JP2010154687A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce radiation noises arising from a common mode current by causing the common mode current to flow to a metal frame smoothly. <P>SOLUTION: A motor drive device includes winding terminals 7a-7d connected to the ends of windings of a stepping motor and exposed outside the metal frame, cables arranged between a driver and the winding terminals 7a-7d to transmit drive currents indicating the drive signals outputted from the driver to the windings, and capacitors 17a-17d arranged between the metal frame of the stepping motor and the winding terminals 7a-7d to feed back the common mode currents made to flow in the cables, to the driver via the metal frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor driving device that drives a stepping motor.

  2. Description of the Related Art Conventionally, for example, a motor drive provided with a phase switching circuit that switches phases of two windings of a stator in a two-phase stepping motor and a switching element that adjusts a pulse width so that a current flowing through the winding is constant The device is known.

  In recent years, in order to achieve high-precision control of stepping motors, high-speed rotation, and miniaturization of motors, it is essential to increase the switching frequency in the phase switching circuit. Increasing the switching frequency brings about deterioration of radiation noise. Furthermore, in order to suppress the heat generation of the switching element due to the high frequency of switching, the speed of PWM switching of the switching element is also increased. The speeding up of PWM switching of the switching element is one of the causes of deterioration of radiation noise.

  Therefore, in the rotation stop holding mode of the stepping motor, a technique has been proposed in which the PWM switching operation of the switching element is stopped and a constant current is supplied from another power source to the internal winding of the stepping motor (see Patent Document 1). However, in the rotational operation mode of the stepping motor, the PWM switching operation of the switching element cannot be stopped, so that it is a problem that radiation noise cannot be suppressed. In order to solve this problem, a technique for reducing radiation noise by appropriately suppressing the switching speed with a simple circuit configuration and blunting the drive waveform of the drive signal output to the stepping motor has been proposed (patent) Reference 2). Thereby, the radiation noise by the operation | movement of a switching element can be reduced. In this technique, it is necessary to dull the drive waveform of the drive signal in consideration of the trade-off between the heat generation amount of the switching element and the radiation noise so as not to hinder the function expression of the switching element.

  Incidentally, the radiation noise is caused by a cable disposed between the stepping motor and the driver that drives the stepping motor, in addition to the noise caused by the operation of the switching element. FIG. 9 is an explanatory view showing a conventional motor driving device. FIG. 10 is an explanatory view showing a conventional stepping motor mounting structure. FIG. 11 is an explanatory view showing a terminal board of a motor driving device attached to a conventional stepping motor.

  In FIG. 9, reference numeral 1 denotes a metal casing of a device on which the stepping motor 200 is mounted. The stepping motor 200 is driven by the motor driving device 100.

  The stepping motor 200 is of a two-phase type, and includes a metal frame 2, a stator (not shown) having windings, and a rotor (not shown) arranged at the center of the stator. A gear 10 is attached to the rotating shaft of the rotor. Then, when attaching the stepping motor 200 to the metal casing 1, as shown in FIG. 10, the gear 10 is inserted into the hole 13 formed in the metal casing 1, and the screw 9 is formed in the metal casing 1. The metal frame 2 is fixed to the metal housing 1 by being screwed into the hole 12.

  As shown in FIG. 9, the motor driving device 100 includes a driver IC 3 that drives the stepping motor 200, a driver board 4 on which the driver IC 3 is mounted, and a board connector 5 that is mounted on the driver board 4. In addition, the motor driving device 100 draws the four cables 6 for transmitting a driving signal to the windings of the stepping motor 200 and the two ends of the two windings inside the stepping motor 200 to the outside of the metal frame 2. And four winding terminals 7. In addition, the motor driving device 100 includes a terminal board 8 on which the winding terminals 7 are mounted.

  The driver substrate 4 is fixed to the metal housing 1, and the ground terminal of the driver IC 3 is grounded to the metal housing 1.

  As shown in FIG. 10, the metal frame 2 of the stepping motor 200 has an opening 11 for exposing the winding terminal 7 to the outside of the metal frame 2 in order to connect the terminal substrate 8 to the winding terminal 7. Yes.

  As shown in FIG. 11, the terminal board 8 includes four wiring patterns 14 connected to each of the four winding terminals 7 and a board connector 15 for connecting the cable 6.

  FIG. 12 is a circuit diagram showing a circuit configuration of a conventional motor driving apparatus. However, the circuit shown in FIG. 12 shows only one-phase drive circuit among the two-phase drive circuits constituting the motor drive device 100.

  In FIG. 12, reference numeral 16 denotes a stator winding of the stepping motor 200. A drive current i1 that is a drive signal transmitted to the winding 16 flows in one of the two cables 6, and a drive current i2 that has passed through the winding 16 flows in the other. Here, the drive currents i1 and i2 are so-called differentially flowing currents and have phases opposite to each other. However, the balance between the cables 6 tends to be unbalanced due to a difference in length between the paired cables 6 or a difference in distance to the metal housing 1. Due to this imbalance, the drive currents i1 and i2 flowing through the two cables 6 do not have completely opposite phases, but in reality, a current flowing in the same phase through the two cables 6, that is, a so-called common mode current ic flows.

  The common mode current ic is fed back from the winding 16 to the driver IC 3 via the metal frame 2, the metal housing 1, and the ground of the driver board 4. Radiation noise N called common mode noise can be reduced by canceling out the magnetic field generated by the feedback current ir flowing through the feedback route with the opposite magnetic field generated by the common mode current ic.

Japanese Patent Laid-Open No. 9-93992 Japanese Patent Laid-Open No. 2003-189592

  However, since the winding 16 and the metal frame 2 are insulated and are coupled to each other with a minute stray capacitance, the impedance between the two is high. Therefore, a sufficient feedback current ir cannot be passed through the metal housing 1. As a result, the magnetic field due to the common mode current ic of the cable 6 cannot be canceled out by the magnetic field due to the feedback current ir of the metal housing 1 in the vicinity of the cable 6, and the effect of reducing the radiation noise N is insufficient. was there.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor drive device that allows a common mode current to flow smoothly through a metal frame and reduces radiation noise caused by the common mode current.

  The present invention provides a motor driving device including a driver for driving a stepping motor in which a stator having windings and a rotor rotating with respect to the stator are housed in a metal frame. A winding terminal that is connected and exposed to the outside of the metal frame; and a cable that is disposed between the driver and the winding terminal and transmits a drive signal output from the driver to the winding. A capacitive element disposed between the metal frame and the winding terminal for returning a common mode current flowing through the cable to the driver through the metal frame. It is a feature.

  The present invention also provides a motor drive device comprising a metal frame and a driver for driving a stepping motor in which a stator having windings and a rotor rotating with respect to the stator are housed. A winding terminal connected to a point and exposed to the outside of the metal frame, and disposed between the driver and the winding terminal, for transmitting a drive signal output from the driver to the winding A capacitive element disposed between the cable, the metal frame and the winding terminal, and for returning a common mode current flowing up to the midpoint of the winding to the driver via the metal frame; It is characterized by having.

  According to the present invention, the common mode current can be smoothly passed through the metal frame, and radiation noise caused by the common mode current can be reduced.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is an explanatory view showing a motor drive device according to a first embodiment of the present invention, and FIG. 2 is an explanatory view showing a terminal board attached to a stepping motor. Moreover, FIG. 3 is explanatory drawing which shows schematic structure of a stepping motor.

  1 shown in FIG. 1 is a metal casing of a device on which the stepping motor 200 is mounted. The stepping motor 200 is driven by the motor driving device 100A.

  In the first embodiment, the stepping motor 200 is a two-phase bipolar type. As shown in FIG. 3, the stepping motor 200 includes a metal frame 2, a stator 201 having two windings 16 a and 16 b, a rotor 202 that is disposed at the center of the stator 201 and rotates with respect to the stator 201, It has. The stator 201 and the rotor 202 are housed in the metal frame 2. A gear 10 is attached to the rotation shaft of the rotor 202. As shown in FIG. 1, the metal frame 2 of the stepping motor 200 is attached to the metal casing 1 of the device with screws 9 and is grounded to the metal casing 1.

  The motor drive device 100A includes a driver IC 3 as a driver that outputs a drive signal to drive the stepping motor 200, a driver board 4 on which the driver IC 3 is mounted, and a board connector 5 mounted on the driver board 4. Yes. The motor driving device 100A is connected to both ends of two windings 16a and 16b inside the stepping motor 200, and is exposed to four winding terminals 7 (7a, 7b, 7c and 7d) exposed to the outside of the metal frame 2. ). Further, the motor driving device 100A includes four cables 6 disposed between the driver IC 3 and the winding terminal 7 and the winding terminal 7 in order to transmit a drive signal to the winding of the stepping motor 200. And a terminal board 8 as a wiring board to be mounted.

  The driver board 4 is fixed to the metal housing 1. The ground terminal of the driver IC 3 is connected to the ground wiring of the driver substrate 4, and the ground wiring is connected and fixed to the metal housing 1. As a result, the ground terminal of the driver IC 3 is grounded to the metal housing 1.

  As shown in FIG. 2, the terminal board 8 is a board connector for connecting the four wiring patterns 14a, 14b, 14c, 14d connected to each of the four winding terminals 7a, 7b, 7c, 7d and the cable 6. 15.

  Specifically, the stepping motor 200 has two windings, a first phase winding 16a and a second phase winding 16b, and one end of the first phase winding 16a has a first winding. The line terminal 7a is connected, and the second winding terminal 7b is connected to the other end of the first phase winding 16a. The third winding terminal 7c is connected to one end of the second phase winding 16b, and the fourth winding terminal 7d is connected to the other end of the second phase winding 16b. The terminal board 8 includes a first wiring pattern 14a to which the first winding terminal 7a is connected and a second wiring pattern 14b to which the second winding terminal 7b is connected. . Further, the terminal board 8 has a third wiring pattern 14c to which the third winding terminal 7c is connected and a fourth wiring pattern 14d to which the fourth winding terminal 7d is connected. .

  Each wiring pattern 14a-14d is formed in strip shape, and is arrange | positioned on the terminal board 8 in parallel mutually at intervals. A board connector 15 for connecting to the cable 6 is disposed near one end of each of the wiring patterns 14a to 14d.

  Winding terminals 7a to 7d are connected near the other ends of the wiring patterns 14a to 14d, respectively.

  In the first embodiment, the terminal board 8 has a ground wiring pattern 18 that is electrically connected to the metal frame 2 so as to surround the four wiring patterns 14a to 14d.

  The ground wiring pattern 18 is formed on the surface of the terminal substrate 8 on which the wiring patterns 14 a to 14 d are formed, and is formed so as to cover substantially the entire back surface of the terminal substrate 8.

  The motor drive device 100 </ b> A includes four capacitors 17 a to 17 d as four capacitive elements disposed between the metal frame 2 and the winding terminal 7.

  More specifically, one end of the first capacitor 17a is connected to the other end of the first wiring pattern 14a, and the other end of the first capacitor 17a is connected to the ground wiring pattern 18. One end of the second capacitor 17 b is connected to the other end of the second wiring pattern 14 b, and the other end of the second capacitor 17 b is connected to the ground wiring pattern 18. Further, one end of the third capacitor 17 c is connected to the other end of the third wiring pattern 14 c, and the other end of the third capacitor 17 c is connected to the ground wiring pattern 18. One end of the fourth capacitor 17d is connected to the other end of the fourth wiring pattern 14d, and the other end of the fourth capacitor 17d is connected to the ground wiring pattern 18. Therefore, the capacitors 17a to 17d are connected to the end of the cable 6 (the end of the cable 6 opposite to the driver IC 3), specifically, to the end (the other end) of the wiring pattern 14a. Become.

  As described above, the capacitors 17 a to 17 d are mounted on the terminal board 8. Thus, since the terminal board 8 may be attached to the stepping motor 200 in a state where the capacitors 17a to 17d are mounted on the terminal board 8, the attaching operation is simple.

  By the way, the ground wiring pattern 18 to which the capacitors 17a to 17d are connected can be connected to the metal frame 2 with solder or the like via lead wires, connected only with solder, or connected with a conductive screw. A connection method is possible.

  However, since the lead wire method has a high impedance in the high frequency region due to the lead wire inductance, the effect of reducing radiation noise may be reduced. Further, in the method of directly connecting with solder, there is a possibility that the solder melts when the metal frame 2 becomes high temperature by the operation of the stepping motor 200. In addition, when soldering, there is a possibility that the insulation of the winding is melted. Further, in the method of connecting with screws, since it is necessary to make screw holes in the metal frame 2, it is necessary to prevent the screws from coming into contact with the internal equipment of the stepping motor 200, and the metal frame 2 must be enlarged. Moreover, when the metal frame 2 is enlarged, an air layer is formed between the internal device and the heat dissipation effect of the internal device may be reduced.

  Therefore, the motor drive device 100A of the first embodiment includes a conductive leaf spring 27 that is fixed to the region 28 of the ground wiring pattern 18 on the back surface of the terminal substrate 8 in the vicinity of the capacitors 17a to 17d. Yes.

  As shown in FIG. 1, the leaf spring 27 contacts the metal frame 2 when the terminal board 8 is disposed in the vicinity of the metal frame. At this time, the leaf spring 27 is pressed against the metal frame 2 by its urging force, so that contact failure does not occur and the state in which the leaf spring 27 is in good contact with the metal frame 2 can be maintained.

  Thereby, the ground wiring pattern 18 is electrically connected to the metal frame 2 with a simple configuration by the leaf spring 27.

  And since the leaf | plate spring 27 is being fixed to the other end (terminal) side of the wiring patterns 14a-14d of the terminal board 8 in the ground wiring pattern 18, it is from the terminal of wiring patterns 14a-14d to the metal frame 2. The distance is short. Therefore, the impedance between the wiring patterns 14a to 14d and the metal frame 2 is low, and the common mode current flows favorably.

  FIG. 4 is a circuit diagram showing a circuit configuration of the motor drive device 100A according to the first embodiment of the present invention. However, the circuit shown in FIG. 4 shows only one-phase driving circuit among the two-phase driving circuits constituting the motor driving device 100A, but the driving circuit not shown is the same as the driving circuit shown in FIG. It is the same composition.

  In FIG. 4, reference numeral 16 denotes one of the two windings 16 a and 16 b of the stepping motor 200. A drive current i1 that is a drive signal transmitted to the winding 16 flows in one of the two cables 6, and a drive current i2 that has passed through the winding 16 flows in the other. Here, the drive currents i1 and i2 are so-called differentially flowing currents. When the balance between the paired cables 6 becomes unbalanced due to the difference in the length between the paired cables 6 or the difference in the distance to the metal housing 1, A common mode current ic flows through the cable 6 in the same direction.

  This common mode current ic passes from the terminal end of the cable 6 (specifically, the terminal end of the wiring pattern 14) to the driver IC 3 via the capacitor 17, via the metal frame 2, the metal housing 1, and the ground of the driver board 4. Return.

  That is, since the capacitor 17 has a low impedance with respect to the common mode current ic, the common mode current ic flows through the metal frame 2 smoothly. The magnetic field generated by the feedback current ir flowing through the feedback route cancels out the opposite magnetic field generated by the common mode current ic, and radiation noise caused by the common mode current called common mode noise can be reduced. .

  If a capacitor is connected at the beginning of the cable 6 or in the middle thereof, a common mode current may be generated in the section from the connection point of the capacitor cable 6 to the terminal end of the cable 6, and is generated in that section. The common mode current may not be returned.

  In contrast, in the first embodiment, since the common mode current ic is fed back to the metal frame 2 from the end of the cable 6, the common mode current ic is more effectively passed to the driver IC 3 via the metal frame 2. It can be returned.

  FIG. 5 is a diagram illustrating an example in which the radiation noise level is measured. FIG. 5A is a diagram showing a measurement result in the conventional motor drive device, and FIG. 5B is a diagram showing a measurement result in the motor drive device of the first embodiment. The configuration conditions of the motor drive device were set such that the length of the cable 6 was 500 mm, the height from the metal housing 1 to the cable 6 was 10 mm, and the capacitor 17 mounted on the terminal board 8 was 1000 pF. As shown in FIG. 5, in this experiment, a radiation noise reduction of about 8 dB was confirmed at 55 MHz.

[Second Embodiment]
Next, the motor drive device of 2nd Embodiment is demonstrated. Note that in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 is a circuit diagram showing a circuit configuration of a motor drive device 100B according to the second embodiment of the present invention, and FIG. 7 is an explanatory diagram showing a terminal board 8A attached to the stepping motor. In FIG. 6, only the one-phase drive circuit is illustrated among the two-phase drive circuits constituting the motor drive device 100B, but the drive circuit (not shown) has the same configuration as the drive circuit of FIG. It is.

  As shown in FIG. 6, the motor driving device 100 </ b> B includes a winding terminal 19 that is connected to the midpoint of the winding 16 of the stepping motor and is exposed to the outside of the metal frame 2. The midpoint of the winding 16 is a point where the inductances are equal to each other when the winding 16 is divided into two.

  The motor drive device 100 </ b> B of the second embodiment includes a capacitor 21 as a capacitive element disposed between the metal frame 2 and the winding terminal 19.

  The specific configuration will be described with reference to FIG. 7. The fifth winding terminal 19a is connected to the wiring drawn from the middle point of the first phase winding and drawn from the middle point of the second phase winding. A sixth winding terminal 19b is connected to the wiring. The terminal board 8A is formed with two wiring patterns including fifth and sixth wiring patterns 20a and 20b. The fifth wiring pattern 20a is connected to the fifth winding terminal 19a, and A sixth winding terminal 19b is connected to the sixth wiring pattern 20b. Thus, the fifth and sixth winding terminals 19a and 19b are mounted on the terminal board 8A.

  The motor driving device 100B includes capacitors 21a and 21b that are two capacitive elements disposed between the metal frame 2 and the winding terminals 19a and 19b.

  More specifically, one end of the first capacitor 21a is connected to the fifth wiring pattern 20a, and the other end of the first capacitor 21a is connected to the ground wiring pattern 18. One end of the second capacitor 21 b is connected to the sixth wiring pattern 20 b, and the other end of the second capacitor 21 b is connected to the ground wiring pattern 18.

  Thus, the two capacitors 21a and 21b are mounted on the terminal board 8A.

  With this configuration, the common mode current ic flowing to the middle point of the winding 16 shown in FIG. 6 is fed back to the driver IC 3 by the capacitor 21 via the metal frame 2.

  In the second embodiment, the number of capacitors 21 can be reduced from four to two, and a noise reduction effect can be obtained with a more inexpensive configuration.

  Further, since the capacitor 21 is connected to the midpoint of the winding 16, not only the common mode current generated in the cable 6, but also the common mode current generated by the unbalance between pairs generated in the winding 16 portion is the driver. It can be returned to IC3. Therefore, the common mode current generated in the winding 16 can also be fed back, and the radiation noise generated by this common mode current can be reduced, so that the effect of reducing the radiation noise can be enhanced.

[Third Embodiment]
FIG. 8 is an explanatory view showing a terminal board in the motor drive device of the third embodiment according to the present invention. Note that in the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the first embodiment, the ground wiring pattern and the metal frame are electrically connected by the leaf spring 27. However, in the third embodiment, the ground wiring pattern 18 and the metal frame are bonded by the conductive member 30. Is electrically connected.

  The conductive member 30 is a conductive paste or conductive gasket having adhesiveness.

  When the conductive member 30 is a conductive paste, the conductive paste may be applied to the ground wiring pattern 18 on the back surface of the terminal substrate 8B and adhered to the metal frame.

  When the conductive member 30 is a conductive gasket, the conductive gasket may be attached to the ground wiring pattern 18 on the back surface of the terminal substrate 8B and bonded to the metal frame.

  Regardless of whether the conductive member 30 is a conductive paste or a conductive gasket, the effect of reducing radiation noise is almost the same as that of the first embodiment.

  And in this 3rd Embodiment, since it adhere | attached with the electroconductive member 30 which consists of an electroconductive paste or an electroconductive gasket, it is not necessary to connect with a lead wire, solder, a screw, etc., and it can connect simply. It becomes possible.

  In addition, although the case where the plate spring 27 of the first embodiment is changed to the conductive member 30 has been described, the case where the plate spring 27 of the second embodiment is changed to the conductive member 30 is also applicable. Needless to say, the same effect can be obtained in this case.

  As mentioned above, although this invention was demonstrated based on the said 1st-3rd embodiment, this invention is not limited to this.

  In the first to third embodiments, the motor driving device applied to the two-phase stepping motor has been described. However, the present invention is not limited to this. For example, the present invention can also be applied to a motor drive device that drives a multi-phase stepping motor such as a 5-phase stepping motor.

It is explanatory drawing which shows the motor drive device of 1st Embodiment which concerns on this invention. It is explanatory drawing which shows the terminal board attached to a stepping motor. It is explanatory drawing which shows schematic structure of a stepping motor. It is a circuit diagram which shows the circuit structure of the motor drive device of 1st Embodiment which concerns on this invention. It is a figure which shows the example which measured the radiation noise level. (A) is a figure which shows the measurement result in the conventional motor drive device, (b) is a figure which shows the measurement result in the motor drive device of this 1st Embodiment. It is a circuit diagram which shows the circuit structure of the motor drive device of 2nd Embodiment which concerns on this invention. It is explanatory drawing which shows the terminal board attached to a stepping motor. It is explanatory drawing which shows the terminal board in the motor drive device of 3rd Embodiment which concerns on this invention. It is explanatory drawing which shows the conventional motor drive device. It is explanatory drawing which shows the attachment structure of the conventional stepping motor. It is explanatory drawing which shows the terminal board of the motor drive device attached to the conventional stepping motor. It is a circuit diagram which shows the circuit structure of the conventional motor drive device.

Explanation of symbols

2 Metal frame 3 Driver IC (driver)
6 Cable 7a, 7b, 7c, 7d Winding terminal 8, 8A, 8B Terminal board (wiring board)
14a, 14b, 14c, 14d Wiring patterns 16a, 16b Windings 17a, 17b, 17c, 17d Capacitors (capacitive elements)
18 Ground wiring patterns 19a, 19b Winding terminals 20a, 20b Wiring patterns 21a, 21b Capacitors (capacitive elements)
27 Leaf Spring 30 Conductive Member 100A, 100B Motor Drive Device 200 Stepping Motor

Claims (7)

In a motor drive device comprising a driver that drives a stepping motor in which a stator having windings and a rotor that rotates relative to the stator are housed in a metal frame,
A winding terminal connected to an end of the winding and exposed to the outside of the metal frame;
A cable disposed between the driver and the winding terminal for transmitting a drive signal output from the driver to the winding;
A capacitive element disposed between the metal frame and the winding terminal for returning a common mode current flowing through the cable to the driver via the metal frame;
The motor drive device characterized by the above-mentioned. In a motor drive device comprising a driver that drives a stepping motor in which a stator having windings and a rotor that rotates relative to the stator are housed in a metal frame,
A winding terminal connected to a midpoint of the winding and exposed to the outside of the metal frame;
A cable disposed between the driver and the winding terminal for transmitting a drive signal output from the driver to the winding;
A capacitive element disposed between the metal frame and the winding terminal for returning a common mode current flowing up to the middle point of the winding to the driver via the metal frame; ,
The motor drive device characterized by the above-mentioned. A wiring board having a wiring pattern connected to the winding terminal and a ground wiring pattern connected to the metal frame,
One end of the capacitive element is connected to the wiring pattern, the other end is connected to the ground wiring pattern, and the capacitive element is mounted on the wiring board.
The motor drive device according to claim 1 or 2, wherein A conductive leaf spring fixed to the ground wiring pattern;
The wiring board is disposed in the vicinity of the metal frame, and the leaf spring is brought into contact with the metal frame.
The motor driving device according to claim 3. A conductive member for bonding the ground wiring pattern and the metal frame;
The motor driving device according to claim 3. The conductive member is a conductive paste;
The motor driving device according to claim 5, wherein The conductive member is a conductive gasket;
The motor driving device according to claim 5, wherein

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