JPH0699820A - Power steering device - Google Patents

Abstract

PURPOSE:To mitigate degradation of steering sense due to the effect of the inertia of a motor for auxiliary steering, and to improve the entire efficiency in a simple structure. CONSTITUTION:An outer roller 33 of a planetary roller reduction gear 13 arranged between an output shaft 8a of a motor for auxiliary steering and a transmission shaft 7 to a steering mechanism, is rotatively supported between a pair of side plates 37 and 38 through thrust needle bearings 39a, 39b. An external gear tooth 33a is formed on the outer periphery of the outer roller 33, and a pinion 10 biting into this is fixed to the outer shaft of a variable motor 9, and the outer roller 33 is rotated and driven around the axis of the planetary roller reduction gear 13 by the rotation of the variable speed motor 9. When the outer roller 33 is rotated in the same direction as the revolving direction of planetary rollers 32, 32... around a revolving axis of a transmission shaft 7, the reduction ratio of the planetary roller reduction gear 13 becomes smaller, and when the outer roller 33 is rotated in the reverse direction, the reduction ratio of the planetary roller reduction gear 13 becomes larger, and the auxiliary steering force transmitted to the transmission shaft 7 is thus increased or reduced.

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 steering assist force, and more specifically, transmission from a steering assist motor to a steering mechanism. The present invention relates to a power steering apparatus including a planetary speed reducer for increasing the output of the motor in the middle of the system.

[0002]

2. Description of the Related Art In recent years, an electric power steering apparatus using an electric motor as a source of a steering assist force has been put into practical use. This is to drive a steering assisting motor arranged in the middle of the steering mechanism based on the detection result of the steering torque, assist the operation of the steering mechanism by the rotational force of the motor, and operate the steering wheel for steering ( This is to reduce the labor load required for operating the steering wheel).

When compared with a hydraulic power steering apparatus that uses a hydraulic actuator as a source of a steering assist force, such an electric power steering apparatus has various driving conditions such as high and low vehicle speeds and steering frequency. Although it has the advantage that it is easy to control the assisting force characteristics according to the requirements, it is difficult to obtain a small motor that can generate sufficient rotational force for assisting steering, and consumes a large current to obtain sufficient rotational force. When a large-sized motor is used, it is difficult to secure the position where the motor is arranged around the steering mechanism, and there is a problem that a control unit capable of handling a large current is required.

Therefore, conventionally, a reduction gear is provided in the middle of the transmission system from the steering assisting motor to the steering mechanism, and the output of the motor is increased by the force increasing action of the reduction gear and transmitted to the steering mechanism. The power steering device that solves the above-mentioned drawbacks has been put into practical use. As the speed reducer, a large reduction ratio can be obtained and the size can be easily reduced. A planetary type speed reducer such as a speed reducer is often used. As is known, a planetary speed reducer is an inner ring (sun gear or sun roller) arranged coaxially.
A plurality of planet wheels (planetary gears or planet rollers) rollingly contacting each of these are arranged between the outer ring and the outer ring, and in the power steering apparatus, the outer ring is a fixed ring fixed to a housing, and a motor is provided. The operation mode is generally adopted in which the output of the above is given to the inner ring and the power transmitted to the steering mechanism is taken out on the revolution axis of the planet wheels.

[0005]

However, in the electric power steering apparatus configured as described above, when returning to the neutral position caused by the reverse input from the steering mechanism,
Friction (loss torque) and inertia of the rotating portion of the motor acting through the reducer cause a delay in the start of the operation, and the convergence to the neutral position is obstructed, which causes a deterioration in steering feeling. . This difficulty is due to placing an electromagnetic clutch between the motor and the speed reducer, during the return operation of the steering wheel, etc.
The problem can be solved by disconnecting the motor from the steering mechanism when the steering assist force is not required, but a new control is required for engaging and disengaging the electromagnetic clutch, which causes a problem that the configuration of the control unit becomes complicated.

On the other hand, the steering assist motor is set on the basis of the required output at the time of steering wheel operation in a stopped state where the maximum steering assist force is required, so-called stationary steering,
During normal traveling, in order to obtain the assisting force characteristic according to the traveling state, it is the current situation that the drive current of the motor is adjusted in a range significantly lower than the rating, and in the range of low efficiency, There is a lot of waste of power consumption due to the use of motors,
It has a drawback that the efficiency of the entire system is low.

In order to solve the above problems, JP-A-62-12
According to Japanese Patent Laid-Open No. 0272, a two-stage switching type speed reducer is provided in the middle of a transmission system from a steering assisting motor to a steering mechanism, and a sufficient steering assisting force is obtained by switching to a large deceleration side during stationary steering. During normal driving, switching to a small deceleration side enables the use of a motor near the rated value to improve the efficiency of the system and to reduce the deterioration of steering feeling due to the inertia of the motor. A device is disclosed.

However, the speed reducer has a structure in which one of the two gear devices having different reduction ratios is selectively interposed between the motor and the steering mechanism by the engagement / disengagement operation of each electromagnetic clutch. Therefore, as is apparent from the above-mentioned publication, it is inevitably bulky and, in addition, the efficiency of the assist force according to the running state within the entire control range is improved by switching the reduction ratio between two stages. However, the power steering device disclosed in Japanese Unexamined Patent Publication No. Sho 62-120272 is of poor practicality.

The present invention has been made in view of the above circumstances, and has a simple structure that can alleviate the deterioration of the steering feeling due to the influence of the inertia of the steering assisting motor and can improve the overall efficiency. It is intended to provide a steering device.

[0010]

A power steering apparatus according to the present invention is a planetary speed reducer for increasing the output of a motor for assisting steering in the middle of a transmission system for transmitting the output of the motor to a steering mechanism. A power steering apparatus including: a drive unit for rotating the outer ring of the speed reducer about the axis of the speed reducer.

[0011]

In the present invention, the output of the steering assisting motor is applied to the inner wheels so that the power transmitted to the steering mechanism is decelerated and taken out on the revolution axis of the planet wheels. The ring is driven to rotate about the axis of the speed reducer by a driving unit such as a motor, and the reduction ratio is continuously increased or decreased according to the rotation.

[0012]

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 vertical sectional view showing a main part of a power steering apparatus according to the present invention. In the figure, 1 is the upper axis,
Reference numeral 2 is a lower shaft, which is rotatably supported inside a common housing 4 having a cylindrical shape, and is coaxially connected through a torsion bar 3 fitted in the shaft center portion. There is.

The upper shaft 1 has its upper end linked to a steering wheel (not shown) so as to rotate in response to a turning operation of the steering wheel. Also the lower shaft 2
Has a pinion 2a on the outer periphery near the lower end, and the pinion 2a is engaged with a rack shaft 5 that intersects with the lower shaft 2 at the lower part of the housing 4. Both ends of the rack shaft 5 are connected to left and right steering wheels (not shown) so that steering can be performed according to movement of the rack shaft 5 in the axial direction. Upper shaft 1
The rotation of the lower shaft 2 and the lower shaft 2 is converted into movement of the rack shaft 5 meshing with the pinion 2a in the axial direction of the rack shaft 5, and is transmitted to the steering wheels on the left and right to steer the rack and pinion type steering mechanism. I am configuring.

During steering as described above, the reaction force from the road surface on which the steered wheels contact the ground acts on the lower shaft 2 via the rack shaft 5, so that the upper shaft 1 and the lower shaft 2 are connected. The torsion bar 3 is twisted corresponding to the magnitude and direction of the steering torque applied to the steering wheel. A torque sensor 6 for detecting the steering torque applied to the steered wheels through the torsion of the torsion bar 3 is provided at the connecting portion between the upper shaft 1 and the lower shaft 2 inside the housing 4.

A cylindrical transmission housing 40 is provided in the middle of the housing 4 so as to project outward. The transmission housing 40 includes a speed reducer housing 40a on the housing 4 side and a clutch housing 40b coaxially fitted on the other side of the speed reducer housing 40a. A transmission shaft 7 is coaxially supported on the side of the speed reducer housing 40a that is continuous with the housing 4, and a small bevel gear 7a is fitted to the extension end of the transmission shaft 7 into the housing 4. The small bevel gear 7a is fixed, and is meshed with the large bevel gear 7b fitted to the outer periphery of the lower shaft 2 in the middle thereof.

At the other open end of the clutch housing 40b, an auxiliary motor 8 is driven based on the steering torque detection result of the torque sensor 6 to generate a steering assist force.
Is fixed. The output shaft 8a of the auxiliary motor 8 protruding inside the clutch housing 40b is coaxially opposed to the other end of the transmission shaft 7. An intermediate transmission shaft is placed between these facing parts.
11 are arranged, and between the output shaft 8a and the intermediate transmission shaft 11,
An electromagnetic clutch 12 for engaging and disengaging the output of the auxiliary motor 8 is configured, and between the transmission shaft 7 and the intermediate transmission shaft 11, the planetary roller speed reducer 13 that boosts the output of the auxiliary motor 8 and transmits it to the transmission shaft 7. Is configured.

Then, the rotational force of the auxiliary motor 8 driven based on the detection result of the torque sensor 6 is taken out to the transmission shaft 7 via the electromagnetic clutch 12 and the planetary roller speed reducer 13, and further the small bevel gear. After being transmitted to the lower shaft 2 via the 7a and the large bevel gear 7b meshing with the 7a, the pinion 2a and the rack shaft 5
When the rack shaft 5 is meshed with the rack shaft 5, it is converted into a sliding force (steering assist force) in the axial direction of the rack shaft 5, and the steering operation performed as described above is assisted by the rotational force of the auxiliary motor 8.

FIG. 2 is an enlarged sectional view of the inside of the transmission housing 40. As shown in the drawing, at the end of the output shaft 8a of the auxiliary motor 8 projecting inward of the clutch housing 40b, a thick disk-shaped holding body 20 forming a part of the electromagnetic clutch 12, and
At the end of the transmission shaft 7 inside the speed reducer housing 40a, a thick disk-shaped carrier 30 forming a part of the planetary roller speed reducer 13 is coaxially spline-coupled (or press-fitted). The intermediate transmission shaft 11 between the two shafts 7 and 8a is supported on both sides by ball bearings fitted and fixed to the shaft center portions of the holding body 20 and the carrier 30, respectively. Movement in the axial direction is restricted.

First, the structure of the electromagnetic clutch 12 inside the clutch housing 40b will be described. The electromagnetic clutch 12
The holding body 20 splined (or press-fitted) to the tip of the output shaft 8a of the auxiliary motor 8, and the clutch housing.
The drive coil 21 that is fitted and fixed to the inner periphery of 40b and faces one side of the holding body 20, and the other side of the holding body 20 that is spline-coupled (or press-fitted and fixed) to the outer periphery of the output shaft 8a side of the intermediate transmission shaft 11. And a disk-shaped armature 22 facing each other.

As shown in the figure, a friction plate 22a is fixed to the surface of the armature 22 facing the holding body 20 by means of rivets at a plurality of positions in the circumferential direction through thin movable plates 22b. The plate 22a is opposed to the friction plate 20a fixed to the surface of the holding body 20 facing the armature 22 with a predetermined gap. On the other hand, the drive coil 21 on the other side of the holding body 20 is
Is located in the concave portion formed on the facing surface of the concave portion and faces the bottom surface of the concave portion with a minute gap.

Thus, in the electromagnetic clutch 12 constructed as above, when the drive coil 21 is demagnetized,
If only the holding body 20 is in the shut-off state in which it rotates in conjunction with the output shaft 8a, and conversely the drive coil 21 is excited, the holding body 20
By the action of the magnetic field formed in the vicinity of the armature 22 via the friction plate 22a of the armature 22 is attracted to the holding body 20 side with the flexible deformation of the movable plate 22b, and the friction plate 22a and the friction plate 20a are brought into sliding contact. The auxiliary motor 8 is engaged.
The output of the intermediate transmission shaft passes through the holder 20 and the armature 22.
Propagated to 11.

Next, the structure of the planetary roller reducer 13 inside the reducer housing 40a will be described. The planetary roller speed reducer 13 includes a sun roller (inner ring) 31 formed by enlarging a part of the intermediate transmission shaft 11 on the transmission shaft 7 side, and a plurality of planetary rollers (planetary rollers) that are in rolling contact with the outer periphery of the sun roller 31. Ring) 32, 32 ...
And an annular outer roller (outer ring) 33 whose inner circumference is brought into rolling contact with these planetary rollers 32, 32 ... FIG. 3 is a front view of the planetary roller reducer 13 showing the positional relationship between the rollers.

The planetary rollers 32, 32, ... Are fitted to the respective pivot shafts 34, 34, which are provided on the carrier 30 at the end of the transmission shaft 7 so as to project, and form a single row on the fitting circumference of both. Many supporting balls lined up
It is supported via 35, 35 ..., It is designed to be able to revolve around the axis of the transmission shaft 7 together with the carrier 30 while rotating around the pivot shafts 34, 34. As shown in FIG. 2, the support ball 3
5, 35 ... Are the inner circumferences of the planetary rollers 32, 32 ... and the pivots 34, 3
Fitted in a groove formed on the outer circumference of 4 ..., it acts to restrain movement of the planetary rollers 32, 32 ... In the axial direction due to rotation and revolution.

Also, the outer roller 33 is a reducer housing 40a.
By tightening the nut ring 36 that is screwed onto the inner circumference of the opening end side of the plate, it is sandwiched between the side plates 37 and 38 of the hollow disk shape laminated on both sides, and as shown in FIG. Outer roller 33
Thrust needle bearings 39a and 39b are respectively interposed between the side surfaces of and. That is, the outer roller 33 is supported in the axial direction by thrust needle bearings 39a, 39b, and is radially supported by the planetary rollers 32, 32, ... 31 and planet rollers 32, 32 ... Can rotate on the same axis as the revolution axis. A nut having a self-locking function, a so-called self-locking nut may be used as the nut ring 36, and instead of the nut ring 36, a wave washer or a disc spring abutted in the axial direction of the shielding plate 41 is stopped. You may employ the structure fixed by a ring. In these cases, preload can be applied to the thrust needle bearings 39a, 39b.

Outer teeth 33a are formed on the outer circumference of the outer roller 33 thus supported over the entire circumference. A pinion housing 40c, which faces the outer circumference of the outer roller 33 and has an internal cavity that opens to the opposite side of the clutch housing 40b, is continuously provided at an appropriate position outside the speed reducer housing 40a. Has a variable speed motor 9 fixed to a flange. The clutch housing 40b and the pinion housing 40c may be integrally molded. A pinion 10 is fitted and fixed to the output shaft of the transmission motor 9 protruding inside the pinion housing 40c, and the pinion 10 is meshed with the outer teeth 33a on the outer periphery of the outer roller 33. That is, the outer roller 33 of the planetary roller speed reducer 13 transmits the speed change motor 9 to the outer teeth 33a formed on the outer circumference of the planetary roller speed reducer 13 via the pinion 10.
Is rotated and driven around its own axis that is coaxial with the revolution axes of the sun roller 31 and the planet rollers 32, 32.

Between the outer side plate 38 that holds the outer roller 33 of the planetary roller speed reducer 13 and the nut ring 36, a thin hollow disk-shaped shield plate 41 is held. A seal ring 42 made of an elastic material such as rubber is circumferentially attached to the inner peripheral edge of the shield plate 41 reaching near the boss portion of the armature 22, and the seal ring 42 is connected to the boss portion of the armature 22. It is elastically contacted with one surface of a seal plate 43 which is fixed by pressure between it and the sun roller 31. On the side opposite to the rolling contact surface of the outer roller 33, the inner side plate 37 is provided with a speed reducer housing 40a.
The seal ring 44 fitted inside is fixed by clamping. The seal ring 44 is made of an elastic material such as rubber, and the lip portion protrudingly provided on the inner periphery is the outer peripheral surface of the carrier 30 and the planetary roller.
It is elastically contacted with the surface facing 32, 32 ...

That is, on one side of the installation site of the planetary roller speed reducer 13, a shield plate elastically contacted via the seal ring 42 is provided.
41 and the seal plate 43, and on the other side, a seal ring 44 interposed between the reducer housing 40a and the carrier 30.
However, the sun roller 31, the planetary roller 32, and the outer roller 33 each function as a sealing means, and maintain a reliable rolling contact with each other by the effect of the lubricating grease sealed by the sealing means on both sides. It can rotate smoothly. On the other hand, the lubrication grease enclosed in the planetary roller reducer 13 is almost completely blocked from leaking out to the location where the electromagnetic clutch 12 is arranged.As a result, malfunction of the electromagnetic clutch 12 due to the adhesion of grease is prevented. It can be surely prevented.

In the power steering apparatus according to the present invention constructed as described above, the electromagnetic clutch 12 is normally in the engaged state, and the auxiliary motor 8 is driven based on the detection result of the torque sensor 6. The rotational force is taken out to the transmission shaft 7 via the intermediate transmission shaft 11 and the planetary roller speed reducer 13, and is applied to the steering mechanism as a steering assist force as described above. Note that the electromagnetic clutch 12 is disengaged when the motor lock occurs in the auxiliary motor 8 to disconnect the auxiliary motor 8 from the steering mechanism and prevent the steering impossible state from occurring.

As described above, the planetary roller speed reducer 13 revolves around the axis of the transmission shaft 7 together with the sun roller 31 formed in the middle of the intermediate transmission shaft 11 to which the output of the auxiliary motor 8 is transmitted and the carrier 30. It is equipped with planetary rollers 32, 32 ...
The rotational force of the auxiliary motor 8 transmitted to the sun roller 31 is taken out to the transmission shaft 7 which is the revolution axis of the planet rollers 32, 32 ..., However, in the power steering apparatus according to the present invention, The outer roller 33 rolling on the outside of the planetary rollers 32, 32 ... Is not a fixed ring as in the prior art, but can be rotationally driven by the transmission motor 9.

First, the transmission motor 9 is locked to lock the outer roller.
If 33 is fixed, the planetary roller reducer 13
31. The planetary rollers 32, 32, ... and the outer roller 33 have a predetermined reduction ratio determined by the effective diameters of the respective rollers, and the output of the auxiliary motor 8 is transmitted to the transmission shaft 7 after being boosted to approximately the reciprocal of this reduction ratio. To be done. On the other hand, when the transmission motor 9 is rotationally driven at a predetermined speed and the outer roller 33 is rotated in the same direction as the revolution direction of the planet rollers 32, 32, ..., This rotation is the revolution speed of the planet rollers 32, 32. That is, since it acts to increase the rotational speed of the transmission shaft 7 on the output side of the planetary roller reducer 13, the planetary roller reducer 13 has a reduction ratio smaller than the original reduction ratio and the auxiliary motor 8 The output is transmitted to the transmission shaft 7 after reducing the degree of boosting. On the contrary, the outer roller 33 is rotated in the opposite direction of the revolution of the planet rollers 32, 32 ...
When is rotated, the planetary roller speed reducer 13 has a speed reduction ratio larger than the original speed reduction ratio, and the output of the auxiliary motor 8 is transmitted to the transmission shaft 7 with an increased degree of increase.

In the above-described operation, the degree of increase in the power transmitted to the transmission shaft 7 changes (decreases or increases) in accordance with the increase in the rotation speed of the outer roller 33, so that the drive current of the transmission motor 9 is controlled. By changing the rotation speed, it is possible to realize an appropriate degree of boosting force according to the running state. For example, the shift motor 9 is controlled based on the detection result of the vehicle speed, and the rotation speed of the outer roller 33 is changed to increase the degree of boosting during stationary steering to obtain a large steering assist force and reduce the labor burden for steering. While reducing as much as possible, reduce the amount of boosting during running to realize a small reduction ratio, delay in the return operation to the neutral position caused by the reverse input from the steering mechanism, and convergence to the neutral position. It is possible to reduce the delay and suppress the deterioration of the steering feeling.

Since the rotation speed of the transmission motor 9 can be continuously changed by controlling the drive current, the steering assist force transmitted from the transmission shaft 7 to the steering mechanism makes the output of the auxiliary motor 8 constant. It will be possible to change steplessly while keeping it, finer characteristic control according to the high and low of the vehicle speed, and further,
It is possible to perform characteristic control according to other traveling conditions such as steering frequency. During this period, the output (driving current) control based on the detection result of the torque sensor 6 is only performed in the auxiliary motor 8 that is the source of the steering assist force, and the auxiliary motor 8 always operates at a high level near the rated point. Being operated within the range of efficiency, the overall efficiency of the system can be greatly improved.

Since the rotation direction of the outer roller 33 can be freely set by driving the transmission motor 9 in the forward and reverse directions, the method of changing the boosting ratio and the speed reduction ratio is the two methods described above, namely, the outer roller 33.
Is rotated in the same direction as the revolution direction of the planet rollers 32, 32,
Either a method of reducing the boosting ratio and the reduction ratio by this rotation or a method of rotating the outer roller 33 in the direction opposite to the revolving direction and increasing the boosting ratio and the reduction ratio by this rotation may be adopted. For this reason, it is desirable to adopt the latter method of driving the variable speed motor 9 at the time of stationary steering with a low frequency of occurrence. That is, in order to alleviate the delay of the returning operation to the neutral position and the delay of the convergence caused by the reverse input from the steering mechanism, the planetary roller speed reducer 13 having a relatively small original reduction ratio is used,
When a large steering assist force is required, such as during stationary operation, the speed change motor 9 is driven to rotate the outer roller 33 to increase the speed reduction ratio and the force increase ratio.

In these embodiments, the rack
The configuration in which the rotational force of the auxiliary motor 8 for steering assist is transmitted to the middle of the lower shaft 2 connected to the pinion 2a of the pinion type steering mechanism has been described, but the rotation of the auxiliary motor 8 to other parts of the steering mechanism has been described. The present invention can be applied to a structure that transmits force.

Further, in the present embodiment, the configuration in which the planetary roller speed reducer 13 is provided in the middle of the transmission system from the auxiliary motor 8 to the steering mechanism has been described. However, instead of the planetary roller speed reducer 13, a planetary gear speed reducer is used. Can also be used. Further, the transmission means from the speed change motor 9 to the outer roller 33 is not limited to the meshing of the pinion 10 and the outer teeth 33a shown in this embodiment. For example, the outer roller 33 is a worm wheel and the speed change motor 9
Other transmission means, such as a structure in which it is meshed with a worm formed on the output shaft, may be adopted. Further, it goes without saying that the present invention is applicable not only to a vehicle equipped with a rack and pinion type steering mechanism, but also to a vehicle equipped with another type of steering mechanism such as a ball screw type.

[0036]

As described in detail above, in the power steering apparatus according to the present invention, the planetary type speed reducer disposed in the middle of the transmission system for transmitting the output of the steering assisting motor to the steering mechanism is It is equipped with an outer ring that is driven to rotate around the center, and the reduction ratio of the speed reducer can be continuously increased or decreased by the rotation of this outer ring. In addition, by realizing a small reduction ratio, the deterioration of the steering feeling due to the influence of the inertia of the motor is alleviated, and the motor for steering assist is always driven in the high efficiency range, so that the overall efficiency can be improved. . Moreover, these things
The present invention has excellent effects such as realization with a simple configuration in which a motor for driving an outer ring is added.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of a power steering apparatus according to the present invention.

FIG. 2 is an enlarged sectional view of a characteristic portion of the power steering apparatus according to the present invention.

FIG. 3 is a front view of a planetary roller reducer.

[Explanation of symbols]

 1 Upper shaft 2 Lower shaft 3 Torsion bar 5 Rack shaft 6 Torque sensor 7 Transmission shaft 8 Auxiliary motor 9 Speed change motor 10 Pinion 11 Intermediate transmission shaft 12 Electromagnetic clutch 13 Planetary roller reducer 31 Sun roller 32 Planetary roller 33 Outer roller 33a External teeth 39a Thrust needle bearing 39b Thrust needle bearing 40a Reduction gear housing 40b Clutch housing 40c Pinion housing

Claims (1)

[Claims] 1. A power steering apparatus comprising a planetary speed reducer for increasing the output of the motor in the middle of a transmission system for transmitting the output of a motor for steering assistance to a steering mechanism. A power steering apparatus comprising drive means for rotationally driving a ring around an axis of the speed reducer.