JPS62216867A - Four-wheel steering device for car - Google Patents

Abstract

PURPOSE:To enhance the safety in steering by switching over to two-wheel steering system when any abnormality is generated in the hydraulic line for the rear wheel steering mechanism. CONSTITUTION:A hydraulic fail-safe device includes an engine oil-pressure sensor 43, which is to sense that the engine is in operation, and a sensor 44 which senses the oil pressure in an oil-hydraulic device 41 for a rear wheel steering 7. When any failure with oil pressure drop has occurred in said oil- hydraulic device 41 consisting of a power cylinder 15, a control valve 18 and an oil pressure pump 22, the rear wheel steering 7 is returned to the neutral condition. Then switching is made into two-wheel steering condition.

Description

[Detailed description of the invention] [Field of application of production] The present invention improves the stability and safety of steering when an abnormality occurs in the hydraulic system of The present invention relates to a four-wheel steering system for a vehicle with a raised height.

[Prior art]

Conventionally, as a four-wheel steering system for a vehicle such as an automobile, for example, as disclosed in Japanese Patent Laid-Open No. 59-128054, the steering angle of the rear wheels is adjusted in accordance with the traveling speed of the vehicle and the steering angle of the front wheels. Is it electrically driven by a pulse motor, etc.? It is known that the steering wheel is controlled by an IU actuator, and the steering operation of each actuator is assisted by a hydraulic system having a double-acting hydraulic cylinder.

In such a four-wheel steering system for a vehicle, it is necessary to ensure safety against failure of the electric system including the actuator and a control means for controlling the actuator, and the hydraulic system.

The failures of the hydraulic system can be broadly classified into failures of the pressure oil source, that is, failures of the hydraulic pump or the motor that drives it, failures of piping, and failures of the hydraulic actuators. Malfunctions of the pressure oil source include mechanical locking of the hydraulic pump or the motor that drives it, motor stoppage or irregular rotation due to wire breakage, short circuit, poor wiring, insufficient pressure oil flow, etc. Failures include leaks, clogged piping, and falling off, and failures of hydraulic actuators include mechanical locking of the hydraulic actuator, leaks, etc. In any of these failures, abnormalities in the hydraulic pressure, i.e., hydraulic This can lead to loss of energy, pulsation, and decline.

Conventionally, in order to ensure safety against failures in the electrical system, a pair of springs have been provided that return the screws of the hydraulic cylinder to the neutral position. System failure detection means, and when an electrical system failure is detected by this electrical system failure detection means, the hydraulic pressure of the hydraulic circuit is removed, and the pressure receiving chambers on both sides of the piston are communicated with each other, so that a differential pressure acts on both sides. A control means is provided to eliminate the problem.

The vehicle's four-wheel steering system is designed to ensure safety against electrical system failures, so if an electrical system failure occurs,
By removing the hydraulic pressure from the hydraulic circuit, or by communicating the pressure receiving chambers on both sides of the piston to eliminate the differential pressure acting on both sides, the piston returns to the neutral position or the maximum position of the same phase due to the action of the spring. and held in that position.

For example, when the piston returns to the neutral position, the steering angle of the rear wheels becomes 0, and as a result, the steering of the vehicle depends only on the two front wheels.

According to the four-wheel steering system for a vehicle configured in this way, a certain degree of safety can be ensured even if the hydraulic system fails during driving. For example, when hydraulic pressure is lost due to a failure of the hydraulic system, the piston is returned to the neutral position by the pair of springs, and the rear wheels are held at the neutral position, resulting in a two-wheel steering state.

However, when the piston of the hydraulic cylinder is held in the neutral position by the force of the spring, if the oil pressure is restored for some reason after the hydraulic cylinder's screw is in the neutral position, Since the rear wheels are suddenly steered by hydraulic pressure to correspond to the front wheel steering angle and traveling speed when the hydraulic pressure is restored, there is room for improvement in terms of steering stability.

[Object of the Invention] The present invention has been made in consideration of the above-mentioned circumstances, and is intended to fix the actuator in a predetermined position and to control the front wheel steering mechanism after an abnormality occurs in the hydraulic system of the rear wheel steering mechanism. The object of the present invention is to provide a four-wheel steering system for a vehicle that improves steering stability and safety when an abnormality occurs in the hydraulic system of the rear wheel steering mechanism by switching to a wheel steering system. .

[Structure of the invention]

In order to achieve the above object, a four-wheel steering system for a vehicle according to the present invention is provided for a vehicle equipped with an actuator that controls the steering angle of a rear wheel steering mechanism, and a hydraulic system that assists the steering operation of this actuator. In the four-wheel steering system, the operating state detecting means detects that the engine is rotating, the oil pressure detecting means detects the oil pressure of the hydraulic system, and the oil pressure is determined by the outputs of the operating state detecting means and the oil pressure detecting means. While an abnormality determining means is provided for determining whether or not there is an abnormality in the device, the actuator is fixed at a predetermined position after the abnormality determining means determines that there is an abnormality. ff
One means is provided.

When the operating state detection means detects that the engine is being operated in a predetermined state, if the oil pressure detection means detects a hydraulic abnormality such as loss of oil pressure or abnormal pressure reduction, the abnormality determination means determines that there is an abnormality. After this determination, the actuator is fixed at a predetermined position by the control means, so even if the oil pressure is restored after the abnormality determination, the steering angle of the rear wheels is fixed at the predetermined position by the actuator, and the predetermined steering characteristics are maintained. is maintained.

Note that it is preferable that the fixation of the actuator to a predetermined position be released by turning off all power when the engine is stopped or turning on the power when starting the next engine.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 3.

The front wheel steering device 1 is configured to transmit the rotation of the steering wheel 3 to the left and right front wheels 1.OMEGA.12 via a rack and pinion mechanism 4, left and right tie rods 5, and knuckle arms 6. The rear wheel steering device 7 includes a rear wheel steering rod 9 slidably supported on the vehicle body, a pair of left and right tie rods 10, and a pair of left and right knuckle arms in order to steer the left and right rear wheels 8 in coordination with each other. 11
It is equipped with A rack (not shown) is formed on the rear wheel steering rod 9, and a binion 13 formed on the pinion shaft 12 is meshed with this rack.
is configured. The rear wheel steering rod 9 has a piston 15 of a power cylinder 15 which is a double-acting hydraulic cylinder.
a is fixed, and the cylinder of this power cylinder 15 is fixed to the vehicle body. Each pressure oil chamber 15b of this power cylinder 15 is connected to a control valve 18 disposed around the pinion shaft 12 via a pressure oil passage 16.17.
It is connected to. The control valve 18 is connected to, for example, a hydraulic pump 22 driven by an electric motor 21T, via a pressure oil supply passage 19 and a return oil passage 20. The call valve 18 operates to control both pressure chambers 1.5 of the power cylinder 15 in response to the rotation of the pinion shaft 12 in order to control the rear wheel steering device 70 assist 1-force and its direction. One pressure oil chamber 15 of b
b is selected and connected to the pressure oil supply passage 19, the other pressure oil chamber 15b is connected to the return oil passage 20, and the piston 1
5a and rear wheel drying helm port, and 9 is connected to one of the pressure oil chambers 15.
It is configured to be driven from the b side to the other pressure oil chamber 15b side. The pinion shaft 12, a pair of beher gears 23
- Connected via 24 to a pulse motor 25 as an actuator that controls the steering angle of the rear wheel steering device 7, and the pulse motor 25 rotates the pinion shaft 12 in either forward or reverse direction to rotate the power cylinder. 15
The rear wheel steering rod 9 is moved while being assisted by the rear wheel steering rod 9 to steer the rear wheel 8 left and right.

In order to control the steering angle of the rear wheel steering device 7 in accordance with the steering angle of the front wheel steering device 1 and the traveling speed, a front wheel steering angle sensor 26 detects the steering angle of the front wheels 2.
A vehicle speed sensor 27 that detects the vehicle speed, and a controller 28 that receives the outputs of these sensors and controls the electric motor 21 are provided. As shown in FIG. 1, this controller 28 has a characteristic storage section 29 that stores preset steering angle characteristics (characteristics of the rear wheel steering angle relative to the front wheel steering angle).
and a target steering angle calculation unit 30 that compares the output signals of the front wheel steering angle sensor 26 and the vehicle speed sensor 27 with the memory of the characteristic storage unit 29 to calculate a target steering angle in that state;
It has a pulse generator 31 that generates a pulse number signal corresponding to the calculation result, and a driver 32 that drives the pulse motor 25 in response to the pulse signal of the pulse generator 31. Further, a battery 33 is mounted as a power source for driving the controller 28, electric morph 21, and pulse motor 25. Furthermore, the four-wheel steering system of this vehicle is equipped with a rear-wheel steering system 7 when a failure such as a short circuit or disconnection occurs in a circuit component related to four-wheel steering, including the drive power supply, in the electrical system of this vehicle. An electrical fail-safe device 34 is provided for returning the vehicle to the neutral position and switching to a two-wheel + = rudder state using the front wheels. This electrical fail-safe device 34 is configured to change the switching speed from four-wheel steering to two-wheel steering depending on the nature of the failure. That is, the pulse motor 25 is driven to relatively control the rear wheel steering device 7 in order to provide a stability window for the steering G in the event of a failure while driving, and to prevent an inexperienced driver from making a sudden dangerous steering operation. There is a case where the steering device 7 is returned to the neutral position slowly (slow return mode) and a case where the steering device 7 is returned to the neutral position further than this (rapid return mode).
8, the rear wheel steering device 7 is returned to neutral based on the output of a failure detection means such as a battery voltage sensor (not shown) or an alternator output horn voltage sensor (not shown).
A mote determination unit 35 is provided that determines the mode and outputs a slow return command or a rapid return command in accordance with the determination result. Further, the controller 1-roller 28 includes a neutral return command section 36 which sets the target steering angle of the 1" target steering angle calculation section 30 to Oo in response to the slow speed return command. Furthermore, the oil chamber 15b of the power cylinder 15 is connected,
It is inserted into a bypass oil passage 38 with a normally closed solenoid valve 37 interposed therebetween and into both main oil chambers 15b,
Spring 3 for returning the piston 15a to the neutral position
A driver 40 is provided in the controller 28 to open the solenoid valve 37 in response to the quick return command.

Now, the four-wheel steering system of this vehicle includes the power cylinder 15, pressure oil passages 16 and 17, control valve 18,
When a failure occurs in the hydraulic system 41 consisting of the pressure oil supply passage 19, the return oil passage 20, and the hydraulic pump 22, such as a drop in oil pressure or loss of oil pressure due to a leak, etc., the rear wheel steering device 7 is returned to the neutral state, and the front wheel steering device 7 is returned to the neutral state. A hydraulic failsafe device 42 is provided for switching to a two-wheel steering state. This hydraulic system fail-safe device 42 has an engine oil pressure sensor 13 as an operating state detection means for detecting that the engine is rotating, and a steering oil field that detects the oil pressure of the hydraulic device 41 of the rear wheel steering device 7. It has Sen IJ'44. The engine oil pressure sensor 43 detects the lubricating oil pressure of the engine corresponding to the engine rotation speed, and outputs rotation detection numbers 1 and 9 consisting of, for example, a high level signal when it detects that the lubricating oil pressure is equal to or higher than a predetermined value. configured to do so. Also 1,
”2 Steering oil pressure sensor 44 is 1. It is configured to detect the oil pressure in the pressure oil supply passage 19 of the hydraulic device 41, and output a low pressure detection signal consisting of, for example, a low level signal when this oil pressure falls below a predetermined value. Further, the hydraulic fail-safe device 42 inputs the outputs of the engine oil pressure sensor 43 and the steering oil pressure sensor IJ-44 to determine whether there is any abnormality, and when it determines that there is an abnormality, it continuously detects the abnormality. It has an abnormality detection section 45 that outputs a signal.

This abnormality detection signal is transmitted to the electrical fail-safe device 3.
The mode determining section 35, which is common to the mode determining section 4, is manually operated to start the mode determining section 35. Further, this hydraulic fail-safe device 42 includes a neutral return command section 36, a solenoid valve 37, a bypass oil passage 3, and a solenoid valve 37 of the electrical fail-safe device 34.
8 and shares a spring 39 and a driver 40. As shown in FIG. 3, the abnormality detection section 45 has a front-stage AND circuit 48 which inputs the output of the engine oil pressure sensor 43 and inputs the ON signal of the starter motor circuit 46 via an inverter (reversing circuit) 47. , an exclusive logical OR circuit 49 that inputs the output of this pre-stage AND circuit 48 and the output of the steering oil pressure sensor 44, another inverter 50 that inverts the output of the steering oil pressure sensor 44, and the output of this inverter 50. a post-AND circuit 51 inputting the output of the exclusive OR circuit 49;
It consists of a latch circuit 52 that latches the output of the rear-stage AND circuit 51, and a seven-node circuit 53 that forms a reset I- signal of the latch circuit 52 from the ON signal of the cell motor circuit 46. This reset circuit 53 includes a capacitor 5
4 and a diode 55 for preventing backflow.

Note that the steering angle characteristics stored in the second characteristic storage unit 29 are such that, for example, at low vehicle speeds, as the front wheel steering angle increases, the rear wheel steering angles are in the same phase (the front and rear wheels are steered in the same direction). state) to reversed 1'l (a state in which the front and rear wheels are steered in opposite directions), and at high vehicle speeds, as the front wheel steering angle increases, the rear wheel steering angle increases in the same phase. The ratio of the steering angle of the front wheels to the steering angle of the rear wheels is changed so as to generate a rotation angle and a yaw rate depending on the driving condition of the vehicle.

In the above configuration, while the engine is operating, the engine oil pressure sensor 43 outputs a rotation detection signal consisting of a high level signal, and since the starter motor circuit 46 is off, the inverted signal is high. level. As a result, while the engine is operating, the output of the preceding stage AND circuit 48 is at a high level. If hair occurs in the above-mentioned hydraulic system while this engine is operating, the oil pressure in the pressure oil supply passage 19 decreases or loses ff15, and falls below the predetermined value. Therefore, the steering oil pressure sensor 44 outputs a low pressure detection signal consisting of a low level signal. Therefore, the output of the exclusive OR circuit 49 becomes a high level signal, and the output of the subsequent AND circuit 51 which manually outputs this high level signal and the high level signal obtained by inverting the output of the steering oil pressure sensor 44 using an inverter. becomes high level. This high level signal is latched by the latch circuit 52 and output as an abnormal signal. This abnormal signal is
This abnormality detection signal is transmitted to the electrical fail-safe device 34.
is input to the common mode determination unit 35, and the mode determination unit 3
Start 5. The mode determination unit 35 issues a quick return command to the driver 40 in consideration of the fact that the oil pressure is unstable or lost, and also issues a quick return command to the neutral return command unit 36.
A slow speed return JiS command is output.

The solenoid valve 37 is opened by the driver 40 inputting the quick return signal, and the power cylinder 15 is opened.
The repressurization oil chamber 15b is connected to the bus 1' bus oil passage 38, and the pressure difference in the repressurization oil chamber 15b is eliminated.
5a is returned to the neutral force position by the spring 39. As a result, the rear wheel steering wheel 7 is returned to the neutral position.

In addition, the neutral return command unit 36 to which the slow speed return command was inputted causes the 1st! The target steering angle of the A steering angle calculating section 30 is set to 0°, and the -8 pulse motor 25 is fixed at the neutral position. Furthermore, if the oil pressure of the hydraulic system 4I recovers to the above-mentioned predetermined value or more for some reason after a failure occurs, the output of the steering oil pressure sensor l+4 becomes a high level signal, and the exclusive logic OR circuit 49 The output of will be a low value,
The output of the subsequent AND circuit also becomes a low value. However, since the high level signal is already latched in the launch circuit 52, the output of the latch circuit 52 is maintained at a high level, the piston 15a is maintained in the neutral position by the spring 39, and the pulse motor 25 is in the neutral position. This ensures that the rear wheel steering device 7 is held in the neutral position. In this way, after the rear wheel steering device 7 is held in the neutral position due to the occurrence of a failure, when the engine is temporarily stopped and then restarted using the starter motor, the starter motor circuit 46 is turned on, so the latch The circuit 52 is reset, the solenoid valve 37 is closed, and the target turning angle calculating section 30 calculates the target turning angle in that state by comparing it with the memory in the characteristic record 10 section 29.

In the above embodiment, the engine oil pressure sensor 43 is used as the operating state detection means for detecting that the engine is rotating, but instead of the engine oil pressure sensor 43, a voltage for detecting the alternator output voltage is used. It is possible to use a sensor, an engine rotation detector that detects the engine rotation speed, and the like. In addition, the latch circuit 5
0, a 4α element refreshed by the ON signal of the cell motor circuit 46 may be used, and in place of the latch circuit 50, the output of the exclusive OR circuit 49 may be manually operated as a 7 soto signal. However, an R-S flip-flop circuit which inputs the ON signal of the starter motor circuit 46 as the reset signal 1- may be used.

[Embodiment 2] FIG. 4 is a logic circuit diagram of an abnormality detecting section 56 according to another embodiment of the present invention. is input, and outputs a time-up signal after a predetermined period of time has elapsed from the start of output of this on-signal, and a memory element 59 that is refreshed by the on-signal of the cell motor circuit 46 and stores the time-up signal. ing. This operating state detection means is an AND circuit 6
0, and the other input end of this AND circuit 60 is connected to a steering oil pressure sensor 44 via an inverter 61.

The output of this AND circuit 59 is the cell motor circuit 46
It is output as an abnormal signal via the launch circuit 52 which is reset by the ON signal.

In this embodiment, when an engine starting operation is performed by the starter motor, a time-up signal is output from the timer circuit 58 after a predetermined period of time has elapsed, and is recorded in the memory element 59. It is determined that the engine is rotating. .

Therefore, for example, when the engine oil pressure sensor 43, alternator output sensor, etc. are used as the operating state detection means,
While there is a risk that the output may fall to a low level during deceleration, etc., in this embodiment, the oil pressure of the hydraulic system 41 remains at the predetermined value regardless of the actual operating state of the engine once the starting operation has been executed. The output of the AND circuit 60 becomes high level or low level depending on whether or not the value is lower than . When the oil pressure of the hydraulic device 41 falls below a predetermined value and the output of the AND circuit 60 becomes a high level, this high level signal is latched by the latch circuit 52 and output as an abnormal signal until the next starter motor operation is performed. .

In each of the above embodiments, the latch circuit 52 is reset by the ON signal from the starter motor circuit 46, and the memory element 59 in the embodiment shown in FIG. 4 is also refreshed by the ON signal from the starter motor circuit 46. However, it is also possible to reset or refresh these circuit components using an engine stop signal output when the engine is stopped.

In the embodiment described above, the actuator is fixed at the neutral position when there is an abnormality in the hydraulic system, but this is not limited to the actuator. It is possible to fix it in a predetermined position accordingly.

[Effects of the Invention] As described below, the four-wheel steering system for a vehicle according to the present invention is capable of moving the rear wheel steering system to a predetermined position when the hydraulic system that assists the steering operation of the rear steering system is activated. After the failure occurs, the steering angle of the rear wheel steering device is controlled by fixing the offset actuator at a predetermined position and switching to the predetermined steering state. Even if the oil field recovers for some reason, the rear wheel steering device is reliably held in a predetermined position, eliminating the risk of unstable steering and further increasing safety.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the main parts of an electrical system related to four-wheel steering according to an embodiment of the present invention, Fig. 2 is an overall schematic configuration diagram of an embodiment of the present invention, and Fig. 3 is an abnormality detection section thereof. Logic circuit diagram, 4th
The figure is a logic circuit diagram of an abnormality detection section according to another embodiment of the present invention. 7 is a rear wheel steering mechanism (rear wheel steering device), 25 is an actuator (pulse motor), 28 is a control means (controller), 41 is a hydraulic system, 43 is an operating state detection means (engine oil pressure sensor), 44 is oil pressure detection 45 is an abnormality determining means (an abnormality detecting section), 56 is an abnormality detecting section, and 57 is a driving state detecting means. Patent applicant Mazda Motor Corporation Figure 1 2q

Claims (1)

[Claims] 1. In a four-wheel steering system for a vehicle that includes an actuator that controls the steering angle of a rear wheel steering mechanism and a hydraulic system that assists the steering operation of this actuator, an operation that detects that the engine is rotating. A state detecting means, a hydraulic pressure detecting means for detecting the hydraulic pressure of the hydraulic system, and an abnormality determining means for determining whether or not there is an abnormality in the hydraulic system based on the outputs of the operating state detecting means and the hydraulic pressure detecting means are provided. A four-wheel steering system for a vehicle, comprising control means for fixing the actuator at a predetermined position after the means determines that there is an abnormality.