JP3816607B2 - Stepping motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stepping motor driven by multiphase excitation by a drive circuit.
[0002]
[Prior art]
Conventionally, the excitation coil of each phase in this type of stepping motor has the same form such as its own electrical resistance and number of turns. Therefore, for example, in the case of a rotary type stepping motor, the rotational torque in one direction and the rotational torque in the other direction are the same under the same driving conditions.
[0003]
[Problems to be solved by the invention]
By the way, as a usage pattern of such a stepping motor, a different rotational torque according to the rotational direction may be required. For example, when used as a drive source for an open / close valve, the rotation of the stepping motor is required when the valve closing torque is to be made smaller than the valve opening torque in order to minimize the wear of the valve and the seat when the open / close valve is closed. The torque is required to be different depending on the direction of rotation.
However, in the case of the above conventional stepping motor, under the same driving conditions, the rotational torque cannot be varied according to the rotational direction, and if the drive conditions are to be changed according to the rotational direction, As a result, the driving circuit of the stepping motor is complicated, resulting in an increase in manufacturing cost.
[0004]
The present invention has been made based on a demand for such a conventional stepping motor, and provides a stepping motor capable of differentiating output torques when driving a motor in one direction and the other direction under the same driving conditions. It is intended.
[0005]
[Means for Solving the Problems]
The invention described in claim 1 is a PM type stepping motor that includes a four-phase exciting coil that is bifilar-wound so as to be unipolarly driven, and is driven to rotate in both forward and reverse directions by a two-phase excitation method. Of the four-phase excitation coils, the torque generated by at least one-phase excitation coil is set to a magnitude different from the torque generated by the other-phase excitation coils in order to differentiate the output torque when driving the motor in one direction and the other direction. It is characterized by that.
Further, the invention described in claim 2 is a PM type stepping motor that is rotationally driven in both forward and reverse directions and includes a two-phase exciting coil that is monofilar wound so as to be bipolar driven. The torque generated by one-phase excitation coil is set to a magnitude different from the torque generated by the other-phase excitation coil so that the output torque when driving the motor in one direction and the other direction is different. It is a feature.
[0006]
Further, the invention described in claim 3 is characterized in that, in claim 1 or 2, the exciting coils having different generated torques have different products of the reciprocal number of electrical resistance and the number of turns .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIGS. 1 to 8 are diagrams for explaining a first embodiment of the present invention, which is provided with two pairs of exciting coils that are bifilar-wound so as to be unipolarly driven, and is driven by a two-phase excitation method. This is an application example as a PM type stepping motor .
First, the basic configuration of the stepping motor according to the present embodiment will be described with reference to FIGS. 1, 2, and 3. In FIG. 1, reference numerals 1 and 2 are excitation coils that are bifilar wound so as to generate a magnetic field having a phase relationship of 180 ° with each other, and the magnetic field generated by the excitation coil 1 is the A phase. The magnetic field generated by the exciting coil 2 having the opposite phase to the A phase is indicated by adding “-” to the letter “A” of the A phase in the drawing, and hereinafter referred to as “A bar phase”. Reference numerals 3 and 4 are excitation coils wound by bifilar so as to generate a magnetic field having a phase relationship of 180 ° with each other. The magnetic field generated by the excitation coil 3 is a B phase. The magnetic field generated by the excitation coil 4 having the opposite phase to the B phase is indicated by adding “-” to the letter “B” of the B phase in the figure, and hereinafter referred to as “B bar phase”. Further, the magnetic fields (A phase and B phase) generated by the exciting coils 1 and 3 are set to have a phase difference of 90 °.
[0008]
In the present embodiment, as shown in FIG. 2, the exciting coils 1 and 2 are simultaneously wound around the same bobbin 5 to have an integral structure, and the stator pole 6 forming the magnetic pole has a trapezoidal shape. Similarly, the exciting coils 3 and 4 are simultaneously wound around the same bobbin 7 to have an integral structure, and the stator pole 8 forming a magnetic pole has a trapezoidal shape. Reference numeral 9 in the figure denotes a rotor composed of an alnico-based permanent magnet or the like, and magnetic poles corresponding to the stator poles 6 and 8 are formed as shown in FIG. The stepping motor having such a basic configuration is driven by a two-phase excitation method in which two phases are excited with respect to one input pulse as shown in FIG.
[0009]
In the first embodiment of the present invention, in such a basic configuration, the excitation current in the former is changed between the excitation coils 1 and 2 and the excitation coils 3 and 4 by making their electrical resistances and turns different. The product AT (ampere turn) of the excitation current and the number of turns in the latter is set smaller than the product AT (ampere turn) of the number of turns. Thereby, the torque generated by the exciting coils 3 and 4 is set smaller than the torque generated by the exciting coils 1 and 2.
For example, the exciting coils 1 and 2 have a wire diameter of 0.155 mm, a winding number of 390 turns, and an electrical resistance of 30 ohms, while the exciting coils 3 and 4 have a wire diameter of 0.13 mm, a winding number of 550 turns, and an electric resistance of 60 ohms. did. When the exciting coils 1, 2, 3, and 4 are driven under the same driving conditions using a common power source, the electrical resistance and the exciting current are inversely proportional, so the product of the reciprocal of the electrical resistance and the number of turns is AT. (Ampere turn) will be supported. Therefore, the product of the reciprocal of the electrical resistance and the number of turns in the exciting coils 1 and 2 is set larger than the product of the reciprocal of the electrical resistance and the number of turns in the exciting coils 3 and 4.
[0010]
In this way, the torque generated by the exciting coils 3 and 4 is set smaller than the torque generated by the exciting coils 1 and 2, so that the θ-T characteristics (angular displacement-torque characteristics) for each phase are shown in FIGS. As shown in FIG.
In these drawings, the torque generated by the exciting coil 1 is “A phase torque T (A)”, and the torque generated by the exciting coil 2 is above the letter “A” of the A phase torque T (A) in the figure. The symbol “−” is attached to the symbol, and hereinafter, it is referred to as “A-bar phase torque”. Similarly, the torque generated by the excitation coil 3 is “B-phase torque T (B)”, and the torque generated by the excitation coil 4 is “ The symbol “−” is used for the description, and hereinafter referred to as “B-bar phase torque”.
[0011]
4 shows the θ-T characteristic when the exciting coils 1 and 3 are excited (hereinafter referred to as “sequence 1”), and FIG. 5 shows the case when the exciting coils 1 and 4 are excited (hereinafter referred to as “sequence 2”). 6 shows the θ-T characteristic when the excitation coils 2 and 4 are excited (hereinafter referred to as “sequence 3”), and FIG. 7 shows the case when the excitation coils 2 and 3 are excited (hereinafter referred to as “sequence 3”). Θ-T characteristics of “Sequence 4”. In both cases, the B-phase and B-bar phase torques are smaller than the A-phase and A-bar phase torques. In these drawings, T (D) is a dedent torque, and T1, T2, T3, and T4 are combined torques in sequences 1, 2, 3, and 4.
[0012]
Next, the operation of the stepping motor of this example will be described using such sequences 1, 2, 3, and 4 (see FIG. 8).
(Right rotation (CW direction) operation)
Now, it is assumed that the rotor 9 is stopped at the stable point P1 of the sequence 1. By switching to the sequence 2 at this time, the operating point becomes the P2 point on the composite torque T2, the force in the CW direction is applied, the rotor 9 rotates right, and moves to the stable point P3 of the sequence 2. After that, by switching to the sequence 3, the operating point becomes the P4 point on the combined torque T3, the force in the CW direction acts, the rotor 9 rotates right, and moves to the stable point P5 of the sequence 3. After that, by switching to the sequence 4, the operating point becomes the P6 point on the combined torque T4, the force in the CW direction acts, the rotor 9 rotates to the right, and moves to the stable point P7 of the sequence 4. By repeating the above operation, the rotor 9 rotates to the right.
[0013]
(Left rotation (CCW direction) operation)
Now, it is assumed that the rotor 9 is stopped at the stable point P7 of the sequence 4. By switching to sequence 3 at this time, the operating point becomes P8 point on the combined torque T3, the force in the CCW direction acts, and the rotor 9 rotates counterclockwise and moves to the stable point P5 of sequence 3. Thereafter, by switching to the sequence 2, the operating point becomes the P9 point on the combined torque T2, the CCW direction force acts, the rotor 9 rotates counterclockwise, and moves to the stable point P3 of the sequence 2. Thereafter, by switching to sequence 1, the operating point becomes P10 point on the combined torque T1, the force in the CCW direction acts, the rotor 9 rotates counterclockwise, and moves to the stable point P1 of sequence 1. By repeating the above operation, the rotor 9 rotates counterclockwise.
[0014]
By the way, in such a stepping motor, the torque at the right rotation is smaller than the torque at the left rotation. This is because the excitation coils 3, 4, 4, and the product of the excitation current and the number of turns AT (ampere turns) in the excitation coils 1, 2, are set according to the setting example of the electrical resistance and the number of turns of the excitation coils 1, 2, 3, 4. This can be confirmed from an operation test of a stepping motor in which the product AT (ampere turn) of the excitation current and the number of turns in is small. As a result of the operation test, the left rotation torque was 2.0 kg · km and the right rotation torque was 1.5 kg · km. It can be presumed that the difference between the right rotational torque and the left rotational torque is due to the difference between the torque minimum points PA and PB on the envelope shown by the thick line in FIG. That is, since the minimum torque point PA in the right rotation region is smaller than the minimum torque point PB in the left rotation region, it can be estimated that the right rotation torque is smaller than the left rotation torque.
[0015]
Stepping motors having such torque output characteristics can be widely used as drive sources for various operating mechanisms that require different rotational torques depending on the rotational direction. For example, when used as a drive source for an opening / closing valve, the valve closing torque can be made smaller than the valve opening torque in order to suppress wear and tear between the valve and the seat when the opening / closing valve is closed.
[0016]
(Second Embodiment)
FIG. 9 is a diagram for explaining a second embodiment of the present invention. In the case of this example, the excitation coil 11 has a basic configuration in which two excitation coils 11 and 12 wound in a monofilar are bipolar driven. The product of the exciting current and the number of turns AT (ampere turn) in the exciting coil 11 is set smaller than that of the exciting current and the number of turns AT (ampere turn) in the exciting coil 11. Therefore, each of the exciting coil 11 and the exciting coil 12 corresponds to the exciting coils 1 and 2 and the exciting coils 3 and 4 in the above-described embodiment, and torque output characteristics similar to those in the above-described embodiment can be obtained.
The present invention can be applied to a multi-phase excitation stepping motor including a 1-2 phase excitation method, and can also be applied to a linear stepping motor.
[0017]
【The invention's effect】
As described above, according to the first to third aspects of the present invention, the torque generated by at least one of the four- phase excitation coils is different from the torque generated by the other-phase excitation coils. By setting to, the output torque when driving the motor in one direction and the other direction can be made different under the same driving condition, and as a result, it can operate without complicating the drive circuit and increasing the price. It can be effectively used as a drive source for various operating mechanisms that require different torques in directions.
[0018]
Here, in the invention according to the third aspect , the exciting coils having different generated torques have different products of the reciprocal of the electrical resistance and the number of turns. as possible out to set the different sizes output torque when the direction of the motor drive.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a basic configuration of a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of a relationship between a rotor and a stator in the basic configuration of FIG.
3 is an explanatory diagram of a two-phase excitation method in the basic configuration of FIG. 1;
FIG. 4 is an explanatory diagram of a sequence 1 in the first embodiment of the present invention.
FIG. 5 is an explanatory diagram of a sequence 2 in the first embodiment of the present invention.
FIG. 6 is an explanatory diagram of a sequence 3 in the first embodiment of the present invention.
FIG. 7 is an explanatory diagram of a sequence 4 in the first embodiment of the present invention.
FIG. 8 is an operation explanatory diagram of the first embodiment of the present invention.
FIG. 9 is an explanatory diagram of a basic configuration of a second embodiment of the present invention.
[Explanation of symbols]
1, 2, 3, 4 Excitation coil 5, 7 Bobbin 6, 8 Stator pole 9 Rotor

Claims (3)

A PM type stepping motor comprising a four-phase exciting coil wound by bifilar so as to be unipolar driven and driven to rotate in both forward and reverse directions by a two-phase excitation method,
Of the four-phase excitation coils, the torque generated by at least one-phase excitation coil has a magnitude different from the torque generated by the other-phase excitation coils so that the output torque when driving the motor in one direction differs from that in the other direction. Stepping motor characterized by setting. A PM type stepping motor that is driven to rotate in both forward and reverse directions with a two-phase exciting coil that is monofilar wound so as to be bipolar driven,
Of the two-phase excitation coils, the torque generated by the one-phase excitation coil is set to a magnitude different from the torque generated by the other-phase excitation coils so that the output torque when driving the motor in one direction and the other direction is different. Stepping motor characterized by that.   3. The stepping motor according to claim 1, wherein the exciting coils having different generated torques have different products of the reciprocal of the electrical resistance and the number of turns.

Images