JPH0215435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention provides a method for operating an electric motor by supplying power from an on-vehicle power supply after an internal combustion engine is started and after the voltage generated by an alternator reaches a predetermined value.
This electric power steering device for a vehicle uses an electric motor to assist the steering force of the steering wheel via a hydraulic system or by a mechanical structure, and in particular, despite the accidental stoppage of the internal combustion engine during operation of the vehicle, The present invention relates to an electric power steering device having an electric motor drive holding function.

BACKGROUND OF THE INVENTION Conventionally, electric power steering devices have been known that receive electric power from an on-vehicle power source to drive an electric motor dedicated to power steering to provide steering assistance.

However, in this type of electric power steering device, when starting the engine, which consumes a large amount of power,
In order to prevent power loss due to driving the electric power steering device, a controller such as a microprocessor that controls the power supply from the in-vehicle power supply to the electric motor for power steering must be turned on when the key switch is turned on. The drive control of the electric motor is made possible only by inputting both the electrical component energizing signal given to the product and the power generation signal from the alternator for charging the on-board battery. Both signals are configured to act as gate signals to control power supply to the electric motor.

Therefore, in a vehicle equipped with an electric power steering device such as the one described above, if the internal combustion engine accidentally stops while driving due to an incorrect driving operation, the supply of the power generation signal from the alternator to the controller is cut off. As a result, the electric motor stopped and the steering assist function was suddenly lost.

DISCLOSURE OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved electric power steering device capable of overcoming the above-mentioned drawback that the steering assist function is interrupted due to accidental stoppage of the internal combustion engine. It is said that

According to the present invention, in the presence of both the power generation signal of the alternator for charging the on-board battery and the electrical component energization signal given when the key switch is in the ON state, it responds to the detection output of the vehicle speed sensor and the steering sensor. In the electro-hydraulic power steering device for a vehicle, which includes a controller that controls power supply from an on-vehicle power supply to an electric motor for power steering, the controller is provided with an electric motor drive holding circuit, and the circuit Therefore, even if the supply of the power generation signal to the controller is cut off due to an accidental stop of the internal combustion engine during operation, as long as the electrical component activation signal is present, in other words, the key switch will remain in the ON state. As long as the electric motor remains active, the steering assist function can be maintained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The figure schematically shows an embodiment of an electric power steering device according to the invention, which is equipped with an electric motor drive holding circuit, and in particular provides steering assistance via a hydraulic system. This figure shows an electric power steering device with vehicle speed and steering sensitivity characteristics.

As is known, a steering wheel (not shown) is connected via a steering shaft 2 to a control valve 1 which operates as a servo valve. The input side of the control valve 1 is connected to the supply port P1 and the return port P2 of the oil pump 3, respectively. Control valve 1
The output side of is connected to ports A and B, respectively, of a power cylinder 4 that operates as an actuator. The power cylinder 4 receives the pressure of hydraulic oil from the supply port P1 of the oil pump 3 into one of its chambers via the control valve 1, operates the cylinder in either the left or right direction, and reduces the back pressure. through the control valve 1 to the return port P2 of the oil pump 3
Return to The operating output of the power cylinder 4 is transmitted to the left and right wheels (not shown) from both ends of the rack gear 5, and at the same time is transmitted as an assist force to the steering wheel via the pinion gear 6 and the steering shaft 2. Steering power is doubled.

The oil pump 3 is driven by a dedicated electric motor 7, and its drive is controlled by a controller 8. The controller 8 receives power from an on-vehicle battery 9 and an alternator 13, and receives a drive output gate signal from a drive holding circuit 10, which will be described in detail later. The power supply to the electric motor 7 is controlled in response to the speed signal and the steering signal from the steering sensor 12 . That is, the controller 8 functions as an electronic switch for controlling the power supply to the electric motor 7 for driving the power steering.

The power generation output of the alternator 13 driven by an internal combustion engine (not shown) is supplied by the charge/voltage adjustment circuit 14 to the on-vehicle battery 9 as charge energy and also to the charge warning circuit 15 as a power generation signal. .

The charging warning circuit 15 is widely known in the technical field as a circuit that monitors the charging state of the vehicle battery 9. This charging warning circuit 15
In this case, the electrical component activation signal supplied to the electrical components via the movable contact a of the engine key switch KS and the power generation signal obtained via the movable contact b and the charging warning light LA are both logical control signals. As shown in FIG. The electromagnetic relay RL of the charging warning circuit 15 operates to open its normally closed contact C when the generated output of the alternator 13 reaches a predetermined value, that is, the charging voltage. The drive holding circuit 10 is composed of an inverter INV, a flip-flop FF, and an AND circuit AND.

When the engine key switch KS is ON,
When the power generation output of the alternator 13 has not reached a predetermined value, the first input IN1 of the drive holding circuit 10 is at the "H" level due to the presence of the electrical component energization signal, and the second input IN2 is at the "H" level due to the presence of the electrical component energization signal. It is at "L" level when contact C is closed. Therefore, the inverter
The first input of the flip-flop FF via INV is at the "L" level, the second input is at the "L" level, and its output maintains the "L" level. Since the two inputs are at the "L" level, the output, that is, the drive holding circuit 10
The output OUT of is at "L" level. This means that there is no drive output gating signal supplied to the controller 8 and therefore the power supply to the electric motor 7 is stopped.

Next, under normal operating conditions in which the power generation output of the alternator 13 has reached a predetermined value, the second input IN2 of the drive holding circuit 10 is Changes from "L" level to "H" level. Therefore, the output of the flip-flop FF changes to "H" level,
Both the first and second inputs of the AND circuit AND are “H”
level, so its output becomes "H" level. As a result, the output OUT of the drive holding circuit 10 becomes "H" level, in other words, the drive output gate signal is supplied to the controller 8, and a state in which power can be supplied to the electric motor 7 is established.

Under normal operating conditions, if the internal combustion engine accidentally stops due to incorrect operation,
The supply of the power generation signal to the charging warning circuit 15 is cut off. As described above, in the conventional electro-hydraulic power steering device, in such a case, power supply from the controller 8 to the electric motor 7 becomes impossible, and the steering assist function is suddenly lost. However, as shown in the figure, according to the present invention, even if the second input IN2 of the drive holding circuit 10 changes to the "L" level due to the absence of the power generation signal, the output of the flip-flop FF remains "H".
Since both the first and second inputs of the AND circuit AND are maintained at “H” level,
The output, ie, the output OUT of the drive holding circuit 10, is maintained at the "H" level. Therefore, even if the internal combustion engine accidentally stops under normal operating conditions,
As long as the engine key switch KS is in the ON state, the output of the drive output gate signal is guaranteed, and the state in which power can be supplied to the electric motor 7 is maintained until the engine key switch KS is turned OFF.

Effects As described in detail above, according to the present invention, when starting an internal combustion engine, oil and gas will be lost unless the engine key switch is returned to the ON position immediately after the starter generates electricity in the alternator, as in the conventional case.
This has the energy-saving effect of not being able to drive the pump, i.e. the electric motor, and furthermore, in the event of an abnormality in which the internal combustion engine accidentally stops during normal operation, the electric motor will not be activated as long as the engine key switch is kept in the ON position. It is possible to provide an electric power steering device that can continue to drive and therefore has extremely excellent safety and operability without interrupting the steering assist function.

[Brief explanation of drawings]

The figure shows an embodiment of the electric power steering device of the invention. (Description of symbols), 1: Control valve, 2: Steering shaft, 3: Oil pump, 4: Power cylinder,
5: Rack gear, 6: Pinion gear, 7: Electric motor, 8: Controller, 9: Vehicle battery, 10:
Drive holding circuit, 11: Vehicle speed sensor, 12: Steering sensor, 13: Alternator, 14: Charging/voltage adjustment circuit, 15: Charging warning circuit.

Claims (1)

[Claims] 1 Power is supplied to the electric motor that drives the power steering mechanism using a power generation signal given from the alternator for charging the on-board battery and an electrical component energization signal given from the on-board power supply when the engine key switch is ON. In an electric power steering system for a vehicle, the electric power steering device is provided with an electronic controller that controls the control as long as the electrical component energization signal is present when the internal combustion engine is accidentally stopped and the power generation signal is not present. The electric power steering device further comprises an electric motor drive holding circuit that maintains power supply to the electric motor by the electric power steering device.