JPH0215433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for power steering used in automobiles, and more particularly to a control device equipped with a safety measure in case a power relay malfunctions 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 is known that changes the assist force depending on the vehicle speed. For example, as shown in Japanese Patent Application Laid-Open No. 55-55059, when the vehicle speed is low and a large 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 increased. A type with variable assist force (assist force) is known.

In this kind of vehicle speed sensitive power steering, especially in the type that uses a power transistor to control the motor and the motor drives the oil pump, when a large auxiliary force is required, the amount of electricity supplied to the motor is reduced. This increases the load on the transistor. This condition lasts for a relatively long time, such as when driving at low speeds in traffic jams, so in order to protect the transistor from such high load conditions, a bypass circuit installed in parallel with the transistor is used to connect the power supply to the motor during high loads. It is known that it is directly connected to . In other words, when the motor is under high load, a current transformer connected in series with the motor activates a Hall element, etc., which excites the coil of a power relay installed in parallel with the power transistor, and the power relay bypasses the power transistor. Protection circuits are known that sometimes do not load the power transistors.

In power steering equipped with such a protection circuit, if a current transformer or relay malfunctions when driving at high speed, the power relay malfunctions and causes a high current to flow through the motor through the bypass circuit, causing a sudden increase in the rotation speed of the oil pump. There is a possibility that the auxiliary force will be increased by increasing the auxiliary force.
This results in light steering while driving at high speeds, which is extremely dangerous.

Therefore, it is necessary to take safety measures to prevent the power relay from operating during high-speed running and to prevent excessively high assisting force from occurring.

SUMMARY OF THE INVENTION In response to such needs, it is an object of the present invention to provide a power steering control device that includes means for preventing the relay from operating when the vehicle speed exceeds a predetermined speed.

The power steering control device of the present invention detects when the traveling speed is equal to or higher than a set value, and
The present invention is characterized in that it includes a safety means for preventing an excitation signal from being applied to the coil of the power relay. That is, the control device of the present invention:
A power cylinder that assists the steering force, an oil pump that supplies pressurized oil to this power cylinder, an electric motor that drives this oil pump, a semiconductor element that adjusts the amount of power supplied to this electric motor, and a semiconductor element that adjusts the speed of the vehicle. a control means which receives a corresponding speed signal and issues a control signal to the semiconductor element to reduce the amount of power supplied as the running speed increases; a relay whose contacts are connected in parallel to the semiconductor element; A power steering control device comprising load detection means that detects a high load state and issues an excitation signal to the coil of the relay, which detects that the traveling speed is above a set value and sends an excitation signal to the coil of the relay. This feature is characterized by the provision of a security means for preventing the application of the voltage.

As a safety measure, for example, when a vehicle speed signal is received and the vehicle speed exceeds a predetermined value, the transistor connected in series with the power relay coil is turned off to prevent the power relay from turning on. You can use any means to do so.

According to the present invention, the power relay is always inoperative when the vehicle speed exceeds a predetermined value and the power steering assist force is no longer required. Even if you try to malfunction, it will never actually malfunction. Therefore, the danger that the auxiliary force suddenly increases during high-speed driving is prevented.

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 system includes a rack and pinion steering system as a manual steering system, 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 easy 6
At both ends of the rack 6 are shafts 7a,
tie rods 9a, 9b engaged with knuckle arms 8a, 8b rotatably supported around 7b;
are connected. When the steering wheel 1 is operated and the rotation of the steering shaft 2 is transmitted to the rack 6 via the pinion 5, the rack 6
moves in the left-right direction in the drawing, rotates the knuckle arms 8a, 8b via tie rods 9a, 9b, and gives steering angles to the steered wheels (generally front wheels) 10a, 10b.

A piston 11c of a power cylinder 11 is fixed to the rack 6, and a piping 1 communicating with oil chambers 11a and 11b defined by the piston 11c.
2a and 12b are connected to an oil pump 14 via a control valve 13. The control valve 13 has conventionally been commonly used in this type of power steering device, and connects the discharge pipe 15 and return pipe 16 of the oil pump 14 to pipes 12a and 12, respectively, depending on the steering direction.
b, or switch the hydraulic system to connect to 12b 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 12b, 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. Further, when the steering shaft 2 is not rotating, the control valve 13 allows 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 powered by a power source 17 such as a battery.
It is driven by a motor 18 rotated by. This motor 18 is controlled by a controller 20 to which a vehicle speed signal _S1 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 running speed of the vehicle. Furthermore, a signal S ₂ from the 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 20 is shown in block form in FIG. As shown in FIG. 2, the controller 20 receives a vehicle speed signal from the speed sensor 19.
S ₁ and a signal S ₂ based on the output from the steering sensor 21 drive the motor 18 that drives the oil pump 14 via a control circuit 28 including a power transistor 28a and a relay Ry. The output _S1 of the speed sensor 19 is converted into voltage B (lower as the speed is higher) by the speed voltage conversion circuit 22, and compared with the triangular wave A constantly oscillated from the triangular wave generating circuit 23 by the comparator 24. H only while is higher than triangular wave A
A rectangular wave signal C that becomes (high level) (the duty ratio decreases as the vehicle speed increases) is output. On the other hand, the output S ₂ from the steering sensor 21 that detects the steering of the steering wheel 1 is passed through the steering timer circuit 25 to become a signal D that becomes H when the steering wheel is turned (during steering), and together with the signal C. Input to AND circuit _a1 . Further, the signal D from the steering timer 25 is inputted via the inverter 26 to another AND circuit _a2 together with the output E of the circuit 27 that constantly oscillates the idle duty. two AND circuits
The outputs of a ₁ and a ₂ become power transistor chopping signals and are inputted from input terminal b 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 transmitted to a relay drive circuit 30 consisting of a load current detection current transformer 29 connected in series to the motor 18, a Hall element, a transistor, etc.
emanates from. 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 has a transistor Tr 2 in the controller 20 between the output terminal of the speed-voltage conversion circuit 22 indicated by and the base terminal of the transistor Tr ₂ in the current detection and relay drive circuit 30. It is characterized in that a power relay activation prevention circuit 31 (corresponding to the above-mentioned safety means) as shown in FIG. 3 is connected.

FIG. 3 shows the control circuit 28, current detection, and relay drive circuit 3 shown in the controller 20 of FIG.
0 shows the power relay prevention circuit 31 which is a feature of the present invention. Below, the third
Embodiments of the present invention will be explained in detail with reference to the drawings.

A signal determining the auxiliary force according to the outputs S ₁ and S ₂ of the speed sensor 19 and the steering sensor 21 is input to the base of the power transistor 28 a of the control circuit 28 . As a result, a current for driving the motor 18 flows through the power transistor 28a. When this current exceeds a predetermined value (for example, when driving at low speed or stopping when parking, etc.), the transistor Tr 2 is turned on by the action of the current transformer 29 for detecting the load current and the Hall element 30a that receives this action, and the transistor Tr ₂ is turned on. A current flows through the relay coil Rc of the power relay Ry connected in _series to the power transistor 28a, the normally open relay contact Rx is turned on, and the power transistor 28a is bypassed to the normally open relay contact Rx connected in parallel. Therefore, the power transistor 28a is protected from a large load, a large current continues to flow through the motor 18, and a large auxiliary force is maintained.

On the other hand, the prevention circuit 31 connected between the base of the transistor Tr ₂ and the output terminal of the speed-voltage conversion circuit 22 includes a comparator 31a that compares the output B of the speed-voltage conversion circuit 22 with a predetermined level. , this output is the transistor Tr ₁
connected to the base of. this transistor
Tr ₁ is connected between the base of the transistor Tr ₂ and the ground, and is turned on when the output of the comparator 31a becomes high level (H), and turned off when the output falls below the high level (H). Since the input of the comparator 31a is the output B of the speed-voltage conversion circuit 22, when the vehicle speed exceeds a predetermined value and reaches a high speed region that does not require a large auxiliary force, the output of the comparator 31a becomes high level (H). , turns on transistor Tr ₁ . As a result, the base of the transistor Tr ₂ is grounded, so the transistor Tr 2 is turned off. Therefore, in this state, no current flows through the relay coil Rc, and the power relay Ry is kept in the OFF state, so that the motor 18 always has the power transistor 28.
a is connected, and a large current is prevented from flowing to the motor 18.

In this way, in the above embodiment, the comparator 31a of the power relay activation prevention circuit 31 detects a vehicle speed equal to or higher than a predetermined value and switches the first transistor Tr ₁
, which turns on the power relay coil Rc
Since the second transistor Tr 2 connected to Tr ₂ is turned off, the power relay Ry is kept inactive,
The power relay will not turn on due to malfunction when driving at high speeds.

In the above embodiment, a power transistor is used as an element for adjusting the amount of current supplied to the motor 18, but a thyristor may also be used. In addition, a transistor Tr ₂ is used to turn on and off the coil that drives the power relay, and another transistor Tr ₁ is used to control the on and off of this transistor Tr ₂ , but these transistors Tr ₁ and Tr ₂ may be replaced by another switch element, such as another relay.

The power steering control device according to the present invention includes:
As is clear from the above explanation, when the vehicle speed exceeds a certain level, the power relay is prevented from operating, and the bypass for preventing high loads on the semiconductor element that adjusts the amount of power supplied to the motor is disabled. Prevents large current from flowing. Therefore, the assisting force of the power steering is prevented from increasing due to malfunction during high-speed driving, and safety during high-speed driving is ensured.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of vehicle speed sensitive power steering which is the object of the power steering control device of the present invention, Fig. 2 is a block diagram showing the basic circuit thereof, and Fig. 3 is an embodiment of the present invention. FIG. 2 is a circuit diagram showing a power relay activation prevention circuit, which is a main part of a power steering control device according to the present invention, and its peripheral circuit configuration. 1... Steering wheel, 11... Power cylinder, 14... Oil pump, 18... Motor, 19... Vehicle speed sensor, 20...
Controller, 21...Steering sensor, 2
2... Speed-voltage conversion circuit, 25... Steering timer circuit, 27... Idle duty generation circuit, 28... Control circuit, 28a... Power transistor, 29... Current transformer, Ry
...Power relay, Rc...Relay coil, 30
...Current detection, relay drive circuit, 30a...Hall element, 31...Power relay operation prevention circuit, 3
1a...Comparator.

Claims (1)

[Claims] 1. A power cylinder that assists the steering force, an oil pump that supplies pressure oil to the power cylinder, an electric motor that drives the oil pump, and a semiconductor that adjusts the amount of power supplied to the electric motor. A speed signal corresponding to the running speed of the vehicle is inputted to the element, and a control means and a contact point are connected in parallel to the semiconductor element to issue a control signal to reduce the amount of power supplied to the semiconductor element as the running speed increases. a relay, a load detection means that detects a high load state of the electric motor and issues an excitation signal to the coil of the relay, and detects that the traveling speed is equal to or higher than a set value and applies an excitation signal to the coil of the relay. A power steering control device consisting of safety measures to prevent 2. The power steering control device according to claim 1, wherein the semiconductor element is a transistor.