JP2006151335A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of maintaining the steering feeling as natural as possible and also capable of securely resuming idling. <P>SOLUTION: In the power steering device, the steering force of a vehicular steering member is assisted by an electric motor and the assisted steering force is varied by interlocking with a means for halting/restarting an engine. The power steering device comprises an engine halt detection means for detecting a halt of the engine, a rotational frequency reducing means for gradually reducing rotational frequency of the electric motor within a certain period of time when the engine halt detection means detects the halt of the engine, an engine start detection means for detecting the start of the engine, and a rotational frequency increasing means for gradually increasing the rotational frequency of the electric motor within a certain period of time when the engine start detection means detects the start of the engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention also has an idle stop function for stopping the engine when the vehicle is stopped by a signal, etc., and assists the steering force of the steering wheel (steering member) of the vehicle by the driving force of the electric motor or the hydraulic pressure generated by the pump driven by the electric motor. The present invention relates to a power steering device.

As an international environmental problem, there is a strong worldwide demand for reducing CO ₂ emissions from vehicles. Depending on the country, there are countries that have laws that prohibit idling under national laws. In Japan, in order to cope with such a problem, a vehicle equipped with an idle stop function that detects a state where the vehicle is stopped and automatically stops the engine has been developed.

  However, when a power steering device that assists the steering force of the steering member of the vehicle with the driving force of the electric motor or the hydraulic pressure generated by the pump driven by the electric motor is provided, when the engine is stopped, the rotation of the alternator also stops. Since the charging of the battery is also stopped, there is a problem in that the steering force may not be received during the steering operation of the steering member that originally needs the assistance of the steering force.

Therefore, by restarting the engine that has been paused at the time when the upsetting operation is detected, it is possible to receive the assistance of the steering force even during the upsetting operation of the steering member that originally needs the assistance of the steering force. A power steering device has been developed (see Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 10-318012 JP 2000-345878 A

  However, in the power steering apparatus described above, the idle stop function works simultaneously with the vehicle stop. Therefore, when there are many opportunities to repeatedly stop and retreat to move carefully, for example, when trying to put in a garage, the steering member is not assisted with steering force every time the vehicle stops, and as soon as the steering member is fixed This results in an unnatural steering feeling that the steering force is assisted.

  In order to receive steering force assistance while the engine is at rest, for example, the hydraulic pump is driven by output voltage from a battery to receive steering force assistance. However, when the battery charge amount is sufficient, the steering force can be assisted reliably, but when the battery charge amount is not sufficient, the battery becomes overdischarged, making it difficult to resume idling. There was a problem that there is a risk of becoming.

  In order to solve the above-described problems, an object of the present invention is to provide a power steering device that can maintain a steering feeling as natural as possible and can reliably resume idling.

  In order to achieve the above object, the power steering apparatus according to the first aspect of the present invention assists the steering force of the steering member of the vehicle by the electric motor, and fluctuates the assisting steering force in conjunction with the means for stopping and restarting the engine. In the power steering apparatus, engine stop detection means for detecting engine stop, and rotation speed reduction means for gradually reducing the rotation speed of the electric motor within a predetermined time when the engine stop detection means detects engine stop. Engine start detecting means for detecting engine start; and rotation speed increasing means for gradually increasing the rotation speed of the electric motor within a predetermined time when the engine start detection means detects engine start. Features.

  In the power steering device according to the first aspect of the invention, in conjunction with the idle stop function of the engine, when the engine is stopped, the rotational speed of the electric motor is gradually reduced within a certain time. As a result, the driver feels that the operation of the steering member gradually becomes heavy from the time when the engine is stopped, and the driver feels an unnatural steering sensation that the operation of the steering member becomes heavy suddenly by suddenly stopping the assist of the steering force. Never give to. Further, when the engine is restarted, the rotational speed of the electric motor is gradually increased within a certain time. As a result, the operation of the steering member gradually becomes lighter after the engine is restarted, and the operation of the steering member is lightened at a stroke by suddenly resuming the assist of the steering force. Is not given to a person.

  The power steering device according to a second aspect of the present invention is the power steering device according to the first aspect, wherein when the engine stop detection means detects engine stop, the battery output voltage is measured and the output voltage measured by the means is greater than a predetermined voltage. The means for determining whether or not the speed is low, and when the means is determined to be lower than a predetermined voltage, the rotational speed reducing means is configured to reduce the rotational speed of the electric motor to zero.

  In the power steering device according to the second aspect of the invention, when the engine is stopped, the rotation speed of the electric motor is set to zero when the output voltage of the battery becomes lower than a predetermined voltage. As a result, while the output voltage of the battery is equal to or higher than the predetermined voltage, the steering force is assisted by the output voltage from the battery, and it is necessary to restart the engine when the output voltage of the battery becomes lower than the predetermined voltage. In order to ensure a stable output voltage, the steering force assistance is completely stopped.

  The power steering device according to a third aspect of the present invention is characterized in that, in the first or second aspect, the predetermined voltage is an output voltage when the battery is fully charged.

  In the power steering apparatus according to the third aspect of the invention, when the engine is stopped, it is determined whether or not the rotation speed of the electric motor is made zero by comparing the output voltage with the output voltage when the battery is fully charged. As a result, the output voltage of the battery suddenly drops from the output voltage when the battery is fully charged due to deterioration of the battery, so that the engine can be restarted more reliably by using the battery full charge as a criterion for judgment. It is possible to secure an output voltage necessary for the operation.

  As described above, according to the present invention, the operation of the steering member gradually becomes heavier from the time when the engine is stopped, and the operation of the steering member gradually becomes lighter after the engine is restarted. Therefore, it is possible to prevent the driver from feeling an unnatural steering feeling such that the operation of the steering member becomes heavy or light.

  Further, while the output voltage of the battery is a predetermined voltage, for example, the output voltage when the battery is fully charged, the steering force is assisted by the output voltage from the battery, and when the output voltage of the battery becomes lower than the predetermined voltage, the battery By stopping the assist of the steering force by the output voltage, it is possible to reliably ensure the output voltage necessary for restarting the engine.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.

(Embodiment 1)
FIG. 1 is a block diagram showing a main configuration of the power steering apparatus according to Embodiment 1 of the present invention. In the power steering apparatus according to the first embodiment, the CPU 12 calculates the steering angular speed based on the output signal of the steering angle sensor 10, and the electric motor 27 based on the calculated steering angular speed and the vehicle speed detected by the vehicle speed sensor 14. Target rotation speed R is set.

  Specifically, a steering speed detection signal of a steering angle sensor 10 that detects a steering speed by rotating a steering shaft (not shown) is given to the CPU 12 via the interface circuit 11. A vehicle speed signal from a vehicle speed sensor 14 that detects the vehicle speed is given to the CPU 12 via the interface circuit 15. Further, a detection signal of the engine tachometer 3 for detecting the engine speed is given to the CPU 12 via the interface circuit 4. The CPU 12 creates a motor rotation speed command value corresponding to the target rotation speed R of the electric motor 27 set based on the given steering angle signal and vehicle speed signal with reference to the built-in steering speed / motor rotation speed table 12a. And input to the PWM control unit 5.

  The PWM control unit 5 creates a drive signal necessary to achieve the target rotation speed R based on the motor current detected by the current sensor and the rotation angle detected by the Hall sensor, and uses the generated drive signal as the electric motor. 27 drive circuit 28.

  The electric motor 27 includes a stator having a U-phase field coil 27U, a V-phase field coil 27V, and a W-phase field coil 27W, and a permanent magnet that receives a repulsive magnetic field from the field coils 27U, 27V, and 27W. For example, a rotor with a ferrite magnet) fixed thereto is provided, and the rotation angle of the rotor is detected by a Hall sensor.

  The hall sensor has hall sensors 22U, 22V, and 22W provided corresponding to the U phase, the V phase, and the W phase, respectively. These hall sensors 22U, 22V, and 22W are built in the electric motor 27. The rotation angle of the rotor may be detected by a rotation angle sensor (for example, a resolver) other than the Hall sensor, and such a rotation angle sensor may be provided in the casing of the electric motor 27. It may be provided outside thereof.

  The current sensor that detects the current flowing through the electric motor 27 includes current sensors 21U, 21V, and 21W that detect currents flowing through the U phase, the V phase, and the W phase, respectively. The output signals from the current sensors 21U, 21V, and 21W are input to the motor current detection circuit 7, and the output signals from the hall sensors 22U, 22V, and 22W are input to the CPU 12, respectively.

  The drive circuit 28 includes a pair of field effect transistors UH and UL corresponding to the U phase, a pair of field effect transistors VH and VL corresponding to the V phase, and a pair of field effect transistors WH corresponding to the W phase, A WL series circuit is connected in parallel to the in-vehicle battery 40 as a power source. The U-phase field coil 27U of the electric motor 27 is connected to a connection point between the field effect transistors UH and UL, and the V-phase field coil 27V is connected to a connection point between the field effect transistors VH and VL. The W-phase field coil 27W is connected to a connection point between the field effect transistors WH and WL.

  The CPU 12 sequentially turns on the field effect transistors UH, VH, and WH only for each fixed electrical angle period, and gives a drive signal including a PWM pulse to the field effect transistors UL, VL, and WL. The rotation of the electric motor 27 is controlled. That is, by setting a PWM duty according to the target rotational speed R, the PWM control unit 5 outputs a drive signal to be applied to the field effect transistors UH, UL, VH, VL, WH, WL of the drive circuit 28.

  The CPU 12 acquires the current values detected by the current sensors 21U, 21V, and 21W from the motor current detection circuit 7 and the output signals of the hall sensors 22U, 22V, and 22W as feedback signals, and outputs the target rotation to the PWM controller 5. The PWM duty setting value corresponding to the speed R is output.

  In the above description, the vehicle speed is detected by the vehicle speed sensor 14, and the engine speed is detected by the engine tachometer 3. Instead of the vehicle speed sensor 14 and the engine tachometer 3, a CAN signal sensor that detects both simultaneously. (Not shown) may be provided and given to the CPU 12 via an interface circuit (not shown).

  FIG. 2 is a flowchart showing a processing procedure of the CPU 12 of the power steering apparatus according to Embodiment 1 of the present invention, and FIG. 3 shows the rotation of the engine and electric motor of the power steering apparatus according to Embodiment 1 of the present invention. It is a figure which shows transition of a number. The CPU 12 reads the detection signal of the vehicle speed sensor 14 via the interface circuit 15 (step S201), and determines whether or not the vehicle is stopped based on the read detection signal of the vehicle speed sensor 14 (step S202). ).

  When CPU12 determines with the vehicle moving (it has not stopped) (step S202: NO), it returns to step S201 and CPU12 reads the detection signal of the vehicle speed sensor 14 until a vehicle stops. When the CPU 12 determines that the vehicle is stopped (step S202: YES), the detection signal of the engine tachometer 3 which is the engine stop detection means is read via the interface circuit 4 (step S203). Based on the detection signal, it is determined whether or not the engine speed is equal to or less than a predetermined value (step S204). The predetermined value as a reference for determination is preferably an idling speed, particularly an idling speed in a state where no load such as an in-vehicle air conditioner is generated.

  When the CPU 12 determines that the engine speed is greater than the predetermined value (step S204: NO), the process returns to step S203, and the CPU 12 outputs a detection signal from the engine tachometer 3 until the engine speed becomes equal to or lower than the predetermined value. Read. When the CPU 12 determines that the engine speed is equal to or less than the predetermined value (step S204: YES), the CPU 12 determines that the vehicle is in an idling state, and the CPU 12 is an electric motor that is a DC brushless motor as the speed reducing means. A motor rotational speed command value for reducing the rotational speed of the motor 27 within a predetermined time is output to the PWM controller 5 (step S205).

  The CPU 12 calculates a signal for reducing the rotational speed of the electric motor 27 within a predetermined time by the following procedure. A unit time is set so that the reduction time of the rotational speed is stored as a constant value (for example, 15 seconds) and the current rotational speed of the electric motor 27 is gradually reduced within the predetermined constant time stored up to the target minimum rotational speed. The amount of decrease in the number of rotations per unit (for example, per second) is calculated. The CPU 12 outputs, to the PWM control unit 5, a motor rotation speed command value obtained by correcting the target rotation speed for each unit time based on the amount of decrease in the rotation speed per unit time. The PWM controller 5 creates a PWM signal while gradually decreasing the duty ratio in accordance with the motor rotation speed command value, and gradually decreases the rotation speed of the electric motor 27 within a certain time.

  In FIG. 3, when the engine is stopped by the idle stop function, that is, when the engine speed shifts from 600 rpm, which is the idling engine speed, to 0 rpm, the rotation speed of the electric motor 27 that supplies the auxiliary steering force is set to 2500 rpm. From 15 to 1000 rpm in 15 seconds. As a result, even when the steering member is stationary immediately after the engine is stopped, the steering speed is not suddenly increased, and the rotation speed of the electric motor 27 is reduced while leaving a natural steering feeling. can do.

  In addition, in the state where the rotation speed of the electric motor 27 is 1000 rpm, the driver cannot receive normal steering force assistance, but can receive some steering force assistance. That is, the steering member can be operated more lightly than in a state where the rotation speed of the electric motor 27 is 0 (zero).

  When the engine is stopped, the CPU 12 detects a restart signal for restarting the engine to the ECU of the engine when the driver detects that the driver depresses the accelerator, or the steering member is turned off. Output. The CPU 12 reads the detection signal of the engine tachometer 3 which is an engine start detection means via the interface circuit 4 (step S206), and the engine is restarted based on the read detection signal of the engine tachometer 3. It is determined whether or not there is (step S207).

  When the CPU 12 determines that the engine has not been restarted (step S207: NO), the process returns to step S206, and the CPU 12 reads the detection signal of the engine tachometer 3. When the CPU 12 determines that the engine has been restarted (step S207: YES), the CPU 12 rotates the rotation speed of the DC motor M before the rotation speed is reduced within a predetermined time as the rotation speed increasing means. The motor rotation number command value to be returned to the number is output to the PWM control unit 5 (step S208).

  The CPU 12 calculates a motor rotation speed command value for returning the rotation speed of the electric motor 27 within a predetermined time to the rotation speed before the rotation speed is reduced. The time for returning the rotational speed is stored as a constant value (for example, 15 seconds), and the current rotational speed of the electric motor 27 is stored up to the target rotational speed so as to gradually increase within the predetermined time. The amount of increase in the rotational speed (for example, per second) is calculated. The CPU 12 outputs to the PWM controller 5 a motor rotation speed command value obtained by correcting the target rotation speed for each unit time based on the increase amount of the rotation speed per unit time. The PWM control unit 5 creates a PWM signal while gradually increasing the duty ratio in accordance with the motor rotation speed command value, and gradually increases the rotation speed of the electric motor 27 within a certain time.

  In FIG. 3, when the engine is restarted by the idle stop function, that is, when the engine speed returns to the idling speed of 600 rpm, the speed of the electric motor that supplies the auxiliary steering force is changed from 1000 rpm to 2500 rpm. It gradually increases in 15 seconds. As a result, even when the steering member is stationary immediately after the engine is restarted, the rotation speed of the electric motor is increased while maintaining a natural steering sensation without feeling that the steering has suddenly lightened. can do.

(Embodiment 2)
FIG. 4 is a block diagram showing a main configuration of the power steering apparatus according to Embodiment 2 of the present invention. Since the basic configuration of the power steering apparatus according to the second embodiment is the same as that of the first embodiment, detailed description thereof will be omitted by attaching the same reference numerals.

  In the power steering apparatus according to the second embodiment, the detection signal of the battery output voltmeter 1 that detects the output voltage of the battery is given to the CPU 12 via the interface circuit 2. The CPU 12 creates a motor rotation speed command value corresponding to the given steering angle signal and vehicle speed signal with reference to the built-in steering speed / motor rotation speed table 12 a and inputs the motor rotation speed command value to the PWM controller 5.

  FIG. 5 is a flowchart showing the processing procedure of the CPU 12 of the power steering apparatus according to the second embodiment of the present invention, and FIG. 6 shows the rotation of the engine and electric motor of the power steering apparatus according to the second embodiment of the present invention. It is a figure which shows transition of a number. The CPU 12 reads the detection signal of the vehicle speed sensor 14 through the interface circuit 15 (step S501), and determines whether or not the vehicle is stopped based on the read detection signal of the vehicle speed sensor 14 (step S502). ).

  When the CPU 12 determines that the vehicle is moving (not stopped) (step S502: NO), the process returns to step S501, and the CPU 12 reads the detection signal of the vehicle speed sensor 14 until the vehicle stops. When the CPU 12 determines that the vehicle is stopped (step S502: YES), the detection signal of the engine tachometer 3 is read via the interface circuit 4 (step S503), and based on the read detection signal, It is determined whether the engine speed is equal to or less than a predetermined value (step S504). The predetermined value as a reference for determination is preferably an idling speed, particularly an idling speed in a state where no load such as an in-vehicle air conditioner is generated.

  When the CPU 12 determines that the engine speed is greater than the predetermined value (step S504: NO), the process returns to step S503, and the detection signal of the engine tachometer 3 is read until the engine speed becomes the predetermined value or less. When the CPU 12 determines that the engine speed is equal to or lower than the predetermined value (step S504: YES), the CPU 12 determines that the vehicle is in an idling state, and the CPU 12 is an electric motor that is a DC brushless motor as the speed reducing means. A motor rotational speed command value for reducing the rotational speed of the motor 27 within a predetermined time is output to the PWM controller 5 (step S505).

  The CPU 12 calculates the motor rotation speed command value for reducing the rotation speed of the electric motor 27 within a predetermined time by a predetermined procedure. A unit time is set so that the reduction time of the rotational speed is stored as a fixed time (for example, 15 seconds), and the current rotational speed of the electric motor 27 is gradually reduced within the predetermined fixed time stored up to the target minimum rotational speed. The amount of decrease in the number of rotations per unit (for example, per second) is calculated. The CPU 12 outputs, to the PWM control unit 5, a motor rotation speed command value obtained by correcting the target rotation speed for each unit time based on the amount of decrease in the rotation speed per unit time. The PWM controller 5 creates a PWM signal while gradually decreasing the duty ratio in accordance with the motor rotation speed command value, and gradually decreases the rotation speed of the electric motor 27 within a certain time.

  In FIG. 6, when the engine is stopped by the idle stop function, that is, when the engine speed shifts from 600 rpm, which is the idling speed, to 0 rpm, the rotation speed of the electric motor 27 that supplies the auxiliary steering force is set to 2500 rpm. From 15 to 1000 rpm in 15 seconds. As a result, even when the steering member is stationary immediately after the engine is stopped, the steering speed is not suddenly increased, and the rotation speed of the electric motor 27 is reduced while leaving a natural steering feeling. can do.

  In addition, in the state where the rotation speed of the electric motor 27 is 1000 rpm, the driver cannot receive normal steering force assistance, but can receive some steering force assistance. That is, the steering member can be operated more lightly than in a state where the rotation speed of the electric motor 27 is 0 (zero).

  When the engine is stopped, the CPU 12 detects a restart signal for restarting the engine to the ECU of the engine when the driver detects that the driver depresses the accelerator, or the steering member is turned off. Output. The CPU 12 reads the detection signal of the engine tachometer 3 through the interface circuit 4 (step S506), and determines whether or not the engine has been restarted based on the read detection signal of the engine tachometer 3. (Step S507).

  When the CPU 12 determines that the engine has not yet been restarted (step S507: NO), the CPU 12 reads the detection signal of the battery output voltmeter 1 via the interface circuit 2 (step S508) and reads it. Based on the detection signal, it is determined whether or not the output voltage of the battery is lower than a predetermined value (step S509). The predetermined value as a criterion for determination is preferably an output voltage when the battery is fully charged. This is because the output voltage of the battery rapidly decreases from the output voltage when the battery is fully charged due to deterioration of the battery.

  When the CPU 12 determines that the output voltage of the battery is lower than the predetermined value (step S509: YES), the CPU 12 determines that the deterioration of the battery is progressing and secures the output voltage for restarting the engine. Outputs a motor rotation speed command value for setting the rotation speed of the electric motor 27 to 0 (zero) to the PWM controller 5 (step S510). The PWM controller 5 creates a PWM signal having a duty ratio of 0 according to the motor rotation speed command value, and stops the rotation of the electric motor 27.

  In FIG. 6, when the CPU 12 determines that the deterioration of the battery is progressing, the rotational speed of the electric motor that supplies the auxiliary steering force is decreased from 1000 rpm to 0 rpm. As a result, the driver cannot receive the assistance of the steering force, but can surely secure the output voltage necessary for restarting the engine, for example, when the engine is stopped at a red light at the intersection. It is possible to prevent the restart from being impossible.

  When the CPU 12 determines that the engine has been restarted (step S507: YES), the CPU 12 rotates as the rotation speed increasing means before the rotation speed of the electric motor 27 is decreased within a predetermined time. The motor rotation number command value to be returned to the number is output to the PWM control unit 5 (step S511).

  The CPU 12 calculates a motor rotation speed command value for returning the rotation speed of the electric motor 27 within a predetermined time to the rotation speed before the rotation speed is reduced. The time for returning the rotational speed is stored as a constant value (for example, 15 seconds), and the current rotational speed of the electric motor 27 is stored up to the target rotational speed so as to gradually increase within the predetermined time. The amount of increase in the rotational speed (for example, per second) is calculated. The CPU 12 outputs to the PWM controller 5 a motor rotation speed command value obtained by correcting the target rotation speed for each unit time based on the increase amount of the rotation speed per unit time. The PWM control unit 5 creates a PWM signal while gradually increasing the duty ratio according to the motor rotation speed command value, and gradually increases the rotation speed of the electric motor 27 within a certain time.

  In FIG. 6, when the engine is restarted by the idle stop function, that is, when the engine speed returns to 600 rpm that is the idling speed, the rotation speed of the electric motor that supplies the auxiliary steering force is changed from 0 rpm to 2500 rpm. It gradually increases in 15 seconds. As a result, even when the steering member is stationary immediately after the engine is restarted, the rotation speed of the electric motor 27 can be reduced with a natural steering feeling without feeling that the steering has suddenly lightened. Can be increased.

  In the first and second embodiments described above, a case has been described in which the target rotational speed to be increased within a predetermined time by the rotational speed increasing means is the rotational speed before the rotational speed is decreased by the rotational speed reducing means. However, the present invention is not particularly limited to this, and the same effect can be expected as long as the number of revolutions reduced by the revolution number reduction means is increased.

It is a block diagram which shows the principal part structure of the power steering apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows the process sequence of CPU of the power steering apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the transition of the rotation speed of the engine and electric motor of the power steering apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the principal part structure of the power steering apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the process sequence of CPU of the power steering apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the transition of the rotation speed of the engine and electric motor of the power steering apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery output voltmeter 3 Engine tachometer 5 PWM control part 10 Steering angle sensor 12 CPU
14 Vehicle speed sensor 27 DC brushless motor (electric motor)

Claims (3)

In the power steering device that assists the steering force of the steering member of the vehicle by the electric motor and fluctuates the steering force that assists in conjunction with the means for stopping and restarting the engine,
Engine stop detection means for detecting engine stop; and
A rotation speed reduction means for gradually reducing the rotation speed of the electric motor within a predetermined time when the engine pause detection means detects engine pause;
Engine start detecting means for detecting engine start;
A power steering device comprising: a rotation speed increasing means for gradually increasing the rotation speed of the electric motor within a predetermined time when the engine start detection means detects engine start. Means for measuring the output voltage of the battery when the engine stop detection means detects engine stop;
Means for determining whether the output voltage measured by the means is lower than a predetermined voltage;
2. The power steering apparatus according to claim 1, wherein when the means is determined to be lower than a predetermined voltage, the rotation speed reduction means is configured to make the rotation speed of the electric motor zero.   The power steering apparatus according to claim 1, wherein the predetermined voltage is an output voltage when the battery is fully charged.

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