JPH0323418Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electric power steering device of a type in which steering force is assisted by an electric motor.

The power steering devices currently in practical use are generally hydraulic power steering devices that use oil pressure.A hydraulic power steering device is a hydraulic power steering device that uses a precisely machined hydraulic pump that is constantly driven while the engine is running. hydraulic control valve,
Equipped with various hydraulic piping, etc. For this reason, the structure of the hydraulic power steering system has become extremely complex, requiring high mechanical precision, and the loss of power caused by constantly driving the hydraulic pump while the engine is running, as well as wear and tear on each seal. In addition, there is a risk of oil leakage from each seal portion.

In recent years, in order to solve these problems with hydraulic power steering devices, the practical use of electric power steering devices that do not require hydraulic pumps, hydraulic control valves, various hydraulic piping, etc. has been promoted, and various types of electric power steering devices have been developed. A type power steering device has been proposed. One type of this includes a first shaft and a second shaft coaxially connected via a torsion bar and rotatably supported in a housing;
A gear that is rotatably assembled to the first shaft or the second shaft and driven by an electric motor, and a gear that is interposed between the gear and the first shaft or the second shaft and that is capable of relative rotational displacement between these two shafts. a clutch mechanism that connects the gear and the first shaft or the second shaft when the rotational displacement reaches a predetermined value; An electric power steering device that is activated and uses its driving force to assist the steering force has been proposed in Japanese Patent Laid-Open No. 126030/1983.

Such an electric power steering device automatically connects the gear and the first shaft or the second shaft (driving shaft or driven shaft) by a clutch mechanism when the relative rotational displacement between the two shafts reaches a predetermined value, In other words, the clutch mechanism automatically releases the connection between the gear and the drive shaft or driven shaft when the torsional moment of the torsion bar falls below a predetermined value.
Unlike the case where the electric motor and both shafts are directly connected, this type has the advantage that the inertia of the electric motor and gears does not adversely affect the return of the steering wheel.

In such an electric power steering device, the clutch mechanism has a cup-shaped driving body fixed to the drive shaft, and a notch formed in the side wall of the driving body, which is integrally provided with a casing fixed to the driven shaft. The cam is inserted between the driving body, the outer periphery of the cam, and the perforated part of the gear assembled surrounding it, and expands and contracts by the torsional action of the torsion bar, and the gear and driven shaft It is composed of a winding spring that engages and disengages the. For this reason, in such an electric power steering device, the rotation of the electric motor is transmitted to the driven member after the winding spring is expanded, and the steering force is assisted. is not good. In addition, in such an electric power steering device, since the wrapping spring is always in contact with the inner wall of the perforation, the steering operation on the steering shaft when not assisted is heavy.
Furthermore, it is prone to wear and has poor durability.

In order to deal with this, the present inventor proposed a clutch mechanism that includes a cam surface provided in the circumferential direction on the outer periphery of the first shaft or the second shaft, and a cam surface that is interposed between the cam surface and the gear. a cam follower that connects the gear to the first shaft or the second shaft when the gear is moved relative to the first shaft by a predetermined amount in the circumferential direction; An electric power steering device has been devised that includes a holding member that relatively moves the cam follower in the circumferential direction when a relative rotational displacement occurs. In such a power steering device, when a predetermined relative rotational displacement occurs between the two shafts, the holding member of the cam follower relatively moves the cam follower by a predetermined amount in the circumferential direction to immediately connect one of the shafts to the gear. . Therefore, the steering force is assisted with good responsiveness. In addition, when the gear and shaft are not coupled, that is, when the steering force is not assisted, the friction between the cam surface, cam follower, and gear is small, so the steering operation is not heavy when the steering force is not assisted, and there is little decrease in durability due to wear. .

By the way, in such a power steering device, when the holding member of the cam follower is directly connected to the other of the two shafts, the torsional torque of the shaft is directly transmitted to the holding member. If it is too large, the impact will be large when it is connected to one gear, and problems will arise in the strength of the holding member to withstand the impact load.Also, after one shaft and gear are connected, it will be difficult to determine the relative rotational displacement between the two shafts. Therefore, it is impossible to finely control the assistance of steering force.

The present invention has been developed by paying attention to such a situation, and its main purpose is to connect the holding member of the cam follower and the other shaft via a connecting mechanism that elastically allows a predetermined relative rotation. , the purpose is to solve each of the above-mentioned problems.

In order to achieve such an object, the present invention provides the above-mentioned power steering device, which includes a connecting member that connects the holding member to the second shaft or the first shaft while allowing a predetermined relative rotation, and a connecting member of the holding member. Its structural feature lies in that it is connected to the second shaft or the first shaft via a connecting mechanism provided with a spring member that elastically allows relative rotation.

Therefore, in the present invention, the relative rotation between the holding member and the second shaft or the first shaft is elastically allowed by the action of the connection mechanism, so that the first shaft or the first shaft is The impact when the second shaft and the gear are connected is alleviated, and the impact load applied to the holding member is alleviated, thereby solving problems in strength. In addition, elastic relative rotation between the holding member and the second shaft or the first shaft is allowed even after the first shaft or the second shaft is connected to the gear. It is also possible to determine the relative rotational displacement between the two shafts, thereby making it possible to finely control the assistance to the steering force in accordance with the steering torque.

Hereinafter, the present invention will be explained based on the drawings. FIG. 1 shows an embodiment of an electric power steering device according to the present invention. The steering shaft 10 of this electric power steering device includes an upper shaft 11 to which a steering wheel is attached at the upper end, a lower shaft 12 to which the lower end is connected to, for example, a pinion shaft of a steering gear, and both shafts 11 and 12 coaxially connected to each other. It is constructed by connecting torsion bars 13. Lower shaft 12 is Atsupashi shaft 1
The atsupashi shaft 1 is rotatably inserted into the cylindrical portion 11a of the atsupashi shaft 11 from the lower end opening thereof, and is rotated by the torsion bar 13 within the cylindrical portion 11a of the atsupasyaft 11.
1 and is rotatably supported within a housing 21 that is assembled into a part of the vehicle body. Furthermore, a steering torque detection mechanism 30 is assembled approximately at the center of the steering shaft 10. In this power steering device, a bracket 2 is attached to the upper part of the housing 21.
2, an electric motor 41 capable of forward and reverse rotation is attached, and a reduction gear train 50 and a clutch mechanism 60 are disposed within the lower end of the housing 21.

The steering torque detection mechanism 30 is connected to the lower shaft 12.
A cylindrical cam follower 31 that is slidably fitted to the outer periphery of the cylindrical portion 11a of the atsupashi shaft 11 located on the outer periphery of the upper end, and the cylindrical portion 11a of the atsupashi shaft 11.
It is composed of a cylindrical cam 32 that is fitted and fixed to the outer periphery, a compression spring 33 that urges the cam follower 31 toward the cam 32, and reed switches 34 and 35 that turn on and off the drive of the electric motor 41. The cam follower 31 is entirely magnetized in advance, and is inserted into a long hole provided in the circumferential direction in the cylindrical portion 11a of the upper shaft 11 and a long hole provided in the axial direction in the cam follower 31 to connect the lower shaft 12 and the torsion bar 13. The connecting pin 36 is attached to the upper shaft 11 so as to be rotatable and slidable in the axial direction, and to the lower shaft 12 so as to be non-rotatable and slidable in the axial direction. This cam follower 31 elastically engages with the inclined cam surface 32a of the cam 32 at its protrusion 31a, and when the shaft 11 is rotated clockwise, the torsion bar 13 is twisted and both shafts 1 are rotated clockwise.
When relative rotation occurs between 1 and 12, the shaft 11 slides toward the upper right in the figure, and the atsupashi shaft 11 is rotated to the left, causing the torsion bar 13 to twist, causing both shafts 11, 12 to rotate.
When relative rotation occurs between them, it slides toward the lower left in the figure. Both reed switches 34 and 35 are on bracket 2
3 at the approximate center of the housing 21, and is spaced from the annular flange 31b formed on the cam follower 31 at equal intervals. The reed switch 34 is a switch that is activated by the proximity of the flange 31b when the atspa shaft 11 is rotated clockwise, a predetermined steering torque is applied to the steering shaft 10, and the cam follower 31 slides a predetermined amount in the axial direction toward the upper right in the figure. During the operation, the electric motor 41 is driven to rotate in the normal direction. On the other hand, reed switch 3
5, the atsupashi shaft 11 is rotated to the left and the steering shaft 10 is rotated.
A predetermined steering torque is applied to the cam follower 31.
This is a switch that is activated by the proximity of the flange 31b when the flange 31b slides a predetermined amount in the axial direction toward the lower left in the drawing, and when activated, the electric motor 41 is driven in the reverse direction.

The electric motor 41 detects the steering torque detecting mechanism 30 when the steering torque applied to the steering shaft reaches a predetermined value.
Electrical signals generated from the reed switches 34, 3
5), and is connected to a small diameter gear 51 of a reduction gear train 50 via a shaft 42, a universal joint 43, etc. so as to be able to transmit power.
The large diameter gear 52 of the reduction gear train 50 is the small diameter gear 51
The clutch hub 61 is attached via a torsional damper mechanism 62 to a clutch hub 61 which is rotatably attached to the lower shaft 12.

Therefore, the clutch mechanism 60 in this embodiment
As shown in FIGS. 1 and 2, the power transmission between the lower shaft 12 and the large diameter gear 52 is carried out by the steering shaft 1.
It is intermittent depending on the steering torque applied to 0.
The clutch hub 61 and torsional damper 62 described above, a large number of cam surfaces 63a, 63b, . 64b..., and a cage 65 that is assembled to the outer periphery of the tip of the shaft 11 via a connecting mechanism 70 and holds the balls 64a, 64b.... In such a clutch mechanism 60, each ball 64a, 64
b... functions as a cam follower and cage 6
5 connects each ball 64a, 64b... to each cam surface 63
a, 63b... are moved relative to each other, and when there is no relative rotational displacement between the two shafts 11 and 12, they are in a neutral state as shown in FIG. In this state,
When a relative rotational displacement occurs between both shafts 11 and 12, each ball 64a and 6
4b... move relative to each other on the cam surfaces 63a, 63b... and the lower shaft 12 moves due to their wedge action.
and the clutch hub 61, and when the relative rotational displacement between both shafts 11, 12 reaches a predetermined value, each ball 64a, 64b... strengthens the engagement between the lower shaft 12 and the clutch hub 61. Combine both.

On the other hand, as shown in FIGS. 3 and 4, the coupling mechanism 70 includes an annular outward flange 71 provided at the upper end of the cage 65, a cylindrical body 72 having an annular outward flange 72a opposite thereto, and an outward flange 72a. 7
1, and includes a plurality of coil springs 74 and connecting pins 75. The outward flange 71 is provided with a plurality of window portions 71a extending linearly in the circumferential direction at equal intervals, and a plurality of elongated holes 71b extending in an arc shape in the circumferential direction are provided at equal intervals between the window portions 71a. provided at intervals. The cylindrical body 72 is fitted and fixed to the outer periphery of the shaft 11, and each window 71a of the outward flange 71 in the outward flange 72a
Each portion facing the window portion 71a is formed into a semi-cylindrical recess 72b that bulges out to the outside of each window portion 71a. Moreover, the outward flange 7 in the outward flange 72a
A through hole 72c is provided at each portion facing substantially the center of each elongated hole 71b. cover 73
covers the lower end side of the outward flange 71, and each recess 72 of the outward flange 72a of the cylindrical body 72
b and a plurality of recesses 73 similar to each through hole 72c.
a and a plurality of through holes 73b are provided.
The outward flange 71, the cylindrical body 72, and the cover 73 each have a window portion 71a of the outward flange 71.
A pair of front and rear spring retainers 76a, 76b
They are connected by respective connecting pins 75 with a coil spring 74 assembled therebetween. Each connecting pin 75 is connected to each through hole 72c of the cylindrical body 72, each elongated hole 71b of the outward flange 71, and the cover 73.
It passes through each through hole 73b, and one end thereof is caulked to prevent it from coming out. This results in
Outward flange 71, cylinder 72 and cover 73
are each of those window portions 71a and both recesses 72
The coil spring 74 and both spring retainers 76a and 76b are housed in b and 73a and are connected to each other, and the outward flange 71 and the cylindrical body 72
The cylinder body 72 and the cover 73 can be rotated relative to each other by a predetermined amount determined by the length of each elongated hole 71b of the outward flange 71.
The front wall or rear wall 72 of each recess 72b, 73a
d and 73c bend each coil spring 74. Therefore, the relative rotation of the outward flange 71, cylinder 72, and cover 73 is elastically allowed by a predetermined amount.

In the power steering device configured as described above, when the driver is in a neutral state in which no steering operation is performed, the clutch mechanism 60 releases the connection between the lower shaft 12 and the clutch hub 61 in the neutral state shown in FIG. and the electric motor 41 is stopped. In this state, when the driver rotates a steering wheel (not shown) to perform a steering operation, the torsion shaft 11 rotates and rotates the lower shaft 12 via the torsion bar 13; is twisted, and a relative rotational displacement occurs between both shafts 11 and 12. When this relative rotational displacement is small, that is, when the road resistance of the tires is small and the steering operation can be performed lightly, the electric motor 41 and the clutch mechanism 60 do not operate, so the steering force is not assisted, but the relative When the rotational displacement reaches a predetermined value, the electric motor 41 is activated by the action of the steering torque detection mechanism 30 and is activated by the clutch mechanism 60 via the reduction gear train 50.
Rotate the clutch hub 61 of. Further, in the clutch mechanism 60, the balls 64a, 64b, . Therefore, when the road surface resistance of the tires is large and the relative rotational displacement is large and a large steering force is required, the lower shaft 12 is rotated by the electric motor 41 in a direction in which the relative rotational displacement becomes smaller, thereby assisting the steering force. . Further, when the relative rotational displacement between the shafts 11 and 12 becomes less than a predetermined value, the connection between the lower shaft 12 and the clutch hub 61 is released and the electric motor 41 is stopped. Therefore, when the steering wheel returns after a steering operation, the inertial force of the electric motor 41 does not adversely affect the return of the steering wheel. Note that when the handle returns, the torsion bar 13 is hardly twisted, so both shafts 11, 1
The relative rotational displacement between the two is small, and the lower shaft 12 and the clutch hub 61 are almost never connected by starting the electric motor 41 or operating the clutch mechanism 60.

By the way, in the power steering device, the cage 65, which is one component of the clutch mechanism 60, is connected to the shaft 11 via the connection mechanism 70, and each coil spring 74, each connection pin 75,
The structure is such that relative rotation between the cage 65 and the shaft 11 is elastically allowed by a predetermined amount by the action of each elongated hole 71b and the like. For this reason, cage 6
5 and each ball 64a, 64b... lower shaft 12 and clutch hub 61 (large diameter gear 5
2) The impact load when they are connected is alleviated, and the connection between the two is made smooth, and the problem with the strength of the cage 65 against the impact load is resolved. Further, since the relative rotation between the atsupashi shaft 11 and the cage 65 is allowed even after the lower shaft 12 and the clutch hub 61 (large diameter gear 52) are connected, the relative rotation between the atsupashit 11 and the lower shaft 12 is allowed even after these two are connected. Rotational displacement can be determined. Therefore, by detecting such relative rotational displacement and controlling the drive of the electric motor 41 accordingly, it becomes possible to finely control the assistance to the steering force in accordance with the steering torque.

Note that in this embodiment, the lower shaft 12
An example has been shown in which a cam surface is formed on the outer circumference of the shaft 11 and a ball serving as a cam follower is interposed between this cam surface and the clutch hub 61. A change can be made to interpose a cam follower between the clutch hub and the clutch hub. In addition, in the present invention, both shafts 11,
A clutch mechanism may be interposed between the shaft 11 or 12 and the large diameter gear 52 by directly rotatably supporting the large diameter gear 52 on the outer periphery of one of the shafts 12. In addition, in the present invention, each ball 64 is used as a cam follower constituting the clutch mechanism.
a, 64b... can be replaced with a cam follower of an appropriate shape that has a wedge effect equivalent to these, and both shafts 11, 12 such as arms can be used instead of the cage 65 as a holding member for the cam follower.
A holding member of an appropriate shape that is connected to any one of the cam followers and holds the cam follower may be employed, and furthermore, an elastic body such as rubber may be used as the spring member in the coupling mechanism 70 instead of the coil spring 74. . In addition, reed switches 34 and 35
It goes without saying that any conventionally known appropriate steering torque detection mechanism may be used instead of the steering torque detection mechanism 30 having the following.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the power steering device according to the present invention, Fig. 2 is an enlarged partial vertical sectional view showing the main parts of the clutch mechanism of the device, and Fig. 3 is a schematic diagram of the device. FIG. 4 is a partially cutaway enlarged front view showing the coupling mechanism, and FIG. 4 is a sectional view taken along the line - in FIG. 3. Explanation of symbols, 10... Steering shaft, 11... Upper shaft, 12... Lower shaft, 13... Torsion bar, 30... Steering torque detection mechanism, 41
...Electric motor, 50...Reduction gear train, 60...
Clutch mechanism, 61...Clutch hub, 63a,
63b...cam surface, 64a, 64b...ball,
65... Cage, 70... Connection mechanism, 71... Outward flange, 71b... Elongated hole, 72... Cylindrical body, 7
3...Cover, 74...Coil spring, 75
...Connection pin.

Claims (1)

[Scope of utility model registration request] A first shaft and a second shaft are coaxially connected via a torsion bar and rotatably supported by a housing.
a shaft, a gear rotatably assembled on the first shaft or the second shaft and driven by an electric motor, and a gear interposed between the gear and the first shaft or the second shaft and between the two shafts. a clutch mechanism that connects the gear and the first shaft or the second shaft when the relative rotational displacement between the two shafts reaches a predetermined value; In the electric power steering device in which the electric motor is started and its driving force assists the steering force, the clutch mechanism is a cam provided circumferentially on the outer periphery of the first shaft or the second shaft. a cam follower that is interposed between the cam surface and the gear and connects the gear and the first shaft or the second shaft when the cam follower moves relative to the cam surface by a predetermined amount in the circumferential direction; while holding the second shaft or the first shaft.
a holding member that is connected to a shaft and moves the cam follower relative to the circumferential direction when a relative rotational displacement occurs between these two shafts, and the holding member is arranged at a predetermined position with respect to the second shaft or the first shaft. It is characterized in that it is connected to the second shaft or the first shaft through a connecting mechanism that includes a connecting member that allows relative rotation and is connected, and a spring member that elastically allows relative rotation of the holding member. Electric power steering device.