JPS6018453A - Control method for power steering device - Google Patents

Abstract

PURPOSE:To save energy by changing the amperage to be judged, in accordance with the temp., in case the current to the motor shall be shut when the current flowing in the motor is judged to be below a specific value, thereby carrying out a proper judgement of amperage, and by judging that motor operation is not needed. CONSTITUTION:When current flows through a motor 12, a voltage is generated at a resistor 11 to be fed to non-inversible input terminals of comparators 2-4 through resistors 8-10. Any comparator where the voltage fed to the non-inversible input terminal is greater than the voltage fed to the inversible input terminal shall emit an output signal at (1) level, while the comparators with different judgement emit an output signal with (0) level. Thereby a control circuit 1 reads the current value flowing in the motor 12. Here the characteristics of thermistors 13-15 shall be set so that the change of reference value fed into the inversible input terminal according to temp. change will be equal to the amount of change of the voltage fed into the non-inversible input terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control method for a power steering device that shuts off power steering when unnecessary.

[Prior art]

In recent years, an increasing number of automobiles are equipped with power steering devices that allow easy steering. This device allows steering to be performed almost uniformly and with small force from low to high speeds, and controls the rotational speed of the motor-driven oil pump according to driving conditions such as the steering angle. For example, there is a system that operates a pump only while the steering wheel is being turned, and the steering is detected by a pulse generator attached to the steering shaft. In this case, even if there is a load on the steering system, no steering signal is generated when the steering shaft does not rotate, that is, when the steering is held, the motor stops and the steering force changes suddenly during the held steering.

In order to prevent this phenomenon, when the current flowing to the motor is above a certain reference value, it is determined that the steering is held, and the current flowing to the motor is not interrupted, and only when the current flowing to the motor is below the reference value, power steering is determined to be unnecessary. Motor current is cut off.

However, when the temperature drops, the viscosity of the oil circulated by the oil pump increases, so a current higher than a reference value flows even when power steering is not required, making it impossible to determine an appropriate current value.

[Object and structure of the invention]

Therefore, an object of the present invention is to provide a control method for a power steering device that can appropriately determine a current value even when the temperature changes.

In order to achieve such an object, the present invention changes a reference value for determining a current value in accordance with the temperature. The present invention will be described in detail below using drawings showing embodiments.

〔Example〕

FIG. 1 shows an embodiment in which the present invention is applied to a circuit for determining the magnitude of motor current in a power steering system. In the figure, 1 is a control circuit, 2 to 4 are comparators, and 5 to 10 are
11 is a resistor for the comparator input circuit, 11 is a current detection resistor, 12 is a seventh resistor for driving the oil pump, and 13 to 15 are thermistors. Resistors 5-7 and thermistor 13-
15, a constant and a value are appropriately selected, and three types of current flowing through the motor 12 can be selected by comparators 2 to 4. The control circuit 1 has terminals 1a to 1c.
The current flowing through the motor 12 is read in response to the signal supplied to the motor 12.

The operation of the circuit configured in this way is as follows. When current flows through the motor 12, a voltage is generated across the resistor 11, and this voltage is supplied to the non-inverting input terminals of the comparators 2-4 via the resistors 8-10.

The comparator, in which the voltage supplied to the non-inverting input terminal is greater than the voltage supplied to the inverting input terminal, sends out an output signal of the "1"level; A comparator whose voltage is smaller than the voltage applied to its inverting input terminal will provide an output signal at the "0" level. For this reason, the control circuit 1 reads the value of the current flowing through the motor 12 from the supplied signal, and if this current value is equal to or greater than a predetermined value, it determines that the steering is held and maintains the motor current.

When the air temperature decreases and the temperature of the oil circulated by the oil pump decreases, the viscosity of the oil increases, so the motor current increases and the voltage generated across the resistor 11 increases.

On the other hand, the thermistors 13 to 15 have a property that their resistance value increases as the temperature decreases, as shown in FIG. Since the reference value supplied to the inverting input terminal of comparators 2 to 40 is expressed by the following formula, the temperature decreases and the thermistor 13
When the resistance value of ~15 increases, the reference value increases.

However, each symbol has the following convention.

■: Reference value VDD: Power supply voltage Rth: Resistance value of thermistors 13 to 15 R: Resistor 5 to
Therefore, when the temperature decreases, the voltage supplied to both the inverting input terminal and the non-inverting input terminal of the converters 2 to 4 increases. Therefore, the thermistors 13 to 13
By selecting 15 characteristics, it is possible to appropriately judge the current value and accurately determine the steering condition even if the temperature changes.

FIG. 3 is a circuit diagram showing another embodiment, and the same symbols are used for the same parts and corresponding parts as in FIG. 1. In the figure, 20 to 23 are resistors, 24 is an amplifier, and 26 is a capacitor. In the circuit configured in this way, the amplifier 2
The amplification degree A of 4 is expressed as follows.

Therefore, when the temperature decreases and the resistance value Rth of the thermistor increases, the amplification degree decreases. Therefore, the thermistor 13 is designed so that the increase in voltage generated across the resistor 11 due to a decrease in temperature is compensated for by the decrease in the amplification degree of the amplifier 24.
If the characteristics are selected, the level of the signal supplied to the comparators 2 to 4 will not change even if the temperature fluctuates, so the current flowing through the motor 12 can be read to determine whether or not the steering is held. can do.

Although the above embodiments have been described with reference to the case where the viscosity of the oil increases at low temperatures, the influence of the motor current reduction due to the decrease in oil viscosity can be corrected by decreasing the resistance value of the thermistor at high temperatures.

Furthermore, it is desirable to provide the thermistor as close to the circulating oil passage as possible.

〔Effect of the invention〕

As explained above, the control method for the power steering device according to the present invention changes the value of the current to be determined according to the temperature, so the current value can be determined regardless of the temperature, so the power steering device can be controlled. Even when the steering device is not operating, when a large current is flowing due to the low temperature, it can be determined that the motor does not need to be operated and the current can be cut off, resulting in an energy-saving effect.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of a current value determination circuit constructed by applying the present invention, Fig. 2 is a graph showing the temperature vs. resistance characteristics of a thermistor, and Fig. 3 is a circuit showing another embodiment. It is a diagram. 1...fIilJ both circuits, 2-4...comparator, 5-11.20-23...resistance, 13-
15... Thermistor, 24... Amplifier, 26...
...Capacitor. Patent applicant Jidosha Kiki Co., Ltd.

Claims (1)

[Claims] Current determined as 1 in a power steering device control method that performs power steering by controlling the rotational speed of a motor-driven oil pump and cuts off the motor current when the value of the current flowing through the motor is determined to be less than a predetermined value. A method for controlling a power steering device, characterized in that the value of is changed in accordance with temperature.