JPS62191268A - Power steering control device - Google Patents

Abstract

PURPOSE:To prevent a steering from being stuck when the steering is shifted from one lock state to another lock state by extending the time in which the conductivity of a chopper is reduced when the power steering is returned to a straight advance condition. CONSTITUTION:When a current increase due to a steering operation is detected and a steering is rotated counter-clockwise from one lock state to the next lock state by increasing the chopping duty, the current flowing through a PS motor PM is decreased. Thereby, the current flowing through a shunt 2 is also decreased, and a current amplifier 25 is reversed from 1 to 0 at a certain point. Then, the potential at a point B tends to be decreased, but the potential at the point B is discharged via the time constant of a capacitor 11 and a resistor 12 and this time constant is set to a large value, thus the duty is not lowered to the neutral immediately after the steering is returned to the neutral. Accordingly, even at lock-to-lock, the rotation of the PS motor at the neutral is not decreased, and the steering is prevented from being stuck.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering control device using a chopper control device for a DC motor for driving a power steering pump in a vehicle equipped with power steering.

[Conventional technology]

As shown in Japanese Unexamined Patent Application Publication No. 58-71261, in the conventional method, when the vehicle is in a straight line, the DC motor that drives the power steering pump is operated at low rotation speed, and when the steering wheel is operated, the The rotation of the DC motor is increased.

That is, as shown in FIG. 2(a), the current flow rate of the chopper for supplying power to the DC motor is supported depending on the steering angle, as shown in FIG. 2(C).

[Problem that the invention seeks to solve]

However, in the conventional system described above, when the steering wheel is returned to the neutral direction as shown in FIG. 2(a), as shown in FIG.
The load current of the DC motor shown in b) decreases, and as the conductivity of the chopper decreases in response to this load current, the steering changes from the locked state to the locked state as shown in Figure 2(a). When a lock-to-lock operation is performed rapidly, the current near neutral drops from the normal neutral current (corresponding to the waiting time L' in Figure 2 (b)), and the current changes from the neutral state to the locked state. The flow rate of the chopper did not rise due to continuous operation (Fig. 3 (C)
) during the time t indicated by the broken line), a problem arises in terms of the feel of the steering wheel (steering suddenly becomes heavier).

[Means for solving problems]

In order to solve the above problems, the present invention provides a power steering control device that increases the rate at which the conduction rate of the chopper is reduced when the steering is returned to the neutral direction.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

B att is the battery that serves as the power source, Fl is the main circuit protection fuse, F2 is the control circuit protection fuse, PM is the power steering pump drive motor (hereinafter referred to as PS motor), and TR is the power supply to the PS motor PM. DF is a flywheel diode for flowing the circulating current of the PS motor PM when the chopper TR is OFF, SW is a start switch, and 1a is a PS motor PM.
and a contactor for switching on and off the main circuit connected in series with the chopper TR and turning ON and OFF the power supply to the battery Batt, 1b is the excitation coil of the contactor 1a, 2 is a shunt resistor that detects the current flowing through the chopper TR, 3° 4.8, 9.22
is a diode, 6,7,10°12~16.18,19
, 21.23 is a resistor, 5 is a known constant voltage circuit, 11.1
7 is a capacitor, and 11 is a resistor 12 whose discharge constant is determined to provide a delay element to be described later. 20
．． 24 is a transistor, 20 is synchronized with the chopper TR, and 24 is inverted synchronized. 25 is a current underground circuit that amplifies the voltage of shunt resistor 2, and 26 to 28 are OP amplifiers.
27 constitutes a voltage follower, 27 constitutes an oscillation circuit, and 2
8 is a comparator which ultimately determines the conductivity of the chopper. 29 is an OP amplifier 27, resistors 13 to 16. This is a triangular wave oscillation circuit composed of a capacitor 17.

Next, the operation of the above configuration will be explained. When the start switch SW is turned on, the contactor 1a is closed by the excitation coil lb, and at the same time, the chopper TR starts chopping at a low conduction rate (hereinafter referred to as DUTY) (50% or less), so the PS motor PM rotates at a low speed. Start rotating at . The command DUTY at this time is the voltage follower 26. It is obtained by comparison with the potential at point 2 transmitted to the capacitor 11 via the diode 9, and the oP amplifier 28 operates as a comparator. The details of this operation are shown in Figure 3 (al) and (bl). Here, in Figure 3 (al), the operational amplifier 2
On one terminal side of 8, capacitor 1 of triangular wave oscillation circuit 29 is connected.
7 is input manually, and a triangular wave A due to charging and discharging of the capacitor 17 is input. Further, when the steering is in the neutral state, a predetermined voltage shown as B is input to the child terminal side of the operational amplifier 28.

Then, as shown in FIG. 3(b), when the input voltage on the child terminal side of the operational amplifier 28 is higher than that on the one terminal side, a level is output to the output, the transistor 20 is made conductive, and the transistor 24 is cut off. Turn on the chopper TR according to the output of the operational amplifier 28.

Turn it off.

In addition, as mentioned above, when in neutral, the ON DUTY is reduced and the PS motor P
The current flowing through M is reduced. The above is the operation when in neutral.

Next, as shown in Fig. 2 (a), when the power steering (not shown) is turned to the right ([right]) from the neutral state to the locked state, the PS Since the current flowing through the motor PM increases, the current flowing through the shunt 2 increases.The shunt voltage is changed to the current amplifier 2.
5 increases the output, and when it exceeds the standard value, it outputs almost "1",
Power is applied to the child terminal of the operational amplifier 26 via the diode 8. Therefore, ■thermal potential is resistor 6 and resistor 7 when neutral.
was determined by the partial voltage ratio of
With the output, a high potential (about a constant voltage circuit voltage, e.g. 10
v), so the thermal potential also increases. Therefore, the output of the OP amplifier 28 becomes "1" as shown in FIG.
), the chopper TR becomes fully conductive (100%). In this way, when an increase in current due to steering operation is detected, the chopping DUTY is increased, and the steering is then turned to the left ([left]) from the locked state to reach the next locked state, the PS motor PM Since the current flowing through the shunt 2 decreases, the current flowing through the shunt 2 also decreases, and at a certain point the current amplifier 25 changes from "1" to "0".
(2) The thermal potential returns to its original value determined by resistors 6 and 7. ■Thermal potential also tries to decrease, but due to the time constant of the capacitor 11 and resistor 12, the thermal potential
:j is discharged, but this time constant is set to be large, so even if the steering wheel is returned to neutral, the chopping duty will be as shown in Fig. 2 ( As shown by the solid line in C1, the DUTY does not decrease to the neutral DUTY.At that time, even if the steering wheel continues to be turned in the opposite direction, the PS motor PM is operating at a certain high rotational speed, and the steering operation Since the load current also increases, the rlJ output of the current amplifier 25 causes the same operation as described above.

Therefore, due to lock-to-lock, when transitioning from a lock state to the next lock state, even if the chopper TR passes through the neutral state, the chopping DUTY of the chopper TR does not suddenly drop to the chopping DUTY at the neutral state, and the PS motor This eliminates the problem of the steering becoming stuck due to a drop in PM rotation.

[Effects of the Invention] As described above, in the present invention, when returning the power steering to the straight-ahead state, the time for reducing the conductivity of the chopper is lengthened. Even when shifting, there is an excellent effect in that the steering wheel can be prevented from getting stuck without slowing down the rotation of the DC motor in the neutral state.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram showing an embodiment of the power steering control device of the present invention, and Fig. 2 (al, (bl, (C))
is the input of the operational amplifier 28 for the steering operation time and the steering operation time of the present invention and the prior art. FIG. 4 is a characteristic diagram showing output (when in neutral) and output (when steering is operated). 2... Shunt resistor, 11... Capacitor, 12...
... Resistor, 25... Current amplifier, 26-28... Operational amplifier, 29... Triangular wave oscillation circuit, Batt.
...Battery, PM...DC motor for power steering, TR...Transistor forming a chopper,
DF...Flywheel diode, SW...Start switch.

Claims (1)

[Claims] A DC motor that drives a power steering pump; a chopper that is connected in series with the DC motor and supplies power; when the power steering is maintained in a straight line, the current flow rate of the chopper is reduced; a current flow rate control device that detects an increasing current when the steering wheel is rotating and raises the current flow rate of the chopper to a predetermined value; The power steering control device is characterized in that when the power steering is rotated, the time required to increase the flow rate of the chopper is longer than the time required to raise the flow rate of the chopper.