JP2003231477A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device for improving a response delay of steering assistance while minimizing excessive assistance and insufficient assistance in regard to a power steering device of a type feeding discharge oil pressure delivered from a reversible pump to a hydraulic power cylinder. <P>SOLUTION: The power steering device is provided with a basic control means for calculating a current command value I (a basic driving current command value) on the basis of a steering effort signal T detected by a steering effort sensor 26, an initial control means for outputting an input command current value Ic (current command value I + initial driving current value I' during non-assistance = initial driving current command value) larger than the current command value I calculated by the basic control means as a driving current value initially provided to an electric motor 36 at a steering start, and a feedback control means for returning to the current command value I calculated by the basic control means when cylinder pressures PR and PL detected by cylinder pressure sensors 40 and 41 reach a predetermined pressure threshold value Ps. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering apparatus that assists steering by a hydraulic power cylinder, and more particularly to control during initial steering.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 2001-1918.
In the power steering device described in the publication, a hydraulic power cylinder connected to a pair of discharge ports of a reversible pump driven by an electric motor steers according to a steering state of a steering shaft detected by a rotary encoder. It is designed to assist with power.

[0003]

However, in the conventional power steering apparatus, when the electric motor is stopped and the steering operation is normally performed in order to reduce the power consumption when the vehicle is traveling straight ahead. , The electric motor is rotated by the drive current output from the controller according to the steering state (steering force signal value) of the steering shaft detected by the rotary encoder, and the reversible pump is rotationally driven by the rotation of the electric motor. Since the discharge hydraulic pressure is increased and the hydraulic power cylinder's hydraulic pressure is increased with this increase in hydraulic pressure to drive the piston to generate steering assist force, the hydraulic power cylinder's hydraulic pressure is increased from the start of steering operation. It takes time for (cylinder pressure) to rise,
This has been a cause of delaying the steering assist response (see the time chart in FIG. 11).

Therefore, Japanese Patent Laid-Open No. 9-175422 discloses that the response speed of steering assist is improved by temporarily setting the rotation speed of the electric motor to the maximum speed at the start of the steering operation. ing. However, the power steering device of this conventional example is provided with a rotary hydraulic control valve between an input shaft and an output shaft connected by a torsion bar, and steering torque (torsion bar Since the hydraulic pressure according to the amount of twist was supplied to the hydraulic power cylinder, even if the electric motor is temporarily rotated at the maximum speed, the hydraulic power cylinder will be driven when the steering assist force is generated. Since the feedback operation that the torsion of the torsion bar becomes smaller is automatically performed, there is no danger of over-assisted state even if the time for maximizing the rotation speed of the electric motor is long, but the drive of the electric motor Power steering device that supplies discharge hydraulic pressure discharged from a reversible pump to a hydraulic power cylinder Is a, for an amount corresponding to a reversible pump is driven hydraulic pressure is discharged into the hydraulic circuit, temporarily become over-assisted, there is a problem that the handle is too lightly. Further, if the time for which the rotation speed of the electric motor is set to the maximum speed is too short, there is a problem that the response delay of the steering assist cannot be sufficiently eliminated.

The present invention has been made by paying attention to the above-mentioned conventional problems, and in a power steering device of a system for supplying a discharge hydraulic pressure discharged from a reversible pump to a hydraulic power cylinder, over-assist or insufficient assist is provided. It is intended to improve the response delay of steering assist while suppressing the minimum.

[0006]

In order to achieve the above-mentioned object, a power steering apparatus according to claim 1 of the present invention comprises a steering shaft linked to a steering mechanism and a hydraulic pressure for assisting the steering force of the steering mechanism. A power cylinder, a reversible pump having a pair of discharge ports for supplying hydraulic pressure to both hydraulic chambers of the hydraulic power cylinder via a first passage and a second passage, and the reversible pump rotating in forward and reverse directions. An electric motor to drive,
Steering direction detecting means for detecting the rotation direction of the steering shaft,
Steering force detecting means for detecting the steering force acting on the steering shaft, and the hydraulic power based on the steering force signal detected by the steering force detecting means and the rotation direction signal of the steering shaft detected by the steering direction detecting means. Basic control means for calculating a basic drive current command value given to the electric motor in order to generate a desired hydraulic pressure in the cylinder, and the steering force detection means as the drive current command value given first to the electric motor at the start of steering. And an initial control unit that outputs a predetermined initial drive current command value that is irrelevant to the steering force signal and is larger than the basic drive current command value calculated by the basic control unit based on the steering force signal. In the power steering device, a cylinder oil pressure detecting means for detecting or estimating the oil pressure in the hydraulic power cylinder, and the cylinder oil pressure detecting means for detecting the oil pressure. And feedback control means for changing the initial drive current command value in accordance with the hydraulic pressure in the pressure power cylinder, and a means is provided with a.

A power steering apparatus according to a second aspect is the power steering apparatus according to the first aspect,
When the feedback control means detects or estimates that the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detecting means has reached a predetermined pressure, the basic control means determines the current command value given to the electric motor. The means is configured to return to the calculated basic drive current command value.

A power steering apparatus according to a third aspect is the power steering apparatus according to the second aspect,
The initial drive current command value output from the initial control means is a maximum allowable current value in the drive circuit that drives the electric motor.

A power steering apparatus according to a fourth aspect is the power steering apparatus according to the first aspect,
The feedback control means sets the maximum value of the value and / or the output time of the initial drive current command value output from the initial control means in response to the increase in the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detection means. Is configured to be variably controlled in the decreasing direction.

A power steering device according to a fifth aspect is the power steering device according to any one of the first to fourth aspects, wherein the cylinder oil pressure detecting means is constituted by the hydraulic power cylinder or the first passage and the second passage. The means is composed of a pressure sensor provided in the hydraulic circuit.

A power steering apparatus according to a sixth aspect is the power steering apparatus according to any one of the first to fifth aspects, further comprising current detecting means for detecting a current flowing through the electric motor, wherein the cylinder oil pressure detecting means is the above-mentioned. The means configured to estimate the hydraulic pressure in the hydraulic power cylinder from the current flowing through the electric motor detected by the current detecting means.

[0012]

In the power steering system according to the first aspect of the present invention, as described above, the steering force detected by the steering force detecting means in the initial control means is used as the drive current command value that is first given to the electric motor at the start of steering. By outputting a predetermined initial drive current command value that is irrelevant to the signal and is larger than the basic drive current command value calculated by the basic control means based on the steering force signal, the hydraulic pressure in the hydraulic circuit is suddenly raised. Therefore, the response delay of the steering assist can be improved. Further, in the feedback control means, the discharge hydraulic pressure discharged from the reversible pump is changed to the hydraulic power cylinder by changing the initial drive current command value according to the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detecting means. In the power steering system of the supply type, it becomes possible to minimize over-assist and insufficient assist.

A power steering apparatus according to a second aspect is the power steering apparatus according to the first aspect,
When it is detected or estimated that the hydraulic pressure in the hydraulic power cylinder reaches a predetermined pressure, the current command value given to the electric motor in the feedback control means is returned to the basic drive current command value calculated by the basic control means. By doing so, it becomes possible to minimize over-assist and insufficient assist with a simple control content.

A power steering device according to a third aspect is the power steering device according to the second aspect.
By setting the initial drive current command value output from the initial control means to the allowable maximum current value in the drive circuit that drives the electric motor, the hydraulic pressure is raised in the shortest time, thereby maximizing the response delay of the steering assist. You can improve.

A power steering apparatus according to a fourth aspect is the power steering apparatus according to the first aspect,
By changing the value of the initial drive current command value and / or the output time output from the initial control means in accordance with the increase of the hydraulic pressure in the hydraulic power cylinder from the maximum value to the decreasing direction, the response that changes according to the hydraulic pressure. The speeds can be averaged, which can reduce the discomfort of steering assist.

According to a fifth aspect of the present invention, there is provided the power steering system according to any of the first to fourth aspects, wherein the cylinder oil pressure detecting means is a pressure sensor provided in the hydraulic power cylinder or a hydraulic circuit. As a result, an accurate steering assist force can be applied.

A power steering apparatus according to a sixth aspect is the power steering apparatus according to any one of the first to fifth aspects, wherein the cylinder oil pressure detecting means detects a current flowing through the electric motor and is detected by the current detecting means. Since the hydraulic pressure inside is estimated, the cost can be reduced by omitting the pressure sensor.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment of the Invention) First, the configuration of a power steering apparatus according to a first embodiment of the present invention will be described with reference to the schematic configuration diagram of FIG.

As shown in FIG. 1, the power steering apparatus according to the first embodiment of the present invention includes a steering shaft 21 to which a steering wheel 20 as a steering input means is connected, and an output shaft at the lower end of the steering shaft 21. 22 racks
Pinions 23, 24, a steering force sensor 26 provided on the lower end side of the output shaft 22 for detecting the steering torque of the steering wheel 20, a hydraulic power cylinder 27 linked to the rack, and a hydraulic pressure for the hydraulic power cylinder 27. And a hydraulic circuit 28 for supplying and discharging the.

In the hydraulic power cylinder 27, a piston rod 30 linked to the rack penetrates through a cylindrical cylinder portion 29 extending in the vehicle width direction, and the cylindrical rod portion 29 is connected to the piston rod 30. A piston 31 that slides inside is fixed. In addition, the cylindrical cylinder portion 2
A left and right first hydraulic chamber 32 and a second hydraulic chamber 33 are separated from each other by a piston 31 inside 9. 25a, 25
Reference numeral b denotes left and right front wheels linked to both ends of the piston rod 30 via links.

The hydraulic circuit 28 is connected to a pair of first and second passages 34 and 35, one end of which is connected to the hydraulic chambers 32 and 33, and the other end of both passages 34 and 35. One reversible pump 37 that can be rotated forward and backward by an electric motor (electric motor) 36 and that selectively supplies hydraulic pressure to the first hydraulic chamber 32 and the second hydraulic chamber 33 from the pair of discharge ports 34a, 35a. , A reservoir 39 which is connected to the reversible pump 37 and stores hydraulic oil therein.

A left cylinder pressure sensor (cylinder oil pressure detecting means) 40 for detecting the left cylinder pressure PL of the first hydraulic chamber 32 is provided in the first passage 34, and a second cylinder pressure sensor 40 is provided in the second passage 35. 2 Right cylinder pressure P in hydraulic chamber 33
A right cylinder pressure sensor 41 (cylinder oil pressure detection means) for detecting R is provided. The reservoir 39 is adapted to supply and replenish the hydraulic oil stored therein to the reversible pump 37 via a supply passage 38, and to replenish the hydraulic oil leaked from each component of the reversible pump 37. It is designed to be collected.

The electric motor 36 is controlled to rotate in the forward and reverse directions by a drive current output from a control unit (basic control means, initial control means, feedback control means) ECU. Based on the steering force signal T from the steering force sensor (steering force detecting means, steering direction detecting means) 26, the drive current for executing steering assist control is output by calculation.

Next, the contents of the electric motor drive control in this control unit ECU will be described based on the control block diagram of FIG. 2, the flowchart of FIG. 3, and the time chart of FIG. First, in the control block diagram of FIG. 2, E1 is an assist pressure calculation unit, E2 is a current command value calculation unit, E3 is an initial drive current value setting unit, E4 is an addition processing unit, E5 is a maximum current value regulation unit, and E6 is An electric motor drive part is shown.

Next, the control contents of each block in the control block diagram of FIG. 2 will be described with reference to the flowchart of FIG. 3. First, in step S101, the steering force signal T detected by the steering force sensor 26 is read. In step S102, the right cylinder pressure PR signal detected by the right cylinder pressure sensor 41 is read, and in step S10
At 3, the left cylinder pressure PL signal detected by the left cylinder pressure sensor 40 is read.

Further, in step S104, as shown in a model in the assist pressure calculating section E1, from the steering force signal T read in step S101, the target steering assist direction and the hydraulic pressure corresponding to the target steering assist force are obtained. The value P is calculated. That is, the steering force signal T of the steering force sensor 26 is output as a positive value in the right turning direction and a negative value in the left steering direction with the neutral position of the steering shaft 21 set to zero. Based on T, the hydraulic pressure equivalent value P of the target steering assist direction and the target steering assist force is calculated as shown in the assist pressure (hydraulic pressure equivalent value P) characteristic diagram with respect to the steering force sensor output value (steering force signal T). The hydraulic pressure equivalent value P is calculated as a positive value in the right turning assist direction and a negative value in the left turning assist direction. Further, when the steering force signal T is within the range of both dead zone threshold values -Ts to Ts (-Ts≤T≤Ts), the dead zone processing for setting the hydraulic pressure equivalent value P to zero is performed.

In the following step S105, the current command value calculation unit E2 calculates the current command value I (basic drive current command value) based on the hydraulic pressure equivalent value P calculated by the assist pressure calculation unit E1. Done. In the current command value calculation unit E2, as schematically shown in the graph in the figure,
A memory for calculating a current command value I corresponding to the hydraulic pressure equivalent value P and a digital calculation circuit are provided.

In subsequent step S106, the initial drive current value setting section E3 sets the non-assist initial drive current value I '. That is, the steering force signal T read in step S101 is the both dead zone threshold value -Ts-
Whether it is within the range of Ts (-Ts ≤ T ≤ Ts), and the right cylinder pressure PR or the left cylinder pressure P read in steps S102 and S103, respectively.
It is determined whether or not L exceeds a predetermined pressure threshold value −Ps to Ps range, and according to the result, the non-assist initial drive current value I ′ of the non-assisted initial drive current value I ′ is processed according to the following processing. Settings are made.

(A) The steering force signal T is a positive value (right steering direction) and exceeds the dead zone threshold Ts (T> Ts),
Further, when the right cylinder pressure PR is equal to or lower than the predetermined pressure threshold Ps (PR ≦ Ps), the initial drive current value setting unit E
In 3, the non-assist initial drive current value I ′ is set to a preset predetermined addition current coefficient k, and then the process proceeds to step S107. In step S107, in the addition processing unit E4, the current command value I calculated in step S105 is added to the initial drive current value I ′ (k) during non-assist.
Is added. That is, at the time of this right steering, by adding the non-assist initial drive current value I ′ (positive value = k) to the current command value I (positive value), the non-assist initial drive current value I ′ is obtained. The input command current value Ic (positive value) (initial drive current command value) added by the amount of is output. Then, after that, the process proceeds to step S108.

(B) The steering force signal T is a negative value (left steering direction) and less than the dead zone threshold -Ts (T <-T
s) and when the left cylinder pressure PL is equal to or higher than a predetermined pressure threshold value -Ps (PL≥-Ps), the initial drive current value setting unit E3 sets the non-assist initial drive current value I'to After setting to the predetermined addition current coefficient −k set in advance, the process proceeds to step S107. This step S10
7, the addition processing unit E4 causes the addition step E10 to be performed.
Processing for adding the non-assist initial drive current value I ′ (− k) to the current command value I calculated in 5 is performed. That is, at the time of this left steering, the current command value I (negative value) is changed to the non-assist initial drive current value I ′ (negative addition current coefficient = −
By adding k), the input command current value Ic (negative value) (initial drive current command value) added by the non-assist initial drive current value I ′ is output. Then, after that, the process proceeds to step S108.

(C) Steering force signal T is both dead zone threshold value-
When it is within the range of Ts to Ts (-Ts≤T≤Ts),
When the right cylinder pressure PR exceeds the predetermined pressure threshold Ps (PR> Ps) or the left cylinder pressure PL is less than the predetermined pressure threshold -Ps (PL <-Ps), the initial value is set. In the drive current value setting unit E3, the initial drive current value I ′ during non-assist is set to zero, and then the step S10
Proceed to 7. In step S107, the addition processing unit E4
At step S105, a process of adding the non-assist initial drive current value I ′ (zero) to the current command value I calculated in step S105 is performed. That is, the current command value I is output as it is as the input command current value Ic (basic drive current command value). Then, after that, the process proceeds to step S108.

In step S108, the maximum current value regulation unit E5 allows the maximum allowable current value Imax in the electric motor drive unit E6 for driving the electric motor 36 with respect to the input current command value Ic calculated in the addition processing unit E4. (-
Imax) limit processing drive current Icm
Maximum current value regulation processing that outputs d is performed.

In the electric motor drive section E6, the electric motor 36 is driven based on the limit processing drive current Icmd output from the maximum current value regulation section E5.
The electric motor drive unit E6 is composed of a power MOSFET or the like, receives the limit processing drive current Icmd as a voltage through a D / A converter (not shown),
The electric motor 36 is drive-controlled. That is, the assist pressure calculation unit E1, the current command value calculation unit E2, and the maximum current value regulation unit E5 constitute the basic control means of the claims, and the initial drive current value setting unit E3 and the addition processing unit E4 are the claims. And an initial control unit and a feedback control unit.

Next, the operation and effect of the first embodiment of the present invention will be described based on the time chart of FIG. 4 showing the state during right steering. First, when the steering force signal T is within the range of both dead zone thresholds -Ts to Ts (-Ts≤T≤Ts).
In the assist pressure calculation unit E1 (step S104), the hydraulic pressure equivalent value P is set to zero (the output of the current command value I in the current command value calculation unit E2 (step S105) is set to zero), and the initial drive current value setting unit is set. E3 (step S10
In 6), by setting the non-assist initial drive current value I ′ to zero, the steering assist force in which the drive of the electric motor 36 is stopped is not generated, that is, dead zone processing is performed. At the neutral position of the steering shaft 21, it is possible to eliminate the complexity of control due to the turning back of the steering that is performed in small steps, and at the same time, the electric motor 3
6 can improve durability and reduce power consumption.

Next, when the steering force signal T is a positive value (right steering direction) and exceeds the dead zone threshold Ts (T> Ts),
The addition processing unit E4 (Step S107) adds the current command value I calculated by the current command value calculation unit E2 (Step S105) based on the hydraulic pressure equivalent value P calculated by the assist pressure calculation unit E1 (Step S104). The initial steering assist force (assist pressure) corresponding to the input command current value Ic obtained by adding the non-assist initial drive current value I ′ (= k) is generated. In this way, by outputting the predetermined input command current value Ic for initial drive that is larger than the current command value I, the hydraulic pressure in the hydraulic circuit 28 can be raised at once, and as a result, the response delay of the steering assist is delayed. Will be able to improve.

Then, after that, the right cylinder pressure sensor 4
When the right cylinder pressure PR detected in 1 exceeds the predetermined pressure threshold Ps (PR> Ps), the initial drive current value setting unit E3 (step S106) adds the current command value I up to then. The recovery process for setting the initial non-assisted initial drive current value I ′ (= k) to zero is performed, whereby the discharge hydraulic pressure discharged from the reversible pump 37 is supplied to the hydraulic power cylinder 27. In the power steering device, it becomes possible to minimize over-assist and insufficient assist. Further, as a means for detecting the cylinder pressures PR, PL, the hydraulic circuit 2
By configuring with the pressure sensors 40 and 41 provided on the No. 8, it becomes possible to give an accurate steering assist force.

Next, another embodiment of the present invention will be described. In the description of the other embodiments of the present invention, the same components as those of the first embodiment of the present invention will not be illustrated and described, or will be denoted by the same reference numerals and the description thereof will be omitted, Only the points will be described.

(Embodiment 2 of the Invention) As shown in the control block diagram of FIG. 5, the power steering apparatus according to Embodiment 2 of the present invention is different from that of Embodiment 1 of the invention in that the initial drive current value is set. A part of the processing content in the section E3 is different. That is, in the second embodiment of the present invention, the steering force signal T exceeds the dead zone threshold value (-Ts to Ts) (-Ts>T> Ts), and the cylinder pressures PR and PL are predetermined. When the pressure threshold value (-Ps to Ps) is within the range (PL ≧ −Ps, PR ≦ Ps), the initial drive current value setting unit E3 (step S106 in FIG. 3 in the first embodiment of the invention). ), The non-assist initial drive current value I ′ is set to the maximum allowable current value Imax in the electric motor drive section E6 that drives the electric motor 36.

In the second embodiment of the present invention, as described above, the non-assist initial drive current value I'is set to the allowable maximum current value Imax, so that the cylinder pressures PR and PL are set in the shortest time. This has the additional effect of maximizing the response delay of steering assist.

(Third Embodiment of the Invention) A power steering system according to a third embodiment of the present invention is provided with a cylinder pressure P.
Depending on whether or not R and PL are within a range of a predetermined pressure threshold value (-Ps to Ps) (PL≥-Ps, PR≤Ps), the initial drive current value I'in the non-assisted state is determined by a predetermined addition current coefficient. Instead of the alternative process of setting k or the maximum allowable current value Imax or setting it to zero, as shown in the control block diagram of FIG. 6 and the flowchart of FIG. 7, the cylinder pressure PR,
This is different from the first and second embodiments of the present invention in that the addition current coefficient k is variably set according to the value of PL.

That is, as shown in the control block diagram of FIG. 6, the initial drive current value setting unit E3 (step S30 of FIG. 7).
7) is added before pressure state addition current coefficient calculation unit E7, and in step S306 of FIG. 7, the pressure state addition current coefficient calculation unit E7 is a map (map of FIG. 8) schematically shown in FIG. ), The right cylinder pressure PR input from the right cylinder pressure sensor 41 or the left cylinder pressure P input from the left cylinder pressure sensor 40.
The variable setting is performed such that the absolute value k of the addition current coefficients k and −k decreases from the maximum value as the absolute value of L increases.

Then, in the subsequent step S307 of FIG. 7, the initial drive current value setting unit E3 sets the non-assist initial drive current value I '. That is, it is only determined whether or not the steering force signal T read in step S301 is within the range of both dead zone thresholds -Ts to Ts (-Ts≤T≤Ts), and both dead zone thresholds are determined. -Ts to T
When the range of s is exceeded (T ≦ −Ts, T ≧ Ts),
The non-assist initial drive current value I ′ is set to the addition current coefficients k and −k that are variably set according to the cylinder pressures PR and PL in the pressure state addition current coefficient calculation unit E7 (step S306), while steering is performed. When the force signal T is within the range between the both dead zone thresholds −Ts to Ts, the non-assist initial drive current value I ′ is set to zero.

Incidentally, steps S301 to S30 in FIG.
5, S308, and S309 are steps S101 to S105, S107, and S107 of FIG. 3 in the first embodiment of the invention.
Since the contents are the same as those in S108, the description thereof will be omitted.

In the third embodiment of the present invention, as described above, the value of the non-assisted initial drive current value I'is set to the right cylinder pressure PR input from the right cylinder pressure sensor 41.
Alternatively, variable setting is performed so that the absolute value of the added current coefficients k, -k decreases from the maximum value as the absolute value of the left cylinder pressure PL input from the left cylinder pressure sensor 40 increases. Cylinder pressure PR, P
The response speed that changes according to L can be averaged,
As a result, the additional effect that the discomfort of steering assist can be reduced can be obtained.

(Fourth Embodiment of the Invention) As shown in the control block diagram of FIG. 9 and the flow chart of FIG. 10, a power steering device according to a fourth embodiment of the present invention is replaced with cylinder pressure sensors 40 and 41. This is different from the first embodiment of the invention in that the cylinder oil pressure detecting means is composed of a motor current sensor (current detecting means) 42 and an oil pressure estimating section E8.

That is, in the fourth embodiment of the present invention, FIG.
In step S402 of 0, the current I ′ flowing through the electric motor 36 detected by the motor current sensor 42 is read, and in step S405, the hydraulic pressure estimation unit E8 calculates the cylinder pressure −P ′, P ′ from the read current I ′. An estimation process is performed. Note that steps S401 and S4 in FIG.
03, S404, S406 to S408 are steps S101 and S10 of FIG. 3 in the first embodiment of the invention.
4, S105, and S106 to S108 have the same contents, and the description thereof will be omitted.

As described above, in the fourth embodiment of the present invention, the motor current sensor 4 is used in the oil pressure estimating section E8.
By estimating the cylinder pressures −P ′ and P ′ from the current I ′ flowing through the electric motor 36 detected in 2,
Compared to the first embodiment of the invention, the cylinder pressure sensor 4
Omission of 0 and 41 has an additional effect that the cost can be reduced.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to the embodiments of the present invention, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention.

For example, in the third embodiment of the invention, the additional current coefficient -k for determining the non-assist initial drive current value I'which is added to the current command value I as the absolute values of the cylinder pressures PR and PL increase. , K is variably set so as to be decreased from the maximum value, but the output time of the non-assist initial drive current value I ′ may be variably set.
In addition, the estimation of the cylinder pressure in the fourth embodiment of the invention can be applied to the other first to third embodiments of the invention.

[0050]

As described above, the present invention claims 1.
In the power steering apparatus described above, a desired hydraulic pressure is generated in the hydraulic power cylinder based on the steering force signal detected by the steering force detection means and the rotation direction signal of the steering shaft detected by the steering direction detection means, as described above. For controlling the basic drive current command value to be given to the electric motor, and the steering force signal detected by the steering force detecting means for the drive current command value initially given to the electric motor at the start of steering In a power steering apparatus including an initial control unit that outputs a predetermined initial drive current command value that is larger than the basic drive current command value calculated by the basic control unit based on a force signal, a hydraulic pressure in a hydraulic power cylinder Cylinder oil pressure detection means for detecting or estimating the oil pressure, and the front according to the oil pressure in the hydraulic power cylinder detected by the cylinder oil pressure detection means. By providing the feedback control means for changing the initial drive current command value, the power steering device of the system that supplies the hydraulic power cylinder with the discharge hydraulic pressure discharged from the reversible pump, The effect that the response delay of the steering assist can be improved while suppressing the shortage to the minimum is obtained.

According to a second aspect of the power steering device of the present invention,
When the feedback control means detects or estimates that the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detecting means has reached a predetermined pressure, the basic control means determines the current command value given to the electric motor. By adopting the means configured to return to the calculated basic drive current command value, it becomes possible to minimize over-assist or insufficient assist with a simple control content.

According to a third aspect of the power steering system of the present invention, in the power steering system of the second aspect,
The initial drive current command value output from the initial control means is a means that is an allowable maximum current value in the drive circuit that drives the electric motor, thereby increasing the hydraulic pressure in the shortest time,
This makes it possible to maximize the response delay of steering assist.

According to a fourth aspect of the power steering device of the present invention,
The feedback control means sets the maximum value of the value and / or the output time of the initial drive current command value output from the initial control means in response to the increase in the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detection means. By adopting the means configured to variably control from the decrease direction to the decrease direction, it is possible to average response speeds that change according to the hydraulic pressure, thereby reducing the uncomfortable feeling of steering assist.

According to a fifth aspect of the power steering system of the present invention, in the power steering system according to any one of the first to fourth aspects, the cylinder oil pressure detecting means is the hydraulic power cylinder or the first passage and the second passage. By using the means configured by the pressure sensor provided in the configured hydraulic circuit, accurate steering assist force can be applied.

According to a sixth aspect of the power steering apparatus of the present invention, in the power steering apparatus according to any of the first to fifth aspects, a current detecting means for detecting a current flowing through the electric motor is provided, and the cylinder oil pressure detecting means. By adopting a means for estimating the hydraulic pressure in the hydraulic power cylinder from the current flowing through the electric motor detected by the current detecting means, the cost can be reduced by omitting the pressure sensor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a power steering device according to a first embodiment of the invention.

FIG. 2 is a control block diagram showing details of electric motor drive control in the power steering device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the contents of electric motor drive control in the power steering device according to the first embodiment of the invention.

FIG. 4 is a time chart showing the contents of electric motor drive control in the power steering device according to the first embodiment of the invention.

FIG. 5 is a control block diagram showing the contents of electric motor drive control in the power steering device according to the second embodiment of the invention.

FIG. 6 is a control block diagram showing the contents of electric motor drive control in a power steering device according to a third embodiment of the invention.

FIG. 7 is a flowchart showing the contents of electric motor drive control in the power steering device according to the third embodiment of the invention.

FIG. 8 is a variable current coefficient characteristic map with respect to cylinder pressure in the power steering system according to the third embodiment of the invention.

FIG. 9 is a control block diagram showing details of electric motor drive control in a power steering device according to a fourth embodiment of the invention.

FIG. 10 is a flowchart showing the contents of electric motor drive control in the power steering device according to the fourth embodiment of the invention.

FIG. 11 is a time chart showing the contents of electric motor drive control in the conventional power steering device.

[Explanation of symbols]

20 Steering Wheel 21 Steering Shaft 22 Output Shaft 23 Rack 24 Pinion 25a Left Front Wheel 25b Right Front Wheel 26 Steering Force Sensor (Steering Force Detection Means, Steering Direction Detection Means) 27 Hydraulic Power Cylinder 28 Hydraulic Circuit 29 Cylindrical Cylinder 30 Piston Rod 31 Piston 32 First hydraulic chamber 33 Second hydraulic chamber 34 First passage (hydraulic circuit) 34a Discharge port 35 Second passage (hydraulic circuit) 35a Discharge port 36 Electric motor (electric motor) 37 Reversible pump 38 Supply passage 39 Reservoir 40 Left Cylinder pressure sensor (cylinder oil pressure detection means) 41 Right cylinder pressure sensor (cylinder oil pressure detection means) 42 Motor current sensor (current detection means, cylinder oil pressure detection means) ECU control unit (basic control means, initial control means, feedback control means)

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3D032 CC02 CC08 CC12 CC48 CC49                       DA15 DA52 DA64 DC08 DC22                       DC33 DC34 DD02 DD17 EA01                       EB11 EC03 EC18 GG01                 3D033 EB02 EB04 HA01

Claims (6)

[Claims] 1. A steering shaft linked to a steering mechanism, a hydraulic power cylinder for assisting the steering force of the steering mechanism, and a first passage and a second passage for both hydraulic chambers of the hydraulic power cylinder. A reversible pump having a pair of discharge ports for supplying oil pressure, an electric motor for driving the reversible pump in forward and reverse rotations, a steering direction detecting means for detecting a rotation direction of the steering shaft, and a steering shaft acting on the steering shaft. Steering force detecting means for detecting the steering force, and a desired hydraulic pressure for the hydraulic power cylinder based on the steering force signal detected by the steering force detecting means and the rotation direction signal of the steering shaft detected by the steering direction detecting means. A basic control means for calculating a basic drive current command value to be given to the electric motor in order to generate the electric current, and the steering force detection means as a drive current command value first given to the electric motor at the start of steering. Initial control means irrelevant to the issued steering force signal and outputting a predetermined initial drive current command value larger than the basic drive current command value calculated by the basic control means based on the steering force signal; In a power steering apparatus provided with the cylinder hydraulic pressure detecting means for detecting or estimating the hydraulic pressure in the hydraulic power cylinder, and the initial drive current command value according to the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detecting means. A power steering device comprising: feedback control means for changing. 2. When the feedback control means detects or estimates that the hydraulic pressure in the hydraulic power cylinder detected by the cylinder hydraulic pressure detecting means has reached a predetermined pressure, a current command value given to the electric motor is set. The power steering device according to claim 1, wherein the power steering device is configured to return to the basic drive current command value calculated by the basic control means. 3. The power steering apparatus according to claim 2, wherein the initial drive current command value output from the initial control means is a maximum allowable current value in a drive circuit that drives the electric motor. 4. The value of an initial drive current command value output from said initial control means and / or said feedback control means in response to an increase in hydraulic pressure in said hydraulic power cylinder detected by said cylinder hydraulic pressure detection means. 2. The power steering device according to claim 1, wherein the power steering device is configured to variably control the output time in a decreasing direction from the maximum value. 5. The cylinder hydraulic pressure detection means is constituted by a pressure sensor provided in the hydraulic power cylinder or a hydraulic circuit constituted by the first passage, the second passage, and the like. The power steering device according to any one of to 4. 6. A current detecting means for detecting a current flowing through the electric motor is provided, and the cylinder oil pressure detecting means estimates the hydraulic pressure in the hydraulic power cylinder from the electric current flowing through the electric motor detected by the current detecting means. The power steering apparatus according to claim 1, wherein the power steering apparatus is configured.