JPS63242771A - Electric type power steering device - Google Patents

Abstract

PURPOSE:To prevent production of assist torque opposite to steering torque, by a method wherein, when the direction of steering torque by a torque detector becomes opposite to that of assist torque outputted by an electric motor, the flow of a current to the electric motor is disconnected by means of a current cut-off means. CONSTITUTION:An output signal from a steering torque detector 6 is inputted to an amplifier 31 for amplification, and an output signal V1 from the amplifier 31 is inputted to the non-reverse input terminal of a differential amplifier 32. A current fed to an electric motor 7 is detected by means of current detector 2 and is amplified by an amplifier 33. An output signal V2 from the amplifier 33 is inputted to the reverse input terminal of the differential amplifier 32. An output signal V3 is inputted to a differential amplifier 32, and an absolute value circuit, by which it is adjusted to the absolute value of a difference between the outputs V1 and V2, is incorporated. The output signal V3 is inputted to the non-reverse input terminal of a comparator 34, and a reference voltage V0 is inputted to the reverse terminal of the comparator 34. A relay 36 of a feed circuit is disconnected by means of an output signal V4 from the comparator 34.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electric power steering system with improved safety.

[Prior art]

Conventionally, steering torque applied to the steering shaft was detected, the rotation of the electric motor was controlled according to the direction and magnitude of the detected steering torque, and the rotation of the electric motor was transmitted to the steering shaft to generate assist torque. An electric power steering device is known.

[Problems to be solved by the invention]

The electric power steering device described above is controlled to reverse the rotational direction of the electric motor depending on the polarity of the output signal of the torque detector. For this reason, even if the output of the torque detector is normal, if the control device is abnormal, the polarity of the output of the torque detector and the direction of rotation of the electric motor will be reversed, making it difficult to operate the steering wheel. . The present invention has been made to solve the above problems, and its purpose is to prevent the electric motor from generating assist torque in the opposite direction to the steering torque due to an abnormality in the control device. The goal is to prevent it from happening.

[Means to solve the problem]

The structure of the invention for solving the above problems is as shown in FIG.
a torque output device 6 that detects the steering torque applied to the steering shaft 8; and an electric motor 7 that generates assist torque to the steering shaft 8.
and a control device 1 that controls the electric motor 7 according to the output of the torque detector 6, a current detector 2 that detects the current flowing through the electric motor 7, and a torque detector 2 that detects the electric current flowing through the electric motor 7; The direction of the steering torque detected by the torque detector 6 and the electric motor 7 are inputted.
A determining means 3 for determining whether the directions of the assist torques outputted by the motors coincide with each other, and a current interrupting means 5 for interrupting the power supply circuit of the electric motor in accordance with the output of the determining means 3 are provided.

[Operation] Steering torque applied to the steering shaft 8 by the driver's steering wheel operation is used to change the direction of the steered wheels 11 and 12 via the rack and pinion gear 10. Torque detector 6 detects torque generated by twisting of steering shaft 8, and its output signal is input to control device 1. Further, the electric motor 7 is driven by the control device 1 to generate assist torque to the steering shaft. The control device 1 rotates the electric motor 7 so as to reduce twisting of the steering shaft 8. Further, the current detector 2 detects the current flowing through the electric motor 7, and the direction of rotation of the electric motor 70 is detected from this detected current. The output signal of the current detector 2 and the output signal of the torque detector 6 are input to a determination means 3, and the determination means 3 determines the direction of the steering torque applied to the steering shaft 8 and the assist torque generated by the electric motor 7. It is determined whether the directions match. On the other hand, a current from a power source 4 is supplied to the electric motor 7 via the control device 1 while being controlled to have a required magnitude and direction. A current interrupting means 5 is disposed in the power supply circuit from the power source 4, and the current interrupting means 5 is connected to the determination circuit 3.
When the direction of the steering torque and the assist torque output from the electric motor 7 are opposite to each other, the electric current supplied to the electric motor 7 is cut off. As a result, if for some reason the direction of the assist torque output by the electric motor 7 becomes opposite to the direction of the steering torque, the rotation of the electric motor 7 is stopped and controlled so that no assist torque is generated.

【Example】

The present invention will be described below based on specific examples. FIG. 2 is a sectional view showing the configuration of the torque detector 6 used in the embodiment device. The steering shaft 8 includes a handle shaft 101, a steering shaft 102, and a torsion bar 103 that connects the two shafts. When the steering wheel 9 rotates, the steering wheel shaft 101 rotates, and the rotational force is transferred to the steering shaft 102 via the torsion bar 103.
transmitted to. At this time, a torsion amount proportional to the manual torque is generated in the torsion bar 103. The steering shaft 102 has a ring portion 104 through which a torsion bar passes, and the end surface of the ring portion 104 on the handle shaft 101 side has an engaging end portion 105 in which a partial circle is cut in the axial direction. have. Engagement end 105
One end 107 of the lever 106 is in contact with the lever 106 . The lever 106 is swingably supported on the handle shaft 101 by a pin 108, and one end 109 of the lever 106 is in contact with one end surface 111 of a movable disc 110. Further, another lever 146 is supported on the handle shaft 101 axially symmetrically with the lever 106 . Movable plate 1. , the other end 113 of 10
A coil spring 114 is in contact with the coil spring, and the other end of the coil spring is in contact with a fixed plate 115. The fixing plate 115 is fixed to the handle shaft 101. A rod 116 is disposed at the end of the movable plate 110 in the direction of the handle shaft 101, and a metal body 117 with high magnetic permeability is attached to the tip of the rod 116. On the other hand, differential transformers 11 and 9 are fixed to the inner surface of the handle column 118, and a metal body 11't and a rod 116 are fitted into the differential transformer 119. In such a configuration, the amount of twist of the steering shaft is detected as the amount of relative displacement of the metal body 117 with respect to the differential transformer 119 in the X-axis direction. The effect will be explained next. When a torsional amount occurs between the handle shaft 101 and the steering shaft 102 in the direction of the arrow a shown in the figure, one end 107 of the lever 106 will move against the engagement end surface 10.
5 receives a reaction proportional to the torque in the direction of arrow a. As a result, the lever 106 moves b around the bin 108.
Rotating in the direction of the arrow, the movable plate 110 is pushed down toward the fixed plate 115 against the urging force of the coil spring 114. For this reason, the lot '116 fixed to the movable plate 110
is displaced in the positive direction of the X-axis with respect to the differential transformer 119. Furthermore, when rotational torque in the opposite direction is applied, the biasing force of the coil spring 114 is applied to the lever 106.
107, and the rod 116 moves in the negative direction of the X-axis. In this way, the magnitude of the steering torque applied to the steering shaft 8 can be detected as the amount of displacement of the movable plate 110 and the rod 116, and hence of the metal body 117. FIG. 3 is a block diagram showing a specific configuration of the control device 1 and the determining means 3. The output signal of the torque detector 6 has a linear relationship with the steering torque Tm' as shown in FIG. 4(a). The output signal is input to the CPU 20 via the interface 21. Further, the CPU 20 inputs a vehicle speed signal (not shown), which is a parameter for changing the characteristics of the assist torque, and a control target value of the steering torque is set according to the signal, and the control target value of the steering torque is set and detected by the torque detector 6. A control signal is output to the drive unit 22 so that the steering torque becomes the control target value. Then, the drive unit 22 controls the magnitude and direction of the current supplied from the power source 4 according to the characteristics shown in FIG. 4(b) according to the control signal, and supplies power to the electric motor.
The steering torque is controlled so as to reach the control target value. Further, the output signal of the torque detector 6 is input to the amplifier 31 and amplified, and the output signal v1 of the amplifier 31 is input to the non-inverting input terminal of the differential amplifier 32. In addition, electric motor 7
The current supplied to the differential amplifier 32 is detected by the current detector 2 and amplified by the amplifier 33, and the output signal v2 of the amplifier 33 is input to the inverting input terminal of the differential amplifier 32. The differential amplifier 32 has a built-in absolute value circuit so that its output signal v3 is the absolute value of the difference between the two human forces v1 and v2. The output signal v3 is input to the non-inverting input terminal of the comparator 34, and the base*m voltage vO output from the reference voltage generator 35 is input to the inverting input terminal of the comparator 34. Here, during normal operation, the output signal v1 of the amplifier 31 and the output signal v1 of the amplifier 33
The gains of these amplifiers are adjusted so that the output signals v2 of the two amplifiers are equal. In addition, a relay 36, which normally has a closed contact, is connected to the power supply circuit from the power source 4 to the drive unit 22.
is provided, and its relay 36 is cut off by the output signal v4 of the comparator 34. Now, when the device is normal, the output signal V3 of the differential amplifier 32 is OV, which is lower than the base voltage vO, so the output signal v4 of the comparator 34 is at a low level, and the relay 36 maintains a conductive state. . However, when the direction of the steering torque detected by the torque detector 6 and the direction of the assist torque are opposite, the output signal v3 of the differential amplifier 32 exceeds the base voltage vO, and the output signal v4 of the comparator 34 becomes Becomes a high level. Then, the relay 36 is activated, the power supply circuit is cut off, and the power supply to the motor 7 is stopped. Therefore, the generation of the assist torque that was intended to be generated in the opposite direction to the steering torque is interrupted, and the problem of heavy steering operation due to an abnormality in the device is resolved. FIG. 5 is a block diagram showing an apparatus according to another embodiment. The difference from the first embodiment described above is that the determining means 3 includes comparators 40 and 41 and EXCLtlSIVI.
It is composed of an E-OR gate 42. The output signal v1 of the amplifier 31 is input to the non-inverting input terminal of the comparator 40, and the inverting input terminal of the comparator 400 is grounded. Therefore, when the output signal v1 of the amplifier 31 is at a positive level, the output signal v5 of the comparator 40 becomes a high level, and when the output signal v1 of the amplifier 31 is at a negative level, the output signal v5 of the comparator 40 becomes a low level. Output signal v of amplifier 31
Since the positive or negative value of 1 indicates the direction of the detected steering torque, the signal level of the output signal V5 of the comparator 40 corresponds to the direction of the steering torque. Similarly, the output signal v2 of the amplifier 33 is input to the non-inverting input terminal of the comparator 41,
The inverting input terminal of comparator 410 is grounded. Therefore, when the output signal v2 of the amplifier 33 is at a positive level, the comparator 4
When the output signal v6 of the amplifier 33 is at a negative level, the output signal v6 of the comparator 41 is at a low level. Since the positive/negative of the output signal v2 of the amplifier 33 indicates the direction of the assist torque output from the electric motor 7, the signal level of the output signal 6 of the comparator 41 corresponds to the direction of the assist torque. Therefore, EXCLUSIV[! which is inputting signal v5 and signal v6] The output signal v7 of the -OR gate 42 becomes a low level when the signal levels of the signal v5 and the signal v6 match, and becomes a high level when the signal levels of the signal 5 and the signal v6 do not match. Then, when the output signal v7 is at a high level, the relay 36 is cut off. That is, the direction of the detected steering torque and the electric motor 7
If the directions of the assist torques output by the motors differ, the power supply current to the electric motor 7 will be cut off. [Effects of the Invention] The present invention includes a current detector that detects the current flowing through the electric motor, an output signal from the torque detector, and a direction of the steering torque detected by the torque detector. I! The present invention includes a determining means for determining whether the directions of assist torques output by the motor match, and a current interrupting means for interrupting the power supply circuit of the electric motor according to the output of the determining means. If a failure occurs in the device such that the direction of the detected steering torque and the assist torque output by the electric motor are opposite, the current supplied to the electric motor is interrupted by the current cutoff means, so that the steering torque is The generation of assist torque in the opposite direction is prevented, improving the safety of the device.

[Brief explanation of drawings]

Figure 'f31 is a block diagram showing the concept of the present invention. FIG. 2 is a sectional view showing the configuration of a torque detector used in an embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the embodiment device. FIG. 4 is a characteristic diagram showing the output characteristics of the torque detector and the power supply characteristics of the electric motor. FIG. 5 is a block diagram showing the configuration of another example device. 8・°°Steering shaft 101・°°Handle shaft 102...''・Steering shaft 103 Torsion bar 105''・Engagement end 106-Lever 110...
Movable disk 114-Coil spring 115-Fixed plate 116-Rod 117...°・Metal body 119-・
・−Differential transformer

Claims (1)

[Scope of Claims] A torque detector that detects steering torque applied to a steering shaft of an automobile, an electric motor that generates assist torque to the steering shaft, and a control device that controls the electric motor according to the output of the torque detector. An electric power steering device comprising: a current detector that detects the current flowing through the electric motor; and an output signal of the torque detector is inputted to detect the direction of the steering torque detected by the torque detector and the output of the electric motor. An electric power steering system comprising: a determining means for determining whether or not directions of assist torques coincide with each other; and a current interrupting means for interrupting a power supply circuit of the electric motor according to an output of the determining means. Device.