JPH0356234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power steering device installed in a vehicle, and particularly relates to a measure for increasing and correcting the steering force near the roll limit when the vehicle turns. be.

(Prior Art) Generally, when a vehicle is cornering, the vehicle body rolls due to the effect of lateral acceleration, and when this roll reaches near its limit, the grip force of the tires decreases and the steering force of the steering wheel decreases. For this reason, especially in vehicles equipped with a power steering device that uses a power cylinder to assist the steering force, the steering suddenly becomes sharp near the roll limit, causing a so-called loose steering feel. As a result, a problem may arise in which the steering feel becomes unstable.

In order to solve this problem, conventionally, as disclosed in Japanese Utility Model Publication No. 51-5148, etc., an acceleration sensor is provided to detect the lateral acceleration that occurs when the vehicle is cornering. When the vehicle reaches its roll limit, the power cylinder's assist force to the steering force is cut off, increasing the steering force near the vehicle's roll limit and reducing the feeling of loose steering. Some proposals have been made to eliminate this.

However, in this conventional system, the lateral acceleration acting on the vehicle is detected by an acceleration sensor, so the assist force is cut off after the lateral acceleration actually acts, resulting in poor responsiveness near the roll limit. , there is room for further improvement in terms of responsiveness.

In addition, in order to uniformly cut off the assist force when the vehicle reaches its roll limit, it is not possible to reduce the assist force depending on the magnitude of the lateral acceleration acting on the vehicle, and it is necessary to perform accurate control. is difficult.

(Object of the invention) The present invention has been made in view of the above points,
The purpose is to indirectly detect that the vehicle is at its roll limit based on the steering status and vehicle speed related to lateral acceleration, and to reduce the assist force to the steering force in accordance with the lateral acceleration. By doing this, the steering force is increased near the roll limit of the vehicle, and the steering force is corrected to correspond to the lateral force, thereby reducing the responsiveness of the steering wheel when the vehicle is equipped with a power steering device near the roll limit. The goal is to solve problems well and accurately.

(Structure of the Invention) In order to achieve the above object, the solution means of the present invention is provided with a Paro cylinder operated by pressure oil supplied from an oil pump as described above, and uses the power cylinder to apply steering force to the steering wheel. The Paro steering device configured to assist is provided with an assist force control means for controlling the assist force of the steering operation by adjusting the pressure oil supplied to the power cylinder, and also includes a vehicle speed sensor for detecting vehicle speed and a steering state of the steering wheel. The system further includes a steering sensor for detecting the roll limit of the vehicle, receives output signals from both of the sensors, and compares these sensor signals with a value indicating the roll limit of the vehicle set in advance based on the vehicle speed and steering condition to determine when the roll limit has been reached. The present invention is provided with roll discrimination means for determining the roll and issuing a command signal to the assist force control means to reduce the assist force when the vehicle reaches the roll limit.

As a result, when the roll state of the vehicle, which is indirectly detected based on the vehicle speed and the steering state, reaches near the roll limit, the assist force for the steering force is reduced and the steering force is adjusted to match the roll state of the vehicle. This is to compensate for the increase in the steering force.

(Effects of the Invention) Therefore, according to the power steering device for a vehicle of the present invention, the roll limit of the vehicle is determined based on the vehicle speed and the steering state, and when the vehicle reaches the roll limit, the steering assist is provided. Since it is designed to reduce the force, it is possible to increase the steering force near the roll limit of the vehicle and correct the steering force according to the lateral force, thereby reducing the roll limit of vehicles equipped with a power steering device. It is possible to eliminate the feeling of the steering wheel coming off in the vicinity with good responsiveness and accuracy.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the overall configuration of a power steering device for a vehicle according to an embodiment of the present invention, in which 1 is a handle, 2 is the handle 1 at one end, and a pinion shaft 3 having a pinion 3a is integrally attached to the other end. The steering shaft 4 is a rack bar having a rack 4a that meshes with the pinion 3a, and left and right front wheels 7, 7 are connected to both ends of the rack bar 4 via tie rods 5, 5 and knuckle arms 6, 6, respectively. A rack and pinion type steering mechanism is constructed in which a rack bar 4 is moved left and right by turning the handle 1 to give a steering angle to the front wheels 7, 7.

A power cylinder 8 is disposed at an intermediate position of the rack bar 4, and the power cylinder 8 is slidably inserted through the rack bar 4 as a piston rod. The pressure chambers 10 and 11 are defined by pressure chambers 10 and 11. Each pressure chamber 1
Reference numerals 0 and 11 indicate control valves 14, which are four-way switching valves such as rotary valves, which are disposed around the pinion shaft 3 via pressure oil passages 12 and 13, respectively.
The control valve 14 is connected via a pressure oil supply passage 15 to an oil pump 17 that is rotationally driven by an on-vehicle engine 16, and is also connected to a reservoir 19 via a pressure oil return passage 18. The oil passage is switched by a control valve 14 that is switched in conjunction with the steering operation, and the pressure oil supplied from the oil pump 17 is passed through the pressure oil supply passage 15, the control valve 14, and the pressure oil passages 12, 13 to provide power. The pressure oil in the other pressure chambers 11, 10 is introduced into one pressure chamber 10, 11 of the cylinder 8, and is returned to the reservoir 19 via the pressure oil passages 13, 12, the control valve 14, and the pressure oil return passage 18. By doing so, the power cylinder 8 is operated, and the operation of the power cylinder 8 is configured to assist the steering force of the steering wheel.

Further, an electromagnetic throttle valve 20 that throttles the pressure oil supply passage 15 is disposed in the middle of the pressure oil supply passage 15, and the throttle valve 20 includes a valve body 20a that throttles the pressure oil supply passage 15 to open and close it; a spring 20b that biases the valve body 20a to increase the aperture opening;
The valve body 20a resists the biasing force of the spring 20b.
The pressure oil supply passage 15
This changes the hydraulic pressure between the upstream and downstream sides of the throttle valve 20. The pressure oil supply passage 15 also includes a bypass passage 21 that bypasses the throttle valve 20.
are branched and connected, and a relief valve 22 is disposed in the middle of the bypass passage 21, and the relief valve 22
When the pressure oil pressure in the pressure oil supply passage 15 on the upstream side of the throttle valve 20 increases, the opening degree of the valve body 22a increases and the pressure oil from the oil pump 17 is transferred to the reservoir 19.
It provides relief. Therefore, the throttle valve 20 and the relief valve 22 adjust the amount of pressure oil supplied from the oil pump 17 to the power cylinder 8 to control the assist force that assists the steering force, and the throttle valve 20 solenoid 2
When the energization time to 0c is short, the valve body 20a
By increasing the opening degree of the throttle, the amount of pressure oil supplied to the power cylinder 8 is kept large and the assist force is increased. On the other hand, as the time when the solenoid 20c is energized becomes longer, the opening degree of the throttle valve body 20a becomes smaller. As a result, the assist force control means 23 is configured to reduce the amount of pressure oil supplied to the power cylinder 8 to reduce the assist force.

Furthermore, to explain the control system for controlling the energization time to the solenoid 20c of the throttle valve 20, 24 is the running speed v (vehicle speed) of the vehicle.
25 is a steering angle sensor (steering sensor) attached to the pinion shaft 3 near the control valve 14 and detects the steering angle θ _H as the steering state; 26 is the vehicle speed sensor 24 and This is a control unit that receives each output signal from the steering angle sensor 25 and controls the energization time to the solenoid 20c of the throttle valve 20. As shown in detail in FIG. 2, the control unit 26 includes an f-v converter 27 that converts the output signal (pulse signal) of the vehicle speed sensor 24 into a voltage;
The output signal of the f-v converter 27 is sent to the steering angle sensor 25.
an arithmetic circuit 28 that calculates a quantity indicating the roll state of the vehicle during turning, such as lateral acceleration, by multiplying the output signal of the
The output signal of the arithmetic circuit 28 is compared with a reference voltage value k as a roll limit value indicating the roll limit of the vehicle preset based on the vehicle speed v and the steering angle θ _H , and the output signal of the arithmetic circuit 28 is determined. is the reference voltage value k
A first comparator circuit 29 outputs a negative deviation signal corresponding to the difference (v-θ _H -k) when the difference is higher than .
and a triangular wave generating circuit 30 that generates a triangular wave signal of a predetermined period, and a sum signal obtained by adding the negative deviation signal of the first comparator circuit 29 to the output signal of the triangular wave generating circuit 30 is outputted from the f-v converter 27. A second circuit that compares and discriminates the signal and outputs an ON signal when the output signal of the f-v converter 27 is higher than the addition signal.
The comparison circuit 31 and the solenoid 20c of the throttle valve 20 when a signal is output from the second comparison circuit 31.
The amount of pressure oil supplied to the power cylinder 8, which is determined by the opening degree of the throttle valve 20, that is, the assist force that assists the steering force, is controlled by the vehicle speed as shown in FIG. When the total roll amount of the vehicle detected based on the vehicle speed v and the steering angle θ _H exceeds the roll limit as shown by the shaded area in FIG. Control is performed so that the amount of pressure oil supplied to the power cylinder 8 is reduced by the amount exceeding the roll limit, thereby reducing the assist force. Therefore, this control unit 26
receives each output signal from the vehicle speed sensor 24 and the steering angle sensor 25, compares these sensor signals with a value indicating the roll limit of the vehicle set in advance by the vehicle speed v and the steering angle _θH , and determines whether the vehicle has reached the roll limit. The assist force control means 2 determines when the roll limit has been reached and sends a command signal to reduce the assist force when the roll limit is reached.
3 constitutes a roll determining means.

In addition, in Fig. 1, 33 is the control unit 2.
6, etc., and 34 is a manually operated changeover switch for changing the assist force characteristics of the steering with respect to the vehicle speed v. As shown in FIG. Both circuits 30, 3 are connected between the triangular wave generating circuit 30 of the unit 26 and the second comparator circuit 31.
The signal level of the triangular wave signal from the triangular wave generating circuit 30 to the second comparator circuit 31 is changed by switching the changeover switch 34 to change the current conduction characteristics to the throttle valve 20. By changing , the characteristics of the steering assist force with respect to the vehicle speed v can be switched in two ways, as shown by the solid line and the two-dot chain line in FIG.

Next, to explain the operation of the above embodiment,
By the operation of the control unit 26 which receives each output signal from the vehicle speed sensor 24 and the steering angle sensor 25, the energization time to the solenoid 20c of the throttle valve 20 is controlled based on the vehicle speed v and the steering angle _θH , and the oil pump The amount of pressure oil supplied from the power cylinder 17 to the power cylinder 8, that is, the assist force that assists the steering is controlled. At this time, basically, the assist force changes according to the vehicle speed v, and is controlled so that as the vehicle speed v increases, the assist force decreases as shown in FIG. 4. That is, when the vehicle speed v is low, the
As shown in FIG. 2, the output signal of the f-v converter 27 in the control unit 26
9 and the triangular wave generating circuit 30, and the output signal of the second comparator circuit 31 has a low duty ratio as shown in FIG. By shortening the energization time, the amount of pressure oil supplied to the power cylinder 8 increases, and the assist force that assists the steering force increases. On the other hand, as the vehicle speed v increases, the time during which the output signal of the f-v converter 27 is higher than the addition signal increases, and as shown in FIG. As the time period during which the solenoid 20c of the throttle valve 20 is energized becomes longer, the amount of pressure oil supplied to the power cylinder 8 decreases, and the steering assist force decreases. As a result, at low vehicle speeds, the steering force is reduced by increasing the assist force, and at high vehicle speeds, the assist force is reduced, thereby improving the running stability of the vehicle speed.

In addition, at the same time as this basic control of the assist force is performed according to the vehicle speed v, a quantity indicating the roll state accompanying the turning movement of the vehicle is calculated, and when the vehicle exceeds the roll limit, the above-mentioned assist force is adjusted accordingly. Correction control is performed so that the value decreases. To explain the correction control of the assist force according to the roll state of the vehicle, the vehicle speed signal from the vehicle speed sensor 24 and the steering angle signal from the steering angle sensor 25 are multiplied by the calculation circuit 28, and the output of the calculation circuit 28 is The first signal
The comparator circuit 29 compares and determines a reference voltage value k indicating a roll limit set in advance. and,
When the output signal of the arithmetic circuit 28 is higher than the reference voltage value k, that is, the amount (v/
When θ _H ) corresponds to the shaded _area in FIG. The negative deviation signal output from the comparator circuit 29 and output from the first comparator circuit 29 is added to the triangular wave signal from the triangular wave generating circuit 30, so that the signal level of the triangular wave signal becomes as shown by the imaginary line in FIG. 3a. descend. For this reason, the time during which the solenoid 20c of the throttle valve 20 is energized becomes longer than in the case of the above basic control, as shown by the imaginary lines in b and c of the figure, and the amount of pressure oil supplied to the power cylinder 8 is reduced. The assist force is reduced by the amount by which the roll state quantity of the vehicle exceeds the roll limit. As a result, the steering force near the roll limit of the vehicle increases and becomes a steering force that corresponds to the lateral force applied to the vehicle, thereby eliminating the feeling of the steering wheel coming loose.

In this case, since it is determined that the vehicle has reached the roll limit based on the vehicle speed v and the steering angle θ _H , it is possible to determine whether the vehicle has reached the roll limit more quickly than in the case where the determination is made using a conventional acceleration sensor. Therefore, the increase correction of the steering force near the roll limit of the vehicle can be performed with good responsiveness.

In addition, the assist force is reduced by the amount that the vehicle roll state amount detected based on the vehicle speed v and steering angle θ _H exceeds the roll limit, so the steering force can be made to correspond to the actual vehicle roll state. Therefore, it is possible to accurately correct the steering force near the roll limit of the vehicle.

In addition, in the above embodiment, the control unit 2
Although the vehicle speed signal from the vehicle speed sensor 24 and the steering angle signal from the steering angle sensor 25 are multiplied by the vehicle speed signal from the vehicle speed sensor 24 and the steering angle signal from the steering angle sensor 25 in the arithmetic circuit 28 of No. 6, it may be changed to add both signals to simplify the roll state of the vehicle. can be determined. In this case, it is determined that the vehicle has exceeded the roll limit when the roll state amount of the vehicle is within the shaded range in FIG.

Furthermore, in the above embodiment, the assist force is controlled by changing the amount of pressure oil supplied to the power cylinder 8 by controlling the throttle opening of the throttle valve 20 according to the vehicle speed signal from the vehicle speed sensor 24. Although the case where it is applied to a vehicle speed-sensitive power cylinder device has been described, the present invention is applicable to a power steering device equipped with a control valve incorporating a hydraulic reaction force chamber, a torsion bar, etc., or which does not perform assist force control based on vehicle speed sensitivity. Of course, the present invention can also be applied to ordinary power steering devices.

Furthermore, it goes without saying that the present invention can be applied to power steering devices other than the rack and pinion type.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is an overall configuration diagram, Fig. 2 is a block diagram of the control system, and Fig. 3 is a block diagram of the control system.
The figure is an explanatory diagram showing the waveform signals at a predetermined part of the control system, Fig. 4 is an explanatory diagram showing the basic relationship between vehicle speed and steering assist force, and Fig. 5 is an explanatory diagram showing the basic relationship between vehicle speed and steering assist force, and Fig. 5 is an explanatory diagram showing the vehicle roll that should reduce the steering assist force. An explanatory diagram showing the limits, FIG. 6 is a diagram corresponding to FIG. 5 showing a modification of the roll limits. 1...handle, 2...steering shaft, 3
... Pinion shaft, 4... Rack bar, 8... Power cylinder, 14... Control valve, 17... Oil pump, 20... Throttle valve, 22... Relief valve, 23
...assist force control means, 24...vehicle speed sensor, 25
... Rudder angle sensor, 26... Control unit.

Claims (1)

[Claims] 1 A power steering device for a vehicle comprising a power cylinder operated by pressure oil supplied from an oil pump and configured to assist the steering force with the power cylinder, the power steering device comprising a power cylinder operated by pressure oil supplied to the power cylinder. Adjust and
an assist force control means for controlling an assist force for assisting the steering force; a vehicle speed sensor for detecting the running speed of the vehicle; and a steering sensor for detecting the steering state of the steering wheel; is compared with a value indicating the roll limit of the vehicle set in advance based on the traveling speed and steering condition to determine that the vehicle has reached the roll limit, and when the roll limit is reached, the above-mentioned assist command signal is sent to reduce the assist force. 1. A power steering device for a vehicle, comprising: a roll determining means that outputs power to the force controlling means.