JPH0313418Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is based on an electronically controlled power steering device that changes the steering force (response) by controlling the current flowing through the solenoid valve. The present invention relates to an electronically controlled power steering device in which a solenoid coil is disconnected to increase steering force when a solenoid coil is detected.

In addition to the normal power steering function, the electronically controlled power steering system changes the hydraulic characteristics relative to the steering force depending on the vehicle speed by controlling the hydraulic pressure that acts on the reaction plunger installed in the input shaft of the gearbox. This is a device that obtains appropriate steering characteristics according to any vehicle speed and steering condition. The hydraulic pressure acting on the reaction plunger described above is controlled by a solenoid valve provided in the oil passage. If a conduction failure occurs in the transistor that controls the solenoid coil of such a solenoid valve, the steering force will be reduced, resulting in a lack of running stability at high speeds.

This idea was made in view of the above points,
The purpose of this is to control the current flowing through the solenoid valve in an electronically controlled power steering system that changes the steering force (response).If a conduction failure is detected in the transistor that controls the solenoid coil of the solenoid valve, To provide an electronically controlled power steering device which secures running stability by disconnecting a solenoid coil and increasing steering force.

Hereinafter, an electronically controlled power steering device according to an embodiment of the invention will be described with reference to the drawings. In the figure, 11 is an EPS (electronic power steering) control circuit that controls the current flowing through a solenoid coil 12 of a solenoid valve (not shown) to change the steering force (response) of the steering wheel. This EPS control circuit 1
1 controls the current flowing through the solenoid coil 12 by controlling the pulse width of the pulse current flowing through the emitter of the output transistor 13 according to the vehicle speed.

This solenoid coil 12 drives a solenoid valve that controls the pressure acting on a reaction plunger provided in the input shaft portion of the gearbox. The longer the current flows through the solenoid coil 12, the longer the solenoid valve is driven, and the hydraulic pressure acting on the reaction plunger is controlled to be smaller. Since the time during which current flows through the solenoid coil 12 is shortened in accordance with the vehicle speed, the driving time of the solenoid valve is shortened, and the hydraulic pressure acting on the reaction plunger is controlled to be large. A power supply Vc is supplied to the collector of the transistor 13 through a relay switch 14S of a relay 14. The relay switch 14s is closed when the relay coil 14 is not energized, and the contact is opened when the relay coil 14 is energized. Furthermore, one end of the solenoid coil 12 is grounded via a disconnection detection resistor R _S . A connection point A between the solenoid coil 12 and the disconnection detection resistor R _S is input to a comparison circuit 16 via an integrating circuit 15 consisting of a resistor RO and a capacitor CO. Above integration circuit 1
The output of 5 is input to one terminal of a comparator 17 in the comparison circuit 16. + of this comparator 17
A reference voltage determined by the ratio of resistor R1 to resistor R2 is input to the terminal. In other words, the integration circuit 15
and the comparison circuit 16 detects the disconnection detection resistor R _S
When the voltage generated at the voltage exceeds a predetermined value (for example, 3V), the output of the comparison circuit 16 becomes H level.
The output of the comparison circuit 16 is input to the S terminal of the S-R flip-flop 18. The potential at the connection point between the capacitor C and the resistor R3 is input to the R terminal of the flip-flop 18. moreover,
The Q output of the flip-flop 18 is connected to one end of the relay coil 14. Further, the Q output of the flip-flop 18 is connected to the base of a transistor 19 via a resistor R4. Further, the collector of the transistor 19 is connected to a conduction failure alarm lamp 20.

Next, the operation of this invention configured as described above will be explained. The EPS control circuit 11 controls the pulse width of the pulse current flowing through the emitter of the transistor 13 in accordance with the vehicle speed, thereby controlling the current flowing through the solenoid coil 12. For example, as the vehicle speed increases, the pulse width of the current flowing through the solenoid coil 12 becomes smaller, the driving time of the solenoid valve becomes shorter, and the hydraulic pressure acting on the reaction plunger is controlled to increase, thereby controlling the steering wheel steering force ( (response) becomes heavier.
On the other hand, when the vehicle speed decreases, solenoid coil 1
The pulse width of the current flowing through the solenoid valve 2 becomes larger, the driving time of the solenoid valve becomes longer, and the hydraulic pressure acting on the reaction force plunger is controlled to be smaller, thereby reducing the steering force of the steering wheel.

By the way, if no conduction failure occurs in transistor 13, transistor 1 is connected to connection point A.
3, a lower pulse-like voltage is generated than when a continuity fault occurs. And the above connection point A
The voltage is smoothed via the integrating circuit 15 and input to the comparing circuit 16. In this comparison circuit 16, the values of resistors R1 and R2 are set so that an L level signal is output when the transistor 13 does not have a conduction failure (that is, when the potential at the connection point A is smaller than 3V). ing. Therefore, if no conduction failure occurs in transistor 13, flip-flop 18 is not set, and its Q output becomes "0". Therefore, relay coil 1
4 is not energized and the continuity failure alarm lamp 2
0 is also not lit.

On the other hand, if a conduction failure occurs in the transistor 13, the potential at the connection point A increases significantly to 3V or more. Therefore, the output of comparison circuit 16 becomes H level, and flip-flop 18 is set. Therefore, the relay coil 14 is excited and the relay switch 14S is opened. As a result, no current is supplied to the solenoid coil 12,
The hydraulic pressure acting on the reaction plunger is controlled to be large, and the steering force of the steering wheel becomes heavy. Further, the transistor 19 is turned on and the continuity failure alarm lamp 20 is turned on. This notifies the driver that the transistor 13 has a conduction failure.

Therefore, it is possible to prevent the transistor 13 from causing a conduction failure, causing a large current to flow through the solenoid coil 12 and reducing the hydraulic pressure acting on the reaction force plunger, thereby preventing the steering force from becoming light. . For example, if such a conduction failure occurs during high-speed running and the steering force becomes light, it is possible to prevent running stability from deteriorating.

As detailed above, according to this invention, in an electronically controlled power steering device that changes the steering force (response) by controlling the current flowing through the solenoid valve, the conduction of the transistor that controls the solenoid coil of the solenoid valve If a failure is detected, the solenoid coil is disconnected and the steering force is increased, so even if a conduction failure occurs during high-speed driving, driving stability can be ensured.

[Brief explanation of the drawing]

The drawing is a diagram showing an electronically controlled power steering device according to an embodiment of the invention. 11...EPS control circuit, 12...Solenoid coil, 14...Relay, 18...Flip-flop, 20...Lamp for continuity failure alarm.

Claims (1)

[Scope of utility model registration request] It has a solenoid valve that controls the pressure acting on a reaction force plunger provided in the input shaft portion of the gearbox, and the pressure acting on the reaction force plunger is reduced in inverse proportion to the current flowing through the solenoid coil of the solenoid valve. In the electronically controlled power steering device that is controlled,
A transistor that controls the solenoid coil of the solenoid valve, a failure detection unit that detects a conduction failure of the transistor, and a failure detection unit that cuts off the power to the solenoid coil when the failure detection unit detects a conduction failure of the transistor. and means for increasing the pressure acting on the reaction force plunger to increase the steering force.