JP2004279295A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily reduce a residual torque to a level not hindering steering control, without requiring technical skill and long time regulation, to reduce a cost, and to stabilize performance. <P>SOLUTION: When a trigger signal is input, a CPU 31 reads an initially set program from a ROM 33, and executes following procedures. (1) The first torque value including the residual torque is detected in the first position where a steering wheel 1 is rotated by a prescribed angle along one direction around a steering wheel axial line from a neutral position, using an assist motor 20, to be stopped there. (2) The second torque value including the residual torque is detected in the second position where the steering wheel 1 is rotated by the same angle along the other direction from the neutral position, to be stopped there. (3) An average value of the first and second torque values is found to offset the negative and positive residual torques, and the average value is determined as an initial torque due to a difference between origin positions of a paired resolvers 12, 12. (4) The initial torque is stored as a correction value for a steering torque in a data storage area 33b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power steering device for a vehicle such as an automobile.
[0002]
[Prior art]
2. Description of the Related Art In a steering device of a vehicle, particularly, a steering device for a vehicle, a power assist mechanism (power steering device) for steering operation is widely and widely used. For this reason, in recent years, most vehicles manufactured in factories are standard equipment, and the number of repairs or replacements performed by dealers (new or used vehicles) is increasing. As such a power steering device, a steering torque applied to a steering wheel shaft via a steering handle is detected by a torque detecting unit, and a driving force corresponding to the steering torque is transmitted from an auxiliary power generating unit such as an electric motor to a steering wheel. It is generally provided (see Patent Document 1 or 2).
[0003]
By the way, when assembling and inspecting the above-described power steering device at the factory production stage or repairing and replacing it at the dealer stage, it is necessary to pay attention to the following.
(1) Residual torque appearing as hysteresis between the steering wheel and the torque detecting means ... Incomplete return of the steering wheel even when the applied torque is removed due mainly to friction in the transmission system existing between the two. Means the torque generated.
(2) When the torque detecting means includes a torsion bar and a pair of angle detection sensors spaced apart from each other in the axial direction, an origin torque caused by a difference between the origin positions of the pair of angle detection sensors, for example, a twin resolver. With a pair of angle detection sensors of the type (see Patent Document 3), it is extremely difficult in terms of manufacturing to assemble the two sensors so that their mounting angle positions are completely matched, and the torque detection means is based on the difference between the origin positions of the two sensors. Detects and gives instructions while including the torque (origin torque).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-168597 [Patent Document 2]
JP 2001-341656 A [Patent Document 3]
JP 2001-194251 A [0005]
[Problems to be solved by the invention]
Therefore, in order to perform initial setting of the steering control of the power steering apparatus, when the steering wheel is held stationary at the neutral position in the steering direction and the applied torque is removed, the torque detecting means determines the origin corresponding to an assembly error in manufacturing. An initial torque including a torque and a residual torque due to an incomplete return of the steering wheel is detected and indicated. Of these, the origin torque cannot be removed unless the torque detecting means is disassembled or adjusted, but it exists as a unique value (constant value) of the device and can be calibrated (can be corrected). Can be specified, the influence on the steady steering control is relatively small. On the other hand, regarding the residual torque, if the residual torque remains (mixes) in the detected value of the initial torque at the time of the initial setting, the state shifts to the steady steering control state, and when the incomplete return of the steering wheel is resolved, There is a strong possibility that the residual torque may cause the steering control to malfunction. A rack assist type power steering apparatus in which auxiliary power generation means and torque detection means are provided in the vicinity of a steering shaft (rack teeth) rather than a column assist type power steering apparatus in which a steering column is provided (Patent Document 2). (Patent Document 1) has a longer distance between the steering wheel and the torque detector, and is more susceptible to residual torque.
[0006]
Regardless of the method of Patent Documents 1 and 2, any of the following operations (1), (2) and (3) must be performed at the time of assembly / inspection in factory production or repair / replacement by a distributor. Was also performed manually (workers).
(1) An operation for holding the steering wheel at a neutral position in the steering direction at rest (2) A small rotational motion is performed while alternately inverting the steering wheel around the axis of the steering wheel to reduce (eliminate) residual torque that appears as hysteresis. Operation {circle around (3)} The operation for detecting the initial torque by the torque detecting means while the steering wheel is held stationary at the neutral position in the steering direction is reduced so that the residual torque approaches 0 in the above (2) (ideally. Requires a long time adjustment work by a skilled technician, so when standardizing a power steering device such as an increase in production costs at a factory or an adjustment error due to a shortage of staff at a sales company, etc. Had become a problem.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to reduce the residual torque easily to a level that does not hinder the steering control without requiring a skilled skill and a long adjustment work, thereby achieving cost reduction and performance stabilization. It is an object of the present invention to provide a power steering device capable of performing the above.
[0008]
Means for Solving the Problems and Effects of the Invention
In order to solve the above-described problems, a power steering device of the present invention includes:
A steering torque applied to the handle shaft via the steering handle is detected by torque detection means including a torsion bar and a pair of angle detection sensors installed separately in the axial direction, and a driving force corresponding to the steering torque is detected. In the power steering device that is configured to give the steering wheel from the auxiliary power generation means,
From a state in which the steering handle is held stationary at the neutral position in the steering direction, at the first position where the steering handle is rotated by a predetermined angle in one direction around the handle axis and stopped using the auxiliary power generating means, A first torque value is detected by the torque detecting means in a form including a residual torque appearing as hysteresis between the steering handle and the torque detecting means, and then the steering handle is moved in the other direction from the neutral position. At the second position stopped by the same angular rotational movement, the second torque value is similarly detected in a form including the residual torque, and the average value of the first and second torque values is obtained to obtain the positive and negative residual torque. And an initial torque detection command for issuing a command to determine the obtained average value as an initial torque mainly caused by the difference between the origin positions of the pair of angle detection sensors. Characterized in that it comprises a stage.
[0009]
Further, in order to solve the above-mentioned problem, the power steering device of the present invention is specifically,
A steering torque applied to the handle shaft via the steering handle is detected by torque detection means including a torsion bar and a pair of angle detection sensors installed separately in the axial direction, and a driving force corresponding to the steering torque is detected. In the power steering apparatus, a command signal for giving the steering wheel from the electric motor as the auxiliary power generation means is transmitted from the steering control unit.
In a first position where the steering handle is rotated by a predetermined angle around the handle axis by a predetermined angle using the electric motor and stopped from the state where the steering handle is held stationary at the neutral position in the steering direction, the steering is performed. A first torque value is detected by the torque detecting means in a form including a residual torque appearing as hysteresis between the steering handle and the torque detecting means, and then the steering handle is turned at the same angle in the other direction from the neutral position. At the second position where the rotary motion is stopped, the second torque value is similarly detected in a form including the residual torque, and the average value of the first and second torque values is obtained to cancel the positive and negative residual torque. And an initial torque detection command means for issuing a command to determine the obtained average value as an initial torque mainly caused by a difference between the origin positions of the pair of angle detection sensors.
Initial torque storage command means for issuing a command to store the initial torque as a correction value of the steering torque in the initial torque storage means of the steering control unit;
It is characterized by having.
[0010]
According to this power steering apparatus, an auxiliary power generation means such as an electric motor already provided for steering control, and a torque detection means including a torsion bar and a pair of angle detection sensors spaced apart in the axial direction thereof. By using (1) and (2), the operation of canceling (removing) the positive and negative residual torques can be performed with high accuracy in a short time without introducing large-scale equipment. In other words, since the initial torque is detected by the torque detecting means while canceling (removing) the positive and negative residual torques by the auxiliary power generating means, the residual (mixing) ratio of the residual torque to the detected value of the initial torque is reduced. It is possible to prevent erroneous operation of the steering control when shifting to the steady steering control state, thereby improving the control stability. Therefore, in the state where the positive and negative residual torques are canceled (removed) as the initial torque detected at the time of the initial setting of the power steering device, the torque is necessarily generated in the torque detecting means including the torsion bar and the pair of angle detection sensors in manufacturing. The origin torque can be detected as accurately and quickly as possible.
[0011]
When an electric motor such as a stepping motor is used as the auxiliary power generating means, the first position and the second position of, for example, ± 5 ° or less can be stably applied to the steering wheel. It is possible to realize an adjustment operation (operation for reducing the residual torque) comparable to that of the user. In addition, the steering control unit provided for performing the steering control of the power steering device stores the initial torque detected after canceling (removing) the positive and negative residual torques as a correction value of the steering torque, so that the steering torque is fixed. It can also contribute to the improvement of control stability in normal steering control.
[0012]
At this time, the initial torque detection command unit and the initial torque storage command unit may be stored in the steering control unit together with the initial setting program, and the initial setting program may be activated by a specific trigger signal transmitted from outside the vehicle. For example, if a portable terminal device (small tester or the like) that can transmit a specific trigger signal is connected to the steering control unit on the vehicle side, the initial setting of the steering control unit can be performed without bringing it to the production factory. It becomes easy to repair or replace various parts and component mechanisms constituting the power steering apparatus at the stage of a trader or the like.
[0013]
Further, in the case where the predetermined time interval is set for the detection of the first and second torque values in the initial torque detection instructing means, it is caused by friction of the transmission system between the first position and the second position. Incomplete return (hysteresis) of the steering wheel is likely to occur. Therefore, it becomes easy to find the residual torque at the time of the initial torque detection operation or the like.
[0014]
Further, in the initial torque detection command means, the first and second torque values are detected by changing the rotation angle of the steering handle around the handle axis or a plurality thereof without changing, so that the positive and negative residual torques are detected. Is improved, and the origin torque can be detected more accurately.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example)
FIG. 1 schematically shows the entire configuration of an electric power steering device as an example of a power steering device to which the present invention is applied (in the present embodiment, “vehicle” is an automobile, The application object of the present invention is not limited to this. In this electric power steering device 100 (hereinafter, also simply referred to as a power steering device), a handle shaft 2 is coupled to a steering handle 1 and fixed to a distal end of a pinion shaft 3 that rotates integrally with the handle shaft 2. The pinion 4 meshes with the rack teeth 5a of the steering shaft 5. The steering angle of the steered wheels 6, 6 is changed by the reciprocating movement of the steering shaft 5 in the axial direction. A DC assist motor 20 (electric motor; auxiliary power generating means) is coaxially mounted on the steering shaft 5 of the power steering device 100 via a ball screw mechanism (not shown). It is configured as a rack assist type in which force assists (power assist) reciprocation of the steering shaft 5 by the steering handle 1.
[0016]
A torque sensor 10 (torque detecting means) is provided between the handle shaft 2 and the pinion shaft 3, and the torque sensor 10 is connected to a torsion bar 11 and a pair of resolvers 12, 12 (angle Detection sensor). When the steering handle 1 is rotated, the torsion bar 11 is twisted, and the rotational angle difference between both ends is measured by the resolvers 12, 12, and the handle is determined from the angle difference measured by the resolvers 12, 12 and the spring constant of the torsion bar 11. The steering torque applied (given) to the shaft 2 is detected. On the other hand, the rotation angle position of the assist motor 20 is detected by a motor angle position detection unit 21 including a rotary encoder or the like. Then, the assist motor 20 outputs, via the motor driver 22, the rotation angle difference of the torsion bar 11 measured by the resolvers 12 and 12 (the steering angle of the steering wheel 1). ), A driving force (rotational force) corresponding to the steering torque detected by the torque sensor 10 is generated.
[0017]
The steering control unit 30 has a CPU 31, a RAM 32, a ROM 33, an input / output interface 34, and the like. The ROM 33 has a program storage area 33a and a data storage area 33b. The program storage area 33a stores a steering control program for controlling the above-described steering angle and steering torque, an initialization program described later, and the like. The data storage area 33b stores an initial torque to be described later, and has a function of an initial torque storage unit. The CPU 31 has various functions as an initial torque detection command unit and an initial torque storage command unit, which will be described later.
[0018]
The initial setting program stored in the program storage area 33a is for detecting an initial torque and storing the detected initial torque in the data storage area 33b. The initial setting program is used as a steering torque correction value in the steering control program. To be used. Here, a small tester (portable terminal device) 40 is connected to the input / output interface 34, and the initial setting program is started by a specific trigger signal transmitted from the tester 40. Initial setting (memory of initial torque) can be easily performed. Of course, an initial setting program is downloaded to the steering control unit 30 from an external microcomputer provided in a production factory or the like via a communication line or a storage medium, and a trigger signal from the external microcomputer is received to perform the initial setting. The program may be started.
[0019]
When a trigger signal is input, the CPU 31 reads an initialization program from the program storage area 33a of the ROM 33, and executes at least the following contents of the program in the following procedure.
{Circle around (1)} From the state where the steering handle 1 is held stationary at the neutral position in the steering direction, at the first position where the steering handle 1 is rotated by a predetermined angle around the handle axis using the assist motor 20 and stopped. The first torque value is detected by the torque sensor 10 so as to include a residual torque that appears as hysteresis between the steering wheel 1 and the torque sensor 10.
(2) Next, at the second position where the steering handle 1 is rotated from the neutral position by the same angle in the other direction and stopped, a second torque value is similarly detected including the residual torque.
(3) The positive and negative residual torques are canceled by calculating the average value of the first and second torque values, and the calculated average value is determined as the initial torque mainly caused by the difference between the origin positions of the pair of resolvers 12, 12. .
(4) The initial torque is stored in the data storage area 33b (initial torque storage means) of the steering control unit 30 as a correction value of the steering torque.
It is preferable that the data storage area 33b be an EPROM so that an initial torque can be written each time the data is initialized.
[0020]
Next, the contents of the steering control will be described with reference to the flowcharts of FIGS. FIG. 2 shows an outline of the steering control program. The presence or absence of an input of a trigger signal from the outside is monitored, and when there is a signal input (YES in S1), the process proceeds to the initialization program S2 (see FIG. 3). If there is no signal input (NO in S1), it is checked whether or not the handle shaft 2 has rotated through the steering handle 1 based on the presence or absence of a change in the angle difference between the pair of resolvers 12, 12 (S3). When the handle shaft 2 is rotated (YES in S3), the steering angle and the steering torque of the handle shaft 2 are detected by the torque sensor 10 (S4). Then, the motor driver 22 is driven, and the assist motor 20 is rotated by the rotational angle difference of the torsion bar 11 measured by the resolvers 12, 12 (the steering angle of the steering wheel 1). Until the angle (angle) coincides, the motor is rotated with a driving force corresponding to the steering torque detected by the torque sensor 10 (S5). If the handle shaft 2 does not rotate (NO in S3), the process ends.
[0021]
FIG. 3 shows details of the initialization program S2. First, in S21, the operator holds the steering wheel 1 at a neutral position in the steering direction. Next, at a first position (for example, 5 ° to the right) at which the steering handle 1 is rotated by a predetermined angle δ in one direction around the handle axis using the assist motor 20 and stopped, the first torque is applied by the torque sensor 10. The torque value T1 is detected (S22). Further, at the second position (eg, 5 ° to the left; 10 ° to the left from the first position) at which the steering handle 1 is rotated from the neutral position by the same angle δ in the other direction and stopped in the other direction, the second movement is similarly performed. The torque value T2 is detected (S23). Then, the positive and negative residual torques are canceled by calculating the average value of the first and second torque values T1 and T2, and the calculated average value is the initial torque mainly caused by the difference between the origin positions of the pair of resolvers 12 and 12. It is determined as T0 (S24). Then, the obtained initial torque T0 is stored in the data storage area 33b of the steering control unit 30 as a correction value of the steering torque (S25).
[0022]
The first and second torque values T1 and T2 detected by the torque sensor 10 each include a residual torque that appears as hysteresis between the steering wheel 1 and the torque sensor 10. However, the positive and negative residual torques are canceled by calculating the average of the two torque values T1 and T2, and the initial torque T0 is mainly occupied by the origin torque (difference between the origin positions of the pair of resolvers 12 and 12).
[0023]
Note that in S21 of FIG. 3, the operator may press the confirmation switch when confirming that the steering wheel 1 is still at the neutral position, and then proceed to the next step.
[0024]
As described above, in the initial torque detecting operation of FIG. 3, the initial torque T0 is obtained only by detecting the first and second torque values T1 and T2 and taking the average value, so that the operation can be completed in a short time. .
In the initial torque detection operation, when a predetermined time interval (for example, 1 second) is set for the detection of the first and second torque values T1 and T2, incomplete return (hysteresis) of the steering wheel 1 may occur. The residual torque is easily generated, and the residual torque can be easily found.
Further, in the initial torque detection operation, when the plurality of first and second torque values T1 and T2 are detected by changing or not changing the rotation angle of the steering handle 1, positive and negative residual torques are detected. Since the accuracy of canceling (removing) is improved, the origin torque can be detected more accurately.
[0025]
The following are precautions when executing the initial setting program stored in the steering control unit 30 in the inspection process of a production factory or the like or the repair process of a dealer or the like.
(1) Start-up with the steering handle 1 held stationary at the neutral position in the steering direction.
(2) Do not apply an applied torque to the steering wheel 1 from outside including the operator.
(3) An engine and a battery are mounted, and the assist motor 20 is operated by the battery.
(4) The steered wheels 6, 6 (wheels) may be in a contact state or a non-contact state (lifted).
[0026]
In the above description, only the rack assist type power steering device has been described, but it is needless to say that the present invention can be applied to a column assist type power steering device. Moreover, as long as the steering wheel and the steered wheels are mechanically connected, the present invention can be applied to a power steering device of a variable steering force type such as a speed-sensitive type or a rotational speed-sensitive type. In addition, a hydraulic motor, a hydraulic cylinder, or the like can be used as the auxiliary power generating means in addition to the electric motor.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of an electric power steering device as an example of a power steering device of the present invention.
FIG. 2 is a flowchart showing the contents of a steering control program.
FIG. 3 is a flowchart showing the contents of an initialization program.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering handle 2 Handle shaft 6 Steering wheel 10 Torque sensor (torque detecting means)
11 torsion bar 12 resolver (angle detection sensor)
20 Assist motor (electric motor; auxiliary power generation means)
30 steering control unit 31 CPU (initial torque detection command means, initial torque storage command means)
33 ROM (initial torque storage means)
100 Power steering device

Claims (5)

A steering torque applied to the handle shaft via the steering handle is detected by torque detection means including a torsion bar and a pair of angle detection sensors installed separately in the axial direction, and a driving force corresponding to the steering torque is detected. In the power steering device that is configured to give the steering wheel from the auxiliary power generation means,
From a state in which the steering handle is held stationary at the neutral position in the steering direction, at the first position where the steering handle is rotated by a predetermined angle in one direction around the handle axis and stopped using the auxiliary power generating means, A first torque value is detected by the torque detecting means in a form including a residual torque appearing as hysteresis between the steering handle and the torque detecting means, and then the steering handle is moved in the other direction from the neutral position. At the second position stopped by the same angular rotational movement, the second torque value is similarly detected in a form including the residual torque, and the average value of the first and second torque values is obtained to obtain the positive and negative residual torque. And an initial torque detection command for issuing a command to determine the obtained average value as an initial torque mainly caused by the difference between the origin positions of the pair of angle detection sensors. Power steering apparatus comprising: a stage. A steering torque applied to the handle shaft via the steering handle is detected by torque detection means including a torsion bar and a pair of angle detection sensors installed separately in the axial direction, and a driving force corresponding to the steering torque is detected. In the power steering apparatus, a command signal for giving the steering wheel from the electric motor as the auxiliary power generation means is transmitted from the steering control unit.
In a first position where the steering handle is rotated by a predetermined angle around the handle axis by a predetermined angle using the electric motor and stopped from the state where the steering handle is held stationary at the neutral position in the steering direction, the steering is performed. A first torque value is detected by the torque detecting means in a form including a residual torque appearing as hysteresis between the steering handle and the torque detecting means, and then the steering handle is turned at the same angle in the other direction from the neutral position. At the second position where the rotary motion is stopped, the second torque value is similarly detected in a form including the residual torque, and the average value of the first and second torque values is obtained to cancel the positive and negative residual torque. And an initial torque detection command means for issuing a command to determine the obtained average value as an initial torque mainly caused by a difference between the origin positions of the pair of angle detection sensors.
Initial torque storage command means for issuing a command to store the initial torque as a correction value of the steering torque in the initial torque storage means of the steering control unit;
A power steering device comprising: The said initial torque detection command means and the said initial torque storage command means are stored in the said steering control part with an initial setting program, The initial setting program is started by the specific trigger signal transmitted from the exterior of a vehicle. Power steering device. The power steering apparatus according to any one of claims 1 to 3, wherein a predetermined time interval is set for the detection of the first and second torque values in the initial torque detection command means. The said initial torque detection instruction | indication means, The said 1st and 2nd torque value are detected by changing the rotation angle of the said steering wheel | steering_wheel around the said handle | steering-wheel axis | shaft, or plural pieces at a time, without changing. 5. The power steering device according to any one of 4.

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