JP6335730B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

  When an impact load is applied to the vehicle, a so-called secondary collision occurs in which the driver collides with the steering wheel. In order to alleviate the secondary collision, for example, as shown in Patent Document 1, when an impact of a certain level or more is applied, the input shaft, which is a component of the steering shaft, moves in the axial direction. An absorbing shock absorbing electric power steering device (EPS) has been developed. For example, an input shaft that moves due to an impact enters the inside of a torque sensor provided in the sensor housing.

JP2013-233879A

  However, when adopting a configuration in which the input shaft enters the inside of the torque sensor, a space for the input shaft to enter is provided outside the lower shaft. For this reason, a space corresponding to the wall thickness of the input shaft called an air gap is generated between the sensor element of the torque sensor and the lower shaft that is the detection target. For example, when a magnetic detection element is used as the sensor element, the detection accuracy of the sensor element decreases as the distance from the detection target increases. Therefore, the structure which can set the air gap between a sensor element and a detection target smaller is desired.

  An electric power steering apparatus that can achieve the above object has a first shaft having a first hollow portion that is open at one end and closed at the other end, and a second hollow portion that is open at one end and closed at the other end. A second shaft, a torsion bar that connects the first shaft and the second shaft, and the first shaft that is provided in the vicinity of the outer peripheral surface of the first and second shafts and that is applied when steering torque is applied. And a sensor for detecting a relative position change between the first shaft and the second shaft. The first end of the torsion bar is held in a state of being inserted into the first hollow part, while the second end of the torsion bar is fixed to the inner bottom surface of the second hollow part. Yes. When the holding state of the torsion bar with respect to the first hollow portion is released, the first shaft is a space formed between the inner peripheral surface of the second hollow portion and the outer peripheral surface of the torsion bar. Can enter.

  According to this configuration, since the second shaft has a space for inserting the first shaft, the holding state of the torsion bar with respect to the first hollow portion is released, whereby the second shaft Is movable in the direction of insertion or withdrawal from the first shaft. The sensor can detect changes in their relative positions in the vicinity of the first shaft and the second shaft. Conventionally, since the sensor is provided at a position away from the second shaft by the thickness of the first shaft, the air gap is increased by the thickness of the first shaft. In the present embodiment, the sensor can be provided at a position closer to the detection target, and the air gap between the sensor and the detection target can be set small.

  The sensor is provided on an outer peripheral surface of the first shaft or the second shaft, and an annular magnet that generates magnetism, and a relative position change between the first shaft and the second shaft. A magnetic detection element that generates an electrical signal corresponding to the change in magnetism.

  According to this configuration, the magnetic detection element can detect a change in magnetism due to a relative position change between the first shaft and the second shaft, and can generate an electrical signal corresponding to the change in magnetism. In particular, in the case of a magnetic detection element, the magnetism attenuates in inverse proportion to the square of the distance, so that the detection accuracy of the magnetic detection element becomes lower as the air gap is larger. When the magnetic detection element is employed, setting the air gap small has a great effect on improving accuracy.

  A holding member is provided between the torsion bar and the first shaft to hold the first end of the torsion bar inserted in the first hollow portion. The holding state of the torsion bar with respect to the first hollow portion by the holding member when an external force that releases the holding state by the holding member toward the entry direction with respect to the space is applied to the first shaft. Is released.

  According to this configuration, when an external force that releases the holding state of the holding release unit is applied, the first shaft enters the space. As a cause of generation of the external force, for example, a secondary collision can be cited. Even if the driver collides with the steering wheel due to the secondary collision, the load on the driver can be reduced by the first shaft entering the space. This is because the steering wheel moves from the original position in the insertion direction of the first shaft by the amount of insertion of the first shaft.

  The holding member is a pin that connects the first shaft and the torsion bar by being driven in a radial direction between the first shaft and the first end portion of the torsion bar. When an external force exceeding the breaking strength of the pin is applied as the external force, the holding state of the torsion bar with respect to the first hollow portion is released by breaking the pin.

  A recess is provided in the vicinity of the pin on at least one of the inner peripheral surface of the first shaft and the outer peripheral surface of the torsion bar at the boundary between the inner peripheral surface of the first shaft and the inner peripheral surface of the torsion bar. It is preferred that

  According to these configurations, the first shaft and the first end portion of the torsion bar can be connected by providing the pin as the holding release portion. Furthermore, by providing the recess, the pin can be bent and easily broken. When an external force is applied to release the holding state of the holding release portion provided in this way, the holding state of the torsion bar with respect to the first hollow portion is released.

  The magnet is preferably provided so as to be slidable along the axial direction of the first shaft with respect to the outer peripheral surface of the first shaft that is thinner than the outer diameter of the second shaft. When the first shaft is inserted into the space, the magnet is prevented from moving in the insertion direction of the first shaft by contacting the opening end surface of the second shaft. It acts as a brake that prevents insertion of the first shaft by sliding relative to the outer peripheral surface of the shaft along the axial direction of the first shaft.

  According to this configuration, when the first shaft moves in the insertion direction, a frictional force is generated between the magnet and the first shaft. This frictional force acts in a direction that prevents insertion of the first shaft, and suppresses movement of the first shaft in the insertion direction. An external force applied to the first shaft can be absorbed or attenuated.

  At least one of the outer peripheral surface of the first shaft and the inner peripheral surface of the second shaft has a tapered surface. When the tapered surface is provided on the outer peripheral surface of the first shaft, the tapered surface is reduced in diameter as it approaches one end of the first shaft that is open, and the tapered surface is formed inside the second shaft. When provided on the peripheral surface, the tapered surface expands in diameter as it approaches one end of the second shaft that is open.

According to this configuration, the tapered surface serves as a guide when the first shaft is inserted into the space. Therefore, the first shaft can be smoothly inserted into the space.
A gas that is a fluid is sealed in the space. As the first shaft is inserted into the space, movement of the first shaft in the insertion direction is suppressed by a reaction force generated by compressing the gas.

  According to this configuration, when the first shaft is inserted into the space, the reaction force is generated due to the compression of the gas by sealing the gas in the space for inserting the first shaft. Since this reaction force acts in a direction that prevents gas compression, the first shaft is prevented from being inserted into the space. This reaction force absorbs or attenuates the external force applied to the first shaft.

  When gas is employed as the fluid, it is preferable that a safety valve is provided so as to penetrate the outer peripheral surface and the inner peripheral surface of the second shaft. When the pressure of the space becomes equal to or higher than the specified value of the safety valve due to the compression of the gas, the fluid inside the space is released to the outside by opening the safety valve.

  According to this configuration, when the gas is compressed by inserting the first shaft into the space, if the pressure in the space is too high, the input shaft 23a may not be inserted into the lower shaft 23b any more. When the pressure in the space exceeds the specified value of the safety valve, the gas in the space is released to the outside by opening the safety valve. Thereby, the pressure inside the space can be lowered. Therefore, a sufficient shock absorbing stroke can be ensured.

Oil that is a fluid may be sealed in the space. An orifice is provided on the outer peripheral surface of the second shaft.
Specifically, oil or gas is used as the fluid. For example, an external force that releases the holding state of the holding release unit can be attenuated by the viscous resistance of the oil.

It is also possible to control shock absorption by the fluid by changing the characteristics of the fluid by adding an external factor to the fluid.
According to this configuration, the shock absorption characteristic can be controlled by changing the compression characteristic of the fluid by an external factor such as electricity.

  A steering wheel is provided at the axial end of one of the first shaft and the second shaft. The position of the steering wheel in the axial direction is changed by moving the first shaft in the insertion direction or the drawing direction relative to the space.

  According to this configuration, the steering wheel provided on the axis of the first shaft can be moved in the axial direction by moving the first shaft in the insertion or extraction direction. Therefore, it can be used as telescopic steering according to the driver's request.

  A spring may be provided in a state where the torsion bar is inserted between the inner bottom surface of the first hollow portion and the opening end surface of the second shaft in the space. When the first shaft is moved in the insertion direction, the spring exerts an elastic force in a direction that relaxes the movement in the insertion direction, and when the first shaft is moved in the extraction direction, the spring The axial movement of the steering wheel is assisted by exerting an elastic force in a direction assisting the movement in the pulling direction.

  According to this configuration, the movement of the steering wheel in the axial direction is assisted by the elastic force of the spring. For this reason, the driver can smoothly adjust the position of the steering wheel.

The effective length of the torsion bar that can be twisted can be adjusted by moving the first shaft in the insertion direction or the extraction direction with respect to the space.
According to this configuration, the effective length that the torsion bar can be twisted can be changed by adjusting the amount of insertion of the first shaft into the second shaft. Therefore, the rigidity of the steering wheel can be set according to the driver's preference.

  According to the electric power steering device of the present invention, the air gap between the sensor element and the detection target can be set smaller.

The block diagram which shows the structure of the steering device in one embodiment. (A) Schematic diagram of a column shaft in one embodiment, (b) An enlarged view of a connection portion between an input shaft and a torsion bar in one embodiment, (c) A schematic diagram of a column shaft in one embodiment. The schematic diagram of the column shaft in one embodiment. The schematic diagram of the column shaft in one embodiment. (A) Schematic diagram of the column shaft in one embodiment, (b) Schematic diagram of the column shaft in one embodiment. The schematic diagram of the column shaft in one embodiment. The schematic diagram of the column shaft in one embodiment.

  Hereinafter, an embodiment of an electric power steering device for a vehicle will be described. Here, a so-called dual pinion assist type electric power steering device (DP-EPS) is taken as an example.

  As shown in FIG. 1, the EPS 10 is provided to the steering mechanism 20 that steers the steered wheels 29 based on the operation of the driver's steering wheel 21, the assist mechanism 30 that assists the driver's steering operation, and the steering wheel 21. A torque sensor 50 for detecting a steering torque.

  The steering mechanism 20 includes a steering wheel 21 and a steering shaft 22 that rotates integrally with the steering wheel 21. The steering shaft 22 includes a column shaft 23 connected to the steering wheel 21, an intermediate shaft 24 connected to the lower end portion of the column shaft 23, and a first pinion shaft 25 connected to the lower end portion of the intermediate shaft 24. Have. The lower end portion of the first pinion shaft 25 meshes with a rack shaft 26 (more precisely, the rack teeth 26a) extending in the direction intersecting the first pinion shaft 25. Therefore, the rotational motion of the steering shaft 22 is converted into a reciprocating linear motion in the axial direction of the rack shaft 26 via the first rack and pinion mechanism 27 including the first pinion shaft 25 and the rack shaft 26. The reciprocating linear motion is transmitted to the left and right steered wheels 29 via tie rods 28 respectively connected to both ends of the rack shaft 26, whereby the steered angle of the steered wheels 29 changes.

  The assist mechanism 30 includes a motor 31 that is a source of assist force, a worm shaft 32 coupled to the motor 31, a worm wheel 33 that meshes with the worm shaft 32, and a second pinion shaft 34 that rotates integrally with the worm wheel 33, And an ECU 40 for controlling the motor 31. The lower end portion of the second pinion shaft 34 meshes with the rack shaft 26 (more precisely, the rack teeth 26b). Therefore, the rotational motion of the second pinion shaft 34 is converted into a reciprocating linear motion in the axial direction of the rack shaft 26 via the second rack and pinion mechanism 27 a including the second pinion shaft 34 and the rack shaft 26. That is, the steering operation of the driver is assisted by applying an assist force in the axial direction of the rack shaft 26 by the motor 31. The ECU 40 is provided, for example, in a housing that houses components of the assist mechanism 30 and controls the motor 31 based on the detection result of the torque sensor 50.

  The torque sensor 50 is provided on the column shaft 23. The torque sensor 50 detects a steering torque τ applied to the steering shaft 22 in accordance with the driver's steering operation.

  As shown in FIG. 2A, the column shaft 23 has a structure in which an input shaft 23a on the steering wheel 21 side and a lower shaft 23b on the intermediate shaft 24 side are connected to both ends of the torsion bar 23c. Each of the input shaft 23a and the lower shaft 23b has a hollow cylindrical shape with one end opened. The input shaft 23a and the lower shaft 23b have hollow portions 23ah and 23bh, respectively. These hollow portions 23ah and 23bh are opened to one end of the input shaft 23a and the lower shaft 23b. The torsion bar 23c is a solid bar. The inner diameter of the input shaft 23a is set slightly larger than the outer diameter of the torsion bar 23c, and the outer diameter of the input shaft 23a is set slightly smaller than the inner diameter of the hollow portion 23bh of the lower shaft 23b. A torsion bar 23c is inserted into the hollow portion 23bh of the lower shaft 23b. The torsion bar 23c is fixed to the inner bottom surface of the hollow portion 23bh. The torsion bar 23c is coaxial with the lower shaft 23b. The end of the input shaft 23a on the hollow portion 23ah side is inserted into the hollow portion 23bh of the lower shaft 23b, whereby the torsion bar 23c is inserted into the hollow portion 23ah of the input shaft 23a. However, the input shaft 23a is not completely inserted into the lower shaft 23b, and a gap 23f exists in the axial direction between the input shaft 23a and the lower shaft 23b (the inner bottom surface of the hollow portion 23bh). At that time, a gap 23g exists between the torsion bar 23c and the input shaft 23a (hollow portion 23ah) in the axial direction. The gap 23f and the gap 23g are spaces for inserting the input shaft 23a into the lower shaft 23b. The outer peripheral surface of the input shaft 23a is in contact with the inner peripheral surface of the lower shaft 23b. The outer peripheral surface of the torsion bar 23c is in contact with the inner peripheral surface of the input shaft 23a. The input shaft 23a rotates relative to the lower shaft 23b.

  As shown in FIG. 2B, the input shaft 23a and the torsion bar 23c are fixed by, for example, metal pins 23d. The pin 23d is press-fitted into a pin hole 23h that passes through the input shaft 23a and the torsion bar 23c in the radial direction (direction perpendicular to the axis m). The movement of the input shaft 23a in the axis m direction is restricted by the pin 23d. On the inner peripheral surface of the input shaft 23a, a recess 23e is provided near the opening of the pin hole 23h. The recess 23e is preferably provided on the opposite side to the insertion direction of the input shaft 23a with respect to the hollow portion 23bh in the axis m direction (right side in the figure). The recess 23e serves as a space for the pin 23d to bend when a load P directed to the lower shaft 23b is applied to the input shaft 23a. For example, a curved surface is set as the shape of the recess 23e.

  As shown in FIG. 2A, a cylindrical multipolar magnet 51 in which the magnetic poles of the N pole and the S pole are alternately arranged in the circumferential direction is provided on the outer peripheral surface of the input shaft 23a. The multipolar magnet 51 is fixed to the outer peripheral surface of the input shaft 23a in a press-fitted state. A cylindrical first rotary yoke 52 is fixed to the outer peripheral surface of the input shaft 23a, and a cylindrical second rotary yoke 53 is fixed to the outer peripheral surface of the lower shaft 23b in a press-fit state. The first rotating yoke 52 and the second rotating yoke 53 are provided so as to face each other with a gap therebetween so as to sandwich the multipolar magnet 51 in the axis m direction. Therefore, the multipolar magnet 51 and the first rotating yoke 52 rotate integrally with the input shaft 23a. The second rotating yoke 53 rotates integrally with the lower shaft 23b. The lower shaft 23 b and the second rotating yoke 53 are slidably rotated with respect to the multipolar magnet 51.

  A cylindrical first fixed yoke 54 is provided with a slight gap (air gap) with respect to the outer peripheral surface of the first rotating yoke 52, and a slight gap (air gap) with respect to the outer peripheral surface of the second rotating yoke 53. A cylindrical second fixed yoke 55 is provided at a distance. The first and second fixed yokes 54 and 55 face each other in the direction of the axis m. The first fixed yoke 54 and the second fixed yoke 55 are provided, for example, in a sensor housing (not shown). A hole as an example of a magnetic detection element (sensor element) is provided between the first fixed yoke 54 and the second fixed yoke 55 (more precisely, between two projecting pieces provided on the outer peripheral surface thereof). An element 56 is provided. The detection target of the hall element 56 is the first and second rotary yokes 52 and 53 that change the magnetic flux density in accordance with the relative rotational displacement between the input shaft 23a and the lower shaft 23b.

The operation of the electric power steering device of the present embodiment described above will be described.
When the steering wheel 21 is rotated, a steering torque τ acts on the input shaft 23a. When the steering torque τ is transmitted from the input shaft 23a to the lower shaft 23b via the torsion bar 23c, torsional deformation occurs in the torsion bar 23c. When a relative rotational displacement occurs between the input shaft 23a and the lower shaft 23b, the positional relationship between the first and second rotating yokes 52 and 53 and the multipolar magnet 51 changes, and the first and second yokes 54, The magnetic flux density acting on 55 also changes. Therefore, since the magnetic flux density acting on the Hall element 56 also changes, the Hall voltage output from the Hall element 56 changes corresponding to the acting magnetic flux density. From the hall voltage, the ECU 40 calculates the torsion angle of the torsion bar 23c.

  Corresponding to the rotational displacement of the input shaft 23a and the lower shaft 23b, the magnetic flux density applied from the multipolar magnet 51 to the first and second rotary yokes 52, 53 is slightly lower than that of the first and second rotary yokes 52, 53. The first and second fixed yokes 54 and 55 arranged apart from each other act with almost no air gap.

  Here, for example, a configuration in which the input shaft 23a is inserted between the lower shaft 23b and the hall element 56 may be adopted. In this case, the first and second rotary yokes 52 and 53 and the first and second It is necessary to provide an air gap between the fixed yokes 54 and 55 by the thickness of the input shaft 23a. In this regard, in the present embodiment, there is no air gap due to the thickness of the input shaft 23a. Therefore, the magnetic flux density generated in the first and second rotating yokes 52 and 53 acts on the Hall element 56 provided between the first and second fixed yokes 54 and 55 with almost no air gap. . Therefore, the torsion angle of the torsion bar 23c can be detected with high accuracy.

  In particular, when a magnetic detection element is used as the sensor element, it is important that the air gap is small. This is because the magnetic flux density, which is a physical quantity detected by the magnetic detection element, is inversely proportional to the square of the distance. If the distance to the detection target is increased, a smaller change in magnetic flux density must be detected. Therefore, when an error in the magnetic flux density is added due to noise or the like, the influence of noise on the detection result of the magnetic detection element becomes larger.

  For example, when the vehicle collides with an obstacle in front, a force that pushes the driver of the vehicle forward acts as a reaction. For this reason, a so-called secondary collision occurs in which the driver of the vehicle collides with the steering wheel 21. Due to the secondary collision, the load P acts on the steering wheel 21, and then the load P acts on the input shaft 23a.

  The torsion bar 23c is fixed to the lower shaft 23b, and the lower shaft 23b is supported by the rack housing 26c via the intermediate shaft 24 and the first pinion shaft 25. For this reason, the position of the lower shaft 23b basically does not change. Therefore, as shown in FIG. 2B, when a load P acts on the input shaft 23a due to a secondary collision or the like, a shear stress acts on the pin 23d that fixes the input shaft 23a and the torsion bar 23c. When the load P is above a certain level, the pin 23d is destroyed. The pin 23d is easily broken when a shearing stress is applied by the recess 23e provided in the input shaft 23a. The recess 23e functions as a space where the pin 23d can be deformed when the load P is applied. Since the concave portion 23e is provided, the solid portion of the input shaft 23a does not exist in that portion. Therefore, the pin 23d does not have to be deformed by pushing the input shaft 23a when the load P is applied. Therefore, the pin 23d can be easily broken compared with the case where the recess 23e is not provided. By setting the shape of the recess 23e so that the pin 23d is broken when the load P is applied, the load P at which shock absorption starts can be controlled.

  Therefore, the movement of the input shaft 23a in the direction of the axis m, which is normally restricted by the pin 23d, can be performed by breaking the pin 23d. Further, since the gap 23f and the gap 23g are formed, a space for the input shaft 23a to expand and contract in the direction of the axis m is also secured. For this reason, when a load P exceeding a certain level is applied during the secondary collision, the input shaft 23a enters the lower shaft 23b as shown in FIG. 2 (c).

  At this time, the torsion bar 23c also functions as a guide when the input shaft 23a is inserted into the lower shaft 23b, and the input shaft 23a is smoothly inserted into the gap 23f. As the input shaft 23a is inserted into the lower shaft 23b, a frictional force is generated between the outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b. As the input shaft 23a is inserted into the lower shaft 23b, a frictional force is also generated between the inner peripheral surface of the input shaft 23a and the outer peripheral surface of the torsion bar 23c. These frictional forces act in a direction that prevents the input shaft 23a from being inserted into the lower shaft 23b. Therefore, as the input shaft 23a is inserted into the lower shaft 23b, the load P acting on the input shaft 23a is reduced (damped), and the load on the driver (load acting as an impact reaction) is reduced.

  Furthermore, it can be expected that the load P is reduced by the multipolar magnet 51. When the load P acts on the input shaft 23a, the movement of the multipolar magnet 51 in the direction of the axis m is restricted by the lower shaft 23b. For this reason, the input shaft 23 a enters the lower shaft 23 b while sliding with respect to the inner peripheral surface of the multipolar magnet 51. When the pin 23d is broken and the input shaft 23a starts to be inserted into the lower shaft 23b, a frictional force is generated between the multipolar magnet 51 and the input shaft 23a. This frictional force also acts in a direction that prevents insertion of the input shaft 23a. As shown in FIG. 2C, the input shaft 23a is preferably stopped before the input shaft 23a collides with the bottom surface of the lower shaft 23b.

According to this embodiment, the following effects can be obtained.
(1) The air gap can be set smaller than that of a conventional shock absorbing electric power steering device in which an air gap corresponding to the thickness of the input shaft exists between the sensor element and the lower shaft to be detected. It becomes. In the case of a conventional shock absorbing electric power steering device, the air gap is increased by the thickness of the input shaft 23a. As the air gap is set smaller, the magnetic flux density is not attenuated and acts on a magnetic detection element such as a Hall element. For this reason, detection accuracy can be further improved.

  (2) When the load P exceeding a certain level is applied, the pin 23d is broken, whereby the input shaft 23a can be inserted into the lower shaft 23b. By inserting the input shaft 23a, it is possible to secure a longer stroke for absorbing the impact. Further, since it is not necessary to provide a separate shock absorbing mechanism in order to ensure a constant shock absorbing stroke, the length of the steering shaft 22 can be set short, and the EPS 10 can be downsized. Therefore, the vehicle space can be utilized more effectively.

  (3) The impact caused by the secondary collision can be absorbed by the frictional force acting between the input shaft 23a and the lower shaft 23b acting during the shock absorbing stroke. Furthermore, the impact caused by the secondary collision can be absorbed by the frictional force acting between the multipolar magnet 51 and the input shaft 23a. Therefore, the load acting on the driver can be further reduced.

<Second Embodiment>
Next, a second embodiment of the electric power steering device will be described. Here, the difference from the first embodiment will be mainly described.

  As shown in FIG. 3, as an example, a tapered surface 60 is provided in the hollow portion 23bh of the lower shaft 23b. The tapered surface 60 is provided over a certain range from the open end surface of the hollow portion 23bh to the inner bottom surface of the hollow portion 23bh in the lower shaft 23b. The taper surface 60 decreases in diameter toward the inner bottom surface of the hollow portion 23bh. The inner diameter of the lower shaft 23b excluding the tapered surface 60 in a certain range is set slightly larger than the outer diameter of the input shaft 23a. When the input shaft 23a is inserted into the lower shaft 23b, the outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b slide with each other. In a state where the input shaft 23a is fixed to the torsion bar 23c by the pin 23d, the inclination angle of the tapered surface 60 with respect to the axis m is set so that the input shaft 23a does not contact the lower shaft 23b.

Next, the operation of this embodiment will be described. In addition, about the same effect | action as 1st Embodiment, it abbreviate | omits.
By providing the tapered surface 60, the input shaft 23a is maintained in a state of not contacting the lower shaft 23b until a load P that shears and breaks the pin 23d is applied to the input shaft 23a. When the load P acts on the input shaft 23a due to the secondary collision and the pin 23d is broken, the input shaft 23a is pushed into the lower shaft 23b. When the input shaft 23a has rattling or the like, the input shaft 23a contacts the tapered surface 60. In this case, the input shaft 23a is smoothly inserted into the hollow portion 23bh by being guided by the tapered surface 60.

  As the input shaft 23a is inserted into the hollow portion 23bh, the frictional force generated between the outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b, and the inner peripheral surface of the input shaft 23a and the torsion bar 23c The impact caused by the secondary collision is absorbed by the frictional force generated between the outer peripheral surface and the outer peripheral surface.

Next, the effect of this embodiment will be described.
(1) By adjusting the position where the input shaft 23a and the lower shaft 23b are in contact with each other, the gradient of the tapered surface 60, and the like, it is possible to control the position where the impact is to be absorbed. Further, the tapered surface 60 can be expected to serve as a guide when the input shaft 23a is pushed into the lower shaft 23b.

<Third Embodiment>
Next, the structure of 3rd Embodiment of an electric power steering apparatus is demonstrated.
As shown in FIG. 4, the gap 23f is filled with a gas as a fluid. A safety valve 61 is provided on the peripheral wall of the lower shaft 23b. The safety valve 61 is provided so as to penetrate the inner peripheral surface and the outer peripheral surface of the lower shaft 23b. When the clearance 23f is lower than a certain pressure, the safety valve 61 is closed, so that no gas enters and exits between the inner peripheral surface and the outer peripheral surface of the lower shaft 23b. Therefore, gas does not enter and exit between the gap 23f and the outside. In addition, when the gap 23f is at a certain pressure or higher, the safety valve 61 is opened. As a result, the gas inside the gap 23f is released to the outside, and the pressure in the gap 23f decreases. When the safety valve 61 is opened and becomes lower than a certain pressure in the gap 23f, the safety valve 61 is closed, so that the release of gas from the gap 23f is restricted.

  The outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b are in sufficient contact, and the gap 23f is sealed. A certain sealing device may be provided between the outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b. For this reason, the gas inside and outside the gap 23f enters and exits only by the safety valve 61.

Next, the operation of this embodiment will be described.
When the load P at which the pin 23d is sheared and broken by the secondary collision acts, the input shaft 23a starts to be pushed into the lower shaft 23b. Since the gas in the gap 23f is compressed, the pressure in the gap 23f increases. At this time, the pressure in the gap 23f acts in a direction that prevents gas compression, and thus acts in a direction that prevents the input shaft 23a from being inserted into the lower shaft 23b. As a result, the gas filled in the gap 23f is compressed, so that the impact load is attenuated or absorbed.

  Furthermore, if the gas filled in the gap 23f is greatly compressed by the input shaft 23a being pushed into the lower shaft 23b, the pressure in the gap 23f may increase. If the pressure in the gap 23f is too high, the input shaft 23a may not be inserted into the lower shaft 23b any more. As a result, the shock cannot be absorbed by fully utilizing the shock absorbing stroke of the gap 23f. However, when the gap 23f reaches a certain pressure or higher, the safety valve 61 is opened, and the gas filled in the gap 23f is released to the outside. Therefore, it is possible to ensure a sufficient shock absorbing stroke in the gap 23f of the input shaft 23a.

Next, the effect of this embodiment will be described.
(1) The repulsive force generated when the gas is compressed prevents the input shaft 23a from being pushed into the lower shaft 23b. Therefore, the impact load is attenuated or absorbed by the gas being compressed.

  (2) When the gas in the gap 23f is sufficiently compressed so that the gap 23f becomes a certain pressure or higher, the pressure of the gap 23f can be lowered by the safety valve 61. Therefore, it is possible to sufficiently ensure the shock absorbing stroke of the input shaft 23a in the gap 23f.

<Fourth Embodiment>
Next, the configuration of the fourth embodiment will be described. This example differs from the first embodiment in that it has a telescopic function.

  As shown in FIG. 5A, a spring 62 is provided in the gap 23g provided in the input shaft 23a. The springs 62 are provided along the direction of the axis m, and both ends of the springs 62 are connected to the input shaft 23a (the inner bottom surface of the hollow portion 23ah) and the torsion bar 23c, respectively. The diameter of the spring 62 is set smaller than the inner diameter of the hollow portion 23ah. A spring 63 is provided in a gap 23f provided between the input shaft 23a and the lower shaft 23b. The spring 63 is provided along the direction of the axis m, and both ends of the spring 63 are connected to the input shaft 23a (the inner bottom surface of the hollow portion 23ah) and the lower shaft 23b, respectively. The diameter of the spring 63 is set larger than the outer diameter of the torsion bar 23c and smaller than the inner diameter of the hollow portion 23bh.

  Although the outer peripheral surface of the input shaft 23a and the inner peripheral surface of the lower shaft 23b are in contact with each other, it is preferable that the frictional resistance between them is set as small as possible. In the first embodiment, when the input shaft 23a is inserted into the lower shaft 23b, the multipolar magnet 51 has an effect of applying a frictional force in a direction that prevents the input shaft 23a from being inserted. The magnet 51 is provided slightly apart from the input shaft 23a so that almost no frictional force acts between the magnet 51 and the input shaft 23a.

  The input shaft 23a and the torsion bar 23c are fixed by pins 64 provided in a direction perpendicular to the axis m. The lower shaft 23b is provided with a plurality of holes 65 along the direction of the axis m. The hole 65 penetrates in the radial direction of the lower shaft 23b. The input shaft 23a is provided with a plurality of holes 66 along the direction of the axis m. The hole 66 penetrates in the radial direction of the input shaft 23a. The torsion bar 23c is provided with a plurality of holes 67 along the axis m direction. The hole 67 penetrates in the radial direction of the torsion bar 23c. The pitches (arrangement intervals) in the direction of the axis m of the holes 65 to 67 are the same. By adjusting the insertion depth of the input shaft 23a with respect to the lower shaft 23b, the holes 65 to 67 are aligned in a direction perpendicular to the axis m. The pin 64 is inserted into the holes 65 to 67 that coincide in the direction of the axis m. By adjusting the position where the pin 64 is inserted, the position where the input shaft 23a and the torsion bar 23c are fixed can be adjusted.

Next, the operation of this embodiment will be described.
When the driver and the steering wheel 21 are too close to each other, the driver removes the pin 64 and directs the steering wheel 21 toward the back side in the direction of the axis m (the lower shaft 23b side) with a certain force applied. Good. The input shaft 23 a is pushed into the lower shaft 23 b against the elastic force of the spring 63. When the input shaft 23a is inserted into the lower shaft 23b, the sudden insertion of the input shaft 23a due to the elastic force of the spring 63 is suppressed.

  When the position of the driver and the steering wheel 21 is too far, the driver only needs to remove the pin 64 and pull the steering wheel 21 toward the front side (driver side) in the direction of the axis m by applying a certain force. . When the input shaft 23a moves from the lower shaft 23b in the pulling direction, the elastic force of the spring 63 suppresses the input shaft 23a from moving suddenly in the pulling direction. After adjusting the position of the steering wheel 21, the input shaft 23 a and the lower shaft 23 b are fixed again by the pins 64.

  In addition to the position adjustment of the steering wheel 21, the fixing position of the input shaft 23a and the lower shaft 23b may be changed from the following viewpoint. That is, by adjusting the holes 65, 66, and 67 into which the pins 64 are inserted, the position where the input shaft 23a and the torsion bar 23c are fixed, that is, the twistable length L of the torsion bar 23c is changed. Therefore, the length that the torsion bar 23c can be twisted as shown in FIG. 5 (a) can be set as the length L2, or as shown in FIG. 5 (b). L2 is set longer than L3.

  The spring rate (spring constant) of the torsion bar 23c can be changed by adjusting the twistable length L of the torsion bar 23c. The spring rate is the hardness of the spring. The shorter the length L, the greater the spring rate and the less likely it is to be deformed. The greater the spring rate, the greater the rigidity when the steering wheel 21 is steered.

Next, the effect of this embodiment will be described.
(1) Since the gap 23f is provided, the steering wheel 21 can be moved in the direction of the axis m of the steering shaft 22 in accordance with the driver's preference like so-called telescopic steering.

  (2) By providing the springs 62 and 63, it is possible to prevent the input shaft 23a from being suddenly inserted into and pulled from the lower shaft 23b by a telescopic operation.

  (3) The rigidity of the steering wheel 21 can be changed by changing the spring rate of the torsion bar 23c according to the driver's preference. Therefore, the steering characteristics can be changed according to the driver's preference.

Each embodiment may be changed as follows. The following other embodiments can be combined with each other within a technically consistent range.
In the first to third embodiments, the multipolar magnet 51 is provided so as to contact the input shaft 23a, but the contact resistance (sliding resistance) may be set as appropriate. Further, the multipolar magnet 51 may be provided so as not to contact the input shaft 23a.

In each embodiment, the ECU 40 is provided in the assist mechanism 30, but may be provided anywhere in the vehicle.
In each embodiment, the input shaft 23a and the torsion bar 23c are fixed by the pins 23d and 64, but may be fixed by another fixing method. For example, serration connection or spline connection may be used. Even in this case, the input shaft 23a and the lower shaft 23b rotate integrally. However, in the first to third embodiments, the movement of the input shaft 23a and the torsion bar 23c in the direction of the axis m is restricted during normal times, and the movement of the input shaft 23a and the torsion bar 23c in the direction of the axis m is restricted during a secondary collision. It needs to be released.

  -In 2nd Embodiment, although the taper surface 60 was provided in the inner peripheral surface of the lower shaft 23b, you may provide in the outer peripheral surface of the input shaft 23a. Further, instead of the tapered surface 60, it may be a curved surface 68 as shown in FIG. The curved surface 68 also increases in diameter toward the opening end surface of the lower shaft 23b.

  In the first to third embodiments, the recess 23e for facilitating the shear failure of the pin 23d is provided in the input shaft 23a, but the recess 23e may be provided in the torsion bar 23c. Further, the recess 23e may not be provided, and for example, a portion that is easily broken by shear may be provided in the pin 23d. Further, in the first to third embodiments, the pin 23d is described as being sheared, but there may be different modes of destruction. For example, the pin 23d may be broken by tensile fracture. In addition, the pin 23d may not be destroyed, but the pin 23d may come off, and the input shaft 23a and the torsion bar 23c may be unfixed.

  In the third embodiment, the shock absorption may be controlled by changing the physical properties such as the compression characteristics of the fluid filled in the gap 23f by an external factor such as electricity. For example, as shown in FIG. 7, two electrodes 69 and 70 are provided on the inner peripheral wall of the lower shaft 23b so as to face each other with the torsion bar 23c interposed therebetween. The two electrodes 69 and 70 are each connected to a power source 71. Normally, the two electrodes 69 and 70 are set so that there is no potential difference due to the power source 71. When the load P is applied due to the secondary collision, a predetermined voltage by the power source 71 is applied between the two electrodes 69 and 70. Then, an electric field acts on the fluid inside the gap 23f. As an example, when the fluid filled in the gap 23f is an electrolyte, gas is generated by electrolysis of the electrolyte. In this case, the amount by which the electrolytic solution is electrolyzed is closely related to the potential difference of the power source 71. In general, since the density of gas is lower than that of liquid, the pressure inside the gap 23f is increased. As a result, the repulsive force generated when the fluid in the gap 23f is compressed can be increased, and the impact when the input shaft 23a is pushed into the lower shaft 23b can be absorbed. In this case, by adjusting the voltage applied between the electrodes 69 and 70, the amount of gas generated can be adjusted, and the shock absorption can be controlled.

  -In 3rd Embodiment, the structure which relieves an impact actively, for example using the oil as a fluid may be sufficient. Specifically, it can be considered to have a structure such as a shock absorber or a gas spring. In that case, first, the input shaft 23a is inserted into the lower shaft 23b by the secondary impact, the oil in the gap 23f is compressed, and the pressure in the gap 23f increases. Next, the oil is discharged from, for example, an orifice provided in the lower shaft 23b, and impact energy is converted into thermal energy by the viscous resistance of the oil at that time. By adjusting the viscosity resistance of the oil, the shock absorption can be adjusted. The damping force for absorbing the impact is not limited to viscous resistance.

  In the third embodiment, the gap 23f may not be filled with gas in advance. For example, a sealed container in which a fluid is sealed may be provided in the gap 23f. The sealed container is broken when a load of a certain level or more is applied, and the gas sealed in the sealed container is released to the outside.

  In the first to third embodiments, the shock absorption may be further improved by providing an elastic member such as rubber in the gap 23f and the gap 23g. Moreover, in 4th Embodiment, although rapid insertion and extraction were suppressed with the springs 62 and 63, you may suppress with elastic members, such as rubber | gum.

In each embodiment, the Hall element 56 is provided as an example of the magnetic detection element. However, an MR sensor or a resolver may be used.
In each embodiment, the twist of the torsion bar 23c is detected using a magnetic detection element such as the Hall element 56, but is not limited to the magnetic detection element. For example, the twist of the torsion bar 23c may be detected by a potentiometer. Also in this case, the accuracy is improved by providing a potentiometer in the vicinity of the detection target.

  -In each embodiment, although the input shaft 23a was provided so that it might be inserted in the lower shaft 23b, the structure where the lower shaft 23b is inserted in the input shaft 23a conversely may be sufficient. In that case, the multipolar magnet 51 is provided on the outer peripheral surface of the lower shaft 23b.

In the first to third embodiments, the secondary collision is mainly assumed as the impact load, but any impact load may be used as long as the impact is along the axis m direction.
In each embodiment, the EPS 10 has a DP-EPS structure, but the EPS 10 may be any type of EPS.

  DESCRIPTION OF SYMBOLS 10 ... EPS, 20 ... Steering mechanism, 21 ... Steering wheel, 22 ... Steering shaft, 23 ... Column shaft, 23a ... Input shaft, 23b ... Lower shaft, 23c ... Torsion bar, 23d ... Pin, 23e ... Recess, 23f, 23g ... gap, 23h ... pin hole, 24 ... intermediate shaft, 25 ... first pinion shaft, 25a ... pinion teeth, 26 ... rack shaft, 26a ... rack teeth, 26b ... rack teeth, 26c ... rack housing, 27 ... first Rack and pinion mechanism, 27a ... second rack and pinion mechanism, 28 ... tie rod, 29 ... steering wheel, 30 ... assist mechanism, 31 ... motor, 32 ... worm shaft, 33 ... worm wheel, 34 ... second pinion shaft, 34a ... pinion teeth, 40 ... ECU, DESCRIPTION OF SYMBOLS 0 ... Torque sensor, 51 ... Multipolar magnet, 52 ... 1st rotation yoke, 53 ... 2nd rotation yoke, 54 ... 1st fixed yoke, 55 ... 2nd fixed yoke, 56 ... Hall element, 60 ... Tapered surface, 61 ... Safety valve, 62, 63 ... Spring, 64 ... Pin, 65, 66, 67 ... Hole, 68 ... Curved surface, 69, 70 ... Electrode, 71 ... Power source.

Claims (14)

A first shaft having a first hollow portion open at one end and closed at the other end;
A second shaft having a second hollow portion open at one end and closed at the other end;
A torsion bar connecting the first shaft and the second shaft;
A sensor that is provided in the vicinity of the outer peripheral surfaces of the first and second shafts and detects a relative position change between the first shaft and the second shaft accompanying application of steering torque;
The first end of the torsion bar is held in a state of being inserted into the first hollow part, while the second end of the torsion bar is fixed to the inner bottom surface of the second hollow part,
When the holding state of the torsion bar with respect to the first hollow portion is released, the first shaft is a space formed between the inner peripheral surface of the second hollow portion and the outer peripheral surface of the torsion bar. Electric power steering device that can enter the vehicle. The electric power steering apparatus according to claim 1, wherein
The sensor is an annular magnet that is provided on an outer peripheral surface of the first shaft or the second shaft and generates magnetism;
An electric power steering apparatus comprising: a magnetic detection element that generates an electric signal corresponding to the change in magnetism associated with a change in relative position between the first shaft and the second shaft. In the electric power steering device according to claim 1 or 2,
Provided between the torsion bar and the first shaft is a holding member that holds the first end portion of the torsion bar in a state inserted in the first hollow portion;
The holding state of the torsion bar with respect to the first hollow portion by the holding member when an external force that releases the holding state by the holding member toward the entry direction with respect to the space is applied to the first shaft. Electric power steering device that is released. In the electric power steering device according to claim 3,
The holding member is a pin that connects the first shaft and the torsion bar by being driven in a radial direction between the first shaft and the first end of the torsion bar;
When an external force exceeding the breaking strength of the pin is applied as the external force, the electric power steering device in which the holding state of the torsion bar with respect to the first hollow portion is released by breaking the pin. In the electric power steering apparatus according to claim 4,
A recess is provided in the vicinity of the pin on at least one of the inner peripheral surface of the first shaft and the outer peripheral surface of the torsion bar at the boundary between the inner peripheral surface of the first shaft and the inner peripheral surface of the torsion bar. An electric power steering device. In the electric power steering device according to any one of claims 2 to 5,
The magnet is provided to be slidable along the axial direction of the first shaft with respect to the outer peripheral surface of the first shaft that is thinner than the outer diameter of the second shaft,
When the first shaft is inserted into the space, the magnet is prevented from moving in the insertion direction of the first shaft by contacting the opening end surface of the second shaft. An electric power steering apparatus that acts as a brake that prevents insertion of the first shaft by sliding relative to the outer peripheral surface of the shaft along the axial direction of the first shaft. In the electric power steering device according to any one of claims 1 to 6,
At least one of the outer peripheral surface of the first shaft and the inner peripheral surface of the second shaft has a tapered surface,
When the tapered surface is provided on the outer peripheral surface of the first shaft, the tapered surface is reduced in diameter as it approaches one end of the first shaft that is open, and the tapered surface is formed inside the second shaft. The electric power steering device having a diameter that increases when approaching one end of the second shaft that is open when the tapered surface is provided on a peripheral surface. In the electric power steering device according to any one of claims 1 to 6,
The space is filled with a gas that is a fluid,
An electric power steering apparatus in which movement of the first shaft in the insertion direction is suppressed by a reaction force generated by the gas being compressed as the first shaft is inserted into the space. The electric power steering apparatus according to claim 8,
A safety valve is provided so as to penetrate the outer peripheral surface and the inner peripheral surface of the second shaft;
An electric power steering apparatus in which, when the pressure of the space becomes equal to or greater than a specified value of the safety valve due to the compression of the gas, the fluid in the space is released to the outside by opening the safety valve. In the electric power steering device according to any one of claims 1 to 6,
An electric power steering apparatus in which oil which is a fluid is sealed in the space, and an orifice is provided on an outer peripheral surface of the second shaft. In the electric power steering device according to any one of claims 8 to 10,
An electric power steering apparatus that controls shock absorption by the fluid by changing the characteristics of the fluid by adding an external factor to the fluid. In the electric power steering device according to any one of claims 1 to 3,
A steering wheel is provided at the axial end of one of the first shaft and the second shaft,
An electric power steering apparatus in which the position of the steering wheel in the axial direction is changed by moving the first shaft in the insertion direction or the drawing direction relative to the space. The electric power steering apparatus according to claim 12,
Between the inner bottom surface of the first hollow portion and the opening end surface of the second shaft in the space, a spring is provided in a state where the torsion bar is inserted,
When the first shaft is moved in the insertion direction, the spring exerts an elastic force in a direction that relaxes the movement in the insertion direction, and when the first shaft is moved in the extraction direction, the spring An electric power steering device that assists in the axial movement of a steering wheel by exerting an elastic force in a direction assisting movement in a pulling direction. In the electric power steering device according to claim 12 or 13,
An electric power steering device in which the effective length that the torsion bar can be twisted can be adjusted by moving the first shaft in an insertion direction or a drawing direction with respect to the space.