JP3663890B2 - Control device for electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly to the configuration of its control circuit.
[0002]
[Prior art]
In an electric power steering apparatus for a vehicle, a steering torque generated in a steering shaft by detecting a steering handle is detected, and a motor that generates a steering assist force is driven based on the detection signal. Some are configured to drive a steering mechanism through an attached reduction mechanism.
[0003]
FIG. 3 shows an example of a control circuit of a conventional electric power steering apparatus. The control circuit is constituted by the CPU 11, the steering torque detected by the torque sensor 14, the steering rotation speed detected by the steering rotation sensor 16, and others. The steering assist force command value is determined on the basis of this signal, and the motor drive circuit 21 is controlled based on the determined steering assist force command value to drive the motor.
[0004]
The motor drive circuit 21 is connected to the battery 13 via a normally open contact 18a of a ferrule 18, and when the ignition key 12 is detected to be on, the relay contact 18a is closed. It is configured to be fed. The reason why the relay relay is interposed is to protect the ignition key contact from a large current flowing in the motor driving circuit and for other safety control. The fail relay 18 is connected in series to a transistor TR that is on / off controlled by a signal output from the CPU 11, and is controlled by the CPU 11.
[0005]
The circuit composed of the resistors R1 and R2 and the diodes D1 and D2 is a circuit for detecting the ignition key 12, and the circuit composed of the resistors R3 and R4 and the diodes D3 and D4 is a node. A circuit for detecting the on / off state of the normally open contact 18a and detecting the voltage supplied to the motor drive circuit 21.
[0006]
Reference numeral 23 denotes a motor for supplying a steering assist force to the steering system, reference numeral 24 denotes a motor current detection circuit for detecting motor current, reference numeral 14 denotes a torque sensor for detecting steering torque, and reference numeral 16 denotes a steering rotational speed detector. , 19 is a constant voltage circuit for supplying a constant voltage Vcc to the CPU 11 and other control systems.
[0007]
In this type of electric power steering apparatus, a motor drive circuit 21 in which semiconductor elements FET1 to FET4 are H-bridge connected is used for the motor drive circuit, and output from the CPU based on the steering assist force command value. The gate drive circuit 22 is driven based on the gate drive command signal, and the semiconductor elements of the motor drive circuit are driven by a pulse width modulation signal (PWM signal) having a predetermined time width corresponding to the gate drive command signal. The motor 23 is driven by intermittent on / off control, and a steering assist force corresponding to the detected steering torque is generated.
[0008]
Thus, noise is generated when the motor driving circuit is operating to drive the motor by intermittently turning on / off the semiconductor elements. Therefore, in general, a noise removing circuit in which a large-capacitance capacitor C1 is inserted in parallel with the motor driving circuit 21 is incorporated in order to remove noise (utility model registration No. 2506269, actual (See Kaihei 6-27433).
[0009]
[Problems to be solved by the invention]
In general, a capacitor having a very large capacity is used as a capacitor incorporated in the motor driving circuit in order to enhance the effect of noise removal. However, when a large-capacity capacitor is used, if the ignition key is turned on and the relay contact is closed to set the motor drive circuit to the operating state, the motor drive circuit is inserted in parallel at that moment. In addition, since a large charging current flows through the capacitor, there is a possibility that the relay contact may be welded.
[0010]
In order to prevent welding of the relay contact due to the inrush current that occurs at the moment when the relay contact is closed, a resistor is connected to both ends of the normally open contact, and a small current is always applied to the capacitor even when the contact is open. In this method, the battery voltage is always applied to the contact on the load side, so when starting the control circuit with the ignition key turned on, the relay contact is welded. There was an inconvenience that the failure could not be detected.
[0011]
The present invention provides a control device for an electric power steering apparatus that solves the above-described problems and precharges a capacitor after turning on an ignition key and can detect welding of a relay contact. Objective.
[0012]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the invention according to claim 1 is directed to an electric motor, control means for controlling driving of the electric motor, and motor driving for driving the electric motor. A control device for an electric power steering apparatus that controls driving of the electric motor based on the detected steering torque and applies auxiliary torque to the steering system. An on / off detection circuit for detecting, a capacitor connected in parallel to the motor driving circuit, and a normally open contact disposed on a power feeding circuit for supplying power from the battery to the motor driving circuit A relay driving circuit for driving the relay, and a pre-charging circuit connected in parallel to both ends of the normally open contact of the relay, and the control means turns on an ignition key. When the state is detected, after confirming that the relay contact is not welded, the precharging of the capacitor by the precharging circuit is started, and the relay driving circuit is operated after waiting for the completion of the precharging. And controlling the normally-open contact to close.
[0013]
The confirmation of the welding / non-welding state of the relay contact by the control means is confirmed based on the terminal voltage on the load side of the relay contact when the ON state of the ignition key is detected. To do.
[0014]
The preliminary charging circuit includes a series-connected resistance element for setting a charging current and an opening / closing means, and the opening / closing means is controlled by the control means.
[0015]
Further, the control means may control to stop the control operation by the control means when the welding state of the relay contact is confirmed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing the circuit configuration of the control device. The same components as those of the conventional control circuit shown in FIG. 3 are given the same reference numerals so that the correspondence with the conventional circuit can be easily understood. In FIG. 1, 11 is a CPU, 12 is an ignition key, 13 is a battery, 18 is a ferrule relay provided with a normally open contact 18a, 19 is a constant voltage circuit for supplying a constant voltage to the control system, 21 Is a motor drive circuit constituted by connecting H-bridges of field effect transistors FET1 to FET4, 22 is a gate drive circuit for driving the gates of FET1 to FET4, and 23 is a steering assisting force for the steering system. A motor 24 is a motor current detection circuit for detecting a motor current.
[0017]
The constant voltage circuit 19 supplies a constant voltage Vcc to the CPU 11 and other control systems, and is connected to the battery 13 via the ignition key 12.
[0018]
A constant voltage Vcc is supplied to the CPU 11 from a constant voltage circuit 19, and an output of a torque sensor 14 for detecting a steering torque and an output of a steering rotational speed detector 16 are respectively input to its input ports. And 17 are input.
[0019]
A circuit composed of resistors R1 and R2 and diodes D1 and D2 connected to the input port of the CPU 11 is a key-on detection circuit for detecting the on / off state of the ignition key 12, and the ignition. When the key 12 is turned on, the voltage of the battery 13 is inputted to the input port of the CPU 11 from the middle point of the resistors R1 and R2 connected in series, and the ignition key 12 is turned on.
[0020]
The circuit comprising resistors R3 and R4 and diodes D3 and D4 connected to the input port of the CPU 11 detects and monitors the on / off state of the normally open contact 18a. A voltage detection circuit that detects the voltage supplied to the drive circuit 21 and is connected to the load side of the normally open contact 18a. When the contact 18a is turned on, the voltage of the battery 13 is connected in series. A voltage input to the input port of the CPU 11 from the middle point of R3 and R4 and supplied to the motor drive circuit 21 is detected.
[0021]
The output port of the CPU 11 is connected to a gate circuit 22 and a relay circuit constituted by a transistor TR, a resistor R5 and a relay 18 connected in series.
[0022]
A large-capacitance electrolytic capacitor C1 and a motor drive circuit 21 are connected to the load side of the normally open contact 18a of the ferrule 18, and the normal open contact 18a includes a contact. In parallel with both ends of 18a, a precharge circuit 25 in which a resistor R7 and a switching element SWP are connected in series for precharging the electrolytic capacitor C1 is connected, and the switching element SWP is on / off controlled by the CPU 11.
[0023]
The switching element SWP of the precharge circuit 25 may be a relay having a normally open contact, or may be constituted by a semiconductor element. The resistor R7 is a resistor for setting a charging current when pre-charging the electrolytic capacitor C1, and a resistor having a relatively high resistance value is used so that the motor is not driven. .
[0024]
The resistor R6 is a resistor for detecting the motor current flowing to the motor through the FET1 to FET4. The potential difference between both ends of the resistor R6 is detected by the motor current detection circuit 24, and the detected motor current value is Input to the CPU 11 and motor current feedback control is performed.
[0025]
Next, the control operation of the above configuration executed by the CPU 11 will be described with reference to the block diagram of the control device shown in FIG. 1 and the flowchart shown in FIG.
[0026]
When the ignition key 12 is in the OFF state, the normally open contact 18a of the relay 18 and the switching element SWP of the precharge circuit 25 are in the open state.
[0027]
When the ignition key 12 is turned on, the on state of the ignition key 12 is detected by a key detection circuit composed of resistors R1, R2 and diodes D1, D2, and a detection signal (battery voltage VB) is detected. ) Is input to the CPU 11. The CPU 11 waits for the input of the detection signal, and when it is input, determines that it is activated (step P11).
[0028]
The voltage VL on the load side (electrolytic capacitor C1 and motor drive circuit 21 side) of the normally open contact 18a is read by a voltage detection circuit comprising resistors R3 and R4 and diodes D3 and D4 (step) P12), and is compared with a predetermined voltage value V0 set in advance (step P13). If VL> V0, it means that an abnormal voltage appears on the load side of the normally open contact 18a. Therefore, it is determined that the contact 18a is welded (step P19), and the control operation of the control device is performed. Is stopped (step P20), and the process is terminated.
[0029]
If it is determined in step P13 that VL> V0 is not satisfied, it is determined that the contact 18a is not welded. Therefore, the switching element SWP of the precharge circuit 25 is turned on to start precharging the electrolytic capacitor C1 (step P14). .
[0030]
The voltage VL on the load side (electrolytic capacitor C1 and motor drive circuit 21 side) of the normally open contact 18a is read by a voltage detection circuit comprising resistors R3 and R4 and diodes D3 and D4 (step) P15), it is determined whether or not the voltage VL is substantially equal to the battery voltage VB (step P16). If a voltage substantially equal to the battery voltage VB is detected, it means that the precharging of the electrolytic capacitor C1 has been completed. Therefore, the fail relay 18 is turned on, the normal open contact 18a is closed, and the precharger is closed. The switching element SWP of the circuit 25 is turned off (steps P17 and P18), and the process is terminated.
[0031]
Since the motor drive circuit is set to the operating state by the above processing, normal motor drive control is performed thereafter. That is, the CPU 11 outputs a PWM signal having a predetermined time width corresponding to the steering assist amount determined based on the steering torque detected by the torque sensor 14 and the steering rotation speed detected by the steering rotation number detector 16, and the like. A data rotation direction signal is output to the gate drive circuit 22. The gate drive circuit 22 drives the FET1 to FET4 of the motor drive circuit 21 to rotate the motor 23 to assist steering.
[0032]
【The invention's effect】
As described above, the control device for the electric power steering apparatus according to the present invention confirms that the relay contact is not welded when the ignition key ON state is detected, and then applies the precharge circuit to the capacitor. The preliminary charging is started, and the relay driving circuit is operated after waiting for the completion of the preliminary charging to control the normally open contact.
[0033]
As a result, even after the ignition key is turned on, a large capacity capacitor for noise removal is preliminarily charged with a relatively small current, and the motor drive circuit is set to the operating state after the charging is completed. Therefore, unlike the conventional device, when the ignition key is turned on, a large current does not flow to the capacitor at that moment, and it is possible to prevent the possibility of failure such as welding of the relay contact. Can do.
[0034]
Further, when the ignition key is turned on, it is possible to detect whether or not the contact of the relay relay is welded, and in the case of welding, it is possible to immediately stop the control operation of the control device. As a result, accidents based on contact welding can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of a control device according to an embodiment of the present invention.
FIG. 2 is a flowchart explaining the control operation of the control device.
FIG. 3 is a diagram showing a configuration of a control circuit of a conventional electric power steering apparatus.
[Explanation of symbols]
11 CPU
12 Ignition key
13 Battery 14 Torque sensor 16 Steering rotation sensor 18 Fail relay
18a normally open contact 19 constant voltage circuit 21 motor drive circuit 22 gate drive circuit 23 motor 24 motor current detection circuit 25 precharge circuit C1 electrolytic capacitor SWP switching element

Claims (4)

An electric motor, control means for controlling the driving of the electric motor, and a motor drive circuit for driving the electric motor, and the electric motor based on the detected steering torque. In the control device for the electric power steering apparatus that controls the driving of the steering system and applies the auxiliary torque to the steering system,
An on / off detection circuit for detecting an on / off state of the ignition key;
A capacitor connected in parallel to the motor drive circuit;
A relay having a normally open contact disposed on a power supply circuit for supplying power to the motor drive circuit from a battery;
A relay driving circuit for driving the relay;
A precharging circuit connected in parallel to both ends of the normally open contact of the relay;
When the on state of the ignition key is detected, the control means confirms that the relay contact is not welded and then starts precharging the capacitor by a precharging circuit, and finishes precharging. A control device for an electric power steering apparatus, wherein the control is performed so that the relay drive circuit is activated to close the normally open contact. The confirmation of the welding / non-welding state of the relay contact by the control means is confirmed based on the terminal voltage on the load side of the relay contact when the ON state of the ignition key is detected. 2. A control device for an electric power steering apparatus according to claim 1. 2. The electric power steering apparatus according to claim 1, wherein the preliminary charging circuit includes a series-connected resistance element for setting a charging current and an opening / closing means, and the opening / closing means is controlled by the control means. Control device. 2. The control device for an electric power steering apparatus according to claim 1, wherein the control means stops the control operation by the control means when the welding state of the relay contact is confirmed.

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