JP2002127917A - Steering angle ratio variable steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering angle ratio variable steering device having a simple configuration and capable of setting a large variable amount of a steering angle ratio. SOLUTION: An input shaft 2 connected with a steering wheel 1 and an output shaft 10 continuous with the steering wheel are mutually connected through three cardan joints. An offset amount from a reference line H of the third cardan joint 5 is changed by a tilting device 20 to adjust a steering angle ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device mounted on a vehicle, and to a variable steering angle ratio steering device capable of changing a steering angle ratio.

[0002]

2. Description of the Related Art A conventional steering angle ratio variable steering apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-257406. In this device, the second shaft is connected to the input shaft connected to the steering wheel so as to be relatively movable on a plane passing through the axis of the input shaft in a state substantially parallel to the input shaft, and And a drive unit for relatively moving the input shaft and the second shaft on the plane. Further, an output shaft for transmitting rotation to the wheel is eccentrically connected to the second shaft. The driving means is a support member rotatably supported by the casing, and rotatably supports the input shaft or the second shaft at a position eccentric from the center of rotation of the support member, and further comprises: A drive source for rotating is provided.

[0003]

However, since the conventional steering angle ratio variable steering device is provided in the rack and pinion portion, when it is assumed that the steering device is employed in hydraulic power steering using hydraulic assist, the hydraulic pressure is reduced. Since the valve to be controlled is arranged in the rack and pinion portion, it is difficult to install the valve.

Further, since the amount of eccentricity is regulated by the layout conditions inside the gear, there is a problem that the variable amount of the steering angle ratio is limited. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide a variable steering angle ratio steering apparatus having a simple configuration and capable of setting a large variable amount of the steering angle ratio.

[0005]

In order to solve the above-mentioned problems, an invention according to claim 1 of the present invention provides an input shaft which is rotated by a steering input from a steering wheel, and an output which transmits rotation to a steered wheel. A variable steering angle ratio steering device, which is interposed between the input shaft and the output shaft to transmit rotation of the input shaft to the output shaft. The variable ratio mechanism connects the lower end of the input shaft and the upper end of the output shaft via a plurality of cardan joints, and sets the position of at least one of the plurality of cardan joints to the lower end of the input shaft. And a movable means for moving in a direction approaching / leaving from a straight line connecting the output shaft and the upper end of the output shaft.

Here, the steering angle ratio is defined by the following equation. Next, according to a second aspect of the present invention, in the configuration according to the first aspect, the variable steering angle ratio mechanism is configured such that one end is connected to a lower end of the input shaft via a first cardan joint. 1 link member, a second link member connecting one end to the upper end of the output shaft via a second cardan joint, and the other end of the first link member and the other end of the second link member. A third cardan joint to be connected, and movable means for moving the position of the third cardan joint in a direction approaching / separating from a straight line connecting the lower end of the input shaft and the upper end of the output shaft. It is a feature.

According to a third aspect of the present invention, in the configuration of the second aspect, the movable means can extend and contract at least one of the first link member and the second link member only in the axial direction. The first link member and the second link member.
A swinging means is provided for swinging at least one of the link members in a direction approaching or leaving a straight line connecting the lower end of the input shaft and the upper end of the output shaft.

Next, according to a fourth aspect of the present invention, the rotation transmitted from the input shaft to the variable steering angle ratio mechanism is reduced in comparison with the configuration according to any one of the first to third aspects. A reduction gear is provided. Next, the invention described in claim 5 is characterized in that a speed-increasing gear for increasing the speed of rotation transmitted from the variable steering angle ratio mechanism to the output shaft is provided in addition to the configuration described in claim 4. Is what you do.

According to a sixth aspect of the present invention, in accordance with the configuration of any of the first to fifth aspects, as the steering angle of the steering wheel from the neutral position of the steering wheel increases, the steering angle increases. A steering angle ratio changing means for reducing the angle ratio is provided.
Next, the invention described in claim 7 corresponds to claims 1 to 6
And a turning angle changing means for setting a turning angle of a steered wheel with respect to a steering angle of the steering wheel to be larger as the vehicle speed is lower.

Next, according to the present invention, the steering angle ratio increases as the vehicle speed increases, and the steering angle ratio with respect to the vehicle speed increases. And a steering angle ratio adjusting means for controlling the rate of change of the vehicle to be larger when the vehicle is moving backward than when the vehicle is moving forward. Next, a ninth aspect of the present invention is characterized in that, when the vehicle speed is low, the steering angle ratio when the vehicle is moving backward is smaller than the steering angle ratio when the vehicle is moving forward. It is assumed that.

[0011]

According to the first aspect of the present invention, one of the plurality of cardan joints is offset from a straight line connecting the lower end of the input shaft and the upper end of the output shaft, so that the link between the links connected by the cardan joints is offset. In addition, since an intersection angle occurs according to the offset, changing the offset amount changes the rotation amount of the output shaft with respect to the rotation amount of the input shaft, that is, the steering angle ratio can be changed.

According to the second aspect of the present invention, the distance between the input shaft and the first link member, the distance between the first link member and the second link member, and the distance between the input shaft and the first link member according to the offset amount of the third cardan joint. The angle of intersection between the second link member and the output shaft changes,
There is an effect that the steering angle ratio can be changed according to the intersection angle. Here, the present invention utilizes the non-uniformity of the Cardan joint. That is, the steering angle ratio is made variable utilizing the fact that a relative rotation angle difference occurs between the links connected by the cardan joint in accordance with the intersection angle at each cardan joint.

According to the third aspect of the invention, the steering angle ratio can be changed without swinging the input shaft and the output shaft. Here, the relative rotation angle difference between the links connected by the cardan joints is such that the speed-up period and the deceleration period are repeated every time the rotation angle advances by 90 degrees. When a rotation exceeding 90 degrees occurs in the above, the torque fluctuation due to the switching between the acceleration and the deceleration is input to the driver operating the steering wheel, and the driver feels a sense of discomfort.

On the other hand, according to the fourth aspect of the present invention, the rotation transmitted to the variable steering angle mechanism is reduced by the reduction gear, so that the steering wheel can be steered 90 degrees or more to the left and right. In addition, the maximum rotation angle of the link connected by the cardan joint constituting the variable steering angle mechanism can be restricted to 90 degrees or less. That is, the repetition of torque fluctuations in the variable steering angle mechanism can be suppressed, and the above-described uncomfortable feeling of the driver can be avoided.

According to a fifth aspect of the present invention, even when the rotation transmitted to the variable steering angle mechanism is decelerated or decelerated, the transmission is transmitted from the variable steering angle mechanism to the output shaft. It is avoided that the turning angle of the steered wheels is reduced by increasing the rotation speed. Note that the gear ratio of the speed-up gear and the reduction gear ratio need not be the same. According to the invention of claim 6, the smaller the steering angle of the steering wheel is,
Since the steering angle ratio becomes large (because the steering angle with respect to the steering angle becomes small), the stability of the vehicle when the vehicle is running with the steering angle of the operated steering wheel being small is ensured. Also, as the steering angle of the steering wheel is larger, the steering angle ratio is smaller (because the steering angle with respect to the steering angle is larger), so that the steering responsiveness when the steering angle of the operated steering wheel is larger than a certain degree is improved. Can be done.

According to the seventh aspect of the present invention, even when the steering angle of the steering wheel is the same, the steering angle of the steered wheels is set to be relatively small during high-speed running to improve the response to steering. By making the vehicle dull, the behavior of the vehicle is stabilized. On the other hand, when driving at low speeds, the steering response is made agile by increasing the steering angle of the steered wheels relatively.
It is possible to reduce the amount of steering angle operated by the steering wheel when entering the garage or the like, thereby reducing the troublesomeness of operating the steering wheel.

According to the present invention, the steering angle ratio increases as the vehicle speed increases, so that the response of the steering wheel steering becomes slower as the vehicle travels at a higher speed, thereby contributing to vehicle stability. In addition, the vehicle stability is not better than when the vehicle is traveling forward because the driver normally takes an excessive posture or travels while looking in a mirror when traveling backward as compared with traveling forward. In particular, it becomes more remarkable as the vehicle speed increases. On the other hand, in the invention according to claim 7, the rate of increase in the steering angle ratio is larger at the time of retreat than at the time of forward movement. Becomes smaller, the steering responsiveness of the vehicle at the time of reversing becomes dull. As a result, the required steering response can be ensured when the vehicle is moving forward, and the stability can be improved without impairing the steering when the vehicle is moving backward.

In particular, when the invention according to claim 9 is adopted,
In a backward garage at a low speed or the like, by reducing the steering angle of the steering wheel even if the rearward unreasonable posture is maintained, the handling can be improved and the operation burden can be reduced.

[0019]

Next, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a steering angle ratio variable steering device according to the present embodiment. First, the configuration will be described. As shown in FIGS. 1 and 2, a first cardan coupling 3 is provided at a lower end of an input shaft 2 interlocked with a steering wheel 1.
One end of the first link member 4 is connected via the
The other end of the link member 4 is connected to the other end of the second link member 8 via the third cardan joint 5, and one end of the second link member 8 is output via the second cardan joint 9. It is connected to the upper end of the shaft 10. The lower end of the output shaft 10
First intermediate shaft 12 via fourth cardan joint 11
Are connected, and a pinion 12a provided on the first intermediate shaft 12 meshes with a steering rack 13 that transmits rotation to wheels (steered wheels), so that rotation of the output shaft 10 can be transmitted to the wheels. . Reference numeral 14 denotes a rubber coupling.

The first to third cardan joints 3, 9,
5, the first link member 4, the second link member 8, and a tilting device 20 described later are located closer to the steering wheel 1 (in the room) than the dash lower 34, and constitute a part of a variable steering angle ratio mechanism. A reduction gear 15 is interposed in the middle of the input shaft 2. That is, the input shaft 2 includes the first input shaft 2a connected to the steering wheel 1 and the first input shaft 2a.
a through a reduction gear 15 and a second input shaft 2b coaxially arranged with the first input shaft 2a. The first link member 4 is connected to the second input shaft 2 b via a first cardan joint 3.

The reduction gear 15 is composed of a planetary gear as shown in FIG. 3 which is a schematic diagram. A sun gear 15a is coaxially fixed to the lower end of the first input shaft 2a.
5a is arranged coaxially with the ring gear 15b, and between the sun gear 15a and the ring gear 15b,
A plurality (two are shown in FIG. 2) of planetary gears 15c meshing with a and 15b are arranged. The plurality of planetary gears 15c are connected by a planetary carrier 15d.
The upper end of the second input shaft 2b is fixed to d. Thus, the rotation of the first input shaft 2a is reduced by the reduction gear 15, that is, decelerated, and transmitted to the second input shaft 2b.

The second link member 8 is composed of a spline shaft 6 and a second intermediate shaft 7 and can be extended and contracted. That is, the spline shaft 6 is connected to the third cardan joint 5 and has a plurality of key grooves parallel to the axis on the outer peripheral surface of the lower portion. The second intermediate shaft 7 can move forward and backward only in the axial direction of the spline shaft 6 with respect to the spline shaft 6.
Are spline-connected.

A speed increasing gear 16 is interposed in the middle of the second intermediate shaft 7. That is, the second intermediate shaft 7 has a first shaft 7a spline-coupled to the spline shaft 6, and a second shaft 7a connected to the first shaft 7a via the speed increasing gear 16 and arranged coaxially with the first shaft 7a. And two shafts 7b. The speed increasing gear 16 is formed of a planetary gear as shown in FIG. 4 which is a schematic diagram, and a sun gear 16a is provided at an upper end of the second shaft 7b.
Is fixed, and the ring gear 1 is coaxial with the sun gear 16a.
6b, and a plurality (two in FIG. 4) of planetary gears 16c meshing with both gears 16a, 16b are arranged between the sun gear 16a and the ring gear 16b. The plurality of planetary gears 16c are connected by a planetary carrier 16d, and the lower end of the first shaft 7a is fixed to the planetary carrier 16d. Thereby, the rotation of the first shaft 7a is increased in angle by the speed increasing gear 16, and the rotation of the second shaft 7a is increased.
b.

Further, on the outer periphery of the first shaft 7a,
A cylindrical cylindrical bracket 17 is arranged coaxially with the first shaft 7a. A bearing 18 is interposed between the outer peripheral surface of the first shaft 7a and the inner peripheral surface of the cylindrical bracket 17. Thereby, the cylindrical bracket 17 and the first
The rotation with respect to the shaft 7a is allowed, so that the cylindrical bracket 17 does not rotate even if the first shaft 7a rotates axially. The casing of the speed increasing gear 16 is supported by a cylindrical bracket 17.

An arm member 19 projects from the cylindrical bracket 17 in the outer diameter direction. A tilting device 2 connected to the tip of the arm member 19 to tilt the second intermediate shaft 7 about the second cardan joint 9 via the arm member 19 and the cylindrical bracket 17.
Has zero. The tilting device 20 includes a housing 21, a third shaft 22, a motor 23, a nut member 24, and a mounting bracket 25.

The housing 21 is connected to the arm 1
9 and the third shaft 22
Is supported such that only the shaft can rotate. Further, the motor 23 is fixed to the housing 21,
The rotation of the motor 23 can be transmitted to the third shaft 22 via the gear 26. That is, the third shaft 22 also rotates by an amount corresponding to the rotation angle of the motor 23. An external thread is engraved on the outer periphery of the other end of the third shaft 22, and the nut member 24 is screwed into the external thread. Reference numeral 27 denotes a coil spring that urges the housing 21 and the nut member 24 in the axial direction of the third shaft 22 and in a direction away from the third shaft 22.

The nut member 24 is connected to the nut member 2 via a mounting bracket 25 as shown in FIG.
4, is fixed to the vehicle body side member 28 so as to be rotatable only about an axis S1 (a direction orthogonal to the plane of FIG. 1) orthogonal to a plane including the first and second cardan joints 3, 9.
In FIG. 5, reference numeral 29 denotes a bearing. With the above configuration, when the third shaft 22 rotates in accordance with the rotation angle of the motor 23, the tilting device 20 displaces the screwing position between the third shaft 22 and the nut member 24, and the nut member is displaced by the displacement. The distance between the housing 24 and the housing 21 changes. Since the position of the nut member 24 is fixed to the vehicle body side, for example, when the distance between the nut member 24 and the housing 21 increases, as shown in FIG. Accordingly, the second link member 8 swings around the second cardan joint 9 via the arm member 19 and the cylindrical bracket 17 in a direction in which the angle with respect to the straight line increases. That is, the third
Is moved in a direction away from the reference line.

The second link member 8 becomes longer as it swings in a direction in which the angle becomes larger with respect to the straight line. The rotation angle and the rotation direction of the motor 23 are controlled by a command from the steering controller 30. Here, the tilting device 20, the variable steering angle ratio mechanism, and the reduction gear 15 constitute a steering angle ratio changing unit. Also, the tilting device 2
0 constitutes a movable means and a swing means.

The steering controller 30 receives a signal corresponding to the traveling speed of the vehicle from the vehicle speed sensor 31 and a signal corresponding to the steering angle from the neutral position of the steering wheel 1 from the steering angle sensor 32 to the gear position sensor 33. , A signal relating to the current traveling state of the vehicle (information on whether the vehicle is moving forward or backward) is input. Here, the gear position sensor 33 is:
For example, if it is M / T, a back lamp drive switch, A
If / T, the shift position sensor corresponds.

The steering controller 30 detects the current traveling speed and traveling direction (forward or backward) of the vehicle and the steering angle of the steering wheel 1 based on the signals input from the sensors 31 to 33, respectively. The target steering angle ratio is determined by a steering angle ratio map set in advance using each detected value as a parameter. Thereafter, a command is output to the motor 23 so that the rotation angle position corresponds to the steering angle ratio. For example, an offset amount of the target steering angle ratio from the current steering angle ratio is obtained, and a rotation command of a rotation angle amount corresponding to the offset amount is output to the motor 23. The steering controller 30 constitutes a turning angle changing unit and a steering angle ratio adjusting unit.

Here, as shown in FIG. 7, the first link shaft 50 and the second link shaft 51 are connected by a cardan joint 52, and a required intersection angle α (deflection angle or bending) is When the first link shaft 50 is rotated at a constant speed in a state in which the (angle) is provided, as shown in FIG.
The second link shaft 51 repeats the acceleration period and the deceleration period in units of 90-degree rotation of the first link shaft 50. In consideration of the rotation angle ratio between the first link shaft 50 and the second link shaft 51, every time the first link shaft 50 rotates 90 degrees,
It means that the rotation angle ratio increases and decreases.

At this time, in this embodiment, even if the maximum steering angle of the steering wheel 1 in the left-right direction is set to 180 degrees, the steering wheel 1 is input to the first and third cardan bearings 3 and 5 by the reduction gear 15. The maximum angle is reduced to 90 degrees or less (FIG. 9 shows a case where the angle is reduced to 45 degrees), so that the steering angle ratio decreases as the steering angle of the steering wheel 1 increases. , The steering angle ratio characteristics can be set.

As can be seen from FIG. 8, focusing on, for example, the acceleration period, the larger the intersection angle α, the larger the change in acceleration,
In other words, in the graph showing the change in the rotation angle ratio, when the curvature of the arc becomes large and the maximum turning angle of the steered wheels is set to a constant value, the smaller the intersection angle α is, the smaller the steering angle of the wheel at the same steering wheel steering angle is always. The cutting angle is set to be large (see FIG. 9).

It is also understood that by changing the intersection angle in this way, a target rotation angle ratio, that is, a target steering angle ratio can be set according to the rotation angle of the first link shaft. Further, in this embodiment, as shown in FIG. 10, the rotation of the input shaft 2 is controlled by the output shaft 1 via three cardan joints 3, 5, and 9.
0, and the third cardan joint 5 is connected to the input shaft 2
The angle of intersection θ1, θ2, θ3 at each of the cardan joints 3, 5, 9 increases as the offset from a straight line H (hereinafter, referred to as a reference line H) connecting the lower end of the output shaft 10 and the upper end of the output shaft 10 increases,
The characteristics of the rotation angle ratio at each of the cardan joints 3, 5, and 9 are the same as those shown in FIG.

Here, the intersection angle θ1 of the first cardan joint 3
When the intersection angle θ2 of the third cardan joint 5 is equal to that of the third cardan joint 5, the unequal velocity is canceled out. However, as shown in FIG. The relative angle difference between the intersection angle θ2 at the first cardan joint 3 and the intersection angle θ1 at the third cardan joint 5 increases. In this way, the third cardan joint 5 is offset from the reference line H, and the intersection angles θ1,
When θ2 and θ3 are increased, a steering angle ratio characteristic equivalent to that obtained by increasing the intersection angle of one cardan joint is obtained, and the steering angle ratio characteristic as shown in FIG. 9 can be obtained. That is, by changing the offset amount of the third cardan joint 5 from the reference line H, the steering angle ratio can be continuously changed, and the target steering angle ratio can be set according to the steering angle. I understand.

The steering angle ratio map is set so as to satisfy the following conditions. The steering angle ratio is set to decrease as the steering angle of the steering wheel 1 from the neutral position of the steering wheel 1 increases. This condition is that the steering angle ratio characteristic shown in FIG. 9 is obtained by limiting the maximum rotation angles of the first cardan joint 3 and the second cardan joint 9 to 90 degrees or less for each of the left and right as described above. The condition is automatically satisfied.

The steering angle of the steering wheel with respect to the steering angle of the steering wheel 1 is set to be larger as the vehicle speed is lower. This condition is automatically satisfied only by increasing the offset amount of the third cardan joint 5 from the reference line H as the vehicle speed increases, based on the steering angle ratio characteristics shown in FIG. As shown in FIG. 11, the steering angle ratio is set to increase as the vehicle speed increases.

This condition is realized by increasing the offset amount of the third cardan joint 5 from the reference line H as the vehicle speed increases. Here, FIG. 11 illustrates a case where the rate of change of the steering angle ratio with respect to the vehicle speed (in this case, the rate of increase) is linear, but along a gentle curve such as a quadratic curve. The steering angle ratio may be increased or may be set so as to increase the steering angle ratio stepwise.

Further, since the steering angle ratio has an upper limit, the steering angle ratio necessarily becomes a constant value of the upper limit steering angle ratio above a predetermined vehicle speed. As shown in FIG. 11, the rate of change of the steering angle ratio with respect to the vehicle speed is set to be larger when the vehicle is moving backward than when moving forward. In FIG. 11, the solid line indicates the steering angle ratio at the time of retreat, and the chain line indicates the steering angle ratio at the time of forward movement.

This condition is realized by increasing the offset amount of the third cardan joint 5 from the reference line H as the vehicle speed increases, by changing the rate of change between forward movement and reverse movement. As shown in FIG. 11, when the vehicle speed is low, the steering angle ratio when the vehicle is moving backward is set smaller than the steering angle ratio when the vehicle is moving forward.

Further, the rotation angle is increased by the speed increasing gear 16 and the rotation is transmitted to the second cardan joint 9, so that the first cardan joint 3 and the third cardan joint 5 are transmitted as described above. Even if the rotation angles at the right and left are suppressed within 90 degrees, the rotation angle transmitted to the output shaft 10 is prevented from being limited to a small value. Here, the second cardan joint 9
In this case, there is a possibility that unequal velocity occurs by rotating to 90 degrees or more, but the intersection angle of the fourth cardan joint is set to substantially the same value as the intersection angle of the second cardan joint 9 and Minutes are offsetting. Note that the swing angle of the second link member 8 about the second cardan joint 9 changes the angle of intersection at the second cardan joint 9. By setting the length to be long, the swing angle of the second link member 8 with respect to the reference line H is suppressed to be small, and the influence thereof is reduced.

Next, the operation of the variable steering angle device having the above configuration will be described. When the third shaft 22 is axially rotated by rotating the motor 23, the screwing position between the third shaft 22 and the nut member 24 changes, so that the distance between the nut member 24 and the housing 21 changes. At this time, since the nut member 24 is fixed to the vehicle body side, the housing 21 swings up and down about the position of the nut member 24 as shown in FIG. When the cylindrical bracket 17 also swings in the same direction, the second link member 8 swings up and down. As a result, the position of the third cardan joint 5 is offset from the reference line H, and the steering angle ratio can be continuously changed. Specifically, as shown in FIG. 6, as the distance between the nut member 24 and the housing 21 increases, the offset amount of the third cardan joint 5 from the reference line H increases.

Even if the steering angle ratio is continuously changed as described above, the input shaft 2 and the output shaft 10 do not swing. Further, a mechanism for varying the steering angle ratio using the cardan joints 3, 5, and 9 is realized, but the steering angle ratio is set so that the change in the steering angle ratio according to the steering angle of the steering wheel 1 becomes gentle. The steering wheel 1
Is turned to the right, the steering angle ratio does not repeatedly increase and decrease. That is, even if the non-uniformity of the Cardan joint is used, the steering wheel 1 is prevented from generating an unacceptable steering torque fluctuation as a reaction,
It is possible to suppress the driver from feeling unnecessary torque fluctuation.

In this embodiment, the smaller the steering angle of the steering wheel 1, the larger the steering angle ratio (because the steering angle with respect to the steering angle becomes smaller). The stability of the vehicle when the vehicle is running with a small steering angle is ensured. Further, since the steering angle ratio becomes smaller as the steering angle of the steering wheel 1 becomes larger (because the turning angle with respect to the steering angle becomes larger), the steering angle of the operated steering wheel 1 is increased to a certain extent such as when turning the vehicle. Steering response can be improved.

Moreover, in this embodiment, the steering angle ratio characteristic of the variable steering angle ratio device satisfies the above condition only by limiting the maximum rotation angle of the variable steering angle ratio mechanism to 90 degrees left and right by the reduction gear 15. Therefore, the control for changing the steering angle ratio is also simplified. Further, since the turning angle of the steered wheels with respect to the steering angle of the steering wheel 1 is set to be larger as the vehicle speed is slower, even when the steering of the steering wheel 1 is the same, the turning angle of the steered wheels is relatively high during high-speed running. By setting it to a small value, the response of the vehicle to steering is made slow to stabilize the behavior of the vehicle. On the other hand, when the vehicle is traveling at low speed, the response to steering is increased by relatively increasing the turning angle of the steered wheels, and the amount of steering angle operated by the steering wheel 1 when the vehicle is put into a garage is reduced to operate the steering wheel 1. Can be reduced.

Since the steered wheels are set to have a smaller turning angle as the vehicle speed is higher, the response of steering of the steering wheel 1 becomes slower as the vehicle travels at a higher speed, which contributes to vehicle stability. In this case, the vehicle stability is not better than when the vehicle is traveling forward since the driver normally takes an unreasonable posture or travels while looking at a mirror when traveling backward as compared with traveling forward. In particular, it becomes more remarkable as the vehicle speed increases. In contrast, in the present embodiment, the ratio of the change in the steering angle ratio with respect to the vehicle speed is set to be larger when the vehicle is moving backward than when moving forward. The rate of increase of the ratio increases, that is, even if the steering angle is the same, the steering response of the vehicle at the time of retreat becomes slower because the ratio of the turning angle becomes smaller at the time of retreat. As a result, the required steering responsiveness is ensured when the vehicle is moving forward, and the stability is improved when the vehicle is moving backward without impairing the maneuverability.

Further, when the vehicle speed is in a low speed range, the steering angle ratio when the vehicle is moving backward is set to be smaller than the steering angle ratio when the vehicle is moving forward. By reducing the steering angle of the steering wheel 1 even in a proper posture, the handling can be improved and the burden of operation can be reduced. Here, in the above-described embodiment, generally, since the vibration from the vehicle speed sensor 31 detects the absolute angular velocity from the frequency of the pulse signal, the rotation direction cannot be detected. For this purpose, the gear position sensor 33 separately determines whether the vehicle is moving forward or backward, but instead of the gear position sensor, a vehicle speed sensor 31 is used.
A means for detecting the rotation direction of the wheel may be provided in the inside, and the forward / backward movement may be determined based on the rotation direction.

In the above embodiment, the second link member 8 is swung by the tilting device 20, but the first link member 4 may be swung by the tilting device 20.
The mechanism of the tilting device 20 is not limited to the above mechanism.
Further, in the above embodiment, the second link member 8 side is configured to be extendable and contractible, but the first link side may be configured to be extendable and retractable.

In the above embodiment, the input shaft 2 and the output shaft 10 are connected by three cardan joints. However, as shown in FIG. 12, the input shaft 2 is connected via four cardan joints. And the output shaft 10 may be connected, or the input shaft 2 and the output shaft 10 may be connected via five or more cardan joints. When the reduction gear 15 is not inserted into the input shaft 2, the steering angle ratio characteristic is, for example, as shown in FIG. 13, and the rate of change of the steering angle ratio starts at a steering angle of 90 degrees (inflection point). Is reversed. If the left and right steering angle ratios are not symmetric, the inflection point is not limited to 90 degrees.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a variable steering angle ratio device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a connection portion between a second link member and an output shaft.

FIG. 3 is a schematic diagram showing a reduction gear.

FIG. 4 is a schematic view showing a speed increasing gear;

FIG. 5 is a diagram showing a mounting structure of a nut member.

FIG. 6 is a view showing swinging of a second link member.

FIG. 7 is a view showing a cardan joint.

FIG. 8 is a view showing non-uniformity of a cardan joint.

FIG. 9 is a diagram showing basic steering angle ratio characteristics according to the embodiment based on the present invention.

FIG. 10 is a view showing an intersection angle at each cardan joint according to the embodiment based on the present invention.

FIG. 11 is a diagram showing a relationship between a vehicle speed and a steering angle ratio according to the embodiment based on the present invention.

FIG. 12 is a diagram of an example in which an input shaft 2 and an output shaft are connected by four cardan joints.

FIG. 13 is a diagram showing a steering angle ratio characteristic when no reduction gear is provided.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 input shaft 2a first input shaft 2b second input shaft 3 first cardan joint 4 first link member 5 third cardan joint 6 spline shaft 7 second intermediate shaft 7a first shaft 7b second shaft 8 2nd link member 9 2nd cardan joint 10 output shaft 11 4th cardan joint 12 1st intermediate shaft 15 reduction gear 16 speed increasing gear 17 cylindrical bracket 18 bearing 19 arm member 20 tilting device 21 housing 22 third shaft 23 motor 24 Nut member 25 Mounting bracket 26 Gear 27 Coil spring 30 Steering controller 31 Vehicle speed sensor 32 Steering sensor 33 Gear position sensor 34 Dash lower

Continued on the front page (72) Inventor Hitoshi Ono 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Inventor Koji Tsuchiya 2 Takaracho, Kanagawa-ku, Yokohama City, Kanagawa Prefecture Nissan Motor Co., Ltd. Person Katsuhiro Suda 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa F-term in Nissan Motor Co., Ltd. (reference) 3D030 DC25 3J027 FA50 FB12 GA01 GB03 GC13 GC22 GD04 GD08 GD12 GE23

Claims (9)

[Claims] 1. An input shaft which is rotated by a steering input from a steering wheel, an output shaft which transmits rotation to a steered wheel, and a rotation of the input shaft which is interposed between the input shaft and the output shaft is used as an output shaft. A variable steering angle ratio steering device for transmitting, wherein the variable steering angle ratio mechanism includes a plurality of cardan joints between a lower end of the input shaft and an upper end of the output shaft. Moving means for moving the position of at least one cardan joint of the plurality of cardan joints in a direction approaching / separating from a straight line connecting the lower end of the input shaft and the upper end of the output shaft. A variable steering angle ratio steering device. 2. The variable steering angle ratio mechanism according to claim 1, wherein one end of the input shaft is connected to a lower end of the input shaft via a first cardan joint.
A link member, a second link member connecting one end to an upper end of the output shaft via a second cardan joint,
A third cardan joint connecting the other end of the link member to the other end of the second link member; and a straight line connecting the position of the third cardan joint to a lower end of the input shaft and an upper end of the output shaft. 2. A variable steering angle ratio steering apparatus according to claim 1, further comprising: a movable means for moving in a direction of approaching / leaving from the steering wheel. 3. The movable means is configured so that at least one of the first link member and the second link member can be expanded and contracted only in the axial direction, and at least one of the first link member and the second link member is connected to the movable member. 3. The variable steering angle ratio steering apparatus according to claim 2, further comprising a swinging unit that swings in a direction of approaching and leaving a straight line connecting a lower end of the input shaft and an upper end of the output shaft. 4. The variable steering angle ratio according to claim 1, further comprising a reduction gear for reducing rotation transmitted from the input shaft to the variable steering angle ratio mechanism. Steering gear. 5. The variable steering angle ratio steering device according to claim 4, further comprising a speed increasing gear for increasing the rotation transmitted from the variable steering angle ratio mechanism to the output shaft. 6. A steering angle ratio changing means for reducing a steering angle ratio as a steering angle of the steering wheel from a neutral position of the steering wheel increases. A variable steering angle ratio steering device according to any one of the preceding items. 7. The steering wheel according to claim 1, further comprising a steering angle changing means for setting a steering angle of the steering wheel with respect to a steering angle of the steering wheel to be larger as the vehicle speed is lower. Variable steering ratio steering system. 8. A steering angle ratio adjusting means for increasing the steering angle ratio as the vehicle speed increases, and controlling the rate of change of the steering angle ratio with respect to the vehicle speed so that the backward movement of the vehicle is larger than that of the forward movement. The variable steering angle ratio steering device according to any one of claims 1 to 7, further comprising: 9. The variable steering angle ratio steering device according to claim 8, wherein, when the vehicle speed is low, the steering angle ratio when the vehicle is moving backward is smaller than the steering angle ratio when the vehicle is moving forward.