JP7316325B2 - steering device - Google Patents

Description

The present invention relates to steering devices.

Patent Literature 1 describes a rack-and-pinion steering device that includes a preload mechanism that presses a rack toward a pinion. The preload mechanism is constructed by sequentially inserting a rack guide, a preload spring, and an adjustment screw into the cylindrical portion of the housing. By biasing the rack guide toward the rack with the preload spring, the rack is pressed toward the pinion. This prevents backlash from occurring between the rack and pinion.

JP 2013-241051 A

A preload mechanism such as that described in Patent Document 1 may be configured, for example, to increase the biasing force of a preload spring to strongly press the rack toward the pinion in order to prevent the occurrence of abnormal noise due to backlash. Common. In this configuration, since the rack is strongly pressed against the pinion and is difficult to move, the load from the wheel is reversely input to the rack, which prevents the rack from contacting the pinion and the like, thereby preventing noise from being generated. It may get worse.

Moreover, the steering device described in Patent Document 1 is of a so-called single pinion type. It is also conceivable to apply a preload mechanism as described in Patent Document 1 to each of the two pinions of a dual pinion type steering device. In this case, in order to prevent the generation of abnormal noise due to backlash, each of the two pinions must be strongly pressed toward the rack, making it more difficult for the rack to move. Therefore, there is a possibility that the steering performance of the dual-pinion type steering device may deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to improve steerability while preventing abnormal noise from occurring in a dual-pinion steering device.

The present invention is a steering device, comprising: a first shaft member that rotates in response to steering of a steering member by a driver; a first pinion gear that is provided on the first shaft member and rotates together with the first shaft member; a second shaft member to be driven, a second pinion gear provided on the second shaft member and rotating together with the second shaft member, a rack shaft having a rack gear meshing with the first pinion gear and the second pinion gear, and steering a wheel; A case member that houses the rack shaft, a first biasing mechanism that biases the rack shaft toward the first pinion gear, and a second biasing mechanism that biases the rack shaft toward the second pinion gear, The case member has a first accommodating portion for accommodating the first biasing mechanism and a second accommodating portion for accommodating the second biasing mechanism, and the first biasing mechanism abuts against the rack shaft. and a first biasing member that biases the first contacting part toward the rack shaft, and a second biasing mechanism comprises a second contact portion that abuts against the rack shaft and is movable within the second accommodating portion following the movement of the rack shaft; a second biasing member that biases the second contact portion toward the rack shaft; and the first contact portion and the second contact portion move within the corresponding first housing portion and second housing portion by the case member as the amount of movement of the rack shaft that steers the wheels increases. It is characterized in that the first contact portion and the second contact portion become unable to follow the rack shaft and start to slide on the rack shaft at different timings.

In this aspect of the invention, the first contact portion of the first biasing mechanism and the second contact portion of the second biasing mechanism cannot follow the movement of the rack shaft and start to slide on the rack shaft at different timings. The rack shaft steers the wheels by moving while sliding with respect to each contact portion. Therefore, if the frictional force between each contact portion and the rack shaft is large, the steerability of the steering device is deteriorated. The frictional force is greater when each contact portion is stationary with respect to the rack shaft than when each contact portion is sliding with respect to the rack shaft. That is, the total amount of frictional force between each contact portion and the rack shaft when each contact portion is stationary with respect to the rack shaft is greater than when each contact portion is sliding with respect to the rack shaft. Become. Therefore, by allowing one of the contact portions to start slipping on the rack shaft first, it is possible to obtain the necessary torque to start slipping on each of the contact portions when the rack shaft moves for turning. The force can be reduced compared to when each abutment begins to slide at the same time. Therefore, the steerability of the steering device can be improved. Further, even if the timing at which the first contact portion and the second contact portion start to slide on the rack shaft is changed, the biasing force with which the first biasing mechanism and the second biasing mechanism bias the rack shaft does not change. Therefore, it is possible to improve the steerability of the steering device while preventing backlash and abnormal noise due to reverse input from the wheels.

The present invention is characterized in that gaps of different sizes are formed between the first accommodating portion and the first contact portion and between the second accommodating portion and the second contact portion.

In these inventions, the size of the gap between the first accommodation portion and the first contact portion and the size of the gap between the second accommodation portion and the second contact portion are individually set, whereby the rack You can adjust the ease of movement of the shaft.

In the present invention, the first urging mechanism further includes an annular first elastic portion that is compressed between the first contact portion and the first accommodating portion, and the second urging mechanism includes: It further has an annular second elastic part that is compressed and provided between the second contact part and the second housing part, and the stress acting on the first contact part from the first elastic part and the second The stress acting on the second contact portion from the elastic portion is different.

In this invention, by making the first elastic portion and the second elastic portion different, it is possible to adjust the easiness of movement of the rack shaft.

According to the present invention, one of the first elastic portion and the second elastic portion, which exerts a large stress on the corresponding first contact portion and second contact portion, is formed by two annular elastic portions provided apart in the axial direction. Of the two elastic members, one elastic member provided away from the rack shaft has a larger wire diameter than the other elastic member provided near the rack shaft.

In the present invention, by changing the wire diameters of the two elastic members, it is possible to make the rack shaft difficult to move.

The present invention is characterized in that the first contact portion is formed so as to start sliding on the rack shaft before the second contact portion.

In the present invention, immediately after the first contact portion starts to slide on the rack shaft at the beginning of the stroke of the steering device, the second contact portion can follow the rack shaft. The shaft can travel a great deal without being hindered. As a result, it is possible to improve the initial responsiveness of the stroke of the steering device.

According to the present invention, it is possible to improve steering performance while preventing the generation of abnormal noise in a dual-pinion steering device.

1 is a configuration diagram of an electric power steering device according to an embodiment; FIG. It is a partial sectional view of a rack shaft. It is a partial cross-sectional view of the vicinity of the first biasing mechanism. It is a partial cross-sectional view of the vicinity of the second biasing mechanism.

An electric power steering device 100 as a steering device according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an electric power steering device 100 includes a steering shaft 11 as a first shaft member that rotates in accordance with steering of a steering wheel 1 as a steering member by a driver, and a steering shaft 11 that is provided on the steering shaft 11. 11, and a rack shaft 12 having a rack gear 12a meshing with the first pinion gear 16 and steering the wheel 2.

The steering shaft 11 includes an input shaft 13 that rotates as the driver operates the steering wheel 1, an output shaft 15 that displaces the rack shaft 12, and a torsion bar that connects the input shaft 13 and the output shaft 15. 14 and .

The rack shaft 12 is a shaft-shaped member that extends in the left-right direction of the vehicle and is connected to the wheels 2 via tie rods 5 and knuckle arms 4 .

The output shaft 15 and the rack shaft 12 are connected to each other via a rack and pinion mechanism including a first pinion gear 16 provided at the end of the output shaft 15 and a rack gear 12 a provided on the rack shaft 12 . The torque of the output shaft 15 is converted into a load in the axial direction of the rack shaft 12 and transmitted to the rack shaft 12 via the first pinion gear 16 and the rack gear 12a that mesh with each other. As a result, the rack shaft 12 is displaced in the axial direction by the transmitted torque, and the wheels 2 are steered via the tie rods 5 .

Further, the electric power steering apparatus 100 includes an electric motor 21 as a motor that is a power source for steering assist torque, a drive shaft 22 that is rotationally driven by the electric motor 21, and is provided on the drive shaft 22. A second pinion gear 23 that rotates together with the drive shaft 22 , and a reduction section 50 that reduces the speed of rotation of the electric motor 21 and transmits it to the drive shaft 22 .

The reduction unit 50 is a worm gear mechanism including a worm shaft 51 driven by the electric motor 21 and a worm wheel 52 provided on the drive shaft 22 . The worm shaft 51 and the worm wheel 52 mesh with each other, and the torque of the electric motor 21 is transmitted to the drive shaft 22 via the worm shaft 51 and the worm wheel 52 . The second pinion gear 23 and the rack gear 12a mesh with each other, and the torque transmitted from the electric motor 21 to the drive shaft 22 is further transmitted to the rack shaft 12 via the second pinion gear 23 and the rack gear 12a.

The electric power steering device 100 further includes a torque sensor 40 that detects torque acting on the torsion bar 14 and a controller 30 that controls driving of the electric motor 21 according to the detected value of the torque sensor 40 .

The controller 30 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read-Only Memory) that stores control programs and the like executed by the CPU, and a RAM (random access memory) that stores the calculation results of the CPU and the like. and a microcomputer including The controller 30 may be composed of a single microcomputer, or may be composed of a plurality of microcomputers.

The torque sensor 40 detects the steering torque applied to the input shaft 13 in accordance with the driver's steering operation, and outputs a voltage signal corresponding to the detected steering torque to the controller 30 . The controller 30 calculates the torque output by the electric motor 21 based on the voltage signal from the torque sensor 40, and controls driving of the electric motor 21 so that the torque is generated.

Thus, in the electric power steering apparatus 100 having the above configuration, the steering torque applied to the input shaft 13 is detected by the torque sensor 40, and the drive of the electric motor 21 is controlled by the controller 30 based on the detection result. It is possible to assist the driver's steering operation. As described above, the electric power steering device 100 is a dual-pinion steering device in which the steering torque by the driver and the steering assist torque by the electric motor 21 are independently input to the rack shaft 12 .

As shown in FIG. 2 , the electric power steering device 100 houses a rack housing 17 as a case member that houses the rack shaft 12 , a shaft housing 18 that houses the steering shaft 11 , a reduction section 50 and a drive shaft 22 . a worm housing 53;

The rack housing 17 includes an accommodation hole 17a formed through the axial direction to accommodate the rack shaft 12, and a first insertion hole 17b and a second insertion hole 17b which are open at one end on the outer peripheral surface and are formed so as to intersect the accommodation hole 17a. and two insertion holes 17c. The shaft housing 18 is connected to the rack housing 17 via bolts (not shown) such that the output shaft 15 is inserted through the first insertion hole 17b. The worm housing 53 is connected to the rack housing 17 via bolts (not shown) such that the drive shaft 22 is inserted through the second insertion hole 17c.

As shown in FIG. 3 , the electric power steering device 100 includes a first biasing mechanism 60 that biases the rack shaft 12 toward the first pinion gear 16 . The first biasing mechanism 60 is housed in a first housing portion 17 d provided in the rack housing 17 . In other words, the rack housing 17 has a first accommodating portion 17d that accommodates the first biasing mechanism 60. As shown in FIG. The first accommodating portion 17 d is a through hole extending perpendicularly to the rack shaft 12 and the output shaft 15 and opening to the inner peripheral surface of the accommodating hole 17 a and the outer peripheral surface of the rack housing 17 .

The first biasing mechanism 60 includes a first yoke 61 as a first contact portion that contacts the rack shaft 12 and a first biasing member that biases the first yoke 61 toward the rack shaft 12 . It has a spring 62 , a first cover 63 that closes the opening of the first accommodating portion 17 d of the rack housing 17 , and two O-rings 64 a and 64 b as elastic members provided on the outer peripheral surface of the first yoke 61 . A first elastic portion 64 is formed by the O-rings 64a and 64b.

The first yoke 61 is slidably accommodated in the first accommodation portion 17d. The first yoke 61 is provided with a contact surface 61a along the outer peripheral surface of the rack shaft 12, and the rack shaft 12 contacts the contact surface 61a and is accommodated in the first accommodation portion 17d. As a result, a static frictional force acts between the contact surface 61 a of the first yoke 61 and the rack shaft 12 . Also, the outer diameter of the first yoke 61 is formed smaller than the inner diameter of the first accommodating portion 17d. Therefore, a gap 65 is formed between the outer peripheral surface of the first yoke 61 and the inner peripheral surface of the first accommodating portion 17d. In addition, in FIG. 3, the size of the gap 65 is exaggerated. Annular grooves 61b and 61c are formed on the outer peripheral surface of the first yoke 61 so as to be separated from each other in the axial direction of the first accommodating portion 17d. The groove 61b is provided farther from the rack shaft 12 than the groove 61c.

The O-rings 64a, 64b of the first elastic portion 64 are partially accommodated in the grooves 61b, 61c, respectively, and are provided under compression between the first yoke 61 and the first accommodation portion 17d. Thus, the O-rings 64a and 64b are axially spaced apart, with the O-ring 64a being further away from the rack shaft 12 than the O-ring 64b. As a result, the first yoke 61 is elastically supported by the first elastic portion 64 with respect to the first housing portion 17d in a state in which a gap 65 is provided between the first housing portion 17d and the inner peripheral surface of the first housing portion 17d. be done. In other words, stress for supporting the first yoke 61 acts on the first yoke 61 from the first elastic portion 64 . Therefore, the first yoke 61 is radially movable within the first accommodating portion 17 d and can follow the movement of the rack shaft 12 in contact therewith by the size of the gap 65 . The operation of the first yoke 61 following the rack shaft 12 will be described later.

The first spring 62 is arranged such that its central axis is orthogonal to the central axis of the rack shaft 12 . Also, the first cover 63 is attached to the rack housing 17 by being screwed onto a female screw (not shown) provided in the first accommodating portion 17d. A first spring 62 is provided in a compressed state between the first yoke 61 and the first cover 63 . Thereby, the first spring 62 biases the rack shaft 12 toward the first pinion gear 16 via the first yoke 61 .

As shown in FIG. 4 , the electric power steering device 100 includes a second biasing mechanism 70 that biases the rack shaft 12 toward the second pinion gear 23 . The second biasing mechanism 70 is housed in a second housing portion 17e provided in the rack housing 17. As shown in FIG. In other words, the rack housing 17 has a second accommodation portion 17e that accommodates the second biasing mechanism 70 . The second accommodation portion 17 e is a through hole extending perpendicularly to the rack shaft 12 and the drive shaft 22 and opening to the inner peripheral surface of the accommodation hole 17 a and the outer peripheral surface of the rack housing 17 .

The second biasing mechanism 70 includes a second yoke 71 as a second contact portion that contacts the rack shaft 12 and a second biasing member that biases the second yoke 71 toward the rack shaft 12 . It has a spring 72 , a second cover 73 that closes the opening of the second accommodating portion 17 e of the rack housing 17 , and O-rings 74 a and 74 b as elastic members provided on the outer peripheral surface of the second yoke 71 . The O-rings 74a and 74b form a second elastic portion 74 that is compressed between the second yoke 71 and the second housing portion 17e. Annular grooves 71b and 71c are formed on the outer peripheral surface of the second yoke 71 so as to be separated from each other in the axial direction of the second accommodating portion 17e. The O-rings 74a and 74b are partially accommodated in the grooves 71b and 71c, respectively, and are secondly accommodated by the second elastic portion 74 with a gap 75 provided between them and the inner peripheral surface of the second accommodation portion 17e. It is elastically supported with respect to the portion 17e. Since the second biasing mechanism 70 has the same basic configuration as the first biasing mechanism 60, detailed description thereof is omitted. Differences between the first biasing mechanism 60 and the second biasing mechanism 70 will be described later.

Next, the operation of the first yoke 61 and the second yoke 71 following the rack shaft 12 will be described. Since this operation is the same for the first yoke 61 and the second yoke 71, the operation for the first yoke 61 to follow the rack shaft 12 will be described as an example.

The rack shaft 12 moves in its own axial direction due to input from the first pinion gear 16 or the like to steer the wheels 2, or moves in its own axial direction due to input from the first pinion gear 16, vibration, or the like. May move vertically. Since the first pinion gear 16 and the rack shaft 12 mesh obliquely, the input from the first pinion gear 16 causes the rack shaft 12 to move in its own axial direction and radial direction.

When the rack shaft 12 moves in its own axial direction, a frictional force acts between the contact surface 61 a of the first yoke 61 and the rack shaft 12 . Thereby, the first yoke 61 follows the movement of the rack shaft 12 . Further, the supporting force of the first elastic portion 64 acts on the first yoke 61 . As the first yoke 61 moves together with the rack shaft 12, the front side of the first elastic portion 64 in the moving direction is compressed, and the first elastic portion 64 acts on the first yoke 61 in the direction opposite to the moving direction. Increases bearing capacity. The first yoke 61 starts to slide on the rack shaft 12 when the force acting in the opposite direction to the moving direction of the rack shaft 12 becomes greater than the frictional force acting between the contact surface 61a and the rack shaft 12. .

More specifically, when the rack shaft 12 moves in its own axial direction, the first yoke 61 moves against the supporting force of the first elastic portion 64 so as to fill the gap 65 toward the front of the rack shaft 12 in the moving direction. It translates in the direction of movement of shaft 12 . As the amount of movement of the rack shaft 12 increases, the first elastic portion 64 is compressed, so the supporting force that the first yoke 61 receives from the first elastic portion 64 increases. When the supporting force of the first elastic portion 64 is set relatively large, if the supporting force of the first elastic portion 64 becomes larger than the frictional force acting between the contact surface 61a and the rack shaft 12, the rack shaft 12 The first yoke 61 starts to slide on the rack shaft 12 before the contact with the inner peripheral surface of the first accommodation portion 17d.

When the supporting force of the first elastic portion 64 is set to be relatively small, the supporting force of the first elastic portion 64 remains at the contact surface 61a until the rack shaft 12 contacts the inner peripheral surface of the first accommodating portion 17d. and the rack shaft 12.

When the first yoke 61 comes into contact with the inner peripheral surface of the first housing portion 17d, the first yoke 61, in addition to the supporting force of the first elastic portion 64, moves from the inner peripheral surface of the first housing portion 17d to the rack shaft 12. receives a reaction force in the opposite direction to the movement direction of When the rack shaft 12 further moves from the state in which the first yoke 61 contacts the first accommodation portion 17d, the reaction force that the first yoke 61 receives from the inner peripheral surface of the first accommodation portion 17d increases. Then, the force acting on the first yoke 61 in the direction opposite to the moving direction of the rack shaft 12 becomes greater than the frictional force acting between the contact surface 61a and the rack shaft 12, and the first yoke 61 begins to slide against the rack shaft 12 . Therefore, the first yoke 61 comes into contact with the inner peripheral surface of the first accommodating portion 17 d and is restricted from moving, so that it cannot follow the rack shaft 12 .

When the first yoke 61 follows the movement of the rack shaft 12 , static frictional force acts between the contact surface 61 a and the rack shaft 12 . Also, when the first yoke 61 slides on the rack shaft 12 , a dynamic frictional force acts between the contact surface 61 a and the rack shaft 12 .

By making the gap 65 small, the first yoke 61 quickly contacts the inner peripheral surface of the first accommodating portion 17d and receives the reaction force from the inner peripheral surface of the first accommodating portion 17d. It can be configured to start sliding on the rack shaft 12 early even if the supporting force is small. Further, by increasing the supporting force of the first elastic portion 64, a force acting in the opposite direction to the moving direction of the rack shaft 12 acts between the contact surface 61a and the rack shaft 12, and the rack shaft 12 moves in the moving direction. Since the frictional force increases more quickly than the frictional force directed toward the first receiving portion 17d, it can be configured to start sliding on the rack shaft 12 earlier before contacting the inner peripheral surface of the first accommodating portion 17d. By changing the size of the gap 65 and the supporting force of the first elastic portion 64 in this manner, the timing at which the first yoke 61 starts to slide on the rack shaft 12 can be changed. In addition, if the first yoke 61 starts to slide on the rack shaft 12 earlier, the rack shaft 12 becomes more difficult to move from a state where the rack shaft 12 is stationary to when it starts to slide on the first yoke 61. Become.

Also, when the rack shaft 12 moves in a direction perpendicular to its own axial direction, the first yoke 61 inclines toward the moving direction of the rack shaft 12 so as to fill the gap 65 and follows the rack shaft 12 . Thereby, the first yoke 61 can follow the rack shaft 12 even when the rack shaft 12 moves in a direction perpendicular to the axial direction.

In general, the biasing mechanism that biases the rack shaft toward the pinion gear is designed, for example, to increase the biasing force of the biasing member to strongly press the rack toward the pinion, in order to prevent noise due to backlash. configured to In this configuration, since the rack is strongly pressed against the pinion and is difficult to move, the load from the wheel is reversely input to the rack, which prevents the rack from contacting the pinion and the like, thereby preventing noise from being generated. It may get worse. Also, if such an urging mechanism is applied to each of the two pinions of a dual-pinion steering device, the rack will be strongly pressed against each pinion, making it more difficult to move. Therefore, there is a possibility that the steering performance of the dual-pinion steering device may deteriorate.

On the other hand, in the electric power steering device 100 according to the present embodiment, the contact surface 61 a of the first yoke 61 and the contact surface 71 a of the second yoke 71 cannot follow the rack shaft 12 . The timing to start slipping is formed differently.

In order to differentiate the timings at which the first yoke 61 and the second yoke 71 start to slide on the rack shaft 12, the sizes of the gaps 65 and 75 and the supporting forces of the elastic portions 64 and 74 are adjusted as described above. Make each size different. The magnitude of the supporting force of each elastic portion 64, 74 can be adjusted, for example, by changing the number, material, and shape of the O-rings forming each elastic portion 64, 74. FIG. In this embodiment, the first yoke 61 is formed to start sliding on the rack shaft 12 before the second yoke 71 does. Specifically, the gap 65 formed around the first yoke 61 is formed smaller than the gap 75 formed around the second yoke 71 . Further, the supporting force of the first elastic portion 64 provided around the first yoke 61 (in other words, the stress acting on the first yoke 61 from the first elastic portion 64) It is formed larger than the supporting force of the second elastic portion 74 (in other words, the stress acting on the second yoke 71 from the second elastic portion 74). More specifically, of the O-rings 64a and 64b of the first elastic portion 64, the O-ring 64a provided away from the rack shaft 12 has a wire diameter larger than that of the O-ring 64b. 74a and 74b are formed to have the same wire diameter.

Here, the rack shaft 12 steers the wheels 2 by sliding relative to the first yoke 61 and the second yoke 71 . Therefore, if the frictional force between the contact surfaces 61a, 71a of the yokes 61, 71 and the rack shaft 12 is large, the steerability of the electric power steering apparatus 100 is deteriorated. The frictional force becomes static frictional force when the yokes 61 and 71 are stationary with respect to the rack shaft 12 , and thus is larger than when the yokes 61 and 71 are sliding with respect to the rack shaft 12 . Become. That is, the total amount of frictional force between the contact surfaces 61a, 71a of the yokes 61, 71 and the rack shaft 12 when both the yokes 61, 71 are stationary with respect to the rack shaft 12 is becomes larger than the state where is slipped on the rack shaft 12 . Therefore, in a configuration in which the yokes 61 and 71 start to slide at the same time, a force twice the maximum static friction force is required when moving the rack shaft 12 .

In the electric power steering device 100, the first yoke 61 starts to slide on the rack shaft 12 before the second yoke 71, as described above. Therefore, when the second yoke 71 starts to slide, dynamic frictional force acts on the first yoke 61, so the force for moving the rack shaft 12 may be less than twice the maximum static frictional force. . Therefore, when the rack shaft 12 moves for steering, the maximum force required to start slipping on each of the yokes 61 and 71 is compared with the case where each of the yokes 61 and 71 starts to slip simultaneously. can be made smaller. Therefore, the steerability of the electric power steering device 100 can be improved.

In addition, since the biasing force with which the first biasing mechanism 60 and the second biasing mechanism 70 bias the rack shaft 12 does not change, backlash and abnormal noise due to reverse input from the wheels 2 are prevented. The steerability of the electric power steering device 100 can be improved.

Further, in the present embodiment, as described above, the first yoke 61 is formed to start sliding on the rack shaft 12 before the second yoke 71 does. At the beginning of the stroke of the electric power steering device 100, when the first yoke 61 starts to slide relative to the rack shaft 12, the second yoke 71 is not in contact with the inner peripheral surface of the second accommodating portion 17e. That is, a gap 75 is formed between the second yoke 71 and the inner peripheral surface of the second housing portion 17e with respect to the moving direction of the rack shaft 12 . Therefore, immediately after the first yoke 61 starts to slide on the rack shaft 12 , the second yoke 71 can follow the rack shaft 12 , so that the second yoke 71 and the rack shaft 12 do not move by the gap 75 . The movement of the rack shaft 12 becomes large without being hindered. As a result, the initial responsiveness of the stroke of the electric power steering apparatus 100 can be improved.

The electric power steering device 100 may be formed so that the second yoke 71 starts to slide on the rack shaft 12 before the first yoke 61 does. In this configuration, the rack shaft 12 becomes more difficult to move from a stationary state to a time when the rack shaft 12 starts to slide with respect to the second yoke 71 . That is, since the rack shaft 12 is more difficult to move than in the above configuration, it is possible to prevent abnormal noise caused by reverse input to the rack shaft 12 .

Further, the elastic portions 64 and 74 may not be provided in the biasing mechanisms 60 and 70, respectively. In this case, the timing at which the yokes 61 and 71 start to slide on the rack shaft 12 can be made different by making the gaps 65 and 75 different. Further, the timing at which the yokes 61 and 71 start to slide on the rack shaft 12 may be varied by changing the axial length of the yokes 61 and 71 and the positions at which the elastic portions 64 and 74 are provided. . Specifically, if the yokes 61 and 71 are shortened in the axial direction or the positions where the elastic portions 64 and 74 are provided are made closer to the rack shaft 12 , the fulcrum of movement of the yokes 61 and 71 will be closer to the rack shaft 12 . This facilitates movement of the yokes 61 and 71 following the rack shaft 12 with the elastic portions 64 and 74 as fulcrums. As a result, the timing at which the yokes 61 and 71 start to slide on the rack shaft 12 is advanced.

According to the present embodiment described above, the following effects can be obtained.

The electric power steering device 100 differs in the timing at which the yokes 61 and 71 start to slide on the rack shaft 12, so that when the rack shaft 12 moves, it is necessary for the yokes 61 and 71 to start to slide. force can be reduced compared to the case where each yoke 61, 71 starts to slide at the same time. Therefore, the steerability of the electric power steering device 100 can be improved. In addition, since the biasing force with which the first biasing mechanism 60 and the second biasing mechanism 70 bias the rack shaft 12 does not change, backlash and abnormal noise due to reverse input from the wheels 2 are prevented. The steerability of the electric power steering device 100 can be improved.

Further, the electric power steering device 100 is formed such that the contact surface 61a starts to slide on the rack shaft 12 before the contact surface 71a, so that the first yoke 61 slides on the rack shaft 12. Immediately after starting, the second yoke 71 and the rack shaft 12 can move largely without their movements being hindered. As a result, the initial responsiveness of the stroke of the electric power steering apparatus 100 can be improved.

Next, a modified example of this embodiment will be described.

<Modification>
In the electric power steering apparatus 100 of the above embodiment, the first pinion gear 16 and the second pinion gear 23 are held on the rack shaft 12 by urging the rack shaft 12 by the first urging mechanism 60 and the second urging mechanism 70. a holding force is generated. Specifically, the holding force in this embodiment indicates the force acting on the first pinion gear 16 and the second pinion gear 23 through the rack shaft 12 . A force acts on the first pinion gear 16 and the second pinion gear 23 through the rack shaft 12 from the first biasing mechanism 60 and the second biasing mechanism 70 . Furthermore, force acts on the first pinion gear 16 and the second pinion gear 23 from the rack shaft 12 as a reaction force to the force input to the rack shaft 12 from itself. The holding force is the sum of the above two forces.

The electric power steering device 100 has a first holding force by which the first pinion gear 16 is held on the rack shaft 12 by urging the rack shaft 12 by the first urging mechanism 60 and a second urging mechanism 70 to hold the first pinion gear 16 on the rack shaft 12 . The second holding force with which the second pinion gear 23 is held by the rack shaft 12 by being biased may be configured to be different. The first holding force can be adjusted by changing the set load of the first spring 62, for example. This is because the force acting on the first pinion gear 16 through the rack shaft 12 changes as the biasing force of the first spring 62 changes. When the set load of the first spring 62 is increased, the biasing force of the first spring 62 is increased, and the force acting on the first pinion gear 16 through the rack shaft 12 is increased. Therefore, the first holding force increases. Conversely, when the set load of the first spring 62 is reduced, the biasing force of the first spring 62 is reduced, and the force acting on the first pinion gear 16 through the rack shaft 12 is reduced. Therefore, the first holding force is reduced. Similarly, the second holding force can also be adjusted by changing the set load of the second spring 72 . In this manner, the electric power steering device 100 can individually set the first holding force and the second holding force by the members forming the first biasing mechanism 60 and the second biasing mechanism 70 .

Further, in the electric power steering device 100, the set load of the first spring 62 is smaller than the set load of the second spring 72, in other words, the first holding force is smaller than the second holding force. The reaction force that the second pinion gear 23 receives from the rack shaft 12 is smaller than the reaction force that the second pinion gear 23 receives from the rack shaft 12 . Therefore, the rack shaft 12 is more likely to move with the input from the steering shaft 11 than with the input from the drive shaft 22 . As a result, the steerability of the electric power steering device 100 can be improved. Moreover, since the second holding force is higher than the first holding force, backlash that occurs between the rack shaft 12 and the second pinion gear 23 can be prevented. In this manner, the electric power steering apparatus 100 can achieve both prevention of abnormal noise and improvement of steering performance.

Alternatively, the first holding force may be smaller than the second holding force. For example, by forming the first yoke 61 and the second yoke 71 from different materials, or by coating the contact surface 61a and the contact surface 71a with different materials, the first yoke relative to the rack shaft 12 can be adjusted. 61 may be configured to have a smaller friction coefficient than the second yoke 71 . When the coefficient of friction of the first yoke 61 is small, the frictional force generated between the contact surface 61a of the first yoke 61 and the rack shaft 12 is small. As a result, the reaction force that the first pinion gear 16 receives from the rack shaft 12 is smaller than the reaction force that the second pinion gear 23 receives from the rack shaft 12 . Therefore, the first holding force becomes smaller than the second holding force, and the same effect as that of the above embodiment is exhibited.

The configuration, action, and effect of the embodiment of the present invention configured as described above will be collectively described.

An electric power steering device 100 as a steering device includes: a steering shaft 11 as a first shaft member that rotates according to steering of a steering wheel 1 as a steering member by a driver; a first pinion gear 16, a drive shaft 22 as a second shaft member that is rotationally driven by an electric motor 21 as a motor, a second pinion gear 23 that is provided on the drive shaft 22 and rotates together with the drive shaft 22, and a first pinion gear 16 and a rack gear 12a that meshes with the second pinion gear 23 and steers the wheel 2; a rack housing 17 as a case member that accommodates the rack shaft 12; A first biasing mechanism 60 for biasing and a second biasing mechanism 70 for biasing the rack shaft 12 toward the second pinion gear 23 are provided, and the rack housing 17 accommodates the first biasing mechanism 60. It has a first accommodating portion 17d and a second accommodating portion 17e that accommodates a second biasing mechanism 70. The first biasing mechanism 60 contacts the rack shaft 12 and follows the movement of the rack shaft 12. A first yoke 61 as a first contact portion movable within the first housing portion 17d and a first spring 62 as a first biasing member that biases the first yoke 61 toward the rack shaft 12 are provided. The second biasing mechanism 70 includes a second yoke 71 as a second contact portion that contacts the rack shaft 12 and follows the movement of the rack shaft 12 and is movable within the second housing portion 17e; and a second spring 72 as a second biasing member that biases the yoke 71 toward the rack shaft 12 . As the amount of movement increases, the movement is restricted by the rack housing 17 and becomes unable to follow the rack shaft 12 , and the first yoke 61 and the second yoke 71 become unable to follow the rack shaft 12 and start to slide relative to the rack shaft 12 . different timings.

In this configuration, the first yoke 61 of the first urging mechanism 60 and the second yoke 71 of the second urging mechanism 70 cannot follow the movement of the rack shaft 12 and start to slide relative to the rack shaft 12. different. The rack shaft 12 slides on the yokes 61 and 71 to steer the wheels 2 . Therefore, if the frictional force between the yokes 61 and 71 and the rack shaft 12 is large, the steerability of the electric power steering apparatus 100 is deteriorated. The frictional force is greater when the yokes 61 and 71 are stationary with respect to the rack shaft 12 than when the yokes 61 and 71 are sliding with respect to the rack shaft 12 . That is, when both yokes 61 and 71 are stationary with respect to rack shaft 12, the total amount of frictional force between each yoke 61 and 71 and rack shaft 12 is It becomes larger than the state where it is slipping. Therefore, by making one of the yokes 61 and 71 start to slide on the rack shaft 12 first, when the rack shaft 12 moves for steering, it starts to slide on the yokes 61 and 71 respectively. The force required for this can be reduced compared to when the yokes 61 and 71 start to slide simultaneously. Therefore, the steerability of the electric power steering device 100 can be improved. Further, since the urging force with which the first urging mechanism 60 and the second urging mechanism 70 urge the rack shaft 12 does not change, backlash and abnormal noise due to reverse input from the wheels can be prevented. The steerability of the power steering device 100 can be improved.

Further, in the electric power steering apparatus 100, gaps 65, 75 of different sizes are formed between the first accommodation portion 17d and the first yoke 61 and between the second accommodation portion 17e and the second yoke 71. be.

In this configuration, the size of the gap 65 between the first accommodation portion 17d and the first yoke 61 and the size of the gap 75 between the second accommodation portion 17e and the second yoke 71 are individually set, so that the rack The ease of movement of shaft 12 can be adjusted.

In addition, in the electric power steering device 100, the first biasing mechanism 60 further has an annular first elastic portion 64 that is compressed between the first yoke 61 and the first housing portion 17d, The second urging mechanism 70 further has an annular second elastic portion 74 that is compressed between the second yoke 71 and the second housing portion 17e. The stress acting on the second elastic portion 74 and the stress acting on the second yoke 71 are different.

In this configuration, the easiness of movement of the rack shaft 12 can be adjusted by making the first elastic portion 64 and the second elastic portion 74 different.

Further, in the electric power steering apparatus 100, one of the first elastic portion 64 and the second elastic portion 74 that exerts a greater stress on the corresponding first yoke 61 and second yoke 71 is provided apart in the axial direction. It has two O-rings 64a, 64b (74a, 74b) as two annular elastic members, and one O-ring 64a ( 74 a ) is formed to have a wire diameter larger than that of the other O-ring 64 b ( 74 b ) provided near the rack shaft 12 .

In this configuration, by changing the wire diameters of the two O-rings 64a, 64b (74a, 74b), it is possible to make the rack shaft 12 difficult to move.

Further, the electric power steering device 100 is formed so that the first yoke 61 starts to slide on the rack shaft 12 before the second yoke 71 does.

With this configuration, the second yoke 71 can follow the rack shaft 12 immediately after the first yoke 61 starts to slide on the rack shaft 12 at the beginning of the stroke of the electric power steering device 100 . And the rack shaft 12 can move a lot without being hindered. As a result, the initial responsiveness of the stroke of the electric power steering apparatus 100 can be improved.

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above embodiments. do not have.

The steering device may be of a so-called two-assist type having a mechanism for assisting the steering operation on the steering shaft side as well.

Reference Signs List 1 Steering wheel (steering member) 2 Wheel 11 Steering shaft (first shaft member) 12 Rack shaft 12a Rack gear 16 First pinion gear , 17... rack housing (case member), 17d... first accommodation portion, 17e... second accommodation portion, 21... motor (electric motor), 22... drive shaft (second shaft member), 23... second pinion gear, 60... first biasing mechanism, 61... first contact portion, 62... first spring (first biasing member), 64... First elastic portion 64a, 64b O-ring (elastic member) 70 Second biasing mechanism 71 Second contact portion 72 Second spring (second biasing mechanism) member), 74... second elastic portion, 74a, 74b... O-ring (elastic member), 100... electric power steering device (steering device)

Claims (5)

a first shaft member that rotates in response to steering of the steering member by the driver;
a first pinion gear provided on the first shaft member and rotating together with the first shaft member;
a second shaft member rotationally driven by a motor;
a second pinion gear provided on the second shaft member and rotating together with the second shaft member;
a rack shaft having a rack gear meshing with the first pinion gear and the second pinion gear and steering a wheel;
a case member that accommodates the rack shaft;
a first biasing mechanism that biases the rack shaft toward the first pinion gear;
a second biasing mechanism that biases the rack shaft toward the second pinion gear,
The case member has a first accommodation portion that accommodates the first biasing mechanism and a second accommodation portion that houses the second biasing mechanism,
The first urging mechanism includes a first contact portion that contacts the rack shaft and is movable within the first accommodating portion following the movement of the rack shaft, and the first contact portion is directed toward the rack shaft. a first biasing member that biases the
The second biasing mechanism includes a second contact portion that contacts the rack shaft and is movable within the second accommodating portion following the movement of the rack shaft, and the second contact portion is directed toward the rack shaft. a second biasing member that biases the
The first contact portion and the second contact portion move within the corresponding first housing portion and second housing portion by means of the case member as the amount of movement of the rack shaft that steers the wheel increases. The movement is restricted and it becomes impossible to follow the rack shaft,
The steering device, wherein the first contact portion and the second contact portion become unable to follow the rack shaft and start to slide relative to the rack shaft at different timings. The steering device according to claim 1,
A steering device, wherein gaps of different sizes are formed between the first accommodating portion and the first contact portion and between the second accommodating portion and the second contact portion. . The steering device according to claim 1 or 2,
The first urging mechanism further includes an annular first elastic portion that is compressed between the first contact portion and the first accommodating portion, and
The second urging mechanism further includes an annular second elastic portion that is compressed between the second contact portion and the second accommodation portion, and
A steering device, wherein a stress acting from the first elastic portion to the first contact portion is different from a stress acting from the second elastic portion to the second contact portion. The steering device according to claim 3,
Of the first elastic portion and the second elastic portion, the one having the larger stress acting on the corresponding first contact portion and the second contact portion is formed by two annular elastic portions spaced apart in the axial direction. having a member;
A steering device, wherein one of the two elastic members provided away from the rack shaft has a larger wire diameter than the other elastic member provided near the rack shaft. The steering device according to any one of claims 1 to 4,
The steering device, wherein the first contact portion is formed to start sliding on the rack shaft before the second contact portion.

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