JP2009143461A - Transmission ratio variable device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission ratio variable device capable of improving steering feeling. <P>SOLUTION: MPUs (motor control means and correction duty ratio setting means) adjust duty ratios for adjustment in the on/off-control of a lower side FET (second switching element) which is not connected to an upper side FET (first switching element) in an on-state in series in lock states, and determine an output voltage from a detected voltage detected by a voltage sensor. The duty ratio when the output voltage becomes zero in a straight line passing the output voltage corresponding to the duty ratio for adjustment is set to be a correction duty ratio on the lower side FET. The MPUs bring one of the upper side FETs into an on-state based on a steering state, and perform the on/off-control of one of lower side FETs which are not connected to the upper side FET in series based on a duty ratio for driving set by adding the correction duty ratio of the lower side FET to a basic duty ratio of the lower side FET set according to the steering state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission ratio variable device that changes a turning angle of a steered wheel with respect to a steering angle of a steering according to a driving situation.

2. Description of the Related Art Conventionally, as a transmission ratio variable device that changes a steering angle of a steered wheel with respect to a steering angle of a steering according to a driving situation, for example, a vehicle steering device shown in Patent Document 1 is known. The vehicle steering apparatus includes a variable gear ratio actuator (transmission ratio variable mechanism) having a differential mechanism provided on a steering shaft and a motor that drives the differential mechanism. The variable gear ratio actuator speeds up (or decelerates) the rotation of the steering shaft accompanying the steering operation, thereby varying the gear ratio (transmission ratio) of the steered wheels with respect to the steering angle.
JP 2005-170129 A

  By the way, in the conventional transmission ratio variable device, the drive circuit for driving the motor of the transmission ratio variable mechanism includes a pair of FETs for each phase, and a gate which is a control signal input from the MPU as the motor control means. The applied voltage of the motor is adjusted by switching each FET at a predetermined timing in accordance with the voltage. At this time, since the FET is switched when the gate voltage applied to the FET exceeds a predetermined voltage, a dead zone is generated from when the gate voltage is applied until the predetermined voltage is exceeded, and the transmission ratio is changed during steering. In this case, a response delay occurs, which adversely affects the steering feeling. In order to suppress this dead zone, the MPU controls the drive circuit by adding a correction duty ratio, which is a value for raising the basic duty ratio, to the basic duty ratio set according to the steering situation. is doing.

  However, since the above-described correction duty ratio is estimated from the FET rank selected according to the difference in the ON voltage in the manufacturing process, the influence on the temperature, the power supply voltage, and the like, there is a problem that the accuracy is not good. There is also a problem that a work process for selecting FETs by rank is required.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a transmission ratio variable device capable of improving the steering feeling.

In order to achieve the above object, the variable transmission ratio device according to claim 1 is provided in the middle of a steering system of a vehicle connecting the steering wheel (12) and the steering wheels (FR, FL). A transmission ratio variable mechanism (40) capable of changing a transmission ratio between the steering wheel side input shaft (14) and the steering wheel side output shaft (16) by rotation of a motor (34), and the motor A locking means (70) capable of preventing the rotation of the input shaft and connecting the input shaft and the output shaft, a first switching element (92a to 92c) disposed on the power supply line side, and a ground line side. A plurality of pairs of switching elements connected in series with the second switching elements (92d to 92f), and the power supplied from the DC power source (B) is controlled by turning on / off the switching elements. And the second driving circuit (91) for outputting to the motor and the second switching circuit which is not connected in series to the first switching device while turning on one of the first switching devices based on the steering state. Motor control means (81) for controlling on / off of one of the switching elements based on a predetermined duty ratio (Da to Dc), the anti-power supply line side of the first switching element in the on state, and the on / off Output voltages (Vvu _H , Vvu _L , Vwv _H , Vwv _L , Vuw _H , Vuw _L ) output from the drive circuit are detected from the voltage between the second switching element to be turned off and the anti-ground line side. A transmission ratio variable device (30) comprising voltage detecting means (88u to 88w) for preventing rotation of the motor by the locking means. And adjusting the duty ratio (D2a to D2c) in the on / off control of the second switching element that is not connected in series to the first switching element in the on state, and the voltage detecting means There is a correction duty ratio setting means (81) for setting the maximum duty ratio when the detected output voltage is 0 (zero) as the correction duty ratio (D1a to D1c) for each second switching element. The predetermined duty ratio is technically characterized by being set by adding the correction duty ratio to a basic duty ratio (D0a to D0c) set according to the steering situation.

  According to the first aspect of the present invention, the correction duty ratio setting means includes a second switching element that is not connected in series to the first switching element that is in the on state in a state where the rotation driving of the motor is blocked by the lock means. The duty ratio in the on / off control is adjusted, and the maximum duty ratio when the output voltage detected by the voltage detecting means is 0 (zero) is set as the correction duty ratio for each second switching element. . Then, the motor control means turns on one of the first switching elements based on the steering situation, and sets one of the second switching elements not connected in series to the first switching element. On / off control is performed based on a predetermined duty ratio set by adding the correction duty ratio to the basic duty ratio set in accordance with the steering situation.

On / off control of one of the second switching elements is performed based on the correction duty ratio and the basic duty ratio set in this way, and the first switching element not connected in series to the second switching element. By turning one on, the dead zone in which the output voltage output from the drive circuit becomes 0 (zero) is suppressed, so that a response delay can be eliminated when changing the transmission ratio during steering.
Therefore, the steering feeling can be improved.

  According to the second aspect of the present invention, the correction duty ratio setting means turns on / off the second switching element based on at least two duty ratios and these duty ratios in a state where the rotation driving of the motor is blocked by the lock means. In an approximate straight line obtained from at least two output voltages greater than 0 (zero) detected by the voltage detection means when controlled, the duty ratio when the output voltage becomes 0 (zero) is defined as the correction duty ratio. Each of the two switching elements is set. By using such an approximate straight line, the correction duty ratio can be set with a simple calculation.

  According to a third aspect of the present invention, the correction duty ratio setting means causes the duty ratio in the on / off control to approach 0 (zero) in a state where the rotation of the motor is blocked by the lock means. The duty ratio when the output voltage detected by the voltage detection means becomes 0 (zero) when adjusted may be set for each of the second switching elements as the correction duty ratio.

  Hereinafter, a variable transmission ratio device according to an embodiment of the present invention will be described with reference to the drawings for a vehicle control device. FIG. 1 is an explanatory diagram showing a schematic configuration of a vehicle control device 10 to which the transmission ratio variable device 30 according to the present embodiment is applied.

  As shown in FIG. 1, the vehicle control device 10 mainly includes a steering wheel 12, a first steering shaft 14, a second steering shaft 16, a steering angle sensor 18, a pinion gear 20, a rack shaft 22, a rod 24, and an ECU 80. The transmission ratio variable device 30 is configured.

  The steering wheel 12 is fixed to the first steering shaft 14, the first steering shaft 14 is connected to the input side of the transmission ratio variable device 30, and the second steering shaft 16 is connected to the output side of the transmission ratio variable device 30. Has been. The steering angle sensor 18 detects the steering angle θs and outputs a detection signal corresponding to the steering angle to the ECU 80.

  The pinion gear 20 at the tip of the second steering shaft 16 meshes with the rack shaft 22, and the rotational motion of the second steering shaft 16 is converted into the linear motion of the rack shaft 22. A rod 24 is connected to both ends of the rack shaft 22, and steering wheels FR and FL are connected to the end of the rod 24 via a knuckle (not shown). Thus, when the second steering shaft 16 rotates, the turning angle of the steered wheels FR, FL can be changed via the rack shaft 22, the rod 24, etc., so that the rotation amount and the rotation direction of the second steering shaft 16 can be changed. The steering wheels FR and FL can be steered according to the above.

FIG. 2 is a detailed sectional view of the transmission ratio variable device 30 of FIG.
The transmission ratio variable device 30 is a device that changes the steered angles of the steered wheels FR and FL with respect to the steering angle in accordance with the steering situation. The transmission ratio variable device 30 includes a motor 34 that changes a transmission ratio between the first steering shaft 14 and the second steering shaft 16 by rotational driving in housings 52, 54, and 56 that are integrally coupled. A wave gear mechanism 40 as a gear mechanism, a lock mechanism 70 that can connect the first steering shaft 14 and the second steering shaft 16 are provided, and a spiral cable unit 38 is provided outside the housing 52. The lower end 14a of the first steering shaft 14 is connected to a housing 52 on the input side of the transmission ratio variable device 30, so that the housing 52 and the first steering shaft 14 rotate together. On the other hand, the upper end 16 a of the second steering shaft 16 is connected to the output side of the transmission ratio variable device 30.

  The motor 34 is fixed in the housing 54 by the motor housing 46, is connected to the first steering shaft 14 via the housings 52, 54, and rotates together with the first steering shaft 14. The motor housing 46 includes a motor housing body 46a and a motor end plate 46b. A cup-shaped shaft hole 46c is formed at the center of the motor housing body 46a on the second steering shaft 16 side. A motor end plate 46b is fixed on the first steering shaft 14 side of the motor housing body 46a so as to close the opening of the motor housing body 46a.

  A stator 34S is fixed to the inner peripheral surface of the motor housing main body 46a, and a rotor 34R that is rotationally driven by a rotating magnetic field generated by energizing the coil of the stator 34S is provided in the stator 34S. A motor shaft 34A is fixed in the rotor 34R so as not to be relatively rotatable, and the motor shaft 34A protrudes from both ends of the rotor 34R in the axial direction. One end 34a of the motor shaft 34A is supported by a ball bearing 48 provided between the motor end plate 46b and the other end 34b of the motor shaft 34A is provided between the shaft hole 46c of the motor housing body 46a. It is supported by a ball bearing 58. Thereby, the motor shaft 34A can rotate coaxially with respect to the motor housing main body 46a and the housings 52, 54, and 56.

  A wave gear mechanism 40 constituted by a harmonic drive (registered trademark) is connected to the other end 34b of the motor shaft 34A. The wave gear mechanism 40 includes a wave generator 64 in which the other end 34b of the motor shaft 34A is fitted and can rotate integrally with the motor shaft 34A. The wave generator 64 includes a cam 64a having a substantially elliptical cross section perpendicular to the axis, and a ball bearing 64b provided on the outer periphery of the cam 64a. The inner ring of the ball bearing 64b is fixed to the outer periphery of the cam 64a, and the outer ring of the ball bearing 64b can be elastically deformed via the ball. An annular flexspline 66 that is elastically deformable integrally with the outer ring of the ball bearing 64b is provided on the outer periphery of the wave generator 64. External teeth 66 a are formed on the outer periphery of the flex spline 66.

  An annular stay circular spline 68 is formed on the motor 34 side in the housing 54. Inner teeth 68a having a greater number of teeth (102) than the number of teeth (100) of outer teeth 66a of the flexspline 66 are formed on the inner periphery of the stay circular spline 68, whereby the stay circular spline 68 meshes with the flexspline 66. ing.

  An annular drive circular spline 69 adjacent to the stay circular spline 68 is rotatably supported on the second steering shaft 16 side in the housing 54 via a bearing metal 54a. On the inner periphery of the drive circular spline 69, the same number (100) of inner teeth 69a as the outer teeth 66a of the flexspline 66 are formed, so that the drive circular spline 69 is also meshed with the flexspline 66.

  A protective plate 67 is provided between the motor housing body 46 a and the wave gear mechanism 40. An upper end 16 a of the second steering shaft 16 is fixed to the drive circular spline 69.

  That is, the housings 52, 54, and 56 are configured to rotate together with the first steering shaft 14, and the rotation of the first steering shaft 14 is 50 by the wave gear mechanism 40 composed of the above-described harmonic drive (registered trademark). / 51 to rotate the second steering shaft 16. On the other hand, as described above, the rotation of the motor 34 is decelerated to (1/50) × (50/51) to rotate the second steering shaft 16. Thus, the first steering shaft 14 and the second steering are rotated by adding the rotation (ACT angle θta) of the motor 34 to the rotation (steering angle θs) of the first steering shaft 14 and rotating the second steering shaft 16. The transmission ratio with the shaft 16 can be changed by the rotational drive of the motor 34.

FIG. 3 is a cross-sectional view taken along the line 3-3 shown in FIG.
The lock mechanism 70 is a mechanism capable of locking (connecting) the motor shaft 34A to the housing 52. As shown in FIGS. 2 and 3, the lock mechanism 70 is disposed on the outer periphery of one end 34a of the motor shaft 34A. Then, a lock holder 71 that rotates integrally with the motor shaft 34A, a substantially disc-shaped lock base 72 that is fixed to the motor end plate 46b, and a lock pin 73 that is parallel to the shaft center with respect to the housing 52. And a single lock lever 76 that is pivotally supported via a metal bush 74 and driven by a solenoid 75.

  A plurality of lock groove portions 71 a are formed on the outer periphery of the lock holder 71, and a single engagement claw portion 76 a that can be engaged with each lock groove portion 71 a is formed at one end of the lock lever 76. Around the lock pin 73, a first torsion coil spring 73 a is provided with one end fixed to the housing 52 and the other end fixed to the anti-lock base 72 side of the lock lever 76. Around the lock pin 73, a second torsion coil spring 73b having one end fixed to the lock base 72 side of the lock lever 76 and the other end fixed to the lock base 72 is provided. The first and second torsion coil springs 73 a and 73 b urge the lock lever 76 so that the engaging claw 76 a of the lock lever 76 is close to the lock holder 71.

  In the lock mechanism 70 configured as described above, when the solenoid 75 is excited, the lock lever 76 swings counterclockwise in FIG. 3, and the engagement claw portion 76 a of the lock lever 76 and the lock groove portion of the lock holder 71. The engagement with 71a is released and an unlocked state is established. When the excitation to the solenoid 75 is stopped, the lock lever 76 swings clockwise by the urging force of the first and second torsion coil springs 73a and 73b, and the engagement claw 76a of the lock lever 76 is locked. The motor shaft 34 </ b> A is locked (connected) to the housing 52 by engaging with the lock groove 71 a of the holder 71, and the motor 34 is prevented from rotating.

  The spiral cable unit 38 is provided with a substantially cylindrical casing 38 a that is held by a vehicle body (not shown), and is provided inside the casing 38 a so as to be rotatable relative to the casing 38 a and is fixed to the housing 52 outside the housing 52. And an inner cylinder 38b. A flexible flat cable 38c is provided between the housing 38a and the inner cylinder 38b. The flexible flat cable 38c is formed by insulating and coating a plurality of lead wires. One end of the flexible flat cable 38c is connected to the inner cylinder 38b. It is wound around the inner cylinder 38b and the other end is connected to the casing 38a. The lead wire connected to the flexible flat cable 38c and extending from the inner cylinder 38b is connected to the stator 34S and the like of the motor 34, and the lead wire connected to the flexible flat cable 38c and extended from the housing 38a is a DC power source. The battery B and the ECU 80 are connected by a connector.

Next, an electrical configuration of the ECU 80 responsible for driving control of the motor 34 will be described with reference to FIG. FIG. 4 is a control block diagram regarding control processing of the motor 34 according to the present embodiment.
As shown in FIG. 4, the ECU 80 mainly includes an MPU 81 that outputs a motor control signal and a drive circuit 91 that supplies drive power to the motor 34 based on the motor control signal. In the present embodiment, the motor 34 that is the drive source of the wave gear mechanism 40 is a brushless motor, and the drive circuit 91 has three phases (U, V, W) applied to the motor 34 based on the input motor control signal. The drive power is supplied. In addition to the steering angle sensor 18 that detects the steering angle θs, the ECU 80 includes a rotation angle sensor 26 that detects the ACT angle θta that is the motor rotation angle of the motor 34 and a vehicle speed sensor 28 that detects the vehicle speed V of the vehicle. Connected (see FIG. 1).

Next, control processing of the motor 34 by the ECU 80 will be described with reference to FIGS. 4 and 5. FIG. 5 is a circuit diagram showing a configuration of the ECU 80 according to the present embodiment.
As shown in FIG. 4, the MPU 81 executes a predetermined program stored in its internal memory, thereby changing the gear ratio variable control calculation unit 82, the differential steer control calculation unit 83, the adder 84, It functions as a motor control means comprising a control calculation unit 85, a correction duty ratio setting unit 86, and a motor control signal output unit 87.

  The gear ratio variable control calculation unit 82 calculates a gear ratio variable ACT command angle θgr *, which is a control target component for changing the gear ratio, on the basis of the input steering angle θs and the vehicle speed V, and supplies it to the adder 84. Output.

  The differential steer control calculation unit 83 is based on the steering speed ωs and the vehicle speed V obtained by differentiating the steering angle θs, and a differential steer command that is a control target component for improving the responsiveness of the vehicle according to the steering speed ωs. The angle θls * is calculated and output to the adder 84.

  The adder 84 is a control target of the ACT angle θta by superimposing the gear ratio variable ACT command angle θgr * from the gear ratio variable control calculation unit 82 and the differential steer command angle θls * from the differential steer control calculation unit 83. The ACT command angle θta * is calculated and output to the position control calculation unit 85.

  The position control calculation unit 85 calculates a current command ε by feedback calculation based on the ACT command angle θta * from the adder 84 and the ACT angle θta from the rotation angle sensor 26, and outputs it to the motor control signal output unit 87.

  The correction duty ratio setting unit 86 sets correction duty ratios D1a to D1c based on detection voltages Vsu to Vsw from voltage sensors 88u to 88w that detect voltages at connection points 93u to 93w, which will be described later, and each correction duty ratio D1a. To D1c are output to the motor control signal output unit 87.

  The motor control signal output unit 87 includes basic duty ratios D0a to D0c set based on the current command ε from the position control calculation unit 85 and the ACT angle θta from the rotation angle sensor 26, and a correction duty ratio setting unit 86. A motor control signal based on each of the correction duty ratios D1a to D1c is generated and output to the drive circuit 91. The motor control signal output unit 87 generates a motor control signal based on an adjustment duty ratio (described later) input from the correction duty ratio setting unit 86 and outputs the motor control signal to the drive circuit 91. The process of setting the correction duty ratios D1a to D1c in the correction duty ratio setting unit 86 and the process of generating and outputting the motor control signal in the motor control signal output unit 87 will be described later with reference to FIGS. This will be described in detail with reference to the flowchart shown.

The drive circuit 91 is configured to control the operation of the wave gear mechanism 40 by supplying drive power based on the motor control signal described above to the motor 34.
As shown in FIG. 5, the drive circuit 91 includes upper FETs 92a to 92c that are switching elements disposed on the power supply line side, and lower FETs 92d to 92f that are switching elements disposed on the ground line side. , FETs 92a and 92d, FETs 92b and 92e, and FETs 92c and 92f are connected in series to form a pair of FETs connected in parallel. The connection point 93u of the FETs 92a and 92d is connected to the motor coil 35u constituting the U phase of the motor 34, and the connection point 93v of the FETs 92b and 92e is connected to the motor coil 35v constituting the V phase. , 92f is connected to a motor coil 35w constituting the W phase. The gate terminals of the FETs 92a to 92f are connected to the MPU 81, and the FETs 92a to 92f are turned on or off according to a motor control signal output from the MPU 81.

  The voltages at the connection points 93u, 93v, and 93w are detected as detection voltages Vsu, Vsv, and Vsw by the voltage sensors 88u, 88v, and 88w, and input to the correction duty ratio setting unit 86 of the MPU 81, respectively.

  In the present embodiment, the ECU 80 causes the solenoid 75 of the lock mechanism 70 to be omitted when the lock mechanism 70 is operated when an ignition switch (IGSW) (not shown) is turned off or when an abnormality of the motor 34 is detected. Excitation current is supplied by the drive circuit. As a result, the motor shaft 34A and the housing 52 are locked (connected).

  Here, the process of setting the correction duty ratios D1a to D1c in the correction duty ratio setting unit 86 and the process of generating and outputting the motor control signal in the motor control signal output unit 87 are shown in FIGS. This will be described in detail with reference to the flowchart shown. FIG. 6 is a flowchart showing the flow of the transmission ratio variable control process by the ECU 80. FIG. 7 is a flowchart showing a subroutine of the correction duty ratio setting process in FIG.

  First, when the IGSW is turned on and the transmission ratio variable device 30 is activated, it is determined Yes in step S101, and the process in the correction duty ratio setting process S200 is performed. As will be described later, immediately after the IGSW is switched from the OFF state to the ON state, the motor shaft 34A and the housing 52 are locked (connected) by the lock mechanism 70, and the correction duty ratio setting process is performed in this locked state. Will be.

First, in step S201 of FIG. 7, an on / off control process based on the adjustment duty ratio D2a _H is performed. Accordingly, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2a _H to the motor control signal output unit 87. The motor control signal output unit 87 turns on the upper FET 92b, turns off the upper FETs 92a and 92c, and the lower FETs 92e and 92f, and controls on and off of the lower FET 92d based on the adjustment duty ratio D2a _H.

  Thereby, a current flows from the battery B toward the upper FET 92b, the connection point 93v, the motor coil 35v, the motor coil 35u, the connection point 93u, and the lower FET 92d. In step S203, the detection voltage Vsv at the connection point 93v and the detection voltage Vsu at the connection point 93u are detected by the voltage sensor 88v and the voltage sensor 88u.

Next, in step S205, an on / off control process based on the adjustment duty ratio D2a _L is performed. Thus, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2a _L to the motor control signal output unit 87. The motor control signal output unit 87 turns on the upper FET 92b, turns off the upper FETs 92a and 92c and the lower FETs 92e and 92f, and controls the lower FET 92d on and off based on the adjustment duty ratio D2a _L. In step S207, the detection voltage Vsv and the detection voltage Vsu are detected in the same manner as in step S203.

Next, in step S209, the correction duty ratio D1a for the lower FET 92d is set. In this process, as described above, the voltage difference between the detection voltage Vsv and the detection voltage Vsu when the lower FET 92d is on / off controlled based on the adjustment duty ratio D2a _H , that is, the output output from the drive circuit 91 to the motor 34. The voltage Vvu _H is calculated. Further, it calculates the output voltage Vvu _L is a voltage difference between the detection voltage Vsv and the detection voltage Vsu when the on-off controlled based on the lower FET92d the adjustment duty ratio D2a _L.

Figure 8 is a bottom FET92d the adjusting duty ratio _D2a H, the adjusting duty ratio _D2a H when the on-off controlled based on D2a _L, D2a _L and the output voltage _Vvu H, a graph showing the relationship between Vvu _L is there.
Next, as shown in FIG. 8, the horizontal axis represents the adjustment duty ratio D2a, the vertical axis represents the output voltage Vvu, and the output voltage Vvu _H corresponding to the adjustment duty ratio D2a _H corresponds to the adjustment duty ratio D2a _L. A straight line L that passes through both the output voltage Vvu _L and the output voltage Vvu _L is created, and the adjustment duty ratio D2a when the output voltage Vvu becomes 0 (zero) in this straight line L, that is, the output voltage Vvu becomes 0 (zero). The maximum adjustment duty ratio D2a is set as the correction duty ratio D1a of the lower FET 92d.

Note that the adjustment duty ratio D2a _H and the adjustment duty ratio D2a _L are set to values such that the output voltage Vvu _H and the output voltage Vvu _L do not become 0 (zero). Further, the upper FET 92c is turned on instead of the upper FET 92b, and the lower FET 92d is turned on / off, so that the upper FET 92c, the connection point 93w, the motor coil 35w, the motor coil 35u, the connection point 93u, and the lower A current flows toward the side FET 92d. At this time, the output voltage Vwu _H which is a voltage difference between the detection voltage Vsw and the detection voltage Vsu when the lower FET 92d is on / off controlled based on the adjustment duty ratio D2a _H , and the adjustment duty ratio D2a _{L of the} lower FET 92d. The correction duty ratio D1a may be set as in step S209 based on the output voltage Vwu _L which is the voltage difference between the detection voltage Vsw and the detection voltage Vsu when the on / off control is performed based on the above.

Next, in step S211, an on / off control process based on the adjustment duty ratio D2b _H is performed. As a result, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2b _H to the motor control signal output unit 87. The motor control signal output unit 87, the upper FET92c ON state, the upper FET 92A, 92b and the lower FET92d, while the off state 92f, on-off controlled based on the lower FET92e the adjustment duty ratio D2b _H.

  Thereby, a current flows from the battery B toward the upper FET 92c, the connection point 93w, the motor coil 35w, the motor coil 35v, the connection point 93v, and the lower FET 92e. In step S213, the detection voltage Vsw at the connection point 93w and the detection voltage Vsv at the connection point 93v are detected by the voltage sensor 88w and the voltage sensor 88v.

Next, in step S215, the on-off control process is performed based on the adjustment duty ratio D2b _L. Accordingly, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2b _L to the motor control signal output unit 87. The motor control signal output unit 87, the upper FET92c ON state, the upper FET 92A, 92b and the lower FET92d, while the off state 92f, on-off controlled based on the lower FET92e the adjustment duty ratio D2b _L. In step S217, the detection voltage Vsw and the detection voltage Vsv are detected in the same manner as in step S213.

Next, in step S219, the correction duty ratio D1b for the lower FET 92e is set. In this process, as in step S209, the output voltage Vwv _H , which is the voltage difference between the detection voltage Vsw and the detection voltage Vsv when the lower FET 92e is on / off controlled based on the adjustment duty ratios D2b _H and D2b _L , Vwv _L is calculated. Then, adjustment when the output voltage Vwv in straight line passing through both the output voltage Vwv _L corresponding to the output voltage Vwv _H and the adjustment duty ratio D2b _L corresponding to the adjustment duty ratio D2b _H becomes 0 (zero) The duty ratio D2b is set as the correction duty ratio D1b of the lower FET 92e.

Incidentally, adjusting the duty ratio D2b _H and adjusting the duty ratio D2b _L is set to such a value as will not cause the output voltage Vwv _H and the output voltage Vwv _L is 0 (zero). Further, the upper FET 92a is turned on instead of the upper FET 92c, and the lower FET 92e is turned on / off, whereby the upper FET 92a, the connection point 93u, the motor coil 35u, the motor coil 35v, the connection point 93v, and the lower A current flows toward the side FET 92e. At this time, the output voltage Vuv _H which is a voltage difference between the detection voltage Vsu and the detection voltage Vsv when the lower FET 92e is on / off controlled based on the adjustment duty ratio D2b _H , and the adjustment duty ratio D2b _{L of the} lower FET 92e. The correction duty ratio D1b may be set as in step S209 based on the output voltage Vuv _L which is the voltage difference between the detection voltage Vsu and the detection voltage Vsv when the on / off control is performed based on.

Next, in step S221, on-off control process is performed based on the adjustment duty ratio D2c _H. Thereby, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2c _H to the motor control signal output unit 87. The motor control signal output unit 87, the upper FET92a on state, upper FET92b, 92c and lower FET92d, while turns off the 92e, on-off controlled based on the lower FET92f the adjustment duty ratio D2c _H.

  Thereby, a current flows from the battery B toward the upper FET 92a, the connection point 93u, the motor coil 35u, the motor coil 35w, the connection point 93w, and the lower FET 92f. In step S223, the detection voltage Vsu at the connection point 93u and the detection voltage Vsw at the connection point 93w are detected by the voltage sensor 88u and the voltage sensor 88w.

Next, in step S225, on-off control process is performed based on the adjustment duty ratio D2c _L. Thus, the correction duty ratio setting unit 86 outputs the adjustment duty ratio D2c _L on the motor control signal output unit 87. The motor control signal output unit 87, the upper FET92a on state, upper FET92b, 92c and lower FET92d, while turns off the 92e, on-off controlled based on the lower FET92f the adjustment duty ratio D2c _L. In step S227, the detection voltage Vsu and the detection voltage Vsw are detected in the same manner as in step S223.

Next, in step S229, the correction duty ratio D1c for the lower FET 92f is set. In this process, as in step S209, the output voltage Vuw _H , which is the voltage difference between the detection voltage Vsu and the detection voltage Vsw when the lower FET 92f is on / off controlled based on the adjustment duty ratios D2c _H and D2c _L , Vuw _L is calculated. Then, adjustment when the output voltage Vuw in straight line passing through both the output voltage Vuw _L corresponding to the output voltage Vuw _H and the adjustment duty ratio D2c _L corresponding to the adjustment duty ratio D2c _H becomes 0 (zero) The duty ratio D2c is set as the correction duty ratio D1c of the lower FET 92f.

Incidentally, adjusting the duty ratio D2c _H and adjusting the duty ratio D2c _L is set to such a value as will not cause the output voltage Vuw _H and the output voltage Vuw _L is 0 (zero). Further, the upper FET 92b is turned on instead of the upper FET 92a, and the lower FET 92f is turned on / off, so that the upper FET 92b, the connection point 93v, the motor coil 35v, the motor coil 35w, the connection point 93w, and the lower A current flows toward the side FET 92f. At this time, the output voltage Vvw _H which is a voltage difference between the detection voltage Vsw and the detection voltage Vsw when the lower FET 92f is on / off controlled based on the adjustment duty ratio D2c _H , and the adjustment duty ratio D2c _{L of the} lower FET 92f. The correction duty ratio D1c may be set as in step S209 based on the output voltage Vvw _L which is the voltage difference between the detection voltage Vsv and the detection voltage Vsw when the on / off control is performed based on the above.

  When the correction duty ratios D1a to D1c are thus set for the lower FETs 92d to 92f and the correction duty ratio setting process S200 is completed, the unlocking process is performed in step S103 of FIG. 6, and the lock mechanism 70 is unlocked. It becomes.

  In step S105, a transmission ratio variable control process is performed. In this process, the correction duty ratios D1a to D1c set in the correction duty ratio setting process S200 are input to the motor control signal output unit 87. The motor control signal output unit 87 generates a correction duty ratio D1a to a basic duty ratio D0a to D0c set for each of the FETs 92d to 92f based on the current command ε from the position control calculation unit 85 and the ACT angle θta from the rotation angle sensor 26. Drive duty ratios Da to Dc obtained by adding to D1c are set for the lower FETs 92d to 92f. A motor control signal based on each of these drive duty ratios Da to Dc is output to the drive circuit 91.

  Any one of the lower FETs 92d to 92f is ON / OFF controlled according to the corresponding drive duty ratio Da to Dc, and any one of the upper FETs 92a to 92c not connected in series to the lower FET is ON controlled. Accordingly, the motor 34 is driven to change the transmission ratio between the first steering shaft 14 and the second steering shaft 16.

  As described above, the correction duty ratios D1a to D1c, which are the maximum adjustment duty ratios D2a to D2c at which the output voltage becomes 0 (zero), are set for each of the lower FETs 92d to 92f. Since the drive circuit 91 is controlled based on the drive duty ratios Da to Dc added to the duty ratios D0a to D0c, the dead zone where the output voltage output from the drive circuit 91 becomes 0 (zero) is suppressed.

  When the IGSW is turned off (Yes in S107), a lock process is performed in Step S109, and the lock mechanism 70 locks (connects) the motor shaft 34A to the housing 52 to prevent rotation of the motor 34. It becomes.

As described above, in the transmission ratio variable device 30 according to the present embodiment, the MPU 81 is connected in series to the upper FET 92b in the on state in the locked state in which the rotation drive of the motor 34 is blocked by the lock mechanism 70. Output voltage which is the voltage difference between the detection voltage Vsv and the detection voltage Vsu detected by the voltage sensor 88v and the voltage sensor 88u by adjusting the adjustment duty ratio in the ON / OFF control of the lower FET 92d not to be D2a _H or D2a _L Vvu _H and output voltage Vvu _L are obtained. Then, adjustment when the output voltage Vvu in the straight line L passing through both the output voltage Vvu _L corresponding to the output voltage Vvu _H and the adjustment duty ratio D2a _L corresponding to the adjustment duty ratio D2a _H becomes 0 (zero) The duty ratio D2a is set to the correction duty ratio D1a of the lower FET 92d. Similarly, the correction duty ratio D1b of the lower FET 92e and the correction duty ratio D1c of the lower FET 92f are set. Then, the MPU 81 turns on one of the upper FETs 92a to 92c based on the steering situation, and sets one of the lower FETs 92d to 92f not connected in series to the upper FET in accordance with the steering situation. On / off control is performed based on the driving duty ratios Da to Dc set by adding the correction duty ratios D1a to D1c of the lower FET to the basic duty ratios D0a to D0c of the lower FET set.

Based on the correction duty ratios D1a to D1c and the basic duty ratios D0a to D0c set in this way, one of the lower FETs 92d to 92f is on / off controlled and the upper FET 92a not connected in series to the lower FET By turning on one of -92c, the dead zone in which the output voltage output from the drive circuit 91 becomes 0 (zero) is suppressed, so that there is no response delay when changing the transmission ratio during steering. Can do.
Therefore, the steering feeling can be improved.

In addition, this invention is not limited to the said embodiment, You may actualize as follows, and even in that case, an effect | action and effect equivalent to the said embodiment are acquired.
(1) In the correction duty ratio setting process S200 of FIG. 7, a straight line L that passes through both output voltages (for example, Vvu _H and Vvu _L ) respectively corresponding to two adjustment duty ratios (for example, D2a _H and D2a _L ). The adjustment duty ratio when the output voltage becomes 0 (zero) is not limited to being set as the correction duty ratios D1a to D1c, but the correction duty ratios D1a to D1c may be set as follows.

  That is, the adjustment duty ratios D2a to D2c in the on / off control of the lower FETs 92d to 92f are sequentially changed to search for the adjustment duty ratio at which the output voltage becomes 0 (zero). The correction duty ratios D1a to D1c may be set respectively.

  Further, as illustrated in FIG. 9, for adjustment when the output voltage becomes 0 (zero) when the adjustment duty ratios D2a to D2c in the on / off control of the lower FETs 92d to 92f are adjusted to approach zero. The duty ratio may be set as the correction duty ratios D1a to D1c. FIG. 9 shows a modification in which the correction duty ratio D1a in the lower FET 92d is set. Based on the adjustment duty ratio D2a that is adjusted by gradually decreasing the lower FET 92d so as to approach 0 (zero). It is a graph which shows the modification of the relationship between the duty ratio D2a for adjustment and output voltage Vvu when on / off control is carried out.

(2) In the correction duty ratio setting process S200 of FIG. 7, straight lines passing through two points of output voltages (for example, Vvu _H and Vvu _L ) respectively corresponding to two adjustment duty ratios (for example, D2a _H and D2a _L ) The adjustment duty ratio when the output voltage becomes 0 (zero) at L is not limited to the correction duty ratios D1a to D1c, and it corresponds to three or more adjustment duty ratios and these adjustment duty ratios. The adjustment duty ratio when the output voltage becomes 0 (zero) in an approximate straight line (including a straight line) passing through each point of the output voltage to be set may be set as the correction duty ratios D1a to D1c.

  By using such an approximate straight line, the correction duty ratio can be calculated by a simple calculation compared to the case of searching for the adjustment duty ratio at which the output voltage becomes 0 (zero) by sequentially changing the adjustment duty ratio. Can be set. Further, when the number of adjustment duty ratios for detecting the output voltage is increased, the accuracy of the correction duty ratios D1a to D1c can be improved.

(3) In step S101 in FIG. 6, the correction duty ratio setting process S200 is not limited to the execution when the IGSW is changed from the OFF state to the ON state and the transmission ratio variable device 30 is activated. The correction duty ratio setting process S200 may be performed when the state is changed to the unlocked state.

It is explanatory drawing which shows the structure outline | summary of the vehicle control apparatus to which the transmission ratio variable apparatus which concerns on this embodiment is applied. FIG. 2 is a detailed sectional view of the transmission ratio variable device of FIG. 1. It is sectional drawing by the cut surface equivalent to the 3-3 line shown in FIG. It is a control block diagram regarding the control process of the motor which concerns on this embodiment. It is a circuit diagram which shows the structure of ECU which concerns on this embodiment. It is a flowchart which shows the flow of the transmission ratio variable control process by ECU. It is a flowchart which shows the subroutine of the correction | amendment duty ratio setting process in FIG. It is a graph which shows the relationship between the said duty ratio for adjustment, and output voltage when carrying out on-off control of lower FET based on the duty ratio for adjustment. It is a graph which shows the modification of the relationship between the said duty ratio for adjustment and output voltage when carrying out on-off control of lower FET based on the duty ratio for adjustment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vehicle control apparatus 30 ... Transmission ratio variable apparatus 34 ... Motor 40 ... Wave gear mechanism (transmission ratio variable mechanism)
70: Lock mechanism (locking means)
80 ... ECU
81 ... MPU (motor control means, correction duty ratio setting means)
88u to 88w ... Voltage sensor (voltage detection means)
91: Driving circuit 92a to 92c: Upper FET (first switching element)
92d to 92f ... lower FET (second switching element)
Da to Dc: Driving duty ratio (predetermined duty ratio)
D0a～D0c ... basic duty ratio D1a to D1c ... correction duty ratio _{D2a H, D2a L, D2b H} , D2b L, D2c H, D2c L ... adjusting the duty ratio Vsu～Vsw ... detection voltage _{Vvu H,} Vvu L, Vwv _H , Vwv _L , Vuw _H , Vuw _L ... Output voltage

Claims (3)

Provided in the middle of the steering system of the vehicle connecting the steering wheel and the steering wheel,
A transmission ratio variable mechanism capable of changing a transmission ratio between the input shaft on the steering wheel side and the output shaft on the steering wheel side by rotating the motor;
Lock means capable of preventing rotation of the motor and connecting the input shaft and the output shaft;
A plurality of a pair of switching elements in which a first switching element arranged on the power supply line side and a second switching element arranged on the ground line side are connected in series are provided. A drive circuit for controlling the supplied power and outputting the same to the motor;
Based on a steering situation, one of the first switching elements is turned on, and one of the second switching elements not connected in series to the first switching element is based on a predetermined duty ratio. Motor control means for on / off control;
The output voltage output from the drive circuit is detected from the voltage between the anti-power supply line side of the first switching element in the on state and the anti-ground line side of the second switching element that is on / off controlled. Voltage detecting means for
A transmission ratio variable device comprising:
The duty ratio in the on / off control of the second switching element that is not connected in series to the first switching element that is in the on state is adjusted in a state in which the rotation driving of the motor is blocked by the locking means. Correction duty ratio setting means for setting the maximum duty ratio when the output voltage detected by the voltage detection means is 0 (zero) as the correction duty ratio for each of the second switching elements. And
The transmission ratio variable device, wherein the predetermined duty ratio is set by adding the correction duty ratio to a basic duty ratio set according to the steering situation.   The correction duty ratio setting means controls the on / off of the second switching element based on at least two duty ratios and these duty ratios in a state where the rotation of the motor is blocked by the lock means. The duty ratio when the output voltage becomes 0 (zero) in the approximate straight line obtained from at least two output voltages greater than 0 (zero) detected by the voltage detection means is the correction duty ratio as the correction duty ratio. The transmission ratio variable device according to claim 1, wherein each of the two switching elements is set.   The correction duty ratio setting means is detected by the voltage detection means when the duty ratio in the on / off control is adjusted to be close to 0 (zero) in a state where rotation of the motor is blocked by the lock means. 2. The variable transmission ratio device according to claim 1, wherein a duty ratio when the output voltage is 0 (zero) is set for each of the second switching elements as the correction duty ratio.

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