JP2016020166A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hinder processing from being complicated regardless of reduction in discomfort of a driver in terms of steering operation.SOLUTION: A steering device comprises: a steering mechanism; a steering motor that applies assisting torque to the steering mechanism; and an ECU (a target value arithmetic part and a motor control part) that controls the steering motor so as to generate assisting torque. The ECU performs a steering assistance process in which a target value for assisting torque to be applied by the steering motor according to steering torque τ applied to the steering mechanism is calculated and the steering motor is controlled so as to reach the target value based on the result of the calculation. If it is determined to be positive in both steps S101 and S102 in a backlash reduction process, the steering motor is controlled so as to generate torque in an opposite direction to steering, applied to the steering mechanism prior to the start of the steering assistance process.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a steering device.

  2. Description of the Related Art Conventionally, there is a steering apparatus that includes a steering mechanism that changes the direction of a steered wheel by transmitting the rotation of a steering shaft accompanying the operation of a steering wheel to a rack shaft, and assists the steering operation of the driver (steering assist). . For the steering assist, an actuator such as a motor is used, and the motor and the like are controlled according to the steering operation of the driver.

  On the way from the steering wheel in the steering mechanism to the rack shaft via the steering shaft, there are many mechanical elements that are mechanically connected. The connection itself between the steering shaft and the rack shaft is also a mechanical element mechanically configured like a rack and pinion mechanism. For this reason, the mechanical elements such as the steering wheel to the rack shaft and the connection between the steering shaft and the rack shaft may be loose due to aging of parts, assembly, and manufacturing errors. Such backlash causes a situation where steering assist is performed even though the mechanical elements are not sufficiently connected to each other, and the steering assist is rejected, which makes the driver feel uncomfortable with respect to the steering operation.

  In order to solve such a problem, for example, as described in Patent Document 1, an attempt is made to detect a backlash generated in the steering device from the state of the steering operation.

  For example, as described in Patent Document 2, an attempt is made to correct the rattling detected in this way in consideration of the rattling when calculating the torque generated for steering assist.

JP 2013-244855 A JP 2011-255776 A

  The problem solving according to Patent Document 1 and Patent Document 2 described above needs to always be processed assuming that there is a backlash when controlling steering assist. That is, as the torque generated for steering assist, in addition to the assist torque necessary for assist, a correction torque for correcting such assist torque is required, resulting in complicated processing.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a steering device that can suppress the processing complexity even if the driver feels uncomfortable with respect to the steering operation. .

  A steering device that solves the above problem includes a steering mechanism, a steering actuator that applies assist torque to the steering mechanism, and a control unit that controls the steering actuator to generate assist torque. The control unit calculates a target value of the assist torque applied by the steering actuator in accordance with the steering torque applied to the steering mechanism, and performs a steering assist process for controlling the steering actuator so that the target value is based on the calculation result. When the predetermined condition is satisfied, the control unit controls the steering actuator so as to generate torque in a direction opposite to the steering applied to the steering mechanism prior to the start of the steering assist process.

  As described above, when the steering mechanism is loose due to aging deterioration or assembly of parts and manufacturing errors, by generating torque in the direction opposite to the steering applied to the steering mechanism, It becomes possible to pack the backlash. In addition, the generation of torque in the opposite direction to the steering applied to the steering mechanism is performed prior to the start of the steering assist process, so that the above-described rattling is reduced in the actual steering assist process in this case. become. Therefore, in the steering assist process after the backlash is reduced, the occurrence of a situation where the steering assist is performed although the mechanical elements are not sufficiently connected to each other is suppressed, and the target value is corrected in consideration of the backlash. Such processing is unnecessary. Therefore, even if the driver's uncomfortable feeling with respect to the steering operation is reduced, the complexity of the processing can be suppressed.

  On the other hand, if a torque in the opposite direction to the steering applied to the steering mechanism is generated regardless of the situation, the driver may feel uncomfortable unless the rattling actually occurs. Therefore, in the above configuration, the torque is generated when the torque in the direction opposite to the steering applied to the steering mechanism satisfies a predetermined condition. For this reason, the above-described rattling is reduced in an appropriate situation, and the driver's discomfort with respect to the steering operation can be effectively reduced.

  Such a predetermined condition is that the steering speed applied to the steering mechanism is greater than the predetermined speed and the steering acceleration applied to the steering mechanism satisfies at least one greater than the predetermined acceleration, or the steering torque applied to the steering mechanism is predetermined. It may be smaller than torque. According to these configurations, it is possible to detect that the steering mechanism is being steered, and the situation where torque is generated in the opposite direction to the steering applied to the steering mechanism is effectively applied to the situation where steering assist is required. Can be matched.

  In addition to setting the elements of the predetermined conditions alone, setting a plurality of elements of the predetermined conditions can more effectively cope with the situation where the steering assist is required. For example, it is conceivable to satisfy the predetermined condition when the steering speed applied to the steering mechanism is higher than a predetermined speed and the steering torque applied to the steering mechanism is lower than the predetermined torque. In addition, the condition relating to the steering speed is replaced with the condition relating to the steering acceleration, or the condition relating to the steering torque is removed and the steering speed applied to the steering mechanism is greater than the predetermined speed, and the steering acceleration applied to the steering mechanism is set to the predetermined acceleration. It is also conceivable to satisfy a predetermined condition when satisfying any larger value.

  Further, as a steering device for achieving the above-described effects, a steering shaft provided with a torque sensor for detecting steering torque, a column shaft that is a part of the steering shaft and to which a steering wheel is connected at one end, and a column A steering angle sensor that is provided on the shaft and detects one element for determining the predetermined condition; and a steering gear box that is connected to the column shaft via at least one mechanical element, and further includes a steering actuator. It is recommended that the steering gear box be unitized.

  In the above configuration, the power of the steering actuator acts as an operating torque that becomes an operating source of the steering gear box and an assist torque that assists the operation of the steering gear box. According to this, the backlash caused by the mechanical elements between the steering wheel (particularly the column shaft) constituting the steering mechanism and the steering gear box can be reduced. Therefore, it is possible to expand the range of the effect that effectively reduces the driver's uncomfortable feeling with respect to the steering operation.

  In addition, by providing the steering angle sensor on the steering wheel side of the steering shaft as much as possible than the torque sensor, it is possible to determine the predetermined condition when the backlash is reduced with higher accuracy.

  According to the present invention, even if the driver's uncomfortable feeling with respect to the steering operation is reduced, complication of processing can be suppressed.

The figure which shows the outline of a steering device. The figure which shows a motor control unit. The figure explaining the assist torque computed by steering assist processing. The flowchart explaining the backlash filling process.

Hereinafter, embodiments of the steering device will be described.
As shown in FIG. 1, the steering apparatus of the present embodiment includes a steering mechanism 1 that can change the steering angle of the steered wheels 6 by a driver's operation of the steering wheel 2 (hereinafter referred to as “steering operation”). In the steering mechanism 1, the steering shaft 3 to which the steering wheel 2 is connected is connected to a rack shaft 5 as a steered shaft via a rack and pinion mechanism 4.

  Specifically, the steering wheel 2 is mechanically connected (fixed) to the steering shaft 3 via the mechanical mechanism 2a so as to be rotatable in the radial direction. The steering shaft 3 includes, in order from the steering wheel 2 side, a column shaft 31 to which the steering wheel 2 is connected to one end via a mechanical mechanism 2a, and an intermediate shaft mechanically connected to the column shaft 31 and a universal joint 3a. 32 and a pinion shaft 33 mechanically coupled to the intermediate shaft 32 via the universal joint 3b. The pinion shaft 33 and the rack shaft 5 are arranged with a predetermined crossing angle, and the rack and pinion mechanism 4 is formed by meshing the rack teeth 5a formed on the rack shaft 5 and the pinion teeth 33a formed on the pinion shaft 33. Is configured.

  The rotation of the steering shaft 3 accompanying the operation of the steering wheel 2 by the driver (hereinafter referred to as “steering operation”) is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. Then, the rudder angle of the steered wheels 6 is changed by the reciprocating linear motion of the rack shaft 5.

  Further, a motor as a steering force assisting device that applies an assist force for assisting a steering operation to the rack shaft 5 of the steering mechanism 1, particularly the rack shaft 5 (hereinafter referred to as “steering assist”). A control unit (hereinafter referred to as “MCU”) 10 is provided.

  As shown in FIG. 2, the MCU 10 includes a steering motor 12 as a steering actuator serving as a power source at the time of steering assist, and an ECU 20 as a control unit that controls the operation of the steering motor 12. As the steering motor 12, for example, a three-phase brush motor is employed. A torque sensor 14, a vehicle speed sensor 15, and a steering angle sensor 16 are connected to the ECU 20.

  The torque sensor 14 detects the steering torque τ applied to the steering wheel 2, that is, the steering torque τ applied to the steering mechanism 1. The torque sensor 14 is provided in the vicinity of the torsion bar provided in the portion of the rack and pinion mechanism 4 on the pinion shaft 33 side, and constitutes the steering gear box 11 unitized with the rack and pinion mechanism 4 and the MCU 10. Then, the torque sensor 14 outputs a signal corresponding to the twist of the torsion bar to the ECU 20.

  The vehicle speed sensor 15 detects the vehicle speed V of the vehicle. The vehicle speed sensor 15 is provided in the vicinity of the steered wheel 6. The vehicle speed sensor 15 then outputs a signal corresponding to the rotational speed of the steered wheels 6 to the ECU 20.

  The steering angle sensor 16 detects the steering speed θv of the steering wheel 2. The steering angle sensor 16 is provided in the vicinity of the steering wheel 2 of the steering shaft 3, that is, in the column shaft 31. The steering angle sensor 16 outputs a signal corresponding to the rotational speed of the steering shaft 3 to the ECU 20. The rotational speed is obtained by differentiating the steering angle of the steering shaft 3 and has a positive / negative element and means a rotational direction from positive / negative, that is, a steering direction.

  The steering device transmits the rotation of the steering motor 12 to the rack shaft 5 to apply the motor torque to the steering mechanism 1 as power. The steering motor 12 of the MCU 10 is arranged coaxially with the rack shaft 5 and transmits rotation to the rack shaft 5 via a ball screw mechanism. The power applied by the steering motor 12 acts as an operation torque that is an operation source of the rack shaft 5 and an assist torque that assists the operation of the rack shaft 5. That is, the MCU 10 in the steering device of the present embodiment can function as a steering force generation device or a rack-type electric power steering device.

  The ECU 20 performs a steering assist process for calculating a target value of the assist torque generated by the steering motor 12 based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15 among the various sensors.

  Specifically, the ECU 20 includes a target value calculation unit 21 and a motor control unit 22. The target value calculation unit 21 calculates a motor torque command value Tr * as a target value using a map according to the steering torque τ and the vehicle speed V, and outputs it to the motor control unit 22.

  For example, as shown in the map of FIG. 3, the target value of the assist torque is calculated from the steering torque τ and the vehicle speed V. The target value calculation unit 21 sets the target value to a larger value as the steering torque τ increases. Further, the target value calculation unit 21 decreases the change gradient (assist gradient) of the target value with respect to the steering torque τ as the vehicle speed V increases.

  The motor control unit 22 calculates a current command value based on the motor torque command value Tr * and calculates a voltage command value through current feedback control of the current command value. The motor control unit 22 calculates a motor control signal Sm based on the voltage command value, and controls the supply of drive power to the steering motor 12.

  On the way from the steering wheel 2 to the rack shaft 5 through the steering shaft 3 in the steering mechanism 1 of the present embodiment, there are a plurality of mechanical elements such as a mechanical mechanism 2a and universal joints 3a and 3b. The connection itself between the steering shaft 3 and the rack shaft 5, that is, the rack and pinion mechanism 4, is also a mechanical element configured mechanically like the rack teeth 5a and the pinion teeth 33a. For this reason, mechanical elements such as the connection from the steering wheel 2 to the rack shaft 5 and the rack and pinion mechanism 4 may be loose due to aging deterioration, assembly, and manufacturing errors of parts. Note that the looseness that can be assumed in the present embodiment is the looseness that occurs in the mechanical mechanism 2a, the universal joints 3a and 3b, and the rack and pinion mechanism 4 that are located upstream from the steering motor 12.

  Therefore, the target value calculation unit 21 (ECU 20) of the present embodiment performs the above-described backlash in the steering mechanism 1 based on the steering torque τ and the steering speed θv detected by the torque sensor 14 and the steering angle sensor 16 among various sensors. Performs the backlash filling process. The target value calculation unit 21 performs such backlash processing by applying assist torque by steering assist, that is, prior to starting the steering assist processing.

  As shown in FIG. 4, in the loosening process, the target value calculation unit 21 determines whether or not the steering torque τ is “0 (zero)” (step S101). Step S101 is set as a dead zone for the steering assist. In this embodiment, the dead zone for the steering assist is obtained when the steering torque τ is “0”. That is, the MCU 10 of the present embodiment does not perform steering assist (steering assist processing) when the steering torque is “0”, generates even a small amount of steering torque τ, and steers assist when the steering torque is not “0”. (Steering assist processing) is performed.

  When it is determined in step S101 that the steering torque τ is not “0” (S101: NO), the target value calculation unit 21 shifts from the backlash reduction process to the steering assist process (step S201). On the other hand, when it is determined in step S101 that the steering torque τ is “0” (S101: YES), the target value calculation unit 21 determines whether or not the steering speed θv is larger than the threshold value α (step S102). ). The threshold value α is set to a value that is empirically derived as the steering operation being performed while the vehicle is traveling.

  When it is determined in step S102 that the steering speed θv is equal to or less than the threshold value α (S102: NO), the target value calculation unit 21 shifts from the loosening process to the steering assist process (step S201). On the other hand, when it is determined in step S102 that the steering speed θv is larger than the threshold value α (S102: YES), the target value calculator 21 generates motor torque in the direction opposite to the steering direction (step S103). The steering direction in step S103 is determined from the steering speed θv. In the present embodiment, the determinations in step S101 and step S102 determine whether or not a predetermined condition is satisfied, and the steering torque τ and the steering speed θv, which are the contents of each, are elements of the predetermined condition, that is, parameters. The predetermined condition is satisfied when both of the determinations of step S101 and step S102 are “YES”, and the predetermined condition is not satisfied when either of the determinations is “NO”.

  In step S103, the target value calculation unit 21 controls the rotation of the steering motor 12 so as to generate motor torque in the direction opposite to the steering direction. That is, the target value calculation unit 21 calculates a motor torque command value Tr * as a target value for rotating the steering motor 12 and outputs it to the motor control unit 22. Then, the target value calculation unit 21 repeatedly performs one set of steps S101 to S103, i.e., the backlashing process, in order from the processing of step S101 until either step S101 or step S102 is negative.

  The target value calculation unit 21 sets a predetermined initial target value in step S103 of the first (first set) set prior to the steering assist process. The initial target value is set to a value that is empirically derived as necessary to start the rotation of the steering motor 12 in the direction opposite to the steering direction.

  Then, the target value calculation unit 21 sets the initial target value smaller than the initial target value or the target value of the immediately preceding step S103 in step S103 of the first and subsequent (second and subsequent sets) performed prior to the steering assist process. This is performed each time the set of backlash processing is repeated. That is, the target value calculation unit 21 performs control so that the target value is attenuated every time step S103 is repeated by repeating the backlash filling process.

  In the backlashing process, when the predetermined conditions satisfying both positive determinations in step S101 and step S102 are satisfied, the steering torque τ is “0” and the steering speed θv is larger than α. This is because the steering operation is actually performed, but the steering assist is not possible, the mechanical elements are not sufficiently connected in the middle of the steering mechanism 1, and the operation is transmitted to the entire steering mechanism 1. It can be said that it is not completed. In this way, it is determined whether or not the steering mechanism 1 is rattled and whether or not the steering motor 12 is rotated in the opposite direction of the steering direction so as to be loose.

  In the loosening process, if the predetermined condition in which step S101 is negative is not satisfied, it is possible that the steering torque τ is not “0” and the steering assist has already been performed. In addition, in the backlash processing, when the predetermined condition in which step S101 is affirmative and step S102 is negative is not satisfied, the steering operation is not actually performed or the vehicle is not stored in the garage because the steering speed θv has not reached α. The situation that I put it in can be considered.

According to the steering apparatus described above, the following operations and effects (1) to (6) are achieved.
(1) If the determinations in steps S101 and S102 of the backlash processing are both affirmative, motor torque is generated in the direction opposite to the steering applied to the steering mechanism 1, thereby causing the steering mechanism 1 to If the sticking has occurred, it becomes possible to pack the sticking.

  The generation of the motor torque in the direction opposite to the steering applied to the steering mechanism 1 is performed prior to the start of the steering assist process, so that even if the steering mechanism 1 has a backlash, In the steering assist process, the backlash is reduced.

  For this reason, in the steering assist process after the backlash is reduced, the occurrence of a situation where the steering assist is performed although the mechanical elements are not sufficiently connected to each other is suppressed, and the target value is corrected in consideration of the backlash. No processing is required. Therefore, even if the driver's uncomfortable feeling with respect to the steering operation is reduced, the complexity of the processing can be suppressed.

  (2) On the other hand, if the motor torque in the direction opposite to the steering applied to the steering mechanism 1 is generated regardless of the situation, the driver feels uncomfortable if the rattling is not actually caused as described above. I could give it. Therefore, in the present embodiment, the motor torque in the direction opposite to the steering applied to the steering mechanism 1 is generated when both the determinations in steps S101 and S102 in the backlash processing are affirmative. For this reason, the above-described rattling is reduced in an appropriate situation, and the driver's discomfort with respect to the steering operation can be effectively reduced.

  (3) The contents for which both the determinations in steps S101 and S102 are affirmative satisfy that the steering speed θv of the steering applied to the steering mechanism 1 is larger than the predetermined speed “α” and the steering applied to the steering mechanism 1 It is satisfied that the torque τ is “0”.

  According to these, it can be detected that the steering mechanism 1 is being steered, and the situation where the motor torque is generated in the direction opposite to the steering applied to the steering mechanism 1 is effectively applied to the situation where steering assist is required. Can be matched.

  (4) In the present embodiment, the elements of the conditions for generating the motor torque in the direction opposite to the steering applied to the steering mechanism 1 are independently set so that the determinations in steps S101 and S102 in the backlash processing are both affirmative. In addition, a plurality of parameters such as steering torque τ and steering speed θv are set. Therefore, it is possible to more effectively cope with a situation where steering assist is required.

  (5) In the present embodiment, the motive power of the steering motor 12 is an operating torque that is an operation source of the steering gear box 11, that is, the rack shaft 5, and an assist torque that assists the operation of the steering gear box 11, that is, the rack shaft 5. Works. According to this, the backlash caused by the mechanical elements between the steering wheel 2 (particularly the column shaft 31) constituting the steering mechanism 1 and the steering gear box 11, that is, the portion of the rack shaft 5 to be assisted by steering, can be reduced. become. Therefore, it is possible to expand the range of the effect that effectively reduces the driver's uncomfortable feeling with respect to the steering operation.

  (6) Further, by providing the steering angle sensor 16 on the steering wheel 2 side as much as possible with respect to the torque sensor 14, the determination in step S102 in the backlash processing can be performed with higher accuracy.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the rotation of the steering motor 12 is transmitted to the rack shaft 5 so that the motor torque is applied to the steering mechanism 1 as power. However, the rotation of the steering motor 12 is transmitted to the column shaft 31. It may be. In this case, the MCU 10 and the torque sensor 14 are provided in the vicinity of the column shaft 31. Also in this example, the backlash produced by the mechanical mechanism 2a, the universal joint 3a, etc. in the steering shaft 3 has the same effect as the above embodiment.

  The determination in step S101 in the backlash processing may be set on the condition that the steering torque τ is not “0”. This condition may have a range (width), and may be a range set as a dead zone for steering assist. According to this, the present invention can be applied to a steering device that sets a range of the steering torque τ from “0” to a value β as a dead zone for steering assist. However, the value β is preferably a relatively small value.

  As the predetermined condition, the steering acceleration θa may be used instead of the steering speed θv. The steering acceleration is detected by the steering angle sensor 16 and is output to the ECU 20 as a signal corresponding to the rotational acceleration of the steering shaft 3. The rotational acceleration is obtained by differentiating the rotational speed. However, also in this case, the steering speed θv is used to detect the steering direction of the steering operation. In addition, as the predetermined condition, both the steering speed θv and the steering acceleration θa may be used. In this case, the accuracy of the determination as to whether or not the steering mechanism 1 is rattled is increased.

  The element of the predetermined condition may be set independently, and the loosening process can be simplified by setting or changing only the steering torque τ or only the steering speed θv. When only the steering torque τ is set, if it is determined from the vehicle speed V that the vehicle is traveling, the same effects as in the above embodiment can be obtained.

The processing order of steps S101 and S102 in the backlash processing can be switched. Even in this case, the same effect as the above-described embodiment can be obtained.
A brushless motor can be adopted as the steering motor 12. In this case, a rotation angle sensor that detects the rotation angle of the steering motor 12 and outputs the detection result to the ECU 20 may be provided to control the rotation.

  The steering device of the above embodiment may be a so-called pinion type electric power steering device that applies the power of the steering motor 12 to the pinion shaft 33 (rack and pinion mechanism 4) of the steering gear box 11.

Next, a technical idea that can be grasped from the above-described embodiment and another example (modification) will be additionally described below.
(A) The predetermined torque under the predetermined condition is set as a dead zone for steering assist. According to this configuration, even if there is a dead zone for steering assist in terms of performance, it is possible to pack back in consideration of such a dead zone.

  (B) The steering mechanism includes a steering shaft connected to a steering wheel and a turning shaft connected to a steered wheel, and the steering actuator applies power to the turning shaft of the steering mechanism. is there. According to this configuration, it is possible to close the backlash between the portions of the turning shaft that is steered from the steering wheel that constitutes the steering mechanism. For example, when the steering mechanism is configured to apply power to the pinion shaft of the steering gear box, it is possible to reduce backlash due to mechanical elements between the steering wheel (particularly the column shaft) and the pinion shaft.

  DESCRIPTION OF SYMBOLS 1 ... Steering mechanism, 2 ... Steering wheel, 2a ... Mechanical mechanism, 3 ... Steering shaft, 3a, 3b ... Universal joint, 4 ... Rack and pinion mechanism, 5 ... Rack shaft (steering shaft), 5a ... Rack tooth, 12 DESCRIPTION OF SYMBOLS ... Steering motor (steering actuator), 14 ... Torque sensor, 15 ... Vehicle speed sensor, 16 ... Steering angle sensor, 20 ... ECU (control part), 21 ... Target value calculating part (control part), 22 ... Motor control part (control) Part), 31 ... column shaft, 32 ... intermediate shaft, 33 ... pinion shaft, 33a ... pinion teeth, [tau] ... steering torque, V ... vehicle speed, [theta] v ... steering speed, [theta] a ... steering acceleration.

Claims (4)

In a steering apparatus comprising: a steering mechanism; a steering actuator that applies assist torque to the steering mechanism; and a control unit that controls the steering actuator so as to generate the assist torque.
The controller is
Calculating a target value of the assist torque applied by the steering actuator in accordance with a steering torque applied to the steering mechanism, and performing a steering assist process for controlling the steering actuator to be a target value based on the calculation result;
When a predetermined condition is satisfied, the steering actuator is controlled to generate a torque in a direction opposite to the steering applied to the steering mechanism prior to the start of the steering assist process.   2. The steering apparatus according to claim 1, wherein the predetermined condition satisfies at least one of a steering speed applied to the steering mechanism being higher than a predetermined speed and a steering acceleration applied to the steering mechanism being higher than a predetermined acceleration.   The steering apparatus according to claim 1 or 2, wherein the predetermined condition satisfies that a steering torque applied to the steering mechanism is smaller than a predetermined torque. The steering mechanism is
A steering shaft provided with a torque sensor for detecting the steering torque;
A column shaft that is a part of the steering shaft and is connected to a steering wheel at one end;
A steering angle sensor that is provided on the column shaft and detects one element for determining the predetermined condition;
A steering gear box connected to the column shaft via at least one mechanical element;
The steering apparatus according to any one of claims 1 to 3, wherein the steering actuator is unitized in the steering gear box.