JP2007083772A - Steering gear for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent formation of a closed loop between a motor and a motor driving circuit when a short circuit occurs in the motor driving circuit, to avoid heating generation, and to reduce power consumption. <P>SOLUTION: This electric power steering gear is provided with a latching relay 12. The latching relay 12 is provided with a permanent magnet, and usually maintains the condition wherein a contact point for connecting/disconnecting a connection point 20U of a series circuit 10U to/from a U-phase coil 11U and a contact point 14V for connecting/disconnecting a connection point 20V of a series circuit 10V to/from a V-phase coil 11V are closed. When a short circuit failure occurs in the motor driving circuit, the contact points 14U and 14V are opened to disconnect between the connection point 20U of the series circuit 10U and the U-phase coil 11U and between the connection point 20V of the series circuit 10V and the V-phase coil 11V. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus such as an electric power steering apparatus.

For example, in an electric power steering apparatus, a three-phase brushless motor is employed as a drive source, and the three-phase brushless motor is controlled based on the operation of the steering wheel. Force is generated from a three-phase brushless motor.
A three-phase brushless motor is generally driven by a three-phase bridge circuit. The three-phase bridge circuit is connected between a battery mounted on the vehicle and a ground, and includes a series circuit of two switching elements in parallel corresponding to each phase of the three-phase brushless motor. Each series circuit is connected to a corresponding phase winding of the three-phase brushless motor at a connection point of two switching elements. When a PWM (Pulse Width Modulation) signal is applied to the switching elements of each series circuit, the switching elements are turned on / off at the duty of the PWM signal, and a current corresponding to the duty is transferred from the three-phase bridge circuit to the three-phase brushless motor. Supplied. Therefore, by creating a PWM signal with a duty corresponding to the steering wheel operation, it is possible to supply a current of a current value corresponding to the steering wheel operation to the three-phase brushless motor, and as a result, to the steering wheel operation A corresponding steering assist force can be generated from the three-phase brushless motor.

  In such a configuration, when a short circuit failure occurs in the switching element in the motor drive circuit, an overcurrent is supplied from the battery to the motor drive circuit, and heat is generated on the power supply path from the battery to the drive circuit and other switching elements. There is a risk of problems such as destruction. Therefore, when a short circuit failure of the switching element occurs, as a fail safe, the power supply path from the battery to the motor drive circuit is cut, and the power supply from the battery to the motor drive circuit is stopped. .

  However, when a short circuit failure occurs in the switching element, a closed loop including at least one phase winding of the three-phase brushless motor may be formed. When this closed loop is formed, when the steering wheel is operated with no power supplied from the battery to the three-phase bridge circuit, an induction current is generated in the three-phase brushless motor, and the steering wheel becomes extremely heavy. Or uneven steering wheel weight (torque ripple).

In order to cope with this problem, in the conventional electric power steering apparatus, a normally open relay is interposed between the three-phase bridge circuit and the three-phase brushless motor. And usually, by supplying a driving current to the relay, the relay is turned on, and when a short circuit failure of the switching element occurs, the supply of the driving current to the relay is stopped, and the relay is turned off, A closed loop is prevented from being formed between the three-phase bridge circuit and the three-phase brushless motor.
JP 2004-106664 A

However, in the conventional configuration, there is a problem that the driving current must be continuously supplied to the relay while the switching element is not short-circuited, so that heat is generated from the relay and power consumption is large.
Therefore, an object of the present invention is to avoid the problem of heat generation while preventing a closed loop from being formed between the motor and the motor drive circuit when a short circuit failure occurs in the motor drive circuit. It is possible to provide a vehicle steering apparatus that can reduce power consumption.

  In order to achieve the above object, the invention according to claim 1 is directed to a vehicle steering apparatus that applies a steering force to the steered wheels (3) of the vehicle in accordance with an operation of the operation member (1). A motor (M) for generating, a motor drive circuit (4) for driving the motor, and a permanent magnet interposed between the motor and the motor drive circuit, and by the magnetic force of the permanent magnet A vehicle steering apparatus comprising: switch means (12) for maintaining a closed state of contacts (14U, 14V) for connecting / disconnecting the motor and the motor drive circuit.

In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
According to this configuration, the switch means is interposed between the motor and the motor drive circuit, and when the short circuit failure occurs in the motor drive circuit, the contact of the switch means is opened, thereby the motor and the motor drive circuit. It is possible to prevent a closed loop from being formed between the two. Therefore, it is possible to prevent an induction current from being generated in the motor when the operation member is operated in a state where the supply of electric power to the motor drive circuit is interrupted. As a result, it is possible to prevent the operation member from becoming extremely heavy or unevenness in the weight of the operation member. In addition, since it is not necessary to supply power to the switch means during a period when no short circuit failure has occurred, the amount of power consumption can be reduced. Moreover, the problem of heat generation can be avoided.

  According to a second aspect of the present invention, there is provided a motor for generating a steering force in a vehicle steering apparatus that applies a steering force to the steered wheels (3) of the vehicle in response to an operation of the operation member (1). M), a motor drive circuit (4) for driving the motor, contacts (17U, 17V) for connecting / disconnecting the motor and the motor drive circuit, and energizing the contacts in the opening direction When the power is supplied to the biasing means (18U, 18V) and the power is not supplied, the contact is maintained in a closed state against the biasing force of the biasing means. And an actuator (21) for releasing

  According to this configuration, in a state where the contact is maintained in the closed state by the actuator, the motor and the motor drive circuit are connected, power can be supplied from the motor drive circuit to the motor, and a short circuit failure occurs in the motor drive circuit. When this occurs, it is possible to prevent the closed loop from being formed between the motor and the motor drive circuit by supplying electric power to the actuator, releasing the closed state, and opening the contact. Therefore, it is possible to prevent an induction current from being generated in the motor when the operation member is operated in a state where the supply of electric power to the motor drive circuit is interrupted. As a result, it is possible to prevent the operation member from becoming extremely heavy or unevenness in the weight of the operation member. In addition, since it is not necessary to supply power to the actuator during a period when no short circuit failure has occurred, the amount of power consumption can be reduced. Moreover, the problem of heat generation can be avoided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram schematically showing the configuration of an electric power steering apparatus according to an embodiment of the present invention. This electric power steering apparatus is used by being mounted on a vehicle, and drives an electric motor M composed of a three-phase brushless motor in accordance with an operation of a steering wheel 1 as an operation member, and uses the electric power generated by the electric motor M. By transmitting to the steering mechanism 2, steering by the steering mechanism 2 (turning of the steered wheels 3 of the vehicle) is assisted.

  This electric power steering apparatus includes a motor drive circuit 4 for supplying a drive current to the electric motor M, a microcomputer 5 as a PWM signal generation means including a CPU, a RAM and a ROM, and each phase current value calculation means, a steering, A torque sensor 6 for detecting the steering torque applied to the wheel 1 and a vehicle speed sensor 7 for detecting the traveling speed (vehicle speed) of the vehicle are provided.

The motor drive circuit 4 is composed of a three-phase inverter circuit, and a series circuit 10U of switching elements (power MOSFETs) 8U and 9U and a switching element 8V and 9V between a power source (for example, an in-vehicle battery) Vb and a ground G. A series circuit 10V and a series circuit 10W of switching elements 8W and 9W are connected in parallel.
The series circuit 10U of the switching elements 8U and 9U is connected to the U-phase winding 11U of the electric motor M at a connection point 20U between the two switching elements 8U and 9U. The series circuit 10V of the switching elements 8V and 9V is connected to the V-phase winding 11V of the electric motor M at the connection point 20V of the two switching elements 8V and 9V, and the series circuit 10W of the switching elements 8W and 9W. Is connected to the W-phase winding 11W of the electric motor M at a connection point 20W between the two switching elements 8W and 9W.

  The microcomputer 5 receives an output signal from the torque sensor 6 and an output signal from the vehicle speed sensor 7. The microcomputer 5 sets the target current value of the current that should flow through the phase windings 11U, 11V, 11W of the electric motor M based on the output signals of the torque sensor 6 and the vehicle speed sensor 7. On the other hand, the microcomputer 5 performs PWM (Pulse) for each phase of the electric motor M based on the deviation between each phase target current value and each phase current value actually flowing through each phase winding 11U, 11V, 11W. Width Modulation) signal is generated, and each phase PWM signal is input to the switching elements of the series circuits 10U, 10V, 10W of the motor drive circuit 4. As a result, the switching elements of the series circuits 10U, 10V, and 10W of the motor drive circuit 4 are turned on / off according to the duty of the PWM signal input to them. As a result, a current corresponding to the steering torque and the vehicle speed flows to the electric motor M, and a driving force (steering force) corresponding to the steering torque and the vehicle speed is generated from the electric motor M.

  Further, in this electric power steering apparatus, the connection point 20U of the series circuit 10U of the motor drive circuit 4 and the U-phase winding 11U of the electric motor M and the connection point 20V of the series circuit 10V of the motor drive circuit 4 are electrically connected. A latching relay 12 for disconnecting from the V-phase winding 11V of the motor M and a relay drive circuit 13 for driving the latching relay 12 are provided.

  The latching relay 12 includes a permanent magnet. Normally, the contact 14U for connecting / disconnecting the connection point 20U of the series circuit 10U and the U-phase winding 11U and the connection point 20V of the series circuit 10V by the magnetic force of the permanent magnet. Is a relay that maintains the closed state of the contact 14V that connects / disconnects to the V-phase winding 11V, and that is switched on / off by a pulse input and self-maintains the state. When a short circuit failure occurs in the switching elements 8U, 9U, 8V, 9V, 8W, and 9W of the motor drive circuit 4 and an overcurrent flows through the motor drive circuit 4, the microcomputer 5 uses the power supply Vb as a fail safe. The power supply to the motor drive circuit 4 is cut off and the latching relay 12 is operated via the relay drive circuit 13 to open the contacts 14U and 14V, and the connection point 20U of the series circuit 10U and the U-phase winding 11U And between the connection point 20V of the series circuit 10V and the V-phase winding 11V.

  This prevents a closed loop from being formed between the electric motor M and the motor drive circuit 4 when a short circuit failure occurs in the switching elements 8U, 9U, 8V, 9V, 8W, 9W of the motor drive circuit 4. can do. Therefore, it is possible to prevent an induction current from being generated in the electric motor M when the steering wheel 1 is operated in a state where the supply of power from the power source Vb to the motor drive circuit 4 is interrupted. As a result, it is possible to prevent the steering wheel 1 from becoming extremely heavy or causing unevenness (torque ripple) in the weight of the steering wheel 1.

Further, since it is not necessary to supply power to the latching relay 12 during a period in which the short-circuit failure of the switching elements 8U, 9U, 8V, 9V, 8W, and 9W has not occurred, the power consumption can be reduced. Further, heat generation from the latching relay 12 can be suppressed.
In this embodiment, the configuration using the latching relay 12 is taken up. However, instead of the latching relay 12, a configuration as shown in FIG.

  FIG. 2 is a perspective view showing a configuration that can be employed in place of the latching relay 12. The configuration shown in FIG. 2 includes a drive circuit side wiring 15U connected to the connection point 20U of the series circuit 10U of the motor drive circuit 4, a motor side wiring 16U connected to the U phase winding 11U of the electric motor M, Contact 17U for connecting / disconnecting drive circuit side wiring 15U and motor side wiring 16U, drive circuit side wiring 15V connected to connection point 20V of series circuit 10V of motor drive circuit 4, and V-phase winding of electric motor M A motor side wiring 16V connected to the line 11V, and a contact point 17V for connecting / disconnecting the drive circuit side wiring 15V and the motor side wiring 16V are provided.

The contacts 17U and 17V are made of a thin metal plate, and one end portions thereof are opposed to the drive circuit side wirings 15U and 15V from above. The other ends of the contacts 17U and 17V are fixed to the motor side wirings 16U and 16V via spring members 18U and 18V as urging means, respectively.
The spring members 18U and 18V themselves have a biasing force that elastically biases the contacts 17U and 17V in the opening direction (the direction in which the contacts 17U and 17V are separated from the drive circuit side wirings 15U and 15V, respectively). Bently formed in a letter shape and integrally provided with urging portions 19U and 19V for urging the contacts 17U and 17V further in the opening direction. Thereby, in the state where no external force is applied to the contacts 17U and 17V, the contacts 17U and 17V are opened by the biasing force of the spring members 18U and 18V, respectively, and the drive circuit side wirings 15U and 15V and the motor side wirings 16U and 16V are connected. Each space is cut.

Further, the structure shown in FIG. 2 includes a stopper 20 installed between the contacts 17U and 17V, and an actuator for maintaining the contacts 17U and 17V in a closed state by the stopper 20 and releasing the state. The linear motion solenoid 21 is provided.
The direct acting solenoid 21 is configured such that the movable portion 22 protrudes from the main body in a state where no electric power is supplied, and the movable portion 22 retracts to the main body side when electric power is supplied. Under normal conditions, the movable portion 22 of the linear solenoid 21 comes into contact with the stopper 20 from the side opposite to the contacts 17U and 17V, and the upward movement of the stopper 20 is restricted, so that the contacts 17U and 17V are The state of contact with the drive circuit side wirings 15U and 15V is maintained. When an overcurrent flows through the motor drive circuit 4 (see FIG. 1), the direct acting solenoid 21 is actuated (driven) as a fail safe, and the movable portion 22 of the direct acting solenoid 21 is separated from the stopper 20. The Accordingly, the upward movement of the stopper 20 is allowed, and the contacts 17U and 17V are separated from the drive circuit side wirings 15U and 15V by the urging force of the spring members 18U and 18V. As a result, the drive circuit side wirings 15U and 15V and the motor side wirings 16U and 16V are disconnected.

  Even in the configuration shown in FIG. 2, when a short circuit failure occurs in the switching elements 8U, 9U, 8V, 9V, 8W, and 9W (see FIG. 1) of the motor drive circuit 4, the electric motor M and the motor drive circuit 4 It is possible to prevent a closed loop from being formed between the two. Further, since it is not necessary to supply power to the direct acting solenoid 21 during a period in which the short-circuit failure of the switching elements 8U, 9U, 8V, 9V, 8W, and 9W has not occurred, the power consumption can be reduced. Further, there is no possibility of causing a problem of heat generation.

  While the two embodiments of the present invention have been described above, the present invention can also be implemented in other forms. For example, in the above embodiment, when a short circuit failure occurs in the switching elements 8U, 9U, 8V, 9V, 8W, 9W of the motor drive circuit 4, the connection point 20U of the series circuit 10U and the U-phase winding 11U Although the configuration in which the connection point 20V between the series circuit 10V and the V-phase winding 11V is disconnected is taken as an example, the connection point 20V between the series circuit 10V and the V-phase winding 11V and the series circuit 10W The connection point 20W and the W-phase winding 11W may be disconnected, or the connection point 20W and the W-phase winding 11W of the series circuit 10W and the connection point 20U and the U-phase winding 11U of the series circuit 10U. May be cut off. Further, between the connection point 20U of the series circuit 10U and the U-phase winding 11U, between the connection point 20V of the series circuit 10V and the V-phase winding 11V, and between the connection point 20W and the W-phase winding 11W of the series circuit 10W. Everything between and may be cut off.

  In the above embodiment, the electric power steering device is taken up. However, the present invention is not limited to the electric power steering device, and the electric pump type that generates the steering assist force by the generated hydraulic pressure of the oil pump driven by the electric motor. The present invention may be applied to other types of power steering devices such as a power steering device. In addition, the steering wheel and the steering mechanism are mechanically separated from each other, and steer-by-wire (SBW) that achieves steering of the steered wheels of the vehicle by applying the driving force of the electric motor to the steering mechanism. The present invention may be applied to a vehicle steering apparatus other than the power steering apparatus such as a system.

  In addition, various design changes can be made within the scope of matters described in the claims.

1 is a block diagram schematically showing the configuration of an electric power steering apparatus according to an embodiment of the present invention. It is a perspective view which shows the structure which can be replaced with the latching relay of FIG. 1, and can be employ | adopted.

Explanation of symbols

  1: Steering wheel, 3: Steering wheel, 4: Motor drive circuit, 12: Latching relay, 14U, 14V: Contact, 17U, 17V: Contact, 18U, 18V: Spring member, 21: Direct acting solenoid, M: Electric motor

Claims (2)

In a vehicle steering device that applies a steering force to a steered wheel of a vehicle according to an operation of an operation member,
A motor for generating a steering force;
A motor drive circuit for driving the motor;
Switch means that is interposed between the motor and the motor drive circuit, includes a permanent magnet, and maintains a closed state of contacts for connecting / disconnecting the motor and the motor drive circuit by the magnetic force of the permanent magnet. And a vehicle steering apparatus. In a vehicle steering device that applies a steering force to a steered wheel of a vehicle according to an operation of an operation member,
A motor for generating a steering force;
A motor drive circuit for driving the motor;
A contact for connecting / disconnecting the motor and the motor drive circuit;
A biasing means for biasing the contact in the opening direction;
An actuator for maintaining the contact in a closed state against an urging force of the urging means in a state in which no electric power is supplied, and for releasing the closed state of the contact when electric power is supplied. A steering apparatus for a vehicle that is characterized.

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