JP2012040932A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device for a vehicle which requires neither a torque sensor used for measuring a steering reaction force generated by the operation of a transmission ratio variable mechanism nor a torsion bar.SOLUTION: A target act angle calculation part 51 calculates a target act angle θact*, which is a target value of an act angle θact. A control signal output part 52 controls a drive circuit 29 of a motor 20 for changing transmission ratio on the basis of the target act angle θact* calculated by the target act angle calculation part 51. A target reaction force compensation angle calculation part 61 calculates a target reaction force compensation angle θrec*, which is a target rotation angle of a motor 25 for reaction force compensation, based on the target act angle θact* when the target act angle θact* calculated by the target act angle calculation part 51 is not zero. A control signal output part 62 controls the motor 25 for reaction force compensation on the basis of the target reaction force compensation angle θrec* calculated by the target reaction force compensation angle calculation part 61.

Description

  The present invention relates to a vehicle steering apparatus.

  In the following Patent Documents 1 and 2, the transmission ratio variable mechanism that changes the ratio of the turning angle of the steered wheel to the steering angle of the steering member, and the steering reaction force of the steering member in relation to the operation of the transmission ratio variable mechanism are compensated. A vehicle steering apparatus including a reaction force compensating motor for the purpose is disclosed. The transmission ratio variable mechanism includes a planetary gear mechanism that differentially couples a first shaft coupled to the steering member and a second shaft coupled to the steering mechanism, a transmission ratio changing motor that drives the planetary gear mechanism, and including. The transmission ratio variable mechanism adds the rotation angle (act angle) of the second shaft based on the motor drive to the rotation angle of the second shaft based on the operation of the steering member, so that the rotation angle of the first shaft (to the steering angle) is increased. The ratio of the rotation angle of the second shaft (corresponding to the steered angle) to the equivalent) is varied.

  The reaction force compensating motor is controlled based on, for example, a steering torque applied to the first shaft detected by a steering torque sensor. Specifically, when the transmission ratio changing motor is driven, the steering reaction force generated by the operation of the transmission ratio variable mechanism is measured by the steering torque sensor, and the reaction force compensation is based on the measured steering reaction force. The motor is controlled. The first shaft includes two shafts connected by a torsion bar (twisting element). The steering torque sensor detects the steering torque by detecting a relative displacement in the rotational direction between the two shafts due to torsion of the torsion bar.

JP 2009-101800 JP JP 2005-343205 A JP 2006-341814 A JP 2009-101885 JP 2005-297715 A JP 2007-76618 EP1870313B1 publication

In the conventional vehicle steering apparatus described above, when the transmission ratio changing motor is driven, the reaction force compensating motor is controlled based on the steering reaction force measured by the steering torque sensor. For this reason, since it is necessary to provide a torsion bar in the shaft connected with a steering member, there exists a problem that the rigidity of the shaft falls.
An object of the present invention is to provide a vehicle steering apparatus in which a torque sensor used for measuring a steering reaction force generated by the operation of a transmission ratio variable mechanism is unnecessary and a torsion bar is unnecessary.

In order to achieve the above object, the invention according to claim 1 includes a first shaft (11) coupled to the steering member (2) and a second shaft (12) coupled to the steering mechanism (10). A variable transmission ratio mechanism (6) for changing the transmission ratio of rotation between the first motor (20) for changing the transmission ratio of the variable transmission ratio mechanism, and when the first motor is rotating A second motor (25) for increasing / decreasing a steering reaction force applied to the steering member, and a first target rotation angle calculating means for calculating a first target rotation angle (θact ^* ) that is a target rotation angle of the first motor. 51), first control means (52) for controlling the first motor based on the first target rotation angle calculated by the first target rotation angle calculation means, and when the first motor is rotated. In addition, based on the first target rotation angle, the target rotation angle of the second motor There second target rotation angle second target rotation angle calculating means for calculating a (θrec ^{*) (61),} based on the second target rotation angle computed by the second target rotation angle calculation means, said second motor And a second control means (62) for controlling the steering mechanism, and the vehicle steering apparatus does not include a twisting element for detecting a steering torque between the steering member and the transmission ratio variable mechanism. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  If the transmission ratio of rotation between the first shaft and the second shaft is changed by rotating the first motor, the driver may feel uncomfortable. In the present invention, when the first motor is rotated, the second target rotation angle that is the target rotation angle of the second motor is calculated based on the first target rotation angle that is the target rotation angle of the first motor. Then, the second motor is controlled based on the obtained second target rotation angle. Accordingly, the second motor can be controlled according to the steering reaction force applied to the steering member by the rotation of the first motor without using the steering torque sensor. For this reason, when the 1st motor is rotating, the discomfort given to a driver | operator can be reduced. Further, since it is not necessary to detect the steering torque in order to calculate the second target rotation angle, it is not necessary to provide a torsion bar on the first shaft. For this reason, the rigidity of the first shaft can be increased.

The invention according to claim 2 is the vehicle according to claim 1, wherein the second target rotation angle calculation means calculates a second target rotation angle by multiplying the first target rotation angle by a predetermined constant. This is a steering device for use. In this configuration, the second target rotation angle is calculated by multiplying the first target rotation angle by a predetermined constant.
The invention according to claim 3 is the vehicle steering apparatus according to claim 2, wherein the sign of the predetermined constant is negative. In this configuration, the second motor is rotated in a direction that cancels the steering reaction force applied to the steering member by the rotation of the first motor. Thereby, when the 1st motor is rotating, the discomfort given to a driver | operator can be reduced.

  According to a fourth aspect of the present invention, the second target rotation angle is obtained based on a map that stores a second target rotation angle with respect to a first target rotation angle that is created in advance. The vehicle steering device according to the item. In this configuration, the second target rotation angle is obtained based on a map that stores the second target rotation angle with respect to the first target rotation angle.

It is a mimetic diagram showing a schematic structure of a steering device for vehicles concerning one embodiment of this invention. It is a block diagram which shows schematic structure of a control part. It is a flowchart which shows operation | movement of a 1st control part and a 2nd control part. It is a graph which shows the change of a target act angle and a target reaction force compensation angle. It is a schematic diagram for demonstrating the example of active control. It is a graph for demonstrating the specific example of the relationship of target reaction force compensation angle (theta) rec ^{* with} respect to target act angle (theta ⁾ act ^* memorize | stored as a map.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus according to an embodiment of the present invention.
The vehicle steering apparatus 1 includes a steering member 2 such as a steering wheel, and a steering shaft 3 connected to the steering member 2. The steering shaft 3 includes a first shaft 11 and a second shaft 12 arranged coaxially with the first shaft 11. A steering member 2 is connected to one end of the first shaft 11 so as to be able to rotate together. The other end of the first shaft 11 and one end of the second shaft 12 are connected via a transmission ratio variable mechanism 6 so as to be differentially rotatable. The other end of the second shaft 12 is connected to the steered wheels 4L and 4R via the universal joint 7, the intermediate shaft 8, the universal joint 9, and the steering mechanism 10.

The steering mechanism 10 includes a pinion shaft 15 that is connected to the universal joint 9, a rack 16 a that meshes with the pinion 15 a at the tip of the pinion shaft 15, a rack shaft 16 that serves as a steering shaft extending in the left-right direction of the vehicle, and a rack shaft 16. Knuckle arms 18L and 18R connected to each of the pair of end portions via tie rods 17L and 17R.
With the above configuration, the rotation of the steering member 2 is transmitted to the steering mechanism 10 via the steering shaft 3 and the like. In the steering mechanism 10, the rotation of the pinion 15a is converted into the movement of the rack shaft 16 in the axial direction, and the corresponding knuckle arms 18L and 18R rotate through the tie rods 17L and 17R, respectively. Accordingly, the corresponding steered wheels 4L and 4R connected to the knuckle arms 18L and 18R are respectively steered.

  The transmission ratio variable mechanism 6 changes the ratio (transmission ratio θt / θs) of the rotation angle of the second shaft 12 (corresponding to the turning angle θt) to the rotation angle of the first shaft 11 (corresponding to the steering angle θs). Is to do. The transmission ratio variable mechanism 6 includes a planetary gear mechanism 19 serving as a differential mechanism that connects the first shaft 11 and the second shaft 12 so as to be differentially rotatable, and a transmission ratio changing motor (first gear) that drives the planetary gear mechanism 19. Motor) 20.

  The planetary gear mechanism 19 is disposed opposite to the first sun gear 21, which is connected to the first shaft 11 so as to be able to rotate along with the first shaft 11, and is connected to the second shaft 12 so as to be able to rotate together. Second sun gear 22, planetary gear 23 meshing with both first and second sun gears 21, 22, planetary gear 23 can rotate about its axis, and about the axis of first and second sun gears 21, 22 And a carrier 24 for revolvingly holding.

The first and second sun gears 21 and 22 and the planetary gear 23 are formed using, for example, a torsion gear, and the planetary gear 23 meshes with the sun gears 21 and 22. Instead of the helical gear, other parallel shaft gears such as a helical gear and a spur gear may be used.
The planetary gear 23 is for associating the first and second sun gears 21 and 22 with each other, and a plurality (two in the present embodiment) are arranged at equal intervals in the circumferential direction of the steering shaft 3. The axis of each planetary gear 23 extends in parallel with the axis A of the steering shaft 3. The carrier 24 can rotate around the axis A of the steering shaft 3.

  The transmission ratio changing motor 20 is for driving the carrier 24 to rotate, and changes the transmission ratio θt / θs by changing the rotation speed of the carrier 24 about the axis A. The transmission ratio changing motor 20 is composed of, for example, a brushless motor, and is arranged coaxially with the steering shaft 3. The transmission ratio changing motor 20 includes a rotor 201 that is coupled to the carrier 24 so as to be able to rotate along with the carrier 24, and a stator 202 that surrounds the rotor 201 and is fixed to the housing 26. In the vicinity of the transmission ratio changing motor 20, a rotation angle sensor 35 made of, for example, a resolver for detecting the rotation angle of the transmission ratio changing motor 20 is disposed.

  The vehicle steering apparatus 1 includes a reaction force compensating motor (second motor) 25 for increasing or decreasing a steering reaction force applied to the steering member 2 when the transmission ratio changing motor 20 is rotating. The reaction force compensating motor 25 is composed of, for example, a brushless motor, and is arranged coaxially with the steering shaft 3. The reaction force compensating motor 25 includes a rotor 251 that is coupled to the first shaft 11 so as to be able to rotate along with the first shaft 11, and a stator 252 that surrounds the rotor 251 and is fixed to the housing 26. In the vicinity of the reaction force compensation motor 25, a rotation angle sensor 36 made of, for example, a resolver for detecting the rotation angle of the reaction force compensation motor 25 is disposed.

  In this embodiment, when the first shaft 11 is rotated by the operation of the steering member 2, the second shaft 12 and the first shaft 11 are passed through the first sun gear 21, the planetary gear 23, and the second sun gear 22. Rotates at speed. When the transmission ratio changing motor 20 is driven, the carrier 24 rotates, and the second shaft 12 rotates at a higher speed through the planetary gear 23 and the second sun gear 22. That is, when the transmission ratio changing motor 20 is driven to rotate (when active control is performed), the rotation angle of the second shaft 12 based on the operation of the steering member 2 (in this embodiment, equal to the steering angle θs). ) Is added with the rotation angle of the second shaft 12 based on the motor drive (hereinafter referred to as “act angle θact”), so that the rotation angle of the second shaft 12 with respect to the steering angle θs that is the rotation angle of the first shaft 11 is increased. The ratio θr / θs of (θr = θs + θact) is varied. Note that “addition” includes not only addition but also subtraction.

  Driving of the transmission ratio changing motor 20 and the reaction force compensating motor 25 is controlled by the control unit 28. The control unit 28 is connected to the transmission ratio changing motor 20 via the drive circuit 29, and is connected to the reaction force compensating motor 25 via the drive circuit 30. A steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, a yaw rate sensor 34, and rotation angle sensors 35 and 36 are connected to the control unit 28, respectively.

  The steering angle sensor 31 detects a steering angle θs (rotation angle of the first shaft 11) that is an operation amount from the straight traveling position of the steering member 2. The turning angle sensor 32 detects the turning angle θt (the rotation angle of the second shaft 12). The vehicle speed sensor 33 detects the vehicle speed V. The yaw rate sensor 34 detects the yaw rate Ry of the vehicle. The control unit 28 controls driving of the transmission ratio changing motor 20 and the reaction force compensating motor 25 based on the signals of the sensors 31 to 36 and the like.

FIG. 2 is a block diagram illustrating a schematic configuration of the control unit 28.
The control unit 28 includes a first control unit 50 for controlling the transmission ratio changing motor 20 and a second control unit 60 for controlling the reaction force compensating motor 25. Each control unit 50, 60 is constituted by a microcomputer including a CPU and a memory storing an operation program of the CPU.

The first control unit 50 functions as a plurality of function processing units by executing a predetermined operation program stored in the memory. The plurality of function processing units include a target act angle calculation unit 51 and a control signal output unit 52. The target act angle calculation unit 51 is detected by the steering angle θs detected by the steering angle sensor 31, the turning angle θt detected by the turning angle sensor 32, the vehicle speed V detected by the vehicle speed sensor 33, and the yaw rate sensor 34. The target act angle θact ^* is calculated based on the vehicle state quantity such as the yaw rate Ry. The target act angle calculation unit 51 may calculate the target act angle θact ^* by a method similar to the calculation method described in Patent Document 3, for example.

The target act angle calculation unit 51, like the IFS control calculation unit described in Patent Document 3, for example, is a so-called active steer function, that is, an act angle θact for controlling the yaw moment of the vehicle based on the vehicle model. A target act angle θact ^* which is a target value may be calculated. In this case, the target act angle calculation unit 51 calculates the target act angle θact ^* for realizing the active steering function. Specifically, for example, when the steer characteristic is understeer, the target act angle calculation unit 51 calculates a target act angle θact ^* so that the turning angle of the steered wheels 17L and 17R becomes small. On the other hand, when the steer characteristic is oversteer, the target act angle calculation unit 51 provides the target act angle θact ^* for giving the steered wheels 4L and 4R a steer angle (counter steer) opposite to the yaw moment direction ^. Is calculated.

  Understeering refers to a case where the actual vehicle turning angle is smaller than the vehicle turning angle assumed by the driver. Further, oversteer refers to a case where the actual vehicle turning angle is smaller than the vehicle turning angle assumed by the driver. The case where the vehicle turning angle assumed by the driver is the same as the actual vehicle turning angle is called neutral steer. The vehicle turning angle assumed by the driver can be replaced with a theoretical value in the vehicle model.

The control signal output unit 52 outputs an actual act angle (actual) obtained from the target act angle θact ^* calculated by the target act angle calculation unit 51 and the rotation angle of the transmission ratio changing motor 20 detected by the rotation angle sensor 35. current command value is generated so that the actual act angle θact follows the target act angle θact ^* based on (act angle θact). Then, the control signal output unit 52 gives a control signal corresponding to the current command value to the drive circuit 29. Drive power corresponding to the control signal is supplied from the drive circuit 29 to the transmission ratio changing motor 20. As a result, the transmission ratio changing motor 20 is driven.

The second control unit 60 functions as a plurality of function processing units by executing a predetermined operation program stored in the memory. The plurality of function processing units include a target reaction force compensation angle calculation unit 61 and a control signal output unit 62. The target reaction force compensation angle calculation unit 61 is given the target act angle θact ^* calculated by the target act angle calculation unit 51 in the first control unit 50. When the target act angle θact ^* given from the first control unit 50 is not zero, that is, when active control is being performed, the target reaction force compensation angle calculation unit 61 is based on the following equation (1). Then, the target reaction force compensation angle θrec ^* which is the target rotation angle of the reaction force compensation motor 25 is calculated.

θrec ^* = k × θact ^* (1)
k is a constant, and in this embodiment, its sign is negative. For example, k may be a value within a range of −1 ≦ k ≦ −0.1. More specifically, k may be a value such as -1, -0.9, -0.8, and the like.
The control signal output unit 62 is based on the target reaction force compensation angle θrec ^* calculated by the target reaction force compensation angle calculation unit 61 and the rotation angle of the reaction force compensation motor 25 detected by the rotation angle sensor 36. The current command value is generated so that the actual rotation angle (actual rotation angle) of the reaction force compensation motor 25 follows the target reaction force compensation angle θrec ^* . Then, the control signal output unit 62 gives a control signal corresponding to the current command value to the drive circuit 30. Drive power corresponding to the control signal is supplied from the drive circuit 30 to the reaction force compensating motor 25. As a result, the reaction force compensating motor 25 is driven.

FIG. 3 is a flowchart showing operations of the first control unit 50 and the second control unit 60.
The 1st control part 50 performs processing of Steps S1-S3 shown in Drawing 3 for every predetermined calculation cycle. The target act angle calculator 51 in the first controller 50 calculates a target act angle θact ^* for realizing the active steering function (step S1). The target act angle calculation unit 51 gives the obtained target act angle θact ^* to the control signal output unit 52 in the first control unit 50, and the obtained target act angle θact ^* in the second control unit 60. This is transmitted to the reaction force compensation angle calculation unit 61 (step S2). The control signal output unit 52 drives the drive circuit 29 so that the actual act angle θact calculated based on the output signal of the rotation angle sensor 35 follows the target act angle θact ^* given from the target act angle calculation unit 51. Is controlled (step S3).

The target reaction force compensation angle calculation unit 61 in the second control unit 60 monitors whether or not the target act angle θact ^* transmitted from the first control unit 50 is zero (step S11). That is, it is determined whether or not active control is being performed. When the target act angle θact ^* transmitted from the first control unit 50 is zero, that is, when the active control is not performed (step S11: YES), the process returns to step S11. When the target act angle θact ^* transmitted from the first control unit 50 is not zero, that is, when active control is performed (step S11: NO), the target reaction force compensation angle calculation unit 61 performs the target reaction angle calculation unit 61. Based on the act angle θact ^* and the above equation (1), the target reaction force compensation angle θrec ^* is calculated (step S12). Thereafter, the control signal output unit 62 in the second control unit 60 determines that the actual rotation angle of the reaction force compensation motor 25 calculated based on the output signal of the rotation angle sensor 36 is the target reaction force compensation angle calculation unit. The drive circuit 30 is controlled so as to follow the target reaction force compensation angle θrec ^* calculated by 61 (step S13).

FIG. 4 is a graph showing changes in the target act angle θact ^* and the target reaction force compensation angle θrec ^* . In FIG. 4, a broken curve indicates a change in the target act angle θact ^* , and a solid curve indicates a change in the target reaction force compensation angle θrec ^* .
During active control, the target reaction force compensation angle θrec ^* is a rotation angle having a sign opposite to the target act angle θact ^* . Therefore, during active control, the reaction force compensating motor 25 is rotated in the direction opposite to the rotation direction of the transmission ratio changing motor 20. As a result, the reaction force compensating motor 25 rotates in a direction to cancel the steering reaction force generated by the rotation of the transmission ratio changing motor 20. As a result, the uncomfortable feeling given to the driver during the active control can be reduced. In addition, a steering torque sensor conventionally used for measuring the steering reaction force during active control is not required. For this reason, since it is not necessary to provide the torsion bar in the 1st shaft 11, the rigidity of the 1st shaft 11 can be improved.

FIG. 5 is a schematic diagram for explaining an example of active control. When the vehicle 71 is traveling along the traveling direction intended by the driver (θact ^* = 0), the direction of the vehicle 71 is, for example, relative to the original traveling direction due to the obstacle (or μ split) 72. And change to the left. Then, the transmission ratio changing motor 20 is driven by the above-described active steering function, and the direction of the vehicle 71 is changed to the right (θact ^* = x (x ≠ 0)). At this time, the reaction force compensating motor 25 is driven so as to cancel the steering reaction force transmitted from the second shaft 12 side to the transmission ratio variable mechanism 6. Thereby, the uncomfortable feeling given to a driver at the time of active control is reduced. When the vehicle 71 is returned to the correct track, the active control is stopped (θact ^* = 0).

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the target reaction-force compensation angle calculation unit 61, based on the target act angle Shitaact ^* and a constant k (based on the equation (1)), calculating a target reaction force compensating angle Shitarec ^* is doing. However, the target reaction force compensation angle calculation unit 61 calculates the target reaction force compensation angle based on the value obtained by converting the target act angle θact ^* into the rotation angle of the first shaft 11 using the transmission ratio θt / θs and the constant k. θrec ^* may be calculated. Specifically, a value obtained by converting the target act angle θact ^* into the rotation angle of the first shaft 11 is θact ^* × θs / θt. Therefore, the target reaction force compensation angle calculation unit 61 may calculate the target reaction force compensation angle θrec ^* based on the following equation (2).

θrec ^* = k × θact ^* × θs / θt (2)
k is a constant and its sign is negative. For example, k may be a value in a range of −1 ≦ k ≦ −0.1. More specifically, k may be a value such as -1, -0.9, -0.8, and the like.
The target reaction-force compensation angle calculation unit 61, based on a map that stores the target reaction force compensating angle Shitarec * for pre-made target act angle Shitaact ^*, may be obtained the target reaction-force compensation angle θrec ^*. The relationship of the target reaction force compensation angle θrec * with respect to the target act angle θact ^* stored as a map may be, for example, a relationship as shown by a straight line a or curves b to d in FIG. In all of the straight lines a or curves b to d shown in FIG. 6, the target reaction force compensation angle θrec * increases in the negative direction as the target act angle θact ^* increases in the positive direction. However, the line a shows an example where the target act angle Shitaact ^* with respect to the target reaction-force compensating angle Shitarec * varies linearly, curve b~d the target reaction force with respect to the target act angle Shitaact ^* respectively An example in which the compensation angle θrec * changes nonlinearly is shown.

When a map of the target reaction force compensation angle θrec * with respect to the target act angle θact ^* is created in consideration of a time constant related to steering torque transmission when it is assumed that a torsion bar (torsion element) is provided on the first shaft 11 When the steering reaction force is compensated by the reaction force compensating motor 25, it is possible to give the driver the same feeling as when the first shaft 11 is provided with the torsion bar.
In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 2 ... Steering member, 6 ... Transmission ratio variable mechanism, 10 ... Steering mechanism, 11 ... 1st shaft, 12 ... 2nd shaft, 20 ... Transmission ratio change motor, 25 ... Reaction force compensation motor

Claims (4)

A transmission ratio variable mechanism for changing a transmission ratio of rotation between the first shaft coupled to the steering member and the second shaft coupled to the steering mechanism;
A first motor for changing a transmission ratio of the transmission ratio variable mechanism;
A second motor that increases or decreases a steering reaction force applied to the steering member when the first motor is rotated;
First target rotation angle calculating means for calculating a first target rotation angle that is a target rotation angle of the first motor;
First control means for controlling the first motor based on the first target rotation angle calculated by the first target rotation angle calculation means;
Second target rotation angle calculation means for calculating a second target rotation angle that is a target rotation angle of the second motor based on the first target rotation angle when the first motor is rotated;
Second control means for controlling the second motor based on the second target rotation angle calculated by the second target rotation angle calculation means;
A vehicle steering apparatus that does not include a torsion element for detecting a steering torque between the steering member and the transmission ratio variable mechanism.   The vehicle steering apparatus according to claim 1, wherein the second target rotation angle calculation means calculates a second target rotation angle by multiplying the first target rotation angle by a predetermined constant.   The vehicle steering apparatus according to claim 2, wherein the sign of the predetermined constant is negative. The vehicle steering apparatus according to any one of claims 1 to 3, wherein the second target rotation angle is obtained based on a map that stores a second target rotation angle with respect to a first target rotation angle that is created in advance. .

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