JP2004322863A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of realizing smooth steering feeling without varying auxiliary steering force without generating microvibration even in a state where the direction of a motor electric current is abruptly changed in the case when abrupt steering is continued, etc. <P>SOLUTION: This electric power steering device is furnished with a motor driving control circuit 9 to drive a motor 7 to generate auxiliary torque in accordance with steering torque, the motor driving control circuit is constituted of a bridge circuit having a plurality of FETs 30A, 30B, 31A, 31B and booster circuits 39a, 39b are provided in each of branches including the FET on the high electric potential side of this bridge circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device, and more particularly to an electric power steering device that reduces the steering force burden on a driver by applying the power of a motor to a steering system.
[0002]
[Prior art]
2. Description of the Related Art An electric power steering device is a support device that assists a steering force by linking a motor when a driver operates a steering wheel (steering wheel) while driving an automobile. In an electric power steering device, a motor control is performed by using a steering torque signal from a steering torque detection unit that detects a steering torque generated on a steering shaft by a driver's steering wheel, and a vehicle speed signal from a vehicle speed detection unit that detects a vehicle speed. Based on the control operation of the section (motor drive control circuit), the assisting motor that outputs the auxiliary steering force is PWM-driven to reduce the driver's steering force.
[0003]
In the control operation of the motor control unit, a target current value of a motor current to be supplied to the motor is set based on the steering torque signal and the vehicle speed signal, and a signal (a target current signal) relating to the target current value is actually transmitted to the motor. A difference from a motor current signal from a motor current detection unit for detecting a flowing motor current is obtained, a proportional / integral compensation process (PI control) is performed on the difference signal, and a signal for driving and controlling the motor is generated. I have.
[0004]
In the layout of the actual components related to the electric power steering device described above, the steering force assisting motor is installed near the steering shaft so as to apply the rotating force to the steering shaft and the like, and further configures the motor control unit. The circuit board provided with the electronic circuit to be mounted is mounted in a state attached to the motor. As the motor, a brushed motor or a brushless motor is used.
[0005]
In the above-mentioned electric power steering apparatus, for example, as shown in FIG. 8, the motor control unit for controlling the driving of the brush motor includes, for example, four field effect transistors (hereinafter, referred to as FETs) 211, 212, 213, and An H-type bridge circuit composed of an H. 214 and a bridge drive circuit (not shown) for applying a drive signal voltage (gate voltage) to the gate of the FET (see Patent Document 1).
[0006]
The motor M is driven and controlled based on a PWM drive control signal output from a bridge drive circuit including a microcomputer. A battery (power supply) V is connected between input terminals of the H-type bridge circuit, and a motor M is connected between output terminals. By driving the second FET 212 of the FET 211, 214 or 222 based on the PWM drive control signal, the rotation direction of the motor M is controlled. For example, when the FETs 211 and 214 are conductive, current flows through the FET 211, the motor M, and the FET 214, and a current flows in the motor M in the positive direction.
[0007]
The magnitude of the motor current is controlled by driving the FET 211 (or FET 212) with a PWM drive control signal (pulse width modulation signal) having a duty ratio determined based on the difference between the target current signal and the motor current signal. You. In particular, in the H-type bridge circuit shown in FIG. 8, a booster circuit 215 is provided for the FETs 211 and 212 on the high potential side, and the FETs 211 and 212 are driven via the booster circuit 215. Thereby, a smooth steering feeling is obtained.
[0008]
[Patent Document 1]
Japanese Patent No. 2864474
[0009]
[Problems to be solved by the invention]
In the electric power steering apparatus having the motor drive control circuit configured by the H-type bridge circuit as described above, the direction of the current supplied to the motor M is changed to a sharp steering when the sharp steering is continued. It will switch accordingly. At this time, even if the FET changes from on to off, power may be supplied to the off FET under the influence of the impedance of the motor drive control circuit and the circuit pattern. In particular, as shown in FIG. 8, when there is one booster circuit 215, the power of the booster circuit 215 is also supplied to the circuit portion on the off side due to the influence of the impedance of the circuit pattern and the like, and the response becomes slow. Further, there has been a case where the output from the booster circuit to be supplied to the FET that is turned on fluctuates. This fluctuation had a bad influence on the steering feeling.
[0010]
Here, attention is focused on one FET. FIG. 9 is a diagram illustrating an FET, a voltage value applied to the FET, and a current value flowing through the FET. The voltage applied between the drain and source is V_DSAnd the voltage applied between the gate and the source is V_GSAnd the current flowing from the drain to the source is represented by I_DIs shown. The temperature of the FET is T [° C.].
[0011]
In the above-described voltage fluctuation due to the rapid steering, the gate-source voltage V_GSWhen the current drops, the on-resistance R of the FET is_DSAnd the FET may not be turned on. FIG. 10 shows the voltage V between the drain and the source._DSAnd the current I flowing through the FET_DWith the voltage V between the gate and the source._GSFIG. 3 is a diagram showing as parameters. FET ON resistance R_DSIs V_DS/ I_DIs calculated.
[0012]
The voltage V between the gate and the source of the FET when the voltage is reduced by the voltage fluctuation due to rapid steering._GSIs 5 [V] in FIG. 10, for example, the current I necessary to turn on the FET is_{D T}Can not flow. Voltage V_GSIs 5 [V], no matter how much the voltage V_DSThe current I required to drive the FET_{D T}Can not flow. On the other hand, the motor control unit controls to keep the current flowing through the FET constant based on the feedback of the motor current signal from the motor current detection unit that detects the motor current flowing through the motor M. In this case, the Joule heat ( Q = I²Rt) occurs, and the temperature of the FET rises. As a result, the on-resistance R_DSWill be higher. That is, the difference between the fed-back motor current and the target current set in the motor control unit becomes large, so that the motor control unit attempts to flow a large current.
[0013]
FIG. 11 shows the on-resistance R_DSFIG. 3 is a diagram showing a relationship between temperature and temperature [° C.]. Temperature T_FETWhen the ON resistance R_DSIs 1 [Ω]. As the temperature rises, the on-resistance R_DSIs higher. A large current flows through the FET by the motor control unit that performs the feedback control of the motor current, and as a result, the temperature of the FET rises and the on-resistance of the FET increases, resulting in a circulation. In addition, such a process may cause a slight vibration (hunting) in the motor current.
[0014]
As described above, as a result of the voltage fluctuating due to rapid steering, the on-resistance R of the FET is reduced._DSAnd the voltage for driving the motor fluctuates, affecting the steering feeling. Also, the on-resistance R of the FET_DSAs the FET becomes higher, the FET itself generates heat and becomes higher in temperature, so that the on-resistance R_DSAnd a slight vibration (hunting) of the motor current occurs, so that a smooth steering feeling may not be obtained.
[0015]
An object of the present invention is to solve the above-described problem. In a case where the direction of the motor current is suddenly switched, for example, when rapid steering is continuously performed, a slight vibration of the motor current occurs. An object of the present invention is to provide an electric power steering device that realizes a smooth steering feeling without any change in the auxiliary steering force.
[0016]
Means and action for solving the problem
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0017]
An electric power steering apparatus according to the present invention (corresponding to claim 1) is an electric power steering apparatus including a motor drive control circuit that performs PWM driving of a motor that generates an auxiliary torque corresponding to a steering torque. The circuit includes a bridge circuit having a plurality of switching elements (field effect transistors), and a booster circuit for a gate drive signal is provided for each of the branches including the switching element on the high potential side of the bridge circuit. And
[0018]
A gate drive signal booster circuit is provided for each of the branches including the switching element on the high-potential side of the bridge circuit, so that the direction of the motor current suddenly switches when sudden steering is continued. Even in the situation, the output from the booster circuit to be supplied to the FET on the side to be turned on does not fluctuate, the on-resistance of the FET does not increase due to the voltage drop of the gate drive signal of the FET, and the motor current is reduced. The occurrence of micro vibration can be suppressed, and the steering feeling is improved. Here, the branch includes a branch formed by connecting a plurality of switching elements in parallel.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0020]
With reference to FIG. 1 and FIG. 2, a main configuration and an electronic circuit of a mechanical mechanism of the electric power steering apparatus according to the present invention will be described. FIG. 1 is a main part configuration diagram of a mechanical mechanism of the electric power steering device according to the present invention. The electric power steering device includes an input shaft 1, a steering speed detecting unit 2, a steering torque detecting unit 3, a rack shaft 4, a ball recirculating nut (ball screw) 5, a brushed motor 7, a microcomputer unit (MCU) 8, and a motor. And a drive circuit 9 and a power supply circuit 9A.
[0021]
One end of the input shaft 1 is connected to a steering wheel via a universal joint (not shown), and a pinion gear 1b is integrally attached to the other end. The rack shaft 4 meshes with the pinion 1b, and converts the rotational displacement of the input shaft 1 into the axial displacement of the rack shaft 4. Both ends of the rack shaft 4 are respectively connected to ball joints, tie rods, and knuckles (not shown) to change the steering of the wheels.
[0022]
Here, a load acts on the rack shaft 4, and when the load is large, the pinion 1 b rotates around a portion meshing with the rack shaft 4. For example, when the input shaft 1 is rotated by applying a torque in the direction of arrow X, the torsion bar 15 is twisted according to the magnitude of the torque, and the pinion holder 12 is rotated in the direction of arrow Y. The rotational displacement at this time is proportional to the torque applied to the input shaft 1, that is, the steering torque.
[0023]
Therefore, the movable core 16 is converted into the displacement Z in the axial direction by the pin 11b. That is, the steering torque is proportional to the axial displacement of the movable iron core 16, and the axial displacement is detected by the coil unit 17.
[0024]
As described above, the steering torque detecting unit 3 includes the pinion gear 1b, the rack shaft 4, the pinion holder 12, the pin 11b, the movable core 16, and the differential transformer, and detects the magnitude and direction of the steering torque. .
[0025]
The input shaft 1 is integrally provided with a light shielding plate 18 having a large number of slits 18a in the circumferential direction. Photocouplers 19 and 20 are integrally fixed to the pinion holder at positions sandwiching the light shielding plate 18. Have been.
[0026]
Light passing through the slit 18a of the light shielding plate 18 is detected by the photocouplers 19 and 20, and a pulse-like electric signal is output. The mounting positions of the photocouplers 19 and 20 are provided such that the phases of the pulses differ by about 90 °. As described above, the steering speed detecting section 2 includes the light shielding plate 18 and the photocouplers 19 and 20, and detects the magnitude of the steering speed and the rotation speed thereof. It is needless to say that the steering torque detector is replaced with a torsion bar type or a magnetostrictive torque sensor.
[0027]
A thrust bearing 22 fixed to the rack case is provided at one end of the nut 21, and a pulley 23 having a V-shaped cross section is integrally provided at the other end of the nut 21. Further, a thrust bearing (not shown) fixed to the rack case is provided on an end surface of the pulley 23, and the nut 21 is supported so as to be axially immovable and rotatable.
[0028]
A pulley 24 having a V-shaped section is mounted along the pulley 23 on the rotating shaft of the motor 7 with a brush. A V-belt 25 is suspended between the pulley 23 and the pulley 24. I have. The brushed motor 7 is supported on the vehicle body via an elastic member. Therefore, the rotation of the motor with brush 7 displaces the rack shaft 4 in the axial direction through the rotation of the ball screw 5.
[0029]
On the other hand, the control means comprises a power supply circuit 9A, a microcomputer unit 8, and a motor drive circuit 9. Power is supplied to the photocouplers 19 and 20 through the microcomputer unit 8, and outputs from the photocouplers 19 and 20 are input to the microcomputer unit 8.
[0030]
The power supply circuit 9A includes a relay circuit 28 connected to the + terminal of the on-vehicle battery 26 via a fuse 27. The relay circuit 28 is turned on / off by a PWM drive control signal T1 from the microcomputer unit 8. Power is supplied to the motor drive circuit 9 from the output side of the relay circuit 28.
[0031]
FIG. 2 is an electronic circuit diagram of the motor drive circuit 9. Here, FIG. 2 clearly shows the motor 7 so that the connection relationship with the motor 7 can be recognized. The motor drive circuit 9 includes a bridge circuit composed of FETs 30A, 30B, 31A, 31B. Here, the branch including the switching element on the high potential side refers to a branch including the FET 30A and a branch including the FET 31A. A booster circuit 39a and a booster circuit 39b are provided for these branches, respectively. FETs 30A and 30B and FETs 31A and 31B located on opposing sides of the bridge circuit operate as a set.
[0032]
The drain terminals of the FETs 30A and 31A are connected, and this connection is connected to the output side of the relay circuit 28, while the source terminals of the FETs 30B and 31B are connected, and this connection is connected via the resistor 32 to the common side ( Ground), and these connection portions become input terminals.
[0033]
The gate terminal of the FET 30A is connected via a resistor 33 to the collector of a transistor 34 whose emitter is grounded. The PWM drive control signal T4 from the microcomputer unit 8 is input to the base thereof. Similarly, the gate terminal of the other FET 31A is connected via a resistor 35 to the collector of a transistor 36 whose emitter is grounded. The PWM drive control signal T5 from the microcomputer unit 8 is input to its base. Reference numerals 51 and 52 are FET drive circuits provided in the MCU 8.
[0034]
The collector of the transistor 34 is connected via a resistor 37 to a booster circuit 39a connected to the output side of the relay circuit 28, and is supplied with an operating power supply voltage that is approximately doubled by the booster circuit 39a. . The collector of the transistor 36 is connected via a resistor 38 to a booster circuit 39b connected to the output side of the relay circuit 28, and is supplied with an operating power supply voltage that is approximately doubled by the booster circuit 39b. ing. Since the booster circuits 39a and 39b for the gate drive signal are provided for each of the high-potential side FETs 30A and 31A, the high-potential side FETs 30A and 31A are connected to the high-potential side FETs 30A and 31A even if the voltage fluctuates due to a sudden sudden steering. The boosted power supply voltage for operation is supplied, and the FETs 30A and 31A are reliably turned on and off, so that the steering feeling is improved as compared with the related art.
[0035]
The PWM drive control signal T2 from the microcomputer unit 8 is input to the gate terminal of the FET 30B via the resistor 40, while the PWM drive control signal T3 from the microcomputer unit 8 is connected to the gate terminal of the FET 31B via the resistor 41. Is input, and the FET 30B or 31B is PWM-driven by the PWM drive control signal T2 or T3.
[0036]
Therefore, for example, the PWM drive control signal T4 is set to "L level", the PWM drive control signal T2 is set to "PWM signal", and in this case, the other PWM drive control signals T5 are set to "H level" and T3 is set to "L level". Conversely, the PWM drive control signal T5 is set to "L level", the PWM drive control signal T3 is set to "PWM signal", and in this case, the other PWM drive control signals T4 are set to "H level" and T2 is set to "L level". Thus, the rotation direction of the brushed motor 7 is controlled, and appropriate control power is supplied to the brushed motor 7 by the pulse width control of the PWM drive control signal T4 or the PWM drive control signal T5.
[0037]
Next, another embodiment of the present invention is shown in FIG. FIG. 3 is a diagram showing a motor drive circuit 9 of the electric power steering device according to the present invention. Here, FIG. 3 clearly shows the motor 7 so that the connection relationship with the motor 7 can be recognized. The motor drive circuit 9 is configured by connecting FETs having a small current capacity in parallel to form a bridge circuit. That is, similar FETs 42A, 42B, 43A, 43B are connected in parallel to the source and drain terminals of the FETs 30A, 30B, 31A, 31B of the previous embodiment, respectively. Reference numerals 51 and 52 schematically show FET drive circuit units provided in the MCU 8 for transmitting a PWM drive control signal. Here, the branch including the switching element on the high potential side refers to a branch including the FET 30A and the FET 42A connected in parallel, and a branch including the FET 31A and the FET 43A connected in parallel. A booster circuit 39a and a booster circuit 39b are provided for these branches, respectively.
[0038]
The FET drive circuit 51 receives the power supply voltage for operation boosted by the booster circuit 39a and supplies it to the gates of the FET 30A and the FET 42A. The FET drive circuit 52 also receives the operating power supply voltage boosted by the booster circuit 39b and supplies the same to the gates of the FETs 31A and 43A. Further, the on-resistance between the source and the drain of each of the FETs 30A and 42A, 30B and 42B, 31A and 43A, and 31B and 43B connected in parallel is further reduced, and the power loss can be further reduced.
[0039]
As described above, in the present embodiment of the electric power steering apparatus using the brush motor, the booster circuit is provided for each of the branches including the FET on the high potential side, so that the case where the rapid steering is continued. Even if there is, the power supply voltage for operation can be reliably supplied to the gate of the FET on the high potential side. Further, since a booster circuit is provided for each of the FETs on the high potential side, there is no difference in impedance depending on the circuit pattern, and the responsiveness is improved.
[0040]
Next, an electric power steering device including a brushless motor will be described. With reference to FIGS. 4 to 7, a description will be given of a main configuration of a mechanical mechanism of the electric power steering apparatus according to the present invention and a layout of an electronic circuit unit. FIG. 4 shows a main part of a mechanical mechanism of the electric power steering device 110 and a specific configuration of an electric system. A part of the left end and the right end of the rack shaft 114 is shown in cross section. The rack shaft 114 is slidably accommodated in the axial direction inside a cylindrical housing 131 arranged in the vehicle width direction (the horizontal direction in FIG. 4). Ball joints 132 are screw-connected to both ends of a rack shaft 114 protruding from the housing 131, and left and right tie rods 116 are connected to these ball joints 132. The housing 131 includes a bracket 133 for attaching to a vehicle body (not shown), and also includes stoppers 134 at both ends.
[0041]
In FIG. 4, reference numeral 135 denotes an ignition switch, 136 denotes a vehicle-mounted battery, and 137 denotes an alternating current generator (ACG) attached to a vehicle engine. The AC generator 137 starts generating power by the operation of the vehicle engine. Necessary electric power is supplied to the motor control device 122 from the battery 136 or the AC generator 137. The motor control device 122 is attached to the brushless motor 119. Reference numeral 138 denotes a rack end that contacts the stopper 134 when the rack shaft 114 moves, and reference numeral 139 denotes a dust seal boot for protecting the inside of the gear box from water, mud, dust, and the like.
[0042]
FIG. 5 is a sectional view taken along line AA in FIG. FIG. 5 clearly shows the support structure of the steering shaft 112, the specific configuration of the steering torque detector 120, the power transmission mechanism 118, the rack and pinion mechanism 115, and the layout of the brushless motor 119 and the motor control device 122.
[0043]
In FIG. 5, a steering shaft 112 is rotatably supported by two bearing portions 141 and 142 in a housing 124a forming the gear box 124. A rack and pinion mechanism 115 and a power transmission mechanism 118 are housed inside the housing 124a, and a steering torque detector 120 is additionally provided at an upper portion. The upper opening of the housing 124a is closed by a lid 143, and the lid 143 is fixed by bolts 144. The pinion 113 provided at the lower end of the steering shaft 112 is located between the bearings 141 and 142. The rack shaft 114 is guided by a rack guide 145, and is pressed against the pinion 113 by a contact member 147 urged by a compressed spring 146. The power transmission mechanism 118 is formed by a worm gear 149 fixed to a transmission shaft 148 coupled to an output shaft of the brushless motor 119 and a worm wheel 150 fixed to the steering shaft 112. The steering torque detection unit 120 includes a steering torque detection sensor 120a disposed around the steering shaft 112, and an electronic circuit unit 120b that electrically processes a detection signal output from the steering torque detection sensor 120a. . The steering torque detection sensor 120a is attached to the lid 143.
[0044]
FIG. 6 is a sectional view taken along line BB in FIG. FIG. 6 shows a specific configuration inside the brushless motor 119 and the motor control device 122.
[0045]
The brushless motor 119 includes a rotor 152 made of a permanent magnet fixed to the rotation shaft 151, and a stator 154 disposed around the rotor 152. The stator 154 includes a stator winding 153. The rotation shaft 151 is rotatably supported by the two bearing portions 155 and 156. The tip of the rotating shaft 151 is the output shaft 119a of the brushless motor 119. An output shaft 119a of the brushless motor 119 is coupled to a transmission shaft 148 via a torque limiter 157 so that rotational power is transmitted. As described above, the worm gear 149 is fixed to the transmission shaft 148, and the worm wheel 150 meshing with the worm gear 149 is disposed. A motor rotation angle detection unit (position detection unit) 123 that detects a rotation angle (rotation position) of the rotor 152 of the brushless motor 119 is provided at a rear end of the rotation shaft 151. The motor rotation angle detection unit 123 includes a rotor 123a fixed to the rotation shaft 151, and a detection element 123b that detects the rotation angle of the rotor 123a using a magnetic effect. For example, a resolver is used for the motor rotation angle detection unit 123. Motor currents Iu, Iv, Iw, which are three-phase alternating current, are supplied to the stator winding 153 of the stator 154. The above components of the brushless motor 119 are arranged inside the motor case 158.
[0046]
The motor control device 122 is arranged inside a control box 161 mounted outside the motor case 158 of the brushless motor 119. The motor control device 122 is configured by an electronic circuit in which electronic circuit elements are mounted on a circuit board 162. The electronic circuit elements include a one-chip microcomputer and its peripheral circuits, a pre-drive circuit, a FET bridge circuit, an inverter circuit, and the like. Motor currents Iu, Iv, Iw (drive control signals) are supplied from the motor control device 122 to the stator winding 153 of the brushless motor 119. The rotation angle signal detected by the motor rotation angle detection unit 123 is input to the motor control device 122.
[0047]
Next, a configuration of an electronic circuit of the motor control device 122 will be described with reference to FIG. FIG. 7 is a diagram showing an internal configuration of the motor control device 122 and a circuit configuration for controlling the rotation operation of the three-phase brushless motor 119.
[0048]
In the motor control device 122, a target current is set based on detection signals from the steering torque detector 120, the vehicle speed detector 121, the engine rotation detector 125, and the resolvers 123c, and the brushless motor 119 is driven. A one-chip microcomputer 171 for outputting a signal to perform the operation is provided. Detection signals from the steering torque detection unit 120, the vehicle speed detection unit 121, and the engine rotation detection unit 125 are input to the one-chip microcomputer 171 via the interface 172, and the detection signal from the resolver 123c is transmitted to the interface 173 and the RD (Resolver-Digital). The data is input to the one-chip microcomputer 171 via the conversion unit 123d. Further, a current signal relating to the motor current is fed back from the current sensors 175 and 176 to the one-chip microcomputer 171 and is input via the interface 174.
[0049]
In the brushless motor 119, it is necessary to control the amount of motor current to be supplied in accordance with the rotation angle of the rotor 152 (rotary shaft 151) of the brushless motor 119, so that the motor currents Iu, Iv, and Iw, which are three-phase AC, are required. Among them, current sensors 175 and 176 are provided in, for example, two phases to detect the amount of current supplied to the motor, and a motor rotation angle detection unit 123 is provided to detect the motor rotation angle. The brushless motor 119 outputs detection signals output from the motor rotation angle detection unit 123 and the two current sensors 175 and 176 based on a one-chip microcomputer 171 and a bridge circuit provided inside the motor control device 122. PWM driving is performed by utilizing the above.
[0050]
The motor rotation angle detection unit 123 of the brushless motor 119 includes a resolver 123c attached to the brushless motor 119 and an RD conversion unit 123d. The RD converter 123d sends the exciting current to the resolver 123c, and the output signal from the resolver 123c is sent to the RD converter 123d. The RD conversion unit 123d extracts and outputs a rotation angle signal (θ) and a rotation angular velocity signal (ω) related to the rotation position of the rotor 152 of the brushless motor 119 based on the output signal from the resolver 123c. The rotation angular velocity signal ω is fed back to the one-chip microcomputer 171.
[0051]
The motor control device 122 has a bridge circuit composed of a plurality of FETs 181, 182, 191, 192, 201 and 202 for controlling the rotation operation of the three-phase brushless motor 119, and corresponds to the U-phase, V-phase and W-phase. Each has an FET drive circuit 183, 193, 203. Here, the branch including the switching element on the high potential side refers to a branch including the FET 181, a branch including the FET 191, and a branch including the FET 201. Booster circuits 184, 194, 204 are provided for the FETs 18, 191, 201 in these branches via FET drive circuits 183, 193, 203, respectively. The FET drive circuits 183, 193, and 203 receive the supply of the boosted voltage from the boost circuits 184, 194, and 204 provided respectively, and supply the boosted operation power supply voltage to the gates of the FETs 181, 191, and 201. .
[0052]
As described above, in the present embodiment in the electric power steering apparatus using the brushless motor, since the booster circuit is provided for each of the plurality of FET drive circuits corresponding to the branch including the switching element on the high potential side, Even when the rapid steering is continued, the power supply voltage for operation can be reliably supplied to each FET. In addition, since the booster circuit is provided for each of the plurality of FET drive circuits, the ability to follow the current supplied to the FET is improved.
[0053]
【The invention's effect】
As apparent from the above description, the present invention has the following effects.
[0054]
The present invention relates to an electric power steering device including a motor drive control circuit that performs PWM drive on a motor that generates an auxiliary torque corresponding to a steering torque, wherein the motor drive control circuit is configured by a bridge circuit including a plurality of switching elements; Since a booster circuit is provided for each of the branches including the switching element on the high potential side of the bridge circuit, the switching of each high potential side can be performed even if the rapid steering is continued. The power supply voltage for operation can be reliably supplied to the element, and the occurrence of minute vibration of the motor current can be suppressed. Therefore, a smooth steering feeling can be realized without the auxiliary steering force fluctuating.
[Brief description of the drawings]
FIG. 1 is a main part configuration and an electronic circuit diagram of a mechanical mechanism of an electric power steering device according to the present invention.
FIG. 2 is a diagram showing a motor drive circuit of the electric power steering device according to the present invention.
FIG. 3 is a diagram showing a motor drive circuit of another embodiment of the electric power steering device according to the present invention.
FIG. 4 is a diagram showing a main part of a mechanical mechanism of the electric power steering device and a specific configuration of an electric system.
FIG. 5 is a sectional view taken along line AA in FIG.
6 is a sectional view taken along line BB in FIG.
FIG. 7 is a diagram showing an electric circuit configuration of the motor control device.
FIG. 8 is a diagram showing a motor control unit of a conventional electric power steering device.
FIG. 9 is a diagram showing an FET, a voltage value applied to the FET, and a current value flowing through the FET.
FIG. 10 shows a voltage V between a drain and a source._DSAnd the current I flowing through the FET_DWith the voltage V between the gate and the source._GSFIG. 3 is a diagram showing as parameters.
FIG. 11: ON resistance R_DSFIG. 3 is a diagram showing a relationship between temperature and temperature [° C.].
[Explanation of symbols]
2 Steering speed detector
3 Steering torque detector
7 Brushed motor
9 Motor drive circuit
9A power supply circuit
26 In-vehicle battery
28 relay circuit
30A, 30B, 31A, 31B FET
39a, 39b booster circuit
51,52 FET drive circuit
110 Electric power steering device
119 brushless motor
120 Steering torque detector
121 Vehicle speed detector
122 Motor control device
123 Motor rotation angle detector
183,193,203 Drive circuit
184, 194, 204 booster circuit

Claims (1)

An electric power steering device including a motor drive control circuit that performs PWM driving of a motor that generates an auxiliary torque corresponding to a steering torque,
The motor drive control circuit includes a bridge circuit having a plurality of switching elements, and a gate drive signal booster circuit is provided for each branch including the high-potential side switching element of the bridge circuit. Electric power steering device.

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