JP2009161120A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device for quickly returning to a state capable of assisting steering, by shortening charging time of an auxiliary power source, by supplying a regenerative current recirculated to the power source only to the auxiliary power source connected in parallel to a main power source. <P>SOLUTION: This electric power steering device has the main power source composed of an on-vehicle generator 34 and an on-vehicle battery 26, a steering assisting motor 18 driven by the main power source and a motor driving circuit 13, and the auxiliary power sources 29 and 32 connected in parallel to the main power source and the motor driving circuit 13 and assisting an electric current made to flow to the motor 18, and controls the electric current flowing to the motor 18 based on steering torque detected by a torque sensor 10, and has a motor current detecting circuit 17 detecting the electric current flowing in the motor driving circuit 13 from the main power source and the auxiliary power sources 29 and 32, a relay driving circuit 15 and a relay contact point 15a cutting off the main power source from the auxiliary power sources 29 and 32 when the motor current detecting circuit 17 does not detect the electric current flowing in the motor driving circuit 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering device that assists steering by a driving force generated by a steering assist motor based on a steering torque.

  The electric power steering device assists a steering force applied to a vehicle by a motor, and a steering torque applied to the steering wheel to a steering mechanism in which a steering member (steering wheel, steering wheel) is connected via a steering shaft. And a motor that is supplied with power from a generator and a battery and assists the operation of the steering mechanism. With such a configuration, the steering force applied to the steered wheels is reduced by driving the motor in accordance with the steering torque detected by the torque detector.

  In the electric power steering apparatus, when a large steering force such as “stationary” is applied, it is necessary to temporarily supply a large current from the power source. Therefore, in Patent Document 1, an auxiliary power source such as a secondary battery or a large-capacity capacitor is provided separately from the main power source including a generator and a battery so that current can be supplied from both the main power source and the auxiliary power source. . Moreover, in patent document 2, when there is a possibility that the power supply of the main power supply (first power supply means) may not be performed normally, power is supplied from the auxiliary power supply (second power supply means). .

The auxiliary power source discharged for use in steering assistance needs to be charged before it is used next time. This charging is performed by a current supplied from the main power source during a period when steering assistance is not performed. On the other hand, when the steering assist is stopped, a counter electromotive force is generated in the motor due to the reaction force from the tire, so-called regenerative current flows, and most of it returns to the main power supply and auxiliary power supply from the motor. Therefore, it is conceivable to reduce the charging time of the auxiliary power by using the regenerated current that has been refluxed for charging the auxiliary power.
JP 2003-320942 A JP 2006-213273 A

  However, in the technique disclosed in Patent Document 1, the regenerative current that has recirculated to the power supply side recirculates not only to the auxiliary power supply but also to the main power supply, so that the regenerative current is sufficient for shortening the charging time of the auxiliary power supply. It cannot be used effectively. In the technique disclosed in Patent Document 2, the regenerative current is not used for charging the auxiliary power source as long as at least the main power source is normal.

The present invention has been made in view of the circumstances as described above, and in the first invention, the regenerative current returned to the power supply side is supplied only to the auxiliary power supply connected in parallel to the main power supply, and the auxiliary power supply An object of the present invention is to provide an electric power steering device capable of shortening the charging time and speeding up the return to a state where steering assist is possible.
In the second aspect of the invention, charging and discharging of the auxiliary power supply is suppressed at a light load that does not require an auxiliary power supply, and current is supplied from the auxiliary power supply to the steering assist motor at a heavy load that requires the auxiliary power supply. It is an object of the present invention to provide an electric power steering device that can be used.
It is an object of the third invention to provide an electric power steering device that can charge an auxiliary power supply even when the main power supply and the auxiliary power supply are disconnected.
In the fourth aspect of the invention, when a sufficient current can be supplied from the second power source as the auxiliary power source to the steering assist motor, charging and discharging of the first power source is suppressed and a sufficient current is supplied from the second power source to the motor. An object of the present invention is to provide an electric power steering device that can add a first power source as an auxiliary power source when it cannot be supplied.

  An electric power steering apparatus according to a first aspect of the present invention includes a main power source composed of a generator and a battery, a steering assist motor driven by a drive circuit to which an output voltage of the main power source is applied, the main power source and the drive An electric power steering device that includes an auxiliary power source that is connected in parallel to a circuit and assists a current that flows to the motor, and that controls a current that flows to the motor based on a steering torque applied to a steering member. A detector for detecting a current flowing from the power source into the drive circuit; and a main cutting means for disconnecting the main power source from the drive circuit and the auxiliary power source when the detector does not detect a current flowing into the drive circuit; It is characterized by providing.

  The electric power steering apparatus according to a second aspect of the present invention is the first determination means for determining whether or not the current value detected by the detector is equal to or less than the first current value, and the first determination means is equal to or less than the first current value. If it is determined that the auxiliary power source is present, the auxiliary power source includes an auxiliary disconnecting unit that disconnects the auxiliary power source from the main power source and the drive circuit.

  According to a third aspect of the present invention, there is provided an electric power steering apparatus comprising: means for charging the auxiliary power supply from the main power supply when the auxiliary cutting means disconnects the auxiliary power supply from the main power supply and the drive circuit. .

  In the electric power steering apparatus according to a fourth aspect of the present invention, the auxiliary power source includes a first power source and a second power source, and the auxiliary disconnecting means includes a first power source and a second power source, respectively, from the main power source and the driving circuit, respectively. A second detector for detecting a current flowing out from the second power source; and a current value detected by the second detector is equal to or less than a second current value. Second determining means for determining whether or not the first determining means disconnects the first power supply when the first determining means determines that the first determining means exceeds the first current value, 2 When the determination means determines that the current value is less than or equal to the second current value, the first power supply is not cut off.

  According to the electric power steering apparatus of the first invention, when the detector detects the current flowing into the drive circuit from the main power supply and the auxiliary power supply, and the detector does not detect the current flowing into the drive circuit, the main disconnection Since the means disconnects the main power supply from the drive circuit and the auxiliary power supply, the regenerative current returned to the power supply side is supplied only to the auxiliary power supply, shortening the charging time of the auxiliary power supply and returning to the state where the steering assist is possible It is possible to realize an electric power steering device that can speed up the process.

  According to the electric power steering apparatus of the second invention, when the first determination unit determines that the current value detected by the detector is equal to or less than the first current value, the auxiliary disconnecting unit uses the auxiliary power source as the main power source and Since it is disconnected from the drive circuit, charging and discharging of the auxiliary power supply is suppressed at light loads when the auxiliary power supply is not required, and current is supplied from the auxiliary power supply to the steering assist motor at heavy loads when the auxiliary power supply is required. An electric power steering apparatus capable of supplying the power can be realized.

  According to the electric power steering apparatus according to the third aspect of the present invention, the auxiliary power source includes a means for charging the auxiliary power source from the main power source when the auxiliary power source is disconnected from the main power source and the drive circuit. An electric power steering device that can charge the auxiliary power supply even when disconnected is realized.

  According to the electric power steering apparatus according to the fourth aspect of the invention, the auxiliary power source includes the first power source and the second power source, and the auxiliary cutting means disconnects the first power source and the second power source from the main power source and the drive circuit, respectively. When the second detector detects a current flowing out from the second power source and the first determination unit determines that the first current value exceeds the first current value, the first detector includes a first cutting unit and a second cutting unit. When the cutting means cuts off the first power supply and the second judging means judges that the current value detected by the second detector is equal to or smaller than the second current value, the first cutting means cuts off the first power supply. Therefore, when a sufficient current can be supplied from the second power source as the auxiliary power source to the steering assist motor, charging / discharging of the first power source is suppressed and sufficient power is supplied from the second power source to the motor. When current cannot be supplied, use the first power supply as an auxiliary power supply. It is possible to realize an electric power steering apparatus that can be added.

Hereinafter, the present invention will be described with reference to the drawings showing embodiments thereof.
(Embodiment)
FIG. 1 is a block diagram showing a main configuration of an electric power steering apparatus according to the present invention.
In this electric power steering apparatus, the torque sensor 10 detects the steering torque applied to the steering member 23 (steering wheel, steering wheel). The detected steering torque value has a positive / negative sign indicating the steering direction, and is supplied to the phase compensator 12. The steering torque value phase-compensated by the phase compensator 12 is given to a torque-current table 16 of an ECU (Electric Control Unit) 25. The vehicle speed value detected by the vehicle speed sensor 11 is also given to the torque-current table 16.

  In the torque-current table 16, when the steering torque value exceeds a predetermined dead zone, the target value of the motor current increases proportionally with the increase of the steering torque value, and when the steering torque value becomes more than the predetermined value, the target value is reached. The function that saturates is variably determined according to the vehicle speed value. The function is determined so that the ratio of the target value of the motor current to the steering torque value becomes smaller and the saturation value of the target value becomes smaller as the vehicle speed value becomes larger.

The target value of the motor current determined by the torque-current table 16 is given to the subtracting means 21 as a target value in motor control.
The command current direction designating unit 19 creates a rotation direction command signal indicating the steering assist direction based on the sign of the steering torque value given from the torque-current table 16 and gives it to the motor drive circuit (drive circuit) 13. .

The motor drive circuit 13 is supplied with the output voltage of the in-vehicle battery 26 and the output voltage of an alternator (on-vehicle generator, AC generator) 34 linked to an engine (not shown) as a main power supply through the relay contact 15a. The output voltage of the alternator 34 is held at a constant voltage by an added regulator and is rectified to a direct current.
The motor drive circuit 13 is also supplied with output voltages of the auxiliary power source (first power source) 29 and the auxiliary power source (second power source) 32 through the relay contacts 27a and 30a, respectively. Further, a protection circuit 28 for preventing overcharge and overdischarge is connected in series to the auxiliary power source 29.

  The auxiliary power supplies 29 and 32 are a lithium ion battery and a large-capacity capacitor (electric double layer capacitor), respectively, but are not limited thereto, and a secondary battery such as a lead storage battery or other capacitors may be used. The auxiliary power supplies 29 and 32 are charged by the in-vehicle battery 26 and the alternator 34 through the diodes 33a and 33b, respectively, and are charged by the regenerative current flowing back from the motor drive circuit 13 through the relay contacts 27a and 30a, respectively.

The motor 18 for assisting steering is a brushless DC motor in the present embodiment, and includes a rotor position detector 14 for detecting the rotor position. The rotor position signal output from the rotor position detector 14 is a motor drive circuit. 13 is given.
The motor current detection circuit (detector) 17 detects a current flowing through the motor 18 as a current flowing into the motor drive circuit 13 and supplies the detected current value to the subtracting means 21 and the control unit 20 in the ECU 25.
The subtracting means 21 calculates a deviation between the target value of the motor current determined by the torque-current table 16 and the current value detected by the motor current detection circuit 17, and gives the calculated deviation to the current PI control unit 22.

The current PI control unit 22 calculates a voltage to be applied to the motor 18 for PI control based on the given deviation, and supplies it to a PWM (Pulse Width Modulation) modulation unit 24.
The PWM modulation unit 24 performs pulse width modulation on the applied voltage, and applies the pulse width modulated voltage to the motor drive circuit 13 as a PWM value command signal.
The control unit 20 is given the current value detected by the motor current detection circuit 17 and the current value detected by the current detector (second detector) 31. Based on the given current values, the relay drive circuit On / off control of 15, 27 and 30 is performed. Even when the motor 18 is not assisting in steering, since a leakage current flows into the motor drive circuit, the motor current detection circuit 17 does not detect the current flowing into the motor drive circuit 13 (zero). In the case of a value), the regenerative current is returned from the motor 18.

Further, the control unit 20 is given an on / off signal of an ignition switch (IG switch) 33, and every time the IG switch 33 is turned on / off, the relay drive circuit 15 is turned on / off to turn on the relay contact 15a. / Off (close / open) and relay drive circuits 27 and 30 are turned off, and relay contacts 27a and 30a are turned off (closed).
The phase compensator 12, the torque-current table 16, the subtracting means 21, the command current direction specifying unit 19, the control unit 20, the current PI control unit 22, and the PWM modulation unit 24 in the ECU 25 described above are realized by a microcomputer. ing.

  FIG. 2 is a block diagram showing a configuration example of the motor 18, the motor drive circuit 13, the motor current detection circuit 17, and the power supply system of the electric power steering apparatus shown in FIG. The motor 18 that is a brushless motor includes a stator 18a in which one terminal of each of the coils A, B, and C is star-connected, and a rotor (rotor) 18b that is rotated by a rotating magnetic field generated by the coils A, B, and C. And a rotor position detector (rotary encoder) 14 for detecting the rotational position of the rotor 18b.

  The motor drive circuit 13 includes transistors Q1 and Q2 connected in series between a positive terminal and a ground terminal and diodes D1 and D2 connected in series in the opposite direction in parallel, and transistors Q3 and Q3 connected in series. Q4 and diodes D3 and D4 connected in series in the reverse direction are connected in parallel, and transistors Q5 and Q6 connected in series and diodes D5 and D6 connected in series in the reverse direction are connected in parallel.

  The other terminal U of the star-connected coil A is connected to the common connection node of the transistors Q1 and Q2 and the common connection node of the diodes D1 and D2, and the common connection node of the transistors Q3 and Q4 and the diode D3 The other terminal V of the coil B that is star-connected is connected to the common connection node of D4, and star-connected to the common connection node of the transistors Q5 and Q6 and the common connection node of the diodes D5 and D6. The other terminal W of the coil C is connected.

  The rotational position of the rotor 18b detected by the rotor position detector 14 is notified to the gate control circuit 13a. A rotation direction command and a motor current command value (PWM command value) are given from the ECU 25 to the gate control circuit 13a. The gate control circuit 13a turns on / off the gates of the transistors Q1 to Q6 according to the rotation direction command and the rotation position of the rotor 18b, for example, U-V, U-W, V-W, V- Like U, W-U, and W-V, the path of the current flowing through the stator 18a is switched to generate a rotating magnetic field. The rotor 18b is a permanent magnet and rotates by receiving a rotational force from the rotating magnetic field.

The gate control circuit 13a also performs increase / decrease control of the rotational torque of the brushless motor by performing PWM control of on / off of the transistors Q1 to Q6 according to the motor current command value (PWM command value).
The diodes D1 to D6 are for absorbing noise generated by turning on / off the transistors Q1 to Q6.
As described above, the motor current detection circuit 17 detects the current flowing through the brushless motor and supplies the detected current value of the motor 18 to the ECU 25.

  The positive voltage side terminal of the motor drive circuit 13 is supplied with the output voltage of the in-vehicle battery 26 and the alternator 34 as the main power supply through the relay contact 15a, and the output voltage of the auxiliary power supplies 29 and 32 is connected to the relay contacts 27a and 30a, respectively. Given through. The auxiliary power supplies 29 and 32 are charged from the in-vehicle battery 26 and the alternator 34 through the diodes 33a and 33b, respectively. The output current value of the auxiliary power supply 32 detected by the current detector 31 is given to the control unit 20.

  The relay contacts 27a and 30a are connected to the relay drive circuits 27 and 30 from the control unit 20 (FIG. 1) based on the current value detected by the motor current detection circuit 17 and the “input / output” of the current to the motor drive circuit 13, respectively. On / off control. The relay contact 27 a is also turned on / off from the control unit 20 via the relay drive circuit 27 based on the current value detected by the current detector 31.

Hereinafter, an example of the operation of the electric power steering apparatus having such a configuration will be described with reference to the flowcharts shown in FIGS. 3 and 4. In the microcomputer of the control unit 20, the ON / OFF states of the relay contacts 27a and 30a are stored in FLG1 and FLG2, respectively.
The control unit 20 determines whether or not the IG switch 33 is turned on (S1), and waits when it is determined that the IG switch 33 is not turned on (S1: NO). When it is determined that the IG switch 33 is turned on (S1: YES), the control unit 20 turns on the relay drive circuit 15 and turns on (closes) the relay contact (main power relay contact) 15a (S2). . Thereafter, the relay drive circuit 27 is turned off, the relay contact (first power relay contact) 27a is turned off (open) (S3), the relay drive circuit 30 is turned off, and the relay contact (second power relay contact) ) 30a is turned off (open) (S4). Further, “0” is written in FLG1 and FLG2 in order to store the OFF of each relay contact (S5).
Next, the control unit 20 determines “Yes / No” of the current (Im) flowing into the motor drive circuit 13 (S6).

When it is determined that the current (Im) flowing into the motor drive circuit 13 is “none” (S6: NO), the control unit 20 turns off the relay drive circuit 15 and turns off the relay contact (main power relay contact) 15a. (Open) (S7). Thereafter, the relay drive circuit 27 is turned on and the relay contact (first power relay contact) 27a is turned on (closed) (S8), and the relay drive circuit 30 is turned on and the relay contact (second power relay contact). ) 30a is turned on (closed) (S9). As a result, the regenerative current returned from the motor drive circuit 13 does not flow into the in-vehicle battery 26 and the alternator 34, but flows into the auxiliary power source (first power source) 29 and the auxiliary power source (second power source) 32. Used for charging.
Next, the control unit 20 determines “present / not present” of the current (Im) flowing into the motor drive circuit 13 (S10), and stands by when it is determined “not present” (S10: NO). When it determines with "present" (S10: YES), the control part 20 returns a process to step S2.

  When it is determined in step S6 that the current (Im) flowing into the motor drive circuit 13 is “ON” (S6: YES), the control unit 20 determines that the current value (Im) detected by the motor current detection circuit 17 is the first value. It is determined whether or not the current value is 1 or less (a range that does not require an auxiliary power supply) (S11). When it is determined that Im exceeds the first current value (S11: NO), the control unit 20 determines whether FLG1 indicating ON of the relay contact 27a is “1” (S12). When it is determined that FLG1 is “1” (S12: YES), since at least the auxiliary power supply 29 is already connected to the motor drive circuit 13, the control unit 20 returns the process to step S6.

  When determining that FLG1 is not “1” (S12: NO), the control unit 20 determines whether FLG2 indicating ON of the relay contact 30a is “1” (S13). When it is determined that FLG2 is not “1” (S13: NO), the control unit 20 first turns on the relay drive circuit 30 and turns on (closes) the relay contact (second power supply relay contact) 30a (S14). ). Thus, the auxiliary power source (second power source) 32 is connected to the motor drive circuit 13 prior to the auxiliary power source (first power source) 29. Thereafter, “1” is written in FLG2 in order to memorize ON of the relay contact 30a (S15). Next, in order to wait for the relay contact 30a to be actually turned on, the control unit 20 determines whether 10 mS has elapsed since the relay drive circuit 30 was turned on (S16), and 10 mS has not elapsed. Is determined (S16: NO), it waits. In addition, the time to wait for progress is not limited to 10 mS, but may be determined according to the response speed of the relay drive circuit 30 and the relay contact 30a.

  When it is determined that 10 mS has elapsed since the relay drive circuit 30 was turned on (S16: YES), or when FLG2 is determined to be “1” in step S13 (S13: YES), the control unit 20 The output current value (Is) of the auxiliary power source (second power source) 32 detected by the detector 31 is equal to or smaller than the second current value smaller than the first current value (the range in which the output current as the auxiliary power source is insufficient). It is determined whether or not (S17). When it determines with Is exceeding a 2nd electric current value (S17: NO), the control part 20 returns a process to step S6. When it is determined that Is is equal to or smaller than the second current value (S17: YES), the control unit 20 turns on the relay drive circuit 27 and turns on (closes) the relay contact (first power relay contact) 27a. (S18). As a result, the auxiliary power source (first power source) 29 is connected to the motor drive circuit 13. Thereafter, “1” is written to FLG1 in order to store ON of the relay contact 27a (S19). Next, the control unit 20 returns the process to step S6.

  When it is determined in step S11 that Im is equal to or smaller than the I-th current value (S11: YES), the control unit 20 determines whether FLG1 indicating ON of the relay contact 27a is “1” (S20). ). When it is determined that FLG1 is “1” (S20: YES), the control unit 20 turns off the relay drive circuit 27 and turns off (opens) the relay contact (first power supply relay contact) 27a. As a result, the auxiliary power source (first power source) 29 is disconnected from the motor drive circuit 13. Thereafter, “0” is written to FLG1 in order to store the relay contact 27a OFF (S22).

  When the process of step S22 is completed, or when it is determined in step S20 that FLG1 is not “1” (S20: NO), the control unit 20 indicates that FLG2 indicating ON of the relay contact 27a is “1”. It is determined whether or not (S23). When it is determined that FLG2 is “1” (S23: YES), the control unit 20 turns off the relay drive circuit 30 and turns off (opens) the relay contact (second power supply relay contact) 30a (S24). ). Thereby, the auxiliary power supply (second power supply) 32 is disconnected from the motor drive circuit 13. Thereafter, “0” is written to FLG2 in order to store the relay contact 30a off (S25). Next, the control unit 20 returns the process to step S6.

It is a block diagram which shows the principal part structure of embodiment of the electric power steering apparatus which concerns on this invention. It is a block diagram which shows the structural example of the motor shown in FIG. 1, a motor drive circuit, a motor current detection circuit, and a power supply system. It is a flowchart which shows the example of operation | movement of the electric power steering apparatus which concerns on this invention. It is a flowchart which shows the example of operation | movement of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Torque sensor, 13 Motor drive circuit (drive circuit), 15 Relay drive circuit (main cutting means), 15a Relay contact (main cutting means), 16 Torque-current table, 17 Motor current detection circuit (detector), 18 ( Motor for steering assistance, 20 control unit, 23 steering member, 25 ECU, 26 on-vehicle battery, 27 relay drive circuit (auxiliary cutting means, first cutting means), 27a relay contact (auxiliary cutting means, first cutting means) , 28 Protection circuit, 29 Auxiliary power supply (first power supply), 30 Relay drive circuit (auxiliary disconnection means, second disconnection means), 30a Relay contact (auxiliary disconnection means, second disconnection means), 31 Current detector (second Detector), 32 auxiliary power source (second power source), 33a diode, 33b diode, 34 alternator (on-vehicle generator, AC generator)

Claims (4)

A main power source composed of a generator and a battery, a steering assist motor driven by a drive circuit to which an output voltage of the main power source is applied, and the main power source and the drive circuit are connected in parallel to flow through the motor An electric power steering device comprising an auxiliary power source for assisting current and controlling the current flowing to the motor based on a steering torque applied to the steering member;
A detector for detecting a current flowing from the main power supply and the auxiliary power supply into the drive circuit;
An electric power steering apparatus comprising: main cutting means for cutting off the main power supply from the drive circuit and the auxiliary power supply when the detector does not detect a current flowing into the drive circuit. First determination means for determining whether a current value detected by the detector is equal to or less than a first current value;
An auxiliary disconnecting means for disconnecting the auxiliary power source from the main power source and the drive circuit when the first determining means determines that the current value is less than or equal to the first current value;
The electric power steering apparatus according to claim 1, further comprising:   3. The electric power steering apparatus according to claim 2, further comprising means for charging the auxiliary power source from the main power source when the auxiliary power source is disconnected from the main power source and the drive circuit. The auxiliary power source includes a first power source and a second power source,
The auxiliary cutting means comprises a first cutting means and a second cutting means for cutting the first power supply and the second power supply from the main power supply and the driving circuit, respectively,
Furthermore,
A second detector for detecting a current flowing out of the second power source;
Second determination means for determining whether or not the current value detected by the second detector is equal to or less than the second current value;
The first disconnecting unit disconnects the first power source when the first determination unit determines that the first determination unit exceeds the first current value, and the second determination unit determines that the second determination unit is equal to or less than the second current value. The electric power steering apparatus according to claim 2 or 3, wherein the first power source is not cut off.

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