JP2000062632A - Vehicular steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the steering incompatibility sense giving to a driver, even in the trouble time of a transmission ratio variable mechanism. SOLUTION: At the trouble time of a transmission ratio variable mechanism 30, an assist force generated by the actuator 60 of a power steering device is changed in response to the deviation of the transmission ratio before/after a trouble. When the transmission ratio at the trouble time becomes quick in comparison with a normal time, a steering reaction is increased and a steering amount is restrained and when it becomes slow, the steering reaction is reduced and the steering amount is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system that steers steered wheels in response to steering of a steering wheel.

[0002]

2. Description of the Related Art Conventionally, there has been known a vehicle steering system having a transmission ratio variable mechanism for changing a transmission ratio of a turning angle of steered wheels to a steering angle of a steering wheel. This transmission ratio variable mechanism connects the input shaft connected to the steering wheel side and the output shaft connected to the rack shaft side with a predetermined gear mechanism, and by driving this gear mechanism with an actuator,
The mechanism is such that the transmission ratio of the rotation amount between the input shaft and the output shaft can be changed.

Further, in the steering device disclosed in Japanese Patent Laid-Open No. 62-23869, the input shaft-output shaft in a state in which the actuator of the variable transmission ratio mechanism is stopped in case of failure of such variable transmission ratio mechanism. The base transmission ratio, which is the transmission ratio between them, is set to the intermediate value of the variable width of the transmission ratio. By setting in this way, even when the actuator that changes the transmission ratio is stopped, it is possible to avoid a situation in which the transmission ratio greatly changes compared to the normal state, and to reduce the discomfort felt by the driver.

[0004]

However, the transmission ratio set by the transmission ratio variable mechanism is usually set in accordance with the running state such as the vehicle speed, and is large in the low vehicle speed range and small in the high vehicle speed range. Is set. On the other hand, when the transmission ratio variable mechanism fails, the set transmission ratio of the transmission ratio variable mechanism is maintained at the base transmission ratio described above even if the running state of the vehicle changes. The steering feeling of the person changes.

The present invention has been made to solve such a problem, and an object thereof is for a vehicle capable of reducing a driver's uncomfortable steering feeling even when a transmission ratio variable mechanism fails. To provide a steering device.

[0006]

Therefore, a vehicle steering system according to a first aspect of the present invention is a vehicle steering system for steering a steered wheel in accordance with steering of a steering wheel, wherein the steered wheel corresponds to a steering angle of the steering wheel. Ratio changing means for changing the transmission ratio of the turning angle of the steering wheel according to the running state of the vehicle, a reaction force generating means for generating a steering reaction force which is a resistance force against the operation of the steering wheel, and a transmission ratio changing means. And a control means for controlling the magnitude of the steering reaction force generated by the reaction force generation means according to the deviation of the transmission ratio before and after the failure.

When the transmission ratio varying means is normal, the set transmission ratio changes according to the running state of the vehicle. However, in the case of a failure, even if the running state of the vehicle changes, the predetermined transmission ratio is set as described above. The base transmission ratio is maintained. As a result, even when the steering wheel is steered by a predetermined amount, the steering angle of the steered wheels is unexpectedly large or small, which gives the driver a feeling of strange steering.

On the other hand, normally, the driver operates the steering wheel with a constant steering force, and when the steering reaction force decreases, the steering wheel operation becomes light and the amount of rotational steering tends to increase. On the contrary, when the steering reaction force increases, the steering wheel operation becomes heavier and the rotational steering amount tends to be suppressed. This effect is utilized when the transmission ratio variable mechanism fails, for example,
The transmission ratio set at the time of failure is a small value (slow) compared to the transmission ratio at normal time set according to the running condition of the vehicle.
Under such a situation, the steering reaction force generated by the reaction force generating means is reduced and the amount of rotational operation of the steering wheel is increased.
As a result, the steered angle of the steered wheels is also increased, and the driver's uncomfortable feeling of steering is reduced. On the other hand, under a situation where the transmission ratio at the time of failure becomes a larger value (quick) than that at the normal time, the steering reaction force generated is increased to suppress the rotational operation amount of the steering wheel, and the steering angle of the steered wheels is reduced. Suppress.

A vehicle steering system according to a second aspect is the vehicle steering system according to the first aspect, wherein the reaction force generating means is an assisting force generating means for generating an assisting force at the time of steering, and the control means is: When the transmission ratio set at the time of failure of the transmission ratio variable means is smaller than that at the normal time, it is increased with respect to the steering assist force that should be generated at the normal time, and the transmission ratio set at the time of failure is increased compared to the normal time. In order to reduce the steering assist force that should occur during normal operation,
Controls the amount of steering assist force.

As described above, in a situation where the transmission ratio set at the time of failure decreases as compared with the value at the normal time set according to the running state of the vehicle, the steering assist force is generated at the normal time. By increasing with respect to the power size, the amount of rotation operation of the steering wheel is increased, and the steered angle of the steered wheels is also increased. By this action, the shortage of the steered angle of the steered wheels caused by the change of the transmission ratio due to a failure can be compensated. Further, in a situation where the transmission ratio set at the time of failure increases compared to the value at the normal time set according to the running state of the vehicle, the steering assist force is compared with the magnitude that should be generated at the normal time. By reducing the amount, the rotational operation amount of the steering wheel is suppressed, and the steered angle of the steered wheels is also reduced. This action can compensate for the increase in the steered angle of the steered wheels caused by the change in the transmission ratio due to a failure, and reduce the feeling of strange steering caused by the change in the transmission ratio.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a steering apparatus according to the embodiment.

The input shaft 20 and the output shaft 40 are connected via a transmission ratio variable mechanism 30, and the steering handle 10 is connected to the input shaft 20. The output shaft 40 is connected to a rack shaft 51 via a rack and pinion type gear device 50, and wheels FW are connected to both sides of the rack shaft 51.

The input shaft 20 is provided with an input angle sensor 21 for detecting the steering position of the steering wheel 10, and the output shaft 40 is provided with an output angle sensor 41 for detecting the rotational position of the output shaft 40.
A torque sensor 42 for detecting the steering torque T is provided. The rotation angle of the output shaft 40 corresponds to the stroke position of the rack shaft 51, and the stroke position of the rack shaft 51 corresponds to the turning angle of the wheel FW.
By detecting the rotation angle of the output shaft 40 by
The steering angle of W is detected.

The transmission ratio variable mechanism 30 includes the steering handle 10.
Is a mechanical unit that changes a transmission ratio G (G = steering angle / steering angle) between the steering angle of the input shaft 20 and the steering angle of the wheel FW.
A mechanism in which the rotation amount transmitted between the input shaft 20 and the output shaft 40 can be changed by connecting the output shaft 40 and the output shaft 40 by a gear mechanism and rotating a predetermined gear constituting the gear mechanism by the actuator 31. Has become.

Further, the rack shaft 51 is provided with an actuator 60 constituting an electric power steering device, and a steering assist force is applied by displacing the rack shaft 51 in the axial direction by the actuator 60. The steering force for the driver to operate the steering wheel 10 is reduced.

The actuator 31 of the transmission ratio variable mechanism 30 and the actuator 60 of the power steering device.
The drive control of is performed by the control device 70. The steering control device 70 includes an input angle sensor 21 and an output angle sensor 4.
1. In addition to the steering torque sensor 42, each detection signal from the vehicle speed sensor 44 for detecting the vehicle speed V is given, and the drive control of the actuator 31 and the actuator 60 is performed based on these signals.

Here, of the respective control processes executed by the control device 70, first, drive control of the actuator 31 will be described with reference to the flowchart of FIG.

This flowchart is started by turning on the ignition switch. First, the process proceeds to step (hereinafter referred to as “S”) 102, where the input angle θh detected by the input angle sensor 21 and the output angle sensor 41 are detected.
The value of the output angle θp detected in step 1 and the value of the vehicle speed V detected by the vehicle speed sensor 44 are read.

At S104, it is determined whether the transmission ratio variable mechanism 30 is functioning normally. For example, when the input angle θh is not detected or indicates an abnormal value, the output angle θp with respect to the control signal I ₁ described later does not match, or the overcurrent flows through the actuator 31, a failure occurs in the transmission ratio variable mechanism 30. It is determined that the operation has been performed ("N
o ”), the process proceeds to S116, where a fail flag F indicating that a failure has occurred in the transmission ratio variable mechanism 30 is set to 1. The fail flag F is reset when the ignition switch is turned off.

On the other hand, when it is determined in S104 that the transmission ratio variable mechanism 30 is normal ("Yes" in S104).
s "), the process proceeds to S106, where the vehicle speed V and the transmission ratio G shown in FIG.
Based on the vehicle speed V read in S102, a map is searched from a map showing the relationship with, and a transmission ratio G corresponding to the vehicle speed V is set.

In subsequent S108, θpm = Gθh is calculated based on the transmission ratio G set in S106 and the input angle θh read in S102 to set the output angle target value θpm.

In subsequent S110, the deviation e between the output angle target value θpm set in S108 and the output angle θp detected by the output angle sensor 41 is calculated as e = θpm−θp.

In subsequent S112, the actuator 31 is set so that the deviation e is set to 0 without overshooting.
A control signal I ₁ for controlling As an example of this processing, PI based on the arithmetic expression of I ₁ = C (s) · e
The control signal I ₁ can be determined by appropriately setting the D control parameters. In addition, "s" in a formula is a Laplace operator.

In subsequent S114, the control signal I ₁ determined in S112 is output to the actuator 31, and the actuator 31 is driven according to the control signal I ₁ .

Then, this S114 or the previously described S
After 116, the process proceeds to S118, where it is determined whether the ignition switch (IG) is turned off. If "No", the process returns to S102, and the process from S102 described above is repeated until "Yes" is determined in S118. The process is repeatedly executed.

By repeating such processing, the vehicle speed V
The transmission ratio G is set in accordance with the above, and based on the set transmission ratio G, steering control of the wheels FW is performed according to the input angle θh.

Next, drive control of the actuator 60 constituting the power steering device, which is carried out by the control device 70, will be described with reference to the flowchart of FIG.

This flowchart is started by turning on the ignition switch. First, in S202, it is determined whether the fail flag F indicating a failure of the transmission ratio variable mechanism 30 is set to 1.

When the fail flag F is reset in S202 (when F = 0), the process proceeds to S204,
The value of the correction coefficient k is set to 1. The correction coefficient k will be described later.

In the following S206, the steering torque T detected by the torque sensor 42 is read, and in the following S208,
From the map showing the relationship between the steering torque T and the control amount i shown in FIG. 5, a map search is performed based on the steering torque T read in S206, and the control amount i corresponding to the steering torque T is set.

At S210, I = k * i is calculated,
A control amount I for controlling the actuator 60 is set. Thus, “k” is a correction coefficient for correcting the control amount i set in S208, and “No” in S202 above.
If it is determined that K = 1 in S204, the correction process is not substantially performed, and the value of the control amount i is set as it is as the control amount I.

In the following S212, the control signal I ₂ for controlling the actuator 60 is determined based on the arithmetic expression of I ₂ = C (s) · I. In addition, "s" in a formula is a Laplace operator.

In subsequent S214, the control signal I ₂ determined in S212 is output to the actuator 60, and the actuator 60 is driven according to the control signal I ₂ .

After passing through S214, the process proceeds to S216, where it is determined whether the ignition switch (IG) is turned off. If "No", the process returns to S202 and S21.
Until S6 is determined to be "Yes", the above-described processing from S202 is repeatedly executed.

As described above, while the variable transmission ratio mechanism 30 is operating normally, the drive control of the actuator 60 is executed as described above, and the steering assist force corresponding to the steering torque T is generated.

On the other hand, when the transmission ratio variable mechanism 30 has a failure, the drive control of the actuator 31 is not performed and the actuator 31 is stopped as shown in the flowchart of FIG. Actuator 3
When 1 stops, the transmission ratio G set by the transmission ratio variable mechanism 30 becomes a transmission ratio peculiar to the gear mechanism configuring the transmission ratio variable mechanism 30 (hereinafter referred to as the base transmission ratio). An example will be described in which the base transmission ratio is set to an intermediate value of the transmission ratio variable width as indicated by a dotted line in FIG.

If a failure has occurred in the transmission ratio variable mechanism 30, it is determined to be "Yes" in S202 and S2.
Proceed to 18.

In S218, the vehicle speed V detected by the vehicle speed sensor 44 is read, and in the subsequent S220, S218 from the map showing the relationship between the vehicle speed V and the correction coefficient k shown in FIG.
A map search is performed based on the vehicle speed V read in, and the correction coefficient k corresponding to the vehicle speed V is set. The correction coefficient k is set based on the change in the transmission ratio before and after the failure. Referring to FIG. 4, in the low vehicle speed range, the base transmission ratio when the transmission ratio variable mechanism 30 is out of order is set to a slower side than the transmission ratio G in the normal state, which is the same as in the normal state. In order to steer the wheels FW, it is necessary to steer the steering wheel 10 more than in the normal state. On the other hand, in the high vehicle speed range, the base transmission ratio set at the time of failure is set to a quicker side than the transmission ratio G at the normal time, and the wheels FW are steered similarly to the normal time. It is necessary to steer the steering wheel less than in the normal state.

Therefore, as in the low vehicle speed range in FIG.
When the base transmission ratio at the time of failure is set to a slower side than the transmission ratio G according to the vehicle speed V that should be set at the normal time (before failure), the value of the correction coefficient k is set to a large deviation. The value is set to be larger than 1 (low vehicle speed range in FIG. 6). As a result, in the process of S210, the control amount I for the actuator 60 of the power steering device increases as compared to the normal state, and the assist force (steering assist force) during steering increases and the steering reaction force felt by the driver is Decrease (low vehicle speed range in FIG. 7). For this reason, the steering wheel operation becomes lighter than in the normal state, and for the driver who steers with a constant steering force, the steering amount tends to unknowingly increase, and the steering amount of the wheel FW also increases.

On the contrary, like the high vehicle speed range in FIG.
When the base transmission ratio at the time of failure is set to the quick side, the value of the correction coefficient k is set to be smaller than 1 according to the magnitude of the deviation (high vehicle speed range in FIG. 6). As a result, in the process of S210, the control amount I for the actuator 60 of the power steering device is increased.
Is smaller than that in the normal state, the assist force during steering (steering assist force) is reduced and the steering reaction force felt by the driver is increased (high vehicle speed range in FIG. 7). For this reason, the steering wheel operation becomes heavier than in the normal state, and the driver who steers with a constant steering force tends to unconsciously decrease the steering amount, and the steering amount of the wheels FW also decreases.

In this way, even when the set transmission ratio is changed due to the failure of the transmission ratio variable mechanism 30 as compared with the normal state, the magnitude of the steering assist force is changed to change the set transmission ratio. It is possible to reduce the uncomfortable steering feeling.

Further, as shown in FIG. 8, in the transmission ratio variable mechanism 30 of the type in which the base transmission ratio is set to the slow side with respect to the transmission ratio variable region, the influence of the change of the transmission ratio in the low vehicle speed range is affected. Receive more strongly. Also in this case, by setting the correction coefficient k according to the vehicle speed V as shown in FIG. 9 based on the deviation between the transmission ratio G and the base transmission ratio according to the vehicle speed V that should be set under normal conditions. As shown in FIG. 10, the steering reaction force felt by the driver decreases more as the vehicle speed decreases, and the driver tends to unintentionally increase the steering amount, and the same effect is exhibited. It

Further, as shown in FIG. 11, in the transmission ratio variable mechanism 30 of the type in which the base transmission ratio is set on the quick side with respect to the transmission ratio variable region, the influence of the change of the transmission ratio in the high vehicle speed range is affected. Receive more strongly. Also in this case, by setting the correction coefficient k according to the vehicle speed V as shown in FIG. 12, based on the deviation between the transmission ratio G and the base transmission ratio according to the vehicle speed V that should be set under normal conditions. The steering reaction force felt by the driver increases as the vehicle speed increases, as shown in FIG. 13, and the driver unconsciously decreases the steering amount, and the same effect is exhibited. .

In the above-described embodiment, the case where the control amount i for the actuator 60 of the power steering device is corrected in the entire speed range when the transmission ratio variable mechanism 30 is out of order has been exemplified. For example, the base transmission ratio is variable. In the case of FIG. 4 set within the region, the steering force assist by the actuator 60 may be stopped in the vehicle speed range equal to or higher than the vehicle speed Vm at which the normal transmission ratio G and the base transmission ratio match. As a result, during a failure of the transmission ratio variable mechanism 30, the steering reaction force becomes large in the high vehicle speed range, the steering operation becomes heavy, and the traveling stability in the high vehicle speed range is secured.

Although the electric power steering device has been illustrated as a mechanism for applying such a steering assist force, it can be similarly applied to a hydraulic power steering device.

Further, the mechanism for changing the steering reaction force is not limited to the power steering device for displacing and driving the rack shaft 51, but any mechanism capable of changing the resistance force to the rotational operation of the steering handle 10 may be used. Can be applied. For example, it is also possible to use a variable flow rate type hydraulic pump that controls the flow rate of the discharged fluid by a pump motor and apply it to a reaction force variable system that controls the steering reaction force by hydraulic pressure. When the ratio is set to the slower side, the steering reaction force is reduced by correcting it so that it decreases with respect to the normal fluid flow rate, depending on the magnitude of the deviation of the transmission ratio before and after the failure.
When the transmission ratio after a failure is set to a quicker side, the steering reaction force is corrected by correcting it to increase with respect to the normal fluid flow rate according to the magnitude of the deviation of the transmission ratio before and after the failure. It may be controlled so as to increase.

[0048]

As described above, according to the vehicle steering system of the claims, the steering reaction force generated by the reaction force generation means in accordance with the change of the transmission ratio before and after the failure of the transmission ratio varying means. Since it has a control means for controlling the size of
By controlling the steering reaction force at the time of failure, the driver who operates the steering wheel adjusts the steering amount unknowingly and suppresses the influence of the transmission ratio change at the time of failure. Even if a failure occurs, it is possible to reduce the uncomfortable feeling of steering given to the driver.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a vehicle steering system according to an embodiment.

FIG. 2 is a flowchart showing a control process of a transmission ratio variable mechanism.

FIG. 3 is a flowchart showing a control process of the power steering device.

FIG. 4 is a map defining the relationship between vehicle speed and transmission ratio.

FIG. 5 is a map defining the relationship between steering torque and control amount.

FIG. 6 is a map defining a relationship between vehicle speed and a correction coefficient.

FIG. 7 is a graph showing a relationship between a vehicle speed and a steering reaction force when the transmission ratio variable mechanism is normal and when it is out of order.

FIG. 8 is a map defining a relationship between vehicle speed and transmission ratio.

FIG. 9 is a map defining the relationship between vehicle speed and correction coefficient.

FIG. 10 shows a transmission ratio variable mechanism at a normal time and at a failure time.
5 is a graph showing the relationship between vehicle speed and steering reaction force.

FIG. 11 is a map defining the relationship between vehicle speed and transmission ratio.

FIG. 12 is a map defining a relationship between vehicle speed and a correction coefficient.

FIG. 13 shows a transmission ratio variable mechanism at a normal time and at a failure time.
5 is a graph showing the relationship between vehicle speed and steering reaction force.

[Explanation of symbols]

10 ... Steering wheel, 20 ... Input shaft, 21 ... Input angle sensor, 30 ... Transmission ratio variable mechanism, 31 ... Actuator, 4
0 ... Output shaft, 41 ... Output angle sensor, 42 ... Torque sensor, 60 ... Actuator, 70 ... Control device.

Claims (2)

[Claims] 1. A vehicle steering system for steering steered wheels according to steering of a steering wheel, wherein a transmission ratio of a steered angle of a steered wheel to a steering angle of a steering wheel is changed according to a traveling state of a vehicle. A transmission ratio varying means for changing, a reaction force generating means for generating a steering reaction force, which is a resistance force to the operation of the steering wheel, and a failure of the transmission ratio varying means, depending on a deviation of the transmission ratio before and after the failure. And a control means for controlling the magnitude of a steering reaction force generated by the reaction force generation means. 2. The reaction force generating means is an assisting force generating means for generating an assisting force at the time of steering, and in the control means, the transmission ratio set when the transmission ratio varying means is out of order is compared to when the transmission ratio is normal. If the transmission ratio set at the time of failure increases compared to the normal time,
The vehicle steering system according to claim 1, wherein the magnitude of the steering assist force is controlled so as to be reduced with respect to the steering assist force that should be generated during normal operation.