JPH0646775Y2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is an electric power system that prevents overcurrent of an auxiliary electric motor at a turning end position of a steering wheel, that is, a so-called steering end, and improves steering response. The present invention relates to a steering device.

[Conventional technology]

In recent years, power steering devices have been widely used in various vehicles for the purpose of reducing steering force. In addition, electric vehicles such as forklifts and trucks that use a battery as a driving source are preferably used for indoor work in factories, ships and the like.
As a power steering device for such a vehicle, an electric device is adopted to save power.

However, the conventional electric power steering device detects an overcurrent of the motor that applies an auxiliary torque to the steering wheel in order to prevent overheating when the motor is locked at the turning end position of the steering wheel, so-called steering end. There was a mechanical contact type overcurrent protection device that temporarily interrupted the current.

[Problems to be solved]

Therefore, when the steering wheel reaches the turning end position, the current to the auxiliary electric motor is cut off as described above, and the responsiveness and steering performance of the steering are significantly reduced even if it is a short time, and the work efficiency is reduced. Was also lowered.

The present invention solves the above problems by flowing an idle current that gives an idle torque equal to or less than the mechanical loss torque of the steering wheel toward the other end position at the turning end position of the steering wheel. It is an object of the present invention to provide an electric power steering device that can be solved.

[Means for solving problems]

 An embodiment of the present invention will be described below with reference to the drawings.

In the figure, an electric power steering apparatus A drives an auxiliary electric motor 5 that rotates a steering wheel W and changes the direction of the steering wheel W by the output of a rotation direction detector 3 that detects an operation of a steering wheel S. Control main circuit 4A that generates drive current
And an idle circuit 9 for generating an idle current that gives an idle torque equal to or less than the mechanical loss torque of the steered wheel W toward the other end position at the turning end position of the steered wheel W. ing.

In this embodiment, the electric power steering apparatus A is used in an electric vehicle such as a so-called battery-powered forklift truck, and the electric vehicle detects an operation of detecting a malfunction of the electric power steering apparatus A. Circuit 6
A traveling safety device B including a motor control circuit 10 for decelerating the traveling electric motor 7 according to the detection signal is provided.

In the present embodiment, the steering wheel W also serves as a driving wheel and forms a drive unit 22 integrated with the traveling electric motor 7 as schematically shown in FIG. 1, and the unit 22 rotates on the vehicle body. It is installed freely. Further, the drive unit 22 meshes with a large-diameter gear 23 fixed to the unit and a gear 25 at the lower end of a steering shaft 24 having a steering wheel S attached to the upper end. Therefore, the steering wheel W can be turned by rotating the steering wheel S. The steering shaft 24 is a chain 2
6. A spline universal joint 27 that is expandable and contractible in the axial direction is interposed, and further, a speed reducer 28 that transmits the rotational torque by driving the auxiliary electric motor 5 and the rotational direction detector 3 are additionally provided.

The rotation direction detector 3 is a torque sensor in the present embodiment, and is substantially proportional to the magnitude of the steering torque applied to the steering wheel S, and the zero potential when the detected torque is zero is the center of the steering wheel S, for example. When the steering direction is right, the potential is positive, and when the steering direction is left, the potential is negative. Therefore, the rotation direction detector 3 detects the operation of the steering wheel S and outputs the direction and magnitude of the steering torque applied to the steering wheel S.

Further, in this embodiment, a pair of left and right turning end detectors 8, 8 for detecting the left and right turning end positions of the steering wheel W are fixed to the vehicle body. In this example, the turning end detector 8 is composed of a micro switch, and is turned on by an actuating piece 21 formed on the side surface of the drive unit 22, so that the left and right turning end detectors 8, 8 respectively turn to the left and right turning end positions. To detect. A rotation meter may be used as the rotation direction detector, and the left and right rotation end positions of the steering wheel W can be detected from the number of rotations or the rotation angle. Therefore, at that time, the rotation end detectors 8, 8 are detected. Can be omitted.

The control main circuit 4A and the idle circuit 9 are the second in this example.
It constitutes the control circuit 4 shown in the figure.

The control main circuit 7 pulse-width-modulates the widening circuit 30 for widening the output of the rotation direction detector 3 and the output 31 of the widening circuit 30.
A PWM circuit 40, a direction determination circuit 50 for determining the rotation direction of the steering wheel S from the output of the rotation direction detector 3, and the PWM
A switching circuit that turns on and off the current from the battery E by the output 41 of the circuit 40 and the outputs 51 and 52 of the direction determination circuit 50.
And 60 to form a so-called chiyhopper control circuit.

The idle circuit 9 is, in the present embodiment, a pulse oscillation circuit 70 that oscillates a narrow pulse, and the direction determination circuit.
Outputs 51 and 52 of 50 and outputs 53 and 54 of the rotation end detectors 8 and 8, respectively.
With the output 71 of the pulse oscillation circuit 70 and the PWM circuit 4
And a switching circuit 100 for switching between the output 41 of 0 and the output 41.

In the present example, the amplification circuit 30 increases the output 32 of the rotation direction detector 3 and outputs a non-linear circuit 33 that cuts off below a certain threshold level and the absolute value of the output 34 of the non-linear circuit 33. And a rectifying circuit 35. The input / output characteristics of the amplification circuit 30 are schematically shown in FIG. 4, and the dead zone between the positive and negative threshold levels forms the play of the steering wheel S. Therefore, the width of the dead zone is determined by the actual vehicle feeling. In order to realize such a characteristic, a silicon rectifier assembled in a bridge is interposed between two OP amplifiers whose gains are appropriately selected, so that the forward voltage of the rectifier can be easily utilized.

As the PWM circuit 40, for example, a well-known circuit such as one using a triangular wave generating circuit and a comparator can be adopted.

The direction determination circuit 50 is the output 34 of the non-linear circuit 33 in this example.
Is input to determine the level, positive or negative in this example, the output 51 becomes 1 when the steering direction of the steering wheel S is right, and the output 52 when the steering direction is left.
Becomes 1. The direction determination circuit 50 can be configured using a comparator or the like.

The turning end detectors 8 and 8 have an output 53 of 1 when the steering wheel W is at the right end position, and also have an output 54 of 1 when the steering wheel W is at the left end position.

The switching circuit 60 is a bridge-connected switching element 61, 62, 63, 64, and a drive circuit 65 for driving the switching element 61, 63 and the switching element 62, 64, which are located diagonally and form a pair, respectively. It consists of 66 and. The auxiliary electric motor 5 is connected to the middle side of the bridge. The switching elements 61 and 62 are connected to the battery E via the key switch KS, and the switching elements 63 and 64 are connected to the ground. Therefore, by inputting a pulse to the drive circuit 65, the switching elements 61 and 63 are rendered conductive, and the auxiliary electric motor 5 has a current flowing in a direction for turning the steered wheels W to the right. Further, when a pulse is applied to the drive circuit 66, a current flows in the same direction as turning the steering wheel to the left. In this embodiment, power MOS-FETs are connected in parallel and used as the switching elements 61-64.

The pulse oscillation circuit 70 outputs a rectangular wave having a narrow pulse width as described above and substantially the same frequency as the PWM circuit 40.
The pulse width is set so that the idle torque applied to the steering wheel W by the auxiliary electric motor 5 when the pulse is input to the drive circuit 65 or 66 is equal to or less than the mechanical loss torque of the steering wheel W. In other words, the steering wheel W is set in a range in which the steering wheel W is not turned by idle torque even when the steering wheel W is floated from the ground.

The switching circuit 100 is a logic circuit that selects the PWM circuit 40 or the pulse oscillation circuit 70 according to the outputs 51 to 54 of the direction determination circuit 50 and the rotation end detectors 8 and 8 and inputs it to the switching circuit 60. The operation will be described with reference to.

When the steering wheel W is not at the left and right turning end positions, the outputs 53 and 54 of the turning end detectors 8 and 8 are both 0. Therefore, the AND circuits 101, to which the outputs 53 and 54 are respectively input,
Each output 103, 104 of 102 is zero. Also this output 10
The output 106 of the OR circuit 105 to which 3 and 104 are input is also 0. Therefore, the output 109 of the AND circuit 107 to which the output 106 and the output 71 of the pulse oscillation circuit 70 are input is 0, and the pulse signal of the pulse oscillation circuit 70 does not appear. On the other hand, the output 111 of the NOT circuit 110 that inverts the output 106 and the output 41 of the PWM circuit 40 are input to the output 104 of the AND circuit 103.
Therefore, the pulse signal of the output 41 appears as it is. Therefore, the output 104 of the OR circuit 105 to which the outputs 104 and 109 of the AND circuits 103 and 107 are input is the output 104, that is, the PWM circuit.
40 pulse signals appear.

Further, the output 52 of the turning end detector 8 for detecting the right turning end is inputted to the other input of the AND circuit 101, which reverses the output 52 which becomes 1 when the steering direction is left. Circuit 1
Output 109 of 07 is input. Similarly, the AND circuit 102 inverts the output 51 that becomes 1 when the steering direction is right.
The output 121 of the NOT circuit is input.

Therefore, for example, when the steering wheel W is at the right rotation end position, the output 53 is 1, and when the output 52 is 0, the output 109 is 1, so the output 103 of the AND circuit 101 is 1. That is, when the output 53 is 1 and the output 52 is 0, the steering wheel W is in the right turning end position while the steering wheel W is further applied with the steering torque in the right direction, or the steering wheel S is substantially operated by the steering wheel S. It is in a state like that, further speaking,
It can be said that the steering torque to the left has not been applied yet.
In this state, the output 103 of the AND circuit 101 is 1, the output 106 is 1, and the inverted output 111 is 0. Therefore, in this state, contrary to the above state, the pulse signal of the pulse oscillation circuit 70 appears in the output 109 of the AND circuit 107, and the output 1 of the OR circuit 105
The pulse signal of the pulse oscillation circuit 70 also appears in 06.

Similarly, when the steering wheel W is at the left end position of rotation, the pulse signal of the pulse oscillation circuit 70 appears at the output 106.

On the other hand, the outputs 51 and 52 of the direction determination circuit 50 are AN
It is input to the D circuits 122 and 123, and the other inputs of the AND circuits 122 and 123 have outputs 53 and 54 of the rotation end detectors 8 and 8 respectively.
The outputs 126 and 127 of the NOT circuits 124 and 125 that invert the signal are input. Therefore, the output 129 of the AND circuit 122 becomes 1 only when the steering direction is right and there is no steering wheel W at the right end position. On the contrary, the output 130 of the AND circuit 123 becomes 1 only when the steering direction is left and the steering wheel W is not at the left end position. The output 129 is input to the OR circuit 131 together with the output 54, and the output 130 and the output 53 are input to the OR circuit 132. Therefore OR
The output 133 of the circuit 131 becomes 1 in addition to the above condition that the output 129 becomes 1 in addition to the condition that the output 54 becomes 1, that is, the steering wheel W is located at the left end position. Similarly, the OR circuit 13
The output 134 of 2 becomes 1 because the condition that the output 53 becomes 1 is added to the above condition that the output 130 becomes 1. Also, the AND circuit 140 has an OR
The output 133 of the circuit 131 and the output 106 of the OR circuit 105 are input. The AND circuit 142 outputs the output 134 of the OR circuit 132 and the output 10
6 and are entered. Also, the outputs 141 and 143 of the AND circuits 140 and 142, respectively.
Are input to the drive circuits 65 and 66 of the switching circuit 60, respectively.

Therefore, the output signal of the PWM circuit 40 is input to the AND circuits 140 and 142 when the steered wheels W are between the left and right turning end positions, and when the steering direction is right, the output 133 is output.
Becomes 1 and the output 141 becomes a pulse signal equal to the output signal of the PWM circuit 40. Therefore, in the switching circuit 60, the drive circuit 65 causes the switching elements 61 and 63 to turn on and off,
The auxiliary electric motor 5 generates an auxiliary torque for rotating the steered wheels W rightward. Similarly, when the steering direction is left, the switching elements 62 and 64 are turned on and off, and the auxiliary electric motor 5 generates leftward auxiliary torque. When the steering wheel W reaches the left or right turning end position, the turning end detectors 8, 8
To detect.

When the steering wheel W is at the left or right turning end position,
As described above, the pulse signal of the pulse oscillation circuit 70 appears in the output 106. When the output 133 is 1, that is, the steering wheel W
Is at the left rotation end position, an idle current is generated toward the other right end position and which gives the steering wheel W an idle torque equal to or less than the mechanical loss torque of the steering wheel W.
Similarly, when the steered wheel W is at the right rotation end position, a reverse idle current that gives an idle torque to the other left end position can be generated.

On the other hand, if the conventional device is adopted in the case where the steering wheel and the steered wheels are mechanically coupled by the steering shaft as in this example, the current of the auxiliary electric motor is temporarily cut off at the turning end position as described above. Due to this, the steering torque to the other end temporarily increases, and a catching phenomenon as if mechanically catching occurred. However, in the present device A, when the steering wheel S reaches the turning end position, Since the idle torque toward the other end position is automatically generated, the catching phenomenon can be prevented.

The traveling safety device B includes an operation detection circuit 6 for detecting an operation failure of the electric power steering device A and an electric motor control circuit 10 for decelerating the electric motor 7 for traveling according to the detection signal.
It is equipped with

The operation detection circuit 6 outputs the output 1 of the OR circuit 105 of the control circuit 4.
A shaping circuit 150 that smoothes the pulse signal of 06 into a DC signal of a constant level, an auxiliary motor operation detection circuit 160 that detects the operation of the auxiliary motor 5 by detecting the drive current of the auxiliary motor 5, and the circuit 150. , 160 outputs 151, 161
And a holding circuit 175 for holding an output 171 of the comparison circuit 170.

The auxiliary motor operation detection circuit 160, as shown in FIG.
The shunt resistors 162, 163 inserted between the switching elements 63, 64 and the ground, the operation amplification circuit 164 for increasing the voltage drop between the resistance-side ends of the resistors 162, 163, and the output 165 thereof are input. With a window comparator 166. The window comparator 166 sets the idle current and the overcurrent in the window. That is, the output 169 of the window comparator 166 is the idle current and the auxiliary motor 5
Is 1 when a drive current for generating an effective auxiliary torque flows. And when the current becomes too large,
The output 169 becomes 0 and also has the function of overcurrent protection.

The comparison circuit 170 uses an exclusive OR circuit. Therefore, the output 171 becomes 1 when the current is not flowing through the auxiliary electric motor 5 although the output 106 has the pulse signal from the PWM circuit 40 or the pulse oscillation circuit 70.

Further, the holding circuit 175 uses an RS flip-flop and is connected to the same power supply circuit as the control circuit 4. A power-on reset circuit 176 is connected to the reset terminal R, and the holding circuit 175 is automatically reset when the power is connected to the control circuit 4 and its output 177 becomes 1. The output 171 is input to the set terminal S of the holding circuit 175.

Therefore, the output 177 of the operation detecting circuit 6 becomes 0 when the operation failure of the electric power steering apparatus A is detected.

As shown in FIG. 3, the electric motor control circuit 10 is a tipper control circuit that increases / decreases the drive current of the traveling electric motor 7 according to the operation amount of the accelerator C by the accelerator signal 191 of the accelerator C. A widening circuit 200 to increase the
A PWM circuit 210 that generates a pulse whose pulse width is modulated by its output 201 and a switching circuit 220 including a drive circuit 221 and a chip element 222 are provided.
In addition, the attenuation circuit 2 is provided between the amplification circuit 200 and the PWM circuit 210.
A circuit in which 03 and the normally closed bypass switch 204 are connected in parallel is inserted. Therefore, the output 201 of the amplification circuit 200 is always
Is directly input to the PWM circuit, and the signal of the output 201 attenuated by the attenuation circuit 203 is input to the PWM circuit 210 by turning off the bypass switch 204.

An AND circuit is provided between the PWM circuit 210 and the switching circuit 220.
211 is inserted. Then, the output 177 of the operation detection circuit 6 and the output 231 of the forced traveling switch 230 are input O
The output 236 of the R circuit 235 is input to the other input terminal of the AND circuit 211.

Therefore, when the electric power steering apparatus A is operating normally, the output 177 is 1, so the output 236 is also 1, and the pulse signal of the PWM circuit 210 is input to the switching circuit 220. Therefore, the vehicle speed can be controlled by operating the accelerator C.

When the operation detection circuit 6 detects an operation failure of the electric power steering apparatus A, the output 17 thereof is output as described above.
7 becomes 0, and the output 236 also becomes 0. That is, the PWM circuit 2
The pulse signal of 10 is cut off by the AND circuit 211, and the traveling electric motor 7 is stopped. When stopping traveling, it is best to avoid sudden braking to prevent collapse of cargo.

In this example, the electric power steering device A
Even when the steering wheel is inoperable, the steering wheel S and the steered wheels W are mechanically connected, and although the steering torque is large, the steered wheels W can be turned. In such a state, when the forced traveling switch 230 is turned on, the output 231 becomes 1, the bypass switch 204 is turned on, and the amplification circuit 200 and the PWM circuit 210 are connected via the attenuation circuit 203. At the same time, the other input, that is, the output 236 of the AND circuit 211 is set to 1. Therefore, the electric vehicle can safely travel at a slower speed than usual by operating the accelerator.

The traveling direction can be switched by selecting the forward contactor FC or the reverse contactor RC by the changeover switch DS interlocking with the traveling direction switching lever D and reversing the polarity of the field coil F.

As described above, since the traveling safety device B decelerates the traveling electric motor by the detection signal of the operation detection circuit that detects the malfunction of the electric power steering device, the collision occurs due to the unexpected malfunction of the electric power steering device. Accidents can be prevented and safety can be improved.

[Effect of device]

As described above, the electric power steering apparatus according to the present invention provides the idle current that gives the steering wheel an idle torque that is less than the mechanical loss torque of the steering wheel toward the other end position at the turning end position of the steering wheel. Can be drained,
It is possible to prevent overcurrent of the auxiliary electric motor at the turning end position, overheat due to overcurrent, and the like, which further contributes to power saving, improves the responsiveness of the steering wheel, and improves the operability and operation feeling.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a control circuit of an electric power steering device and an operation detection circuit of a traveling safety device of an electric vehicle. FIG. 3 is a block diagram showing a motor control circuit of a traveling safety device for an electric vehicle, and FIG. 4 is a diagram showing input / output characteristics of the widening circuit 30 of FIG. 3 ... Rotation direction detector, 4A ... Control main circuit, 5 ... Auxiliary motor, 6 ... Motion detection circuit, 7 ... Running electric motor, 8 ... Rotation end detector, 9 ... Idle circuit, B: Driving safety device for electric vehicle, W: Steering wheel.

Claims (1)

[Scope of utility model registration request] 1. A control main circuit for generating a drive current for driving an auxiliary electric motor for rotating a steering wheel and changing the direction of the steering wheel according to an output of a rotation direction detector for detecting a steering operation. At the turning end position of the steering wheel, an idle circuit is provided to generate an idle current that gives an idle torque to the other end position and is equal to or less than the mechanical loss torque of the steering wheel. Electric power steering device.