JP3269911B2 - Electric power steering device - Google Patents

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 system, and more particularly to an electric power steering system in which the rate of change of the amount of displacement between an input shaft and an output shaft is changed in a plurality of stages to smooth the connection of a clutch mechanism. .

[0002]

2. Description of the Related Art An electric power steering apparatus controls an assist amount of a motor based on a torque at which a driver operates a steering wheel. The operating torque of the steering wheel is such that when the input shaft, which is the shaft on the steering wheel side, and the steering gear, that is, the output shaft, which is the shaft on the tire side, are connected by an elastic body such as a torsion bar, and the steering wheel is operated, It is measured from the amount of displacement generated between the input shaft and the output shaft.

As the electric power steering apparatus, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 1-1199026. The clutch device disclosed in this publication is configured such that a cylindrical surface is formed on one of an inner diameter surface of a clutch outer ring and an outer surface of a clutch inner ring incorporated inside the outer ring, and an inclined cam surface is provided on the other. A pocket is provided at a position corresponding to the wedge-shaped space formed by the cylindrical surface and the inclined cam surface in the cylindrical retainer interposed therebetween. Two rolling elements are provided in the pocket and the rolling elements are in opposite directions. A spring that presses against the wall surface facing in the circumferential direction of the pocket and presses against the cage, and engages the retainer with the clutch outer ring and the clutch inner ring on the member having the inclined cam surface with the rotational gap, A torque setting member that is elastically deformed until the rotational direction gap is eliminated when the rotational direction gap is adjusted to the neutral position and the rotational direction gap is eliminated when the set torque is exceeded is provided between both members, In the neutral position, the rolling elements accommodated in the pockets of the cage are not engaged with any of the narrow portions at both ends of the wedge-shaped space, and when the clutch is used for electric power steering, the torque setting elastic member When the steering operation force is equal to or less than the set torque, manual operation is performed, and when the torque exceeds the set torque, the operation mode is automatically switched to power steering.

[0004] There is also one disclosed in Japanese Patent Application Laid-Open No. 1-218973. In the electric power steering apparatus disclosed in this publication, a steering torque detector detects a steering torque in accordance with an elastic deformation of an elastic body connecting an input shaft and an output shaft, and a clutch outputs the output shaft by the elastic deformation of the elastic body. And the on / off control of the electric motor, the on / off control of the clutch is controlled, the elastic deformation of the elastic body, the elastic body when the steering torque detector detects the steering torque and starts the rotation of the electric motor , Which makes the electric power steering more compact and improves the steering feeling.

[0005]

By the way, in the conventional electric power steering apparatus, the clutch mechanism 138 is used.
As shown in FIG. 12, the worm wheel 150
An outer retainer 170 disposed concentrically within the worm wheel 150; an inner retainer 172 disposed concentrically within the outer retainer 170; and disposed between the worm wheel 150 and the output shaft 116. And a connecting pin 176 for connecting the input shaft 112 to the outer retainer 170, and a spring 178 for pressing the rolling element 174 toward the connecting pin 176.

The length of the rolling element 174 is determined by the output shaft 116.
When the steering wheel (not shown) is not operated, the rolling elements 174 between the worm wheel 150 and the output shaft 116 do not transmit torque, that is, when the steering wheel (not shown) is not operated. It is time (see FIG. 12).

Further, the steering wheel is operated,
When the input shaft 112 moves in the direction of arrow A, the outer retainer 170 rotates in the same direction (arrow A1) as the input shaft 112 via the connecting pin 176, as shown in FIG.

The rolling element 174 is pressed by the urging force of a spring 178 fixed to the outer retainer 170, and is inclined from the dashed line in FIG. 13 to the solid line.

At this time, if the amount of displacement between the input shaft 112 and the output shaft 116 exceeds a certain value, the rolling element 174 meshes between the worm wheel 150 and the output shaft 116, and when the clutch is engaged, an arrow B appears. As shown, the rotation of the worm wheel 150 is transmitted to the output shaft 116.

On the other hand, there is a case where an abnormality occurs in a drive system of an electric motor such as a motor (not shown), and the worm wheel 150 is locked and becomes inoperable. In this case, the connecting pin 176 is inserted into the pocket hole of the output shaft 116. The input shaft 112 contacts the side surface (not shown) and directly transmits the rotation to the output shaft 116. This rotation acts to release the rolling element 174 from the connection between the output shaft 116 and the worm wheel 150. Since such an action occurs, manual steering can be performed even when the drive system is locked.

As shown in FIG. 14 (b), when assist is performed by the motor as the electric motor in the entire range of the operating torque which is the steering wheel operation amount, when the clutch mechanism is turned on, the operation shown in FIG. As shown by the one-dot chain line (conventional 1) in a), the motor driving force is transmitted to the output shaft through the clutch mechanism, and assist is suddenly started, resulting in an inconvenience in operation.

When a three-way mechanical clutch mechanism is used, as shown in FIG. 15, when a steering wheel operating torque exceeding a certain value is applied, as shown in FIG.
After the clutch mechanism was connected, the steering wheel operation area became narrower, causing a sense of incongruity.

That is, the displacement between the input shaft and the output shaft is
As shown by the one-dot chain line (conventional 2) in FIG. 15B, the same change amount in the entire region up to the limit torque of the elastic body, which is the limit displacement amount of the elastic body, with respect to the operating torque of the steering wheel. is there.

When detecting a steering torque with a single elastic body, for example, when a hard elastic body and a soft elastic body are used, respectively, in the case of a hard elastic body, one is shown in FIG.
As indicated by the dashed line (conventional 2), a large torque can be linearly detected, but the steering torque required to connect the clutch mechanism becomes large, and the assistless region becomes large across the neutral point, resulting in a reduced steering feeling. There is an inconvenience.

In the case of a soft elastic body, FIG.
As shown by the two-dot chain line (conventional 3) in (a), the clutch mechanism can be connected with a small standby torque, but a large torque cannot be detected due to the elastic limit of the elastic body, and the linear torque range is small. In addition, the control current of the motor rises steeply, and the stability of the control system is impaired.

[0016] The standby torque refers to an electric power steering for connecting a clutch mechanism.
It refers to the steering torque when the amount of displacement between the input shaft and the output shaft is a predetermined value.

Therefore, if a single elastic body is used for detecting the steering torque, the dynamic range of the assist cannot be widened, which is disadvantageous in practical use.

[0018]

SUMMARY OF THE INVENTION Accordingly, in order to eliminate the above-mentioned disadvantages, the present invention provides an input shaft connected to a steering wheel of a vehicle and an output shaft connected to a steering gear via an elastic body. When the amount of displacement of the elastic body due to relative rotation between the input shaft and the output shaft is equal to or less than a set value, the elastic member is separated from the output shaft and the input shaft and the output shaft are separated from each other. A clutch mechanism that is engaged with the output shaft when a displacement amount of the elastic body due to the relative rotation exceeds a set value; a motor that interrupts transmission of torque to the output shaft by the clutch mechanism; When the amount of displacement of the elastic body due to relative rotation between the shaft and the output shaft exceeds a set value, the driving force of the electric motor is transmitted to the output shaft via the clutch mechanism to assist the steering wheel operating force. In the electric power steering device, when the displacement amount of the elastic body due to the relative rotation between the input shaft and the output shaft is equal to or less than a set value, the displacement amount is generated only by the elastic body, and the input shaft and the output shaft are When the amount of displacement of the elastic body due to relative rotation with the elastic member exceeds a set value, the rate of change of the amount of displacement is changed in a plurality of steps in order to reduce the rate of change of the amount of displacement in cooperation with the elastic body. A rate-of-change switching means for increasing the assist area of the electric motor after the clutch mechanism is connected is provided in the transmission path of the torque between the input shaft and the output shaft.

[0019]

According to the invention described above, when the steering wheel is operated, the operation of switching between the generation of the displacement by the elastic body alone and the generation of the displacement by the elastic body and the change rate switching means is performed. The assist area of the electric motor after the clutch mechanism is connected by changing the ratio in a plurality of stages is increased.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 10 show a first embodiment of the present invention. In FIG. 2, 2 is a power steering device, 4 is a vehicle, and 6 is a steering wheel.

In the power steering apparatus 2, a steering wheel 6 and a steering gear 8 are provided in communication with each other via a steering column 10, and the steering column 10 is connected to an input shaft 12 which is a shaft on the steering wheel 6 side and a steering gear 8 In other words, it comprises an output shaft 16 which is a shaft on the tire 14 side, and an elastic body 18 such as a torsion bar connecting the input shaft 12 and the output shaft 16.

When the amount of displacement of the elastic body 18 due to the relative rotation between the input shaft 12 and the output shaft 16 exceeds a set value, the driving force of the motor 24 described later is output via the clutch mechanism 38 described later. 16 to assist the operating force of the steering wheel 6 by transmitting it to the steering wheel 6.

A steering sensor 20, which is a torque sensor, a speed reduction mechanism 22, and a motor 24, which is an electric motor, are mounted on the steering column 10.

The motor 24 is connected to a control means 26. The control means 26 has a vehicle speed sensor 28 such as a speedometer, a steering sensor 20, and a generator 30 as shown in FIGS. , An engine speed sensor 32, and a battery 36 via an ignition switch 34, respectively.

Then, the motor 24 is driven by the control means 26 based on signals from the vehicle speed sensor 28 and the steering sensor 20, as shown in FIG. At this time, the rotation of the motor 24 is transmitted to the steering column 10 through a three-way clutch mechanism 38 to assist the steering operation.

As shown in FIG. 4, the steering column 10 is surrounded by an upper housing 40 and a lower housing 42. In the upper housing 40, the cylindrical input shaft 12 is supported and provided. The output shaft 16 is supported and provided via a bearing 44 therein, and the end of the input shaft 12 is slidably fitted into the output shaft 16. The elastic body 18 is located inside the input shaft 12, one end of the elastic body 18 is fixed to the input shaft 12, and the other end is fixed to the output shaft 16.

Therefore, when the steering wheel 6 is operated, the elastic body 18 is slightly twisted, and the input shaft 12 and the output shaft 16 are displaced. If this displacement exceeds a certain value set by the elastic characteristic of the elastic body 18, mechanically
The way type clutch mechanism 38 is connected, and the driving force of the motor 24 is transmitted to the output shaft 16. That is, the clutch mechanism 38 includes the input shaft 12 and the output shaft 1.
When the amount of displacement of the elastic body 18 due to relative rotation with respect to 6 is equal to or less than a set value, the elastic body 18 is separated from the output shaft 16 and
When the displacement of the elastic body 18 due to the relative rotation between the input shaft 12 and the output shaft 16 exceeds a set value, the elastic body 18 is engaged with the output shaft 16.

As shown in FIG. 5, the motor 24 is provided with the reduction mechanism 22 on a shaft 46 of the motor 24. The reduction mechanism 22 is provided with a worm gear 48 mounted on the shaft 46 of the motor 24. And a worm wheel 5 of a three-way clutch mechanism 38 disposed around the steering column 10 so as to mesh with the worm gear 48.
0, the driving force of the motor 24 is reduced and transmitted to the worm wheel 50 of the clutch mechanism 38.

As shown in FIG. 10, the steering sensor 20 includes a sensor body 52 and a sensor body 5.
Shaft 54 protruding from the side 2 toward the input shaft 12 and the output shaft 16
And a plate member 56 that rotates around the shaft portion 54, and a sensing portion 60 that protrudes from the plate member 56 and contacts a first slider 58 on the outer periphery of the input shaft 12.

As shown in FIG. 4, the first slider 58 and the second slider 58
The slider 62 is fixed with a C-shaped ring 64, and the second
A ball 66 is provided in contact with the slider 62, and a groove 68 for moving the ball 66 is formed on the input shaft 12. As shown in FIGS. 7 to 9, the groove 68 has a predetermined angle with respect to the longitudinal direction of the input shaft 12 like a screw thread shape of a screw.

At this time, when the steering wheel 6 is operated and the input shaft 12 and the output shaft 16 are twisted,
The ball 66 moves along the groove 68, and the ball 66
The first and second sliders 58 and 62 slide in the axial direction of the input shaft 12 in accordance with the movement of. And
When the first and second sliders 58 and 62 slide in the axial direction of the input shaft 12, the sensing unit 60 also moves, and the shaft 54 rotates via the plate member 56. The steering sensor 20 detects the rotation amount of the shaft portion 54,
The detection signal is transmitted to the control means 26.

As shown in FIGS. 1 and 6, the clutch mechanism 38 includes a worm wheel 50 and an outer retainer 70 disposed concentrically within the worm wheel 50.
An inner retainer 72 disposed concentrically within the outer retainer 70; a rolling element 74 which is a sprag disposed between the worm wheel 50 and the output shaft 16;
And a spring 78 for pressing the rolling element 74 toward the connecting pin 76.

The length of the rolling element 74 is set to be slightly smaller than the distance between the output shaft 16 and the worm wheel 50, and the length between the worm wheel 50 and the output shaft 16 when the steering wheel 6 is not operated. The rolling elements 74 do not transmit the rotational force, that is, when the clutch is released (see FIG. 1).

When the displacement of the elastic body 18 due to the relative rotation between the input shaft 12 and the output shaft 16 is equal to or smaller than a set value, the displacement is generated only by the elastic body 18 and the input shaft 12 When the amount of displacement of the elastic body 18 due to the relative rotation of the elastic body 18 and the output shaft 16 exceeds a set value, the change in the amount of displacement is reduced in cooperation with the elastic body 18 to reduce the rate of change of the amount of displacement. The change rate switching means 80 for increasing the assist area of the motor 24 after changing the rate in a plurality of steps and connecting the clutch mechanism 38 to the input shaft 12 and the output shaft 1
6 in the middle of the transmission path of the rotational force.

More specifically, the change rate switching means 80 is a multi-stage displacement amount switching system that switches the change rate of the displacement amount generated between the input shaft 12 and the output shaft 16 in multiple stages.
In this embodiment, the change rate switching means 80 is provided between the connecting pins 76 of the inner holding portion 72 and the outer holding portion 70 of the clutch mechanism 38.

That is, as shown in FIG. 1, the rate-of-change switching means 80 comprises first and second coil-type springs 82-1 and 82-2 disposed on both sides of the connecting pin 76. The first and second springs 82-1 and 82-2 are fixed on the 72 side, and a small gap S1 and S2 is provided between the first and second springs 82-1 and 82-2 and the connecting pin 76. Arrange.

When the steering wheel 6 is operated, the displacement of the elastic body 18 due to the relative rotation between the input shaft 12 and the output shaft 16 is set until one of the gaps S1 and S2 becomes 0 (zero). If less than the value,
The displacement is generated only by the elastic body 18 and the gap S
After either one of S1 and S2 becomes 0 (zero), that is, when the displacement of the elastic body 18 due to the relative rotation between the input shaft 12 and the output shaft 16 exceeds a set value, the elastic body 18
And one of the first and second springs 82-1 and 82-2 generates a displacement with a small change rate, and changes the change rate of the displacement in two stages, for example.

Next, the operation will be described.

When the steering wheel 6 is operated to rotate the input shaft 12 in the direction of arrow A in FIG. 6, the outer retainer 70 rotates in the same direction as the input shaft 12 via the connecting pin 76 (arrow A1). .

The rolling element 74 is mounted on the outer cage 7.
It is pressed by the urging force of the spring 78 fixed to 0, and tilts from the one-dot chain line state to the solid line state in FIG.

At this time, when the displacement between the input shaft 12 and the output shaft 16 exceeds a certain value, the rolling element 74 meshes between the worm wheel 50 and the output shaft 16 and the clutch mechanism is connected to indicate the arrow. As shown in B, the rotation of the worm wheel 50 is transmitted to the output shaft 16.

At the start of the connection of the clutch mechanism 38 in the case where the motor 24 is driven in all regions, FIG.
As shown by the solid line in (a), a half-clutch state occurs in which the clutch mechanism 38 starts slipping, and the driving force from the motor 24 is smoothly transmitted to the output shaft 16.

Here, the displacement between the input shaft 12 and the output shaft 16 will be described in detail. When the steering wheel 6 is operated, the distance between the first and second springs 82-1 and 82-2 and the connecting pin 76 is reduced. For example, until the gap S2 becomes 0 (zero),
That is, until the connection pin 76 rotates and comes into contact with the second spring 82-2, the displacement amount is generated only by the elastic body 18.

Further, the connecting pin 76 is rotated to rotate the second spring 8.
After the contact with 2-2 and the gap S2 becomes 0 (zero),
A displacement with a small change rate is generated by the elastic body 18 and the second spring 82-2, and the change rate of the displacement is changed, for example, in two stages (see a solid line in FIG. 15B).

Further, for reference, the ball 66 in the operation of the steering wheel 6 and the groove 68 with which the ball 66 is engaged will be described.

When the steering wheel 6 is not operated,
That is, in the neutral position of the steering wheel, as shown in FIG.
The ball 66 is located at the center of the groove 68.

When the steering wheel 6 is operated to rotate the steering wheel to the left, as shown in FIG. 8, an operation torque is generated by the operation of the steering wheel 6, the elastic body 18 is twisted, and the input shaft 12 and the output shaft 16 are twisted. And the ball 66 moves upward in the groove 68, and the first slider 58 and the second slider 62
Slides upward to rotate the plate member 56 of the steering sensor 20 that contacts the first slider 58 upward.

Conversely, when the steering wheel 6 is operated and the steering wheel is turned rightward, as shown in FIG. 9, an operation torque is generated by the operation of the steering wheel 6, the elastic body 18 is twisted, and the input shaft 12 and the output shaft are output. A relative displacement occurs with the shaft 16, and the ball 66 moves downward in the groove 68, and the first slider 58 and the second slider 62
Slides downward, and rotates the plate member 56 of the steering sensor 20 that contacts the first slider 58 downward.

Thus, when the motor 24 is driven in the entire region, as shown by the solid line in FIG.
The first and second springs 82-1 and 82-2, which are 0, can be in a half-clutch state in which the clutch mechanism 38 starts to slide, and the driving force from the motor 24 can be smoothly transmitted to the output shaft 16.

Further, by forming small gaps S1 and S2 between the first and second springs 82-1 and 82-2, which are the change rate switching means 80, and the connecting pin 76, the steering wheel 6 is connected. The pin 76 rotates and the second spring 8
Until contact with 2-2, the displacement amount is generated only by the elastic body 18 and the connecting pin 76 rotates to rotate the second spring 8.
After the contact with 2-2 and the gap S2 becomes 0 (zero),
A displacement with a small change rate is generated by the elastic body 18 and the second spring 82-2, and as shown by a solid line in FIG.
By changing the change rate of the displacement amount in, for example, two stages, the range of the displacement amount can be widened. For this reason, the clutch mechanism 3
After the connection of the motor 8, the assist area of the motor 24 can be enlarged, so that the so-called dynamic range can be widened, and there is no sense of incongruity in steering operation, which is practically advantageous.

Further, first and second springs 82-1 and 82-2, which are change rate switching means 80, are provided between the inner holding portion 72 of the clutch mechanism 38 and the connecting pin 76 of the outer holding portion 70. Accordingly, the mounting can be performed by utilizing the gap between the connection pins 76 of the inner holding portion 72 and the outer holding portion 70, so that the design change of each portion is not required and the clutch mechanism 38
It can be dealt with only by mounting inside, there is no need to change other than the clutch mechanism 38, there is no fear that the configuration is complicated, the cost can be kept low, and it is economically advantageous.

FIGS. 11A and 11B show the second embodiment of the present invention.
It shows an embodiment. In the second embodiment, portions that perform the same functions as those in the first embodiment will be described with the same reference numerals.

In the above-described first embodiment, the change rate switching means 80 is provided between the connecting pin 76 of the inner holding portion 72 and the outer holding portion 70 of the clutch mechanism 38. The features of the second embodiment are as follows. The point is that the change rate switching means 92 is provided in the stopper portion 90 that regulates the rotation state of the input shaft 12.

That is, as shown in FIG. 11A, the output shaft 16 is provided with stopper portions 90-1 and 90-2 having a fan-shaped cross section.
Are formed facing each other.

The stopper section 9 having a fan-shaped cross section is used.
The end of the input shaft 12 is slidably fitted in the key portions of 0-1 and 90-2, and the elastic body 18 is positioned inside the input shaft 12.

At this time, the input shaft 12 and the stopper 90-
Four coil type first to fourth springs 94-1, 94-2, 94-3, 94 which are change rate switching means 92 on the stopper portions 90-1, 90-2 between the first and the 90-2. -4. These first to fourth springs 94-1, 94-2, 94-
3, 94-4 are disposed at positions where odd numbers and even numbers face each other. Reference numerals 96-1 and 96-
2 is a ball.

Then, the input shaft 12 is rotated by the operation of the steering wheel, and as shown in FIG.
The input shaft 12 comes into contact with the first and third springs 94-1 and 94-3, so that the rate of change of the displacement can be changed in two stages as in the first embodiment. Then, when driving the motor in all regions, FIG.
As shown by a solid line, when the connection of the clutch mechanism is started, first to fourth springs 94 as the change rate switching means 92 are provided.
-1, 94-2, 94-3, and 94-4 can be brought into a half-clutch state in which the clutch mechanism starts to slide, and the driving force from the motor can be smoothly transmitted to the output shaft.

Further, a small gap is formed between the first to fourth springs 94-1, 94-2, 94-3, 94-4, which are the change rate switching means 92, and the stopper portions 90-1, 90-2. By operating the steering wheel, the input shaft 1
Until the second spring rotates and comes into contact with the first and third springs 94-1 and 94-3, the displacement amount is generated only by the elastic body 18 and the input shaft 12 rotates to rotate the first and third springs 94-1 and 94-3. -1,
After contacting the gap 94 to zero (0), a displacement is generated by the elastic body 18 and the first and third springs 94-1 and 94-3, and the displacement shown in FIG. As shown by the solid line,
By changing the change rate of the displacement amount in two stages, the change rate of the displacement amount can be made small and the range of the displacement amount can be widened. Therefore, similar to the first embodiment, the clutch mechanism 38
Can be widened after the connection, which is practically advantageous.

Further, first to fourth springs 94-1, 94-2, 94-3, and 94-4, which are change rate switching means 92, are provided in a stopper portion 90 for regulating the rotation state of the input shaft 12. As a result, the mounting can be performed by using the gap between the stopper portion 90 of the input shaft 12 and the output shaft 16, so that the design of each part does not need to be changed, and the first to fourth springs can be externally provided from the output shaft 16. 94-1, 94-2, 94-3, 94-4
Can be mounted, the mounting operation becomes easy, and there is no fear that the configuration becomes complicated, the cost can be maintained at low cost, and it is economically advantageous.

The present invention is not limited to the above-described first and second embodiments, and various modifications can be made.

For example, in the second embodiment of the present invention, four first to fourth springs as change rate switching means are provided on the stopper side between the input shaft and the stopper. It is also possible to arrange and use only odd-numbered springs or even-numbered springs.

[0063]

As described above in detail, according to the present invention, the input shaft connected to the steering wheel of the vehicle and the output shaft connected to the steering gear are rotatably supported via an elastic body. When the displacement of the elastic body due to the relative rotation between the input shaft and the output shaft is less than the set value, the elastic body is separated from the output shaft and the displacement of the elastic body due to the relative rotation between the input shaft and the output shaft. Is provided with a clutch mechanism that is engaged with the output shaft when the set value exceeds a set value, and an electric motor that interrupts transmission of torque to the output shaft by the clutch mechanism is provided, and elasticity due to relative rotation between the input shaft and the output shaft is provided. An electric power steering device that assists operating force of a steering wheel by transmitting a driving force of an electric motor to an output shaft via the clutch mechanism when an amount of displacement of a body exceeds a set value. When the displacement of the elastic body due to the relative rotation between the shaft and the output shaft is equal to or less than the set value, the displacement is generated only by the elastic body, and the displacement of the elastic body due to the relative rotation between the input shaft and the output shaft is reduced. If the set value is exceeded, the assist area of the electric motor after the clutch mechanism is connected by changing the rate of change of the displacement in multiple steps in order to reduce the rate of change of the amount of displacement in cooperation with the elastic body Is provided in the middle of the transmission path of the rotational force between the input shaft and the output shaft, so that when the motor is driven in all regions, when the connection of the clutch mechanism is started, the change rate switching means is increased. As a result, a half-clutch state in which the clutch mechanism starts to slide can be achieved, and the driving force from the electric motor can be smoothly transmitted to the output shaft. Also, by forming a small gap between the change rate switching means and the input shaft side, until the input shaft is rotated by operation of the steering wheel and contacts the change rate switching means,
That is, when the displacement of the elastic body due to the relative rotation between the input shaft and the output shaft is equal to or less than the set value, the displacement is generated only by the elastic body, and the input shaft rotates to contact the change rate switching means. After the gap becomes 0 (zero), that is, when the displacement amount of the elastic body due to the relative rotation between the input shaft and the output shaft exceeds a set value, the displacement amount of the elastic body is changed by the elastic body and the change rate switching means. By changing the rate of change in a plurality of stages, the rate of change of the amount of displacement can be made small and the range of the amount of displacement can be widened. For this reason, the assist area of the electric motor after the clutch mechanism is connected can be enlarged, so that the so-called dynamic range can be widened, and there is no uncomfortable feeling in steering operation, which is practically advantageous.

Further, if the change rate switching means is arranged between the connecting pins of the inner holding portion and the outer holding portion of the clutch mechanism, the gap between the connecting pins of the inner holding portion and the outer holding portion is used. It is not necessary to change the design of each part, and it can be dealt with only by installing it inside the clutch mechanism, no change other than the clutch mechanism is required, there is no risk of complicating the configuration, cost Can be maintained at a low cost, which is economically advantageous.

Further, if the change rate switching means is provided at the stopper for regulating the rotation state of the input shaft, it can be mounted by utilizing the gap between the stopper of the input shaft and the output shaft. This eliminates the need to change the design of each part and allows the change rate switching means to be mounted from outside the output shaft.
The mounting operation is easy, and the configuration is not likely to be complicated, and the cost can be kept low, which is economically advantageous.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a portion indicated by an arrow の in FIG. 5 when a three-way clutch according to a first embodiment of the present invention is released.

FIG. 2 is a schematic perspective view of a vehicle.

FIG. 3 is a circuit diagram of the electric power steering device.

FIG. 4 is an enlarged sectional view of a column portion.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is an enlarged view showing when a three-way clutch is connected.

FIG. 7 is a cutaway view of a main part of a ball and a groove at a steering wheel neutral position where the steering wheel is not operated.

FIG. 8 is a cutaway cross-sectional view of a main part of a ball and a groove when the steering wheel is operated to rotate the steering wheel to the left.

FIG. 9 is a cutaway view of a main part of a ball and a groove when the steering wheel is operated to rotate the steering wheel to the right.

FIG. 10 is a sectional view taken along line XX of FIG. 4;

FIG. 11 shows a second embodiment of the present invention;
(A) is a schematic diagram in the case where displacement amount switching means is provided in the stopper portion in the enlarged cross-sectional view taken along the line IV-IV in FIG.
(B), the input shaft is rotated by the operation of the steering wheel, and the input shaft is the first and third springs 9 which are change rate switching means.
It is the schematic of the state which contacted 4-1 and 94-3.

FIG. 12 is an enlarged view of the related art of the present invention when the three-way clutch is released.

FIG. 13 is an enlarged view showing when a three-way clutch is connected.

14A and 14B are diagrams showing a relationship between a steering wheel operation amount and motor assist, and FIG. 14A is a diagram showing a relationship between a steering wheel operation amount and a motor driving force transmitted to an output shaft through a clutch;
(B) is a diagram showing the relationship between the steering wheel operation amount and the driving force of the motor.

15A and 15B show the relationship between the handle operation amount and the change amount change, FIG. 15A shows the relationship between the handle operation amount and the motor assist amount, and FIG. 15B shows the relationship between the handle operation amount and the input shaft and the output shaft; It is a figure showing the relation with the amount of displacement.

[Explanation of symbols]

 2 Power steering device 4 Vehicle 6 Steering wheel 8 Steering gear 10 Steering column 12 Input shaft 16 Output shaft 18 Elastic body 20 Steering sensor 22 Reduction mechanism 24 Motor 26 Control means 28 Vehicle speed sensor 32 Engine speed sensor 34 Ignition switch 36 Battery 38 Clutch Mechanism 48 worm gear 50 worm wheel 66 ball 68 groove portion 70 outer retainer 72 inner retainer 74 rolling element 76 connecting pin 78 spring 80 change rate switching means 82-1 and 82-2 first and second springs

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroumi Nojiri 68, 1019, Akigashima, Iwata City, Shizuoka Prefecture (72) Inventor Koji Sato, 392 Naritaki, Kakegawa City, Shizuoka Prefecture 1 (56) References JP1 JP-A-229125 (JP, A) JP-A-6-8835 (JP, A) JP-A-1-249575 (JP, A) JP-A-4-321469 (JP, A) JP-A-3-239670 (JP, A) JP-A-5-139321 (JP, A) JP-A-5-139322 (JP, A) JP-A-3-11133 (JP, U) JP-A-2-13882 (JP, U) Field (Int.Cl. ⁷ , DB name) F16D 41/08

Claims (3)

(57) [Claims] An input shaft connected to a steering wheel of a vehicle and an output shaft connected to a steering gear are rotatably supported via an elastic body so as to be relatively rotatable. When the amount of displacement of the elastic body due to rotation is equal to or less than a set value, the elastic member is separated from the output shaft, and when the amount of displacement of the elastic body due to relative rotation between the input shaft and the output shaft exceeds the set value, the output shaft. A clutch mechanism is provided which is engaged with the motor, and an electric motor is provided which interrupts transmission of torque to the output shaft by the clutch mechanism. The displacement of the elastic body due to the relative rotation between the input shaft and the output shaft has a set value. An electric power steering apparatus which assists operating force of a steering wheel by transmitting a driving force of the electric motor to an output shaft via the clutch mechanism when the power is exceeded.
Set the amount of displacement of the elastic body due to relative rotation between the force axis and the output shaft
If the value is equal to or less than the value, the displacement is generated only by the elastic body.
And the relative rotation between the input shaft and the output shaft
If the amount of displacement of the elastic body exceeds the set value, the elastic body
In order to the cooperation with the small amount of displacement of the change rate and the change rate switching means for an assist region of motor after changing connected to the clutch mechanism in a plurality of stages the rate of change of the displacement and the large An electric power steering device provided in a transmission path of a rotational force between the input shaft and the output shaft . 2. The electric power steering according to claim 1, wherein the change rate switching means is a change rate switching means provided between connecting pins of an inner holding portion and an outer holding portion of the clutch mechanism. apparatus. 3. The electric power steering apparatus according to claim 1, wherein the change rate switching means is a change rate switching means provided on a stopper for regulating a rotation state of the input shaft.