JP2007274771A - Direct-current motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct-current motor whose number of revolutions can be detected wherein it is unnecessary to separately provide a terminal or a power source for generating pulses in proportion to its number of revolutions and complication of the structure of the direct-current motor is not incurred. <P>SOLUTION: The direct-current motor 1 includes brushes 2a, 2b, a commutator 3, power supply lines 4a, 4b, and a number-of-revolutions detecting means 13 that counts current pulses to detect its number of revolutions. The motor is provided with: a detecting brush 6 that is brought into contact with the commutator 3 and is repeatedly brought into and out of continuity to the power supply lines 4a, 4b; and a pulse generation circuit 8 that superimposes as a pulse a charging current for a capacitor 7, connected between the detecting brush 6 and the power supply line 4a or 4b, on the current passed through the power supply line 4a or 4b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a DC motor having a brush and a commutator and capable of detecting the number of rotations.

  Normally, when detecting the rotation speed of a DC motor having a brush and a commutator, a speed detection sensor such as an encoder or a pulse generator is required, and a separate encoder, pulse generator, or speed detection sensor is provided, leading to an increase in cost. It was.

  Therefore, as a means for detecting an accurate rotational speed without using an encoder, a pulse generator, or a speed detection sensor, a pulse proportional to the rotational speed of the motor is generated, and this pulse is counted by a counter, whereby the rotational speed is calculated. A DC motor that can be detected is described in Patent Document 1.

  As shown in FIG. 11, this DC motor 51 is provided with a detection brush 54 that contacts the commutator 52 and repeats conduction and non-conduction with the negative electrode side of the power supply device 53 separately from the power supply brush 55. A voltage is applied via a terminal 56 by a power source 55 such as a battery between the negative electrode side of 52 and the detection brush 53.

  In the DC motor 51 having this configuration, the detection brush 54 and the negative electrode side of the power supply device 53 repeat conduction and non-conduction as the DC motor 51 rotates, which is proportional to the rotational speed of the DC motor 51. A number of pulses are generated and superimposed on the current of the DC motor 51, and this pulse is counted by the counter 57 to detect the rotation speed of the DC motor 51 and compared with the set rotation speed set by the rotation speed setting unit 58. The controller 59 controls the current of the DC motor 51 to control the rotational speed.

Here, the number of pulses generated is determined by the number of repetitions of conduction and non-conduction between the detection brush 54 and the negative electrode side of the power supply device 53. Since it is calculated | required by the product with rotation speed, the value which remove | divided the count number by the said product becomes rotation speed.
JP 2004-80921 A

  However, such a device has a problem that a terminal and a power source for generating a pulse proportional to the number of rotations are separately required, and the structure as a DC motor is complicated.

  Accordingly, the present invention requires a terminal and a power source for generating a pulse proportional to the rotational speed, and a DC motor capable of detecting the rotational speed without causing a complicated structure as a DC motor. The purpose is to provide.

In order to solve the above problem, the DC motor according to the present invention is:
A DC motor having a brush and a commutator, a power supply line, and a rotation speed detecting means for detecting a rotation speed by counting current pulses,
The detection brush is in contact with the commutator and repeats conduction and non-conduction with the power supply line, and charging current of a capacitor connected between the detection brush and the power supply line is used as the pulse. A pulse generation circuit for superimposing on a current flowing through the power supply line is provided.

  In order for the detection brush to repeat conduction and non-conduction with the commutator, the circumferential length of the contact surface of the detection brush with the commutator is set to the adjacent commutator piece constituting the commutator. It is necessary to form it shorter than the circumferential length of the insulating part formed between.

  Here, it is preferable that the pulse generation circuit includes a charging resistor in series with the capacitor.

  According to this, the charging time when the power supply line and the detection brush are conducted through the commutator and a charging current flows through the capacitor is determined by the capacitance of the capacitor and the resistance of the charging resistor. It can be controlled by a constant determined by the product of the value. At the same time, the peak value of the charging current can be controlled in inverse proportion to the resistance value.

  In addition, it is preferable that the pulse generation circuit includes a discharge resistor in parallel with the capacitor.

  According to this, the power supply line and the brush for detection become non-conductive, and the discharge current when the capacitor is discharged can be consumed by the discharge resistance, and the discharge time of the capacitor can be reduced. It can be controlled by a constant determined by the product of the capacitance and the resistance value of the discharge resistor.

  Furthermore, it is preferable that the detection brush is brought into contact with the axial end surface of the commutator. According to this, the axial length of the commutator can be shortened as compared with the case where the brush and the detection brush are arranged in the axial direction on the peripheral surface of the commutator.

  Further, it is preferable that the end face in the axial direction of the commutator is formed flat, that is, the undercut (indentation in the commutator axial direction of the insulating part) is not provided in the insulating part constituting the commutator. According to this, in the peripheral surface of the commutator, an undercut (insulation) is provided in an insulating portion between adjacent commutator pieces in order to prevent a short circuit between adjacent commutator pieces due to adhesion of abrasion powder of the brush. It is possible to eliminate the need to provide the undercut (indentation in the commutator axial direction of the insulating portion) on the axial end surface of the commutator piece, where it is necessary to provide a commutator radial recess in the portion). When the detection brush comes into contact with the commutator piece, the detection brush contacts the axial end surface of the commutator as the DC motor rotates due to the presence of the undercut. While moving in the circumferential direction, abnormal wear occurs due to repeated contact with the circumferential end of the commutator piece after falling into the undercut once. It is possible to prevent the Rukoto.

  Furthermore, in the prior art, in order to prevent such abnormal wear, it was necessary to use a metal brush as the detection brush. However, it is possible to eliminate the necessity and use a normal carbon brush, for example. .

  According to the present invention, it is possible to separately detect a rotational speed without requiring a terminal and a power source for generating a pulse proportional to the rotational speed, and without complicating the structure of the DC motor. A motor can be provided.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view showing an embodiment of a DC motor according to the present invention.

  The direct current motor 1 of the present embodiment includes power supply brushes 2a and 2b, a commutator 3, power supply lines 4a and 4b, power supply terminals 5a and 5b, and an axial end surface of the commutator 3 formed flat. The detection brush 6 made of a carbon brush that repeats conduction and non-conduction with the power supply lines 4a and 4b via the commutator 3 in contact with 3a, and between the detection brush 6 and the negative power supply line 4b A capacitor 7 having a capacitance C to be connected and a pulse generation circuit 8 that superimposes a charging current of the capacitor 7 on a current flowing through the power supply line 4b as a pulse. Further, the pulse generation circuit 8 includes a charging resistor 9 having a resistance value Rc positioned in series on the positive electrode side of the capacitor 7 and a discharging resistor 10 having a resistance value Rd positioned in parallel with the capacitor 7. The commutator 3 is provided at the end of the armature 11 in the axial direction.

  The power supply terminal 5 a is connected to the positive side of the battery 12. The negative electrode side of the battery 12 is grounded and connected to the power supply terminal 5b through the counter 13.

  The brushes 2a and 2b supply current from the battery 12 to a coil, which will be described later, of the armature 11 through the commutator 3, and come into contact with the peripheral surface 3b of the commutator 3 formed in a cylindrical shape. The commutator 3 is provided so as to extend in the radial direction.

  The commutator 3 supplies current from the battery 12 supplied from the brushes 2a and 2b to a coil (described later) of the armature 11, and although not shown here, the commutator pieces and the insulating portions are alternately arranged in the circumferential direction. They are formed side by side.

  The detection brush 6 intermittently supplies the current from the battery 12 to the capacitor 7 by contacting the axial end surface 3a of the commutator 3 and repeating conduction and non-conduction with the power supply line 4a as will be described later. It is provided so as to extend in the axial direction of the commutator 3.

  The capacitor 7 is charged by the current supplied from the detection brush 6 while the detection brush 6 is electrically connected to the power supply line 4 a via the commutator 3, and the detection brush 6 is connected to the commutator 3. As long as the power supply line 4a is not electrically connected to the power supply line 4a, it is discharged via the discharge resistor 10.

  The counter 13 is configured by combining, for example, a JK flip-flop or a T flip-flop, and when the current value of the current of the DC motor 1 exceeds the threshold value α, the current is counted as a pulse, and the count number is counted as the DC motor 1. This is provided for the stop and rotation speed control.

  While the detection brush 6 is electrically connected to the power supply line 4b via the commutator 3, the power supply line 4b has the charging current Ic of the capacitor 7 as an armature current IM flowing through the power supply line 4b as a pulse. The counter 13 counts the superimposed charging current Ic as a pulse.

  Hereinafter, the functions and operations of the brushes 2a and 2b, the commutator 3, and the detection brush 6 will be described in more detail, and the form of pulses generated by the pulse generation circuit 8 of the DC motor 1 according to the present invention and the counter 13 will be described. The counting method will be described in detail.

  FIG. 2 is a schematic perspective view showing a commutator, a brush and a detection brush of an embodiment of a DC motor according to the present invention, and FIG. 3 is a commutator, a brush and a detection of an embodiment of the DC motor according to the present invention. FIG. 4 is a schematic diagram showing a commutator of an embodiment of a DC motor according to the present invention viewed from the axial direction, and FIG. 5 is a DC diagram according to the present invention. It is a schematic diagram which shows the mutual connection aspect by planarly developing the commutator of a motor and the coil of an armature.

  As shown in FIG. 2, the commutator 3 is formed in a substantially cylindrical shape, and has a commutator piece 3 c having a circular arc shape obtained by dividing the cylinder in the circumferential direction, and a circumferential length e smaller than the commutator piece 3 c. Insulating portions 3d are formed alternately in the circumferential direction.

  3, the undercut 3e (insulating portion 3d) is formed on the peripheral surface of the commutator 3 by forming the radial thickness of the insulating portion 3d smaller than the radial thickness of the commutator piece 3c. Of the commutator 3 in the radial direction). Thereby, the abrasion powder generated when the brushes 2a and 2b come into contact with the commutator 3 adheres to the insulating portion 3d, thereby preventing the adjacent commutator pieces 3c from being short-circuited.

  As shown in FIG. 2, the axial end face 3a of the commutator 3 is formed flat, and no undercut (indentation in the commutator 3 axial direction of the insulating part 3d) is provided in the insulating part 3d.

  The brushes 2a and 2b are formed in a rectangular parallelepiped shape extending in the radial direction of the commutator 3, and a surface of the commutator 3 that contacts the peripheral surface 3b is formed in an arc tube shape along the peripheral surface 3b.

  The detection brush 6 is formed in a rectangular parallelepiped shape extending in the axial direction of the commutator 3, and the surface that contacts the axial end surface 3 a of the commutator 3 is formed in a flat shape.

  2 and 4, the circumferential length of the detection brush 6 is b, the circumferential length of the insulating portion 3d of the commutator 3 is e, and the circumferential length of the brushes 2a and 2b is a. In this case, the circumferential length b of the detection brush 6 is made smaller than the circumferential length e of the insulating portion 3d (b <e). Thereby, the brush 6 for a detection can be made into conduction | electrical_connection or non-conduction alternately and continuously with respect to the commutator piece 3c. Further, the circumferential length a of the brushes 2a and 2b is made larger than the circumferential length e of the insulating portion 3d (a> e). Thereby, the brushes 2a and 2b can be always conducted with respect to the commutator piece 3c.

  In addition, as shown in FIG. 5, the commutator 3 is formed by arranging 15 commutator pieces 3 c in the circumferential direction with an insulating portion not shown here arranged therebetween, and each commutator piece 3 c is a coil 14 in the armature 11. The commutator pieces 3c are always connected to each other, and the coil 14 has four poles, thirty conductors, and a series winding, and correspondingly, the stator side permanent magnets 15 are mutually polarized in the circumferential direction. There are 4 different poles. Of the commutator piece 3c, the brush 2a is brought into contact with the commutator piece 3c (I in FIG. 5), and the brush 2a, 2b is brought into contact with the commutator piece 3c (V in FIG. 5). Place on the circumference.

  With the configuration of the commutator 3 described above, current is supplied from the battery 12 shown in FIG. 1 to the coil 14 of the armature 11 via the power supply terminal 5a, the power supply line 4a, the brush 2a, and the commutator 3. Then, a magnetic flux is generated in the coil 14, and this magnetic flux repeats the magnetic flux of the permanent magnet 15 on the stator side and the attractive repulsion, and the armature 11 rotates.

  When the armature 11 rotates, the detection brush 6 rotates while contacting the axial end surface 3a of the commutator 3 in the circumferential direction, and the detection brush 6 is connected to the commutator piece 3c and the insulating portion 3d of the commutator 3. Are alternately contacted with each other to repeat conduction and non-conduction with the positive electrode side of the battery 12 via the commutator piece 3c of the commutator 3, so that the voltage of the battery 12 is periodically and intermittently applied to the capacitor 7. 7 charging current Ic flows into the power supply line 4b and is superimposed on the armature current IM flowing through the power supply line 4b.

  That is, the DC motor shown in FIG. 1 constitutes an equivalent circuit as shown in FIG. As the armature 11 rotates, the detection brush 6 moves in the circumferential direction while being in contact with the axial end surface 3a of the commutator 3, so that a virtual switch S is configured. Since this switch S is repeatedly turned on and off at a frequency determined by the product of the number of arrangements 15 and the number of rotations per unit time of the armature 11 in the circumferential direction of the commutator piece 3c, while the switch S is on, The voltage from the battery 12 is applied to the pulse generation circuit 8 by the battery 12, and the charging current Ic flows to the capacitor 7. The charging current Ic is supplied to the power supply line 4b, and the coil of the armature 11 flowing through the power supply line 4b. 14 is superimposed on the armature current IM. While the switch S is OFF, the voltage from the battery 12 is not applied to the pulse generation circuit 8, and a discharge current flows from the capacitor 7, and this discharge current is consumed by the discharge resistor 10.

  These currents are shown in the time chart as follows. FIG. 7 is a time chart showing the voltage applied to the pulse generation circuit 8 of the DC motor according to the present invention, the voltage of the capacitor 7 and the pulse generated by the pulse generation circuit 8.

  As described above, the detection brush 6 moves from the insulating portion 3d of the commutator 3 to the commutator piece 3c, and the timing at which the virtual switch S is turned on is t1, t3, and from the commutator piece 3c to the insulating portion 3d. If the timing at which the detection brush 6 moves and the virtual switch S is turned off is t2 and t4, the voltage V applied to the circuit constituted by the capacitor 7 and the charging resistor 9 is shown in the upper part of FIG. It becomes a square wave as shown.

  When the voltage V from the battery 12 is applied to the pulse generation circuit 8 at t1, the capacitor 7 is charged, and the voltage VC of the capacitor 7 is determined by the product CRc of the capacitance C of the capacitor 7 and the charging resistor Rc. Depending on the time constant, the integrated wave as shown in the middle part of FIG. The larger the time constant CRc, the slower the voltage VC rises, and the longer the charging time.

  When the voltage V from the battery 12 is no longer applied to the pulse generation circuit 8 at t2, the capacitor 7 is discharged, and the capacitor voltage VC is determined by the product CRd of the capacitance C of the capacitor 7 and the discharge resistor Rd. Thus, the differential wave as shown in the middle part of FIG. As the time constant CRd increases, the rate at which the voltage VC falls decreases and the discharge time increases. Thereafter, similarly at t3, the voltage VC of the capacitor 7 rises with an integrated wave, and similarly at t4, the voltage VC of the capacitor 7 also falls with a differential wave.

  Thus, the voltage VC of the capacitor 7 draws a sawtooth waveform that alternately repeats the integrated wave and the differential wave. During the discharge period from t2 to t3 and after t4, the discharge current of the capacitor 7 is consumed by the discharge resistor 10, so this discharge current is not supplied to the power supply line 4b, and the armature current IM of the armature 11 is Not superimposed.

  Therefore, the pulse superimposed on the armature current IM flowing through the power supply line 4b becomes a charging current Ic of the capacitor 7 having an intermittent peak shape as shown in the lower part of FIG.

  That is, the current waveform of the DC motor 1 input to the counter 13 is as shown in FIG. 8 because the charging current Ic of the capacitor 7 is superimposed on the armature current IM. FIG. 8 is a schematic diagram showing a current waveform according to an embodiment of the DC motor according to the present invention.

  The armature current IM is proportional to the number of arrangement of the commutator pieces 3c in the circumferential direction and the number of rotations of the armature 11 because the current from the battery 12 is supplied by the brushes 2a and 2b and the commutator 3. Since the discharge current Ic is superimposed on this ripple component, the current waveform of the DC motor 1 becomes a waveform as shown in FIG.

  When the current value of the current waveform exceeds the threshold value α, the counter 13 counts the current as a pulse, and divides this count by the number of arrangement of the commutator pieces 3c in the circumferential direction to rotate the DC motor 1. Ask for.

  As described above, according to the present embodiment, by adding the simple pulse generation circuit 8 using the capacitor 7, the comb-shaped discharge current having a frequency proportional to the number of the commutator pieces 3 c arranged in the circumferential direction. By superimposing Ic as a pulse on the armature current IM of the armature 11 and counting the pulse by the counter 13, the rotational speed of the DC motor 1 can be detected.

  In addition, since it is possible to eliminate the need to separately provide terminals for detecting the rotational speed other than the power supply terminals 5a and 5b in the DC motor 1 as in the prior art, the structure of the DC motor 1 is complicated. It becomes possible to detect the rotation speed without inviting.

  Furthermore, unlike the prior art, it is not necessary to provide a separate power source for superimposing a pulse for detecting the rotational speed on the armature current IM, so that this also does not complicate the structure of the DC motor 1. It becomes possible to detect the rotation speed. In addition, since no separate power source is used, maintenance work such as power supply replacement can be eliminated, and durability against vibration and impact can be enhanced.

  Furthermore, in the DC motor 1 according to the present embodiment, the pulse generation circuit 8 to be added is a simple circuit using the capacitor 7, so that not only the number of terminals and the power supply as described above are reduced, but also additional components are reduced. It is possible to reduce the size and weight, improve the robustness, and improve the durability. As a result, the direct current motor 1 itself can be reduced in size and weight, become more robust, and improve the durability.

  In the embodiment described above, the detection brush 6 is provided on the positive power supply brush 2a side, the positive side of the pulse generation circuit 8 is connected to the detection brush 6, and the negative side of the pulse generation circuit 8 is connected to the negative electrode. As shown in FIG. 9, the detection brush 6 is provided on the negative brush 2b side, and the negative electrode side of the pulse generation circuit 8 is connected to the detection brush 6 to generate a pulse. A configuration in which the positive electrode side of the circuit 8 is connected to the power supply line 4a on the positive electrode side may be employed. An equivalent circuit in this case is as shown in FIG.

  Also by this, a pulse having a frequency proportional to the number of arrangement of the commutator pieces 3 c in the circumferential direction is superimposed on the armature current IM of the armature 11 only by adding a simple pulse generation circuit 8 using the capacitor 7. Thus, the number of rotations of the DC motor can be detected by counting the pulses.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications and substitutions are made to the above-described embodiment without departing from the scope of the present invention. be able to. For example, the counter 13 can be provided on the positive electrode side of the battery 12 in FIG.

  The present invention relates to rotation speed detection of a DC motor applied to a memory seat system, a power window device, a sunroof device, etc. of an automobile, and a terminal for pulse generation without using a speed detection device such as an encoder. Since the rotational speed can be detected without providing a separate power source and used for stopping and rotating the DC motor, the present invention is applicable to various automobiles and is useful.

It is a schematic diagram which shows one Example of the DC motor by this invention. 1 is a schematic perspective view showing a commutator, a brush, and a detection brush of an embodiment of a DC motor according to the present invention. 1 is a schematic diagram showing a commutator, a brush and a detection brush of an embodiment of a DC motor according to the present invention as viewed from the axial direction. It is a schematic diagram which shows the commutator of one Example of the DC motor by this invention seeing from an axial direction. It is a schematic diagram which shows the connection aspect mutually by developing the commutator and armature coil of the DC motor according to the present invention in a horizontal plane. It is an equivalent circuit of one Example of the DC motor by this invention. It is a time chart which shows the voltage applied to the pulse generation circuit of the DC motor concerning the present invention, the voltage of a capacitor, and the pulse which a pulse generation circuit generates. It is a schematic diagram which shows the current waveform by one Example of the DC motor by this invention. It is a schematic diagram which shows the other Example of the DC motor by this invention. It is an equivalent circuit of another embodiment of the DC motor according to the present invention. It is a schematic diagram which shows the rotation speed detection apparatus using the conventional DC motor.

Explanation of symbols

1 DC motor 2a Brush (positive side)
2b Brush (negative electrode side)
3 commutator 3a axial end face 3b peripheral surface 3c commutator piece 3d insulating part 4a power supply line (positive electrode side)
4b Power supply line (negative electrode side)
5a Power supply terminal (positive side)
5b Power supply terminal (negative electrode side)
6 Detection Brush 7 Capacitor 8 Pulse Generation Circuit 9 Charging Resistor 10 Discharge Resistor 11 Armature 12 Battery 13 Counter 14 Coil 15 Permanent Magnet

Claims (5)

A DC motor having a brush and a commutator, a power supply line, and a rotation speed detecting means for detecting a rotation speed by counting current pulses,
The detection brush is in contact with the commutator and repeats conduction and non-conduction with the power supply line, and charging current of a capacitor connected between the detection brush and the power supply line is used as the pulse. A direct current motor comprising a pulse generation circuit for superimposing on a current flowing through a power supply line.   The DC motor according to claim 1, wherein the pulse generation circuit includes a charging resistor in series with the capacitor.   The DC motor according to claim 1, wherein the pulse generation circuit includes a discharge resistor in parallel with the capacitor.   The DC motor according to claim 1, wherein the detection brush is brought into contact with an axial end surface of the commutator.   The DC motor according to claim 4, wherein an axial end surface of the commutator is formed flat.

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