JP4923491B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus including a differential gear device that can change a transmission ratio steplessly from a steering member to a steering mechanism in the middle of a steering shaft.

  Steering of a vehicle is performed by transmitting an operation of a steering member such as a steering wheel to a steering mechanism via a steering shaft, and changing the direction of steering wheels (generally, left and right front wheels) by the operation of the steering mechanism. Is called. In such steering, a good steering feeling can be obtained by changing the correspondence relationship between the operation amount of the steering member and the operation amount of the steering mechanism in accordance with the traveling state such as the vehicle speed and the steering angle. Can do.

  For example, during low-speed or medium-speed driving, the operation amount of the steering mechanism can be made larger than the operation amount of the steering member, and the driving angle can be facilitated by increasing the turning angle of the steering wheel. By making the operation amount of the steering mechanism smaller than the operation amount of the steering member and making the turning angle of the steering wheel small, it is possible to prevent a decrease in running stability due to a sudden driving operation.

  Conventionally, in order to meet such a demand, a differential gear device is arranged in the middle of the steering shaft that connects the steering member and the steering mechanism, and the steering member side (under differential by the differential gear device ( A vehicle steering apparatus has been proposed that transmits rotation from the input side to the steering mechanism side (output side) (see, for example, Patent Document 1).

  The differential gear device includes a sun gear and a ring gear supported on the same axis, a plurality of planetary gears arranged between the gears and meshing with each other, and a differential motor that rotationally drives the ring gear around an axis. The input shaft on the steering member side is fixed to the sun gear, and the output shaft on the steering mechanism side is fixed to the planetary gear carrier, and is interposed in the middle of the steering shaft.

  According to this configuration, when the differential motor is kept in the non-rotating state and the ring gear is fixed, the rotation of the input shaft input to the sun gear is performed at the speed change ratio determined by the number of teeth of the sun gear, the ring gear, and the planetary gear. Thus, the operation amount of the steering member and the operation amount of the steering mechanism are maintained in a certain correspondence relationship.

  On the other hand, when the ring gear is rotated by rotationally driving the differential motor, the rotation of the input shaft input to the sun gear is transmitted to the planetary gear carrier that rotates under engagement with the sun gear and the ring gear. The speed is increased / decreased according to the rotation, and the correspondence between the operation amount of the steering member and the operation amount of the steering mechanism changes according to the rotation direction and rotation speed of the ring gear driven by the differential motor. It becomes.

Further, when the differential motor is driven to rotate while the sun gear is not rotating, the planetary gear rotates between the non-rotating sun gear and the rotating ring gear, and the output shaft fixed to the planetary gear carrier rotates. Thus, the steering mechanism can be operated without depending on the operation of the steering member, and for example, correction steering for correcting a change in the posture of the vehicle due to disturbance such as cross wind and slip can be performed.
JP 2000-302050 A

  In the vehicle steering apparatus including the differential gear device as described above, the rotation of the steering member is transmitted to the steering mechanism by changing the differential ratio steplessly from the deceleration region to the acceleration region, and various traveling states When a practical steering state suitable for (for example, enabling the passage of a roundabout or an intersection with a small operation amount of the steering member) can be obtained, but the differential ratio is changed by driving the differential motor There is a possibility that a problem arises that it is difficult for the driver to experience the actual amount of steering (the amount of operation of the steering mechanism) that occurs in response to the operation of the steering member.

  In order to cope with this problem, the inventors of the present application include a reaction force motor that applies a rotational force to the input side of the differential gear device, and drives the reaction force motor while the differential motor is being driven. Proposed in Japanese Patent Application No. 2005-18174 etc. is a vehicle steering device in which a turning force is applied to a steering shaft on the steering member side so that a driver operating the steering member can experience the amount of steering. Yes.

  In this vehicle steering device, a driver operating a steering member can use a reaction force motor to apply a steering reaction force transmitted from an output-side steering mechanism via a differential gear device. By making it correspond, the actual turning amount on the output side can be experienced through the steering member, and natural steering is facilitated.

  However, in the configuration provided with the reaction force motor as described above, the turning reaction force corresponding to the turning amount changes as the differential motor starts to be driven. Therefore, when the reaction force motor is driven, A reaction force corresponding to the change in the steering reaction force needs to be added, and at this time, the reaction force actually applied to the steering member may change suddenly. This sudden change in steering feeling due to the start of active control signals the driver to start control, that is, tells the driver what is happening to the vehicle at the moment, and then the vehicle This is important steering information for making it easier for the driver to predict what kind of behavior he wants to take, but depending on the driver, he may be disliked as steering information that promotes unnecessary anxiety.

  The present invention has been made in view of such circumstances, and prevents the reaction force applied to the steering wheel from suddenly changing when the reaction force motor provided in the differential gear device starts to be driven. It is an object of the present invention to provide a vehicle steering device that does not cause the vehicle to move.

A vehicle steering apparatus according to a first aspect of the present invention includes a differential gear device that is interposed in the middle of a steering shaft that transmits an operation of a steering member to a steering mechanism, and changes a differential transmission ratio by the differential gear device. A vehicle steering apparatus comprising: a differential motor that is driven as much as possible; and a reaction force motor that is driven to increase or decrease a reaction force applied to the steering member while the differential motor is being driven. the target value, the set as a value obtained by multiplying the angle proportional gain of the steering shaft side of the steering member, comprises a control means for driving and controlling the reaction force motor on the basis of the target value, control means, the steering The turning angle immediately before the drive determination is made by determining whether the differential motor is driven or not based on the detected value of the turning angle and turning torque of the wheel to be steered according to the operation of the member. The proportional gain is determined from the detected value of the steering torque. The target value of the reaction force immediately after the determination of the driving is made, characterized in that determined by using the proportional gain.

Vehicle steering apparatus according to the second aspect of the present invention, the control means in the first shot Ming, in response to stop of the differential motor, the stop driving of the reaction force reaction motor while gradually decreasing the target value of It is characterized by doing.

Upon the vehicle steering apparatus according to a first aspect of the present invention shall be specified target value of the reaction force to be applied to the steering member at the start of driving of the reaction motor, a value proportional to the operating angle of the steering member at the time Based on the detected value of the turning angle and the turning torque, it is determined whether the differential motor is driven or not, and the proportional gain determined from the detected value of the turning angle and the turning torque immediately before the change from the non-drive to the drive. since used, the target value determined, becomes a smooth continuous values in reaction torque is fed back to the steering member before the start of driving of the differential motor, by driving the reaction force motor so as to obtain the target value Thus, it is possible to reliably prevent a sudden change in the reaction force applied to the steering member before and after the start of driving, and to effectively relieve the uncomfortable feeling felt by the driver, thereby providing a good steering feeling.

Furthermore, in the vehicle steering apparatus according to the second aspect of the invention, the reaction force motor is gently stopped while the target value of the reaction force is gradually reduced in response to the stop of the differential motor, so that the reaction force applied to the steering member before and after the stop. The present invention has an excellent effect such that a sudden change in the pressure is eased and a good steering feeling can be given.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing the overall configuration of a vehicle steering apparatus according to the present invention, in which a rotation operation of a steering wheel 1 as a steering member is transmitted to a steering mechanism 3 via a steering shaft 2, and the steering mechanism 3 By operation, the steering wheels 30, 30 arranged on the left and right of the vehicle body are steered.

  The steering mechanism 3 includes a rack shaft 32 that is supported so as to be movable in the axial direction in a rack housing 31 that extends in the left-right direction of a vehicle body (not shown), and a pinion housing 33 that crosses the rack housing 31 in the middle. This is a known rack and pinion type steering mechanism having a pinion shaft 34 rotatably supported therein.

  Both ends of the rack shaft 32 projecting outward from both sides of the rack housing 31 are connected to the left and right steering wheels 30, 30 via separate tie rods 35, 35, and projecting out of the pinion housing 33. The upper end of the pinion shaft 34 is connected to the steering shaft 2 via the intermediate shaft 36. Pinion teeth (not shown) are formed on the outer peripheral surface of the lower half of the pinion shaft 34 extending into the pinion housing 33. The pinion teeth are suitable for the outer surface of the rack shaft 32 at the intersection with the rack housing 31. It is meshed with rack teeth formed over the length.

The steering shaft 2 is rotatably supported in a cylindrical column housing 20 and is supported in an interior of a not-shown passenger compartment while maintaining a tilted posture with the front facing down. A steering wheel 1 is fixed to the projecting end of the shaft 2, and the projecting end of the steering shaft 2 downward is connected to the pinion shaft 34 as described above.
The steering shaft 2 is rotatably supported inside a cylindrical column housing 20, and is supported in a tilted posture with the front facing down inside a passenger compartment (not shown). The steering shaft 2 is divided into two shafts, an input shaft 2a and an output shaft 2b (see FIG. 2), inside the column housing 20, and the steering shaft 2 (input shaft 2a) above the column housing 20 is divided. The steering wheel 1 is fixed to the projecting end of the steering wheel 1, and the projecting end of the steering shaft 2 (the output shaft 2b) downward is connected to the pinion shaft 34 as described above.

  With the above configuration, when the steering wheel 1 is rotated for steering, this rotation is transmitted to the pinion shaft 34 via the steering shaft 2, and the rotation of the pinion shaft 34 is caused between the pinion teeth and the rack teeth. The movement of the rack shaft 32 is converted into a movement in the axial direction of the rack shaft 32 at the meshing portion, and by the movement of the rack shaft 32, the left and right steering wheels 30, 30 are pushed and pulled through the respective tie rods 35, 35. These wheels 30, 30 are steered.

  The vehicle steering apparatus according to the present invention includes a differential gear device 4 in the middle of the column housing 20 that supports the steering shaft 2. This differential gear device 4 transmits rotation transmission from the upper part to the lower part of the steering shaft 2, that is, from the input shaft 2a to the output shaft 2b, steplessly from the deceleration region to the acceleration region. And is configured as described later in the inside of a gear housing 21 in which the diameter of the middle part of the column housing 20 is increased.

  Outside the gear housing 21 are a differential motor 5 that is driven to change the differential ratio, and a reaction force motor 6 that is driven to apply a reaction force to the steering wheel 1 fixed to the upper end of the steering shaft 2. Is installed. The differential motor 5 and the reaction force motor 6 are rotationally driven in both forward and reverse directions in accordance with an operation command given from a differential control unit 7 using a microprocessor to a drive circuit (not shown). The differential ratio is changed by a later-described operation of the differential gear device 4 according to the rotation, and the rotational force of the reaction force motor 6 is transmitted to the steering wheel 1 via the steering shaft 2, and is counteracted to the steering wheel 1. Power is added.

  The differential control unit 7 includes a detection result of the input sensor 22 that detects the rotation angle and torque of the steering shaft 2 above the differential gear device 4, that is, the input shaft 2 a, and the differential gear device 4. The steering shaft 2 in the lower position, that is, the detection result of the output sensor 23 for detecting the rotation angle and torque of the output shaft 2b is given, and further from the running state sensor 24 arranged in each part of the vehicle, The detection results of various running states that affect steering such as the running speed of the vehicle and the lateral acceleration applied to the vehicle body are given.

  Here, the rotation angle detected by the input sensor 22 is a rotation angle generated in the steering shaft 2 (input shaft 2a) by the operation of the steering wheel 1 for steering, and is referred to as a steering angle in the following description. The torque detected by the input sensor 22 is a rotational torque applied to the steering shaft 2 by the operation of the steering wheel 1 and is referred to as steering torque in the following description.

  Further, the rotation angle detected by the output sensor 23 is an angle corresponding to the amount of steering actually generated on the left and right wheels 30 and 30 by the operation of the steering mechanism in accordance with the rotation of the steering shaft 2 (output shaft 2b). In the following description, it is referred to as a steering angle. Further, the torque detected by the output sensor 23 is a torque used for actual turning of the wheels 30 and 30 and is referred to as turning torque in the following description.

  FIG. 2 is a longitudinal sectional view schematically showing the configuration of the differential gear device 4. As shown in the figure, the input shaft 2a and the output shaft 2b constituting the steering shaft 2 are supported so as to be rotatable on the same axis with their front ends abutted on each other. 41 and the output sun gear 42 are integrally formed.

  A plurality of input-side planetary gears 43, 43... Mesh with the outer peripheral teeth of the input sun gear 41, and the outer peripheral teeth of the output sun gear 42 are connected to one side of the input-side planetary gears 43, 43. The output side planetary gears 44, 44... Are engaged with each other by separate support shafts 46, 46... Parallel to the input shaft 2 a and the output shaft 2 b. It is pivotally supported. The carrier 45 is externally fitted to the input shaft 2a and the output shaft 2b with support holes passing through the axis of the end walls on both sides, and is supported so as to be relatively rotatable coaxially with both the shafts 2a and 2b. On the outer periphery of the carrier 45, external teeth 47 having an appropriate width are formed over the entire periphery. The external teeth 47 are connected to the output gear 50 of the differential motor 5 that is driven to change the differential ratio. Meshed.

  Further, a reaction force gear 48 is fitted and fixed to the input shaft 2a outside the support portion of the carrier 45, and the reaction force gear 48 is driven to apply a reaction force to the steering wheel 1. It is meshed with the output gear 60 of the force motor 6.

  With the above configuration, when the differential motor 5 is rotationally driven, this rotation is transmitted to the carrier 45 via the external teeth 47 meshing with the output gear 50, and the input side planetary gear 43 supported by the carrier 45, 43 ... and the output side planetary gears 44, 44 ... revolve coaxially with the input shaft 2a and the output shaft 2b, and are integrated around the shafts of the separate support shafts 46, 46 ... at each position on this revolution. Without spinning. When the reaction force motor 6 is driven to rotate, the rotational force generated by the reaction force motor 6 is transmitted to the input shaft 2a via the reaction force gear 48 meshing with the output gear 60, and the upper end of the input shaft 2a is A rotational torque is applied to the steering wheel 1 fixed to the wheel.

  In the vehicle steering apparatus according to the present invention having such a differential gear device 4, when the steering wheel 1 is rotated for steering, the input shaft 2a connected to the steering wheel 1 rotates and the difference The input sun gear 41 of the moving gear device 4 rotates.

  Here, when the differential motor 5 is not rotationally driven and the carrier 45 is constrained in a non-rotating state, the input sun gear 41 rotates to cause the input-side planetary gears 43, 43. .., And the output side planetary gears 44, 44... That share these support shafts 46, 46. By this rotation, a rotational force is applied to the output sun gear 42 meshing with the output side planetary gears 44, 44, the output shaft 2b provided with the output sun gear 42 rotates, and the pinion shaft 34 further rotates. The steering wheels 30, 30 are steered.

  At this time, rotation transmission from the input shaft 2a to the output shaft 2b is performed at a predetermined differential ratio determined by the number of teeth of the input sun gear 41, the input and output side planetary gears 43 and 44, and the output sun gear 42, and the steering wheel 30 and 30 are steered in an operation direction of the steering wheel 1 by an amount corresponding to an angle (steering angle) obtained by multiplying the operation amount (steering angle) of the steering wheel 1 by the differential ratio.

  At this time, the reaction force torque to which the turning torque of the output shaft 2b used for actual turning of the wheels 30 and 30 is fed back through the differential gear device 4 is added to the input shaft 2a. Therefore, the operation of the steering wheel 1 is performed against this reaction torque.

  On the other hand, when the differential motor 5 is driven to rotate and the carrier 45 is rotated, the input sun gear 42 is rotated by the input-side planetary gears 43, 43... And the output-side planetary gears 44, 44. As a result of the rotation being transmitted to the output sun gear 42, the rotation transmission from the input shaft 2a to the output shaft 2b is made with a differential ratio that is increased (or decreased) by the revolution speed due to the rotation of the carrier 45. The wheels 30, 30 are steered larger (or smaller) than the steering wheel 1 equivalent to the steering angle.

  At this time, the reaction torque applied to the input shaft 2a is also increased or decreased according to the change in the differential ratio of the differential gear device 4, and the operational feeling of the steering wheel 1 made against the reaction torque is changed. The reaction force motor 6 is driven to relieve the change in the operational feeling of the steering wheel 1 by adding the increase / decrease of the reaction force torque generated when the differential motor 5 is driven to the steering wheel 1.

  The differential motor 5 is driven and controlled in accordance with a control command given from the differential control unit 7 based on the detection result of the steering state by the input sensor 22 and the output sensor 23 and the detection result of the traveling state by the traveling state sensor 23.

  For example, the drive control is such that the differential motor 5 is rotationally driven in the same direction as the operation direction of the steering wheel 1 during low-speed or medium-speed travel, and conversely the differential motor is reverse in the operation direction of the steering wheel 1 during high-speed travel. 5 is driven to rotate. As a result, the steering angle of the steering wheels 30, 30 is increased during low-speed or medium-speed traveling, and the driving operation can be easily performed. In addition, the steering angle of the steering wheels 30, 30 is enabled during high-speed traveling. Therefore, the unstable behavior of the vehicle due to sudden steering can be prevented in advance, and the running stability can be improved.

The differential control unit 7 compares the steering angle θ ₁ detected by the output sensor 23 with the steering angle θ ₂ detected by the input sensor 22 and drives the differential motor 5 in accordance with the difference therebetween. Perform the action. Thereby, the correction steering for correcting the inevitable posture change of the vehicle due to disturbance such as a cross wind or slip during traveling can be performed.

  Various drive control procedures of the differential motor 5 by the differential control unit 7 have been proposed in the past, and these can be adopted as appropriate. The vehicle steering apparatus according to the present invention is characterized in the procedure of driving control of the reaction force motor 6 performed as described above while the differential motor 5 is driven.

FIG. 3 is a flowchart showing a procedure for controlling the driving of the reaction force motor 6 by the differential control unit 7. This control is started to drive the reaction force motor 5 as a condition, the differential control unit 7 firstly reads the operation immediately before the start of the steering angle θ ₁ (t _a) and the steering torque T ₁ (t _a) ( Step 1). The turning angle θ ₁ (t _a ) and the turning torque T ₁ (t _a ) are always given as the output of the output sensor 23, and are used for determining whether the differential motor 5 is driven or not, for example. The reading in step 1 is performed from such a history of detected values.

Next, the differential control unit 7 takes in the steering angle θ ₂ (t) given as the output of the input sensor 22 (step 2), applies the steering angle θ ₂ (t) to the following equation, and applies it to the steering wheel 1. A target value T ₂ (t) of the steering torque to be applied is calculated (step 3).

_{T 2 (t) = T 1} (t a) / θ 1 (t a) · θ 2 (t) ... (1)

Next, the differential control unit 7 calculates a target torque to be generated by the reaction force motor 6 in order to apply the steering torque target value T ₂ (t) calculated by the equation (1) to the steering wheel 1 (step 4). ) An operation command is issued to the reaction force motor 6 to obtain the target torque, and the reaction force motor 6 is driven (step 5).

The target value T ₂ (t) of the steering torque calculated by the equation (1) is given as a value proportional to the steering angle θ ₂ (t) at the current time. The steering torque required to steer the vehicle, since changes in accordance with the magnitude of the steering angle, the target value T ₂ of the steering torque given as a value proportional to the steering angle θ ₂ (t) (t) is the current state of the steering state Depending on.

Furthermore (1) In the formula, the proportional gain by multiplying the steering angle theta ₂ (t), beauty turning torque T ₁ at the immediately preceding the start of driving the differential motor 5 (t _a) and the steered angle theta ₁ (t _a ) And the steering torque T ₁ (t _a ) corresponds to the reaction force applied to the steering wheel 1 before the differential motor 5 starts to be driven. Immediately after the start, the target value T ₂ (t) of the steering torque set by the equation (1) is added to the steering wheel 1 to give the driver operating the steering wheel 1 the reaction torque applied before that. A smooth reaction force torque can be experienced and an auxiliary reaction force by driving the reaction force motor 6 can be applied without causing the driver to feel uncomfortable.

The differential control unit 7 checks whether or not the differential motor 5 is stopped (step 6). While the differential motor 5 is continuously driven (step 6: NO), the operations of steps 2 to 5 are performed. Repeatedly, the reaction force motor 6 is continuously driven while the target value T ₂ (t) of the steering torque is updated in accordance with the change of the steering angle θ ₂ (t).

  On the other hand, when the driving of the differential motor 5 is stopped (step 6: YES), the differential control unit 7 gradually decreases the target torque at a predetermined rate of change (step 7), and the target torque becomes zero. (Step 8: YES), the reaction force motor 6 continues to be driven.

  By this operation, reaction force addition by the reaction force motor 6 is lost immediately after the differential motor 5 is stopped, and deterioration of steering feeling due to a sudden change in reaction force applied to the steering wheel 1 can be prevented.

  Moreover, since a rapid change in the reaction force due to the control can be prevented, it is possible to reduce a load applied to the differential gear device and the entire vehicle steering device.

1 is a schematic diagram showing an overall configuration of a vehicle steering apparatus according to the present invention. It is a longitudinal cross-sectional view which shows the structure of a differential gear apparatus schematically. It is a flowchart which shows the procedure of the drive control of the reaction force motor by a differential control part.

Explanation of symbols

1 Steering wheel (steering member)
2 Steering shaft 3 Steering mechanism 4 Differential gear device 5 Differential motor 6 Reaction force motor 7 Differential control unit (control means)

Claims (2)

A differential gear device interposed in the middle of a steering shaft for transmitting an operation of a steering member to a steering mechanism, a differential motor driven to change a differential transmission ratio by the differential gear device, and the differential motor A vehicle steering apparatus comprising: a reaction force motor driven to increase or decrease a reaction force applied to the steering member during driving of the vehicle;
A control means for determining the reaction force target value as a value obtained by multiplying the angle of the steering shaft on the steering member side by a proportional gain, and driving and controlling the reaction force motor based on the target value;
The control means determines whether the differential motor is driven or not based on a detected value of a turning angle and a turning torque of a wheel to be steered according to an operation of the steering member, and the drive is determined. The proportional gain is determined from the detected value of the turning angle and the turning torque immediately before the vehicle, and the target value of the reaction force immediately after the drive is determined is determined using the proportional gain. Steering device.   2. The vehicle steering apparatus according to claim 1, wherein the control unit stops driving of the reaction force motor while gradually decreasing the target value of the reaction force in response to the stop of the differential motor. 3.

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