JPH07288999A - Step motor controller - Google Patents

Abstract

(57) [Abstract] [Purpose] To detect the excitation coil short circuit and prevent the generation of holding torque. [Structure] Four-phase excitation coils A to D of the step motor 1
Are variable resistors 40A to 40D and a drive 60, respectively.
It is connected to A-60D. A common drive voltage V is applied to each variable resistor and each drive. The surge absorbing circuits 50A to 50D composed of a diode and a resistor are connected in parallel with the exciting coil through the variable resistance sliding terminals. Short-circuit detection circuits 70A to 70D are connected to both ends of each variable resistor. The output terminal of each short-circuit detection circuit is connected to the corresponding terminal of the input port 42 of the CPU 30, and the input terminal of each drive is connected to the corresponding terminal of the output port 41. When the exciting coil is short-circuited, the CPU 30 simultaneously energizes the short-circuited exciting coil and the exciting coil opposite thereto to make the total magnetomotive force in the motor zero. This can prevent the holding torque from being generated due to a short circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor control device, and more particularly to a step motor control device for preventing generation of holding torque in the step motor due to short circuit of an exciting coil.

[0002]

2. Description of the Related Art A conventional step motor controller is shown in FIG. This is a control device when a step motor is used as a drive source for an EGR valve. A, B, C, D are four-phase exciting coils of the step motor, and drive 60A, 60B, 60 respectively.
A, B, C of output port 401 via C, 60D
And D-phase output terminals. Each drive has the same structure, for example, the drive 60A is composed of a voltage dividing circuit composed of resistors A2 and A3 and a power conversion transistor A1.
The pulse output from the CPU 301 is voltage-adjusted by the voltage divider circuit and applied to the transistor to convert the power to excite the exciting coil. The exciting coil of each phase has surge current absorbing circuits 50A, 50B, 50 composed of resistors and diodes.
C and 50D are provided.

The CPU 301 inputs the engine speed and the intake air amount, determines the command opening of the EGR valve according to these input values, and determines the pulse number corresponding to the command opening for each phase of the output port 401. Output in order from the output terminal. The output pulse is converted into electric power by the drive connected to the terminal to excite each corresponding exciting coil, and the step motor 1 rotates step by step accordingly.
The EGR valve is opened to a predetermined opening. The surge current absorption circuit consumes energy accumulated in the excitation coil when the excitation phase is switched, and improves the response characteristic of the step motor.

[0004]

However, like the ordinary analog motor, the step motor may be short-circuited due to damage of the insulating layer applied to the exciting coil due to coil heat generation due to copper loss or the like, or the operating environment. Further, when the machine is damaged, coil breakage or contact failure of the connector may occur. In any of these cases, even if the excitation coil is energized as usual, it may not move according to the command pulse from the CPU. In the latter case, if disconnection is detected and all drives are turned off, the step motor In the free state, the EGR valve can be closed by attaching a closing spring.

On the other hand, when the exciting coil is short-circuited, a large exciting current is generated, and the transistor in the drive may be damaged by the overcurrent. In this case, the motor does not work according to the command. Of course, even if the drive is turned off, the transistor will already be damaged and the exciting coil will always be energized. Therefore, the holding torque will be generated in the step motor and the EGR valve Is braked and cannot be opened to a predetermined opening degree, nor can it be returned to the closed state. There was a problem that the engine stalled and could not be driven again. Therefore, in view of the above-mentioned conventional problems, the present invention provides a step motor control device that does not fall into a holding state even if a power element such as a transistor in a drive is damaged due to a short circuit in an exciting coil. The purpose is to do.

[0006]

Therefore, the present invention comprises pulse means for generating a pulse signal, exciting means for exciting a predetermined exciting coil according to the pulse signal, and detecting means for detecting a short circuit of the exciting coil. When a short circuit of the exciting coil is detected by the detecting means, another exciting coil is excited so as to cancel the exciting force of the exciting coil with respect to the rotor, thereby controlling the magnetomotive force of the entire step motor to zero. It has a control means for controlling. Further, according to the present invention, the other exciting coil is short-circuited, and the exciting coil is opposed to the rotor.

[0007]

Since the short circuit of the exciting coil is detected and the other exciting coils are excited so as to cancel the magnetomotive force of the exciting coil with respect to the rotor, the magnetomotive force of the step motor as a whole is controlled to zero. It is possible to prevent the generation of holding torque in the step motor due to the short circuit of the exciting coil.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the construction of an EGR valve which is an embodiment of the present invention. The EGR valve includes a drive unit G, a cooling unit H, and a valve unit I. The drive unit G is a drive force generation unit for opening the EGR valve, and when a drive pulse is input to the step motor 1, the rotor 2 rotates. This rotational movement is converted into a linear movement by the sliding screw 3 at the center of the rotor 2 and transmitted to the valve portion I by the coupling 5 connected to the end of the sliding screw 3.

The valve portion I has a poppet 6 and a poppet 6
Seating seat 7 is provided, and the poppet 6 is the valve shaft 4
It is connected to the coupling 5 via the valve and opens / closes the valve according to the movement of the sliding screw 3. When the valve opens,
The exhaust gas is introduced from an inlet 9 and the flow rate is adjusted by opening and closing the poppet 6, and the exhaust gas is taken into the intake side of the engine from the outlet 10. The coupling 5 is provided with a biasing spring 11 which is always compressed, and when the step motor 1 has no torque, the poppet 6 can be seated on the seat 7 and closed. The cooling unit H has a water cooling device 8 provided between the step motor 1 and the valve unit I for the purpose of blocking the high temperature of the exhaust gas from the inlet 9 from being transmitted to the step motor 1. The engine cooling water is provided so as to flow back around the valve shaft 4 and the sliding screw 3.

FIG. 2 shows the structural principle of the step motor 1. The rotor 2 has a permanent magnet structure, and both magnetic poles are opposed to the air gap. The stator 15 surrounding the rotor 2 is provided with four salient poles at equal pitches so as to be opposed to the magnetic poles of the rotor 2. The exciting coil provided in each salient pole is a four-phase exciting coil A, B, C having an electrical angle of 90 °.
I'm doing D. By sequentially energizing the exciting coils of each phase, the magnetic poles of the rotor 2 are attracted to the energized salient poles to rotate.

FIG. 3 shows a control device for the step motor 1. A, B, C, and D are four-phase exciting coils of the step motor 1, which are variable resistors 40A, 40B, and 40, respectively.
C, 40D and drives 60A, 60B, 60C, 60
Connected with D. A common drive voltage V is applied to each variable resistor and each drive. The surge current absorption circuits 50A, 50B, 50C, and 50D each including a diode and a resistor are connected in parallel with the exciting coil through the sliding terminal of the variable resistor. A short circuit detection circuit 70 is provided at both ends of each variable resistor.
A, 70B, 70C and 70D are connected. The output terminal of each short-circuit detection circuit is connected to the corresponding input terminal of the input port 42 of the CPU 30, and the input terminal of each drive is connected to the corresponding output terminal of the output port 41.
The surge current absorption circuit consumes energy accumulated in the exciting coil when the exciting phase is switched and improves the response characteristic.

The drive connected to each exciting coil, the short-circuit detecting circuit and the surge current absorbing circuit have the same structure, and the exciting coil A will be described here. Drive 60A
Is composed of a voltage dividing circuit composed of resistors A2 and A3 and a transistor A1 of a power element. The short-circuit detection circuit 70A is connected to the output terminals of the amplifier A5 and the amplifier A5 for amplifying the voltage drop on the variable resistor 40A due to the exciting current, and is connected to the output terminals of the comparator A6 and the comparator A6 for judging the occurrence of the short-circuit current. The reference voltage generator A7 is connected to the terminal and supplies a reference voltage for comparison.

When a pulse is input to the drive 60A, the voltage dividing circuit divides the pulse voltage and applies it to the base of the transistor A1. The transistor A1 is turned on / off according to the presence / absence of its base voltage, and excites the exciting coil A connected to the collector. The variable resistor 40A is a detection resistor for detecting an exciting current. The amplifier A5 is a variable resistor 40 based on the exciting current.
Amplify the voltage drop on A. The comparator A6 determines the occurrence of a short circuit current based on the output of the amplifier A6 and the output voltage of the reference voltage generator A7 and outputs a short circuit signal.

In controlling the EGR valve, the CPU 30
Inputs the engine speed and the intake air amount, determines the command opening of the EGR valve according to these input values, calculates the pulse number corresponding to the command opening, and calculates the A phase, B phase of the output port 41.
Output in order from the phase, C phase, and D phase output terminals. Each drive receives the pulse and excites the exciting coil connected to it, and the step motor 1 rotates. When an exciting coil short circuit occurs, the CPU 30 outputs a pulse to the exciting coil at an electrical angle of 180 ° at the same time as stopping the pulse output to the other exciting coils in response to the input short circuit signal.
As a result, the magnetomotive force in the step motor 1 becomes zero.
Therefore, the occurrence of holding due to a short circuit in the step motor is prevented, and the EGR valve can be closed by the restoring force of the biasing spring 11. As a result, the engine is prevented from stall due to the short circuit of the exciting coil.

Regarding the magnetomotive force of the exciting coil, the number of windings N of the exciting coil to be short-circuited is small, but as the number of windings N is smaller, the coil resistance is also reduced and the current is increased. The magnetomotive force does not change.

FIG. 4 shows an operation time chart of the CPU 30. A, U, D, and E are drive pulses of the step motor 1 output from the CPU 30, and A represents the current value of the A-phase exciting coil flowing through the A-phase variable resistor 40A. Since the coil has not been disconnected or short-circuited during the T1 period, a predetermined current value determined by the coil resistance flows in the A phase, and the step motor 1 normally rotates to drive the EGR valve in the opening direction. ing.

Next, at time t3, when the A-phase coil is short-circuited, the exciting coil resistance decreases and an overcurrent flows.
At t4, when it exceeds a predetermined reference value oc, the output of the comparator A6 is inverted and the short circuit signal is input to the A terminal of the input port 42. The CPU 30 determines from the short-circuit signal that the A-phase exciting coil is short-circuited, and also applies a drive pulse to the C-phase coil. No drive pulse is applied to the B and D phases. Therefore, current flows through both the A-phase exciting coil and the C-phase exciting coil through which the short-circuit current flows. Since the A-phase current and the C-phase current flow in opposite directions to each other, the total of the magnetomotive forces generated in both exciting coils eventually becomes zero, and no driving torque or holding torque is generated, so the step motor 1 closes the valve. The valve can be closed in the direction by the force of the biasing spring 11.

The present embodiment is configured as described above, detects a short circuit of the exciting coil of the step motor 1, and excites the shorted exciting coil and the exciting coil at an electrical angle of 180 °.
By deenergizing the other exciting coils, the magnetomotive force of the entire step motor is reduced to zero, the holding torque is eliminated, and the EGR valve can be closed by the force of the biasing spring, so that engine stall can be avoided. In this example,
The example in which the one-phase exciting coil is short-circuited has been shown, but even when the two-phase exciting coil is short-circuited, the other two exciting coils are simultaneously excited to reduce the total magnetomotive force of the step motor 1 to zero. Therefore, the valve can be closed by the restoring force of the biasing spring 11. In addition, the exciting coil for counteracting the magnetomotive force of the short-circuit exciting coil has an electrical angle of 180 °.
However, if the total magnetomotive force becomes zero, the same effect as that of the present embodiment can be obtained even if other exciting coils or all exciting coils are excited.

[0019]

As described above, according to the present invention, the short circuit of the exciting coil is detected by detecting the short circuit of the exciting coil and exciting the other exciting coil so as to cancel the magnetomotive force of the exciting coil with respect to the rotor. The magnetomotive force of the entire step motor is set to zero to prevent the generation of holding torque.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an EGR valve of this embodiment.

FIG. 2 is a diagram showing a structure of a step motor in an EGR valve.

FIG. 3 is a drive circuit of a step motor of the present embodiment.

FIG. 4 is a time chart showing a control operation.

FIG. 5 is a conventional step motor type EGR valve drive circuit.

[Explanation of symbols]

1, step motor 2, rotor 3, sliding screw 4, valve shaft 5, spring coupling 6, poppet 7, seating seat 8, water cooling device 9, inlet 10, outlet 11, bias spring 15, stator 30, 301, CPU 41, 401, output port 42, input port 40A, 40B, 40C, 40D, variable resistance 50A, 50B, 50C, 50D, surge current absorption circuit 60A, 60B, 60C, 60D, drive 70A, 70B, 70C, 70D, Short circuit detection circuit A, B, C, D, excitation coil A1, transistors A2, A3, resistor A5, amplifier A6, comparator A7, reference voltage generator

Claims (2)

[Claims] 1. A step motor control device having a plurality of exciting coils and a rotor rotated by the magnetomotive force of the exciting coils, the pulse device generating pulse signals.
Excitation means for exciting a predetermined excitation coil according to the pulse signal, and detection means for detecting a short circuit of the excitation coil are provided. When the detection means detects a short circuit of the excitation coil, the rotor of the excitation coil is provided. A step motor control device comprising a control means for controlling the magnetomotive force of the entire step motor to zero by exciting another exciting coil so as to cancel the magnetomotive force of the step motor. 2. The step motor control device according to claim 1, wherein the other exciting coil is an exciting coil facing the short-circuited exciting coil with respect to the rotor.