JP4378099B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering device that assists steering by driving a pump with an electric motor.
[0002]
[Prior art]
Conventionally, in a power steering device, an electric motor is driven based on the output of a torque sensor that detects steering torque to drive an oil pump, and the hydraulic pressure in one of two chambers of a power cylinder separated by a piston is controlled. A technique for assisting steering by increasing the speed is known. Here, Patent Document 1 discloses a technique in which a bypass circuit that communicates two power cylinder chambers and a bypass valve that can switch a communication state / non-communication state of the bypass circuit are provided.
[0003]
In this technique, when the torque input to the steering is small, the bypass valve is in a communicating state, and the differential pressure between the left and right power cylinder chambers is eliminated, thereby enabling manual steering by the driver's steering.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-29079 (see FIG. 3).
[0005]
[Problems to be solved by the invention]
If the pump stops due to an abnormality and steering assist is not possible, the driver will feel uncomfortable. Therefore, it is necessary to check the pump operation when the electric power steering control device is turned on.
In this pump operation check, when the pump is rotated, hydraulic oil is supplied to the power cylinder. Since unnecessary steering assistance is performed by the differential pressure generated thereby, there is a possibility that the driver may feel uncomfortable.
[0006]
The present invention has been made paying attention to the above-mentioned problems, and in a power steering device that drives a pump by an electric motor, when performing pump operation confirmation when power is turned on, operation confirmation is performed without giving the driver a sense of incongruity. An object of the present invention is to provide a power steering device capable of achieving the above.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the invention according to claim 1, the pump is driven, the working oil is returned to the hydraulic circuit formed by the pump and the bypass oil passage, and the pump is operated normally based on the rotational speed of the electric motor. or provided an abnormality determination means to determine an abnormality, the abnormality if the pump is determined to be normal by the determining means, during the first set time the rotational speed of the electric motor is reduced can be preset well after the normal determination Therefore, the abnormality determination means decided to open the bypass valve. That is, the hydraulic oil supplied by the rotation of the pump returns to the hydraulic circuit formed by the pump and the bypass oil passage, so that it is not supplied to the power cylinder. Further, since the bypass valve is open during the first set time during which the rotation speed of the electric motor decreases, the operation of the pump can be confirmed without giving the driver a sense of incongruity.
[0008]
According to the second aspect of the present invention, the motor generated by the motor abnormality determination control is provided by applying a reverse driving force (braking force) to the electric motor after the abnormality determination means determines that the pump is normal. The inertial force of rotation can be quickly stopped, and the first setting time can be set short. Thereby, it is possible to prevent a delay in returning to the normal fail-safe valve driving state (normal controllable state).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 is a system diagram showing the overall configuration of a power steering apparatus according to Embodiment 1 of the present invention. First, the configuration will be described. 1 is a steering wheel, 2 is a steering shaft, 3 is a rack and pinion gear mechanism, 5 is a power steering mechanism that assists the steering force of the driver, and 6 is an external gear driven by an electric motor 6a. An oil pump of the type, 7 is a steering wheel, 8 is a warning lamp for notifying the driver that a failure has occurred in the steering system, and 10 is a steering control unit.
[0010]
The oil pump 6 that is a hydraulic source of the power steering mechanism 5 is provided in a hydraulic pipe 61 that communicates the first cylinder chamber 51 and the second cylinder chamber 52 of the power cylinder 5a. When the driver operates the steering wheel 1, the rotation direction of the electric motor 6 a is switched according to the operation direction, and the oil between the first cylinder chamber 51 and the second cylinder chamber 52 is supplied and discharged to thereby change the driver's direction. Assist steering force. Specifically, when the steering 1 is steered to the right in the figure, the electric motor 6a is driven in the direction in which the hydraulic pressure is supplied from the second cylinder chamber 52 to the first cylinder chamber 51 to move integrally with the rack shaft 54. The piston 53 is assisted to the second cylinder chamber side.
[0011]
The hydraulic pipe 61 is provided with a bypass circuit 62 that connects the first cylinder chamber 51 and the second cylinder chamber 52 without passing through the oil pump 6. On the bypass circuit 62, an electronically controlled fail-safe valve 4 that operates based on a command signal from the control unit 10 is provided.
[0012]
The fail-safe valve 4 uses a normally open valve that is closed when a voltage is supplied in response to a command signal from the control unit 10 and is open when no voltage is supplied. As a result, even if some abnormality occurs in the steering system and the power supply is shut down, the first cylinder chamber 51 and the second cylinder chamber 52 can be in communication with each other. Steering can be ensured.
[0013]
Further, the steering shaft 2 is provided with a torque sensor 12 for detecting the steering torque of the driver.
[0014]
The control unit 10 receives a steering torque signal from the torque sensor 12, an IGN signal from the ignition switch 13, an engine speed signal from the engine speed sensor 14, and a vehicle speed signal from the vehicle speed sensor 15. Based on these input signals, command signals are output to the electric motor 6 a of the oil pump 6, the fail safe valve 4 and the warning lamp 8.
[0015]
FIG. 2 is a block diagram showing the configuration inside the control unit 10. A power supply circuit 101 receives a voltage signal from the battery 11 and an IGN signal from the ignition switch 13 and transmits / receives a signal to / from the main microcomputer 107.
[0016]
An engine speed processing circuit 102 outputs an engine speed signal from the engine speed sensor 14 to the main microcomputer 107. A torque sensor processing circuit 103 outputs a torque signal from the torque sensor 12 to the main microcomputer 107 and also to the sub-microcomputer 108. A vehicle speed signal processing circuit 104 outputs a vehicle speed signal from the vehicle speed sensor 15 to the main microcomputer 107. A diagnostic circuit 105 outputs a diagnostic signal input via the connector 16 to the main microcomputer. Reference numeral 106 denotes a CAN communication circuit, which outputs a signal transmitted by the vehicle system CAN to the main microcomputer 107.
[0017]
Reference numeral 108 denotes a sub microcomputer, which monitors the main microcomputer 107. When a failure occurs in the main microcomputer 107, a control signal can be output to the fail safe relay 109, the fail safe valve driving circuit 116, and the warning lamp driving circuit 117.
[0018]
Reference numeral 109 denotes a fail-safe relay, which cuts off the power supply for driving the motor when any failure occurs. An EEPROM 110 stores various data necessary for control and can update the data. Reference numeral 111 denotes a fail safe relay diagnosis input circuit which outputs an operation diagnosis signal of the fail safe relay 109 to the main microcomputer 107. A motor driving circuit 112 supplies a voltage to the electric motor 6 a based on a command signal from the main microcomputer 107. Reference numeral 113 denotes a current monitor circuit which detects the current value of the electric motor 6 a and outputs it to the main microcomputer 107. A motor terminal voltage circuit 114 outputs the terminal voltage of the electric motor 6 a to the main microcomputer 107.
[0019]
Reference numeral 115 denotes a motor rotation signal processing circuit that outputs the number of rotations of the electric motor 6 a to the main microcomputer 107. Reference numeral 116 denotes a fail safe valve drive circuit that outputs a drive signal to the fail safe valve 4 based on a command signal from the main microcomputer 107 or the sub microcomputer 108. A warning lamp driving circuit 117 outputs a command signal to the warning lamp 8 based on a command signal from the main microcomputer 107 or the sub-microcomputer 108.
[0020]
FIG. 3 is a schematic diagram showing the configuration of the pump unit in the first embodiment. First, the configuration will be described. 61a, 61b, 61c, 61d are hydraulic pipes connecting the cylinder chambers 51 and the oil pump 6. 62a, 62a ′, 62b, 62b ′ are bypass oil passages that communicate the hydraulic pipes 61b, 61c. 202a, 202b, and 205 are reservoir tanks that supply oil to the oil pump 6 and store drained oil. 201a and 201b are check valves that are closed when hydraulic pressure is generated by the oil pump 6 and opened when negative pressure is generated.
[0021]
Reference numeral 203 denotes a return check valve, which will be described in detail later. A check valve 204 supplies drained oil to the reservoir tank 205, and a drain oil path 63 connects the return check valve 203, the reservoir tank 205, and the check valve 204.
[0022]
Here, the return check valve 203 will be described. The return check valve 203 includes a first return check valve 203a, a second return check valve 204a, a spool valve 210, and return springs 206a and 206b that urge the spool valve 210 to the center.
[0023]
The first return check valve 203a is provided with a first hydraulic chamber 207a having a connection port for the hydraulic pipes 61a and 61b, and a first piston chamber 208a having a connection port for the drain oil passage 63 and the bypass oil passage 62a ′. It has been. Similarly, the second return check valve 203b includes a second hydraulic chamber 207b having a connection port with the hydraulic pipes 61c and 61d, and a second piston chamber having a connection port with the drain oil passage 63 and the bypass oil passage 62b ′. 208b is provided.
[0024]
The spool valve 210 is acted on by the urging force on the right side in the figure by the urging force of the return spring 206a, the oil pressure of the first hydraulic chamber 207a, and the oil pressure of the first piston chamber 208a. On the other hand, as the biasing force on the opposite side (left side in the figure), the biasing force by the return spring 207a, the hydraulic pressure in the second hydraulic chamber 207b, and the hydraulic pressure in the second piston chamber 208b act. Thereby, the position of the spool valve 210 is determined.
[0026]
(Control processing to open the bypass valve during pump abnormality judgment)
[0027]
Next, power steering control for determining a pump abnormality based on the pump operation signal and opening the bypass valve during the abnormality determination will be described. FIG. 4 is a flow chart showing the control when the pump abnormality is determined and the bypass valve is opened during the abnormality determination. This control flow is repeatedly executed at predetermined intervals (for example, 10 msec).
[0028]
In step 301, it is determined whether or not the initial motor check end flag is 1. If it is 0, the process proceeds to step 302. If it is 1, this control flow is ended.
[0029]
In step 302, it is determined whether or not the initial motor check abnormality flag is 1. If it is 0, the process proceeds to step 303. If it is 1, this control flow is terminated.
[0030]
In step 303, it is confirmed whether or not the battery voltage is within a normal range. If it is within the normal range, the process proceeds to step 304. If it is not within the normal range, this control flow ends.
[0031]
In step 304, it is confirmed whether another failure is detected. If no other failure is detected, the process proceeds to step 305. If a failure is detected, this control flow is terminated.
[0032]
In step 305, the battery voltage is set to decrease with a change in motor energization time Tm (corresponding to the first set time described in the claims), and the process proceeds to step 306.
[0033]
In step 306, it is determined whether or not the fail-safe valve is open. If it is open, the process proceeds to step 307. If it is closed, this control flow is ended.
[0034]
In step 307, energization of the motor is started, and the process proceeds to step 308.
[0035]
In step 308, it is confirmed whether the return time timer T exceeds a predetermined time Tm. If so, go to Step 309, otherwise go to Step 310.
[0036]
In step 309, the motor energization is terminated, and the process proceeds to step 311.
[0037]
In step 310, the count is incremented and the process proceeds to step 311.
[0038]
In step 311, it is determined whether or not the motor rotation sensor output exceeds a predetermined rotation speed. If it exceeds, go to Step 312, otherwise go to Step 321 .
[0039]
In step 312, the motor energization is terminated, and the process proceeds to step 313.
[0040]
In step 313, the initial motor check abnormality flag is set to 0, and the process proceeds to step 314.
[0041]
In step 314, the initial motor check end flag is set to 1, and the process proceeds to step 315.
[0042]
In step 315, it is determined whether or not the return time timer T exceeds the predetermined time Tm. If it exceeds, the process proceeds to step 317. If not, the process proceeds to step 316 and counts up again. Repeat steps.
[0043]
In step 317, the failsafe valve is closed.
[0044]
In step 318, it is determined whether the torque signal is smaller than a predetermined value. If it is smaller, the process proceeds to step 319. If it is larger, the process proceeds to step 320.
[0045]
In step 319, the assist control is immediately permitted, and this control flow ends.
[0046]
In step 320, assist control is gradually increased and allowed.
[0047]
In step 321, it is confirmed whether or not the return time timer T exceeds the predetermined time Tm. If it exceeds, the process proceeds to step 322, and if it does not exceed, this control flow is terminated.
[0048]
In step 322, an initial motor check abnormality flag is set to 1.
[0049]
In step 323, the initial motor check end flag is set to 1,
This control flow ends.
[0050]
The above contents will be described with reference to the time chart of FIG.
At time T _a, in a state where the initial motor check not completed, is within the battery voltage is normal range, the motor drive is turned OFF.
[0051]
At time T _b, after confirming that the fail-safe valve 4 is open, starts the motor current in step 307, it starts counting up the counter T. As a result, the motor speed increases. At this time, as shown in the pump unit configuration diagram of FIG. 7, the fail safe valve 4 is open, so that the hydraulic oil is indicated by a thick line portion. → Reflux in the direction of the bypass oil passage 62a (or the opposite direction). Therefore, the hydraulic pressure is not supplied to the power cylinder chambers 51 and 52.
[0052]
At time _Tc , the motor energization is terminated in step 312 because the motor rotation number exceeds a predetermined number indicating that it is operating normally. At this time, the count value of the counter T does not exceed the predetermined value Tm, so the count up is continued.
[0053]
At a time _Td , when a predetermined time Tm that is set in advance elapses, the motor rotation speed becomes a value that is substantially close to zero. At this time, since there is no possibility that hydraulic pressure is supplied by the pump 6, the fail-safe valve drive state is turned ON and the fail-safe valve 4 is closed.
[0054]
This shifts to the normal control state. At this time, if the driver is performing manual steering while the pump abnormality determination control is being performed, a large torque signal is input to the torque sensor 12. If the assist control is immediately permitted based on this torque signal when shifting to the normal control, the steering load is suddenly reduced and the driver may feel uncomfortable. Therefore, by detecting the signal of the torque sensor 12 and allowing the assist control immediately when the torque signal falls below a predetermined value, the assist control amount is gradually increased and allowed when the torque signal exceeds the predetermined value. Assist steering control is achieved.
[0055]
As described above, in the first embodiment, during the execution of the motor abnormality determination control, the fail safe valve 4 is kept open for a predetermined time Tm, and the drive of the electric motor 6a is confirmed. The hydraulic oil generated by the pump 6 can be recirculated to the thick line portion in FIG. Thereby, the oil which operates with the pump 6 is not supplied to the power cylinders 51 and 52. Therefore, no differential pressure is generated by the motor abnormality determination control, and unnecessary steering assistance can be prevented.
[0056]
(Second embodiment)
Next, a second embodiment will be described. Since the basic configuration is the same as that of the first embodiment, only different points will be described.
[0057]
FIGS. 8 and 9 are flowcharts when the bypass valve is closed after applying the braking force in the direction opposite to the rotation direction of the electric pump after the abnormality determination is completed. Since steps 301 to 323 are the same as those in the first embodiment, only different parts will be described.
This control flow is repeatedly executed at predetermined intervals (for example, 10 msec).
[0058]
(Motor braking control process in motor abnormality judgment control)
In step 401, it is determined whether or not the brake flag is 0. If it is 0, the process proceeds to step 301. If it is not 0, the process proceeds to step 403.
[0059]
In step 402, the energization of the electric motor 6a is set in the reverse direction, and the process proceeds to step 313.
[0060]
In step 403, it is confirmed whether or not the return time timer T2 has exceeded a predetermined time Tm ₂ (corresponding to the second set time described in the claims). When it exceeds tm ₂ proceeds to step 404, when it does not exceed the process proceeds to step 406.
[0061]
In step 404, energization of the electric motor 6a is terminated, and the process proceeds to step 405.
[0062]
In step 405, the brake flag is set to 0, and the process proceeds to step 317.
[0063]
In step 406, the return time timer T2 is counted up and the routine proceeds to step 407.
[0064]
In step 407, the brake flag is set to 1, and this control flow is terminated.
[0065]
The above contents will be described with reference to the time chart of FIG.
At time T _a, in a state where the initial motor check not completed, is within the battery voltage is normal range, the motor drive is turned OFF.
[0066]
At time T _b, after confirming that the fail-safe valve 4 is open, it starts the power supply to the electric motor 6a at step 307, and starts counting up the counter T. As a result, the motor speed increases. At this time, since the fail safe valve 4 is open, the hydraulic oil recirculates, and the hydraulic pressure is not supplied to the power cylinder chambers 51 and 52.
[0067]
At time _Tc , since the motor speed exceeds a predetermined speed indicating that the motor is operating normally, in step 402, the energization of the electric motor 6a is reversed. At the same time, the return time timer T2 starts counting up.
[0068]
At time T _d, the energization in the reverse direction to the electric motor 6a is, after a preset time Tm ₂ continues to exit the power supply to the electric motor 6a, as well as set the in brake flag to 0, failsafe Close valve 4.
[0069]
As described above, in the second embodiment, when the motor rotation speed exceeds the predetermined rotation speed, a reverse driving force (braking force) is immediately applied to the electric motor 6a. As a result, the inertial force of the motor rotation generated by the motor abnormality determination control can be quickly stopped, and a return delay to the normal fail-safe valve driving state (normal controllable state) can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the overall configuration of a power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing the control content of hydraulic pressure return control in the first embodiment.
FIG. 3 is a schematic diagram illustrating a configuration of a pump unit according to the first embodiment.
4 is a flowchart showing the control content of control for opening a bypass valve during pump abnormality determination in Embodiment 1. FIG.
FIG. 5 is a flowchart showing control details of control for opening a bypass valve during pump abnormality determination in the first embodiment.
6 is a time chart showing control details of control for opening a bypass valve during pump abnormality determination in Embodiment 1. FIG.
7 is a configuration diagram of a pump unit showing the flow of oil during execution of motor abnormality determination control in Embodiment 1. FIG.
FIG. 8 is a flowchart when the bypass valve is closed after applying a braking force in the direction opposite to the rotation direction of the electric pump after completion of the abnormality determination in the second embodiment.
FIG. 9 is a flowchart when the bypass valve is closed after applying a braking force in the direction opposite to the rotation direction of the electric pump after the abnormality determination in the second embodiment is completed.
FIG. 10 is a time chart when the bypass valve is closed after applying a braking force in a direction opposite to the rotation direction of the electric pump after the abnormality determination in the second embodiment is completed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Gear mechanism 4 Fail safe valve 5 Power steering mechanism 5a Power cylinder 6 Oil pump 6a Electric motor 7 Steering wheel 8 Warning lamp 10 Control unit (SBWCU)
11 Battery 12 Steering angle sensor 13 Ignition switch 14 Engine speed sensor 15 Vehicle speed sensor 51, 52 Power cylinder chamber 54 Rack shaft 61a, b, c, d Hydraulic pipe 62a, a ', b, b' Bypass oil passage 201a, b Check valve 202a, b Reserve tank 203a, b Return check valve 204 Check valve 205 Reserve tank 206 Return spring 207 Hydraulic chamber 208 Piston chamber 210 Spool valve

Claims (6)

Steering torque detecting means for detecting the steering torque of the driver;
A pump driven by an electric motor;
Steering assist means having a hydraulic system that performs steering assist by guiding the discharge pressure of the pump to two chambers of a power cylinder separated by a piston;
Assist steering control means for controlling the driving of the electric motor based on the detected steering torque;
In the power steering device with
A bypass oil passage communicating the two power cylinder chambers;
A bypass valve that is on the bypass oil passage and controls a communication state of the communication path based on a control signal from the assist steering control means;
Upon power-up, regardless of the steering intention of the driver, the outputs a drive signal to the electric motor, the pump is driven, the hydraulic oil is refluxed in the hydraulic circuit formed by the bypass fluid passage and said pump, said An abnormality determining means for determining whether the pump is normal or abnormal based on the number of rotations of the electric motor ;
Provided,
When the abnormality determining unit determines that the pump is normal, the abnormality determining unit is configured to perform the bypass valve during a first preset time during which the rotation speed of the electric motor can be sufficiently reduced after the normal determination. A power steering device characterized by opening the valve. Steering torque detecting means for detecting the steering torque of the driver;
A pump driven by an electric motor;
Steering assist means having a hydraulic system that performs steering assist by guiding the discharge pressure of the pump to two chambers of a power cylinder separated by a piston;
Assist steering control means for controlling the driving of the electric motor based on the detected steering torque;
In the power steering device with
A bypass oil passage communicating the two power cylinder chambers;
A bypass valve that is on the bypass oil passage and controls a communication state of the communication path based on a control signal from the assist steering control means;
An abnormality determination means for outputting a drive signal to the electric motor regardless of the driver's steering intention when turning on the power, and determining whether the pump is normal or abnormal based on the rotation speed of the electric motor ;
Provided,
When the abnormality determining unit determines that the pump is normal, the abnormality determining unit is configured to perform the bypass valve during a first preset time during which the rotation speed of the electric motor can be sufficiently reduced after the normal determination. A power steering device characterized in that the valve is opened and a driving force opposite to the rotational direction of the pump is applied for a preset second setting time. Steering torque detecting means for detecting the steering torque of the driver;
A pump driven by an electric motor;
Steering assist means having a hydraulic system that performs steering assist by guiding the discharge pressure of the pump to two chambers of a power cylinder separated by a piston;
Assist steering control means for controlling the driving of the electric motor based on the detected steering torque;
In the power steering device with
A bypass oil passage communicating the two power cylinder chambers;
A bypass valve that is on the bypass oil passage and controls a communication state of the communication path based on a control signal from the assist steering control means;
An abnormality determination means for outputting a drive signal to the electric motor regardless of the driver's steering intention when turning on the power, and determining whether the pump is normal or abnormal based on the rotation speed of the electric motor ;
Provided,
The abnormality determining means outputs a drive signal to the motor after confirming that the bypass valve is open. When the abnormality determining means determines that the pump is normal, the abnormality determining means The power steering device, wherein the bypass valve is opened for a first preset time that can sufficiently reduce the rotational speed. The power steering apparatus according to any one of claims 1 to 3,
The power steering device, wherein the bypass valve is a normally open valve. In the power steering device according to any one of claims 1 to 4,
When the abnormality determination unit determines that the pump is normal, and after the normal determination, if the torque signal from the steering torque detection unit is smaller than a predetermined value, the steering assist unit performs assist control based on the torque signal. When the assist signal is controlled by an amount, and the torque signal is larger than the predetermined value, the assist control is performed by gradually increasing the assist control amount from a control amount smaller than the assist control amount based on the torque signal. Power steering device. The power steering device according to any one of claims 1 to 5,
A motor rotation sensor;
The abnormality determining means is
If the output of the motor rotation sensor exceeds a predetermined number of rotations during a predetermined time, it is determined that the motor is operating normally,
The power steering device according to claim 1, wherein if the output of the motor rotation sensor does not exceed the predetermined number of rotations even after the predetermined time has elapsed, it is determined that there is an abnormality in the motor.

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