JP3891275B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus suitable for assisting a driver's steering operation by generating a steering assist force during a steering operation.
[0002]
[Related background]
There is a power steering device as a device that reduces a steering reaction force applied to a steering wheel during a steering operation of a vehicle and supports a driver's steering operation. This device changes the characteristic of the steering assist force (assist characteristic) according to the engine speed or vehicle speed, and uses a light steering force when driving at low speed or when the engine speed is low. When the rotational speed of the engine is high, the steering assist force is not reduced or applied so that the steering operation does not feel uncomfortable.
[0003]
[Problems to be solved by the invention]
However, if the steering assist force of the power steering device is increased for the purpose of reducing the driver's burden due to the steering reaction force during low-speed driving such as a garage entry operation, for example, when stopping after waiting for a signal or the like, There was a problem that the power became too light. Moreover, as described above, if the steering assist force at a low speed is set large, there is a concern that the difference from the steering force at the time of normal traveling becomes large, and the driver feels uncomfortable.
[0004]
The present invention has been made in view of such circumstances, and its purpose is to reduce the burden on the driver due to the steering reaction force during the garage entry operation, and to prevent the driver from feeling uncomfortable with the steering feeling. The object is to provide a steering device.
[0005]
[Means for Solving the Problems]
In order to achieve the above-described object, a power steering device according to the present invention is a power steering device that assists a driver's steering operation by generating a steering assist force during a steering operation, and is a vehicle that accompanies the driver's driving operation. Driving state detecting means for detecting the driving state of the vehicle, garage entering judging means for judging that the vehicle is in the garage according to detection information by the driving state detecting means, and the garage entering judging means When it is determined that the vehicle is in the garage, the steering assist force is gradually increased from the normal time , and when it is determined that the vehicle is in the garage, the increased steering assist force is gradually increased to the normal steering assist force. And a steering assist force control means for returning to. In this case, a driving operation in which the vehicle speed is low and a large steering operation is repeatedly performed, such as stationary parking, parallel parking, switching, and garage entry operation, is defined as garage entry.
[0006]
The garage entry determining means is configured such that the driving operation detecting means determines that the garage entry operation is being performed when a steering input torque greater than or equal to a predetermined value by the driver continues for a predetermined time or less at a predetermined vehicle speed or less.
[0007]
Alternatively, the garage entry determination means is configured to determine that the garage entry operation is being performed when the driving operation detection means has continued for a predetermined time or longer at a steering angle greater than or equal to a predetermined value by the driver at a predetermined vehicle speed or less.
The garage entry determining means is configured such that the driving operation detecting means determines that the garage entry operation is being performed when a steering angular velocity greater than or equal to a predetermined value by the driver continues for a predetermined time or less at a predetermined vehicle speed or less.
[0008]
Preferably , the power steering device is an electric power steering device that generates a steering assist force by an electric motor, and a value of a current that drives the electric motor by the driving operation detection means is a predetermined value or more is a predetermined vehicle speed or less. It is configured to determine that the garage entry operation is in progress when it continues for a predetermined time or more.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings by taking a so-called electric power steering apparatus using an electric motor as a drive source as an example.
FIG. 1 is a diagram showing a schematic configuration of a main part of a power steering apparatus according to this embodiment.
[0010]
In this power steering apparatus, for example, rotation (steering) of a steering wheel 2 transmitted via a steering shaft 1 is applied in the axial direction of a rod (linkage) 3 for changing the direction of a steering wheel (not shown). An electric motor 5 that generates a steering assist force is incorporated in the gear box 4 that converts the displacement. The steering shaft 1 is provided with a steering angle sensor (not shown) for detecting a steering angle, and the gear box 4 is provided with a torque sensor 6 for detecting steering torque. The power steering device further includes a shift position sensor (not shown) for detecting an operation state (shift stage) of the transmission (not shown) and a vehicle speed sensor (not shown) for detecting the vehicle speed.
[0011]
For example, the steering control device 10 realized by a microcomputer or the like includes a driving state detection unit 11 that detects the driving state of the vehicle according to the outputs (steering angle, steering torque, shift stage, vehicle speed) of the various sensors described above, In accordance with the driving state detected by the driving state detection unit 11, a garage insertion determination unit 12 that determines the garage entry state as described later, and the electric motor 5 according to the determination result by the garage entry determination unit 12. And a steering assist force control unit 13 for controlling the operation.
[0012]
In particular, the garage entry determination unit 12 determines whether or not the vehicle is in the garage entry state from the steering angle, steering torque, shift stage, vehicle speed, and the like detected by the driving state detection unit 11. The steering assist force control unit 13 gradually changes the strength of the driving assist force by the electric motor 5 when the garage entry determination unit 12 determines that the vehicle is in the garage entry state, as will be described later. It has become.
[0013]
Now, the steering control device 10 configured as described above performs a control operation on the steering assist force according to an algorithm as shown in FIG. 2, for example. This processing procedure will be described. First, it is determined from the shift state information of the transmission detected by the driving state detection unit 11 whether the garage entry determination unit 12 is in the reverse state (step S1). If the vehicle is not in the reverse state, the driving state detector 11 detects the vehicle speed V (step S2). From this speed information, the garage entry determination unit 12 determines whether or not the vehicle speed V is slower than a preset speed Vth, for example, 5 [km / h] (step S3). When the vehicle speed V is slower than the set speed Vth, the driving state detection unit 11 further detects the driving current I of the electric motor 5 serving as a steering assist force source (step S4). From this current value, the garage entry determination unit 12 determines whether or not the absolute value | I | of the drive current is larger than a preset current value Ith, for example, 20 [A] (step S5).
[0014]
When the drive current I of the electric motor 5 is equal to or less than the set current value Ith in step S5, the steering torque T is detected by the driving state detector 11 (step S10). Then, from the value of the steering torque T, the garage entry determination unit 12 determines whether or not the absolute value | T | of the steering torque is greater than a preset torque Tth, for example, 3 [N · m] (step S11). ). Further, when the absolute value | T | of the steering torque is equal to or smaller than the set torque Tth in step S11, the steering angle θ is detected by the driving state detection unit 11 (step S12). From the value of the steering wheel angle θ, the garage entry determination unit 12 determines whether or not the absolute value | θ | of the steering wheel angle is larger than a predetermined steering wheel angle θth, for example, 180 [°] (step S13). . Further, if the absolute value of the steering wheel angle | θ | is equal to or smaller than the set steering wheel angle θth in step S13, the steering wheel angular velocity Θ (= dθ / dt) is detected by the driving state detection unit 11 (step S15). From the value of the steering wheel angular velocity Θ, the garage entry determination unit 12 determines whether or not the absolute value | Θ | of the steering wheel angular velocity is larger than a predetermined steering wheel angular velocity Θth (= dθth / dt), for example, 180 [° / s]. Is determined (step S16).
[0015]
If the absolute value | I | of the current flowing through the electric motor 5 is larger than the constant current value Ith in step S5, or if the absolute value | T | of the steering torque is larger than the set torque value Tth in step S11, or step S13. In step S15, the steering wheel angle absolute value | Θ | is greater than the set steering wheel angular velocity Θth in step S15, or a combination thereof. The garage entry determination unit 12 determines whether or not the vehicle speed is in a state and the vehicle speed continues for a predetermined time or more at a predetermined speed Vth or less (steps S6 and S7). And when this steering state is continued for a certain time, for example, 3 [s] or more, or when the vehicle is in the reverse state in step S1, the garage entry determination unit 12 determines that the vehicle is in the garage entry state, A command is issued to the steering assist force control unit 13 to set the assist characteristic with the steering assist force increased by one step (step S8).
[0016]
On the other hand, the garage entry determination unit 12 increases the steering assist force during the garage entry operation when it is not the garage entry operation (steps S3, S7, S13) or when the garage entry is completed (steps S3, S7, S16). It is determined whether or not (step S9). When the garage entry determination unit 12 determines that the operation assisting force is increasing during the garage entry operation until just before, the steering assistance force control unit 13 is set so that the operation assisting force is set to an assist characteristic that is weakened by one step. (Step S14). If the garage entry determination unit 12 determines that the operation assisting force has not increased in step S9, the process returns to continue monitoring the vehicle state.
[0017]
As described above, the power steering device using the electric motor 5 as a drive source increases the drive current I of the electric motor 5 to counter the steering reaction force when the steering reaction force is large as in a garage entry operation. And a large steering assist force is obtained. Further, as the garage entry operation time becomes longer, the burden on the driver for the steering operation increases. Therefore, the power steering apparatus according to the present invention gradually increases the assist current I flowing to the electric motor 5 to increase the steering assist force. It has such characteristics. Specifically, when the vehicle is in the garage state, as will be described in detail later, for example, as shown in FIG. 3, when the garage operation is continued for a certain time or longer, the assist current I with respect to the input torque T (steering force) The characteristic is changed from x1 → x2 → x3 to assist the steering operation so that the steering can be performed with a lighter steering reaction force.
[0018]
Then, when the garage entry operation is completed, if the assist characteristic corresponding to the vehicle speed as in the conventional power steering device is suddenly returned from the state in which the steering assist force has increased, the steering torque increases rapidly, so that the driver can perform the steering operation. Will give you a sense of incongruity. In order to eliminate such an uncomfortable feeling of operation, in this apparatus, the characteristic of the assist current I with respect to the input torque T (steering force) is changed from x3 → x2 → x1, and the steering reaction force is gradually increased to obtain the assist characteristic corresponding to the speed. It is configured to return.
[0019]
That is, the conventional power steering apparatus sets the assist characteristic (assist current I) with respect to the input torque T to a characteristic according to the vehicle speed, for example, as shown by the solid line in FIG. That is, when the vehicle speed is low, the assist current I of the electric motor 5 is set to be larger than the input torque T, and the steering assist force is increased and the steering reaction force is weakened. Conversely, when the vehicle speed is high, the assist current I of the electric motor 5 is set to be smaller than the input torque T, so that the driver does not feel uncomfortable with steering.
[0020]
On the other hand, the power steering device of the present invention obtains the same steering assist force (assist force) as the conventional power steering device except during the garage entry operation, but increases the steering assist force during the garage entry operation. Therefore, the steering reaction force is reduced. That is, the assist characteristic is set as shown by the one-dot chain line in FIG. 3 so that the steering assist force is generated with a smaller input torque than the conventional power steering device. Specifically, when the assist characteristic is represented by a dash-dot line of x1, the assist current I starts to flow even if the input torque is smaller than the assist characteristic corresponding to the vehicle speed indicated by the solid line in FIG. Is born by. The increase rate of the assist current I with respect to the rate of change of the input torque T is set so as to be larger than the characteristic according to the conventional vehicle speed.
[0021]
Further, the assist characteristic indicated by the alternate long and short dash line of x2 has a steeper state where the assist current I starts to flow with an input torque T smaller than the assist characteristic indicated by the alternate long and short dash line of x1, and the increase rate of the assist current I is larger than that of x1. Rise characteristic is set. Furthermore, the assist characteristic represented by the dash-dot line of x3 is set to a characteristic in which the assist current I starts to flow with an input torque T smaller than x2, and the increase rate of the assist current I rises sharply compared to x2. Therefore, the increase rate of the assist current I with respect to [x3>x2> x1] and the input torque T is large, so that a larger assist current I flows with respect to the same input torque T, and the input torque is small. Also, the steering assist force is set to be generated.
[0022]
In other words, the power steering apparatus of the present invention provided with such assist characteristics, the more the longer the duration of the garage operations by the above-mentioned decision means, the current flowing through the electric motor 5 is increased, enhancing the steering assist force gradually Thus, the steering reaction force can be made lighter, and the burden on the driver can be reduced.
On the other hand, when the garage operation ends, never discomfort to the driver because it weakens the steering assist force gradually as described above.
[0023]
Further, since the garage entry determination unit 12 determines that the vehicle is not in the garage entry state when the duration of the steering operation is short, the assist characteristic may be set to the control corresponding to the vehicle speed similar to the conventional power steering device, The driver does not feel uncomfortable with the steering operation. Therefore, for example, when stopping while waiting for a signal, etc., and starting while turning right or left, there is no increase in the steering assist force as in garage steering, and the driver who steers the vehicle does not feel strange. .
[0024]
Note that the assist characteristic at the time of entering the garage illustrated in FIG. 3 shows a three-stage characteristic change for easy understanding. Of course, the assist characteristic may be set without being restricted by the set number of steps. Further, in the characteristic illustrated in FIG. 3, the assist current does not exceed a constant current value because it is limited by the allowable input current value of the electric motor 5.
[0025]
Thus, according to the power steering device configured as described above, it is possible to accurately determine that the vehicle is in a state of stationary driving, parallel parking, switching back, garage entry, or the like, and the vehicle is in such a state. when it is possible to enhance the steering assist force gradually. For this reason, an extremely light steering reaction force characteristic can be obtained, so that the operation burden on the driver can be reduced. Further, when returning from the above-described state, the steering assist force is gradually weakened to return to the assist characteristic corresponding to the normal vehicle speed, so that it is possible to maintain the steering performance that does not give the driver a sense of incongruity.
[0026]
The present invention is not limited to the embodiment described above. For example, even in the case of a hydraulic power steering device that uses the hydraulic pressure of an oil pump that is driven by the rotation of an engine as a drive source that generates a steering assist force, for example, assisting by changing the valve opening degree based on the determination procedure described above. The same effect can be obtained if the characteristics are varied. Similarly, the above-described means may be used even for a hydraulic power steering apparatus configured to drive an oil pump with an electric motor.
[0027]
Alternatively, a conventional hydraulically controlled power steering apparatus is provided with an auxiliary electric motor that generates a steering force, and if the steering assist force is generated by the above-described determination procedure, the vehicle enters a garage state. In some cases, an extremely light steering reaction force characteristic can be obtained, and the burden on the driver's steering can be reduced.
[0028]
Furthermore, even if the vehicle steering device is configured by steer-by-wire, the control characteristic (transfer coefficient) of the steer-by-wire may be changed so that the above-described auxiliary characteristics can be obtained.
In the above-described embodiment, the state of the vehicle is determined in the order of (1) reverse, (2) electric motor current, (3) steering torque, (4) steering wheel angle, and (5) steering wheel angular velocity. The order may be changed, or a part thereof may be appropriately combined. As described above, the present invention can be implemented with various modifications without departing from the spirit of the present invention.
[0029]
【The invention's effect】
As described above, according to the power steering device of the present invention, the steering reaction force can be greatly reduced when the vehicle is in a driving operation such as stationary driving, parallel parking, switching back, and garage entry operation. The operation burden can be reduced.
In addition, when returning from the state such as the garage operation described above, the steering assist force is gradually weakened to return to the assist characteristic corresponding to the normal vehicle speed, so that the steering reaction force is not too light and the driver can perform the steering operation. There are many practical effects such as no discomfort.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a control operation of the power steering apparatus according to the embodiment of the present invention.
FIG. 3 is a view showing a characteristic of a steering assist force according to an embodiment of the present invention.
[Explanation of symbols]
1 Steering shaft 2 Steering wheel 3 Rod (linkage)
4 Gearbox 5 Electric Motor 6 Torque Sensor 10 Steering Control Device 11 Driving State Detection Unit 12 Garage Insertion Determination Unit 13 Steering Auxiliary Force Control Unit

Claims (6)

A power steering device for assisting a driver's steering operation by generating a steering assist force during a steering operation,
Driving state detection means for detecting the driving state of the vehicle accompanying the driving operation of the driver;
Garage entry determination means for determining that the vehicle is in the garage according to the detection information by the driving state detection means;
When it is determined by the garage entry determining means that the vehicle is in the garage, the steering assist force is gradually increased from the normal time , and when it is determined that the garage entry of the vehicle is finished, the increased steering assist force is increased. A steering assist force control means for gradually returning the steering assist force to the normal steering assist force. 2. The garage entry determination unit is configured to determine that the garage entry operation is being performed when the driving operation detection unit continues the steering input torque greater than or equal to a predetermined value by the driver at a predetermined vehicle speed or less for a predetermined time or more. Power steering device. The garage determining means is for determining the in garage operations are to claim 1 or 2 when a predetermined value or more of the steering angle continues over a predetermined time equal to or less than a predetermined vehicle speed by the driving operation detection means the driver The power steering apparatus described. The garage determination means according to claim 1 to 3 steering angle speed higher than a predetermined value the driving operation detecting means by the driver is what determines the garage during operation when the predetermined time or longer at or less than a predetermined vehicle speed The power steering device according to any one of the above. The power steering apparatus according to any one of claims 1 to 4 , wherein the garage entry determination means determines that the garage entry operation is being performed when the driving operation detection means detects that the vehicle is operating in reverse . The power steering device is an electric power steering device that generates a steering assist force by an electric motor,
To any one of claims 1 to 5 wherein the driving operation detection means is for determining a garage during operation when the value of the current for driving the electric motor equal to or higher than a predetermined value continues for a predetermined time or more below the predetermined vehicle speed The power steering apparatus described.

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