JP4472584B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering device that assists a steering force, and more particularly to a relay protection circuit provided between an electronic circuit and a battery.

  Conventionally, an electric motor drive device as disclosed in Patent Document 1 is provided with a precharge circuit in order to prevent welding and damage of relay contacts. This precharge circuit reduces the potential difference from the power supply side by sufficiently raising the potential of this circuit from when the ignition is turned on until the relay is turned on, and avoids applying a large potential to the relay is doing.

Moreover, such an electric motor drive device detects a potential difference before and after the relay in order to detect a welding failure of the relay. That is, when the potential difference before and after the relay is less than or equal to a predetermined value in the relay OFF state (before the relay ON signal is output), the relay is determined to be fixed while the relay is fixed in the ON state. .
JP 2002-153086 A

  However, in the above prior art, a sufficient time is required from when the ignition is turned off until the potential stored in the precharge circuit is discharged. Therefore, before the potential of the precharge circuit is discharged again, When ignition is turned on and relay welding failure diagnosis is started, the potential difference before and after the relay is within the specified value even though the relay is normally turned off. was there.

The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a power steering apparatus including a relay protection circuit that prevents erroneous detection of relay abnormality.

In order to achieve the above-described object, in the present invention, the steering force of the steering mechanism coupled to the steered wheels is assisted, and the hydraulic power cylinder having the first hydraulic chamber and the second hydraulic chamber is connected to the first hydraulic chamber. A first passage, a second passage connected to the second hydraulic chamber, and a pair of discharge ports connected to the first passage and the second passage, and supply hydraulic pressure to the hydraulic power cylinder. A reversible pump, a motor connected to the reversible pump and rotating the reversible pump forward / reversely, a steering load detecting means for detecting or estimating a steering load of a steering wheel for steering control of the steered wheels, A communication path that communicates the first path and the second path, an electromagnetic switching valve that is provided in the communication path, and switches between communication and blocking of the communication path, power is supplied from a battery, and based on the steering load, Said A motor control circuit for controlling the chromatography data, a relay provided between said motor control circuit battery, a connecting circuit for connecting the said relay electromagnetic switching valve, is provided in the connection circuit, a charging circuit for charging the electric load supplied from the battery, after charging completion of the charging circuit, and a relay control circuit for energizing the relay, and the potential detecting means for detecting a potential difference between the relay sides, said potential detection means When the potential difference is within a predetermined value, the relay failure diagnosis means for determining that the relay has failed in energization, and the charge stored in the charging circuit before the relay failure diagnosis means starts relay failure diagnosis. Electromagnetic switching valve control means for energizing the electromagnetic switching valve so as to be consumed by the electromagnetic switching valve is provided.

Therefore, it is possible to provide a power steering device including a relay protection circuit that prevents erroneous detection of relay abnormality.

Hereinafter, the best mode for implementing the present onset Akira will be described with reference to the accompanying drawings.

[System configuration of relay protection circuit]
The first embodiment will be described with reference to FIGS. FIG. 1 is a system configuration diagram of an electric power steering apparatus equipped with the present relay protection circuit.

  When the driver steers the steering wheel 1, the pinion 3 is driven through the shaft 2, and the rack shaft 4 moves in the axial direction by a so-called rack and pinion mechanism to steer the front wheels. The shaft 2 is provided with a torque sensor 5 that detects the steering torque of the driver, and outputs a torque signal to the control unit 10.

  The rack shaft 4 is provided with a power steering mechanism that assists the movement of the rack shaft 4 according to the steering torque of the driver. The power steering mechanism includes a motor M, a bidirectional pump P, and a cylinder 6.

  The cylinder 6 is defined in a first cylinder chamber 61 and a second cylinder chamber 62 by a piston 63 provided so as to be movable in the axial direction. The first and second cylinder chambers 61 and 62 are connected to the bidirectional pump P via the first and second passages 21 and 22, and the rack shaft 4 is changed by changing the volume of the first and second cylinder chambers 61 and 62. Is moved in the axial direction. The first and second passages 21 and 22 are connected to the electromagnetic switching valve 20, respectively.

  The electromagnetic switching valve 20 is a normally-open fail-safe valve, which is opened when the system fails and communicates with the first and second passages 21 and 22 to introduce hydraulic oil from the high pressure side to the low pressure side. The communication of the second passages 21 and 22 is ensured to reduce the driver's steering load. Normally, it is excited by the control unit 10 and is closed. In addition, the electromagnetic switching valve 20 functions as a potential consumption unit that lowers the potential of the capacitor 200 in the control unit 10 and protects the relay 100 (see FIG. 2).

  The control unit 10 receives power supply from the battery E, and receives a switch signal from the ignition IGN (see FIG. 2), a vehicle speed signal from the vehicle speed sensor 7 and the like in addition to a torque signal from the torque sensor 5. A steering assist force is determined based on these various signals, and a command signal is output to the motor M.

  The motor M is a brushless motor having excellent inertia characteristics, and improves the steering feeling by improving the response of the bidirectional pump P having a high change frequency between forward and reverse rotation.

[Details of Control Unit]
FIG. 2 is a control block diagram of the control unit 10. The control unit 10 includes a potential detection unit 11, a precharge circuit 12, a motor control unit 13, a motor control circuit 14, a relay 100, a capacitor 200 (charging circuit), and a microcomputer 300.

  The relay protection circuit A of the present application includes the control unit 10, the electromagnetic switching valve 20, and the battery E.

  The relay 100 is provided between the motor control circuit 14 and the battery E, and the capacitor 200 is provided between the motor control circuit 14 and the relay 100. A potential detector 11 and a precharge circuit 12 are provided in parallel with the relay 100.

  An ignition IGN is provided upstream of the precharge circuit 12, and a series circuit of the ignition IGN and the precharge circuit 12 is in parallel with the relay 100. Further, an electromagnetic switching valve 20 outside the control unit 10 is provided in parallel with the capacitor 200.

  The potential detector 11 detects a potential difference ΔV on both sides of the relay 100. The detected potential difference ΔV is output to the relay failure diagnosis unit 340 and the precharge voltage diagnosis unit 350 of the microcomputer 300.

  The precharge circuit 12 is a booster circuit that boosts the voltage supplied to the capacitor 200. By increasing the voltage in advance, the potential on the downstream side of the relay is quickly increased.

  The capacitor 200 is a charging circuit that raises the potential downstream of the relay 100 to reduce the inrush current to the relay 100, and the charge Q accumulated in the capacitor 200 is consumed by energizing the electromagnetic switching valve 20. By using a capacitor, simplification of the configuration and protection of the relay 100 are achieved at the same time. The electric capacity C of the capacitor 200 is set to a very small value so that the electromagnetic switching valve 20 does not operate when the charge Q is consumed.

  The motor control unit 13 is provided downstream of the ignition IGN, calculates the target current I * of the motor M based on the torque signal T from the torque sensor 5 and the vehicle speed VSP from the vehicle speed sensor 7, and outputs it to the motor control circuit 14. . The motor control circuit 14 supplies a desired current to the motor M based on the target current I *.

(Details of microcomputer)
The microcomputer 300 includes a precharge circuit control unit 310, a relay control unit 320, an electromagnetic switching valve control unit 330, a relay failure diagnosis unit 340, and a precharge voltage diagnosis unit 350. The microcomputer 300 receives ON / OFF of the ignition signal and the potential difference ΔV between both sides of the relay 100, and performs control based on the input value.

  The precharge circuit control unit 310 controls the precharge circuit 12 based on the ON signal of the ignition IGN to boost the voltage to the capacitor 200. Relay control unit 320 energizes / cuts off relay 100 based on the IGN on / off signal.

  The relay failure diagnosis unit 340 diagnoses the failure of the relay 100 based on the potential difference ΔV from the potential detection unit 11. Since the upstream of the relay 100 is connected to the battery E and the downstream is connected to the ground GND via the precharge circuit 12, the capacitor 200, and the like, the potential difference ΔV becomes the voltage of the battery E when the relay 100 is off when the relay 100 is normal. .

  At this time, if the relay 100 is welded, the potential difference ΔV on both sides of the relay 100 is not detected even when the relay 100 is off. Therefore, before the relay control unit 320 outputs the ON signal of the relay 100 and when the potential difference ΔV is equal to or less than a predetermined value when the relay 100 is OFF, the relay failure diagnosis unit 340 diagnoses the relay 100 as abnormal.

  Further, the relay failure diagnosis unit 340 performs failure diagnosis within a predetermined time after the ON signal of the ignition IGN is output. Since the electric charge is accumulated in the capacitor 200 after the ignition is turned on, the failure diagnosis is performed before the potential of the capacitor 200 increases excessively by performing the failure diagnosis within a predetermined time.

  Precharge voltage diagnosis unit 350 diagnoses the voltage of precharge circuit 12 based on potential difference ΔV of relay 100 detected by potential detection unit 11, and outputs the diagnosis result to precharge circuit control unit 310. This is because the precharge circuit 12 and the relay 100 are in parallel, so that the precharge boost can be detected by the potential difference ΔV of the relay 100.

  The electromagnetic switching valve control unit 330 energizes the electromagnetic switching valve 20 based on the ON signal of the ignition IGN. That is, immediately after the ignition is turned on, the electromagnetic switching valve 20 is energized so that the potential of the capacitor 200 is reliably lowered before the failure diagnosis by the relay failure diagnosis unit 340 is started.

[Avoiding misjudgment of relay failure due to forced discharge to electromagnetic switching valve]
In a relay protection circuit in which the potential on the downstream side of the relay is sufficiently increased using a capacitor or the like, a sufficient time is required until the charge stored in the capacitor is discharged after the ignition is turned off.

  Therefore, when using a failure determination method of a type in which a relay abnormality is determined based on a potential difference before and after the relay in the off state, if the ignition is turned on again before the capacitor charge is discharged, the potential downstream of the relay is reduced by the charge accumulated in the capacitor. A phenomenon occurs in which the ignition is turned on again without being sufficiently lowered.

  Therefore, even though the relay is normally turned off, the potential difference before and after the relay hardly occurs, and the same state as the relay welding appears apparently. For this reason, there is a risk of detecting a relay abnormality by mistake.

  In order to avoid the possibility of this erroneous detection, the charge staying in the capacitor when the relay is turned off may be discharged quickly. In the present embodiment, the electromagnetic switching valve 20 is provided in parallel with the capacitor 200, and the electromagnetic switching valve 20 is energized by the electromagnetic switching valve control unit 330 based on the OFF signal of the relay 100. The charge Q is forcibly introduced into the electromagnetic switching valve 20 and is quickly discharged.

[Contrast of change with time in the conventional example and the embodiment of the present application]
FIG. 3 is a time chart of voltages upstream / downstream of the relay 100. The one-dot chain line is the upstream potential of the relay 100, and the solid line is the downstream potential. Further, since the relay downstream potential is the same in the conventional example and the present application from time t1 to t4, the relay downstream potential in the conventional example is indicated by a broken line only after time t4. Furthermore, the relay failure determination threshold value α is indicated by a two-dot chain line.

(Time t1)
At time t1, the ignition IGN is turned on. Since the upstream side of the relay 100 is directly connected to the battery E, the relay upstream potential is always E. On the other hand, since the downstream side of the relay 100 is connected to the capacitor 200, the charge of the battery E is first charged in the capacitor 200, and at this time, the relay downstream side potential does not rise.

(Time t2)
At time t2, the relay downstream side potential starts increasing. Charging of the capacitor 200 continues, and the relay downstream potential does not increase rapidly but gradually increases.

(Time t3)
At time t3, charging of the capacitor 200 is completed, and the potential on the downstream side of the relay rises to near the battery potential E. At this time, the connection of the relay 100 is turned on.

(Time t4)
At time t4, the ignition IGN is turned off and the relay 100 is also turned off. Accordingly, in this application, the electromagnetic switching valve 20 is energized, and the charge Q accumulated in the capacitor 200 is forcibly introduced into the electromagnetic switching valve 20. Therefore, in the present application, the electric charge of the capacitor 200 is quickly discharged, and the relay downstream potential is also rapidly reduced.
On the other hand, in the conventional example, the electric charge stored in the capacitor is reduced only by natural discharge. Therefore, the relay downstream potential connected to the capacitor hardly decreases.

(Time t5)
At time t5, in the present application, the relay downstream potential becomes equal to or less than the threshold value α, and the relay 100 is diagnosed as normal.
On the other hand, in the conventional example, the relay downstream potential does not fall below the threshold value α, so that a relay abnormality is erroneously detected even though the relay is normally turned off.

(Time t6)
At time t6, the ignition IGN is turned on again. In the conventional example, the discharge of the capacitor is insufficient, and the relay downstream potential still does not fall below the threshold value α.

(Time t7)
At time t7, the relay downstream potential of the present application starts to rise.

(Time t8)
At time t8, charging of the capacitor 200 is completed, the potential on the downstream side of the relay rises to near the battery potential E, and the connection of the relay 100 is turned on.

(Time t9)
After the time t9, it is the same as the time t4 to t8.

[Effect of the embodiment of the present application]
In this embodiment, the capacitor 200 and the electromagnetic switching valve 20 are provided in parallel on the downstream side of the relay 100, and the relay 100 is energized after the capacitor 200 is sufficiently charged. Further, based on the OFF signal of the relay 100, the electromagnetic switching valve control unit 330 sets the electromagnetic switching valve 20 to the energized state before the relay failure diagnostic unit 340 starts the failure diagnosis.

  As a result, the relay 100 can be energized after sufficiently reducing the potential difference between the upstream and downstream sides of the relay 100 during energization, and welding and damage of the relay contacts can be prevented.

  Further, it becomes possible to forcibly introduce the charge Q accumulated in the capacitor 200 before the failure diagnosis is started into the electromagnetic switching valve 20 and quickly discharge it. It is possible to avoid the occurrence of a state similar to that of the relay welding apparently as in the conventional example. Therefore, erroneous detection of relay abnormality can be prevented.

Furthermore, the discharge of the electric charge of the capacitor 200 is performed by exciting the electromagnetic switching valve 20 that is a fail-safe valve. Thereby, compared with the case where the motor M consumes electric charge, the electric charge of the capacitor 200 can be discharged quickly without causing sound vibration during use of electric charge and unnecessary change in hydraulic pressure.
(Other examples)

  The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to each embodiment, and the scope of the invention is not deviated. Design changes and the like are included in the present invention.

  Further, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.

(A) In the power steering apparatus according to claim 1,
The power steering device , wherein the charging circuit is a capacitor.

  Charging can be performed with a simple configuration, and damage to the relay contacts can be prevented.

(B) In the power steering device according to claim 1,
The electromagnetic switching valve control means, the power steering apparatus characterized by a energized the electromagnetic switching valve based on the ignition of the energizing signal.

By turning on the electromagnetic switching valve when the ignition is turned on, that is, immediately before the start of relay failure diagnosis, the potential of the charging circuit can be reliably lowered.

(C) In the power steering device according to claim 1,
The relay failure diagnosis means, after the ignition is turned on, the power steering apparatus characterized by performing a relay failure diagnosis within a predetermined time.

  Since the charging circuit is gradually charged after the ignition is turned on, the relay failure diagnosis can be performed before the potential of the charging circuit rises too much by performing the relay failure diagnosis within a predetermined time. .

(D) In the power steering device according to claim 1 ,
The electromagnetic switching valve is characterized in that the communication path is cut off in an excited state, and the communication path is in a communication state in a non-excited state.

  By setting the communication path to the communication state when the electromagnetic switching valve is in the non-excited state, even if power is not supplied to the electromagnetic switching valve and control becomes impossible in the event of a failure, the communication path is reliably connected. The driver's steering load can be reduced.

(E) In the power steering apparatus described in (d) above,
The electromagnetic switching valve control means puts the electromagnetic switching valve into an energized state based on an energization signal of an ignition signal.

  Even when the ignition is turned off immediately after the ignition is turned off, the potential in the charging circuit is consumed by the electromagnetic switching valve, so that it is possible to prevent erroneous determination in relay failure diagnosis.

It is a system block diagram of the electric power steering device which mounts this application relay protection circuit. It is a control block diagram of a control unit. It is a time chart of the electric potential in relay upstream / downstream.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Shaft 3 Pinion 4 Rack shaft 5 Torque sensor 6 Cylinder 7 Vehicle speed sensor 10 Control unit 11 Electric potential detection part 12 Precharge circuit 13 Motor control part 14 Motor control circuit 20 Electromagnetic switching valve 21 and 22 1st, 2nd path 61, 62 First and second cylinder chambers 63 Piston 100 Relay 200 Capacitor 300 Microcomputer 310 Precharge circuit control unit 320 Relay control unit 330 Electromagnetic switching valve control unit 340 Relay failure diagnosis unit 350 Precharge voltage diagnosis unit E Battery GND Ground IGN Ignition M Motor P Bidirectional pump

Claims (1)

A hydraulic power cylinder that assists the steering force of the steering mechanism coupled to the steered wheels and has a first hydraulic chamber and a second hydraulic chamber;
A first passage connected to the first hydraulic chamber;
A second passage connected to the second hydraulic chamber;
A reversible pump comprising a pair of discharge ports connected to the first passage and the second passage and supplying hydraulic pressure to the hydraulic power cylinder;
A motor connected to the reversible pump and rotating the reversible pump forward / reversely;
Steering load detection means for detecting or estimating a steering load of a steering wheel for steering control of the steered wheels;
A communication passage communicating the first passage and the second passage;
An electromagnetic switching valve that is provided in the communication path and switches between communication and blocking of the communication path;
A motor control circuit that is supplied with electric power from a battery and that drives and controls the motor based on the steering load;
A relay provided between said battery and said motor control circuit,
A connection circuit for connecting the relay and the electromagnetic switching valve;
Provided in the connecting circuit, a charging circuit for charging the electric load supplied from the battery,
A relay control circuit for energizing the relay after charging of the charging circuit ;
A potential detecting means for detecting a potential difference between both sides of the relay;
When the potential difference of the potential detection means is within a predetermined value, relay failure diagnosis means for determining that the relay is energized, and
Electromagnetic switching valve control means for energizing the electromagnetic switching valve so that the charge stored in the charging circuit is consumed by the electromagnetic switching valve before the relay failure diagnostic means starts relay failure diagnosis; A power steering apparatus comprising:

Images