JPS6328764A - Steering control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent sudden change of an assist force before and after the occurrence of abnormality, by a method wherein, when abnormality occurs to car speed detecting means, when a control value exceeds a fuel safe value, the control value is held at a control value right before detection of abnormality. CONSTITUTION:An oil pressure is fed through a control value 7 to a hydraulic cylinder 6 with the aid of a constant flow rate oil pump 8, a part of oil from the oil pump 8 is returned to the low pressure side through a bypass passage 9, and an electromagnetic valve 10, continuously varying a throttle amount according to a current, is located in the middle of the bypass passage. A voltage is fed to a solenoid 10a of the electromagnetic valve 10 from a control device 11, and a signal, e.g. a car speed, a steering speed, a mode switch, from a car speed sensor 12 serving as a car speed detecting means, is inputted to the control device 11. The control device 11 forms a control value set means, a fuel safe value set means, an abnormal detecting means, and a selecting means.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to a vehicle steering control device that controls a steering assist force or rear wheel turning angle according to vehicle speed, such as a power steering device or an automatic stability control device. Regarding.

<Conventional technology> Conventionally, power steering devices that generate steering assist force and automatic stability control devices that steer rear wheels when steering the front wheels detect vehicle speed based on a signal from a vehicle speed sensor, and detect the detected vehicle speed. The steering assist force and rear wheel turning angle are controlled accordingly (see Utility Model Application No. 60-115106, Utility Model Application No. 61-9570, etc.).

To explain this using a power steering system as an example, as shown in Fig. 4, there is a town mode in which the steering assist force is changed at a relatively large value in response to changes in vehicle speed, and a town mode in which the steering assist force is changed at a relatively small value in response to changes in vehicle speed. It has a sports mode that changes according to changes. and,
The driver selects either town mode or sport mode using the mode switch, and the steering assist force is changed according to the selected mode based on the vehicle speed signal from the vehicle speed sensor. In this way, the steering force is assisted by the steering assist force.

In addition, when an abnormality occurs in the output value of the vehicle speed sensor,
Regardless of the selection of town mode or sport mode and the vehicle speed, the steering assist force is maintained at a substantially constant fail-safe level as shown in FIG. 4 Mbi.

<Problems to be Solved by the Invention> However, in such conventional steering control devices, such as power steering devices, when the steering force is assisted with a steering assist force exceeding the fail-safe level, the vehicle speed When an abnormality occurs in the sensor, the steering assist force rapidly changes to the fail-safe level.

As a result, the steering force is suddenly reduced, and if such a situation occurs while driving on a curved road, there is a risk of a vehicle accident.

Furthermore, the automatic stability control system also has the above-mentioned problem because the steering angle changes rapidly.

The present invention has been made in view of the above-mentioned circumstances, and provides a vehicle steering control device that can prevent the steering assist force or steering angle from suddenly changing in a dangerous direction even if an abnormality occurs in the vehicle speed sensor. The purpose is to provide.

Therefore, as shown in FIG. 1, the present invention includes a vehicle speed detection means A that detects the vehicle speed, and a control that sets a control value by changing it according to the detected vehicle speed. A value setting means B, a fail-safe value setting means C for setting a fail-safe value determined as an intermediate value in the range in which the control B value changes, and an abnormality detecting means for detecting an abnormality in the vehicle speed detecting means A. When an abnormality is detected, if the control value exceeds the failsafe value, the control value immediately before the abnormality is detected is selected and held, while when the control value is less than the failsafe value, the failsafe value is selected and the control value is not abnormal. selection means E for selecting the control value upon detection; and steering control means F based on the selected value.
and a driving means G for driving.

In this manner, when the control value exceeds the failsafe value at the time of abnormality detection, control is performed by holding the control value at the control value immediately before the abnormality detection.

<Example> An example of the present invention will be described below with reference to FIGS. 2 and 3. In this embodiment, a power steering device will be explained as an example.

In the figure, reference numeral 1 is a steering wheel, and by rotating the steering wheel, a steering shaft 2. Pinion 3. Wheels 5 are steered via racks 4 and the like. Reference numeral 6 denotes a double-acting hydraulic cylinder called a power cylinder, which serves as a steering control means, and provides a steering assist force. Reference numeral 7 denotes a control valve that is operated in the left and right directions in the figure in conjunction with the steering wheel 1 according to its rotational direction, and in the neutral position, it guides the hydraulic pressure from the oil pump 8 to the hydraulic chambers 6a and 6b of the hydraulic cylinder 6. Although no steering assist force is generated in either direction, when the steering wheel 1 is rotated to the right, this valve 7 moves to the right in the figure and guides the hydraulic pressure from the oil pump 8 only to the hydraulic chamber 6a, thereby reducing the hydraulic pressure. By pushing the piston 6c in the cylinder 6 to the left in the figure, a steering assist force is generated in the right direction. When the steering wheel 1 is rotated to the left, the valve 7 moves to the left in the figure and the oil is By guiding the hydraulic pressure from the pump 8 only to the hydraulic chamber 6b and pushing the piston 6c in the hydraulic cylinder 6 to the right in the figure, a leftward steering assist force is generated.

Further, hydraulic pressure is supplied to the hydraulic cylinder 6 from a constant flow oil pump 8 via a control pulp 7, but part of the oil from the oil pump 8 is returned to the low pressure side through a bypass passage 9, and a part of the oil from the oil pump 8 is returned to the low pressure side through a bypass passage 9. A solenoid valve 10 whose opening degree (amount of throttle) is continuously variable according to the current is provided in the middle. Therefore, the solenoid section 10 of the electromagnetic valve 10
By increasing the current to a and decreasing the opening degree of the solenoid valve 10, the bypass flow rate becomes smaller, the oil pressure to the hydraulic cylinder 6 increases, and the steering assist force can be increased.

Voltage is supplied to the solenoid portion 10a of the solenoid valve 10 from a control device 11.
The vehicle speed from the vehicle speed sensor 12 as a vehicle speed detection means,
Signals such as steering speed and motor switch are input. The control device 111 operates according to the flowchart shown in FIG.
It is designed to be sent to a.

Here, the control device 11 constitutes a control value setting means, a fail-safe value setting means, an abnormality detection means, and a selection means, and the control valve 7 and the t6fi valve 10 constitute a driving means.

Next, the operation will be explained according to the flowchart shown in FIG.

Sl reads various signals such as vehicle speed, steering speed, mode switch, etc.

In S2, based on the input of the vehicle speed sensor 12, for example, if the vehicle speed sensor 12 is malfunctioning or the vehicle speed sensor 12 and the control device 1
It is determined whether there is a break in the lead wire between the vehicle speed sensor 12 and the vehicle speed sensor 12. If the answer is YES, the process advances to S3, and if the result is NO, the process advances to S4. Specifically, when the vehicle speed signal is not input from the vehicle speed sensor 12 under the conditions that the vehicle is running (for example, the engine speed is above a predetermined value, the engine is not in neutral, and the clutch is engaged), the vehicle speed sensor 12 abnormalities are determined.

In S4, it is determined whether or not the mode selected by the mode switch is set to town mode. If YES, the process proceeds to S5; if NO, the process proceeds to S6.

In S5, the steering assist force is changed based on the detected vehicle speed from the town mode in which the steering assist force as a control value is changed in response to changes in vehicle speed by a relatively large value as in the conventional example, as shown in FIG. Search and set.

On the other hand, in S6, as shown in Fig. 4, the steering assist force is searched based on the detected vehicle speed from the sport mode in which the steering assist force is changed in a relatively small value corresponding to changes in vehicle speed, as in the conventional example. and set it.

Further, when it is determined that the vehicle speed sensor 12 is abnormal, S3
Then, it is determined whether or not the steering assist force immediately before abnormality detection exceeds the fail-safe assist force as a fail-safe value at the time of fail-safe.If YES, the process advances to S7, and if NO, the process advances to S8.

Here, as shown in FIG. 4, the failsafe assist force is set to a constant value between the steering assist forces that change in response to changes in vehicle speed regardless of whether the vehicle is in town mode or sport mode.

In S7, the steering assist force is maintained at the level immediately before the abnormality was detected, and in S8, the fail-safe assist force is set.

In S9, a current corresponding to the steering assist force set in any one of 86 to S8 is applied to the solenoid section 10 of the solenoid valve 1o.
Output to a.

As a result, the bypass flow rate is controlled and the hydraulic pressure supply to the hydraulic cylinder 6 is controlled. i is achieved, and a predetermined steering assist force can be secured.

As explained above, when the steering assist force exceeds the fail-safe assist force when an abnormality is detected by the vehicle speed sensor 12, the steering assist force is held at the level immediately before the abnormality was detected. Even if an abnormality occurs in the sensor 12, the same steering assist force can be ensured before and after the abnormality occurs, thereby preventing sudden changes in the steering force and ensuring safety in vehicle running. Note that when the steering assist force at the time of abnormality detection is less than the failsafe assist force, the steering assist force is kept constant by the failsafe assist force, but in this case, the steering force is controlled to be heavier, so that the vehicle travels smoothly. There is no risk of

Incidentally, when the ignition switch is turned on again, abnormality detection of the vehicle speed sensor 12 is performed for 10 seconds, and then the system shifts to the fail-safe assist force in the event of an abnormality.

<Effects of the Invention> As explained above, in the present invention, when the control value exceeds the ferrule safe value when an abnormality is detected by the vehicle speed detection means, the control value is held at the value immediately before the abnormality was detected.
Approximately the same steering assist force or steering angle can be ensured before and after the occurrence of an abnormality, and the safety of vehicle running can be ensured.

[Brief explanation of the drawing]

Fig. 1 is a claim correspondence diagram of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Fig. 3 is a flowchart of the same as above,
FIG. 4 is a diagram for explaining the operation of the embodiment and the conventional example. 6...Double acting hydraulic cylinder 7...Control valve 10...Electric %i valve 11...Control device 12...Vehicle speed sensor

Claims (1)

[Claims] A vehicle speed detection means for detecting vehicle speed, a control value setting means for changing a control value according to the detected vehicle speed, and setting a fail-safe value determined as an intermediate value in a range in which the control value changes. fail-safe value setting means; abnormality detection means for detecting an abnormality in the vehicle speed detection means; and one-sided control for selecting and holding the control value immediately before the abnormality detection when the control value exceeds the fail-safe value when the abnormality is detected. A selection means for selecting the fail-safe value when the value is less than the fail-safe value and selecting the control value when no abnormality is detected, and a driving means for driving the steering control means based on the selected value. A vehicle steering control device characterized by: