that facilitates insertion of a torsion bar into an output shaft and reduces torque sensor defects. It is.

  The invention according to claim 1 is a steering shaft, an input shaft whose one end is rotationally connected to the other end of the steering shaft, a torsion bar whose one end is rotationally connected to the input shaft, and the other end of the torsion bar An output shaft that is rotationally coupled to the input shaft, a torque sensor that detects steering torque from relative rotation between the input shaft and the output shaft, a steering tube that rotatably supports the steering shaft, and a second end of the steering tube. In the electric power steering apparatus including a housing that is fixed and rotatably supports the input shaft and the output shaft, the outer periphery of the other end of the torsion bar is fitted into the inner periphery of the output shaft. In order to fill the gap between the joined portions, a ring-like elasticity is provided between the inner periphery of the output shaft and the outer periphery of the torsion bar. Inserted through the wood, the output shaft and the torsion bar, it is characterized in that it has rotatably connected via the arranged connecting pin in a radial direction of the output shaft.

  According to the present invention, since the gap between the inner periphery of the output shaft and the outer periphery of the other end of the torsion bar is increased and only the elastic member is brought into contact with the inner periphery of the output shaft, the torsion bar can be easily inserted into the output shaft. Since it becomes difficult for deviation to occur between the components of the torque sensor, it is possible to provide an electric power steering apparatus with few torque sensor defects.

Sectional drawing containing the axis line of the output shaft of the electric power steering apparatus in one Embodiment of this invention. The principal part expanded sectional view of FIG. 1 in one Embodiment of this invention. The AA sectional view taken on the line of FIG. 1 in one Embodiment of this invention. The BB sectional drawing of FIG. 1 in one Embodiment of this invention. The CC sectional view taken on the line of FIG. 1 in one Embodiment of this invention.

  An embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the electric power steering apparatus includes a steering tube, a steering shaft rotatably supported by the steering tube, a housing 10 fitted and fixed to the other end of the steering tube, and a housing 10 that is rotatable. An input shaft 30 that is supported by a bearing, an output shaft 32 that is rotatably supported by the housing 10, a torsion bar 31 having one end rotationally coupled to the input shaft 30 and the other end rotationally coupled to the output shaft 32, and an input shaft 30 and a torque sensor 50 for detecting steering torque from the relative rotation of the output shaft 32, a worm wheel 40 fitted and fixed to the outer periphery of the output shaft 32, a worm 43 meshing with the worm wheel 40, and the worm 43 being driven to rotate. Drive motor 15.

  A steering wheel (not shown) is rotationally connected to one end of the steering shaft, and an intermediate shaft (not shown) is rotationally connected to the other end of the output shaft 32. The electric power steering device has a function of transmitting the rotation of the steering wheel to the intermediate shaft, and also has a function of assisting power by the drive motor 15.

  The steering tube includes a cylindrical upper tube 20, a cylindrical lower tube 21, and a resin sheet 22 provided on the inner periphery of the upper tube 20. The upper tube 20 is larger in diameter than the lower tube 21, and the upper tube 20 is fitted to the lower tube 21 via the resin sheet 22 so as to be able to advance and retract in the axial direction. The other end of the lower tube 21 is fitted and fixed to the housing 10. The upper tube 20 is supported by a vehicle (not shown) via an upper side support mechanism so as to be telescopic and tiltable.

  The upper side support mechanism includes a mounting bracket 23 fixed to the vehicle, a U-shaped upper bracket 24 fixed to the mounting bracket 23, and a lower bracket having a U-shaped cross section fixed to the upper tube 20. 27, a rotary shaft 28 rotatably supported by the lower bracket 27, and an eccentric cam 29 attached to the rotary shaft 28. The rotating shaft 28 includes a pair of clamping members (not shown) that press-contact the upper bracket 24 to the lower bracket 27. After the lower bracket 27 is tilted with respect to the upper bracket 24, it can be locked by a pair of clamping members. After telescoping the upper tube 20 with respect to the lower tube 21, it can be locked by an eccentric cam 29.

  A steering shaft is rotatably supported by the steering tube via a first rolling bearing (not shown) and a needle bearing 65. The steering shaft includes an upper shaft 25 that is rotatably supported by the upper tube 20 via a first rolling bearing, and a lower shaft 26 that is loosely fitted to the lower tube 21. The outer periphery of one end of the lower shaft 26 is spline-fitted to the inner periphery of the other end of the upper shaft 25, and the lower shaft 26 is capable of moving forward and backward in the axial direction with respect to the upper shaft 25 and transmitting rotation. A handle (not shown) operated by the driver is connected to one end of the upper shaft 25, and the other end of the lower shaft 26 is fitted and fixed to the input shaft 30.

  The housing 10 is made of a casting, and includes a sensor housing 11 and a gear housing 12 connected to the sensor housing 11 via a screw part 17. The gear housing 12 includes a bifurcated support bracket 13, a disk-shaped motor bracket 14, and a first mounting bracket that protrudes in the outer diameter direction at two locations around the circumference. The support bracket 13 is rotatably supported by a vehicle (not shown) via a lower side support mechanism (not shown). A drive motor 15 is attached to the motor bracket 14 via attachment bolts 16 and has a second attachment bracket that protrudes in the outer diameter direction at two locations around the circumference (FIG. 3). The sensor housing 11 is fixed to the gear housing 12 by inserting the screw component 17 through the first mounting bracket and screwing the screw component 17 into the screw hole of the second mounting bracket.

  The housing 10 is formed with an internal space 10a in which the worm wheel 40 and the worm 43 are rotatably accommodated.

  An input shaft 30 and an output shaft 32 are supported on the housing 10 so as to be axially displaced from each other so as to be rotatable about the same axis. The input shaft 30 is rotatably supported by the sensor housing 11 via a needle bearing 65, and is rotatably supported by the output shaft 32 via a resin sliding bearing 36. The output shaft 32 is rotatably supported by the sensor housing 11 via the second rolling bearing 70 and is rotatably supported by the gear housing 12 via the third rolling bearing 75.

  The second rolling bearing 70 is a ball bearing using balls as rolling elements. A second outer ring of the second rolling bearing 70 is fitted to the inner periphery of the sensor housing 11 with a clearance fit. A second inner ring of the second rolling bearing 70 is fitted on the outer periphery of one end of the output shaft 32 with an interference fit. The other end surface of the second inner ring 72 is in contact with the first step surface of the output shaft 32.

  The third rolling bearing 75 is a ball bearing using balls as rolling elements. A cylindrical third fitting surface is formed on the inner periphery of the gear housing 12, and a second step surface extending in the inner diameter direction is formed on the other end side of the third fitting surface. The third outer ring of the third rolling bearing 75 is fitted to the third fitting surface with an interference fit. The other end surface of the third outer ring is in contact with the second step surface. A retaining ring 37 that abuts one end surface of the third outer ring is fitted in an annular groove formed in the gear housing 12. The second step surface and the retaining ring 37 can prevent the third outer ring from coming off from the gear housing 12 in the axial direction.

  A cylindrical fourth fitting surface is formed on the center outer periphery of the output shaft 32, and a third step surface extending in the outer diameter direction is formed on one end side of the fourth fitting surface. The third inner ring 77 is fitted to the fourth fitting surface with an interference fit. One end surface of the third inner ring is in contact with the fourth step surface. A locking nut 38 that contacts the other end surface of the third inner ring is screwed onto the outer periphery of the output shaft 32. The fourth step surface and the lock nut 38 can prevent the third inner ring from coming off from the output shaft 32 in the axial direction.

  The torsion bar 31 has a first large diameter portion 31e having a large diameter at one end, a second large diameter portion 31c having a large diameter at the other end, and a small diameter portion 31d having a small diameter in the middle. The first large diameter portion 31e has an outer diameter that is approximately several hundred microns larger than that of the second large diameter portion 31c (FIG. 2). The small diameter part 31d has a smaller outer diameter than the first large diameter part 31e and the second large diameter part 31c. An annular groove 31b having a quadrangular cross section is formed on the outer periphery of the second large diameter portion 31c, and an O-ring 39 is fitted in the annular groove 31b. In a state where the O-ring 39 is fitted in the annular groove 31b, the maximum outer diameter of the O-ring 39 is approximately several hundred microns larger than the second fitting surface 32b. The O-ring 39 is an elastic member made of rubber and capable of compressive deformation in the inner diameter direction.

  A first fitting surface 30 a having a diameter of about 100 microns smaller than the first large diameter portion 31 e of the torsion bar 31 is formed on the inner periphery of one end of the input shaft 30. Therefore, the first large-diameter portion 31e is press-fitted and fitted to the first fitting surface 30a with a squeeze of about 50 microns.

  An insertion surface 32e, a sliding surface 32d, a step surface, and a second fitting surface 32b are formed in order from one end on the inner periphery of the output shaft 32. The insertion surface 32e, the sliding surface 32d, and the second fitting surface 32b are formed. The inner diameter becomes smaller in this order (FIG. 4). The second fitting surface 32 b has a larger inner diameter of about 100 microns than the second large diameter portion 31 c of the torsion bar 31. Therefore, the second large-diameter portion 31c is fitted into the second fitting surface 32b with a gap of about 50 microns, and the O-ring 39 is about half of several hundred microns on the second fitting surface 32b. It is press-fitted and fitted. When the O-ring 39 is compressed with a half of several hundred microns, the O-ring 39 is in a state close to a rigid body and does not elastically deform by several microns. A chamfer 32c is formed on the inner diameter side on the insertion surface 32e side of the step surface, and the maximum diameter of the chamfer 32c is larger than the maximum outer diameter of the O-ring 39.

  As shown in FIG. 1, the other end of the output shaft 32 and the other end of the torsion bar 31 have a first fitting hole 32a and a second fitting hole 31a in a state where the output shaft 32 is fitted to the torsion bar 31. The joint pin 33 is press-fitted into the first fitting hole 32 a and the second fitting hole 31 a, and the output shaft 32 and the torsion bar 31 are rotationally connected via the connection pin 33.

  The torque sensor 50 includes a resin collar 55 press fitted to the outer periphery of the input shaft 30, a magnet 54 held by the collar 55, an iron collar 53 press fitted to the outer periphery of the output shaft 32, and A resin-made relay member 52 press-fitted into the collar 53 and a concentration member 51 provided on the sensor housing 11 are included. A pair of cores are embedded in the relay member 52, and a pair of concentration rings are embedded in the concentration member 51. The amount of relative rotation between the input shaft 30 and the output shaft 32 is detected by capturing the magnetic force of the magnet 54 with a pair of concentrated rings via a pair of cores. As the relative rotation amount between the input shaft 30 and the output shaft 32 increases, the torsional torque of the torsion bar 31 increases, so that the steering torque can be detected by the torque sensor 50.

  As shown in FIGS. 1 and 5, a worm wheel 40 is fitted and fixed to the output shaft 32, and a worm 43 is engaged with the worm wheel 40. The worm 43 is rotatably supported by the gear housing 12 via a pair of rolling bearings 44 and 45. The drive shaft of the drive motor 15 is rotationally connected to the worm 43, and the rotation of the drive motor 15 is transmitted to the output shaft 32 via the worm 43 and the worm wheel 40. A coupling 46 is provided between the worm 43 and the drive shaft. The rotational force of the drive motor 15 increases as the steering torque detected by the torque sensor 50 increases.

  The support bracket 13 is rotatably supported by a vehicle (not shown) via a lower side support mechanism (not shown). The upper tube 20 is supported by a vehicle (not shown) via an upper side support mechanism so as to be telescopic and tiltable.

  Next, the assembling operation of the input shaft 30 and the output shaft 32 will be described based on the above-described configuration.

  As shown in FIG. 1, the worm wheel 40 is fitted to the outer periphery of the output shaft 32 by an interference fit. The second inner ring of the second rolling bearing 70 is fitted to the second fitting surface of the output shaft 32 with an interference fit, and the other end surface of the second inner ring is in contact with the first step surface. Furthermore, a collar 53 holding a resin-made relay member 52 is press-fitted onto the second fitting surface of the output shaft 32. The outer periphery of the resin sliding bearing 36 is fitted into the inner periphery of one end of the output shaft 32. Thus, an assembly of the output shaft 32 to which the worm wheel 40, the second rolling bearing 70, the relay member 52, and the resin sliding bearing 36 are attached is produced.

  The third outer ring of the third rolling bearing 75 is fitted into the third fitting surface of the gear housing 12 with an interference fit, and the other end surface of the third outer ring is in contact with the second step surface. A retaining ring 37 is fitted into the annular groove of the gear housing 12, and one end surface of the third outer ring abuts on the retaining ring 37. The second step surface and the retaining ring 37 can prevent the third outer ring from coming off from the gear housing 12 in the axial direction. A worm 43 is inserted into the gear housing 12, and a pair of rolling bearings 44 and 45 are inserted between the inner periphery of the gear housing 12 and the outer periphery of both ends of the worm 43, and the rolling bearing 44 is fixed to the gear housing 12 by a pressing ring 47. Thus, an assembly of the gear housing 12 to which the worm 43 and the third rolling bearing 75 are attached is produced.

  The assembly of the output shaft 32 is assembled to the assembly of the gear housing 12. While the worm wheel 40 is engaged with the worm 43, the third inner ring of the third rolling bearing 75 is fitted into the fourth fitting surface of the output shaft 32 with an interference fit, and one end surface of the third inner ring is fitted into the fourth step surface. Abut. A lock nut 38 is screwed onto the outer periphery of the output shaft 32, and the other end surface of the third inner ring contacts the lock nut 38. The fourth step surface and the lock nut 38 can prevent the third inner ring 77 from coming off from the output shaft 32 in the axial direction. In this way, a large assembly of the gear housing 12 to which the assembly of the output shaft 32 is attached is produced.

  A collar 55 holding a magnet 54 is press fitted into the outer periphery of the input shaft 30. The other end of the torsion bar 31 is inserted from one end of the input shaft 30, and the first large-diameter portion 31e of the torsion bar 31 is press-fitted to the first fitting surface 30a of the input shaft 30 with a squeeze of about 50 microns. . Thus, an assembly of the input shaft 30 to which the torsion bar 31 and the magnet 54 are attached is produced.

  The outer periphery of the needle bearing 65 is fitted into the inner periphery of the sensor housing 11 with an interference fit. Thus, an assembly of the sensor housing 11 to which the needle bearing 65 is attached is made.

  The assembly of the input shaft 30 is assembled to the large assembly of the gear housing 12. The other end of the torsion bar 31 is inserted from one end of the output shaft 32. In this process, the second large diameter portion 31c of the torsion bar 31 is inserted through the insertion surface 32e and the sliding surface 32d without any resistance, and a part of the second large diameter portion 31c is the second fitting of the output shaft 32. A gap is fitted into the mating surface 32b with a gap of about 50 microns. Since the gap fitting has a gap of about 50 microns, the second large diameter portion 31c can be smoothly fitted to the second fitting surface 32b. When the torsion bar 31 is further inserted into the output shaft 32, the O-ring 39 comes into contact with the chamfer 32c, the O-ring 39 is compressed in the inner diameter direction, and the O-ring 39 is about half of several hundred microns in the second large diameter portion 31c. It is press-fitted with a shimeshiro. Since only the O-ring 39 is in contact with the second fitting surface 32b, the twist due to the inclination hardly occurs. In the process of inserting the torsion bar 31 into the output shaft 32, the outer periphery of the other end of the input shaft 30 is fitted to the inner periphery of the resin sliding bearing 36.

  The other end of the output shaft 32 and the other end of the torsion bar 31 are formed with a first fitting hole 32a and a second fitting hole 31a in a state where the torsion bar 31 is fitted to the output shaft 32. The connecting pin 33 is press-fitted into the first fitting hole 32 a and the second fitting hole 31 a, and the output shaft 32 and the torsion bar 31 are rotationally connected via the connecting pin 33. The O-ring 39 is press-fitted into the second large-diameter portion 31c with a half of several hundred microns, so that the O-ring 39 is close to a rigid body by the half of a few hundred microns. Even if the connecting pin 33 is press-fitted into the joint hole 31a, the torsion bar 31 is displaced in the radial direction with respect to the output shaft 32 only within an elastic deformation range of the O-ring 39 about several microns. The torsional characteristics of the torsion bar 31 are not impaired. Thus, a large assembly of the gear housing 12 to which the assembly of the input shaft 30 is attached is produced.

  The assembly of the sensor housing 11 is attached to a large assembly of the gear housing 12. The outer circumference of the second outer ring of the second rolling bearing 70 is fitted to the inner circumference of the sensor housing 11 with a gap fit, and the outer circumference of the input shaft 30 is fitted to the needle of the needle bearing 65 with a gap fit. In a state where the sensor housing 11 is fitted with a gap fit, the screw component 17 is inserted into the sensor housing 11 and screwed into the screw hole of the gear housing 12. Thus, as shown in FIG. 1, the magnet 54 is arranged on the inner peripheral side of the relay member 52, and the sensor housing 11 and the gear housing 12 are integrated to constitute the housing 10.

  Next, the usage status of the electric power steering apparatus will be described.

  When the handle (not shown) is operated, the upper shaft 25 rotates as shown in FIG. 1, and the rotation of the upper shaft 25 is omitted via the lower shaft 26, the input shaft 30, the torsion bar 31, and the output shaft 32. Is transmitted to the intermediate shaft. The road surface resistance is transmitted to the output shaft 32 through the intermediate shaft. The torsion bar 31 is twisted by the operation of the steering wheel and the road surface resistance, relative rotation occurs between the input shaft 30 and the output shaft 32, and the relative rotation amount, that is, the steering torque is detected by the torque sensor 50.

  A signal from the torque sensor 50 is input to a control device (not shown), and an output signal corresponding to the steering torque is applied to the drive motor 15 from the control device. The rotation of the drive motor 15 is transmitted to the output shaft 32 via the worm 43 and the worm wheel 40. The drive motor 15 generates a rotational force corresponding to the steering torque and power assists the steering wheel operation.

  The present invention is not limited to these embodiments, and can of course be implemented in various modes without departing from the gist of the present invention.

  10: housing, 25: upper shaft (steering shaft), 26: lower shaft (steering shaft), 30: input shaft, 31: torsion bar, 31b: annular groove, 31c: second large diameter portion, 32: output shaft, 32b: second fitting surface, 33: connecting pin, 39: O-ring (elastic member), 50: torque sensor

Claims (1)

A steering shaft, an input shaft whose one end is rotationally connected to the other end of the steering shaft, a torsion bar whose one end is rotationally connected to the input shaft, and an output shaft which is rotationally connected to the other end of the torsion bar; A torque sensor for detecting steering torque from relative rotation between the input shaft and the output shaft; a steering tube for rotatably supporting the steering shaft; and the other end of the steering tube fixed to the input shaft and the output In the electric power steering apparatus comprising a housing that rotatably supports the shaft, the outer periphery of the output shaft is fitted to the outer periphery of the other end of the torsion bar, and the gap of the gap-fitted portion is filled. A ring-shaped elastic member is inserted between the inner periphery of the output shaft and the outer periphery of the torsion bar, and the output shaft Preliminary the torsion bar, the electric power steering apparatus characterized by the rotating coupled through a coupling pin disposed in a radial direction of the output shaft.

Images