JPH1016799A - Power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering system that is able to convert the rotation of a steering auxiliary motor into a slide motion in the axial direction of a steering shaft surely, dispensing with any machining of this steering shaft, and to simplify adjusting operations attendant upon assemblage, besides satisfiable to the cut request of a setup space of the steering auxiliary motor inclusive of a transmission system. SOLUTION: A rotary cylinder 6 rotating around a shaft by power transmission of a steering auxiliary motor 5 is set up in a housing 2 of a steering shaft 1, and three feed rollers 7, 7 and 7 are attached to one end face of this rotary cylinder 6 free of rotation around respective pivots tilted as far as each equiangle to the shaft center in the same sense in the circumferential direction, and these feed rollers 7, 7 and 7 are so constituted to have them rollably contacted with a peripheral surface of the steering shaft 1. In addition, a guide groove engaging with these feed rollers 7, 7 and 7 may be installed in a circumferential surface of this steering shaft 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus using an electric motor as a source of a steering assist force.

[0002]

2. Description of the Related Art A power steering device (power steering device) is a steering wheel (steering wheel) for steering.
It is equipped on many automobiles to reduce the labor required for operation of the vehicle and to obtain a comfortable steering feeling. In recent years, an electric power steering device using an electric motor driven in accordance with a steering operation has been put into practical use as an actuator for assisting steering, instead of a hydraulic actuator widely used conventionally. I have.

[0003] Such an electric power steering apparatus can flexibly cope with a change in the assisting force characteristic according to the driving state, such as a vehicle speed, a steering angle, etc., by controlling the driving of a steering assisting motor. It has been desired to expand its application range because of the advantage of obtaining a power steering device.However, a transmission system that transmits the rotation of a steering assist motor to a steering mechanism is indispensable in realizing an electric power steering device. In addition, there is a problem that it is difficult to obtain a small motor capable of obtaining a sufficient steering assist force.

[0004] A steering assist motor is connected to the steering wheel.
A steering shaft that is connected at both ends to a steering column that rotates in accordance with the operation of the steering wheel, or to a steering wheel (generally, left and right front wheels) and slides in an axial direction to perform steering. (Eg, a rack shaft in a rack and pinion steering mechanism). The former may transmit the rotation of the steering assist motor to the steering column, which is a rotating member, and has the advantage that the transmission system can be simply configured by a general gear reducer or the like, but the periphery of the steering column has It is difficult to secure the arrangement position of the motor including the transmission system, and there is a disadvantage that the applicable range is limited.

On the other hand, in the latter, the structure of the transmission system for converting the rotation of the steering assist motor into sliding of the steering shaft is complicated, but the structure of the transmission system in the vicinity of the steering shaft mounted on the front of the vehicle is complicated. There is an advantage that it is relatively easy to secure the arrangement position of the motor, and it can be used in a wide range of vehicle types. However, even in this configuration, it is important to reduce the space for disposing the motor including the transmission system to the steering shaft.
As disclosed in Japanese Patent Application Laid-Open No. 61-191468, there has been proposed a power steering device which uses a ball screw mechanism for the transmission system to reduce the installation space.

In this power steering device, a part of a steering shaft is
A male screw part having a ball screw rail formed on its outer periphery is formed. A nut member screwed through a number of balls to the outside of the male screw part is restrained in the axial direction within a housing supporting the steering shaft. The nut member is rotated by transmitting the torque of a steering assist motor to the nut member, and the steering shaft is slid in the axial direction by utilizing the screwing of a ball screw accompanying this rotation. In addition, the transmission mechanism capable of obtaining a large reduction ratio inside the housing can be configured compactly, and the miniaturized motor is mounted close to the housing of the steering shaft to meet the above-described demand for reducing the installation space. There is to gain.

[0007]

However, in the above-mentioned conventional construction, high precision is required for forming the ball screw rail on the outer periphery of the steering shaft and the inner periphery of the nut member, and a large number of processing steps are required. However, there is a problem that it takes a lot of time and effort to adjust a threaded state between a steering shaft on which the ball screw rail is formed and a nut member via a large number of balls, resulting in an increase in the number of assembly steps. .

Further, in order to compensate for a decrease in bending strength in the portion where the ball screw rail is formed, it is necessary to increase the diameter of the steering shaft and a part or all of the housing of the steering shaft. There was a problem that can not respond to.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and uses a transmission system having a simple configuration instead of a ball screw mechanism to ensure that the rotation of a steering assist motor is prevented from sliding in the axial direction of a steering shaft. A power steering device that can eliminate the need for machining a steering shaft, simplifies the adjustment work involved in assembly, and can meet the demand for reducing the space for disposing the steering assist motor including the transmission system. The purpose is to provide.

[0010]

A power steering apparatus according to the present invention transmits a torque of a motor driven in accordance with a steering operation to a steering shaft supported in a cylindrical housing. An electric power steering device configured to assist in steering by sliding in the axial direction, wherein the steering in the axial direction is restrained and supported inside the housing, and the steering is transmitted by the motor. A rotating cylinder that rotates coaxially with the axis, and a part of the rotating cylinder, which is rotatably supported around each other axis inclined at the same angle in the same circumferential direction with respect to the axis of the rotating cylinder; And a plurality of feed rollers that are in rolling contact with the outer peripheral surface of the steering shaft.

In addition, a guide groove is formed on the outer peripheral surface of the steering shaft so as to form a spiral inclined in the same direction as the feed roller, and engages with a rolling contact surface of the feed roller. The motor has an axis that is substantially parallel to the rotary cylinder, is attached to the outside of the housing, and is configured to transmit with the rotary cylinder via a transmission mechanism that reaches inside the housing, or It is characterized by comprising a rotor connected to the rotating cylinder and a stator provided around the inner periphery of the housing so as to surround the outside of the rotor.

In the present invention, the rotary cylinder arranged coaxially with the steering shaft rotates in the support housing of the steering shaft by transmission from the steering assist motor. The rotating cylinder is
It has a plurality of feed rollers that rotate around respective pivots that are inclined at the same angle in the circumferential direction with respect to the axis, and are in rolling contact with the outer peripheral surface of the steering shaft. Each of the rollers rolls on the outer peripheral surface of the steering shaft along a trajectory orthogonal to each other pivot, and the steering shaft is pressed by the axial component of the frictional force between each feed roller. To slide in the axial direction. The outer peripheral surface of the steering shaft
Any surface can be used as long as the feed roller can be rolled and contacted, and rails and other outer peripheral surface processing are not required. In assembling, it is only necessary to realize a reliable rolling contact state of each feed roller.

A spiral guide groove is formed on the outer peripheral surface of the steering shaft so as to be engaged with the rolling contact surface of the feed roller, and the rolling action of the feed roller is accompanied by sliding in the axial direction by the guiding action of the guide groove. And efficiently convert the rotation of the rotary cylinder into sliding of the steering shaft. In this case, it is necessary to machine the outer peripheral surface of the steering shaft for forming the guide groove. However, the guide groove does not require the same high precision as the rail of the ball screw, and the engagement of the feed roller during assembly is not required. Can be done easily.

A motor for assisting steering is mounted on the outside of the housing so as to have an axis substantially parallel to the steering shaft, and transmission from the motor to the rotary cylinder is realized through a transmission mechanism reaching inside the housing. I do. This transmission mechanism is, for example, a pinion attached to the output end of the motor and a spur gear integrally provided around the outer periphery of the rotating cylinder, directly or indirectly via an appropriate spur gear. The motor can be constituted by a simple meshed spur gear transmission mechanism, and the motor can be arranged close to the steering shaft housing to reduce the installation space of the steering assist motor including the transmission system.

In addition, a stator is provided around the inner periphery of a housing of the steering shaft, and a rotation assisting motor is integrally formed inside the housing by using a rotating cylinder disposed inside the stator as a rotor. I do. As a result, a transmission system to the motor and the steering shaft can be realized with little use of the space around the housing.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a partially cutaway front view showing a configuration of a main part of a power steering device according to the present invention, and FIG.
It is an expanded sectional view of a part.

The steering shaft (rack shaft) 1 is slidably supported in the axial direction inside a cylindrical housing 2 extending in the left-right direction of the vehicle body (not shown). Both ends of the steering shaft 1 projecting to both sides are respectively connected to left and right steering wheels (not shown) via separate tie rods 10 (only one side is shown), and sliding of the steering shaft 1 in the housing 2 is performed. , Are transmitted to the left and right steering wheels via the tie rods 10, 10 so that they are steered.

A pinion housing 3 is provided in the middle of the housing 2 in such a manner that the pinion housing 3 crosses the axis. A pinion shaft 4 is supported inside the pinion housing 3 so as to be rotatable around its axis. In FIG. 1, the pinion shaft 4 has only a projecting end protruding upward from the pinion housing 3, and is connected to a steering wheel (not shown) via the projecting end, and is operated according to an operation of a steering wheel for steering. It is designed to rotate around an axis.

A pinion (not shown) is integrally formed below the pinion shaft 4 extending inside the pinion housing 3. On the steering shaft 1 supported in the housing 2, rack teeth (not shown) are formed over an appropriate length including a crossing position with the pinion housing 3, and mesh with the pinion below the pinion shaft 4. The rotation of the pinion shaft 4 accompanying the operation of the steering wheel is converted into sliding in the longitudinal direction of the steering shaft 1 by the meshing of the pinion and the rack teeth, and the left and right steering connected to both ends of the steering shaft 1. The wheels constitute a rack and pinion type steering mechanism in which the wheels are steered according to the operation of the steering wheel.

The power steering apparatus according to the present invention is configured to assist the steering performed as described above by the rotational force of the electric motor. In the embodiment shown in FIGS. 1 and 2, the steering assist motor 5 is attached to the outside of the housing 2. The housing 2 is provided with a motor seat 50 protruding outward at one location in the circumferential direction at a position appropriately spaced from a continuous portion of the pinion housing 3. Is the axis of the housing 2
And is fixed to the motor seat 50 by a flange so as to be substantially parallel to the steering shaft 1 therein.

As shown in FIGS. 1 and 2, the interior of the motor seat 50 is a cavity communicating with the interior of the housing 2, and the output end of the motor 5 entering the cavity is provided with:
A drive pinion 51 is fixedly provided, and the drive pinion 51 is meshed with a spur gear 52 rotatably supported inside the motor seat 50.

On the other hand, inside the housing 2, a motor seat
The rotary cylinders 6 are accommodated corresponding to the 50 continuous parts.
The rotary cylinder 6 is a cylindrical member supported inside the housing 2 by a four-point contact ball bearing 60 integrally formed on one side of the rotary cylinder 6 so as to allow only coaxial rotation. The steering shaft 1 inserted inside the housing 2 is inserted inside the rotary cylinder 6.

A spur gear 61 is integrally formed on the outer side of the rotating cylinder 6 supported in this manner at a position corresponding to the continuous portion of the motor seat 50 in the axial direction, and is located at the same position from the motor seat 50 side. , And meshes with the spur gear 52 that enters the gear. Thus, the rotation cylinder 6 maintains the restrained position by the four-point contact ball bearing 60 by the rotation of the motor 5 transmitted through the pinion 51, the spur gear 52 and the spur gear 61, and is steered inside the housing 2. It rotates coaxially with the shaft 1.

The other end surface of the rotary cylinder 6, that is, a four-point contact ball bearing
Three feed rollers 7, 7, 7 are mounted on the end face opposite to the position supported by 60, and they are in rolling contact with the outer peripheral surface of the steering shaft 1 projecting to the same side. 1 and 2
, Only two feed rollers 7, 7 are shown. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. As is apparent from FIG. 3, the three feed rollers 7, 7, 7 Are rotatably supported around respective axes inclined at the same angle in the circumferential direction with respect to the axis of the rotary cylinder 6 at substantially equal intervals.

As the feed roller 7, a small-diameter ball bearing can be used. This is fixed to a screw hole formed at the end face of the rotary cylinder 6 at a predetermined inclination angle with respect to the axis. This is easily realized by screwing a set screw 70 and tightening and fixing the inner ring between the set screw 70 and the end face. FIG.
In the figure, the axis of the feed rollers 7, 7, 7 and the axis of the tip of each of the set screws 70, 70, 70 are indicated by dashed lines, and the feed rollers 7, 7, 7 And the inclination of the set screws 70, 70, 70, which are the pivots, are evident from the deviation of these axes.

Feed roller 7 using ball bearing
Is intended to reduce the manufacturing cost by using a general-purpose product, and the above-described fixing structure of the feed roller 7 is intended to simplify the assembly, and the structure and the fixing structure of the feed roller 7 are It is not limited to. The number of the feed rollers 7 needs to be plural in order to maintain the rolling contact state with respect to the peripheral surface of the steering shaft 1. When the number of the feeding rollers 7 is two, the direction connecting these rolling contact positions is set. The external contact force applied to the steering shaft 1 from a direction different from that described above may make it impossible to maintain a good rolling contact state.
Preferably, one or more feed rollers 7 are provided.

The rotary cylinder 6 is provided with a split groove 62 extending from the end face on the side where the feed rollers 7, 7, 7 are mounted on the rotary cylinder 6 in an appropriate length in the axial direction. As shown in FIG.
The rotary cylinder 6 is provided in such a manner that the rotary cylinder 6 is divided into a small half portion 6a including the mounting position of one feed roller 7 at the center thereof and a majority portion 6b including the mounting position of the other two feed rollers 7,7. It is. As shown in FIGS. 1 and 2, a pair of tightening bolts 63, 63 are arranged on the rotary cylinder 6 in the middle of the length range of the split groove 62 in a direction crossing the split groove 62. When these are tightened, the small half portion 6a and the majority portion 6b are brought closer to each other due to the decrease in the width of the split groove 62,
The pressing of the feed rollers 7, 7, 7 against the outer peripheral surface of the steering shaft 1 is strengthened.

With the above arrangement, when the rotary cylinder 6 is rotated by the transmission from the motor 5, the outer ring of the feed rollers 7, 7, 7 attached to the rotary cylinder 6 is in contact with the outer peripheral surface of the steering shaft 1. It rotates while maintaining the rolling contact state. FIG. 4 is an explanatory diagram of this rolling state.

The feed roller 7 has a pivot that is inclined with respect to the axis of the rotary cylinder 6 as described above. Rolling on the outer peripheral surface of the steering shaft 1 is indicated by a two-dot chain line in the figure. As described above, when the rotating cylinder 6 rotates in a direction indicated by an outline arrow when the rotating cylinder 6 rotates in a direction orthogonal to the pivot axis, the steering shaft 1 has a frictional force along the rolling contact track at the rolling contact portion of the feed roller 7. F acts. The steering shaft 1 is engaged with the pinion shaft 4 to
When the rotation about the axis is in a restrained state and the frictional force F acts on the circumferential surface of the axis, the axial component F ₁
And slides in the axial direction.

As described above, in the power steering apparatus according to the present invention, the rotation of the rotation assisting motor 5 causes the rotation cylinder 6 to rotate inside the housing 2 and is attached to the other side with this rotation. When the feed rollers 7, 7, 7 roll on the outer peripheral surface of the steering shaft 1, the steering shaft 1 slides, and the steering performed as described above is assisted in accordance with the sliding. The feed rollers 7, 7, 7 only roll on the outer peripheral surface of the steering shaft 1, do not require any outer peripheral surface processing, and can reduce processing man-hours.
There is no danger that the strength will be reduced.

In the above configuration, when the rolling of the feed rollers 7, 7, 7 is converted into the sliding of the steering shaft 1, there is a slight slip on the rolling contact surface between the two, and the existence of this slip is accompanied. In addition, there is a problem that the rotation amount of the steering assist motor 5 and the sliding amount of the steering shaft 1 do not exactly correspond to each other. The driving of the motor 5 is performed based on the detection result of the steering torque applied to the steering wheel, and the correspondence between the rotation amount of the motor 5 and the sliding amount of the steering shaft 1 has a small effect on the steering assist, but the slippage of the slip is small. It is important to reduce it.

The slippage is caused by adjusting the amount of tightening of the pair of tightening bolts 63 provided on the rotary cylinder 6 to appropriately adjust the rolling contact pressure of the feed rollers 7, 7, 7 to the outer peripheral surface of the steering shaft 1. It can be reduced by maintaining it, and reduced by a structural device such as using a high friction roller having a non-slip member such as a rubber material attached to the outer periphery of the feed roller 7, 7, 7. be able to.

Further, as a countermeasure to reduce the slip, it is effective to apply traction grease to the rolling contact surface between the steering shaft 1 and the feed rollers 7, 7, 7. Traction grease is a synthetic lubricating oil containing polycyclic condensed saturated hydrocarbon as a main component. It has the property of generating an oil film (glassy solid film) with large shear resistance under the action of pressure. Is used to increase the frictional resistance of the contact surface to improve the transmission efficiency and to reduce the wear due to direct contact.

The application of the traction grease may be performed on the outer peripheral surface of the steering shaft 1 over the entire area where the traction grease may come into contact with the feed rollers 7, 7, and 7. By the action of the traction grease, the occurrence of the slip can be effectively reduced.

The steering assist motor 5 is driven based on the result of detection of the steering torque applied to the steering wheel for steering. The steering torque is detected by a torque sensor 8 (see FIG. 1) configured inside the pinion housing 3. Inside the pinion housing 3, the pinion shaft 4 is divided into an upper shaft including an upwardly projecting end connected to the steering wheel and a lower shaft including the pinion, and is coaxially connected by a torsion bar (not shown). The torque sensor 8 is a known sensor that detects a steering torque applied to a steering wheel for steering using a relative angular displacement generated between the upper shaft and the lower shaft with the torsion of the torsion bar as a medium. FIG. 1 only shows a terminal box for supplying power to the torque sensor 8 and extracting output.

FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the present invention. In this drawing, the configuration of the steering assisting motor 5, the rotary cylinder 6, and the transmission system between them are the same as those of the embodiment shown in FIGS. 1 and 2, and the same reference numerals are given and the description is omitted. . At one end of the rotary cylinder 6, three feed rollers 7 a, 7 a, 7 a (only two are shown) are inclined at equal angles in the circumferential direction with respect to the axis of the rotary cylinder 6 in the same direction. Each of the setscrews 70, 70, 70 is rotatably supported by these as pivots.

As the three feed rollers 7a, 7a, 7a, a small-diameter ball bearing similar to the embodiment shown in FIGS. 1 and 2 can be used.
Each of the outer races is provided with a ridge 71, 71, 71 which is provided at substantially the center in the width direction of the outer peripheral surface over the entire circumference.
Feed rollers 7a, 7a, 7a of the rotary cylinder 6
In the same direction as the direction of the inclination, a spiral guide groove 11 inclined at an angle equal to these is formed, and the ridge 7 is formed.
Each of 1, 71 and 71 is engaged with this guide groove 11.

Feed rollers 7a, 7 at the end of the rotary cylinder 6
The pivotal positions of a and 7a are set to be shifted in the axial direction in order to engage them with the common guide groove 11. FIG.
It is a figure which shows the end part of the rotating cylinder 6 linearly developed in the circumferential direction,
As shown in this figure, the feed roller 7a,
Three mounting seats 6c, 6c, for mounting 7a, 7a
6c has a seating surface having an angle equal to the inclination angle of the guide groove 11 on the outer peripheral surface of the steering shaft 1 and is provided so as to be substantially equally distributed in the circumferential direction, and each of the feed rollers 7a, 7a, 7a The inner rings are fixed to the end face of the rotary cylinder 6 and are pivotally supported by the set screws 70, 70, 70 so as to be substantially parallel to the seating surfaces of the other mounting seats 6c, 6c, 6c.

The mounting seats 6c, 6c, 6c are provided as protrusions protruding outside the end face of the rotary cylinder 6 or cutouts cut inward as shown in the figure, and as shown in FIG. The feed rollers 7a, 7a, 7a pivotally supported by these
They are arranged on the same straight line in the circumferential direction. Steering axis 1
The guide groove 11 on the outer peripheral surface is formed so as to have an inclination angle substantially coinciding with the line of the feed rollers 7a, 7a, 7a, and the formation of such a guide groove 11 and the feed rollers 7a, 7a, 7a By the attachment, the two can be engaged collectively.

In the above configuration, similarly to the configuration shown in FIGS. 1 and 2, the rotary cylinder 6 rotates by the transmission from the steering assist motor 5, and the feed roller 7a attached to the rotary cylinder 6 is rotated. , 7a, and 7a roll on the outer peripheral surface of the steering shaft 1, and the steering shaft 1 is pressed and slid in the axial direction by the action of an axial component force generated by the rolling. The steering is assisted in accordance with the sliding. At this time, the feed rollers 7a, 7a, 7a are provided with the respective projections 71, 71, 71 which engage with the guide grooves 11 formed on the outer peripheral surface of the steering shaft 1. The movement in the axial direction is restrained by the action, and there is no danger that the rolling will involve sliding in the axial direction between the steering shaft 1 and the rotation of the rotary cylinder 6. And the amount of rotation of the steering shaft 1 and the amount of rotation of the steering assist motor 5 accurately correspond to each other. A steering auxiliary operation is performed.

On the other hand, in the configuration shown in FIG. 5, the outer peripheral surface of the steering shaft 1 needs to be worked to form the guide groove 11, and this guide groove 11 is provided around the feed rollers 7a, 7a, 7a. What is necessary is just to be able to engage with the projected ridges 71, 71, 71,
High processing accuracy equivalent to the ball screw rail is not required,
As described above, the guide groove 11 with which the three feed rollers 7a, 7a, 7a are engaged is shared, so that a single guide groove 11 may be formed on the outer peripheral surface of the steering shaft 1. Processing is easy.

The feed rollers 7a, 7a, 7a are engaged with the guide grooves 11 through ridges 71, 71, 71 provided around the respective outer races. The outer races of the feed rollers 7a, 7a, 7a May be configured to engage with the guide groove 11 over the entire width. Alternatively, the guide groove 11 may not be common, and the guide grooves 11 with which the respective feed rollers 7a, 7a, 7a engage may be separately provided. Furthermore, in this configuration,
By applying traction grease to the guide groove 11 which is in rolling contact with the feed rollers 7a, 7a, 7a, it is possible to improve transmission efficiency and reduce wear of the contact surface.

FIG. 7 is an enlarged sectional view of a main part showing still another embodiment of the present invention. In this drawing, the rotary cylinder 6 is accommodated in the housing 2 with its substantially central portion supported by a four-point contact ball bearing 60, and a spur gear 61 integrally formed on one side of this support portion is replaced with a spur gear 61. It is configured to mesh with a pinion 51 at the output end of the motor 5 via 52. The outer ring of each of the three feed rollers 7, 7, 7 pivotally supported at the engagement portion and the extended ends on both sides of the support portion is used as a steering shaft 1.
Is rolled on the outer peripheral surface of.

According to this configuration, three feed rollers 7, 7, 7 are provided on the outer peripheral surface of the steering shaft 1 at two positions in the axial direction.
Since the rotation of the motor 7 causes the sliding of the steering shaft 1 in the axial direction accompanying the rotation of the motor 5 to be reliably performed, the load of each feed roller 7 at this time can be kept small,
The above-described stable operation with less slippage is possible. The number of the feed rollers 7, 7, 7 arranged in the axial direction can be three or more pairs. Further, traction grease is applied to the rolling contact surface, and / or the outer peripheral surface of the steering shaft 1 is shown in FIG. It is also possible to carry out the formation of the engaging groove 11 similar to the above.

In the above embodiment, the steering assist motor 5 can be arranged outside the housing 2 of the steering shaft 1 and close to the housing 2. Since there is no need to increase the diameter to secure the strength of the steering shaft 1 and the housing 2 without reducing the strength, the required space around the housing 2 can be reduced and a compact arrangement is possible. .

FIG. 8 is an enlarged sectional view of a main part showing still another embodiment of the present invention. In this figure, the rotary cylinder 6 is extended to the side of a four-point contact ball bearing 60 for supporting the housing 2, and the other side is outside the extension 65 of the rotary cylinder 6 supported by the ball bearing 64. A rotor 5a is integrally provided, and a stator 5b is provided on the inner peripheral surface of the housing 2 surrounding the outer peripheral portion of the rotor 5a. .

In this configuration, the rotary cylinder 6 is rotated by the torque of the motor 5 directly applied to the extension 65. Three feed rollers 7, 7, 7 are pivotally supported at one end of the rotary cylinder 6, similarly to the above-described embodiment, and each outer wheel is brought into rolling contact with the outer peripheral surface of the steering shaft 1. The rotation of the rotary cylinder 6 is converted into sliding in the axial direction of the steering shaft 1 via the feed rollers 7, 7, 7.

According to this configuration, the steering assist motor 5 is provided on the inside of the housing 2 so as to be coaxial with the steering shaft 1. Therefore, the outer periphery of the rotor 5a and the stator 5b is provided on the outside of the housing 2. For this reason, only a large diameter portion required is generated, and the necessary space around the housing 2 can be further reduced, and a more compact arrangement can be achieved. In this configuration, it is also possible to simultaneously apply traction grease to the rolling contact surface and / or form the engagement groove 11 on the outer peripheral surface of the steering shaft 1 as in FIG.

In the above embodiment, the case where the steering shaft 1 is the rack shaft in the rack and pinion type steering mechanism has been described, but the steering shaft 1 is operated in accordance with the sliding in the axial direction. The shaft may be any shaft that steers the turning wheels, and is not limited to the rack shaft. For example, in some power steering devices, a sliding shaft dedicated to steering assistance is provided separately from a rack shaft, and the sliding shaft and the rack shaft are connected in a part thereof, and a steering assist motor is provided. Is transmitted to a rack shaft via a sliding shaft, such a sliding shaft is also included in the steering shaft in the present invention. Further, the scope of the present invention is not limited to the rack and pinion type steering mechanism described above, and it is needless to say that the present invention can be applied to other types of steering mechanisms.

[0050]

As described above in detail, in the power steering apparatus according to the present invention, the rotating cylinder arranged coaxially with the steering shaft rotates by the transmission from the steering assist motor, and is attached to the rotating cylinder. Since the plurality of feed rollers are in contact with the outer peripheral surface of the steering shaft and apply a sliding force to the steering shaft in the axial direction, the outer peripheral surface of the steering shaft may be any surface that can be in contact with the feed roller. No processing is required, and when assembling, it is only necessary to realize a reliable rolling contact state of each feed roller, and the rotation of the steering assist motor with a simple configuration slides in the longitudinal direction of the steering shaft. Can be reliably converted.

Since a spiral guide groove engaging with the rolling contact surface of the feed roller is formed on the outer peripheral surface of the steering shaft, the action of the guide groove allows the feed roller to move on the outer peripheral surface of the steering shaft. Rolling can be generated without sliding in the axial direction, and the rotation of the steering assist motor is efficiently and accurately converted to the sliding of the steering shaft, and reliable steering assist is possible. On the other hand, machining of the outer peripheral surface of the steering shaft for forming the guide groove does not require high precision equivalent to that of a ball screw rail, and simplification of the configuration is achieved.

Further, the steering assist motor can be arranged close to the outside of the housing via a transmission mechanism for transmitting rotation to the rotary cylinder. Further, a stator is provided around the inner periphery of the housing of the steering shaft. By using the rotating cylinder arranged inside the motor as a rotor, the motor can be integrally configured inside the housing, so that the space for disposing the steering assist motor including the transmission system can be greatly reduced. The present invention has an excellent effect, for example, it can occupy a small space around the housing of the steering shaft and can be made compact.

[Brief description of the drawings]

FIG. 1 is a partially broken front view showing a configuration of a main part of a power steering device according to the present invention.

FIG. 2 is an enlarged sectional view of a part of FIG.

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2;

FIG. 4 is an operation explanatory view of the power steering device according to the present invention.

FIG. 5 is a main part enlarged sectional view showing another embodiment of the power steering apparatus according to the present invention.

FIG. 6 is an explanatory diagram of a mounting mode of a feed roller, in which an end of a rotary cylinder is linearly developed in a circumferential direction.

FIG. 7 is an enlarged sectional view of a main part showing another embodiment of the power steering apparatus according to the present invention.

FIG. 8 is an enlarged sectional view of a main part showing another embodiment of the power steering apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 steering shaft 2 housing 5 motor 6 rotating cylinder 7 feed roller 7a feed roller 11 engaging groove 71 convex ridge

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Masahide Nakamura 3-5-8, Minamisenba, Chuo-ku, Osaka-shi, Osaka Prefecture Inside of Koyo Seiko Co., Ltd. (72) Manabu Takaoka 3-5-2, Minamisenba, Chuo-ku, Osaka-shi, Osaka No. 8 Koyo Seiko Co., Ltd.

Claims (4)

[Claims] 1. A structure for transmitting a rotational force of a motor driven in accordance with a steering operation to a steering shaft supported in a cylindrical housing, and sliding the steering shaft in an axial direction to assist steering. In the electric power steering device,
A rotating cylinder that is supported inside the housing by restraining movement in the axial direction and that rotates coaxially with the steering shaft by transmission from the motor, and a part of the rotating cylinder, A power steering device comprising: a plurality of feed rollers rotatably supported around respective axes inclined at the same angle in the same circumferential direction and rotatably contacting the outer peripheral surface of the steering shaft. . 2. The motive power according to claim 1, further comprising a guide groove formed on the outer peripheral surface of the steering shaft in a spiral shape inclined in the same direction as the feed roller, and engaging with a rolling contact surface of the feed roller. Steering gear. 3. The motor has an axis substantially parallel to the rotary cylinder and is mounted outside the housing.
The power steering device according to claim 1 or 2, wherein the power steering device is configured to be transmitted to the rotary cylinder via a transmission mechanism that reaches inside the housing. 4. The motor according to claim 1, wherein the motor includes: a rotor connected to the rotary cylinder; and a stator provided around an inner periphery of the housing so as to surround an outer side of the rotor. A power steering device as described in the above.