JPS5948264A - Controller for power steering - Google Patents

Abstract

PURPOSE:To prevent an assisting force from being increased when a vehicle speed sensor is failed, by a method wherein a trouble in a vehicle speed sensor is detected by detecting a rapid change in a vehicle speed signal, and the rotating speed of an oil pump is forcibly lowered when the trouble is detected. CONSTITUTION:A correcting circuit 31 is provided between a speed-voltage converting circuit 22 connected with a speed sensor 19 and a steering timer circuit 25 connected with a steering sensor 21. The correcting circuit 31 is comprised of an abnormality-discriminating means for detecting a trouble in the speed sensor 19 by detecting a rapid change in the vehicle speed signal s1 and a correcting means which regulates the output of the circuit 25 by receiving an output of the abnormality-discriminating means, thereby lowering the rotating speed of a motor 18 for controlling the rotating speed of the oil pump 14. When the speed sensor 19 is failed during high-speed running, the potential of the output of the circuit 22 is rapidly raised, which is detected by the correcting circuit 31, and the output thereof is reduced to zero. Accordingly, the output of the circuit 25 is also reduced to zero, and the rotating speed of the motor 18 is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for power steering used in an automobile, and more particularly to a control device equipped with a safety measure in case a vehicle speed sensor fails in vehicle speed sensitive power steering.

2. Description of the Related Art Among power steering systems that use hydraulic means to assist steering force, a vehicle speed-sensitive type that changes the assist force depending on vehicle speed is known. That is, for example, JP-A-55
As shown in No. 55059, when the vehicle speed is low and a large amount of auxiliary force is required, the rotational speed of the oil pump is increased to increase the auxiliary force, and as the vehicle speed increases, the auxiliary force is reduced. Variable types are known.

In this type of vehicle speed sensitive power steering, a vehicle speed sensor is used to detect vehicle speed.
If this vehicle speed sensor fails, a dangerous situation will occur. In other words, if the vehicle speed sensor fails during high-speed driving, the vehicle speed signal will output the vehicle speed at zero or close to zero, and the oil pump rotation speed will suddenly increase, causing a large auxiliary force to be applied to the steering. The steering suddenly becomes lighter. High-speed driving is the time when auxiliary force is least needed, and if a large amount of auxiliary force is applied at this time, the steering operation becomes abnormally light, creating a dangerous situation.

Therefore, there is a need for a safety device that automatically controls the auxiliary force so as not to increase it when the vehicle speed sensor fails.

An object of the present invention is to provide a power steering control device that suppresses the rotational speed of the oil pump to a low rotational speed and prevents the auxiliary force from increasing when the vehicle speed sensor fails. It is something to do.

The power steering control device of the present invention detects a failure in a vehicle speed sensor by detecting a sudden change in a vehicle speed signal, and when a failure is detected, corrects a control signal that controls the rotation speed of an oil pump to rotate the oil pump. The feature is that the number is forcibly reduced.

That is, the power steering control device according to the present invention includes a power cylinder that assists the steering force of the steering wheel, an oil pump that supplies pressure oil to the power cylinder, a rotation speed control means that controls the rotation speed of the oil pump, and a rotation speed control means that controls the rotation speed of the oil pump. A vehicle speed sensor that emits a vehicle speed signal according to the traveling speed, and the vehicle speed signal are inputted to the rotation speed control means,
A power steering device comprising a control means for inputting a control signal to reduce the rotation speed as the traveling speed increases, and an abnormality determining means for detecting that the vehicle speed signal from the vehicle speed sensor changes at a predetermined rate or more;
and signal correction means for receiving the output of the abnormality determining means and correcting the control signal inputted from the control means to the rotation speed control means so as to forcibly reduce the rotation speed to a predetermined value or less. This is a characteristic feature.

Here, the rotation speed control means specifically includes, for example, an electric motor that drives an oil pump and a semiconductor element that adjusts the amount of power supplied to the electric motor, or an electromagnetic engine that is connected between an engine and an oil pump. An oil pump that is connected to an electromagnetic clutch and controls the rotational speed of the oil pump by controlling this electromagnetic clutch is used. Further, as the abnormality determining means, a differentiation circuit that differentiates the output signal of the vehicle speed sensor and detects a sudden change in the output signal, a relay that is driven once by the output of the vehicle speed sensor, or the like can be used.

According to the power steering control device of the present invention, when the vehicle speed sensor fails, the failure is detected, and the control signal manually input to the rotation speed control means is corrected to forcibly reduce the rotation speed to a predetermined value or less. For example, even if the vehicle speed sensor fails and the vehicle speed signal suddenly drops to zero during high-speed driving,
Since the oil pump rotation speed is kept low and the auxiliary force does not increase, the steering operation will not suddenly become lighter, thus preventing danger.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram of a vehicle speed sensitive power steering system which is a target of a power steering control device according to an embodiment of the present invention. The power steering includes a rack and pinion type steering as manual steering, and a steering shaft 2 rotated by a steering wheel 1 is connected to a pinion 5 via joints 3 and 4. This pinion 5 is meshed with a rack 6, and at both ends of this rank 60, knuckle arms 8a are supported rotatably about shafts 7a and 7b.

Tie rods 9a and 9b engaged with 8b are connected. When the steering wheel 1 is operated and 20 rotations of the steering shaft are transmitted to the rack 6 via the pinion 5, the rack 6 moves in the left-right direction in the figure, and the knuckle arms ga, 8b are moved via the tie rods 9a, 9b. Rotation, steering wheel (generally front wheel) 10 a.

Give the steering angle to 10b.

” On the rack 6 is the piston 1 of the power cylinder 11.
1C is fixed and communicates with the oil chamber defined by this piston llc], 1a, and llb. 1.2 a
, 121) are connected to the oil pump 14 via the control pulp 13. The control pulp 13 is commonly used in this type of power steering device, and the control pulp 13 connects the discharge pipe 15 and return pipe 16 of the oil pump 14 to pipes 12a and 12b or 12b, respectively, depending on the steering direction. Switch the hydraulic system to connect to 12a and 12a. For example, when the rack 6 is steered to move to the right in the figure, the discharge pipe 15 is connected to the pipe 1'2b, and the return pipe 16 is connected to the pipe 12a. As a result, the rightward movement of the rack 6 is assisted by the hydraulic pressure within the power cylinder 11. Furthermore, when the steering shaft 2 is not being rotated, the control pulp 3 causes the discharge pipe 15 and the return pipe 16 to communicate directly, and does not send pressure oil to the power cylinder 11.

The oil pump 14 is driven by a motor 8 rotated by a power source 17 such as a battery. This motor 18 is controlled by a controller 20 to which a vehicle speed signal Sl is input from a speed sensor 19 that detects vehicle speed, so as to reduce the rotational speed and reduce the auxiliary force in accordance with an increase in the traveling speed of the vehicle. Furthermore, a signal S2 from a steering sensor 21 that detects that the steering wheel 1 has been rotated is also input to the controller 20.

The basic circuit of this controller 200 is shown in block form in FIG. As shown in FIG. 2, the controller 20 uses the vehicle speed signal S1 from the speed sensor 19 and the signal S2 based on the output of the steering sensor 21 to send the It controls the drive of the motor 18 that drives the oil pump 14. Output S1 of speed sensor 19
is converted to a voltage of 13 (the higher the speed is, the lower the speed is) by the speed voltage conversion circuit 22, and compared with the triangular wave constantly oscillated by the triangular wave generating circuit 23 by the comparator 24.
It becomes l-1 (high level) only while voltage B is higher than triangular wave A (as the vehicle speed increases, the duty ratio becomes smaller and
A rectangular wave signal C is output. On the other hand, the output S2 of the steering sensor 21 that detects the steering of the steering wheel 1 is transmitted through the steering timer circuit 25 to become a signal 1) which becomes 1-1 when the steering wheel is turned (during steering). 1 on the AND circuit circuit with signal C
Powered. In addition, the signal from the steering timer 25 is sent via the inverter 26 to the output E of the circuit 27 that constantly oscillates the idle duty, as well as to another AN.
It is input to D circuit a2. Two AND circuits “It”
The output of 2 becomes a power transistor chopping signal and is input from input terminal 1 to a control circuit 28 including a power transistor 28a and a relay Ry. A relay drive signal is input to another input terminal a of this control circuit 28. This relay drive signal is generated by a relay drive circuit 30 comprising a load current detection current transformer 29 connected in series to the motor 18, a Hall element, a transistor, and the like. This motor 18 drives an oil pump 14 that applies auxiliary force to the steering wheel 1, so that auxiliary force corresponding to the vehicle speed can be obtained.

The power steering control device of the present invention provides a vehicle speed signal S between the output terminal 22a of the speed-voltage conversion circuit 22 and the input terminal 25a of the steering timer circuit 250 in the above system diagram.
an abnormality determining means for detecting a failure of the speed sensor 19 by detecting a sudden change in speed sensor 19; and a motor for controlling the rotation speed of the oil pump 140 by changing the output of the steering timer circuit 25 in response to the output of the abnormality determining means. a correction circuit 31 including a correction means acting to reduce the rotation speed of 18;
It is characterized by having the following.

The details of this correction circuit 31 are shown in FIG.

The vehicle speed signal from the output end 22a of the speed-voltage conversion circuit 22 is inputted to a differentiating circuit 33 including a capacitor #C1 through an amplifier 32, and the output of this differentiating circuit 33 is F.
E T'Tl is inputted to a comparator 34 through a timer consisting of FBT1'2 and capacitor C2, and the output of this comparator 34 is 1 through a memory 35;
"Ei"r3 K input salel. F E 'l' Ta
Steering timer circuit 250 shown in FIG.
The input end 25a is connected to the connection point between the FET'l'4 which receives the output of the steering sensor 21 and the capacitor C4, and is further connected to the comparator 3.
6 will be man-powered.

The operation of the correction circuit 31 and steering timer circuit 250 will be explained below.

If the speed sensor 19 fails during high-speed driving, the output potential of the speed-voltage conversion circuit 22 will be as high as when the speed is zero, so the potential at the input terminal 22a of the correction circuit 310 will rise rapidly. This rapid rise is detected by the differentiating circuit 33, and a pulse output is input to FET1+. As a result, I''E T1'' is turned off, and I;' E i'i'2 is also turned off accordingly.

This causes capacitor C2 to discharge and comparator 34
The positive input of decreases and the output becomes zero. This zero output also makes the output of memory 35 zero, resulting in F E T
Ta turns on.

By turning on this FETTa, the lever 7ffc+ is passed through the input terminal 25a of the steering timer circuit 250.
Release! However, the input of the comparator 36 decreases and its output becomes zero 11o.

This output is the output 1) of the steering timer circuit 25, and when this becomes "0", the output of the AND circuit al becomes w'0", while one input of the AND circuit a2 becomes "l" through the inverter 26. Therefore, the AND circuit a2 is the output E of the idle duty generation circuit 27.
is output. As a result, the idle duty is input to the input terminal of the control circuit 280, the motor 18 is rotated at a low rotation speed, and the auxiliary force by the oil pump 14 is maintained small.

In this way, even if the speed sensor 19 fails during high-speed driving, the rotation of the oil pump 1140 is kept low and the auxiliary force is kept small, so there is no danger of the steering suddenly becoming light during high-speed driving. No such situation will occur.

Note that the above embodiment uses a differential circuit for abnormality determination and uses this output to adjust the amount of power supplied to the motor that drives the oil pump, but this is a speed-voltage conversion circuit. The structure is simple and advantageous in that it uses the output of However, it is possible to obtain similar effects in other ways, and the configuration of this part is not limited to that of the above embodiment. For example, a relay may be used to detect a failure in the speed sensor and turn off the motor, or the rotation of the engine may be transmitted to the oil pump via an electromagnetic clutch and controlled according to the vehicle speed. In a system that controls the rotational speed of the oil pump, the electromagnetic clutch can be operated by the relay to stop the oil pump in the event of a failure of the speed sensor.

According to the power steering control device of the present invention, as is clear from the above description, when the speed sensor fails during driving, the rotational speed of the oil pump is automatically reduced to a low rotational speed or stopped, and the steering assist force is This prevents the steering wheel from becoming too large, thereby preventing the risk of the steering wheel suddenly becoming light while driving at high speed.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of a vehicle speed sensitive power steering system which is a target of the power steering control device of the present invention, and Fig. 2 shows a basic circuit of a vehicle speed sensitive 3M power steering system equipped with the control device of the present invention. FIG. 3 is a circuit diagram showing essential parts of an embodiment of the control device of the present invention and a correction circuit according to 1. FIG. 4 is a circuit diagram showing an example of the steering timer circuit in the basic circuit. . 1... Steering wheel 11... Power cylinder 14... Oil pump 18... Motor 19... Vehicle speed (speed) sensor 20... Controller 21... Steering sensor 22... Speed-voltage Conversion circuit 25...Steering timer circuit

Claims (1)

[Claims] ■) A power cylinder that assists the steering force;
An oil pump that supplies pressure oil to this power cylinder, a rotation speed control means that controls the rotation speed of this oil pump,
A vehicle speed sensor that emits a vehicle speed signal according to the vehicle's running speed;
A control means that receives the vehicle speed signal and inputs a control signal to the rotational speed control means to reduce the rotational speed as the traveling speed increases, and detects that the vehicle speed signal from the vehicle speed sensor changes at a predetermined rate or more. and a signal for correcting a control signal manually inputted from the control means to the rotation speed control means so as to forcibly reduce the rotation speed to a predetermined value or less based on the output of the abnormality determination means. A power steering control device comprising correction means. 2) The engine according to claim 1, wherein the rotational speed control means includes an electric motor that drives the oil pump and a semiconductor element that adjusts the amount of power supplied to the electric motor. Power steering control device. 3) The power steering control device according to claim 1 or 2, wherein the abnormality determining means comprises a differentiating circuit that differentiates a vehicle speed signal.