JP4678467B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering device that applies a steering assist force to a steering mechanism by hydraulic pressure generated by a pump driven by an electric motor.
[0002]
[Prior art]
There is known a power steering device that assists the operation of a steering wheel by supplying hydraulic oil from an oil pump to a power cylinder coupled to a steering mechanism. The oil pump is driven by an electric motor, and a steering assist force corresponding to the rotation speed is generated from the power cylinder.
The steering shaft includes a torsion bar that twists according to the direction and magnitude of the steering torque applied to the steering wheel, and a hydraulic control valve whose opening degree changes according to the direction and magnitude of the twist of the torsion bar. It has been incorporated. The hydraulic control valve is interposed in a hydraulic system between the oil pump and the power cylinder, and generates a steering assist force corresponding to the steering torque from the power cylinder.
[0003]
The drive control of the electric motor is performed based on the steering angular speed of the steering wheel, for example. That is, the steering angular speed is obtained based on the output of the steering angle sensor provided in association with the steering wheel, and the target rotational speed of the electric motor is set based on the steering angular speed. A voltage is supplied to the electric motor so that this target rotational speed is achieved. More specifically, when the rudder angular speed is small, the steering wheel is slightly operated, so the electric motor is decelerated to the standby rotational speed that is the lower limit value of the target rotational speed. On the other hand, if the rudder angular velocity is large, it is considered that the steering wheel is largely operated, the electric motor is driven according to the rudder angular velocity at that time, and steering assist force is generated.
[0004]
An electronic control unit for controlling the power steering apparatus executes an abnormality monitoring process for detecting a failure of a sensor line or the like. When any abnormality (failure) is detected by the abnormality monitoring process, the electronic control unit gradually decreases the rotation speed of the electric motor and stops the electric motor by the fail-safe process.
[0005]
[Problems to be solved by the invention]
However, in the current power steering apparatus, the rotational speed of the electric motor is gradually decreased in response to the occurrence of an abnormality, and the electric motor is led to a stopped state even if steering is not performed. .
That is, for example, the rotational speed of the electric motor decreases while the vehicle is traveling on a straight path and the steering wheel is held at the steering angle midpoint. Therefore, the driver is less likely to notice an abnormality in the power steering device, and the steering resistance increases rapidly during the next steering, and the driver feels uncomfortable.
[0006]
Accordingly, an object of the present invention is to provide a power steering device that solves the technical problems described above, allows a driver to reliably recognize an abnormality in the power steering device, and eliminates the uncomfortable steering caused by a sudden increase in steering resistance. Is to provide.
[0007]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, an invention according to claim 1 is a power steering device for generating a steering assist force by a hydraulic pressure generated by a pump (26) driven by an electric motor (27), and for steering a vehicle. Steering angular velocity detecting means (11, 31, S4) for detecting the steering angular speed, which is the steering speed by the operation member (2), and abnormality detecting means (31, S1) for detecting abnormality of the power steering device Based on the output of the steering angular velocity detecting means when the steering detecting means (11, 31, S9, S21, S22) for detecting the presence or absence of steering by the operation member and the abnormality detecting means detects no abnormality. When the normal drive target value setting means (S5) for determining the drive target value of the electric motor and the abnormality detection means detect an abnormality, the steering detection means detects the steering. On the condition that the drive target value of the electric motor is gradually reduced to a predetermined drive target value at the time of abnormality, the drive target value setting unit for abnormality (31, S10, S11, S23, S31) and the drive target value at normal time A power steering device comprising: motor drive means (28, 31, S6) for driving the electric motor based on a drive target value set by a setting means or an abnormal time drive target value setting means.
[0008]
The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
According to said structure, the drive target value of an electric motor is defined based on the output of a steering angular velocity detection means at the time of normal. When an abnormality of the power steering device is detected, the drive target value of the electric motor is gradually reduced to a predetermined drive target value (for example, zero) at the time of abnormality by the function of the drive target value setting unit at the time of abnormality. At this time, the abnormal time drive target value setting means decreases the drive target value on condition that the steering detection means detects the presence of steering.
[0009]
Therefore, even when an abnormality occurs in the power steering device, the drive target value of the electric motor decreases to the drive target value at the time of abnormality during a period when the operation member is not steered, that is, during a straight traveling period. There is no end. That is, since the drive target value is decreased only when the driver is steering, the driver can surely recognize the gradual increase of the steering resistance with the gradual decrease of the drive target value. This makes it possible for the driver to reliably recognize the abnormality of the power steering device and to eliminate the uncomfortable feeling of steering caused by the sudden increase in steering resistance.
[0010]
The rudder angular velocity detection means includes a rudder angle sensor (11) for detecting the steering angle of the operation member and means (31, S4) for time differentiation of the steering angle detected by the rudder angle sensor. May be.
Further, the steering detection means may detect the presence or absence of a change in the steering angle detected by the steering angle sensor, or whether the steering angular speed detection means detects a steering angular speed exceeding a predetermined value (for example, zero). The presence or absence of steering may be detected based on whether or not.
[0011]
The steering angle sensor may be configured to generate a detection signal (for example, a pulse signal) at every constant steering angle change. In this case, the presence or absence of steering is detected based on the presence or absence of the detection signal of the steering angle sensor. be able to.
According to a second aspect of the present invention, when the drive target value at the time when the abnormality detection unit detects an abnormality is less than a predetermined value, the abnormality-time drive target value setting unit gradually increases the drive target value to the predetermined value. The power steering apparatus according to claim 1, comprising (31, S7, S8).
[0012]
When the drive target value at the time when the abnormality occurs in the power steering apparatus is a small value close to the abnormal drive target value, the drive target value is promptly led to the abnormal drive target value. Therefore, the driver cannot feel a gradual increase in steering resistance and may not be able to recognize the occurrence of an abnormality.
Therefore, in the present invention, when the drive target value at the time of abnormality detection is less than a predetermined value, the drive target value is gradually increased to the predetermined value. As a result, in the process in which the drive target value is gradually decreased from the predetermined value to the drive target value at the time of abnormality, the driver can be made to recognize the gradual increase of the steering resistance, and the occurrence of abnormality can be surely recognized. Note that after the drive target value reaches the predetermined value, the drive target value is gradually decreased toward the drive target value, and the drive target value is not increased again as long as the abnormal state continues. .
[0013]
The invention according to claim 3 further includes a rudder angle sensor (11) for detecting a rudder angle change due to an operation of the operation member and outputting a detection signal for every constant rudder angle change, The presence / absence of a detection signal from the steering angle sensor detects the presence / absence of the detection signal, and the abnormal time drive target value setting means decreases the drive target value by a fixed value each time the detection signal from the steering angle sensor is input. The power steering device according to claim 1 or 2, wherein the power steering device is one.
[0014]
In this configuration, the presence or absence of steering is detected based on the presence or absence of a detection signal from a steering angle sensor that outputs a detection signal (for example, a detection pulse) at every constant steering angle change. Then, it is possible to make the driver recognize the occurrence of abnormality by a simple process of reducing the drive target value by a certain value every time the steering angle sensor outputs a detection signal.
According to a fourth aspect of the present invention, the steering detection means detects whether or not the steering angular speed detected by the steering angular speed detection means exceeds a predetermined value. When the rudder angular speed detected by the rudder angular speed detection means is a value exceeding the predetermined value, the drive target value is decreased at a rate of change with time according to the rudder angular speed detected by the rudder angular speed detection means. The power steering apparatus according to claim 1 or 2.
[0015]
In this configuration, the presence or absence of steering is detected based on whether or not the steering angular velocity exceeds a predetermined value (for example, zero). If the rudder angular velocity exceeds a predetermined value, the drive target value is gradually reduced at a time change rate according to the rudder angular velocity. Thereby, since the mode of reduction of the drive target value can be optimized, it is possible to reliably recognize the occurrence of abnormality without giving the driver a feeling of steering discomfort.
For example, it is preferable to gradually decrease the drive target value at a time change rate proportional to the reciprocal of the steering angular velocity. As a result, when the steering angular speed is high, such as during emergency steering, the increase in steering resistance is small, and the steering resistance increases more rapidly as slow steering is performed. Accordingly, it is possible to make the driver surely recognize the occurrence of an abnormality while improving safety.
[0016]
According to a fifth aspect of the present invention, the steering detection means detects whether or not the steering angular speed output from the steering angular speed detection means exceeds a predetermined value. 3. The drive target value is decreased at a predetermined constant rate of time change when the rudder angular velocity detected by the rudder angular velocity detection means exceeds the predetermined value. It is a power steering device.
[0017]
In this configuration, the presence or absence of steering is detected based on whether or not the steering angular velocity exceeds a predetermined value (for example, zero). If the rudder angular velocity exceeds a predetermined value, the drive target value is decreased at a constant rate of time change. As a result, the drive target value can be gradually decreased to the drive target value at the time of abnormality by a simple process that does not require complicated calculation, and the driver can be surely recognized that the abnormality has occurred.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an illustrative view showing a basic configuration of a power steering apparatus according to an embodiment of the present invention. This power steering device is provided in association with the steering mechanism 1 of the vehicle, and is for applying a steering assist force to the steering mechanism 1.
[0019]
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 rack gear meshing with the pinion gear 4. A rack shaft 5 having a portion 5a and extending in the left-right direction of the vehicle is provided. Tie rods 6 are coupled to both ends of the rack shaft 5, and the tie rods 6 are coupled to knuckle arms 7 that support front left and right wheels FL and FR as steering wheels, respectively. The knuckle arm 7 is provided to be rotatable around the kingpin 8.
[0020]
With this configuration, when the steering wheel 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion along the left-right direction of the vehicle by the pinion gear 4 and the rack shaft 5. This linear motion is converted into rotation about the kingpin 8 of the knuckle arm 7, and thereby the front left and right wheels FL, FR are steered.
The steering shaft 3 has a torsion bar 9 that twists according to the direction and magnitude of the steering torque applied to the steering wheel 2, and a hydraulic pressure whose opening degree changes according to the direction and magnitude of the twist of the torsion bar 9. A control valve 23 is incorporated. The hydraulic control valve 23 is connected to a power cylinder 20 that applies a steering assist force to the steering mechanism 1. The power cylinder 20 has a piston 21 provided integrally with the rack shaft 5 and a pair of cylinder chambers 20a and 20b defined by the piston 21, and each of the cylinder chambers 20a and 20b supplies oil. / It is connected to the hydraulic control valve 23 via the return paths 22a and 22b.
[0021]
The hydraulic control valve 23 is further interposed in the middle of the oil circulation path 24 that passes through the reservoir tank 25 and the oil pump 26. The oil pump 26 is driven by the electric motor 27, pumps out the hydraulic oil stored in the reservoir tank 25, and supplies it to 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 is connected to one of the cylinder chambers 20a and 20b of the power cylinder 20 through one of the oil supply / return paths 22a and 22b. Supply hydraulic oil. When the torsion bar 9 is twisted in the other direction, hydraulic oil is supplied to the other of the cylinder chambers 20a and 20b via the other of the oil supply / return paths 22a and 22b. When the torsion bar 9 is hardly twisted, the hydraulic control valve 23 is in an equilibrium state, and the hydraulic oil circulates in the oil circulation path 24 without being supplied to the power cylinder 20.
[0022]
When hydraulic oil is supplied to any cylinder chamber of the power cylinder 20, the piston 21 moves along the vehicle width direction. As a result, a 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. 59-118577.
The electric motor 27 is composed of, for example, a brushless motor, and is controlled by the electronic control unit 30 via the drive circuit 28. The drive circuit 28 is composed of, for example, a power transistor bridge circuit, and supplies power from the in-vehicle battery 40 as a power source to the electric motor 27 in accordance with a control signal supplied from the electronic control unit 30.
[0023]
The electronic control unit 30 includes a microcomputer that operates by receiving power supplied from the in-vehicle battery 40. The microcomputer includes a CPU 31, a RAM 32 that provides a work area of the CPU 31, and the like. A ROM 33 that stores data and the like, and a bus 34 that interconnects the CPU 31, the RAM 32, and the ROM 33 are provided.
The electronic control unit 30 is provided with a steering angle signal output from the steering angle sensor 11 and calculates a steering angular velocity corresponding to the time differential value based on the steering angle signal. The steering angle sensor 11 may output, for example, a pulse signal as a detection signal for every fixed steering angle change. In this case, the steering angle sensor 11 does not output a detection signal when the steering wheel 2 is held at a certain angular position. When the steering wheel 2 is operated quickly, the steering angle sensor 11 outputs a detection signal with a short cycle. When the steering wheel 2 is operated slowly, the steering angle sensor 11 outputs a detection signal with a long cycle. . Therefore, the steering angular speed, which is the speed of steering by the steering wheel 2, can be calculated based on the time interval of the detection signal.
[0024]
The electronic control unit 30 is further supplied with a current detection signal from the current detection circuit 12 that detects the current flowing through the electric motor 27 and a signal from the rotation sensor 15 that detects the rotational position of the rotor of the electric motor 27. It is like that.
Further, a vehicle speed signal output from the vehicle speed sensor 13 is given to the electronic control unit 30. 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 association with the wheel.
[0025]
The electronic control unit 30 controls the driving of the electric motor 27 based on the steering angle signal, the current signal, and the vehicle speed signal given from the steering angle sensor 11, the current detection circuit 12, and the vehicle speed sensor 13, respectively.
FIG. 2 is a characteristic diagram showing a correspondence relationship between the steering angular speed Vθ calculated based on the output of the steering angle sensor 11 and the target rotational speed R of the electric motor 27. The target rotational speed R is determined between the lower limit value R1 and the upper limit value R2 so as to increase between the first threshold value VT1 and the second threshold value VT2 determined with respect to the steering angular speed Vθ. The lower limit value R1 is a standby rotational speed, and the electric motor 27 is rotationally driven at the standby rotational speed R1 for a steering angular speed less than the first threshold value VT1.
[0026]
Based on the vehicle speed, the CPU 31 variably sets the inclination of the target rotational speed R with respect to the steering angular speed Vθ 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. As a result, the higher the vehicle speed, the smaller the target rotational speed R is set, and the steering assist force becomes smaller. Thus, vehicle speed sensitive control for generating an appropriate steering assist force according to the vehicle speed is performed.
[0027]
On the other hand, the CPU 31 repeatedly executes an abnormality monitoring routine for monitoring an abnormality of each part of the apparatus every control cycle. When an abnormality occurs, the CPU 31 executes a fail safe process, stops the electric motor 27, and is undesirable. To prevent proper steering assistance.
FIG. 3 is a flowchart for explaining the control process of the electric motor 27 that the CPU 31 repeatedly executes at predetermined control cycles.
[0028]
The CPU 31 determines whether there is an abnormality by executing an abnormality monitoring routine (step S1). If there is no abnormality (NO in step S1), the CPU 31 reads the vehicle speed from the vehicle speed sensor 13 (step S2). Next, the CPU 31 reads the steering angle signal from the steering angle sensor 11 (step S3), and calculates the steering angular velocity as a time differential value of the steering angle based on this (step S4). Based on the obtained steering angular speed and the read vehicle speed, the CPU 31 sets a target rotational speed R of the electric motor 27 according to the characteristics shown in FIG. 2 (step S5). Then, the electric motor 27 is driven so as to reach the set target rotational speed R (step S6). As a result, a steering assist force corresponding to the rotation speed of the electric motor 27 is generated. Thereafter, when no abnormality is monitored by the abnormality monitoring routine of the CPU 31, the processes of steps S1 to S6 are repeated.
[0029]
When an abnormality is detected (YES in step S1), the CPU 31 determines whether the target rotational speed R has never been equal to or higher than a predetermined rotational speed Z (for example, 2000 rpm) after occurrence of the abnormality (step S7).
When the target rotational speed R is not equal to or higher than the predetermined rotational speed Z (YES in step S7), the CPU 31 adds a constant K (for example, K = 4) to the current target rotational speed R to set a new target rotational speed R. (Step S8). Based on the new target rotational speed R, the electric motor 27 is driven (step S6). Thereafter, when the abnormal state continues (YES in step S1), the processes of steps S1, S7, and S8 are repeated for each control cycle until the target rotational speed R becomes equal to or higher than the predetermined rotational speed Z (step S7). Thus, when an abnormality occurs, the target rotational speed R is gradually increased to a predetermined rotational speed Z at a constant rate of change with time.
[0030]
If the target rotational speed R is equal to or higher than the predetermined rotational speed Z even once after the occurrence of the abnormality (NO in step S7), the CPU 31 checks whether or not there is an output signal from the steering angle sensor 11 (step S9). When the pulse signal output from the steering angle sensor 11 is not confirmed (NO in step S9), the CPU 31 drives the electric motor 27 at the previous target rotational speed R (step S6).
When a pulse signal is output from the steering angle sensor 11 (YES in step S9), the CPU 31 subtracts a constant x (for example, x = 1) from the current target rotational speed R to obtain a new target rotational speed R. Set (step S10). If the newly set target rotational speed R is not zero (NO in step S11), the CPU 31 drives the electric motor 27 based on the target rotational speed R (step S6).
[0031]
If the abnormal state continues (YES in step S1), the processes in steps S7, S9, S10, S11, and S6 are repeated for each control cycle. As a result, every time the steering angle sensor 11 outputs a pulse signal, that is, every time there is a constant steering angle change, the target rotational speed R is decreased by a constant value x. When the target rotation speed R gradually decreases to zero (YES in step S11), the CPU 31 stops the electric motor 27 (step S12).
[0032]
FIG. 4 is a diagram illustrating an example of a temporal change in the target rotation speed R. In FIG.
If an abnormality of the power steering apparatus is detected at time F (YES in step S1 in FIG. 3), the target rotational speed R of the electric motor 27 is not equal to or higher than the predetermined rotational speed Z after the occurrence of the abnormality (see FIG. The CPU 31 gradually increases the target rotational speed R to a predetermined rotational speed Z by increasing the target rotational speed R by a constant K for each control cycle (step S8 in FIG. 3).
After the target rotational speed R is once greater than the predetermined rotational speed Z (NO in step S7 in FIG. 3), the pulse signal generated from the steering angle sensor 11 is output during the period T1 when the steering angular speed Vθ is high. Since the cycle is short, the target rotational speed R decreases rapidly.
[0033]
In a period T2 in which there is no change in the steering angle (that is, the steering angular velocity Vθ = 0), no pulse signal is generated from the steering angle sensor 11 (NO in step S9 in FIG. 3). Therefore, the CPU 31 determines that the steering is not performed, and the target rotational speed R is kept unchanged.
In the period T3 when the steering angular velocity Vθ is low, the cycle of the pulse signal generated from the steering angle sensor 11 is long. For this reason, the target rotational speed R decreases gradually. When the target rotational speed R becomes zero (step S11 in FIG. 3), the electric motor 27 stops (step S12 in FIG. 3).
[0034]
As described above, according to this embodiment, when an abnormality occurs, every time the steering angle sensor 11 outputs a pulse signal, the target rotational speed R is decreased by a constant x and the electric motor 27 is led to a stopped state. . That is, the target rotational speed R does not decrease in a situation where there is no change in the steering angle as in straight traveling, and the target rotational speed R decreases and the steering resistance increases only when substantial steering is performed. Become. As a result, in a simple process, when an abnormality occurs, the driver can be surely recognized that the abnormality has occurred through the gradual increase of the steering resistance, and there is no possibility of causing an uncomfortable steering feeling due to a sudden increase in the steering resistance.
[0035]
Furthermore, in this embodiment, when the target rotational speed R at the time of occurrence of abnormality is less than the predetermined rotational speed Z, the target rotational speed R is gradually increased to the predetermined rotational speed Z in advance (increased by a constant K for each control cycle). Thus, a process of gradually decreasing the target rotational speed R to zero is performed. As a result, the driver can surely feel a gradual increase in steering resistance, so that the occurrence of an abnormality can be reliably transmitted to the driver.
FIG. 5 is a flowchart for explaining processing by the power steering apparatus according to the second embodiment of the present invention. In the description of the second embodiment, reference is again made to FIGS. 1 and 2 described above. FIG. 5 shows a process that the CPU 31 repeatedly executes for each control cycle for controlling the electric motor 27. In FIG. 5, a process similar to the step shown in FIG. The steps performed are indicated with the same reference numerals as in FIG.
[0036]
In this embodiment, when it is determined in step S7 that the target rotational speed R is equal to or higher than the predetermined rotational speed Z, the CPU 31 performs time differentiation on the steering angle signal read from the steering angle sensor 11 to obtain the steering angular speed Vθ. Calculation is performed (step S21). If the determined steering angular velocity Vθ is zero (YES in step S22), the CPU 31 drives the electric motor 27 based on the previous target rotation speed R (step S6). If the determined steering angular velocity Vθ is not zero (NO in step S22), the CPU 31 subtracts a variable A / Vθ (where A is a positive proportionality constant) proportional to the inverse of the steering angular velocity Vθ from the current target rotational speed R. Then, a new target rotational speed R is set (step S23).
[0037]
If the newly set target rotational speed R is greater than zero (NO in step S11), the CPU 31 drives the electric motor 27 based on the target rotational speed R (step S6).
If the abnormal state continues (YES in step S1), the processes in steps S7, S21, S22, S23, S11, and S6 are repeated every control cycle. Thereby, when the obtained steering angular velocity is not zero, that is, when there is a steering angle change, the numerical value A / Vθ proportional to the inverse of the steering angular velocity Vθ is subtracted from the target rotational speed R.
[0038]
When the target rotation speed R gradually decreases to zero (YES in step S11), the CPU 31 stops the electric motor 27 (step S12).
FIG. 6 is a diagram illustrating an example of a temporal change in the target rotation speed R in this embodiment.
If an abnormality is detected in the power steering device at time F (YES in step S1 in FIG. 5), the target rotational speed R of the electric motor 27 is not more than the predetermined rotational speed Z after the occurrence of the abnormality (see FIG. 5). 5 in step S7), the CPU 31 gradually increases the target rotational speed R to the predetermined rotational speed Z by increasing the target rotational speed R by a constant K for each control period (step S8 in FIG. 5).
[0039]
After the target rotational speed R has become equal to or higher than the predetermined rotational speed Z (NO in step S7 in FIG. 5), during the period T5 when the steering angular speed Vθ is zero (YES in step S22 in FIG. 5), the target The rotational speed R is kept unchanged.
When the steering angular velocity Vθ is not zero (NO in step S22 in FIG. 5), a value A / Vθ proportional to the inverse of the steering angular velocity Vθ is subtracted from the target rotational velocity R to obtain a new target rotational velocity R (see FIG. 5 step S23). That is, the target rotational speed R gradually decreases during the period T4 when the steering angular speed Vθ is high, and the target rotational speed R decreases rapidly during the period T6 when the steering angular speed Vθ is small. When the target rotational speed R becomes zero (step S11 in FIG. 5), the electric motor 27 stops (step S12 in FIG. 5).
[0040]
As described above, when an abnormality occurs, the target rotational speed R of the electric motor 27 decreases on the condition that the steering angular speed Vθ is not zero. At this time, since the numerical value A / Vθ proportional to the reciprocal of the steering angular velocity Vθ is subtracted from the target rotational speed R, when the steering angular velocity Vθ is large, the reduction amount of the steering assist force is small and the steering angular velocity Vθ is small. The amount of decrease in the steering assist force increases. That is, as the steering angular velocity Vθ is larger as in emergency steering, the increase in steering resistance is smaller, and the steering resistance increases quickly when slow steering is being performed. Therefore, it is possible to make the driver surely recognize the occurrence of an abnormality while improving safety.
[0041]
In addition, the same effects as in the case of the first embodiment described above can be achieved together.
FIG. 7 is a flowchart for explaining processing by the power steering apparatus according to the third embodiment of the present invention.
In the description of the third embodiment, reference is again made to FIGS. 1 and 2 described above. FIG. 7 shows a process that the CPU 31 repeatedly executes for each control cycle for controlling the electric motor 27. In FIG. 7, the same process as the step shown in FIG. The steps performed are indicated with the same reference numerals as in FIG.
[0042]
In this embodiment, when it is determined in step S22 that the steering angular speed Vθ is not zero, the CPU 31 subtracts a constant y (for example, y = 4) from the current target rotational speed R to obtain a new target rotational speed. R is set (step S31). If the newly set target rotational speed R is greater than zero (NO in step S11), the CPU 31 drives the electric motor 27 based on the target rotational speed R (step S6).
[0043]
If the abnormal state continues (YES in step S1), the processes in steps S7, S21, S22, S31, S11, and S6 are repeated every control cycle. Thus, under the condition that the steering angular velocity Vθ is not zero, that is, in a situation where a steering change is detected, the target rotational speed R gradually decreases by a constant y (that is, at a constant time change rate) every control cycle. Is done. When the target rotation speed R gradually decreases to zero (YES in step S11), the CPU 31 stops the electric motor 27 (step S12).
[0044]
FIG. 8 is a diagram illustrating an example of a temporal change in the target rotation speed R in this embodiment.
If an abnormality is detected in the power steering device at time F (YES in step S1 in FIG. 7), the target rotational speed R of the electric motor 27 is not equal to or higher than the predetermined rotational speed Z after the occurrence of abnormality (see FIG. 7), the CPU 31 gradually increases the target rotational speed R to a predetermined rotational speed Z by increasing the target rotational speed R by a constant K for each control cycle (step S8 in FIG. 7).
[0045]
After the target rotational speed R becomes equal to or higher than the predetermined rotational speed Z (NO in step S7 in FIG. 7), the target rotational speed R is kept unchanged during the period T8 when the steering angular speed Vθ is zero ( YES in step S22 of FIG.
In the periods T7 and T9 where the steering angular velocity Vθ is not zero (NO in step S22 in FIG. 7), the target rotational speed R is decreased by a constant y for each control period regardless of the magnitude of the steering angular velocity Vθ (in FIG. 7). Step S31). Therefore, the target rotational speed R decreases at a constant rate of time change only when steering is being performed. When the target rotational speed R becomes zero (step S11 in FIG. 7), the electric motor 27 is stopped (step S12 in FIG. 7).
[0046]
According to this embodiment, the same effect as that of the second embodiment described above can be achieved. Moreover, since it is not necessary to calculate the value A / Vθ that is proportional to the reciprocal of the steering angular velocity Vθ, it is possible to gradually reduce the drive target value to the abnormal time drive target value by a simple process that does not require complicated calculation, The person can be surely recognized the abnormality.
Although three embodiments of the present invention have been described above, the present invention can be implemented in other forms.
[0047]
For example, in the above three embodiments, the target rotational speed R is used as the drive target value of the electric motor 27. However, the drive target voltage (or current) of the electric motor 27 may be used as the drive target value. .
In the above embodiment, the presence / absence of steering is detected based on the output of the steering angle sensor 11. For example, the presence / absence of steering is determined based on the output of the torque sensor that detects the steering torque applied to the steering wheel 2. It may be detected.
[0048]
Further, in the second and third embodiments, it is determined that steering is present when the steering angular velocity Vθ is not zero. However, on the condition that the steering angular velocity Vθ exceeds a positive threshold value. Further, it may be determined that there is steering.
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a basic configuration of a power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing a relationship between a steering angular speed and a target rotational speed of an electric motor.
FIG. 3 is a flowchart for explaining electric motor control processing that is repeatedly executed by a CPU every predetermined control cycle;
FIG. 4 is a diagram illustrating an example of a temporal change in a target rotation speed.
FIG. 5 is a flowchart for explaining a control process of an electric motor target rotation speed in a power steering apparatus according to a second embodiment of the present invention.
FIG. 6 is a diagram illustrating an example of a temporal change in a target rotation speed of the electric motor by the control process according to the second embodiment.
FIG. 7 is a flowchart for explaining an electric motor control process in a power steering apparatus according to a third embodiment of the present invention;
FIG. 8 is a diagram illustrating an example of a temporal change in a target rotation speed of an electric motor by a control process according to the third embodiment.
[Explanation of symbols]
1 Steering mechanism
2 Steering wheel
9 Torsion bar
11 Rudder 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
31 CPU
33 ROM

Claims (5)

A power steering device that generates a steering assist force by hydraulic pressure generated by a pump driven by an electric motor,
Rudder angular velocity detection means for detecting a rudder angular velocity which is a steering speed by an operation member for steering the vehicle;
An abnormality detecting means for detecting an abnormality of the power steering device;
Steering detection means for detecting the presence or absence of steering by the operation member;
A normal time drive target value setting means for determining a drive target value of the electric motor based on an output of the steering angular velocity detection means when the abnormality detection means has not detected an abnormality;
When the abnormality detection means detects an abnormality, the abnormal-time drive target that gradually reduces the drive target value of the electric motor to a predetermined abnormal-time drive target value on condition that the steering detection means detects steering. Value setting means;
A power steering apparatus comprising: motor drive means for driving the electric motor based on a drive target value set by the normal drive target value setting means or the abnormal drive target value setting means. The abnormal-time drive target value setting means includes means for gradually increasing the drive target value to the predetermined value when the drive target value at the time when the abnormality detection means detects the abnormality is less than the predetermined value. The power steering apparatus according to claim 1. A steering angle sensor that detects a steering angle change due to an operation of the operation member and outputs a detection signal for each constant steering angle change;
The steering detection means detects presence or absence of a detection signal from the rudder angle sensor,
3. The power according to claim 1, wherein the abnormal drive target value setting means decreases the drive target value by a fixed value each time a detection signal from the steering angle sensor is input. Steering device. The steering detection means detects whether or not the steering angular speed detected by the steering angular speed detection means exceeds a predetermined value.
The abnormal-time drive target value setting means is driven at a rate of time change corresponding to the steering angular speed detected by the steering angular speed detection means when the steering angular speed detected by the steering angular speed detection means exceeds the predetermined value. The power steering apparatus according to claim 1 or 2, wherein the target value is decreased. The steering detection means detects whether or not the steering angular speed output from the steering angular speed detection means exceeds a predetermined value.
The abnormal-time drive target value setting means decreases the drive target value at a predetermined constant rate of time change when the steering angular speed detected by the steering angular speed detection means exceeds the predetermined value. The power steering apparatus according to claim 1, wherein the power steering apparatus is a power steering apparatus.

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