JP2006007923A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device capable of obtaining the optimum steering characteristic corresponding to the precipitous vehicular behavior change accompanied by the sudden change of braking/driving force. <P>SOLUTION: The steering device variably controls a steering gear ratio which is the ratio of the steering angle of a steering wheel 1 relative to a turning angle of front wheels 5, 5 according to steering angle information and vehicle speed information. A steering CU8 predicts the start of transmission operation based on driving force information from an ECU9 and transmission information from an ATCU10, and more increases the steering gear ratio of the steering increase side than the steering gear ratio of the steering return side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to a technical field of a steering device that varies a steering gear ratio, which is a ratio of a steering angle to a steered wheel turning angle, according to a traveling state.

In the conventional steering device, the steering gear ratio is controlled such that the deviation between the target yaw angular velocity calculated from the steering steering angle and the vehicle speed and the detected actual yaw angular velocity is zero (for example, Patent Document 1). reference).
JP-A-6-56048

  However, in the above prior art, the actual vehicle behavior (actual yaw angular velocity) is fed back to control the steering gear ratio, so that, for example, tuck-in (the vehicle is caught inside the turn as the driving torque is lost). When a steep change in vehicle behavior occurs as in (Phenomenon), the steering gear ratio control cannot follow the actual vehicle behavior, resulting in a problem that optimum steering characteristics cannot be obtained.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a steering device capable of obtaining optimum steering characteristics corresponding to a steep vehicle behavior change accompanying a sudden change in braking / driving force. It is in.

In order to achieve the above object, the present invention provides:
In a steering device that variably controls a steering gear ratio, which is a ratio of a steering angle to a steered wheel turning angle, according to a traveling state,
Braking / driving force change predicting means for predicting a braking / driving force change of the vehicle;
Steering gear ratio changing means for changing a steering gear ratio according to the predicted braking / driving force change;
Is provided.

  In the present invention, by changing the steering gear ratio before the vehicle behavior changes due to a change in braking / driving force, the steering gear ratio is faster than in the conventional technique in which the vehicle behavior is detected and feedback control is performed. Can be changed. Therefore, an optimum steering characteristic corresponding to a transient or steep change in vehicle behavior can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a system block diagram of a vehicle to which the steering device of the first embodiment is applied.
The steering wheel 1 is connected to the upper end of the upper column 3a so as to face the driver inside a vehicle interior (not shown). A steering angle sensor 4 for detecting a steering angle is provided between the steering wheel 1 and the upper column 3a.

  The steering mechanism 2 is configured by a rack and pinion type steering device including a pinion integrally formed at the lower end of the lower column 3b and a rack shaft meshing with the pinion. The rack shaft is fixed to the front portion of the vehicle (not shown) so as to be slidable in the left-right direction. Both ends of the rack shaft are connected to front wheels (steering wheels) 5 and 5 via left and right tie rods.

  The steering actuator 6 includes, for example, a DC brushless motor including a speed reducer, and is disposed at a position between the upper column shaft 3a and the lower column shaft 3b. The steering actuator 6 changes the rotation input through the upper column shaft 3a according to the steering gear ratio, and outputs it to the lower column shaft 3b. As a result, the steering gear ratio (θ / δ), which is the ratio of the steering angle θ to the front wheel turning angle δ, is changed.

  The steering angle sensor 4 detects the steering angle θ of the steering wheel 1 and outputs it to a steering control unit (hereinafter referred to as a steering CU) 8. The vehicle speed sensor 7 calculates the vehicle speed from the rotational speed of each wheel and outputs it to the steering CU8.

  The steering CU 8 includes steering angle information from the steering angle sensor 4, vehicle speed information from the vehicle speed sensor 7, driving force information from the engine control unit (hereinafter referred to as ECU) 9, and transmission control unit (hereinafter referred to as ATCU) 10. The gear shift information is input. Then, the steering CU 8 calculates a target steering gear ratio (normal gear ratio) based on the steering angle and the vehicle speed, and outputs a control current for obtaining the normal gear ratio to the steering actuator 6. Further, the steering CU 8 predicts the start of the shift operation from the shift information, and performs control to change the normal gear ratio according to the driving force information from the start of the shift operation to the end of the shift operation.

  Here, the driving force information from the ECU 9 includes the driving torque of the engine. Further, the shift information from the ATCU 10 includes range position information (including shift position information in the case of the manual mode) detected by an inhibitor switch (shift position detecting means) 11 provided on the select lever 12, and the ATCU 10 It includes shift command information output to an external automatic transmission, mode information indicating the current transmission mode (auto mode and manual mode), clutch operation information indicating the clutch engagement / release state, and the like.

  The normal gear ratio is set based on a steering gear ratio map set in advance according to the vehicle speed. Steering gear ratio characteristics are low in the low to medium speed range by reducing the steering gear ratio to make the steering response quick, and in the high speed range by increasing the steering gear ratio to make the steering response slow. It is set so that both a light and good steering feeling and a gentle and stable steering feeling in a high speed range can be achieved at the same time.

Next, the operation will be described.
[Transmission mode start prediction by transmission mode]
In the first embodiment, different shift operation start prediction is performed depending on whether the transmission mode is the manual mode or the auto mode.

a) In the manual mode In the manual mode (in the first embodiment, the driver operates the select lever 12 to change speed, and in the case of MT, the driver operates the shift lever to change speed). The shift position is detected using the inhibitor switch 11 provided on the select lever 12, and it is predicted that the driving torque will be lost and the driving force will be reduced due to the shift operation by the operation of the driver. Change the steering gear ratio.

b) When in auto mode In auto mode (when the gear shift itself is automatically performed by the ATCU 10), a drive torque drop occurs due to a shift operation being executed from the gear shift command information from the ATCU 10, and the driving force decreases. To change the steering gear ratio.

[Steering gear ratio change control processing]
FIG. 2 is a flowchart showing the flow of the steering gear ratio change control process executed by the steering CU 8, and each step will be described below.

  In step S1, driving force information (driving torque) is input from the engine CU9, and the process proceeds to step S2.

  In step S2, according to the driving torque read in step S1, the steering gear ratio for the additional steering (the additional gear ratio) and the steering gear ratio for the reverse steering (the reverse gear ratio) are calculated. The process proceeds to step S3. Note that the additional gear ratio is set larger than the normal gear ratio, and the reverse gear ratio is set smaller than the normal gear ratio. As the driving torque increases, the reduction in driving force generated during the speed change operation increases, so the amount of change from the normal gear ratio is increased.

  In step S3, mode information is input from the ATCU 10 to determine the current transmission mode. If it is in the auto mode, the process proceeds to step S4, and if it is in the manual mode, the process proceeds to step S6.

  In step S4, shift command information is input from the ATCU 10, and it is determined whether the shift has started (corresponding to braking / driving force change predicting means). If YES, the process proceeds to step S8, and if NO, the process proceeds to step S5.

  In step S5, normal control based on the normal gear ratio is continued, and the process proceeds to return.

  In step S6, range position information is input from the ATCU 10, and it is determined whether or not shifting has started (corresponding to braking / driving force change prediction means). If YES, the process moves to step S8, and if NO, the process moves to step S7. Here, in a vehicle equipped with a manual transmission of a manual clutch, it is determined that the shift has started when the clutch is released based on the clutch operation information (corresponding to braking / driving force change prediction means).

  In step S7, as in step S5, normal control is continued, and the process proceeds to return.

  In step S8, the steering gear ratio is switched between the additional gear ratio and the return gear ratio calculated in step S2 (corresponding to steering gear ratio changing means), and the process proceeds to step S9.

  In step S9, the shift command information and the range position information are input from the ATCU 10, it is determined whether or not the shift is completed, and it is predicted whether the drive force increases after the drive force decreases. If YES, the process moves to step S10, and if NO, the process moves to step S8. Here, if the clutch operation information indicates that the clutch is engaged, it can also be determined that the shift has been completed.

  In step S10, the driving force is predicted to increase after decreasing and the behavior of the vehicle being caught in the turning inner wheel is lost. Therefore, the steering gear ratio switched in step S8 is returned to the normal gear ratio, and the process proceeds to return.

[Steering gear ratio change control operation]
In the flowchart of FIG. 2, the process proceeds from step S1 to step S2 to step S3, and in the auto mode, the process proceeds from step S3 to step S4 to step S5 to step S8. In the mode, the flow proceeds from step S3 to step S6 to step S8.

  That is, in step S2, the steering gear ratio corresponding to the drive torque is calculated, and in step S8, the steering gear ratio is switched from the normal gear ratio, the increase side is larger than the normal gear ratio, and the return side is set. Make it smaller. Therefore, the steering response becomes slower at the time of turning-up steering than at the time of normal control, and the steering response becomes quicker at the time of turning-back steering than at the time of normal control.

  The above-described steering gear ratio change control is continued until the shift is completed, and when the shift is completed, the process proceeds from step S8 to step S9 to step S10. In step S10, the steering gear ratio is returned to the normal gear ratio. .

  If the shift is not started, in the flowchart of FIG. 2, the flow proceeds from step S1 → step S2 → step S3 → step S4 → step S5 or step S1 → step S2 → step S3 → step S6 → step S7. In S5 or step S7, control by the normal gear ratio is continued.

[Steering gear ratio changing action when shifting start is predicted]
As shown in FIG. 3, the vehicle behavior of tuck-in is a behavior in which the vehicle is caught inside the turn (inside) from the target line, which is caused by a drive torque loss due to a shift during the turn, and the tire lateral force is This is due to the rapid increase.

  As shown in FIG. 4, in the steering device according to the first embodiment, when the shift operation is predicted, the steering device according to the first embodiment has an increase in the left side steering during the left turn with respect to the steering steering angle. The steering gear ratio is changed so that the tire turning angle becomes smaller and the tire turning angle with respect to the steering steering angle becomes larger on the return side (right steering while turning left).

  As a result, the steering response on the increase side becomes slower and the steering response on the return side becomes quicker. Therefore, the front wheels 5 and 5 are less likely to be steered to the increase side, and are easily steered to the return side. Become. Therefore, when drive torque loss occurs, excessive incision to the in side is suppressed, and the travel line can be brought closer to the target line as compared with the case of the normal gear ratio.

  Further, the rapid increase in the lateral force of the tire due to the drive torque loss increases as the engine drive torque increases. In the first embodiment, the amount of change in the steering gear ratio increases as the engine drive torque increases. The steering gear ratio can be set according to the amount of change in the tire lateral force, and the tuck-in behavior can be effectively suppressed.

  FIG. 5 is a time chart illustrating the operation of changing the steering gear ratio according to the first embodiment. When the shift start operation of the automatic transmission is predicted at time t1, the change of the steering gear ratio is started.

  At time t2, the shift operation of the automatic transmission is started, but at this time, the change of the steering gear ratio has already been completed, the additional gear ratio is larger than the normal gear ratio, and the reverse gear ratio is the normal gear ratio. Therefore, an excessive increase in yaw rate due to the tuck-in behavior is suppressed even though the drive torque is lost during the shift operation.

  At the time point t3, since the speed change operation is completed, the steering gear ratio is returned to the normal gear ratio.

Next, the effect will be described.
In the steering device of the first embodiment, the effects listed below can be obtained.

  (1) Since the braking / driving force change predicting means for predicting the braking / driving force change of the vehicle and the steering gear ratio changing means for changing the steering gear ratio according to the predicted braking / driving force change are provided, The steering gear ratio can be changed more quickly than in the conventional device that detects and performs feedback control, and an optimum steering characteristic corresponding to a transient or steep change in vehicle behavior can be obtained.

  (2) When the braking / driving force change predicting means predicts a decrease in the driving force, the steering gear ratio changing means increases the steering gear ratio on the increasing side more than the steering gear ratio on the returning side, so that the driving torque Tuck-in behavior due to omission can be suppressed.

  (3) The steering gear ratio changing means increases the amount of change in the steering gear ratio as the current braking / driving force increases, so the steering gear ratio can be set according to the increase in tire lateral force due to driving torque loss, Tuck-in behavior can be effectively suppressed.

  (4) An inhibitor switch 11 for detecting the shift position of the select lever 12 of the transmission operated by the driver is provided, and the steering gear ratio changing means predicts a decrease in driving force based on a change in the shift position. It is possible to accurately predict a decrease in driving force in the manual mode.

  (5) Since the steering gear ratio changing means predicts a decrease in driving force based on the shift command information output from the ATCU 10, it can accurately predict a decrease in driving force in the auto mode.

(6) Since the clutch operation information output from the ATCU 10 predicts that the driving force will decrease when the clutch is released, it is possible to accurately predict the reduction in driving force in a vehicle equipped with a manual clutch manual transmission. .
(7) The steering gear ratio changing means is driven by shifting to return the changed steering gear ratio to the normal gear ratio when an increase in driving force is predicted after the driving force is reduced by the braking / driving force change predicting means. When there is no risk of torque loss, returning the steering gear ratio to the normal gear ratio can prevent a sense of incongruity caused by the difference in steering characteristics between the increase and the return.

  The steering device according to the second embodiment is an example in which the amount of change in the steering gear ratio is varied according to the driving method of the vehicle. In addition, since the structure of Example 2 is the same as the structure of Example 1 shown in FIG. 1, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted.

Next, the operation will be described.
[Steering gear ratio changing action according to drive system]
Tack-in itself occurs in any drive system vehicle, but as described above, the cause of tuck-in is an increase in tire lateral force due to drive torque loss. For this reason, front-wheel drive vehicles such as front-wheel drive vehicles (front engines and front-wheel drive vehicles) such as front-wheel drive vehicles that drive and steer both on the front wheels are driven by rear wheels such as FR vehicles (front engines and rear-wheel drive vehicles). Compared to cars, tuck-in behavior is noticeable.

  Therefore, in the second embodiment, in consideration of the driving system of the vehicle, as shown in FIG. 6, when the steering gear ratio is changed by predicting the start of the shift operation, if the vehicle is an FF vehicle, the change amount is set to the FR vehicle. Set larger than. That is, in the case of an FF vehicle, the steering gear ratio on the additional side is set larger than that on the FR vehicle, and the steering gear ratio on the return side is set smaller than that on the FR vehicle.

Next, the effect will be described.
In addition to the effects (1) to (6) of the first embodiment, the steering apparatus of the second embodiment provides the following effects.

  (8) When the vehicle is a front-wheel drive vehicle such as a front-wheel drive vehicle, the steering gear ratio change means increases the amount of change in the steering gear ratio compared to a rear-wheel drive vehicle such as a FR vehicle. The tuck-in behavior can be more effectively suppressed in the FF vehicle in which the tuck-in behavior becomes more prominent.

(Other examples)
The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments, and the gist of the present invention. Any design change or the like within a range that does not deviate from the above is included in the present invention.

  For example, in the first embodiment, the steering gear ratio is variably controlled according to the vehicle speed information. However, the steering gear ratio variable control including a traveling state other than the vehicle speed may be used.

In the first embodiment, an example in which a shift start is predicted for each transmission mode (auto mode, manual mode) in a vehicle equipped with an automatic transmission is shown. However, a vehicle equipped with a manual transmission of an automatic clutch without an auto mode is shown. In this case, since the shift start determination is always performed according to the shift position information, the flow of FIG. 2 always proceeds from step S3 to step S6.
In addition, although the example in which the change amount of the steering gear ratio is set according to the engine driving torque has been shown, the braking / driving force control amount when the engine speed or the braking / driving force control device is installed. Alternatively, a braking / driving force detection value may be used.

1 is a system block diagram of a vehicle to which a steering device according to a first embodiment is applied. It is a flowchart which shows the flow of the steering gear ratio change control process performed by steering CU8. It is explanatory drawing which shows the vehicle behavior of tuck-in. It is a figure showing the tire turning angle with respect to the steering angle which shows the steering gear ratio change method of Example 1. FIG. 6 is a time chart showing the steering gear ratio changing operation of the first embodiment. 6 is a time chart showing a steering gear ratio changing operation of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering mechanism 3a Upper column 3b Lower column 4 Steering angle sensor 5 Front wheel 6 Steering actuator 7 Vehicle speed sensor 8 Steering control unit 9 Engine control unit 10 Transmission controller 11 Inhibitor switch 12 Select lever

Claims (8)

In a steering device that variably controls a steering gear ratio, which is a ratio of a steering angle to a steered wheel turning angle, according to a traveling state,
Braking / driving force change predicting means for predicting a braking / driving force change of the vehicle;
Steering gear ratio changing means for changing a steering gear ratio according to the predicted braking / driving force change;
A steering apparatus characterized by comprising: The steering apparatus according to claim 1, wherein
The steering gear ratio changing means increases the steering gear ratio on the increase side more than the steering gear ratio on the return side when the decrease in driving force is predicted by the braking / driving force change prediction means. Steering device. The steering apparatus according to claim 2, wherein
A braking / driving force detecting means for detecting the current braking / driving force is provided,
The steering gear ratio changing means increases the amount of change in the steering gear ratio as the current braking / driving force increases. The steering apparatus according to any one of claims 1 to 3,
Provided with a shift position detecting means for detecting the shift position of the shift lever of the transmission operated by the driver,
The braking / driving force change predicting means predicts a decrease in driving force based on a change in shift position. The steering apparatus according to any one of claims 1 to 4, wherein:
The transmission is an automatic transmission that automatically performs a shift in response to a shift command from an automatic transmission control means,
The braking / driving force change predicting means predicts a decrease in driving force based on a shift command output from the automatic transmission control means. The steering apparatus according to any one of claims 1 to 3,
A clutch operation detecting means for detecting the state of engagement / disengagement of the clutch of the transmission;
The steering / braking force change predicting means predicts that the driving force decreases when the release of the clutch is detected. The steering apparatus according to any one of claims 1 to 6,
The steering gear ratio changing means returns the changed steering gear ratio to a normal gear ratio when the braking / driving force change predicting means predicts an increase in driving force after a decrease in driving force. Steering device. The steering apparatus according to any one of claims 1 to 7,
The steering gear ratio changing means increases the amount of change in the steering gear ratio when the vehicle is a front wheel drive vehicle as compared with the case of a rear wheel drive vehicle.

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