JP2002264833A - Power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering system capable of appropriately performing a failure diagnosis of a sensor or the like. SOLUTION: An abnormality detection part 44 performs an abnormality detection process based on an output of the sensor. A normal control part 41 variably sets a target rotational speed of an electric motor 27 based on the output of the sensor. A fail control part 42 sets a fixed target rotational speed. A selecting part 43 selects and outputs the target rotational speed from the normal control part 41 when no abnormality is detected, and selects and outputs the target rotational speed from the fail control part 42 when the abnormality is detected. An abnormality detection stop part 45 watches a state of a battery voltage, an engine rotation signal, an alternator signal and an ignition switch. If a state disabling appropriate abnormality detection of the abnormality detection part 44 is detected, the abnormality detection stop part 45 prohibits the abnormality detection of the abnormality detection part 44.

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.

The steering shaft has a torsion bar that twists according to the direction and magnitude of the steering torque applied to the steering wheel, and a hydraulic control that changes the opening according to the direction and magnitude of the torsion of the torsion bar. A valve is incorporated. The hydraulic control valve is provided in a hydraulic system between the oil pump and the power cylinder, and generates a steering assist force from the power cylinder according to the steering torque. The drive control of the electric motor is, for example,
This is performed 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 speed is low, the operation of the steering wheel is slight, so that the electric motor is reduced to the standby rotation speed which is the lower limit of the target rotation speed. On the other hand, if the steering angular speed is high, it is considered that the steering wheel is being operated largely, and the electric motor is driven according to the steering angular speed at that time, and a steering assist force is generated.

Further, the drive control of the electric motor may be performed based on vehicle speed information. That is, based on the output signal from the vehicle speed sensor, the target rotation speed of the electric motor is set to be large when the vehicle is traveling at a low speed or when the vehicle is stopped, and the target rotation speed of the electric motor is set to be small when the vehicle is traveling at a high speed. Thereby, an appropriate steering assist force according to the vehicle speed can be given to the steering mechanism. If a failure occurs in the steering angle sensor or the vehicle speed sensor, the drive control of the electric motor cannot be performed properly, so that appropriate steering assistance cannot be performed. Therefore, the power steering apparatus as described above is provided with a failure diagnosis function for detecting a failure of sensors such as a steering angle sensor and a vehicle speed sensor. That is, the failure diagnosis of the sensors is performed based on the output signals of the sensors. Then, when a failure of the sensors is detected, the target rotation speed is set to an intermediate fixed value that can provide a somewhat good steering assist in both low-speed running and high-speed running. In this way, a fail-safe function against failures of sensors is realized.

[0005]

However, since the steering angle sensor and the vehicle speed sensor operate by receiving power supply from the vehicle-mounted battery, the output signals of such sensors are affected by the output voltage fluctuation of the vehicle-mounted battery. receive. Therefore, even when there is no failure in the sensors, an erroneous diagnosis that a failure has occurred in the sensors may be made depending on the output voltage of the vehicle-mounted battery. As a result, the target rotation speed of the electric motor is fixed at a constant value, which leads to deterioration of the steering feeling.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power steering device capable of properly detecting an abnormality and thereby improving a steering feeling.

[0007]

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). A power steering device for generating the power steering device, wherein abnormality detecting means (4) for detecting abnormality of the device.
4) and normal control means (41) for controlling the electric motor when the abnormality detection means does not detect an abnormality.
A fail time control means (42) for controlling the electric motor when the abnormality detection means has detected an abnormality;
Means for prohibiting control of the electric motor by the failure control means when predetermined conditions affecting the abnormality detection operation by the abnormality detection means are satisfied. Device. Note that the alphanumeric characters in parentheses represent corresponding components and the like in embodiments described later. Hereinafter, the same applies in this section.

According to this configuration, when the predetermined condition affecting the abnormality detecting operation by the abnormality detecting means is satisfied, the control of the electric motor by the fail time control means is prohibited, and the electric control by the normal time control means is performed. The motor will be controlled. Therefore, in a situation where there is a high probability that the abnormality detecting means will erroneously detect an abnormality, control is not transferred from the normal control means to the fail control means. Thus, it is possible to prevent the steering feeling from being deteriorated due to the erroneous detection of the abnormality.

According to a second aspect of the present invention, there is provided a control transition control for gradually changing the rotation speed of the electric motor when the control of the electric motor is switched between the normal control means and the failure control means. 2. The power steering apparatus according to claim 1, further comprising means (41a, 42a). According to this configuration, when the control is shifted between the control by the normal time control means and the control by the fail time control means, the rotation speed of the electric motor gradually changes. Therefore, it is possible to prevent the steering feeling from being deteriorated.

The means for prohibiting the control of the electric motor by the fail time control means is means (45) for indirectly prohibiting the control of the electric motor by the fail time control means by prohibiting the abnormality detection by the abnormality detection means. There may be. The normal control means may control the electric motor based on output signals of sensors (such as a steering angle sensor and a vehicle speed sensor). In this case, the abnormality detecting means may detect an abnormality of the sensors.

For example, the sensors may be operated by receiving power supply from a power source (for example, a vehicle battery). In this case, it is preferable that the predetermined condition includes detection of a power supply voltage fluctuation of a predetermined value or more, or detection of a condition causing a power supply voltage fluctuation of a predetermined value or more. The condition that causes the power supply voltage fluctuation to be equal to or more than the predetermined value is that an engine speed of a vehicle equipped with the power steering device is equal to or less than a predetermined value;
For example, the alternator signal may be equal to or less than a predetermined value, or may be a period within a predetermined time after the ignition is turned on.

[0012]

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 includes 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. It has a rack gear portion 5a that meshes with the rack shaft 5 and extends in the left-right direction of the vehicle. Rack shaft 5
Are connected to knuckle arms 7 supporting front left and right wheels FL and FR as steering wheels, respectively. 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 that passes 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. In the reservoir tank 25, an oil temperature sensor 14 for detecting the temperature of the hydraulic oil is arranged.

When the torsion bar 9 is twisted in one direction, the hydraulic control valve 23 is connected to one of the cylinder chambers 20a, 20b of the power cylinder 20 via one of the oil supply / return paths 22a, 22b. Supply hydraulic oil to one of the two. When the torsion bar 9 is twisted in the other direction, the oil supply / return path 22a,
22b via the other one of the cylinder chambers 20a, 20b.
Supply hydraulic oil to the other of the two. When the torsion bar 9 is hardly twisted, the hydraulic control valve 23 is in a so-called equilibrium state, and the hydraulic oil circulates in the oil circulation path 24 without being supplied to the power cylinder 20.

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 23 is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. S59-118577. 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, a ROM 33 storing an operation program of the CPU 31, control data, and the like;
And a bus 34 for interconnecting the ROM 33. The electronic control unit 30 is provided with steering angle data output from the steering angle sensor 11. 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 calculates a steering angular velocity, which is a time differential value, based on the steering angle data.

The electronic control unit 30 further includes a current detection signal from the current detection circuit 12 for detecting a current flowing through the electric motor 27, a rotation speed signal from the rotation sensor 15 for detecting the rotation speed of the electric motor 27, Is given. Further, the electronic control unit 30 is provided with a vehicle speed signal output from the vehicle speed sensor 13. The vehicle speed sensor 13 may directly detect the vehicle speed, or may calculate the vehicle speed based on an output pulse of a wheel speed sensor provided in connection with the wheel.

The electronic control unit 30 includes a 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. In addition to the above, the electronic control unit 30 receives an engine rotation signal indicating the number of revolutions of the engine, an alternator signal indicating the output level of the alternator, and a signal from the ignition switch 16.

FIG. 2 is a block diagram for explaining a functional configuration of the electronic control unit 30. As shown in FIG. The electronic control unit 30 includes a normal-time control unit 41, a failure-time control unit 42, an abnormality detection unit 44 for detecting an abnormality of a sensor, and the like, as functional parts realized by the CPU 31 executing software processing. An abnormality detection stop unit 45 for stopping the abnormality detection operation by 44, and a switching unit 43 for outputting the target rotation speed output by the normal control unit 41 or the failure control unit 42 based on the output of the abnormality detection unit 44. Have.

The normal time control unit 41 controls the electric motor 2 based on the steering angle signal from the steering angle sensor 11, the vehicle speed signal from the vehicle speed sensor 13, and the oil temperature signal from the oil temperature sensor 14.
7 is set and output. FIG. 3 is a characteristic diagram showing the correspondence between the steering angular speed calculated based on the steering angle signal and the target rotation speed of the electric motor 27. The target rotation speed R monotonically increases between a first threshold value VT1 and a second threshold value VT2 defined for a steering angular speed Vθ (corresponding to a steering speed) (in this embodiment, increases linearly). ) Is determined between the lower limit value R1 and the upper limit value R2. The lower limit value R1 of the target rotation speed R in this monotonically increasing section is set as the standby rotation speed, and the first threshold value V
For a steering angular speed less than T1, the electric motor 27 is rotationally driven at the standby rotation speed R1.

The CPU 31 variably sets the inclination of the target rotational speed R with respect to the steering angular speed Vθ based on the vehicle speed, as shown in FIG. That is, the second threshold value VT2 is variably set according to the vehicle speed range. More specifically, the second threshold value VT2 is set to a larger value as the vehicle speed increases. Accordingly, the target rotation speed R is set to be smaller as the vehicle speed is higher, and the steering assist force is reduced.
Thus, the vehicle speed responsive control for generating an appropriate steering assist force according to the vehicle speed is performed.

The normal time control section 41 sets the target rotational speed by setting the target rotational speed set in accordance with the characteristic diagram of FIG. 3 as a "reference value", and applying a correction represented by the following equation to the reference value. . Target rotation speed = reference value × K (T) where K (T) is a coefficient determined according to temperature T. FIG. 4 shows the relationship between the temperature of the hydraulic oil detected by the oil temperature sensor 14 and the coefficient K (T). The coefficient K (T) is
Within a certain temperature range, the temperature is set to increase monotonically from the lower limit to the upper limit as the temperature increases.

Since the viscosity of the hydraulic oil changes according to the temperature of the hydraulic oil, the characteristics of the hydraulic control valve 23 change accordingly. Therefore, the steering assist force applied to the steering wheel 1 varies depending on the temperature of the hydraulic oil. Therefore, in order to compensate for the fluctuation of the steering assist force due to the temperature change of the hydraulic oil, the coefficient K shown in FIG.
According to (T), the target rotation speed is variably set according to the temperature of the hydraulic oil. FIG. 2 is referred to again. Abnormality detector 44
Monitors the output signals of the steering angle sensor 11, the vehicle speed sensor 13, and the oil temperature sensor 14, and determines that an abnormality has occurred in the sensor, for example, when those output signals are below respective predetermined levels. Then, a signal indicating occurrence of an abnormality is provided to switching section 43. The switching unit 43 selects and outputs the target rotation speed set by the normal control unit 41 when the abnormality detection unit 44 does not detect any abnormality. On the other hand, when the abnormality detection unit 44 detects an abnormality, the failure control unit 42 selects and outputs the target rotation speed output.

The failure control unit 42 outputs a constant target rotation speed independent of the steering angular speed, the vehicle speed and the oil temperature. The constant target rotation speed is determined in consideration of an intermediate value of the steering angular speed and an intermediate value of the vehicle speed, and in any case, an allowable steering assist force is applied to the steering mechanism 1. Is set to be able to. The target rotation speed output from the switching unit 43 is provided to the deviation calculation unit 46. The deviation calculating unit 46 detects the electric motor 2 detected by the rotation sensor 15 from the target rotation speed.
By subtracting the actual rotation speed in Step 7, the deviation of the actual rotation speed from the target rotation speed is obtained. The deviation found is
It is provided to a PI (proportional / integral) controller 47 and is used for PI control calculation. As a result, the PI control unit 47 calculates and outputs a duty ratio according to the deviation. This duty ratio is given to the PWM pulse generator 48. The PWM pulse generator 48 generates a PWM pulse having the duty ratio given by the PI controller 47 and supplies the PWM pulse to the drive circuit 28 for driving the electric motor 27.

In this way, by driving the electric motor 27 with a PWM pulse having a duty ratio corresponding to the deviation between the target rotation speed and the actual rotation speed, the electric motor 27 is feedback-controlled to rotate at the target rotation speed. ,
An appropriate steering assist force is applied to the steering mechanism 1. The abnormality detection stop unit 45 outputs a signal for stopping the abnormality detection processing by the abnormality detection unit 44 when a predetermined condition that the abnormality detection operation (failure diagnosis processing) in the abnormality detection unit 44 is not properly performed is satisfied. Generate. as a result,
Since the switching unit 43 does not select the target rotation speed from the fail-time control unit 42, as a result, the control of the electric motor 27 by the fail-time control unit 42 is prohibited.

The abnormality detection stop unit 45 receives a voltage generated by the battery 40 (battery voltage), an engine rotation signal, an alternator signal, and a signal from the ignition switch 16. When any of the following conditions is satisfied, the abnormality detection stopping unit 45
To the abnormality detection stop signal. When the battery voltage VB reaches a predetermined threshold voltage (for example,
9V) or less. The engine speed indicated by the engine speed signal is equal to or lower than a predetermined threshold speed (for example, 500 rpm).

The alternator signal level is below a predetermined threshold level. This is before a fixed time (for example, 2 seconds) has elapsed since the ignition switch 16 was turned on. The above conditions are the steering angle sensor 11, the vehicle speed sensor 13
This is a condition that the output signals of these sensors output abnormal values even if no abnormality occurs in the oil temperature sensor 14.

That is, the condition is that the voltage of the battery 40 supplying the power supply voltage to the steering angle sensor 11, the vehicle speed sensor 13 and the oil temperature sensor 14 fluctuates. Output signal indicates an abnormal value. The above conditions are conditions under which the battery voltage is likely to decrease due to the low engine speed. The above condition is a condition in which the alternator signal level is low and the battery voltage is likely to be temporarily reduced.

The above condition is a condition focusing on a point that the battery voltage drop immediately after the ignition is turned on is remarkable.
This is a condition under which the output signals of the sensors 11, 13, and 14 are abnormally reduced. As described above, in this embodiment, even if there is no failure in the sensors, when the condition of the output of these sensors indicates an abnormal value, the abnormality detecting operation by the abnormality detecting unit 44 is stopped and the normal state is detected. The control unit 41 controls the electric motor 27. by this,
In a situation where there is a high probability that the output signals of these sensors indicate an abnormal value even though the operation of the sensors is normal, a failure is not diagnosed, so that erroneous detection of an abnormality of the sensors can be prevented. As a result, the transition from the control by the normal control unit 41 to the control by the failure control unit 42 is not performed due to the erroneous detection of the abnormality, and the electric motor 27 can be more appropriately controlled. . As a result, an appropriate target rotation speed can be set according to the steering angular speed and the vehicle speed, so that a good steering feeling can be realized.

When the abnormality detecting unit 44 detects an abnormality of the sensors, the control of the electric motor 27 based on the target rotation speed output by the normal control unit 41 is changed to the target rotation speed output by the failure control unit 42. The control is switched to the control of the electric motor 27 based on this. Further, when the abnormality detection unit 44 returns from a failure state in which the abnormality of the sensors is detected to a normal state without detecting the abnormality, control from the failure control unit 42 to control by the normal control unit 41 is performed. Will be migrated.

When the control is switched between the control by the normal control unit 41 and the control by the fail control unit 42, the target rotation speed set by the normal control unit 41 and the constant target rotation by the fail control unit 42 are set. Since the speed does not always match, the target rotation speed generally changes suddenly. As a result, the steering assist force applied to the steering mechanism 1 changes abruptly, so that the driver feels a sense of discomfort via the steering wheel 2.

Therefore, in this embodiment, the normal-time control unit 41 and the fail-time control unit 42 monitor the target rotational speeds each other, so that a sudden change in the target rotational speed does not occur. That is, the normal control unit 41 and the fail control unit 42 are controlled by the control transfer control unit 41, respectively.
a, 42a. Control transfer control units 41a, 42
“a” gradually changes the target rotation speed when the control is switched between the normal control unit 41 and the fail control unit 42. That is, when the control transition control unit 41a shifts from the control by the failure control unit 42 to the control by the normal control unit 41, the control transition control unit 41a changes the constant target rotation speed in the failure control unit 42 by the normal control unit 41. The target rotation speed is gradually changed to the set target rotation speed. In addition, the control transition control unit 42a includes the normal control unit 4
When the control by the control unit 1 shifts to the control by the failure control unit 42, the target rotation speed variably set by the normal control unit 41 gradually changes to the constant target rotation speed in the failure control unit 42. Such a target rotation speed is given to the switching unit 43.

In this way, it is possible to prevent a sudden change in the steering assist force due to the switching of the control, so that the steering feeling can be improved. Instead of gradually changing the target rotation speed, the vehicle speed or the steering angular speed used for controlling the motor may be gradually changed. Although not shown in FIG. 2, when the oil temperature sensor 14 detects that the temperature of the hydraulic oil is extremely low (for example, −40 ° C. or less), a low level for driving the electric motor 27 at the maximum output is used. Oil temperature control may be performed. In this case, it is preferable to gradually change the target rotation speed when shifting from the low oil temperature control to the control by the normal control unit 41.

On the other hand, in the PI control section 47, the proportional gain P
In addition, the duty ratio is set while the integral gain I is updated every fixed control cycle. In this case, the proportional gain P (n) in the current cycle (n is a number representing the current control cycle) is given by the following equation (1). P (n) = Pi × (actual rotation speed−target rotation speed) (1) where Pi is a proportional constant. Further, the integral gain I (n) in this cycle is given by the following equation (2).

I (n) = Ki × (actual rotation speed−target rotation speed) + I (n−1) (2) where Ki is an integration constant. And the PI control unit 4
7 calculates the duty ratio according to the following equation (3). Duty ratio = P (n) + I (n) (3) The proportional constant Pi and the integral constant Ki for setting the proportional gain P and the integral gain I are set to constant values, and the actual rotational speed and the target rotational speed are set. It has been found that if feedback control (PI control) is performed based only on the deviation from the above, problems arise in terms of responsiveness, stability, and noise. Therefore, in this embodiment, a constant setting unit 49 for variably setting the proportional constant Pi and the integral constant Ki based on environmental variables is provided. The constant setting unit 49 variably sets the proportional constant Pi and the integral constant Ki based on the battery voltage, the motor current detected by the current detection circuit 12, and the oil temperature detected by the oil temperature sensor 14. In addition, the constant setting unit 49 has a function of variably setting the proportional constant Pi and the integral constant Ki based on the vehicle speed detected by the vehicle speed sensor 13 and the steering angular speed calculated based on the output of the steering angle sensor 11. You may have.

The variable setting of the proportional constant Pi and the integral constant Ki based on the battery voltage is performed to stably drive the electric motor 27 by compensating for the influence of the fluctuation of the battery voltage. Also, a proportional constant Pi based on motor current or oil temperature
The variable setting of the integration constant Ki is performed to compensate for the magnitude of the load on the electric motor 27 and to stably drive the electric motor 27. The variable setting of the proportional constant Pi and the integral constant Ki based on the vehicle speed and / or the steering angular speed is performed for improving the steering feeling.

Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms.
For example, in the above-described embodiment, when any one of the conditions (1) to (4) is satisfied, the abnormality detection by the abnormality detecting unit 44 is stopped. Alternatively, the abnormality detection operation of the abnormality detection unit 44 may be stopped based on the simultaneous establishment of any plural conditions among the above conditions 1 to 6. Further, another condition may be provided in addition to the above conditions, and the operation of the abnormality detection unit 44 may be stopped when this condition is satisfied.

In the above embodiment, the abnormality detecting unit 4
By stopping the abnormality detection operation by the control unit 4, the drive control of the electric motor 27 by the failure time control unit 42 is prohibited. Alternatively, the switching unit 43 may select the target rotation speed from the normal control unit 41 when the abnormality detection stop unit 45 detects that the predetermined condition is satisfied.
In the above-described embodiment, the proportional constant Pi and the integral constant Ki in the PI control unit 47 are variably set based on the environmental variables (battery voltage, motor current, and oil temperature). And the integration constant Ki
May be fixed values, and the duty ratio calculated by the above equation (3) may be corrected based on environmental variables.

In the above embodiment, the oil temperature sensor 14
Is used to detect the temperature of the hydraulic oil.
In the case where an oil cooling structure using hydraulic oil for cooling the drive element for driving the drive 7 is employed, the temperature of the hydraulic oil is detected indirectly by detecting the temperature of the drive element. You may. The load of the electric motor 27 may be estimated by integrating the motor current detected by the current detection circuit 12 over a certain period of time, and the temperature of the hydraulic oil may be estimated based on the load of the electric motor. That is, since the magnitude of the load on the electric motor 27 depends on the viscosity of the hydraulic oil, the temperature of the hydraulic oil can be estimated based on the correspondence between the viscosity of the hydraulic oil and the temperature of the hydraulic oil.

In addition, various design changes can be made within the scope of the matters 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 an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a functional configuration of an electronic control unit.

FIG. 3 is a characteristic diagram showing a correspondence relationship between a steering angular speed and a target rotation speed of an electric motor.

FIG. 4 is a diagram for explaining setting of a target rotation speed based on the temperature of hydraulic oil.

[Explanation of symbols]

 Reference Signs List 1 steering mechanism 2 steering wheel 11 steering angle sensor 12 current detection circuit 13 vehicle speed sensor 14 oil temperature sensor 15 rotation sensor 16 ignition switch 20 power cylinder 23 hydraulic control valve 26 oil pump 27 electric motor 28 drive circuit 30 electronic control unit 40 in-vehicle battery 41 Normal control unit 41a Control transition control unit 42 Failure control unit 42a Control transition control unit 43 Switching unit 44 Abnormality detection unit 45 Abnormality detection stop unit 46 Deviation calculation unit 47 PI control unit 48 PWM pulse generation unit 49 Constant setting unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B62D 113: 00 B62D 113: 00 117: 00 117: 00 F term (Reference) 3D032 CC28 CC33 CC38 DA03 DA09 DA23 DA24 DA53 DA64 DD02 DD10 DD17 EA01 EC03 EC23 GG01 3D033 EB02 EB04 EB06 JB18

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, wherein abnormality detection means for detecting an abnormality of the device, and the abnormality detection means detects an abnormality. A normal-time control unit that controls the electric motor when the abnormality is not detected; a fail-time control unit that controls the electric motor when the abnormality detection unit detects an abnormality; and an abnormality detection operation performed by the abnormality detection unit. Means for prohibiting control of the electric motor by the fail-time control means when a predetermined condition is satisfied. 2. The control system according to claim 1, further comprising control transition control means for gradually changing the rotation speed of the electric motor when the control of the electric motor is switched between the normal control means and the failure control means. The power steering device according to claim 1, wherein: