JP2005082058A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device using a brushless type motor M capable of solving a problem that the motor M may generate a back electromotive force when returning a steering wheel or the like. <P>SOLUTION: The brushless type motor M to provide the steering supporting force is provided on a steering transmission path to communicate a steering wheel with a turning wheel. Based on the target value of the steering supporting force, a current supplied from a battery B to the motor M is controlled. When the target value of the steering supporting force is not larger than a predetermined value, a power line to connect the battery B to the motor by a relay 16 is shut off to prohibit the current control of the motor M. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power steering apparatus including a brushless motor that generates a steering assisting force.

As disclosed in Patent Document 1, a technique using a reversible pump capable of selectively pressurizing two hydraulic chambers in a power steering device that applies a steering assist force by a differential pressure between two hydraulic chambers is known. It has been. During steering assist, a reversible pump is driven by a brushless motor to pressurize one hydraulic chamber. According to such a configuration using a reversible pump, it is sufficient to drive the pump only in a situation where a steering assist force is required, so that energy loss is small, and the pump is downsized and the hydraulic control is simplified. There is an advantage that the cost can be reduced by such as.
JP 2002-145087 A

  When the steering torque is returned to the neutral position by the self-aligning torque when the input torque value detected by the torque sensor is almost 0 as in the case of returning the steering wheel (steering wheel), generally, the brushless The motor current (voltage) command value, that is, the target value of the steering assist force is set to zero. That is, the current / voltage control of the motor is continued with the target value of the steering assisting force set to zero. In this case, the reversible pump tries to rotate by the hydraulic oil pressure pushed back from the hydraulic power cylinder to the reversible pump by the self-aligning torque from the steered wheels, and the brushless motor generates power to stop the rotation of the reversible pump. Acts to generate back electromotive force. Since this counter electromotive force acts as a resistance to rotation of the reversible pump, there is a problem that, for example, the hydraulic power cylinder is difficult to return to the neutral position, and the return to the neutral position of the steering wheel is reduced. The present invention has been made in view of such problems.

  A power steering device according to a first aspect of the present invention is a brushless motor that is provided in a steering transmission path that links an electric power source, a steering wheel, and a steering wheel, and that generates a steering assist force, and a target value of the steering assist force. Steering assist force target value calculating means for calculating the steering assist force, motor control means for controlling the current or voltage supplied from the power source to the motor based on the target value of the steering assist force, and the target value of the steering assist force And motor control prohibiting means for prohibiting the current control or voltage control of the motor when it is equal to or less than a predetermined value.

  A power steering device according to a second aspect of the present invention is a power cylinder that is provided in a steering transmission path that links a steering wheel and a steered wheel, and that generates a steering assist force in accordance with a differential pressure between the first hydraulic chamber and the second hydraulic chamber. A reversible hydraulic pump capable of selectively pressurizing the hydraulic pressure in the first and second hydraulic chambers, a brushless motor that drives the hydraulic pump, a power source, and a target value of the steering assisting force A steering assist force target value calculating means for calculating the steering assist force, a motor control means for controlling the current or voltage supplied from the power source to the motor based on the target value of the steering assist force, and the target value is less than a predetermined value. And motor control prohibiting means for prohibiting the current control or voltage control of the motor.

  According to these inventions, when the target value of the steering assisting force is equal to or less than a predetermined value (typically around 0), the current control or voltage control of the motor is prohibited, which is caused by the self-aligning torque. Thus, it is possible to reliably prevent the occurrence of inadvertent back electromotive force. Therefore, the returnability to the neutral position of the steering wheel is improved, and the operability such as turning back and turning of the steering wheel from the neutral position is improved.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a power steering apparatus according to the present invention. A steering shaft 1 and a rack L are provided on a steering transmission path that links the steering wheel SW and a pair of steering wheels (not shown) of the vehicle. The steering shaft 1 is connected to the steering wheel SW so as to rotate integrally around the shaft, and is linked to the rack L via a pinion P. A pair of steering wheels are linked to both ends of the rack L. Therefore, when the steering wheel SW is manually rotated, the rotation of the steering shaft 1 is converted into the linear motion of the rack L via the pinion P, and the direction of the pair of steering wheels can be changed (steered). The rack L is provided with a hydraulic power cylinder 2. The hydraulic power cylinder 2 has a pair of hydraulic chambers 2a and 2b defined by a piston 2c fixed to the rack L, and applies a steering assist force to the rack L by the differential pressure between the hydraulic chambers 2a and 2b. .

  The reversible gear pump 3 that supplies hydraulic pressure to both the hydraulic chambers 2 a and 2 b is driven by a motor M. The motor M is a well-known brushless motor, and drives the gear pump 3 by switching both forward and reverse rotation directions. The gear pump 3 includes a pair of discharge ports 3a and 3b that discharge pressurized oil generated during forward rotation and reverse rotation, respectively. The discharge ports 3a and 3b are connected to the hydraulic chambers 2a and 2b of the hydraulic power cylinder 2 through the discharge side communication passages 7a and 7b, respectively.

  Signals from various sensors such as a torque sensor TS that detects a steering force and a steering direction are input to an in-vehicle control unit (control unit) ECU. Based on these signals, the ECU calculates a target value of the steering assist force (steering assist force target value calculating means), and controls the current supplied to the motor M based on the target value. Operation is controlled (motor control means). The gear pump 3 is driven by this motor M, the hydraulic pressure supplied to both hydraulic chambers 2a, 2b of the hydraulic power cylinder 2 is adjusted, and a steering assist force according to a manual steering force and a steering direction is applied.

  The suction port 3 c of the gear pump 3 is connected to the reservoir tank T via the suction side communication path 8. The discharge side communication paths 7a, 7b and the reservoir tank T are connected by oil supply paths 9a, 9b. The oil supply paths 9a, 9b are connected to the oil in the direction from the reservoir tank T to the discharge side communication paths 7a, 7b. Check valves 5 and 5 are interposed so as to enable only replenishment of the fuel. The discharge-side communication passages 7 a and 7 b are connected to each other by a bypass flow path 6, and an electromagnetic valve 4 that opens and closes the bypass flow path 6 is interposed in the middle of the bypass flow path 6. The electromagnetic valve 4 is controlled to be opened and closed by the ECU. Specifically, the electromagnetic valve 4 is closed during normal operation and opened when an initial state or abnormality is detected.

  2 to 4 are block diagrams schematically showing the control unit ECU according to the first to third embodiments. In the figure, a thick line indicates a power line, and a thin line indicates a control line. The inverter 14 converts the power of the battery B as a power source from direct current to alternating current and supplies it to the motor M. The current sensor 15 detects the current value of the power line 19 connecting the inverter 14 and the motor M, and outputs the detection signal to the CPU 12. The CPU 12 outputs a control signal to the pre-driver 13 that is an integrated circuit (IC) based on the detection signals from the torque sensor TS and the current sensor 15 described above. In response to this, the pre-driver 13 outputs a control signal to the inverter 14 to drive and control the inverter 14.

  In the first embodiment shown in FIG. 2, a relay 16 that connects and disconnects the power line 19 is provided on a power line 19 that connects the inverter 14 and the motor M. The relay 16 is switched ON / OFF based on a control signal from the CPU 12 input via the relay control line 11.

  FIG. 5 is a flowchart showing the flow of control according to the first embodiment. In S (step) 11, the torque detection value of the torsion bar detected by the torque sensor TS is read. In S12, it is determined whether the detected torque value is equal to or smaller than a predetermined value, typically near 0, in other words, whether the target value of the steering assist force is equal to or smaller than a predetermined value, typically near 0.

  When the detected torque value is near 0, that is, when the driver is not operating the steering wheel SW as in the case of returning the steering wheel and it is not necessary to apply the steering assist force, the process proceeds from S12 to S13, and the relay 16 is turned on. The power line 19 is cut off as being OFF. Thereby, the motor M and the inverter 14 are electrically disconnected, and the motor M is opened, that is, the current control of the motor M is prohibited (motor control prohibiting means). Thereby, the counter electromotive force peculiar to the brushless motor M is not generated, the return property to the neutral position of the steering wheel SW is improved, and the operability from the neutral position of the steering wheel SW is improved.

  If the detected torque value (the target value of the steering assist force) is not near 0, that is, if the driver is actively operating the steering wheel SW and it is necessary to apply the steering assist force, the process proceeds from S12 to S14. Then, the relay 14 is turned on and the power line 19 is connected. In subsequent S15, the current supplied to the motor is controlled to give a desired steering assist force (motor control means).

  As described above, in this embodiment, when the torque detection value (target value of the steering assisting force) is near 0, the relay 14 is turned off and the power line 19 is cut off, so that the back electromotive force of the brushless motor is generated. Can be reliably prevented. In particular, since the power line 19 is forcibly cut off using the relay 14, the reliability is high.

  In the second embodiment shown in FIG. 3, the power line 19 is not provided with a relay as in the first embodiment, but instead of the main driver control line 21 as a control line connecting the CPU 12 and the pre-driver 13, A driver control line 22 is provided.

  FIG. 6 is a flowchart showing a flow of control according to the second embodiment. As in the first embodiment, the torque detection value of the torsion bar detected by the torque sensor TS is read in S21, and it is determined in S22 whether the torque detection value (target value of steering assisting force) is near zero. When the detected torque value is near 0, the process proceeds from S22 to S23, and a disable signal is output from the CPU 12 to the pre-driver 13 using the sub-driver control line 22 to set the pre-driver 13 in the disabled state. For example, the power supply circuit supplied from the battery B to the pre-driver 13 is shut off. As a result, the drive control of the inverter 14 by the pre-driver 13 is not performed, and the motor M is in an electrically open state, that is, the current control of the motor M is prohibited (motor control prohibiting means). Therefore, it is possible to avoid the occurrence of a counter electromotive force unique to the brushless motor M.

  When the detected torque value is not near 0, that is, when the driver is actively operating the steering wheel SW and it is necessary to apply the steering assisting force, the process proceeds from S22 to S24, via the sub driver control line 22. Then, an enable signal is output from the CPU 12 to the pre-driver 13 so that the pre-driver 13 can be driven. In the subsequent S25, a control signal is output from the CPU 12 to the pre-driver 13 via the main driver control line 21, and the current supplied to the motor M is controlled using the pre-driver 13 to obtain a desired steering assist force. Generated (motor control means).

  According to the second embodiment, as in the first embodiment, in addition to preventing the occurrence of back electromotive force, the motor current control is prohibited by the control circuit / software using the sub-driver control line 22. Therefore, it is not necessary to provide a relay as in the first embodiment, the configuration can be simplified correspondingly, the response and durability are excellent, and the steering resistance is suppressed to a low level.

  In the third embodiment shown in FIG. 4, the sub-driver control line of the second embodiment is also omitted, and the control of the pre-driver 13 by the CPU is stopped, thereby prohibiting the motor current control.

  FIG. 7 is a flowchart showing the flow of control according to the third embodiment. As in the first and second embodiments, the detected torque value of the torsion bar detected by the torque sensor TS is read in S31, and it is determined in S32 whether the detected torque value is near zero. When the detected torque value is near 0, the process proceeds from S32 to S33, and the control of the pre-driver 13 by the CPU 12 is stopped. As a result, the control of the inverter 14 by the pre-driver 13 is not performed, and the motor M is in an electrically open state, that is, the current control of the motor M is prohibited (motor control prohibiting means). Therefore, it is possible to reliably avoid the generation of the counter electromotive force of the brushless motor M.

  When the detected torque value is not near 0, that is, when the driver is actively operating the steering wheel SW and it is necessary to apply the steering assisting force, the process proceeds from S32 to S34, S35, and the pre-driver 13 from the CPU. A command signal is output to the motor, and the current supplied to the motor M is controlled by the pre-driver 13 and the inverter 14 to give a desired steering assist force.

  According to the third embodiment, as in the second embodiment, in addition to preventing the occurrence of back electromotive force of the brushless motor, the prohibition of motor current control is realized by software. It can be easily applied to the apparatus, is advantageous in terms of cost, is excellent in responsiveness and durability, and has a low steering resistance.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. .

  For example, based on a detection signal from the torque sensor TS or the like, control for actively returning the steering wheel SW to the neutral position (hereinafter referred to as return control) may be performed. In this case, when the return control is executed, even if the torque detection value is near 0, the motor current control is not prohibited, that is, the processing of S13, S23 or S33 is not performed, and the steering assisting force is not performed. The current control of the motor is performed with the target value of 0 being 0. As a result, the steering wheel SW can be quickly returned to the neutral position. On the other hand, if the detected torque value is near 0 and the return control is not performed or has been completed, the motor current control is prohibited (S13, S23 or S33). As a result, the motor is opened, the back electromotive force described above is not generated, and the steering wheel SW can be turned back and turned smoothly from the neutral position.

  Further, when the target value of the steering assist force is close to 0, the motor current (or voltage) control may be prohibited not only when the steering wheel is returned but also when the vehicle is traveling straight.

  Further, the present invention is not limited to the hydraulic power steering apparatus provided with the reversible pump as described above, but is also applied to a motor direct-acting electric power steering apparatus that directly applies a steering assisting force by a brushless motor. Is possible.

  The technical ideas other than the claims that can be understood from the above description are listed.

  (1) The motor control prohibiting unit includes a relay provided on a power line that supplies power from a power source to the motor, and when the target value is equal to or less than a predetermined value, the relay interrupts the power line.

  (2) The motor control prohibiting means disables the inverter or pre-driver that controls the current or voltage supplied to the brushless motor when the target value is equal to or less than a predetermined value. In this case, for example, as compared with the case where a relay is used, the configuration is simplified, the response and durability are excellent, and the steering resistance is suppressed to a low level.

  (3) The motor control prohibiting means stops the control of the inverter or pre-driver that controls the current or voltage supplied to the brushless motor when the target value is less than or equal to a predetermined value. In this way, the prohibition of motor current control is realized by software, so it can be easily applied to existing devices, is advantageous in terms of cost, has excellent responsiveness and durability, and has a steering resistance. It is suppressed low.

1 is a schematic configuration diagram showing a power steering device according to the present invention. The block diagram which shows simply the control part of the power steering apparatus which concerns on 1st Example. The block diagram which shows simply the control part of the power steering apparatus which concerns on 2nd Example. The block diagram which shows simply the control part of the power steering apparatus which concerns on 3rd Example. The flowchart which shows the flow of control which concerns on 1st Example. The flowchart which shows the flow of control which concerns on 2nd Example. The flowchart which shows the flow of control which concerns on 3rd Example.

Explanation of symbols

ECU ... control unit M ... motor B ... battery (power source)
TS ... Torque sensor 13 ... Pre-driver 14 ... Inverter

Claims (2)

A power source,
A brushless motor that is provided in a steering transmission path that links the steering wheel and the steering wheel and generates a steering assist force;
Steering assist force target value calculating means for calculating a target value of the steering assist force;
Motor control means for controlling the current or voltage supplied from the power source to the motor based on the target value of the steering assist force;
Motor control prohibiting means for prohibiting current control or voltage control of the motor when a target value of the steering assisting force is a predetermined value or less;
A power steering apparatus comprising: A power cylinder that is provided in a steering transmission path that links the steering wheel and the steering wheel, and that generates a steering assisting force according to a differential pressure between the first hydraulic chamber and the second hydraulic chamber;
A reversible hydraulic pump capable of selectively pressurizing the hydraulic pressure in the first and second hydraulic chambers;
A brushless motor that drives the hydraulic pump;
A power source,
Steering assist force target value calculating means for calculating a target value of the steering assist force;
Motor control means for controlling the current or voltage supplied from the power source to the motor based on the target value of the steering assist force;
Motor control prohibiting means for prohibiting current control or voltage control of the motor when the target value is a predetermined value or less;
A power steering apparatus comprising:

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