JP2003048553A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out appropriate steering assist depending on a vehicle speed even in a case where abnormality is generated in a vehicle speed detecting means or a signal line thereof. SOLUTION: In this power steering device, a steering assist force is applied to a steering mechanism 1 with an electric motor 27 being as a generation source of the steering assist force. An electronic control unit 30 finds a steering angle speed based on an output of a steering sensor 11, and sets a target revolution speed of the electric motor 27 based on the found steering angle speed and the vehicle speed detected by a vehicle speed sensor 13. When malfunction is generated in the vehicle sensor 13 or the signal line thereof, the electronic control unit 30 calculates the vehicle speed based on outputs of an engine speed detection part 16 and a gear ratio detecting part 17 (for detecting a gear ratio of a transmission), and the target revolution speed of the electric motor 27 is set based on the calculated vehicle speed.

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 using an electric motor as a source of a steering assist force.

[0002]

2. Description of the Related Art A power steering system using an electric motor as a source of a steering assist force has a structure in which an output torque of the electric motor is transmitted to a steering mechanism by a mechanical transmission means such as a gear mechanism. There is a hydraulic type that transmits the generated hydraulic pressure of the driven oil pump to the steering mechanism. In any case, the drive target value of the electric motor is determined based on the information (steering torque or steering angular velocity) related to steering by the steering wheel and the vehicle speed information, and the electric motor is set so that the drive target value is achieved. Is driven. As a result, appropriate steering assistance can be realized. In particular, by determining the drive target value of the electric motor based on the vehicle speed information, it is possible to increase the steering assist force during low-speed traveling when the steering resistance increases and decrease the steering assist force during high-speed traveling when the steering resistance decreases. , Appropriate vehicle speed response control can be performed.

If a vehicle speed sensor for detecting vehicle speed information has a failure or a signal line of the vehicle speed sensor has a failure such as a disconnection, the vehicle speed sensitive control cannot be properly performed. Therefore, an electronic control unit (ECU) for the power steering device executes an abnormality monitoring process for detecting an abnormality in the vehicle speed sensor signal. When an abnormality in the vehicle speed sensor signal is detected, the electric motor is driven based on the drive target value corresponding to the intermediate vehicle speed range. For example, in a hydraulic power steering device, the electric motor is maintained at a constant rotation speed regardless of the vehicle speed.

[0004]

However, in such control, there is a high possibility that the steering assist force will be excessive or insufficient when the vehicle speed sensor signal is abnormal, and thus there is a problem that proper steering assist is difficult to achieve. . Therefore, the object of the present invention is to
It is an object of the present invention to solve the above-mentioned technical problem and to provide a power steering device capable of performing appropriate steering assistance according to a vehicle speed even when an abnormality occurs in the vehicle speed detection means or a signal line thereof.

[0005]

In order to achieve the above-mentioned object, the invention according to claim 1 uses an electric motor (27) as a source of a steering assist force to a steering mechanism (1) to assist steering. A power steering device for applying force, comprising steering detecting means (11) for detecting steering by an operating member (2) for steering a vehicle, vehicle speed detecting means (13) for detecting the speed of the vehicle, An engine speed detecting means (16) for detecting an engine speed of the vehicle, a gear ratio detecting means (17) for detecting a gear ratio of a transmission portion of the vehicle, and a failure of the vehicle speed detecting means or a signal line thereof. Vehicle speed calculation means (31, S2) for calculating the vehicle speed of the vehicle based on the outputs of the engine speed detection means and the gear ratio detection means.
S9), and when the failure detecting means does not detect the failure, the electric motor is drive-controlled based on the outputs of the steering detecting means and the vehicle speed detecting means in the normal state, and the failure detecting means detects the failure. The power steering device is characterized in that it sometimes includes motor control means (31, S1 to S12) for driving and controlling the electric motor based on the outputs of the steering detection means and the vehicle speed calculation means.
The alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies in this section below.

According to the above construction, if there is no abnormality in the vehicle speed detecting means or the signal line thereof, the electric motor is controlled based on the vehicle speed detected by the vehicle speed detecting means, while a failure occurs in any of them. Then, the electric motor is controlled based on the vehicle speed calculated by the vehicle speed calculation means. The vehicle speed calculation means is based on the engine speed and the gear ratio of the transmission without depending on the vehicle speed detection means.
Calculate the theoretical value of vehicle speed.

In this way, the so-called vehicle speed response control can be continued even if the vehicle speed detecting means or the signal line thereof fails, so that there is no excess or deficiency in the steering assist force and good steering is achieved. The feeling can be maintained. The invention according to claim 2 further includes a failure state memory (34) in which failure information indicating this is written when the failure detection means detects a failure of the vehicle speed detection means or a signal line thereof, and the motor The control means includes means (YES in S0) for prohibiting activation of the electric motor when the failure information is written in the failure state memory when the engine of the vehicle is started. It is the described power steering apparatus.

According to this structure, when a failure occurs in the vehicle speed detecting means or the signal line thereof, failure information indicating the failure is written in the failure state memory. If the failure state information is written in the failure state memory when the engine is started, starting of the electric motor is prohibited and steering assist is not performed. As a result, the driver can immediately recognize that a failure has occurred, and can immediately take measures such as repair.

[0009]

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 an embodiment of the present invention. The 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.

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 that extends in the left-right direction of the vehicle. Rack shaft 5
Tie rods 6 are connected to both ends of the tie rods 6, respectively. The tie rods 6 are connected to knuckle arms 7 that support front left and right wheels FL and FR as steered wheels. The knuckle arm 7 is provided rotatably around the kingpin 8.

With this configuration, the steering wheel 2
Is operated to rotate the steering shaft 3, 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
The knuckle arm 7 is converted into a rotation around the king pin 8, whereby steering of the front left and right wheels FL and FR is achieved. The steering wheel 2 is attached to the steering shaft 3.
The torsion bar 9 that causes a twist in accordance with the direction and the magnitude of the steering torque applied thereto and the hydraulic control valve 23 whose opening changes according to the direction and the magnitude of the torsion of the torsion bar 9 are incorporated. . The hydraulic control valve 23 is
It is connected to a power cylinder 20 that gives 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, 20 partitioned by the piston 21.
b, the cylinder chambers 20a, 20b are connected to the hydraulic control valve 23 via oil supply / return paths 22a, 22b, respectively.

The hydraulic control valve 23 further includes an oil circulation path 24 passing through a reservoir tank 25 and an oil pump 26.
Is installed in the middle of the. The oil pump 26 is driven by an electric motor 27 to drive the reservoir tank 25.
The hydraulic fluid stored in the hydraulic control valve 23 is pumped out and supplied to the hydraulic control valve 23. The surplus hydraulic oil is returned from the hydraulic control valve 23 to the reservoir tank 25 via the oil circulation path 24. When the torsion bar 9 is twisted in one direction, the hydraulic control valve 23 controls the oil supply / return path 22.
The hydraulic oil is supplied to one of the cylinder chambers 20a and 20b of the power cylinder 20 through one of the a and 22b. Further, when the torsion bar 9 is twisted in the other direction, the oil supply / return paths 22a and 22b.
The hydraulic oil is supplied to the other of the cylinder chambers 20a and 20b via the other of the above. When the torsion bar 9 is hardly twisted, the hydraulic control valve 23
Is, so to speak, an equilibrium state, and the hydraulic oil is the power cylinder 2
It is circulated in the oil circulation path 24 without being supplied to zero.

When hydraulic oil is supplied to one of the cylinder chambers of the power cylinder 20, the piston 21 moves in the vehicle width direction. As a result, the steering assist force acts on the rack shaft 5. An example of the configuration related to the hydraulic control valve 23 is disclosed in detail in Japanese Patent Laid-Open No. 59-18577. The electric motor 27 is, for example, a brushless motor, and is controlled by an electronic control unit (ECU) 30 for power steering via a drive circuit 28. The drive circuit 28 includes, for example, a bridge circuit of power transistors, and supplies the electric power from the vehicle-mounted battery 40 as a power source to the electric motor 27 according to the control signal given from the electronic control unit 30.

The electronic control unit 30 includes a vehicle-mounted battery 4
0 includes a microcomputer that operates by receiving a power supply from 0, and this microcomputer includes a CPU 31
And a RAM 3 that provides a work area for the CPU 31
2, an ROM 33 that stores an operation program of the CPU 31, data for control, and the like, and an EEPROM (Electrically Erasable Programmable Reservoir) that is a nonvolatile memory.
ad Only Memory) 34, CPU 31, RAM 32, R
Bus 3 interconnecting OM33 and EEPROM 34
5 and.

The electronic control unit 30 includes a steering angle sensor 1
The rudder angle data output from 1 is given. The steering angle sensor 11 is provided in association with the steering wheel 2, and 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", The 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 corresponding to the time differential value based on the steering angle data.

The electronic control unit 30 is further provided with a current detection signal from the current detection circuit 12 for detecting the current flowing through the electric motor 27 and a rotation speed signal from the rotation sensor 15 for detecting the rotation of the rotor of the electric motor 27. And are to be given. The rotation sensor 15 is, for example,
It may be a hall sensor (usually plural) built in a brushless motor as the electric motor 27. 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,
Further, the vehicle speed may be calculated based on the output pulse of the wheel speed sensor provided in association with the wheel.

In addition, the electronic control unit 30 includes an engine speed detecting section 1 for detecting the speed of the engine of the vehicle.
6. Gear ratio detector 17 for detecting gear ratio of transmission and ignition (IG) key switch 18
The output signal from is input. Electronic control unit 3
0 controls the drive of the electric motor 27 based on the steering angle data, the current data, and the vehicle speed data provided from the steering angle sensor 11, the current detection circuit 12, and the vehicle speed sensor 13, respectively. Furthermore, the signals from the engine speed detection unit 16 and the gear ratio detection unit 17 are used for drive control of the electric motor 27 as needed.

FIG. 2 is a block diagram showing an actual connection state related to the electronic control unit 30 for power steering. An in-vehicle network 60 formed of an optical fiber cable or the like is formed in the vehicle. The power steering electronic control unit 30, the steering angle sensor 11, the vehicle speed sensor 13, the engine speed detection unit 16, and the main electronic control unit 50 are connected to the in-vehicle network 60. The main electronic control unit 50 controls the engine and the like. In this main electronic control unit 50,
An alternator 19, an ignition key switch 18, and a gear ratio detector 17 are connected.

Electronic control unit 3 for power steering
0 indicates the steering angle sensor 1 via the in-vehicle network 60.
1. Receives signals from the vehicle speed sensor 13, the engine speed detector 16, the gear ratio detector 17, and the ignition key switch 18. FIG. 3 is a characteristic diagram showing a correspondence relationship between the steering angular velocity 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 the first threshold value VT1 and the second threshold value VT2 set for the steering angular speed Vθ (corresponding to the steering speed) (in this embodiment, increases linearly). ) Like
It 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 to the standby rotation speed, and for the steering angular speed less than the first threshold value VT1, the electric motor 27 is rotationally driven at the standby rotation speed R1.

Based on the vehicle speed, the CPU 31 variably sets the inclination of the target rotation 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 target rotation speed R is set smaller as the vehicle speed increases, and the steering assist force decreases.
In this way, vehicle speed responsive control for generating an appropriate steering assist force according to the vehicle speed is performed.

FIG. 4 is a flow chart for explaining drive control of the electric motor 27 by the electronic control unit 30. In FIG. 4, the vehicle speed sensor 13 or the signal line 13a (see FIG. 2) of the vehicle speed sensor 13 is broken (disconnection,
Processing for control related to a failure such as a short circuit is also shown. The CPU 31 of the electronic control unit 30 repeatedly executes the processing shown in FIG. 4 every control cycle. First,
The CPU 31 refers to the EEPROM 34 and determines whether or not failure information indicating that a failure has occurred is written in the vehicle speed sensor 13 or the vehicle speed signal line 13a (step S0), and the failure information having the content is written. If so (YES in step S0), the process ends without starting the electric motor 27. That is, the electric motor 2
7 startup is prohibited.

If the failure information is not written in the EEPROM 34, the vehicle speed signal from the vehicle speed sensor 13 is read (step S1), and it is determined whether or not there is an abnormality in this vehicle speed signal (step S2). If there is no abnormality in the vehicle speed signal (NO in step S2), the steering angle speed is calculated based on the output signal of the steering angle sensor 11 (step S3). Further, the CPU determines the target rotation speed R of the electric motor 27 based on the vehicle speed and the steering angular speed according to the characteristics shown in FIG. 3 (step S4), and outputs the current detection circuit 12 so that the target rotation speed R is achieved. Based on the electric motor 2
7 is feedback-controlled (step S5).

On the other hand, when it is determined that the vehicle speed signal has an abnormality (YES in step S2), the CPU 31 stores in the EEPROM 34 failure information indicating that the vehicle speed sensor 13 or its signal line 13a has an abnormality. Write (step S6). Thereafter, the CPU 31 reads the engine speed detected by the engine speed detector 16 without referring to the output of the vehicle speed sensor 13 (step S7),
Further, the gear ratio of the transmission detected by the gear ratio detector 17 is read (step S8). CPU31
The theoretical vehicle speed is calculated by multiplying the read engine speed and gear ratio (step S9).

Based on the vehicle speed calculated above and the steering angular speed calculated based on the output of the steering angle sensor 11 (step S10), the CPU 31 follows the characteristics of FIG. The speed R is set (step S11), and drive control of the electric motor 27 is executed (step S12). After that, the processes of steps S6 to S12 are repeated until the engine is stopped (step S13). The stop of the engine is detected by a signal from the ignition key switch 18.

After the engine is stopped, when the ignition key switch 18 is turned on again to start the engine, the CPU 31 refers to the EEPROM 34 (step S0). At this time, if the EEPROM 34 stores failure information indicating a failure of the vehicle speed sensor 13 or its signal line (YES in step S9), the electric motor 27 is not activated. That is, since the steering assistance is not provided, the driver can immediately recognize the occurrence of the failure and can take appropriate measures such as repair.

As described above, according to this embodiment, when a failure occurs in the vehicle speed sensor 13 or the vehicle speed signal line 13a, the theoretical vehicle speed is calculated based on the engine speed and the transmission gear ratio. Vehicle speed response control is performed based on the determined vehicle speed. This allows
Even if a failure occurs in the vehicle speed sensor 13 or the like, an appropriate steering assist force can be applied to the steering mechanism 1,
A good steering feeling can be maintained.

Moreover, when restarting the engine,
Since no steering assist force is generated, it is possible to reliably notify the driver of the fact that a failure has occurred.
There is no risk of being left in a faulty state. Although one embodiment of the present invention has been described above, the present invention can be implemented in other forms. For example, in the above-described embodiment, the hydraulic power steering device that transmits the hydraulic pressure generated from the oil pump driven by the electric motor to the steering mechanism is taken as an example, but as long as so-called vehicle speed sensitive control is performed. The present invention can also be applied to a power steering device configured to mechanically transmit a torque generated by an electric motor to a steering mechanism via a gear mechanism or the like.

In the above embodiment, the electronic control unit 30 for power steering detects a failure based on the abnormality of the vehicle speed signal. However, any electronic control unit connected to the in-vehicle network 60 ( For example, the abnormality of the vehicle speed signal is detected in the main electronic control unit 50), and when the abnormality of the vehicle speed signal is detected, the failure information indicating the abnormality is read into the electronic control unit 30 via the in-vehicle network 60. May be

Besides, various design changes can be made within the scope of the matters described in the claims.

[Brief description of 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 showing an actual connection state related to an electronic control unit for power steering.

FIG. 3 is a characteristic diagram showing a correspondence relationship between a steering angular velocity calculated based on a steering angle signal and a target rotation speed of an electric motor.

FIG. 4 is a flowchart for explaining drive control of an electric motor by an electronic control unit.

[Explanation of symbols]

1 Steering mechanism 2 steering wheel 11 Rudder angle sensor 12 Current detection circuit 13 vehicle speed sensor 13a Vehicle speed signal line 16 Engine speed detector 17 Gear ratio detector 18 ignition key switch 20 power cylinder 21 pistons 23 Hydraulic control valve 26 Oil pump 27 electric motor 28 Drive circuit 30 Electronic control unit for power steering 31 CPU 32 RAM 33 ROM 34 EEPROM 60 Car network

Claims (2)

[Claims] 1. A power steering device for applying a steering assist force to a steering mechanism using an electric motor as a source of steering assist force, comprising: steering detecting means for detecting steering by an operating member for steering a vehicle; Vehicle speed detecting means for detecting the speed of the vehicle, engine speed detecting means for detecting the engine speed of the vehicle, gear ratio detecting means for detecting the gear ratio of the transmission portion of the vehicle, and the vehicle speed detecting means or its signal line. Failure detecting means for detecting the failure of the vehicle, vehicle speed calculating means for calculating the vehicle speed of the vehicle based on the outputs of the engine speed detecting means and the gear ratio detecting means, and the failure detecting means not detecting the failure. At times, the electric motor is drive-controlled based on the outputs of the steering detection means and the vehicle speed detection means, and the failure detection means detects a failure. A power steering apparatus comprising: a motor control unit that drives and controls the electric motor based on the outputs of the steering detection unit and the vehicle speed calculation unit when an abnormality occurs. 2. When the failure detecting means detects a failure of the vehicle speed detecting means or a signal line thereof, a failure state memory in which failure information indicating this is further written is further included, and the motor control means of the vehicle. 2. The power steering apparatus according to claim 1, further comprising means for prohibiting activation of the electric motor when the failure information is written in the failure state memory when the engine is started.