JP2007245827A - Power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering system hard to erroneously detect sky failure/ground failure by electromagnetic noise. <P>SOLUTION: This power steering system is furnished with a steering speed detection means to detect steering speed in accordance with the number of pulse signals given after pulled up and pulled down through a resistor R1 from a steering angle detection means (not shown in the drawing) to revolve with a steering member (not shown in the drawing) and a failure detection means 27 to detect failure of the steering speed detection means 24 when the pulse signal slips out of a specified voltage range and assists steering by hydraulic pressure generated by an oil pump (not shown in the drawing) driven by the electric motor M by rotating and controlling the electric motor M in accordance with the steering speed detected by the steering speed detection means 24. It is also constituted by furnishing a means 25 to detect temperature in the neighborhood of the resistor R1 and changing means 26, 27 to change the voltage range in accordance with the temperature detected by the means 25. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power steering device that controls rotation of an electric motor based on a steering speed and assists steering by hydraulic pressure generated by an oil pump driven by the electric motor.

  Recently, hydraulic power steering devices that supply hydraulic oil from an oil pump to a power cylinder coupled to a steering mechanism of a vehicle and generate a steering assist force from the power cylinder have become widespread. In such a power steering apparatus, in order to obtain an optimum steering assist force, an instruction rotational speed to the electric motor is determined according to a motor rotational speed map as shown in FIG. 4 determined by the steering speed and the vehicle speed (vehicle speed). is doing.

The steering speed is the number of pulses (sequence) signals as shown in FIG. 5 per predetermined time from a steering angle detecting means that rotates together with the steering wheel (steering member, steering wheel), for example, a steering angle sensor having a rotary encoder. It is obtained by counting. Each voltage value of the ON voltage / OFF voltage of the pulse signal is set lower (eg, 4V) / higher (eg, 1V) than the power supply voltage / ground voltage so that it can be distinguished from the power supply voltage (eg, 5V) / ground voltage (0V). Therefore, it is configured so that a power fault / ground fault can be detected quickly. The threshold value for detecting the power fault / ground fault is set to 4.5V / 0.5V, for example, and when the threshold value is greater than or less than these threshold values, the power fault / ground fault is detected. Is determined.
Further, in order to stabilize the input voltage of the pulse signal to the electronic control unit and prevent the influence of electromagnetic wave noise, the pulse signal is pulled up by a resistor R1 as shown in FIGS.

Patent Document 1 discloses a fail-safe control mechanism that performs appropriate fail-safe control according to an actual driving situation by making a threshold value and an abnormality determination time variable according to conditions.
Patent Document 2 discloses a fail-safe control mechanism that performs an appropriate fail-safe control according to an actual traveling situation by making the abnormality determination time variable according to conditions.
Patent Document 3 discloses a fail-safe control mechanism that performs appropriate fail-safe control according to an actual traveling situation by making a threshold variable according to conditions.

In Patent Document 4, when the steering assist direction corresponding to the target drive value set based on the steering torque is different from the direction of the steering torque, if the absolute value of the target drive value is equal to or greater than the control abnormality determination threshold value, steering is performed. An electric power steering apparatus that is configured to prohibit driving of the auxiliary motor and changes the control abnormality determination threshold according to the vehicle speed is disclosed.
JP 2005-8106 A JP 2005-8105 A JP 2004-299616 A JP 2004-217084 A

The power steering device is installed in an engine room that is at a high temperature (around 100 ° C.). For this reason, the temperature of the resistor R1 also increases from the start, and the resistance value increases. When the resistance value of the resistor R1 increases, the voltage value of the pulled-up pulse signal decreases and the difference from the threshold value for detecting a ground fault becomes small. There is a problem that the threshold value is exceeded due to external noise, and a fault is easily detected by mistake. In addition, when the pulse signal is pulled down, the voltage value of the pulse signal increases as the resistance value of the pull-down resistor increases, and the difference from the threshold for detecting a power fault is reduced. The ON signal exceeds the threshold value due to external noise such as electromagnetic noise, and it is easy to detect a fault by mistake.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a power steering device in which a power fault / ground fault is hard to be erroneously detected by electromagnetic noise.

  A power steering apparatus according to a first aspect of the present invention is a steering speed detecting means for detecting a steering speed based on the number of pulse signals applied by pulling up or pulling down through a resistor from a steering angle detecting means that rotates together with a steering member. A failure detecting means for detecting a failure of the steering speed detecting means when the pulse signal is out of a predetermined voltage range, and controlling the rotation of the electric motor based on the steering speed detected by the steering speed detecting means. In the power steering apparatus that assists steering by the hydraulic pressure generated by the oil pump driven by the electric motor, the voltage range is changed based on the means for detecting the temperature near the resistance and the temperature detected by the means. And a changing unit.

  In the power steering apparatus according to a second aspect of the present invention, the changing means includes a reference table in which the temperature and the voltage range are associated with each other based on a temperature characteristic of the resistor, and changes according to a reference result of the reference table. It is comprised by these.

  According to the power steering device of the first aspect of the present invention, the steering speed detecting means determines the steering speed based on the number of pulse signals that are supplied from the steering angle detecting means that rotates together with the steering member. When the pulse signal is out of the predetermined voltage range, the failure detection means detects a failure of the steering speed detection means, detects the temperature near the resistance, and the change means detects the voltage range based on the detected temperature. Therefore, it is possible to realize a power steering device in which a power fault / ground fault is hard to be erroneously detected due to external noise such as electromagnetic noise.

  According to the power steering device of the second aspect of the invention, the changing means is such that the reference table associates the temperature with the voltage range based on the temperature characteristic of the resistance, and changes according to the reference result of the reference table. / A power steering device can be realized in which a ground fault is difficult to be detected erroneously due to electromagnetic noise.

The present invention will be described below with reference to the drawings showing embodiments.
(Embodiment)
FIG. 1 is an explanatory view schematically showing a main part configuration of an embodiment of a power steering apparatus according to the present invention. This power steering device assists steering in a steering mechanism 1 of a vehicle, and a steering shaft 3 is connected to a steering wheel 2. A pinion 4 is attached to the tip of the steering shaft 3, and the pinion 4 meshes with a rack shaft 5 that extends in the vehicle width direction. A steering wheel 7 is attached to the rack shaft 5 via a tie rod 6.

The rack shaft 5 is also connected with a piston 11 of a power cylinder 10, and the power cylinder 10 includes a pair of cylinder chambers 10 a and 10 b formed by the piston 11. A hydraulic control valve 13 is connected to the cylinder chambers 10a and 10b through oil supply paths 12a and 12b indicated by broken lines, respectively.
The hydraulic control valve 13 is connected in the middle of an oil circulation path 14 indicated by a broken line, and the hydraulic oil stored in the reservoir tank 15 is pumped out by the oil pump 16 and pumped out. After the hydraulic oil is discharged from the oil pump 16, it is configured to return to the reservoir tank 15 again.
When the oil pump 16 is driven by the electric motor M, the hydraulic oil circulates through the oil circulation path 14, and when it is not driven, the circulation of the hydraulic oil is stopped.

  The opening of the hydraulic control valve 13 changes according to the direction and magnitude of the torque applied to the steering shaft 3, thereby changing the supply state of hydraulic oil to the power cylinder 10. When hydraulic oil is supplied to the cylinder chamber of the power cylinder 10, the piston 11 reciprocates in the direction along the vehicle width direction, whereby a steering assist force is generated and the steering force required to move the rack shaft 5 is reduced. Assisted.

The vehicle speed sensor 18 detects the rotational speed of the rotor of the steered wheel 7, and a magnetic or optical sensor can be used. A vehicle speed signal V which is a detection signal of the vehicle speed sensor 18 is given to the electronic control unit ECU.
The steering shaft 3 is provided with a steering angle sensor (steering angle detecting means) 8 for detecting the steering angle of the steering wheel 2, and a pulse signal S of the steering angle sensor 8 is given to the electronic control unit ECU.
The steering angle sensor 8 may be a magnetic or optical sensor, a rotary encoder, or a gear. In this embodiment, a steering angle sensor using a rotary encoder will be described.

The electric motor M is provided with a rotation speed sensor 17 for detecting the rotation speed (rotation speed) of the electric motor M, and the rotation speed detected by the rotation speed sensor 17 is given to the electronic control unit ECU.
The electronic control unit ECU determines the command rotational speed based on the supplied pulse signal S and vehicle speed signal V, and drives the electric motor M based on the deviation between the command rotational speed and the rotational speed detected by the rotational speed sensor 17. The circuit 19 is feedback controlled to drive the electric motor M, thereby driving the oil pump 16.

  In the power steering device having such a configuration, when the steering wheel 2 is operated and the rotational force is transmitted to the steering shaft 3, the pinion 4 at the tip thereof rotates, whereby the rack shaft 5 moves in the vehicle width direction. Move to. As a result, the amount of movement of the rack shaft 5 is transmitted to the tie rod 6 and the direction of the steering wheel 7 changes. The power cylinder 10 generates an auxiliary force to be applied to the rack shaft 5 when the rack shaft 5 moves in the vehicle width direction.

  FIG. 2 is a block diagram illustrating a configuration example of the electronic control unit ECU, the drive circuit 19, the electric motor M, and the rotation speed sensor 17 described above. In the electronic control unit ECU, the steering speed calculation unit 24 (steering speed detecting means) is supplied with a pulse (sequence) signal S as shown in FIG. 5 from the steering angle sensor 8 having a rotary encoder through the diode D. A steering speed is calculated based on the number of pulse signals S per predetermined time, and the steering speed signal Vθ is given to the motor rotation speed map 20. A vehicle speed signal V from the vehicle speed sensor 18 is given to the motor rotation speed map 20.

  The pulse signal S is pulled up to a 5V power source by a resistor R1, and is also given to the failure detection unit 27 (failure detection means, change means). The failure detection unit 27 sets a threshold value for detecting a power fault / ground fault in the steering angle sensor 8 system, for example, 4.5V / 0.5V, and when these threshold values are exceeded Detects a power fault / ground fault and outputs a fault signal.

The temperature detector 25 detects the temperature in the vicinity of the resistor R1, and the detected temperature is given to the failure detection voltage map 26 (changing means, reference table). The temperature detection unit 25 may be provided outside the electronic control unit ECU.
The failure detection voltage map 26 records a reference map that defines the relationship between the temperature and the voltage value for detecting a ground fault as shown in FIG. 6, and corresponds to the temperature given from the temperature detection unit 25. The obtained voltage value is given to the failure detection unit 27. The failure detection unit 27 updates the voltage value for detecting a ground fault by the given voltage value.

The motor rotation speed map 20 records a reference map that defines the relationship between the steering speed, the vehicle speed, and the motor rotation speed, as shown in FIG. 4, and according to the given steering speed signal Vθ and the vehicle speed signal V, The instruction rotational speed to the electric motor M is output and given to the deviation calculator 21.
The rotation speed detected by the rotation speed sensor 17 of the electric motor M is given to the deviation calculation unit 21, and the deviation calculation unit 21 calculates the deviation by subtracting the rotation speed from the command rotation speed and gives it to the PI control unit 22. .
The PI control unit 22 calculates a control signal for performing PI control based on the given deviation, and provides it to the PWM circuit 23.
The PWM circuit 23 drives the electric motor M by outputting a pulse signal having a pulse width corresponding to the given control signal.

FIG. 3 is a circuit diagram showing a connection example of the electronic control unit ECU and the steering angle sensor 8 described above. The steering angle sensor 8 supplies an on / off signal from a built-in rotary encoder to the base of the NPN transistor Tr. The emitter of the transistor Tr is grounded through a resistor R2, and the collector is connected to the cathode of a diode D for backflow prevention and is grounded through a resistor R3.
The diode D is built in the electronic control unit ECU, and its anode is connected to the 5V power source through the resistor R1 and is connected to each input terminal of the steering speed calculation unit 24 and the failure detection unit 27.

  In the electronic control unit ECU and the steering angle sensor 8 having such a configuration, the voltage of the pulse signal S is a distribution of the power supply voltage 5V and the combined resistance (R2 / R3 / (R2 + R3)) of the resistors R1 and R3 and R2. Voltage. When an off signal is given from the rotary encoder to the base of the transistor Tr, the pulse signal S becomes a voltage divided by the resistance R1 and the resistance R3 of the power supply voltage 5V and becomes an on signal. When an ON signal is given from the rotary encoder to the base of the transistor Tr, the pulse signal S becomes a divided voltage of the resistance R1 of the power supply voltage 5V and the combined resistance R2 / R3 / (R2 + R3), and becomes an OFF signal.

The pulse signal S is provided to the steering speed calculation unit 24 and the failure detection unit 27. The steering speed calculation unit 24 calculates the steering speed Vθ from the number of the given pulse signals per predetermined time, and the motor rotation speed map 20 To give.
The motor rotation speed map 20 outputs an instruction rotation speed to the electric motor M in accordance with the given steering speed signal Vθ and vehicle speed signal V, and gives it to the deviation calculation unit 21.
The deviation calculating unit 21 calculates the deviation by subtracting the rotation speed detected by the rotation speed sensor 17 from the indicated rotation speed, and provides the calculated value to the PI control unit 22.
The PI control unit 22 calculates a control signal for performing PI control based on the given deviation, and provides it to the PWM circuit 23.
The PWM circuit 23 outputs a pulse signal having a pulse width corresponding to the given control signal, turns on / off the drive circuit 19, and drives the electric motor M.

On the other hand, the pulse signal S is also given to the failure detection unit 27, and the failure detection unit 27 has the voltage values of the ON signal / OFF signal of the pulse signal S exceeding the threshold values set in the failure detection voltage map 26. Detects a power fault / ground fault and outputs a fault signal.
Further, the temperature detector 25 detects the temperature near the resistor R 1, and the detected temperature is given to the failure detection voltage map 26. The failure detection voltage map 26 gives a voltage value corresponding to the given temperature to the failure detection unit 27. The failure detection unit 27 updates the voltage value for detecting a ground fault by the given voltage value.

  Here, when the temperature of the resistor R1 rises and the resistance value increases, the voltage value of the pulled-up pulse signal S decreases, and the difference from the threshold for detecting a ground fault becomes small. Faults are easily detected by mistake due to external noise. Therefore, as shown in FIG. 6, the failure detection voltage map 26 is set so that the voltage value for detecting a ground fault decreases as the temperature increases. In this case, the failure detection unit 27 keeps the voltage value for detecting the power supply fault as it is or updates it so as to lower it.

  On the contrary, when the pulse signal is pulled down, if the resistance value of the pull-down resistor increases, the voltage value of the pulse signal rises and the difference from the threshold for detecting a power fault is reduced. Faults are easily detected by mistake due to external noise such as electromagnetic noise. In this case, the failure detection voltage map 26 is set so that the voltage value for detecting the power fault becomes higher as the temperature rises, and the fault detection unit 27 detects the power fault. Update the voltage value of. In this case, the failure detection unit 27 keeps the voltage value for detecting the ground fault as it is or updates it so as to increase it.

It is explanatory drawing which shows typically the principal part structure of embodiment of the power steering device which concerns on this invention. It is a block diagram which shows the structural example of the electronic control unit shown in FIG. 1, a drive circuit, an electric motor, and a rotational speed sensor. It is a circuit diagram which shows the example of a connection of the electronic control unit and steering angle sensor which are shown in FIG. It is a characteristic view showing an example of a motor rotation speed map. It is explanatory drawing which shows the example of the pulse (sequence) signal which a steering angle sensor outputs. It is explanatory drawing which shows the example of the reference map which defined the relationship between the temperature recorded on the failure detection voltage map, and the voltage value for detecting a ground fault.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Steering mechanism, 2 Steering wheel, 3 Steering shaft, 4 Pinion, 5 Rack shaft, 8 Steering angle sensor (steering angle detection means, rotary encoder), 10 Power cylinder, 11 Piston, 13 Hydraulic control valve, 16 Oil pump, 19 Drive circuit, 20 motor rotation speed map, 22 PI control section, 23 PWM circuit, 24 steering speed calculation section (steering speed detection means), 25 temperature detection section (means for detecting temperature), 26 failure detection voltage map (change means) , Reference table), 27 failure detection unit (failure detection means, change means), ECU electronic control unit, M electric motor, R1-R3 resistance, Tr transistor

Claims (2)

Steering speed detecting means for detecting a steering speed based on the number of pulse signals applied by pulling up or pulling down through a resistor from a steering angle detecting means that rotates together with the steering member, and the pulse signal has a predetermined voltage range. An oil pump that includes a failure detection unit that detects a failure of the steering speed detection unit when it is disconnected, and that controls the rotation of the electric motor based on the steering speed detected by the steering speed detection unit and that is driven by the electric motor In the power steering device that assists steering by the hydraulic pressure generated by
A power steering apparatus comprising: means for detecting a temperature near the resistor; and changing means for changing the voltage range based on the temperature detected by the means.   2. The change unit according to claim 1, further comprising: a reference table in which the temperature and the voltage range are associated with each other based on a temperature characteristic of the resistor, and the change unit is configured to change the reference table according to a reference result of the reference table. Power steering device.

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