JPH0324455Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to a vehicle steering system that separates the steering wheel from the mechanical link with the steering wheel and steers the vehicle by electrical control, and is particularly applicable to a servo system. The present invention relates to a vehicle steering system that detects an abnormality in a steering system based on generated vibrations.

(Prior Art) Japanese Patent Laid-Open No. 59-6171 discloses a vehicle steering device using a hydraulic cylinder instead of a conventional mechanical link type steering device. This is applied as a steering device for the rear wheels of a vehicle (four-wheel steering vehicle) that enables front and rear wheel steering, and uses a sensor to detect the steering angle of the front wheels, which are mechanically linked to the steering wheel. When the front wheel steering angle exceeds a predetermined value, the rear wheels are steered.The rear wheel steering angle is controlled by the hydraulic pressure in the hydraulic cylinder using a servo valve.

(Problems to be Solved by the Invention) However, when the steered wheels are servo-controlled as in the conventional example described above, no countermeasures have been taken when the operation of the hydraulic cylinder becomes abnormal.

For example, if the deviation between the steering amount of the steered wheels and the target value becomes abnormally large due to an abnormal operation of the hydraulic cylinder, the steering stability will be significantly deteriorated.

One way to avoid this situation is to determine that an abnormality has occurred when the deviation between the detected value of the steering amount and the target value exceeds a certain value, and, for example, stop turning the steered wheels and return them to the neutral position. It is conceivable to provide a fail-safe device to restore the condition.

However, after this abnormal occurrence,
If such countermeasures are taken, it is inevitable that the vehicle behavior will become unstable at the time the abnormality occurs.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a piston rod connected to the steering wheel, which steers the steering wheel using hydraulic pressure, and when there is no hydraulic pressure supplied. A hydraulic steering actuator is equipped with a spring that holds the piston rod in a neutral position, and a spool displacement amount is controlled by a control current, and the hydraulic pressure supplied to the hydraulic steering actuator is controlled. a servo valve that stops supplying hydraulic pressure to the hydraulic steering actuator when the current value is zero, and a deviation between a target value signal of the steering amount of the steered wheels and a detected value signal of the steering amount. and a servo amplifier that supplies a control current corresponding to the servo valve to the servo valve, and the steered wheels are servo-controlled by these.

In addition to the above configuration, the present invention also includes a vibration sensor that detects vibrations of the movable part of the hydraulic steering actuator, and a vibration sensor that detects whether the amount of vibration detected by the vibration sensor is greater than or equal to a predetermined value. The vibration determining means includes a vibration determining means for determining, and a current cutting means for cutting off output of the control current when the vibration determining means determines that the amount of vibration is equal to or greater than a predetermined value.

(Function) When an abnormality occurs in the operation of the hydraulic steering actuator, the vibration of the movable part increases immediately before the abnormality occurs.

Therefore, when the vibration of the movable part of the hydraulic steering actuator is detected by the vibration sensor, and the amount of vibration exceeds a predetermined value, it is determined that this is a sign of abnormal operation of the hydraulic steering actuator. The control current is prohibited from being output from the servo amplifier.

As a result, the supply of hydraulic pressure from the servo valve to the hydraulic steering actuator is stopped, and the piston rod to the hydraulic steering actuator is held at the neutral position.

Therefore, before the operation of the hydraulic steering actuator becomes abnormal and the vehicle behavior becomes unstable, steering can be prohibited and safe driving can be achieved.

(Example) The configuration of an embodiment of the present invention is shown in FIG.

In this embodiment, the hydraulic cylinder 15 is used as a steering actuator, and the steered wheels 1 are thereby steered. Both ends of the piston 17 of the hydraulic cylinder 15 are connected to the side rods 1 of the left and right steering wheels.
9, the displacement of the piston 17 is transmitted to the knuckle arm 16 via the side rod 19, and the steered wheel 1 is steered.

Hydraulic cylinder 15 is controlled by servo valve 11, and servo valve 11 is controlled by servo amplifier 12.

The specific structure of the servo valve 11 is as shown in FIG.

In the figure, 51 is a substantially cylindrical valve body, and 52 is a substantially cylindrical sleeve press-fitted into the valve body 51.
, the side cover 53 is fitted to the right end in the figure,
A hollow case 54 is fitted on the left end.

The valve body 51 is formed with a drain port 58 connected to the reservoir 55 and two outlet ports 59a and 59b, each connected to the hydraulic cylinder 15.

The sleeve 52 has an annular groove 20 communicating with an inlet port 57 and an annular groove 20 communicating with a drain port 58.
Two annular grooves 21a, 21b and two annular grooves 30a, 30b communicating with each outlet port 59a, 59b are formed. In addition, 24 is a spool 2 which is screwed onto the side cover 53 and will be described later.
The first stopper 25 that restricts the maximum displacement in the right direction in the figure 6 is a lock nut that is screwed onto the first stopper 24 to fasten the first stopper 24 to the side cover 53.

Inside the sleeve 52 is a spool (movable valve body) 2.
6 is slidably inserted. The spool 26 is formed with two protrusions 27a, 27b corresponding to the annular grooves 30a, 30b of the spool 52,
Three grooves 28, 2 are formed by the protrusions 27a, 27b.
9a and 29b are set.

These grooves 28, 29a, 29b selectively communicate the annular grooves 30a, 30b with the annular groove 20 or the annular grooves 21a, 21b according to the displacement of the spool 26, and connect the respective outlet ports 59a, 59.
b is communicated with an inlet port 57 or a drain port 58. Further, a bobbin 31 having a thin cylindrical portion 31a is integrally fitted to the left end of the spool 26 in the drawing.

The bobbin 31 is housed in a case 54 so as to be movable in the left-right direction in the figure, and a conductive wire is wound around the outer periphery of a thin cylindrical portion 31a to form an air-core coil 32. That is, this bobbin 31 has an air-core coil 32 integrally attached to its left end in the figure. This air-core coil 32 is supplied with a control current from the servo amplifier 12 .

43 is a first seal provided between the right end of the spool 26 in the figure and the side cover 53 to prevent fluid leakage; similarly, 44 is a seal provided between the bobbin 31 and the case 54 on the left side of the spool 26 in the figure. A second seal is provided to prevent fluid leakage.

A substantially annular permanent magnet 33 is fixed in the case 54, and a first yoke 34 and a second yoke 35 are provided adjacent to the permanent magnet 33 on the left and right sides of the permanent magnet 33, respectively. It is being 1st
The yoke 34 has a substantially annular shape, and its outer peripheral surface is fixed to the inner surface of the case 54, and the air-core coil 32 is loosely inserted into the hole at a small distance. Second
The yoke 35 has a shaft portion 35a that is loosely inserted into the thin cylindrical portion 31a at a small distance.

These permanent magnets 33, the first yoke 34, and the second yoke 35 constitute a magnetic circuit 36, and the air-core coil 32 is located within the magnetic circuit 36. Note that the air-core coil 32, permanent magnet 33, first yoke 34, and second yoke 35 constitute a linear motor 45 that drives the spool 26.

Further, the second yoke 35 is formed with a through hole that penetrates in the left-right direction in the figure, and the case 54 is screwed into the through hole so that the case 54 can be screwed into the second yoke 35 by the lock nut 38.
A hollow spring holder 37 fixed to 4
is inserted. Inside the spring holder 37, there is a second
A stopper 39 is screwed into the spring holder 37 by a lock nut 40 so that it can be fastened.

The second stopper 39 restricts the maximum displacement of the spool 26 in the left direction in the figure. In addition, 41 is bobbin 3
1 and the spring holder 37, and 42 is a second central spring that is compressed between the case 54 and the bobbin 31. Spring 42 biases spool 26 to a neutral position (the position shown).

Furthermore, notches 46a and 46b are formed in the protrusions 27a and 27b, respectively. These notches 46a, 46b connect the two outlet ports 59 when the spool 26 is in the neutral position.
a, 59b to communicate with the drain port 58.

That is, when the control current applied to the air-core coil 32 becomes zero, the spool 26 returns to the neutral position and drains the hydraulic pressure applied to the hydraulic cylinder 15 via the notches 46a and 46b.

A centering spring 18 is installed inside the hydraulic cylinder 15 and always urges the piston 17 toward the neutral position. The hydraulic pressure that had been displacing the piston 17 against the force disappears, and the piston 17 is returned to the neutral position.

Note that the oil pump 56 is driven by the motor 2 which uses the battery 3 as a power source, as shown in FIG. 8 is a relief valve for keeping the working oil pressure at a constant pressure, 9 is an accumulator, and 10 is an oil filter.

The servo amplifier 12 receives a steering amount target value signal e ₀ of the steered wheel 1 supplied from the control circuit 5 and a detection signal of the displacement amount of the piston 17 of the hydraulic cylinder 15 detected by the displacement sensor 13 (this is the steering amount target value signal e 0 of the steered wheel 1). A signal obtained by amplifying S ₂ (corresponding to the steering amount of 1) by amplifier 14
A current I proportional to the deviation from e _i is outputted to control the servo valve 11.

The control circuit 5 receives a detection signal θ _s of the steering angle of the steering wheel 62 detected by the steering wheel angle sensor 4, a detection signal V of the vehicle speed detected by the vehicle speed sensor 6, and a yaw rate detected by the yaw rate sensor 7. A steering amount target value of the steered wheel 1 is determined based on the detection signal φ, and a voltage signal corresponding to this steering amount target value is output as a steering amount target value signal e _p .

The vibration discrimination circuit 61 inputs a detection signal S ₁ of the amount of vibration of the piston 17 detected by a vibration sensor 60 attached to the piston 17 of the hydraulic cylinder 15, and based on this detection signal S ₁ , detects the amount of vibration of the piston 17.
Determine the magnitude of the amount of vibration. This vibration discrimination circuit 6
The specific configuration of 1 is as shown in FIG.

The output signal S ₁ of the vibration sensor 60 is transmitted to the amplifier circuit 61
1, and then passes through a filter circuit 612 that filters the oscillation component (for example, a high-pass filter with a cutoff frequency of 500 Hz is used to extract the oscillation component that is mostly composed of components of 500 Hz or higher).
It is input to a half-wave rectifier circuit 613. The signal L after being rectified by this half-wave rectifier circuit 613 is smoothed by an averaging circuit 614 and input to a comparison circuit 616. Note that the vibration sensor may be either an acceleration sensor or an amplitude detection sensor.

The comparison circuit 616 compares the levels of the output signal M of the averaging circuit 614 and the reference value signal _VTH provided from the reference value generation circuit 615, and determines that the level of the output signal M exceeds the level of the reference value signal _VTH . Outputs a high level signal when

For example, as shown in FIG. 4, between time points _t1 and _t2 , large vibrations occur in the spool 17 of the hydraulic cylinder 15 due to vibrations of the vehicle body, and this vibration is detected by the vibration sensor 60. , filter circuit 6
Suppose that the vibration amplitude of the output signal K of No. 12 becomes large.

At this time, the level of the signal M after half-wave rectification and averaging of the signal K exceeds the level of the reference signal _VTH , so that the output N of the comparison circuit 616 remains at a high level during the period _t1 to _t2 . becomes the output.

The servo valve 11 has a flow rate proportional to the magnitude of the control current I supplied from the servo amplifier 12 (however, it is affected by the load on the hydraulic cylinder 15).
of hydraulic oil is supplied to the hydraulic cylinder 15.

The control current I has a larger current value as the deviation between the steering amount target value signal e ₀ and the detection signal e _i of the displacement amount of the hydraulic piston becomes larger.

For example, if the control current I changes as shown in FIG. 5a, the spool 26 of the servo valve 11
is displaced in proportion to the control current I, as shown in FIG.

When the displacement X of the spool 26 exceeds a certain value X ₀ (overlap amount), one outlet port 59 has an opening area corresponding to the displacement X of the spool 26.
b communicates with the inlet port 57, and the other outlet port 59a communicates with the drain port 58. When the right end of the spool 26 in FIG. 2 comes into contact with the first stopper 24 and the spool displacement X reaches the maximum X _nax , the opening area becomes the maximum.

Moreover, when the control current I flows in the opposite direction,
Spool displacement X is constant value - X ₀ (overlap amount)
, one outlet port 59b communicates with the drain port 58, contrary to the above case.
The other outlet port 59a communicates with the inlet port 57, and the steered wheel 1 is steered in the opposite direction.

When the steering amount target value signal e ₀ and the detection signal e _i of the piston displacement amount of the hydraulic cylinder match, the displacement X of the spool 26 of the servo valve 11 becomes X=O, and the outlet ports 59a and 59b are closed. As a result, the position of the piston 17 of the hydraulic cylinder 15 does not change.

A specific circuit configuration of the servo amplifier 12 is shown in FIG.

The operational amplifier OP ₁ amplifies the deviation between the steering amount target value signal e ₀ inputted from the control circuit 5 and the displacement detection signal e _i of the piston 17 inputted from the displacement sensor 13 via the amplifier 14 .

The output e _r of the operational amplifier OP ₁ becomes a target value signal e _r of the current flowing through the air core coil 32 of the servo valve 11 .
The operational amplifier OP ₂ is a comparator that determines whether the current target value signal e _r is positive or negative. When e _r is a positive signal, it outputs a high level signal and turns on the transistor T _r4 via the amplifier A ₂ . state. Furthermore, when e _r is negative, operational amplifier OP ₂ outputs a low level signal, turning on transistor T _r2 via inverter I ₁ and amplifier A ₁ .

The operational amplifier _OP3 is a voltage follower for current control, and is activated when the signal e _r is positive. That is, input the current target value signal e _r and the terminal voltage signal _{e c} of the current detection resistor R ₁ for detecting the current value flowing through the air-core coil 32 (e _c is the terminal voltage signal e c of the amplifier A ₃
The base current of the transistor Tr3 is controlled so that the levels of both signals e _r and e _c match. Therefore, the control current I flowing through the air-core coil 32 is controlled in proportion to the current target value signal e _r .

Similarly, op amp OP ₄ is a voltage follower that operates when signal e _r is negative, and when signal e _r
Transistor Tr5 so that the levels of e and _c match.
control the base current.

A relay Re for passing/cutting off the power is provided on the power line of the transistors Tr2 and _Tr4 , and this relay Re has a contact when the output N of the vibration discrimination circuit 61 is at a high level. It is opened to cut off the power.

Next, the operation of the servo amplifier 12 when a large mechanical vibration occurs in the hydraulic cylinder 15 will be described as a sign that a failure occurs in the servo system and an abnormality occurs in the operation of the hydraulic cylinder 15.

As shown in FIG. 4, during period T _b , large mechanical vibrations occur in the hydraulic cylinder 15 and a vibration component appears in the detection signal S ₁ of the vibration sensor 60. During this period T _b , the vibration Discrimination circuit 61
output signal N becomes high level, and hydraulic cylinder 1
5, vibration of a certain value or more occurs, and the hydraulic cylinder 15
It is determined that an operational abnormality has occurred.

As the output N becomes high level, the contacts of the relay Re are opened in the servo amplifier 11, and the power is cut off.

As a result, the current value of the control current I given to the servo valve 11 becomes zero, and as described above,
The supply of hydraulic pressure to the hydraulic cylinder 15 is stopped, and the steered wheels 1 are returned to the neutral position (state where the steering angle is 0°) and maintained in this state.

Therefore, by stopping the steering of the steered wheels 1 and holding them at the neutral position, in order to prevent disturbances in the vehicle body behavior due to abnormal operation of the hydraulic cylinder 15, It is possible to drive safely.

(Effects of the Invention) As explained in detail above, the present invention steers the steered wheels by a servo mechanism using a hydraulic steering actuator, and uses a vibration sensor to steer the steering wheel by a servo mechanism using a hydraulic steering actuator. By detecting the vibration of the movable part and holding the steering wheel in the neutral position when the amount of vibration exceeds a predetermined value, abnormal operation of the hydraulic steering actuator can be detected before it occurs, and the steering wheel can be adjusted. It becomes possible to prohibit wheel steering and create a state in which safe driving can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a sectional view showing the structure of the servo valve in Fig. 1, and Fig. 3 is a block diagram showing the structure of the vibration discrimination circuit in Fig. 1. , Fig. 4 is a waveform diagram showing an example of changes in input/output signals in the vibration discrimination circuit, and Fig. 5 shows the control current I given to the servo valve in Fig. 1 and the amount of displacement of the spool in Fig. 2. FIG. 6 is a circuit diagram showing the configuration of the servo amplifier in FIG. 1. DESCRIPTION OF SYMBOLS 1... Steering wheel, 5... Control circuit, 11... Servo valve, 12... Servo amplifier, 15... Hydraulic cylinder (hydraulic steering actuator), 17... Movable part, 18... Centering spring, 46
a, 46b...notch, 60...vibration sensor, 6
1... Vibration discrimination circuit (vibration amount discrimination means), Re...
Relay (current interrupting means), I... Control current.

Claims (1)

[Scope of Claim for Utility Model Registration] A hydraulic type equipped with a piston rod connected to a steering wheel, which steers the steering wheel using hydraulic pressure, and has an internal spring that holds the piston rod in a neutral position when no hydraulic pressure is supplied. The amount of spool displacement is controlled by the steering actuator and control current,
a servo valve that controls the hydraulic pressure supplied to the hydraulic steering actuator and stops supplying the hydraulic pressure to the hydraulic steering actuator when a control current value is zero; a servo amplifier that supplies the servo valve with a control current corresponding to the deviation between the target value signal of the steering amount and the detected value signal of the steering amount; and a vibration sensor that detects vibrations of the movable part of the hydraulic steering actuator. and a vibration amount determining means for determining whether the amount of vibration detected by the vibration sensor is greater than or equal to a predetermined value; A vehicle steering device comprising: current cutoff means for cutting off output of the control current when the determination is made.