JP2001354151A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of excellently controlling stopping or deceleration of an electric motor regardless of a fluctuation in source voltage. SOLUTION: An oil pump 26 is driven by the electric motor 27, and steering assisting force is imparted to a steering mechanism 1 by generating hydraulic pressure of this oil pump 26. An electronic control unit 30 controls the electric motor 27 at a rotating speed set according to a steering speed via a driving circuit 28. A motor current is detected by a current detecting circuit 12. One of the requirements for stopping the electric motor 27 is that the motor current becomes a motor stopping judging current value Istop or less. The electronic control unit 30 variably sets the motor stopping judging current value Istop according to battery voltage VB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for applying a steering assist force to a steering mechanism by a hydraulic pressure generated by a pump driven by an electric motor.

[0002]

2. Description of the Related Art There is known a power steering apparatus which assists operation of a steering wheel by supplying hydraulic oil from an oil pump to a power cylinder connected to a steering mechanism. The oil pump is driven by, for example, an electric motor composed of a DC motor, and a steering assist force corresponding to the rotation speed is generated from a power cylinder.

[0003] The drive control of the electric motor is performed, for example, based on the steering angular velocity of the steering wheel. That is, the steering angular speed is obtained based on the output of the steering angle sensor provided in connection with the steering wheel, and the target rotation speed of the electric motor is set based on the steering angular speed. A voltage is supplied to the electric motor so that the target rotation speed is achieved. More specifically, when the steering angular velocity is extremely low, the steering wheel is slightly operated, so that it is considered that steering assist is not necessary, and the electric motor is stopped. On the other hand, if the steering angular velocity is large,
It is considered that the steering wheel is largely operated, and the electric motor is driven in accordance with the steering angular velocity at that time, and a steering assist force is generated.

When the vehicle is traveling on a straight road having a slope in the vehicle width direction, it is necessary to apply torque to the steering wheel and maintain the steering wheel at a constant steering angle in order to stabilize the vehicle. Therefore, if the stop control of the electric motor is performed based only on the steering angular velocity, the steering assist is not performed in the above case, and the steering feeling may be deteriorated. Therefore, conventionally, the condition that the steering angular velocity is equal to or less than a predetermined steering angular velocity threshold and the motor current flowing through the electric motor is equal to or less than the predetermined current threshold continues for a certain period of time, The electric motor is stopped (for example, WO99 / 089).
22).

When a torque is applied to the steering wheel, a load is applied to the electric motor, so that the load current of the electric motor increases to achieve the target rotational speed. That is, the motor current corresponds to the torque applied to the steering wheel. The above prior art is
Focusing on this point, it is a necessary condition when stopping the electric motor that the motor current is equal to or less than the current threshold value.

[0006]

The electric motor operates by receiving power supply from a battery mounted on a vehicle. In this vehicle-mounted battery, the generated voltage (battery voltage) is not always stable. In particular, when the battery voltage drops,
Failure occurs in stop control of the electric motor. That is, when the battery voltage decreases, the power supplied to the electric motor decreases, and the rotation speed of the electric motor decreases. Therefore, the controller that controls the electric motor uses the power shortage due to the decrease in the battery voltage to achieve the target rotation speed.
Try to compensate by increasing the motor voltage. As a result, the motor current takes a large value even when the load on the electric motor is small.

Therefore, even in the no-load state, the motor current does not fall below the current threshold value, and the electric motor cannot be stopped. As a result, power is wasted. Therefore, an object of the present invention is to
An object of the present invention is to provide a power steering device that solves the above-described technical problem and that can favorably perform stop or deceleration control of an electric motor without depending on fluctuations in a power supply voltage.

[0008]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the present invention, a steering assist force is generated by a hydraulic pressure generated by a pump (26) driven by an electric motor (27). In the power steering apparatus for generating electric power, a power supply (4
Power supply voltage detecting means (3) for detecting the voltage (VB)
0, S12), current detection means (12, S11) for detecting the value of the motor current flowing through the electric motor,
A current threshold value (Istop) which is a threshold value for a motor current value when the electric motor is stopped or decelerated to a predetermined idle rotation speed (Ri) based on the power supply voltage detected by the power supply voltage detection means. Threshold value setting means (30, S13) for variably setting the motor threshold value, and a state where the motor current value detected by the current detection means is equal to or less than the current threshold value set by the current threshold value setting means. Motor control means (3) for stopping the electric motor or decelerating the electric motor to the idling rotational speed on condition that the electric motor continues for a time.
0, S14, S16, S17). Alphanumeric characters in parentheses
This represents a reference numeral of a corresponding component in an embodiment to be described later.
Hereinafter, the same applies in this section.

According to the present invention, the current threshold value is variably set according to the fluctuation of the power supply voltage. The requirement that the motor current value be equal to or less than the variably set current threshold value is a necessary condition for stopping the electric motor or decelerating the electric motor to the idle rotation speed. Therefore, even if the power supply voltage fluctuates, when the load on the electric motor is small, the motor current value is surely equal to or less than the current threshold value. In addition, the electric motor can be stopped or decelerated.

As a result, wasteful power consumption can be reduced, and the energy saving of the power steering device can be improved. It is preferable that the current threshold value setting means sets the current threshold value higher as the power supply voltage is lower. With this, when the power supply voltage decreases, even when the motor current value increases to rotate the electric motor at the target rotation speed, the motor current value can be set to a value equal to or less than the current threshold value. it can.

The motor current value of the electric motor is determined by its load,
That is, it changes according to the steering torque. Therefore, if the electric motor is stopped or decelerated on condition that the state in which the motor current value has a value equal to or less than the current threshold value corresponding to the steering torque range in which the steering assist is unnecessary is continued for a certain period of time, the steering torque When the value is smaller, the electric motor can be stopped or decelerated. The invention according to claim 2 is
Steering angular velocity detecting means (11, 3) for detecting the steering angular velocity
0, S1), wherein the motor control means detects that the steering angular velocity detected by the steering angular velocity detection means is equal to or less than a predetermined steering angular velocity threshold value (Vb) and is detected by the current detection means. The electric motor is stopped or the electric motor is stopped under the condition that the state where the motor current value is equal to or less than the current threshold value set by the current threshold value setting means has continued for a predetermined time. (30,
The power steering apparatus according to claim 1, wherein (S10, S14, S16, S17).

According to the present invention, since the condition relating to the steering angular velocity is added, the stop or deceleration control of the electric motor can be more appropriately performed.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing a basic configuration of a power steering device according to one embodiment of the present invention. This power steering device is provided in association with a steering mechanism 1 of a vehicle,
This is for applying a steering assist force to the steering mechanism 1.

The steering mechanism 1 is engaged with a steering wheel 2 operated by a driver, a steering shaft 3 connected to the steering wheel 2, a pinion gear 4 provided at the tip of the steering shaft 3, and a pinion gear 4. And a rack shaft 5 extending in the left-right direction of the vehicle. Tie rods 6 are connected to both ends of the rack shaft 5, respectively.
The tie rods 6 are respectively coupled to knuckle arms 7 that support front left and right wheels FL and FR as steering wheels. The knuckle arm 7 is provided rotatably around the king pin 8.

With this configuration, the steering wheel 2
Is operated to rotate the steering shaft 3, the rotation is converted by the pinion gear 4 and the rack shaft 5 into a linear motion along the left-right direction of the vehicle. This linear motion
The rotation is converted into the rotation of the knuckle arm 7 around the king pin 8, whereby the steering of the front left and right wheels FL and FR is achieved. The steering shaft 3 includes the steering wheel 2
A torsion bar 9 that twists according to the direction and magnitude of the steering torque applied to the torsion bar, and a hydraulic control valve 23 whose opening changes according to the direction and magnitude of the torsion of the torsion bar 9 are incorporated. . The hydraulic control valve 23 is
The steering mechanism 1 is connected to a power cylinder 20 that applies a steering assist force to the steering mechanism 1. The power cylinder 20 includes a piston 21 provided integrally with the rack shaft 5 and a pair of cylinder chambers 20 a and 20 defined by the piston 21.
b, and the cylinder chambers 20a and 20b are connected to a hydraulic control valve 23 via oil supply / return paths 22a and 22b, respectively.

The hydraulic control valve 23 further includes an oil circulation passage 24 passing through a reservoir tank 25 and an oil pump 26.
It is interposed in the middle of. The oil pump 26 is driven by an electric motor 27 and the reservoir tank 25
And pumps the hydraulic oil stored in the hydraulic control valve 23. Excess hydraulic oil is returned from the hydraulic control valve 23 to the reservoir tank 25 via the oil circulation path 24. When the torsion bar 9 is twisted in one direction, the hydraulic control valve 23 controls the oil supply / return path 22.
The hydraulic oil is supplied to one of the cylinder chambers 20a and 20b of the power cylinder 20 via one of the cylinders a and 22b. If the torsion bar 9 is twisted in the other direction, the oil supply / return paths 22a, 22b
The hydraulic oil is supplied to the other one of the cylinder chambers 20a and 20b via the other one. When the torsion bar 9 is hardly twisted, the hydraulic control valve 23
Is in a so-called equilibrium state, and the operating oil is the power cylinder 2
The oil circulates in the oil circulation path 24 without being supplied to the oil circulation path.

When hydraulic oil is supplied to any of the cylinder chambers of the power cylinder 20, the piston 21 moves along the vehicle width direction. As a result, the steering assist force acts on the rack shaft 5. A configuration example related to the hydraulic control valve is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. Sho 59-118577. The electric motor 27 is, for example, a DC motor, and is controlled by an electronic control unit 30 via a drive circuit 28. The drive circuit 28 includes, for example, a bridge circuit of a power transistor, and converts the electric power from the vehicle-mounted battery 40 as a power supply into the electric motor 2 in accordance with a control signal given from the electronic control unit 30.
7

The electronic control unit 30 includes a vehicle-mounted battery 4
0, and a microcomputer that operates by receiving power supply from the CPU 31. The microcomputer includes a CPU 31
And a RAM 3 for providing a work area and the like of the CPU 31
2 and a ROM 3 storing an operation program of the CPU 31
3 and a bus 34 for interconnecting the CPU 31, the RAM 32 and the ROM 33. The CPU 31 detects a generated voltage (hereinafter referred to as “battery voltage”) VB of the vehicle-mounted battery 40 in each control cycle.

The electronic control unit 30 includes a steering angle sensor 1
1 is provided. The steering angle sensor 11 is provided in association with the steering wheel 2. The steering angle of the steering wheel 2 when the ignition key switch is turned on and the engine is started is set to an initial value “0”, and the steering angle sensor 11 Steering angle data having a code corresponding to the relative steering angle and corresponding to the steering direction is output. The CPU 31 obtains a steering angle midpoint, which is a steering angle when the vehicle is in a straight running state, based on the steering angle data, and further, based on the steering angle midpoint and the steering angle data output by the steering angle sensor 11. The absolute steering angle θ corresponding to the directions of the wheels FR and FL is obtained. The steering angle midpoint is detected, for example, by sampling the steering angle data output from the steering angle sensor 11, creating a histogram of the values of the steering angle data, and setting the most frequently used steering angle after collecting a predetermined sampling number of data. This is achieved by obtaining the angle data as the steering angle data of the steering angle midpoint.

The electronic control unit 30 is further provided with current data from the current detection circuit 12 for detecting the current flowing through the electric motor 27. The current data has a value proportional to a current consumption value (motor current) of the electric motor 27. Further, the electronic control unit 30 is provided with vehicle speed data output from the vehicle speed sensor 13. The vehicle speed sensor 13 may directly detect the vehicle speed Vf, or may calculate the vehicle speed Vf based on an output pulse of a wheel speed sensor provided in connection with the wheel. Is also good.

The electronic control unit 30 includes the steering angle sensor 1
1. The driving of the electric motor 27 is controlled based on steering angle data, current data and vehicle speed data given from the current detection circuit 12 and the vehicle speed sensor 13, respectively. FIG.
FIG. 3 is a flowchart for explaining the drive control of the electric motor 27, and FIG. 3 is a characteristic diagram showing the correspondence between the steering angular speed and the motor rotation speed. Based on the steering angle data output from the steering angle sensor 11, the CPU 31 determines a steering angular velocity V, which is a time change rate of the steering angle of the steering wheel 2.
θ and the speed Vf of the vehicle are obtained (step S1). Thereafter, the CPU 31 determines whether the electric motor 27 has stopped (step S2). This determination can be made, for example, using a flag that is set when the electric motor 27 is started and reset when the electric motor 27 is stopped.

If the electric motor 27 is stopped (YES in step S2), the CPU 31 determines whether or not the electric motor 27 should be started by using the determined steering angular velocity Vθ at a predetermined start threshold value. Va (for example, Va = 5 (d
egree / sec)) or not (step S
3). If the steering angular velocity Vθ is less than the activation threshold value Va (NO in step S3), the program returns to step S1. If the steering angular velocity Vθ is equal to or greater than the activation threshold value Va (YES in step S3), the CPU 31 activates the electric motor 27 (step S4). In this case, the CPU 3
1 determines the motor rotation speed R based on the value of the steering angle speed Vθ obtained above.

When determining the motor rotation speed R, the CPU 31 determines whether or not the steering angular speed Vθ is equal to or less than a predetermined first threshold value VT1 (for example, VT1 = 10 (degree / sec)) (step S5). . The steering angular velocity Vθ is equal to the first threshold V
If it is equal to or less than T1 (YES in step S5), the motor rotation speed R becomes equal to a predetermined first rotation speed R1 (eg, R1 = 18
00 (rpm)) to drive the electric motor 27 (step S6). That is, if the steering angular speed Vθ is equal to or greater than the activation threshold value Va and equal to or less than the first threshold value VT1, the electric motor 27 operates independently of the value of the steering angular speed Vθ.
It is driven at a constant first rotation speed R1.

If the steering angular velocity Vθ exceeds the first threshold value VT1 (NO in step S5), the CPU 31
Is a second threshold value VT2 in which the steering angular velocity Vθ is larger than the first threshold value VT1 (for example, VT2 = 600 (degree / sec)
) Is determined (step S7). If the steering angular speed Vθ is less than the second threshold value VT2 (YES in step S7), the CPU 31 drives the electric motor 27 at a motor rotation speed R according to the value of the steering angular speed Vθ (step S8). That is, in a region where the steering angular speed Vθ is larger than the first threshold value VT1 and smaller than the second threshold value VT2, the CPU 31 determines that the motor rotation speed R is equal to the first rotation speed R1 with respect to the steering angular speed Vθ. The motor rotation speed R is determined so as to change substantially linearly with the second rotation speed R2 (R2> R1).

If the steering angular speed Vθ is equal to or higher than the second threshold value VT2 (NO in step S7), the CPU 31 determines that the motor rotation speed R is equal to or smaller than the predetermined second rotation speed R2 (for example, R2).
The electric motor 27 is driven so that 2 = 6000 (rpm)) (step S9). That is, when the steering angular velocity Vθ is the second
If the threshold value VT2 or more, the electric motor 27 is driven at a constant second rotation speed R2 regardless of the value of the steering angular speed Vθ. As shown in FIG. 3, the second threshold V
T2 is variably set according to the vehicle speed range. That is, the second threshold value VT2 is set to a larger value as the vehicle speed Vf is larger. As a result, the motor rotation speed R is set to be smaller as the vehicle speed Vf is higher, and the steering assist force is smaller. Thus, the vehicle speed V
Vehicle speed sensitive control for generating an appropriate steering assist force according to f is performed.

If it is determined in step S2 that the electric motor 27 is being driven, the CPU 31 sets the steering angular velocity Vθ to a predetermined stop threshold value (second predetermined value) Vb (for example, Vb = 8 (degree / sec). )) It is determined whether or not the following is true (step S10). The steering angular velocity Vθ is equal to the stop threshold V
If it exceeds b (NO in step S10), the program proceeds to step S5, where the CPU 31 determines the motor rotation speed R based on the obtained value of the steering angular speed Vθ, and determines the determined motor rotation speed R. Electric motor 27 at R
Drive.

If the steering angular velocity Vθ is equal to or smaller than the stop threshold Vb (steering angle threshold) (YES in step S10), C
The PU 31 obtains the motor current value Im based on the current data output from the current detection circuit 12 (step S1).
1). Further, the CPU 31 determines that the latest battery voltage VB
Is detected (step S12), and a motor stop determination current value Istop (current threshold value) is obtained based on the detected battery voltage VB and the vehicle speed Vf detected by the vehicle speed sensor 13 (step S13). And CPU
In step S1, it is determined whether the obtained motor current value Im is equal to or smaller than the motor stop determination current value Istop.
4).

The motor stop determination current value Istop is an upper limit value of the motor current when steering assist is not required. This motor stop determination current value Istop is obtained by adding a correction based on the battery voltage VB and the vehicle speed Vf to the motor stop current initial value Istop (0). The motor stop current initial value Istop (0) is determined by a motor stop current initial value calculation process described later. If the motor current value Im has a value equal to or smaller than the motor stop determination current value Istop (YES in step S13), the CPU 31 further sets
It is checked whether the absolute steering angle θ detected as described above is a value within the stoppable range Δθ near the steering angle midpoint (for example, a range of about ± 3 degrees around the steering angle midpoint) ( Step S15). When this determination is affirmed, the CPU 31
The steering angular velocity Vθ is equal to or less than the stop threshold value Vb, the motor current value Im is equal to or less than the motor stop determination current value Istop,
Further, it is determined whether or not the state in which the absolute steering angle θ is a value within the range of the stoppable range Δθ has continued for a fixed time (for example, 1 to 3 seconds) (step S16). If this determination is affirmative (YES in step S16), it can be considered that the steering wheel 2 is hardly steered, so the CPU 31 stops the electric motor 27 (step S17). On the other hand, the above steps S10, S14 to S
If any one of the judgments of 16 is denied, the CPU 31
The process from step S5 is performed to determine the motor rotation speed R, and the electric motor 27 is driven at that rotation speed.

FIG. 4 shows a motor stop current initial value Istop (0).
6 is a flowchart for explaining the calculation processing of FIG. C
The PU 31 constantly monitors the motor current value Im using the fact that the motor current value Im changes according to the steering torque T applied to the steering wheel 2 (step U).
1). Based on the motor current value Im, the CPU 31
Calculates a no-load current value I0 which is a motor current value when the electric motor 27 is in a no-load state (step U
2). Then, a value I0 + dI obtained by adding a predetermined value dI predetermined according to the specification of the vehicle to the obtained no-load current value I0 is set as the motor stop current initial value Istop (0).

FIG. 5 shows the relationship between the steering torque T and the motor current value Im.
FIG. 6 is a characteristic diagram showing a correspondence relationship with the above. Steering torque T on horizontal axis
And the vertical axis indicates the motor current value Im. When the steering torque T is around 0, the motor current value Im becomes
It can be represented by a curve having the point 0 as the vertex. When the steering torque T is 0, the electric motor 27 is in a no-load state, and the minimum value of the motor current value Im corresponds to the no-load current value I0. On the other hand, the range of the torque that does not require the application of the steering assist force to the steering wheel 2 is determined by the specifications of the vehicle. When this torque range is a range sandwiched by torque threshold values T1 and -T1 around 0,
The difference between the motor current value corresponding to these torque threshold values T1 and -T1 and the no-load current value I0 is obtained in advance and set as the predetermined value dI. And the no-load current value I
A value I0 + dI (= Istop obtained by adding a predetermined value dI to 0)
(0)) The following range can be determined as the range in which the steering wheel 2 is not steered. The predetermined value d
I is obtained in advance for each vehicle type and stored in the ROM 33, for example.

The no-load current value I0 fluctuates mainly depending on the temperature of the hydraulic oil. That is, for example, when the temperature of the hydraulic oil is low, the viscosity of the hydraulic oil is high, so that the load on the electric motor 27 is larger than when the temperature of the hydraulic oil is high. Therefore, the motor current value Im takes a large value when the temperature of the hydraulic oil is low. That is, Im-T in FIG.
The curve slides upward, and the no-load current value I0 also increases. Therefore, in this embodiment, the no-load current value I0 is obtained by calculation, and the obtained no-load current value I0 is stored in the ROM.
A value I0 + d obtained by adding the predetermined value dI stored in 33
I is set as the motor stop current initial value Istop (0).

The calculation of the no-load current value I0 is achieved, for example, by obtaining the most frequent current value among the sampled motor current values Im. More specifically, CP
U31 samples the current data output from the current detection circuit 12 for a certain period of time (for example, 10 (min) to 1 (hour)), provided that the motor rotation speed R is constant. The motor current value Im obtained based on the current data obtained by this sampling has a normal distribution. In this case, since the motor current value Im when the steering torque T is 0 becomes the most frequent current value, the most frequent current value is obtained as the no-load current value I0.

In addition to the above calculation, for example, on the condition that the motor rotation speed R is constant, a minimum value is obtained from the motor current value Im sampled for a certain time or a certain number of times. The minimum value may be the no-load current value I0. FIG. 6 is a diagram for explaining the calculation process of the motor stop determination current value Istop in step S13 of FIG. FIG. 6A shows the relationship between the battery voltage VB and the motor stop determination current value Istop, and FIG. 6B shows the vehicle speed Vf and the motor stop determination current value Istop.
The relationship with stop is shown. More specifically, the motor stop determination current value Istop is a motor stop current initial value Istop.
(0), which is determined as a function of the battery voltage VB and the vehicle speed Vf.

As shown in FIG. 6A, the motor stop determination current value Istop is set smaller as the battery voltage VB is higher, and is set larger as the battery voltage VB is lower. The electric motor 27 is feedback-controlled so that its rotation speed becomes equal to the set rotation speed R. When the battery voltage VB decreases, the power supplied to the electric motor 27 becomes insufficient, and the electronic control unit 30 attempts to compensate for the shortage by increasing the motor current. As a result, even in a no-load state where no torque is applied to the steering wheel 2, the motor current value Im takes a large value.

Therefore, in this embodiment, when the battery voltage VB decreases, the motor stop determination current value Istop
Is set to be large. Thus, in the no-load state, a positive determination is made in step S14 of FIG. 2 even if the motor current value Im takes a large value, and appropriate stop control of the electric motor 27 is performed. I can do it. As a result, wasteful power consumption can be reduced, and the energy saving of the power steering device can be improved.

On the other hand, as shown in FIG. 6B, as the vehicle speed Vf increases, the motor stop determination current value Istop increases. When driving at high speeds, steering assistance is not so necessary. Therefore, in this embodiment, the vehicle speed Vf
Is large, the motor stop determination current value Istop is set to be large, thereby stopping the electric motor 27 as much as possible to improve energy saving. As described above, according to the first embodiment, the battery voltage V
Since the motor stop determination current value Istop is variably set in accordance with the variation of B, the stop control of the electric motor 27 can be appropriately performed. Thereby, useless energy consumption can be suppressed.

The steering angular velocity Vθ is equal to the first threshold value VT1.
In the following regions, the steering angular speed Vθ and the motor rotation speed R have so-called hysteresis characteristics. That is, the threshold value Va for starting the motor is smaller than the threshold value Vb for stopping the motor. Thus, the steering assist force can be quickly generated when the steering is started, and the steering assist can be quickly stopped at the end of the steering. Thereby, the improvement of the steering feeling and the improvement of the energy saving can be achieved at the same time.

FIG. 7 is a view for explaining a second embodiment of the present invention, in which a steering angular velocity Vθ and a motor rotational speed R are shown.
Is shown. In the description of FIG. 7, the above-mentioned FIGS. 1 and 2 will be referred to again. In this embodiment, in the no-load state, the rotation speed R of the electric motor 27 is reduced to the idle rotation speed Ri (Ri <R1) instead of stopping the electric motor 27. That is, steps S10, S14 to S16 in FIG.
When all the conditions are satisfied, instead of stopping the electric motor 27, the rotation speed is changed to the idle rotation speed Ri.
Slow down.

According to this configuration, when the steering assist is required, the rotation speed of the electric motor 27 can be quickly increased to generate the required hydraulic pressure, and therefore, the response of the steering assist is excellent. There are advantages. By adopting this configuration, when steering assist is not required, energy can be saved by rotation at the idle rotation speed Ri, and when steering assist is needed, a quick start-up can be realized. Can be improved.

In step S13 of FIG. 2, the motor stop determination current value Istop is appropriately variably set in accordance with the fluctuation of the battery voltage VB. Instead, the rotation of the electric motor 27 can be reduced to the idle rotation speed Ri. Although the two embodiments of the present invention have been described, the present invention can be implemented in other embodiments. For example, in the above-described embodiment, the condition that the absolute steering angle θ is a value near the steering angle midpoint is a necessary condition for stopping the electric motor 27 or decelerating to the idling rotation speed Ri, but this condition is omitted. May be. In addition, it is possible to make various design changes within the technical scope described in the claims.

[Brief description of the drawings]

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

FIG. 2 is a flowchart for explaining motor drive control.

FIG. 3 is a characteristic diagram showing an example of setting a motor rotation speed with respect to a steering angular speed.

FIG. 4 is a flowchart illustrating a motor stop current initial value setting process.

FIG. 5 is a diagram for explaining a motor stop current initial value setting process.

FIG. 6 is a diagram for explaining a calculation process of a motor stop determination current value.

FIG. 7 is a characteristic diagram illustrating a relationship between a steering angular speed and a motor rotation speed according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 steering mechanism 2 steering wheel 11 steering angle sensor 12 current detection circuit 13 vehicle speed sensor 20 power cylinder 23 hydraulic control valve 26 oil pump 27 electric motor 28 drive circuit 30 electronic control unit 40 in-vehicle battery

Claims (2)

[Claims] 1. A power steering device for generating a steering assist force by a hydraulic pressure generated by a pump driven by an electric motor, a power supply voltage detecting means for detecting a voltage of a power supply for supplying electric power to the electric motor, and the electric motor Current detection means for detecting a value of a motor current flowing through the motor, and a motor current value when stopping or decelerating the electric motor to a predetermined idle speed based on a power supply voltage detected by the power supply voltage detection means. Current threshold value setting means for variably setting a current threshold value which is a threshold value with respect to the motor; a motor current value detected by the current detection means is equal to or less than a current threshold value set by the current threshold value setting means The electric motor is stopped or the electric motor is stopped on condition that the state of And a motor control means for reducing the speed of the motor to the idle rotation speed. 2. The vehicle according to claim 1, further comprising a steering angular velocity detecting means for detecting a steering angular velocity, wherein the motor control means includes a steering angular velocity detected by the steering angular velocity detecting means that is equal to or less than a predetermined steering angular velocity threshold value, And stopping the electric motor on condition that a state in which the motor current value detected by the current detecting means is equal to or less than the current threshold value set by the current threshold value setting means has continued for a predetermined time. 2. The power steering apparatus according to claim 1, wherein the electric motor is decelerated to the idle rotation speed.