JP3642240B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor drive circuit for electric power steering for controlling steering of a vehicle.
[0002]
[Prior art]
In the electric power steering system that controls the steering of the vehicle, the control may be stopped by turning off the fail safe or the ignition switch. In particular, the braking stop by fail-safe is to secure the directionality of the vehicle by stopping the steering rotational movement by the electric motor and switching to manual operation by the driver. For example, Japanese Patent No. 2819473 proposes a device having a clutch that controls connection and disconnection to a steering system of an electric motor (motor). During the control of the electric motor, the clutch is disengaged by detecting a malfunction, thereby switching to manual operation.
[0003]
Japanese Patent No. 2715473 proposes a switch means (relay) interposed on the power supply side of an H-bridge circuit that is a drive circuit of an electric motor. Similarly, when this apparatus detects a malfunction, it not only turns off each switching element of the H bridge, but also cuts off the relay, thereby acting to cut off the power supply of the motor and switching to manual operation. The above configuration is shown together in FIG. In the figure, reference numerals 1 to 4 denote first to fourth switching elements, which are constituted by transistors or FETs. Reference numerals 1 to 4 denote drive circuits for driving an electric motor (motor) 5 and constitute an H-bridge circuit. Reference numeral 40 denotes switch means capable of supplying and shutting off the electric motor 5 and the power supply 8 of the H bridge circuit, and is constituted by a relay. When a malfunction is detected by an electronic circuit (not shown), when an ignition switch (not shown) is turned off, or when the vehicle speed becomes higher than a predetermined value, each switching element of the H blade ( In addition to deactivating 1-4), the relay 40 is also turned off to cut off the power supply. This action stops the driving of the electric motor. Reference numeral 41 denotes an electromagnetic clutch, which connects the electric motor to the steering system. When a malfunction of the system is detected by the electronic circuit, the electromagnetic clutch 41 is turned off to structurally separate the operation of the motor from the steering system.
[0004]
[Problems to be solved by the invention]
In the conventional apparatus having the above-described configuration, there is a problem in that both the switch means (relay) and the electromagnetic clutch must be provided in order to make the fail safe perfect. In other words, electrical measures and mechanical measures were required. On the other hand, in the system in which the electromagnetic clutch is omitted, even if the switch means (relay) is turned off when a failure occurs, a diode is inserted in each switching element (1-4) as shown in FIG. A current due to the induced electromotive force of the motor flows. Due to this action, there also arises a problem that a high load occurs when the driver operates the steering wheel.
[0005]
The present invention has been made to solve the above-described problems, and provides an electric power steering device that has an enhanced fail-safe function and can be easily switched to manual steering operation when a failure occurs. To do.
[0006]
[Means for Solving the Problems]
In the electric power steering apparatus according to the present invention, motor driving means configured by connecting two switching elements for each control terminal of the motor, and the motor is driven by the motor driving means to control the steering of the vehicle. In the electric power steering device, a power supply system line for supplying power to the motor driving means and at least three connection points between the two switching elements can be connected and disconnected at the same time. It is a feature.
[0007]
In the electric power steering apparatus according to the present invention, the power supply line for supplying power to the motor drive means, and the two switching elements connected to one control terminal of the motor The first switch means capable of simultaneously connecting and disconnecting at least three connection points, and the other two switching elements connected to the ground line of the power supply system line and the other control terminal of the motor. And a second switch means capable of simultaneously connecting and disconnecting at least three connection points.
[0008]
In the electric power steering apparatus according to the present invention, the motor driving means configured by connecting two switching elements for each control terminal of the electric motor, and the electric motor is driven by the electric motor driving means to steer the vehicle. In the electric power steering apparatus to be controlled, switch means capable of simultaneously connecting and disconnecting at least three connection points between the control terminal of the electric motor and two switching elements is provided.
[0009]
Furthermore, in the electric power steering apparatus according to the present invention, the motor driving means constituted by connecting two switching elements for each control terminal of the electric motor, the electric motor is driven by the electric motor driving means, and the steering of the vehicle the electric power steering apparatus for controlling the electric motor at the same time connecting the third connection point between the coil windings of respective phases of, is characterized in that was charged through the switching means capable of shutting off.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 shows a computer unit of an electric power steering apparatus in which an electric motor drive circuit is constituted by an H bridge circuit. Reference numerals 1 to 4 denote switching elements such as transistors or FETs, and the driving modes are performed in pairs of 1, 4, 2, and 3. An electric motor (motor) 5 is connected to a vehicle steering system (not shown) and steers the steering by the rotation of the motor. Reference numerals 6 and 7 denote switch means, which are constituted by relays. The relay 6 can simultaneously connect and disconnect the three connection points of the power supply line of the power supply 8 and the first and second switching elements 1 and 2. On the other hand, the relay 7 can simultaneously connect and disconnect the three connection points between the ground line and the third and fourth switching elements 3 and 4. Reference numeral 9 denotes an electronic circuit which controls the H bridge circuit and the relays 6 and 7.
[0011]
Next, the operation of the motor driving means configured as shown in FIG. 1 will be described. The electronic circuit 9 receives a signal from a sensor for detecting, for example, torque or steering angle of the steering operated by the driver, and calculates a control amount for driving the motor 5 so as to generate torque corresponding to the input signal. A control signal for driving the switching elements 1 to 4 is output. When the switching element is driven, a current flows through the motor to rotate, and the steering of the driver or the handle can be automatically rotated. In a normal state, the control signal of the electronic circuit 9 is output so that the relays 6 and 7 are connected. Here, when the switching elements 1 and 4 are turned on, the motor 5 rotates in one direction. Conversely, when the switching elements 2 and 3 are turned on, the motor 5 rotates in the reverse direction. Each of the switching elements 1 to 4 includes a diode connected in parallel or built in. This diode is a so-called flywheel diode and absorbs the back electromotive force induced in the motor coil when the switching element is switched from on to off.
[0012]
Further, the electronic circuit 9 has a function of detecting a system malfunction. For example, it is possible to detect a malfunction of the system by detecting the current of the motor 5, detecting a failure or disconnection of the sensors, or detecting a deviation between the calculated target control amount and the actual control amount. Is possible. With this defect detection function, the electronic circuit 9 not only turns off the switching element but also outputs a signal for shutting off the switch means 6 and 7. For example, when one of the switching elements (for example, the switching element 1) is turned on and then a signal for turning on the switching element 3 is output, a large current flows and the switching element, the electronic network, or the wiring may be destroyed. is there. However, this can be avoided by blocking one of the switch means 6 or 7.
[0013]
Next, the flow of current in the H bridge when the switching element is turned off will be described with reference to FIG. It is also possible to avoid a situation in which the steering is steered in the opposite direction of the driver's will or the load is increased and the driver needs excessive force to steer. For example, it is assumed that the first and fourth switching elements 1 and 4 are turned on and a current flows as shown by 12. Assuming that the fourth switching element is on-failed, a current flows through a diode as indicated by a broken line 13 even if the conventional relay 40 is turned off. Therefore, if the driver tries to turn the steering wheel in 12 directions, an excessive force is required, which hinders vehicle travel. In addition, when the driver turns the handle in the reverse direction, normal manual steering is possible, and a problem occurs that the load changes greatly due to forward and reverse rotation. On the other hand, when the first switching element 1 is on-failed, the current flows as shown by the broken line 14 and a similar problem occurs.
[0014]
As described above, the conventional relay has a problem in fail-safe, and for example, a mechanism for mechanically disconnecting by an electromagnetic clutch is required. However, in the present invention, by using the switch means that can cut off both the power supply system line and the switching element at the same time, there is no circuit through which the current flows as described above, and no current that becomes a steering load is generated. This has the effect of ensuring safety during vehicle travel.
[0015]
Embodiment 2. FIG.
Next, the second embodiment will be described with reference to FIG. The switch means 10 and 11 are interposed between the control terminal of the motor 5 and the switching element. With this configuration, since the motor and each switching element can be cut off, the switching element can be turned on, a motor coil short circuit, a power supply to the motor power supply, and a ground fault with the ground can be avoided. Thereby, there exists an effect which can implement | achieve a fail safe function easily.
[0016]
In the first and second embodiments, the switch means is described as using a special relay with three contacts, but a two-circuit simultaneous on / off control type relay (10a, 11a) is simply used. May be used. One contact in each of the two circuits is short-circuited and connected to the motor terminal, and the remaining one contact is connected to the switching element. This connection method is shown in FIG. Even if this type of relay is used, the same effect can be obtained, and there is no need to use a special relay.
[0017]
Embodiment 3 FIG.
Next, Embodiment 3 will be described with reference to FIG. Considering the case where the electric motor 21 is, for example, a brushless motor, the electric motor drive circuit has a configuration with 2 × 3 = 6 switching elements. Source coils 15, 17, 19 for supplying power and sink transistors 16, 18, 20 for pulling in ground are connected to each coil of the motor. In FIG. 4A, switch means 22, 23, and 24 are interposed between three connection points between each coil of the motor and each switching element. These switch means are three-contact simultaneous connection and interruption type relays. When a malfunction is detected by an electronic circuit (not shown), the current circuit can be disconnected by these relays. Therefore, no induced electromotive force is generated even if the driver rotates the handle after a system failure occurs, and the load does not change due to forward / reverse rotation. Moreover, it is possible to cope with a failure of the switching element, a short circuit of the motor coil, a power fault, and a ground fault.
[0018]
FIG. 4B is an apparatus in which a switch means 25 is interposed at a connection point between motor coils. Also in this case, since the current circuit is disconnected, no induced electromotive force is generated. However, in consideration of an on-failure of the switching element, it is necessary to install a switch means in the power supply line or the ground line to ensure fail-safety. Compared to FIG. 4A, there is an advantage that only two switch means are required.
[0019]
【The invention's effect】
Since the electric power steering apparatus of the present invention is configured as described above, the following effects can be obtained.
[0020]
According to the electric power steering apparatus of the present invention, the power supply system line for supplying power to the motor drive means and the switch means capable of simultaneously connecting and disconnecting at least three connection points between the two switching elements are provided. As a result, the switching circuit and other electronic circuit portions can be protected, and fail safe can be easily realized.
[0021]
Further, according to the electric power steering apparatus of the present invention, at least three connection points between the power supply line and the two switching elements among the power supply system lines for supplying power to the motor driving means are simultaneously connected and disconnected. First switch means that can be connected, and second switch means that can simultaneously connect and disconnect at least three connection points between the ground line and another two switching elements in the power supply system line. By interposing, the switching element and other electronic circuit parts and the motor can be protected, and further, the circuit through which the induced electromotive force of the motor is passed can be cut off, so that the steering steering load change can be prevented.
[0022]
Moreover, according to the electric power steering apparatus of the present invention, the switching element is provided by interposing the switch means capable of simultaneously connecting and disconnecting at least three connection points between the control terminal of the electric motor and the two switching elements. Other electronic circuit portions and the electric motor can be protected, and further, the circuit for flowing the induced electromotive force of the electric motor can be cut off, so that it is possible to prevent the steering steering load from changing.
[0023]
Furthermore, according to the electric power steering apparatus of the present invention, connecting a third connection point of each phase coil windings between the motor at the same time, by intervention instrumentation was a switch means capable of shutting off flow the induced electromotive force of the motor The circuit can be cut off .
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an internal motor drive circuit of an electric power steering apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a circuit diagram showing a current flow by a conventional device.
FIG. 3 is a circuit diagram showing an electric motor drive circuit according to a second embodiment.
FIG. 4 is a circuit diagram showing an electric motor drive circuit according to a third embodiment.
FIG. 5 is a circuit diagram showing an electric motor drive circuit according to a conventional apparatus.
[Explanation of symbols]
1-4 switching element, 5 motor (electric motor), 6, 7 switch means, 15-20 switching element, 21 electric motor, 22-25 switch means.

Claims (4)

In an electric motor drive means configured by connecting two switching elements for each control terminal of the electric motor, and an electric power steering device for driving the electric motor by the electric motor drive means to control the steering of the vehicle,
Electric power steering characterized in that a power supply system line for supplying power to the motor drive means and switch means capable of simultaneously connecting and disconnecting at least three connection points between the two switching elements are provided. apparatus. Of the power supply system line for supplying power to the motor drive means, a first that can simultaneously connect and disconnect at least three connection points between the power line and two switching elements connected to one control terminal of the motor . Similarly, the switching means of the first power supply system line can connect and disconnect simultaneously three connection points of the ground line and two other switching elements connected to the other control terminal of the motor . 2. The electric power steering apparatus according to claim 1, further comprising two switch means. In an electric motor drive means configured by connecting two switching elements for each control terminal of the electric motor, and an electric power steering device for driving the electric motor by the electric motor drive means to control the steering of the vehicle,
An electric power steering apparatus comprising switch means capable of simultaneously connecting and disconnecting at least three connection points between the control terminal of the electric motor and two switching elements. In an electric motor drive means configured by connecting two switching elements for each control terminal of the electric motor, and an electric power steering device for driving the electric motor by the electric motor drive means to control the steering of the vehicle,
At the same time connection, electric power steering GuSo location, characterized in that was charged through the switching means capable of shutting off the third connection point of each phase coil windings to each other of said electric motor.

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