JP3923455B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that assists a driver with a steering operation with a motor, and in particular, a function of prohibiting driving of a motor in a direction opposite to a direction of a steering torque input by a driver to a steering handle, and power supply to the motor The present invention relates to an electric power steering apparatus having a function of detecting line breakage or motor breakage.

  The electric power steering device is provided with a motor drive prohibition means that prohibits the drive of the motor, and the motor that should assist the driver's steering operation is prohibited from generating a torque in the direction opposite to the direction of the steering torque that the driver applies to the steering handle. This is disclosed in Patent Document 1 below.

Also, if the power supply line that supplies power to the motor of the electric power steering device is disconnected or the winding of the motor is disconnected, the motor becomes inoperable and the driver's steering operation cannot be assisted. It is necessary to detect the occurrence. Therefore, conventionally, when the duty ratio for driving the motor is, for example, 100%, the occurrence of the disconnection is detected when the current supplied to the motor is below a threshold for a predetermined time. Yes.
JP 2000-190861 A

  However, in the case where the motor drive prohibiting means for prohibiting the motor drive is provided in the electric power steering device, the motor may not be operated by the motor drive prohibiting means when the motor drive command is output. There is a possibility that it is erroneously determined that the motor does not operate due to the disconnection of the motor or the winding of the motor winding.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to enable detection of disconnection without any trouble in an electric power steering apparatus provided with motor drive prohibiting means.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a steering torque detecting means for detecting a steering torque input to the steering handle by the driver, a motor for assisting the steering operation of the driver, and a motor. Motor current detection means for detecting the supplied motor current, and control means for controlling the drive of the motor based on at least the steering torque and detecting the disconnection of the power supply line to the motor or the motor disconnection based on the motor current And a motor drive prohibiting means for prohibiting driving of the motor in the direction opposite to the steering torque direction, when the motor drive prohibiting means prohibits driving of the motor, the control means Proposed is an electric power steering device characterized by prohibiting detection of the disconnection

  The motor current detection circuit 49 of the embodiment corresponds to the motor current detection means of the present invention, the motor drive prohibition circuit 52 of the embodiment corresponds to the motor drive prohibition means of the present invention, and the steering torque sensor St of the embodiment Corresponding to the steering torque detection means of the invention, the electronic control unit U of the embodiment corresponds to the control means of the invention.

  According to the first aspect of the present invention, when the motor drive prohibiting unit prohibits driving of the motor, the control unit prohibits detection of disconnection of the power supply line to the motor or disconnection of the motor. It is possible to surely prevent the state in which the means prohibits the driving of the motor from being erroneously determined as the state in which the disconnection has occurred.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 6 show an embodiment of the present invention, FIG. 1 is an overall perspective view of an electric power steering apparatus, FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1, and FIG. FIG. 4 is a diagram showing a motor drive circuit, FIG. 5 is a diagram for explaining the operation during normal rotation and reverse rotation of the motor, and FIG. 6 is a flowchart for explaining the operation for detecting disconnection.

  As shown in FIG. 1, the upper steering shaft 12 that rotates integrally with the steering handle 11 has a pinion shaft 17 that protrudes upward from the speed reducer 16 via an upper universal joint 13, a lower steering shaft 14, and a lower universal joint 15. Connected to. Tie rods 19 and 19 projecting from the left and right ends of the steering gear box 18 connected to the lower end of the speed reducer 16 are connected to knuckles (not shown) of the left and right wheels WL and WR. A motor M is supported on the speed reducer 16, and the operation of the motor M is controlled by an electronic control unit U to which a signal from a steering torque sensor St housed in the speed reducer 16 is input.

  2 and 3, the speed reducer 16 is coupled to the lower case 21 integrated with the steering gear box 18, the intermediate case 23 coupled to the upper surface thereof with bolts 22 ..., and the upper surface thereof coupled to the bolts 24 ... The pinion shaft 17 is rotatably supported by the steering gear box 18 and the upper case 25 by ball bearings 26 and 27. A pinion 28 provided at the lower end of the pinion shaft 17 meshes with a rack 30 provided on a rack bar 29 supported inside the steering gear box 18 so as to be movable left and right. A pressing member 31 is slidably accommodated in a through hole 18 a formed in the steering gear box 18, and the pressing member 31 is attached to the rack bar 29 by a spring 33 disposed between the nut member 32 closing the through hole 18 a. By biasing toward the back, the deflection of the rack bar 29 is suppressed.

  A rotation shaft 34 of the motor M extending inside the reduction gear 16 is rotatably supported by the lower case 21 by a pair of ball bearings 35 and 36, and a worm 37 provided on the rotation shaft 34 of the motor M is a pinion. It meshes with a worm wheel 38 fixed to the shaft 17.

  Therefore, when the motor M is driven, the torque of the rotating shaft 34 is transmitted to the pinion shaft 17 via the worm 37 and the worm wheel 38, and the driver's steering operation is assisted by the motor M.

  FIG. 4 shows a motor drive circuit C that drives the motor M in response to a command from the electronic control unit U. The motor drive circuit C includes an H-bridge circuit 41, and the high-voltage terminal TH is connected to the plus pole 45a of the on-vehicle 12V battery 45 via the shunt resistor 42, the power relay 43 and the choke coil 44, and the low-voltage terminal The TL is grounded and connected to the negative electrode 45b of the battery 45. The first output terminal TM1 and the second output terminal TM2 of the H bridge circuit 41 are connected to the motor M, the low voltage terminal TL and the first output terminal TM1 are connected by the first switching element 46a, and the low voltage terminal TL and the second output terminal TM1 are connected. The output terminal TM2 is connected by the second switching element 46b, the high voltage terminal TH and the first output terminal TM1 are connected by the third switching element 46c, and the high voltage terminal TH and the second output terminal TM2 are connected by the fourth switching element 46d. The The first to fourth switching elements 46a to 46d are configured by, for example, field effect transistors (FETs). A fail safe relay 47 is disposed between one of the first output terminal TM1 and the second output terminal TM2 (first output terminal TM1 in the embodiment) and the motor M.

  A power relay 43 that turns on / off the supply of power from the battery 45 to the H-bridge circuit 41 and a fail-safe relay 47 that stops the motor M in the event of an abnormality are a common relay drive circuit 48 controlled by the electronic control unit U. The power relay 43 and the fail safe relay 47 are turned ON / OFF in conjunction with each other. That is, when the power relay 43 is turned on, the fail safe relay 47 is also turned on, and when the power relay 43 is turned off, the fail safe relay 47 is also turned off, thereby reducing the cost and the failure rate of the relay drive circuit 48.

  The shunt resistor 42 disposed between the power relay 43 and the H bridge circuit 41 is connected to a motor current detection circuit 49, and the motor current detection circuit 49 connected to the electronic control unit U has a potential difference between both ends of the shunt resistor 42. And the current supplied from the battery 45 to the H-bridge circuit 41 based on the resistance value of the shunt resistor 42.

  The potential VMN of the first output terminal TM1 and the potential VMP of the second output terminal TM2, that is, the potentials of both terminals of the motor M are detected by the motor terminal voltage detection circuit 50 connected to the electronic control unit U. When the motor M is not operating, the potential VMN of the first output terminal TM1 and the potential VMP of the second output terminal TM2 are pulled up to 2V to 3V by the battery 45.

  The first to fourth switching elements 46 a to 46 d of the H-bridge circuit 41 are duty-controlled by a switching element driving circuit 51 connected to the electronic control unit U. That is, as shown in FIG. 5A, when the first switching element 46a and the fourth switching element 46d at the diagonal positions are turned on, the first output terminal TM1 is connected to the low voltage terminal TL and becomes 0V. The motor M rotates forward by the 2 output terminal TM2 being connected to the high voltage terminal TH and becoming 12V. At this time, the current flowing through the motor M can be controlled by controlling the duty ratio of one of the first switching element 46a and the fourth switching element 46d.

  Further, as shown in FIG. 5B, when the second switching element 46b and the third switching element 46c at other diagonal positions are turned ON, the second output terminal TM2 is connected to the low voltage terminal TL and becomes 0V. When the first output terminal TM1 is connected to the high voltage terminal TH and becomes 12V, the motor M is reversely rotated. At this time, the current flowing through the motor M can be controlled by controlling the duty ratio of one of the second switching element 46b and the third switching element 46c.

  A motor drive prohibition circuit 52 is disposed between the electronic control unit U and the switching element drive circuit 51, and the direction of the steering torque detected by the steering torque detection means St and the motor drive signal output by the electronic control unit U. When the direction is the opposite direction, the motor drive inhibition circuit 52 outputs a motor drive inhibition signal to the switching element drive circuit 51.

  Further, the electronic control unit U has a function of detecting disconnection of the power supply lines 53 and 54 that connect the H bridge circuit 41 and the motor M or disconnection of the motor M itself. Hereinafter, the disconnection detection function of the electronic control unit U will be described with reference to the flowchart of FIG.

First, the motor current IM1 detected by the motor current detection circuit 49 in step S1 is less than the threshold value #IMOPH, and the duty ratio DUTY of the drive signal for the motor M is the threshold value #DUTYHS (100% in the embodiment) in step S2. When the duty ratio DUTY> 0 in step S3, that is, when the drive signal of the motor M is in the right steering direction, the right steering prohibition flag F is determined in step S4. If INHR = 1 and the motor drive prohibition circuit 52 prohibits driving of the motor M in the right steering direction, the failure detection counter COPEN is reset in step S5 to prohibit disconnection detection. On the other hand, if the motor drive prohibition circuit 52 does not prohibit the motor M from being driven in the right steering direction in step S4, the failure detection counter COPEN is incremented in step S7.

When the duty ratio DUTY> 0 is not satisfied in step S3, that is, when the drive signal of the motor M is in the left steering direction, the left steering prohibition flag F is determined in step S6. If INHL = 1 and the motor drive prohibition circuit 52 prohibits driving of the motor M in the left steering direction, the failure detection counter COPEN is reset in step S5 to prohibit disconnection detection. On the other hand, if the motor drive prohibition circuit 52 does not prohibit the driving of the motor M in the left steering direction in the step S6, the failure detection counter COPEN is incremented in the step S7.

  If the failure detection counter COPEN becomes greater than or equal to the threshold value #COPENNG in step S8, the occurrence of a disconnection failure is determined in step S9.

  As described above, when the duty ratio DUTY of the drive signal of the motor M is 100%, even if the motor current IM1 is less than the threshold value #IMOPH, the disconnection failure is not immediately determined, and the steering torque detected by the steering torque sensor St. Since the detection of the disconnection failure is prohibited when the direction of the motor and the drive direction of the motor M prohibited by the motor drive prohibition circuit 52 coincide, the state where the motor drive prohibition circuit 52 prohibits the drive of the motor M is disconnected. It is possible to reliably prevent erroneous determination as a state in which the occurrence of the error occurs. In addition, since the disconnection failure is determined only when the failure detection counter COPEN becomes equal to or greater than the threshold value #COPENNG, it is possible to prevent erroneous determination due to noise or the like.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

Overall perspective view of electric power steering device 2-2 line enlarged sectional view of FIG. 3-3 sectional view of FIG. The figure which shows the drive circuit of the motor Action diagram for forward and reverse rotation of motor Flowchart explaining operation of disconnection detection

Explanation of symbols

11 Steering handle 49 Motor current detection circuit (motor current detection means)
52 Motor drive prohibition circuit (motor drive prohibition means)
53 Electric power supply line 54 Electric power supply line M Motor St Steering torque sensor (steering torque detection means)
U Electronic control unit (control means)

Claims (1)

A steering torque detecting means (St) for detecting a steering torque input to the steering handle (11) by the driver, a motor (M) for assisting the steering operation of the driver, and a motor current supplied to the motor (M) are detected. The motor (M) is controlled based on the motor current detection means (49) and at least the steering torque, and the power supply lines (53, 54) to the motor (M) are disconnected based on the motor current or the motor ( In an electric power steering apparatus comprising a control means (U) for detecting disconnection of M) and a motor drive prohibiting means (52) for prohibiting driving of the motor (M) in the direction opposite to the steering torque direction,
The electric power steering apparatus, wherein when the motor drive prohibiting means (52) prohibits driving of the motor (M), the control means (U) prohibits the detection of the disconnection.