JPH0215434B2 - - Google Patents

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 power relay 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 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 to drive the oil pump, when a large auxiliary force is required, the amount of electricity supplied to the motor is large. 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. It is known to sometimes provide a protection circuit that does not load the power transistor.

In a power steering system equipped with such a protection circuit, if the relay malfunctions and activates when it is not required, such as when driving at high speed, the bypass circuit causes a large current to flow to the motor, causing the oil pump to It happens that the rotation of the engine is suddenly increased to increase the assisting force. Furthermore, if the relay does not operate when it is required to operate, a high load may remain on the power transistor. In the former case, the steering suddenly becomes light while driving at high speed, which is extremely dangerous. In the latter case, the power transistor may be destroyed.

Therefore, if the power relay malfunctions, the amount of power supplied to the motor will be reduced regardless of the driving condition, and unnecessary high auxiliary force will be generated.
It is desirable to provide safety measures to prevent damage to the power transistor.

In response to such demands, the present invention aims to provide a power steering control device that reduces the amount of power supplied to the motor when a power relay fails to prevent the above-mentioned dangers and inconveniences. That is.

The power steering control device of the present invention is characterized in that it includes a safety means that detects a power relay failure and reduces the rotation speed of the motor to a low rotation speed when the relay failure occurs. That is, the control device of the present invention includes a power cylinder that assists the steering force, an oil pump that supplies pressure oil to this power cylinder, an electric motor that drives this oil pump, and adjusts the amount of power supplied to this electric motor. a semiconductor element that receives a speed signal corresponding to the running speed of the vehicle, a control means that issues a control signal to the semiconductor element to reduce the amount of power supplied as the running speed increases, and a contact that is connected in parallel to the semiconductor element. A power steering control device comprising a load detection means for detecting a high load state of the electric motor and emitting an excitation signal to the coil of the relay; The present invention is characterized in that the control means is provided with a safety means for inputting a correction signal for forcibly lowering the rotational speed of the motor.

Here, the security means include, for example, a detection unit that detects the operating state of a relay and determines whether the relay is malfunctioning by combining this with a signal that instructs the relay to operate or deactivate, and the output of this detection unit. and an output section that outputs the correction signal based on the correction signal.

The correction signal outputted here is a control signal inputted to the above-mentioned control means in order to set the rotation speed of the motor to, for example, the minimum rotational speed, and is inputted to the input terminal of a circuit before the power transistor, for example, a steering timer circuit. This is a signal used to lower the input to the power transistor.

According to the present invention, whenever the power relay fails, the amount of power supplied to the motor is reduced.
Even if a failure occurs while driving at high speed, the auxiliary power will not increase, and even if switching to the bypass circuit becomes impossible under heavy load, a large load will not be placed on the power transistor, reducing danger and power loss during driving. Destruction of the transistor 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 detects that the steering wheel 1 has been steered.
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 this embodiment has an input terminal of the comparator 25b of the steering timer circuit 25 of the basic circuit and the control circuit 2.
A power relay failure protection circuit 3 is connected between the contact point of the power relay Ry 8, the base of the transistor 30a of the current detection and relay drive circuit 30, and the output terminal of the speed-voltage conversion circuit 22.
1 is connected.

This power relay failure safety circuit 31 includes a constant voltage circuit 32 connected to the contacts of the power relay Ry.
One input is connected to the output of the high-speed detection circuit 33 connected to the output of the speed-voltage conversion circuit 22, and the output of the constant voltage circuit 32, and the other input is connected to the base of the transistor 30a of the current detection and relay drive circuit 30. The connected first AND circuit A1 has one input connected to the output of the high-speed detection circuit 33, and the second AND circuit A2 has the other input connected to the base, and the output of the first AND circuit A1. A first transistor 35 whose base is connected to the input terminal of the comparator 25b of the steering timer circuit 25 and whose collector is connected to the input terminal of the comparator 25b of the steering timer circuit 25; a second transistor 36 whose collector is connected to the terminal;
An alarm lamp 37 and a relay 38 connected to the collector of the second transistor 36 are provided. A normally closed contact 38a of this relay 38 is connected in series with a contact of a power relay Ry, and is connected between the collector and emitter of the power transistor 28a. Inside the control circuit 28 is a power relay Ry.
There is a relay coil Rc for operating the steering timer circuit 25, and a transistor 25a for inputting the steering signal _S2 from the steering sensor 21 to the input of the comparator 25b.

Hereinafter, the operation of the power steering control device according to the embodiment of the present invention will be explained in detail with reference to FIG.

Failures of the power relay Ry include cases in which it operates even though there is no command to operate the relay, supplying unnecessary large current to the motor, and cases in which it does not operate even though a command to operate the relay has been issued. First, there are cases where a large load is placed on the power transistor.

In the former case, the high-speed detection circuit 33 receives the signal from the output end point of the speed-voltage conversion circuit 22.
The output becomes H, and it detects that the relay does not need to operate, that is, a command to disable the relay is issued (no command to operate the relay), and connects one input to the second AND circuit A2. On the other hand, relay Ry is activated and enters the contact (n), so this is detected at the point and the constant voltage circuit 3
Let the output of 2 be L. The latter output L is inverted to H by the inverter 34, and the other input of the second AND circuit A2 also becomes H. Therefore, the second AND circuit A2
The output becomes H, turning on the second transistor 36 to lower the input of the comparator 25b of the steering timer circuit 25, and at the same time opening the normally closed contact 38a of the relay 38 to cut off the power supply by the power relay. As a result, the output of the comparator 25b decreases, and the output D of the steering timer circuit 25 becomes L.
By the operation of the two AND circuits a ₁ and a ₂ shown in FIG. 2, the input to the power transistor 28a becomes the output E from the idle duty generating circuit 27.
Therefore, the rotation speed of the motor 18 is reduced to the minimum rotation speed. Therefore, the rotation of the oil pump 14 is kept low, the generation of a large auxiliary force is prevented, and danger is prevented. At the same time, the alarm lamp 37 lights up to notify the driver of a dangerous fault condition. It should be noted that it can be determined from the level at the above point that the relay does not need to operate, if the detection level of the current transformer 29 is set so that it detects a relatively high load current.

In the latter case, the presence of a command to operate the relay is detected by current detection and the base of the transistor 30a of the relay drive circuit 30. This is detected at a point by the base voltage which has become H level due to the output of a Hall element or the like that detects the magnetic field of the current transformer 29, and one input of the first AND circuit A1 becomes H level. On the other hand, it is detected that the power relay Ry does not operate and is connected to the contact (m), and the output of the constant voltage circuit 32 becomes H.
The other input of the first AND circuit A1 also becomes H. As a result, the output of the first AND circuit A1 becomes H, turning on the first transistor 35 and lowering the input of the comparator 25b of the steering timer circuit 25 as described above. Therefore, the input level to power transistor 28a is lowered, the load on power transistor 28a is reduced, and destruction is prevented.

As is clear from the above description, according to the power steering control device of the present invention, even if either of the above two types of failures occurs, the level of input to the power transistor is lowered, thereby preventing dangerous conditions or
A large load on the power transistor is prevented.

Note that in the above embodiment, the motor rotation speed is reduced to the idle rotation speed when a failure occurs.
In the event of a failure, the power supply to the motor may be cut off unconditionally to stop the motor. Also, 2
Of these types of failures, the alarm lamp is turned on only in the case of a dangerous situation where the assist force is increased when driving at high speed, but an alarm is also turned on in the case of the other type of failure to notify the relay failure. You can do it like this. Note that these alarms are not necessarily necessary, and there is no problem in practical use if the alarm is not provided and the input to the power transistor is simply lowered.

It goes without saying that the specific configuration of the above embodiment can be modified in various ways, for example, two
Although a configuration using an AND circuit is preferable in practice, it is of course possible to replace it with other well-known detection means or miscalculation means. Also,
Regarding the configuration for detecting activation and deactivation commands to relays in circuits that detect relay failures,
Instead of detecting the levels at the points, for example, the input level to the power transistor may be detected.

[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 failure protection 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...Transistor, 31...Power relay failure protection circuit,
32... Constant voltage circuit, 33... High speed detection circuit, 3
7... Alarm lamp, a ₁ , a ₂ , A1, A2...
AND circuit.

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 a load detection means that detects a failure of the relay and forces the control means to reduce the rotation of the motor when the relay fails. A power steering control device consisting of a safety means that inputs a correction signal for controlling the power steering. 2. The safety means includes a detection section consisting of a first detection section that detects the operating state of the relay and a second detection section that detects an instruction to activate or deactivate the power relay, and an output of this detection section. 2. The power steering control device according to claim 1, further comprising an output section that outputs the correction signal based on the power steering control device.