JP3739259B2 - Brushless motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brushless motor used as a video capstan motor or the like. More specifically, the present invention relates to a PWM (Pulse Width Modulation) type brushless motor.
[0002]
[Prior art]
As shown in FIG. 1, a video capstan motor or the like includes a rotor 5 that rotates integrally with a rotary shaft 10 that is rotatably supported by a bearing 20, and a stator core 32 around which a drive coil 31 is wound. A brushless motor 1 is used that includes a motor board 30 and a motor drive circuit 60 including a drive IC configured on the iron board 40. The brushless motor 1 employs a direct PWM method in which the power transistor (switching element) of the motor drive circuit 60 is turned on / off and the energization of the drive coil 31 is controlled by modulating the switching pulse width for the switching element. ing.
[0003]
In this PWM system, the wasted power consumed by the heat generated by the conventional motor drive circuit can be significantly reduced, which has a great effect on energy saving when driving the motor. In addition, when this method is adopted, there is almost no addition of new parts, which is excellent in terms of cost.
[0004]
This PWM method will be described with reference to FIGS. 2 (A), 2 (B), 3 and 4. FIG. FIG. 2A is an explanatory diagram showing a state in which power is supplied from a motor power supply to a drive coil in a motor drive circuit of a brushless motor adopting a direct PWM method, and FIG. It is explanatory drawing which shows a mode that a regenerative current flows with the counter electromotive force which generate | occur | produced in the drive coil when the electric power supply to a drive coil was stopped. FIG. 3 is a waveform diagram showing a voltage waveform and a current waveform applied to the drive coil for one phase when the control as shown in FIGS. 2A and 2B is performed. FIG. 4 is a waveform diagram showing a voltage waveform and a current waveform in the period b in which a voltage is applied to the drive coil and in the period c in which the voltage application to the drive coil is suspended in the period a shown in FIG. is there.
[0005]
Among these figures, as shown in FIGS. 2A and 3, when the power transistor Q4 is on and the power transistor Q1 is on, the power supply VM is applied to the drive coil 31 from the motor power supply 66. Thus, a current flows through the drive coil 31, and this current flows through the power transistor Q4 to the ground M-GND of the motor power supply 66 (period b in FIG. 4). As shown in FIG. 4, the motor current gradually increases corresponding to the time constant of the drive coil 31.
[0006]
On the other hand, as shown in FIGS. 2B and 3, when the power transistor Q <b> 1 is turned off while the power transistor Q <b> 4 is on, the application of the power source VM from the motor power source 66 to the drive coil 31 is interrupted. . However, back electromotive forces E1 and E2 are generated in each drive coil 31 at this time, and a regenerative current flows through the drive coil 31 as a motor current through the diode 61 by the back electromotive forces E1 and E2. As shown in FIG. 4, this regenerative current gradually decreases in accordance with the time constant of the drive coil 31, but before it completely decreases, the power transistor Q1 is turned on to supply current from the motor power supply 66. Will be.
[0007]
As described above, in the brushless motor 1, since a part of the motor current is covered by the regenerative current, the current (electric power) supplied from the outside can be saved. Further, since the power transistor through which the motor current flows is always in a saturated state, the power consumed by the motor drive circuit 60 can be minimized.
[0008]
[Problems to be solved by the invention]
However, in the brushless motor 1 adopting the direct PWM method, the voltage applied to the drive coil 31 fluctuates in a short period between the drive power supply VM and the ground potential M-GND. Since both of the voltage applied to the wiring leading to the coil 31 and the voltage applied to the drive coil 31 repeat abrupt fluctuations continuously, electromagnetic noise is generated and the operation of the device equipped with this motor is performed. Various adverse effects. Further, in a motor component that is capacitively coupled to the drive coil 31 and wiring, for example, a stator core 32 around which the drive coil 31 is wound, or an iron substrate 40 (metal substrate) serving as a circuit board of the motor, The iron plate portion sandwiching the insulating layer between the wirings provided on 40 causes the electromagnetic noise to diffuse.
[0009]
Furthermore, the current supply from the motor power supply 66 is performed only during the period b shown in FIG. 4, and is interrupted during the period c following the period b. For this reason, a pulse current that is turned on and off at the PWM carrier frequency flows through the wiring of the motor power supply 66 provided on the iron substrate 40, and this pulse current also diffuses electromagnetic noise. In addition, the pulse current causes a failure in the operation of the device by generating ripples in the motor power supply 66.
[0010]
In view of the above problems, an object of the present invention is to provide a configuration capable of suppressing the generation of electromagnetic noise in a brushless motor employing a PWM method.
[0011]
[Means for Solving the Problems]
  In order to solve the above-described problem, in the first invention of the present application, the switching element of the motor driving circuit is directly turned on / off, and the switching pulse width for the switching element is modulated to thereby energize the motor driving coil. In a direct PWM brushless motor that controls the rotor, a rotor that rotates integrally with a rotating shaft that is rotatably supported by a bearing, a stator that includes a stator core around which a drive coil is wound, a metal substrate, and the metal substrate A metal plate that forms the metal substrateTheInsulation resistance between the metal plate and the attachment part to the chassis on the main body side where the motor is attached while being short-circuited to a fixed potential by a conductive connecting memberThe1kΩ or moreAnd 100 kΩ or lessIt is characterized by that.
[0012]
  In the present invention, when a brushless motor is driven by the direct PWM method, even if the voltage applied to the wiring from the motor drive circuit to the drive coil and the voltage applied to the drive coil itself repeat abrupt fluctuations, Metal plates as bases of metal substrates each having capacitive couplingButBecause it is fixedMetal plateCan prevent electromagnetic noise from diffusing.
[0013]
  In the present invention, the metal plate and the stator core are connected to each other by the connecting member and connected to the wiring pattern connected to the fixed potential, so that both the metal plate and the stator core are It is preferably connected to the fixed potential.Since the potential of the stator core is fixed, the stator core can be prevented from diffusing electromagnetic noise.
[0014]
In the present invention, the fixed potential is either a ground potential or a power supply potential of the motor driving circuit.
[0015]
In the present invention, it is preferable that a capacitor having a capacitance of 0.1 μF or more is electrically connected in parallel with the motor power supply between the motor drive circuit and the motor power supply. That is, in the present invention, it is preferable that a capacitor having a capacitance of 0.1 μF or more is electrically connected in parallel with the motor power supply at a position close to the motor drive circuit. With this configuration, even if a pulse current flows through the wiring of the motor power supply, the capacitor absorbs ripples from the motor power supply, so that a device equipped with this motor can operate normally.
[0016]
  In the present invention, the attachment portion of the motor to the main body side chassisWhenThe insulation resistance with respect to the stator core is preferably 1 kΩ or more and 100 kΩ or less.
[0017]
In the present invention, when the attachment portion of the motor to the body-side chassis is formed of a conductive resin bearing holder that holds the bearing, an insulation resistance of the bearing holder is 1 kΩ or more, and 100 kΩ or less is preferable. With this configuration, when a pulley is configured on the rotor, static electricity may be generated due to sliding between the pulley and the connecting belt. If the insulation resistance of the bearing holder is within the above range, the rotor The static electricity accumulated in can be released from the bearing holder. Further, even if the stator core or the like is held at the ground potential, if the bearing holder is a conductive resin, even if the bearing holder is fixed to the main body side chassis, the main body side chassis is short-circuited to the ground potential M-GND of the motor. There is no trouble in the operation of the equipment.
[0018]
In the present invention, when the attachment portion to the body-side chassis in the motor is formed by a metal bearing holder holding the bearing, between the bearing holder and the metal plate, It is preferable that both the bearing holder and the stator core have an insulation resistance of 1 kΩ or more and 100 kΩ or less.
[0019]
When configured in this way, the bearing holder is formed with a hole embedded with a conductive resin screw receiver, and the screw receiver has a screw for fixing the bearing holder and the body-side chassis. A stopped configuration can be employed. With this configuration, even when a pulley is configured on the rotor, the bearing holder is made of metal and is in contact with the chassis on the main body side with a screw receiver made of conductive resin. Static electricity can be released.
[0020]
  In a second invention of the present application, a direct PWM brushless motor that directly turns on / off a switching element of a motor drive circuit and controls energization of a motor drive coil by modulating a switching pulse width for the switching element. And a rotor that rotates integrally with a rotary shaft that is rotatably supported by a bearing, a stator that includes a stator core around which the drive coil is wound, and a circuit that includes a circuit pattern for energizing the drive coil A metal plate having a metal substrate constituting the substrate and the motor drive circuit configured on the metal substrate, the metal plate constituting the metal substrateTheShorted to a fixed potential by conductive metalIn addition, the insulation resistance between the mounting portion of the motor on the main body side chassis and the metal plate in the motor is 1 kΩ or more and 100 kΩ or less.It is characterized by.
[0021]
In the present invention, the metal plate and the stator core are electrically connected to each other by the conductive metal material, a wiring pattern connected to the fixed potential is formed on the circuit board, and the metal plate and the stator core It is preferable that both the metal plate and the stator core are connected to the fixed potential by being electrically connected to the wiring pattern.
[0022]
Also in the present invention, as in the first invention, the fixed potential is either the ground potential or the power supply potential of the motor drive circuit.
[0023]
In the present invention, the conductive metal material includes a first conductive metal material that electrically connects the metal plate and the stator core, and a land portion that is connected to the wiring pattern at a predetermined position of the metal plate. You may employ | adopt the structure which has a 2nd electroconductive metal material which electrically connects the said metal plate.
[0024]
  Also in the present invention, as in the first invention, the mounting portion of the motor with the main body side chassis.WhenThe insulation resistance with respect to the stator core is preferably 1 kΩ or more and 100 kΩ or less.
[0025]
Also in the present invention, as in the first invention, a capacitor having a capacitance of 0.1 μF or more is electrically connected in parallel with the motor power supply between the motor drive circuit and the motor power supply. Is preferred.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In each of the embodiments described below, the basic configuration is the same as that of the conventional embodiment, and thus the same reference numerals are given to these common portions.
[0027]
[Embodiment 1]
FIG. 1 is a side view in which a part of a brushless motor to which the present invention is applied is cut away.
[0028]
As can be seen from FIG. 1, the brushless motor 1 includes a rotor 5 with a pulley 55 that rotates integrally with a rotating shaft 10, a stator 30 that includes a stator core 32 around which a drive coil 31 is wound, and a metal that also serves as a circuit board. It has an iron substrate 40 which is a substrate, and a motor drive circuit 60 provided with a circuit pattern, a drive IC and the like mounted on the lower surface side of the iron substrate 40. A circuit pattern for connecting the motor drive circuit 60 and the drive coil 31 wound around the stator core 32 is formed on the iron substrate 40.
[0029]
Further, the cylindrical bearing holder 25 attached to the iron substrate 40 is formed with an attachment portion for screwing to the chassis of the main device to which the present motor is attached. The brushless motor 1 includes the bearing holder 25. The mounting portion is fixed to the chassis of the main device by screws and fixed to the chassis of the main device.
[0030]
The bearing holder 25 may be formed of a conductive resin, and a metal bearing holder 25 may be used as in the fourth embodiment described later. When the bearing holder 25 is formed of a conductive resin, for example, engineer plastic can be mixed with conductive carbon to have a predetermined conductivity.
[0031]
The magnetic sensor 7 is mounted on the iron substrate 40 via a sensor holder 70 so that an FG output can be obtained by a magnetic pattern provided on the outer peripheral portion 51 of the rotor 5.
[0032]
A pair of upper and lower bearings 20 such as sintered bearings are held inside the bearing holder 25, and the rotary shaft 10 is passed through the bearing 20. Further, a stator core 32 is held on the outer peripheral surface of the bearing holder 25 by using a step formed on the outer peripheral surface of the bearing holder 25, and a resin core holder 33 is covered on the stator core 32. Further, the core holder The iron substrate 40, the core holder 33, and the stator core 32 are fixed with screws 35 in a state where the iron substrate 40 is covered on 33. Note that the drive coil 31 is wound around the stator core 32 as usual, and a drive magnet (not shown) is attached to the inner peripheral surface of the rotor 5 so as to face the outer peripheral surface of the stator core 32. And constitutes a motor.
[0033]
The brushless motor 1 configured as described above has the power transistor Q4 turned on and the power transistor Q1 turned on in the motor drive circuit 60, as described with reference to FIGS. By alternately switching between the state and the state where the power transistor Q4 is on and the power transistor Q1 is off, a part of the motor current is covered by the regenerative current.
[0034]
However, in the brushless motor 1 employing such a direct PWM method, as described above, the voltage applied to the drive coil 31 fluctuates within a short period between the drive power supply VM and the ground potential M-GND. Therefore, the voltage applied to the wiring formed on the iron substrate 40 from the motor drive circuit 60 to the drive coil 31 and the voltage applied to the drive coil 31 itself continuously repeat abrupt fluctuations, generating electromagnetic noise. Easy to make. However, in this embodiment, the electromagnetic noise is prevented from diffusing by being configured as follows.
[0035]
FIG. 5 is a cross-sectional view of the direct PWM brushless motor of this embodiment in which a short circuit structure is applied to the iron substrate and the stator core.
[0036]
In FIG. 5, a metal tap screw 35 that is a connecting member of a conductive metal material is stopped from a flange portion 251 of the bearing holder 25 made of a conductive resin toward the iron substrate 40. The tap screw 35 collectively fixes the flange portion 251 of the bearing holder 25, the stator core 32, the core holder 33, and the iron substrate 40.
[0037]
Here, in the iron substrate 40 to which the metal tap screw 35 is fixed, the upper surface side of the iron plate portion 41 constituting the metal plate of the metal substrate is exposed, and an insulating layer is formed on the lower surface of the iron substrate 40. 42 is formed. A wiring pattern 43 to which the ground potential M-GND is applied is drawn around at a position on the lower surface of the insulating layer 42 where the tap screw 35 is screwed, and the thread of the tap screw 35 has an optimum dimension. Therefore, the iron plate portion 41 of the iron substrate 40 is connected to the wiring pattern 43 via the tap screw 35 and is short-circuited to the ground potential M-GND. The stator core 32 is also connected to the wiring pattern 43 via the tap screw 35 and short-circuited to the ground potential M-GND.
[0038]
Therefore, in this embodiment, when the brushless motor 1 is driven by the direct PWM method, the wiring extending from the motor drive circuit 60 to the drive coil 31 wound around the stator core 32, the voltage applied to the circuit pattern, and the drive coil 31 itself Even if such a voltage repeats abrupt fluctuations continuously, the potential of the iron plate portion 41 or the stator core 32 of the iron substrate 40 that is capacitively coupled to each of these voltages is changed to the ground potential M− via the tap screw 35. Since it is short-circuited or fixed to GND, these motor components will not spread electromagnetic noise. In the above-described embodiment, the tap screw 35 is used as a conductive connecting member for short-circuiting the iron plate portion 41 or the stator core 32 to the ground potential M-GND. As long as a general connection can be achieved.
[0039]
Moreover, in the said embodiment, it has the structure which has arrange | positioned the wiring pattern for ground of the iron substrate 40 in the part to which the stator core 32 and the iron plate part 41 are screwed, and was electrically connected to this wiring pattern for ground. In the present embodiment, the bearing holder 25 is made of a conductive resin, and the bearing holder 25 is fixed to a chassis (not shown) on the main device side via an attachment portion provided on the bearing holder 25. The stator core 32 and the iron plate portion 41, that is, the ground wiring, are electrically insulated from the main body chassis with an insulation resistance of 1 kΩ or more and 100 kΩ or less. Therefore, even when the chassis is the ground of the entire main device, the chassis does not short-circuit with the motor ground potential M-GND, so that the operation of the device is not hindered.
[0040]
The bearing holder 25 formed of a conductive resin preferably has an insulation resistance of 100 kΩ or less with respect to the chassis on the main body side, but even if it has an insulation resistance of 1 MΩ or less, there is a case where there is no problem in operation. The insulation resistance may be set as appropriate. For example, static electricity accumulated when the pulley 55 is rotated by putting a belt on the pulley 55 can be released to the chassis on the main body side via the bearing holder 25, or the static electricity generated in the motor It should be determined in consideration of whether it will adversely affect the system. From this viewpoint, it is preferable that the bearing holder 25 has an insulation resistance of 100 kΩ or less with respect to the chassis.
[0041]
[Embodiment 2]
In the iron substrate 40, which is a metal substrate, a structure in which an iron plate portion 41 serving as a metal plate of the metal substrate is short-circuited to the ground potential M-GND, that is, as a connecting member, as shown in FIG. The iron plate portion 41 may be short-circuited to the ground potential M-GND using the sensor holder 70 fixed to the substrate 40.
[0042]
FIG. 6 is a cross-sectional view showing a structure in which the iron plate portion 41 of the iron substrate 40 is short-circuited to the ground potential M-GND using the sensor holder 70 in the brushless motor 1 of the present embodiment.
[0043]
As shown in FIG. 6, the sensor holder 70 is obtained by processing a conductive metal plate. The sensor holder 70 is fixed to the sensor holding portion 71 that holds the magnetic sensor 7 and the through hole 44 that is opened in the iron substrate 40. A claw portion 72 is formed. Here, the fixing claw portion 72 is bent with respect to the iron plate portion 41 through the through hole 44 of the iron substrate 40 and is in contact with the exposed surface of the iron plate portion 41. The sensor holder 70 is fixed to the iron substrate 40 so as to sandwich the substrate 40. Therefore, in this state, the metal sensor holder 70 is in contact with the wiring pattern 43 of the iron substrate 40 via the soldered solder 77 and also in contact with the iron plate portion 41.
[0044]
Therefore, even when the brushless motor 1 is driven by the direct PWM method, the iron plate portion 41 of the iron substrate 40 is always held at the ground potential M-GND via the wiring pattern 43, so that the iron plate portion 41 generates electromagnetic noise. It does not spread.
[0045]
As shown in FIG. 6, not only the wiring pattern 43 and the sensor holder 70 are connected by the solder 77 but also the solder 77 is interposed in the through hole 44 of the iron substrate 40 by soldering at this time, If the solder 77 is brought into contact with the iron plate portion 41, the iron plate portion 41 can be more reliably fixed to the ground potential M-GND.
[0046]
[Embodiment 3]
As another structure in which the iron plate portion 41 in the iron substrate 40 is short-circuited to the ground potential M-GND and the stator core 32 is also short-circuited to the ground potential M-GND, as shown in FIG. The stator core 32, the core holder 33, and the iron substrate 40 are fixed together by a tap screw 35, which is a kind of connecting member of the first conductive metal material). Further, as shown in FIG. A land portion 47 of the ground potential M-GND is formed at an appropriate position of the substrate 40 at the end of the circuit pattern, and other conductive metal material is formed in a hole formed in the center of the land portion 47. The iron plate portion 41 may be short-circuited to the ground potential M-GND by screwing a metal screw 48 that is a connecting member (second conductive metal material).
[0047]
When configured in this way, the iron plate portion 41 of the iron substrate 40 can be short-circuited to the ground potential M-GND via the tap screw 35. The stator core 32 can also be short-circuited to the ground potential M-GND via the tap screw 35. In the present embodiment, since the iron plate portion 41 of the iron substrate 40 is further brought into contact with the land portion 47 via the screw 48 and short-circuited to the ground potential M-GND, it can be more reliably short-circuited. Therefore, the iron plate portion 41 of the iron substrate 40 is reliably short-circuited to the ground potential M-GND, and the stator core 32 is also reliably short-circuited to the ground potential M-GND.
[0048]
In the embodiment described above, a screw is used as the connecting member for short-circuiting, but a pin may be used as the connecting member as long as it can be fixed and connected.
[0049]
[Embodiment 4]
In the above embodiment, the bearing holder 25 is made of a conductive resin. Here, an example using a metal bearing holder 25 will be described with reference to FIG.
[0050]
FIG. 8 is a cross-sectional view showing a structure in which the stator core and the iron plate portion of the iron substrate are short-circuited to the ground potential and a structure in which the bearing holder and the chassis are fixed with a predetermined insulation resistance range in the brushless motor 1 of the present embodiment. .
[0051]
In FIG. 8, as the core holder 33, a first cylindrical portion 331 that secures insulation between the iron substrate 40 and the outer peripheral surface of the bearing holder 25, and between the inner peripheral surface of the stator core 32 and the outer peripheral surface of the bearing holder 25. Insulation between the iron substrate 40 and the bearing holder 25 and insulation between the stator core 32 and the bearing holder 25 are ensured. ing.
[0052]
Further, as a structure in which the iron plate portion 41 of the iron substrate 40 is short-circuited to the ground potential M-GND, and the stator core 32 is also short-circuited to the ground potential M-GND, the stator core 32, the core holder 33, and the iron are formed by a metal tap screw 35. The substrates 40 are fixed together, but a resin-made first insulating spacer 255 is disposed between the tap screw 35 and the bearing holder 25, and the resin is also formed between the bearing holder 25 and the stator core 32. The second insulating spacer 256 is disposed. By doing in this way, even when the iron plate portion 41 and the stator core 32 of the iron substrate 40 are short-circuited to the ground potential M-GND around the bearing holder 25, the space between the bearing holder 25 and the iron plate portion 41 of the iron substrate 40 is reduced. In addition, an insulation resistance of 1 kΩ or more can be secured between the bearing holder 25 and the stator core 32. Therefore, even if the metal bearing holder 25 is fixed to the chassis 90 on the main device side as it is, the gap between the chassis 90 and the iron plate portion 41 of the iron substrate 40 and between the chassis 90 and the stator core 32 is 1 kΩ or more. Insulation resistance can be secured.
[0053]
In the present embodiment, a conductive resin cap-like screw receiver 91 is used so that the bearing holder 25 and the chassis 90 can be fixed with a predetermined level of insulation resistance. That is, a hole 259 in which a conductive resin screw receiver 91 is embedded is formed in the bearing holder 25, and a fixing screw 95 penetrating the chassis 90 is fixed to the screw receiver 91 mounted in the hole 259. It has been.
[0054]
Therefore, in this embodiment, since the bearing holder 25 has an insulation resistance of 1 kΩ or more with respect to the chassis 90, even if the chassis 90 is the ground of the entire main device, the chassis 90 is at the motor ground potential M-GND. Since there is no short circuit, the operation of the equipment is not hindered.
[0055]
Also in this embodiment, it is preferable that the bearing holder 25 has an insulation resistance of 100 kΩ or less with respect to the chassis 90 in consideration of the fact that static electricity generated in the motor does not adversely affect the electronic components mounted on the motor. In this way, for example, static electricity accumulated when the pulley 55 is rotated by putting a belt on the pulley 55 can be released to the chassis 90 via the bearing holder 25.
[0056]
[Embodiment 5]
FIGS. 9A and 9B each prevent a problem caused by the ripple generated when the motor drive circuit 60 of the brushless motor 1 according to the first to fourth embodiments is driven by the direct PWM method. FIG. 6 is a circuit diagram showing a configuration for the above, and a circuit diagram showing a modification thereof.
[0057]
As shown in FIG. 9A, in the motor drive circuit 60 of the brushless motor 1 of this embodiment, a capacitor 68 having a capacitance of 0.1 μF or more is electrically connected in parallel to the motor power supply 66. For this reason, even if a ripple is applied on the wiring from the motor power supply 66 to the drive coil 31, this ripple is released to the wiring for the ground potential M-GND via the capacitor 68. Therefore, no ripple is applied to the motor power supply 66, so that there is no problem in the operation of equipment such as video. In the direct PWM method, there is a moment when all the power transistors are all turned off at the same time. In such a case, the regenerative current tries to return to the motor power supply 66, but such a pulse can also be absorbed by the capacitor 68. it can. Therefore, the motor power supply 66 can be protected, and the motor drive circuit 60 is not subjected to a voltage higher than its withstand voltage.
[0058]
As shown in FIG. 9B, in the motor drive circuit 60 of the brushless motor 1, a motor current detection resistor RS may be inserted in the middle of the wiring from the motor power supply 66 to the drive coil 31. In such a case, the ripple removing capacitor 68 described with reference to FIG. 9A is closer to the motor power supply 66 on the side closer to the motor drive circuit 60 than the motor current detection resistor RS. It is preferable to effectively remove the ripple generated on the motor drive circuit 60 side by electrically connecting in parallel.
[0059]
[Other embodiments]
In the above embodiment, the iron plate portion 41 and the stator core 32 are fixed to the ground potential M-GND. However, any fixed potential may be used, and the iron plate portion 41 and the stator core 32 may be fixed to the motor power supply VM.
[0060]
【The invention's effect】
As described above, in the direct PWM type brushless motor according to the present invention, even if the voltage applied to the wiring from the motor drive circuit to the drive coil and the voltage applied to the drive coil itself repeatedly change rapidly. Since the potential of the metal plate or the stator core constituting the metal substrate that is capacitively coupled with each of them is fixed, these motor components can prevent electromagnetic noise from diffusing.
[Brief description of the drawings]
FIG. 1 is a side view of a direct PWM brushless motor to which the present invention is applied, with a part thereof cut away.
FIGS. 2A and 2B are explanatory diagrams showing a state in which power is supplied from a motor power supply to a drive coil in the motor drive circuit of the brushless motor shown in FIG. It is explanatory drawing which shows a mode that a regenerative current flows with the counter electromotive force which generate | occur | produced in the drive coil when the electric power supply to a coil was stopped.
3 is a waveform showing a voltage waveform and a current waveform applied to a driving coil for one phase when the control shown in FIGS. 2A and 2B is performed in the brushless motor shown in FIG. FIG.
4 is a voltage waveform in the period b shown in FIG. 3 during the period b in which a voltage is applied to the drive coil and the period c in which the voltage application to the drive coil is paused in the brushless motor shown in FIG. It is a wave form diagram which shows a current waveform.
FIG. 5 is a cross-sectional view showing a short circuit structure for an iron substrate and a stator core in the direct PWM brushless motor according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a short circuit structure with respect to an iron substrate in a direct PWM brushless motor according to a second embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a short circuit structure for an iron substrate and a stator core in a direct PWM brushless motor according to a third embodiment of the present invention.
FIG. 8 is a cross-sectional view showing a short circuit structure for an iron substrate and a stator core and a structure for fixing a bearing holder and a chassis in a direct PWM brushless motor according to a fourth embodiment of the present invention.
FIGS. 9A and 9B each prevent a problem caused by a ripple generated when driven by a direct PWM method in a motor drive circuit of a brushless motor according to a fifth embodiment of the present invention. FIG. 6 is a circuit diagram showing a configuration for the above, and a circuit diagram showing a modification thereof.
[Explanation of symbols]
1 Brushless motor
5 Rotor
7 Magnetic sensor
10 Rotating shaft
20 Bearing
25 Bearing holder
30 Stator
31 Drive coil
32 Stator core
33 Core holder
35 Tap screw (conductive connecting member / conductive metal material)
40 Iron substrate (metal substrate)
41 Iron plate part of iron substrate
42 Insulating layer of iron substrate
43 Wiring pattern of iron substrate
47 Land of iron substrate
48 Metal screw for short circuit (conductive metal material)
55 pulley
60 Drive IC used in motor drive circuit
68 Capacitor for ripple absorption
70 Sensor holder
71 Sensor holder of sensor holder
72 Claw for fixing sensor holder
91 Screw receiver made of conductive resin
331, 332 Insulating cylinder part of the core holder

Claims (14)

In a direct PWM type brushless motor that directly controls on / off of a switching element of a motor driving circuit and controls energization to a motor driving coil by modulating a switching pulse width for the switching element.
A rotor that rotates integrally with a rotating shaft that is rotatably supported by a bearing, a stator that includes a stator core around which a drive coil is wound, a metal substrate, and the motor drive circuit that is configured on the metal substrate. And
Causes short-circuited to the fixed potential by connecting member conductive metal plate for constituting the metal substrate,
Motor and attachment to the body side chassis mounted the metal plate and of the insulation resistance of 1kΩ or more, and a brushless motor which is characterized in that not more than 100 k.OMEGA.   2. The metal plate and the stator core according to claim 1, wherein the metal plate and the stator core are connected to each other by the connecting member and are connected to a wiring pattern connected to the fixed potential. Is connected to the fixed potential.   3. The brushless motor according to claim 2, wherein the fixed potential is either a ground potential or a power supply potential of the motor driving circuit.   3. The brushless motor according to claim 2, wherein a capacitor having a capacitance of 0.1 [mu] F or more is electrically connected in parallel with the motor power source between the motor driving circuit and the motor power source. The brushless motor according to claim 1, wherein an insulation resistance between the mounting portion and the stator core is 1 kΩ or more and 100 kΩ or less. In Claim 5, the attachment part to the body side chassis in the motor is formed by a bearing holder made of conductive resin that holds the bearing,
A brushless motor , wherein an insulation resistance between the bearing holder and the metal plate and an insulation resistance between the bearing holder and the stator core are 1 kΩ or more and 100 kΩ or less. In Claim 5, the attachment part to the body side chassis in the motor is formed of a metal bearing holder holding the bearing,
The brushless is characterized in that both the bearing holder and the metal plate and between the bearing holder and the stator core have an insulation resistance of 1 kΩ or more and 100 kΩ or less. motor. In claim 7, the bearing holder is formed with a hole embedded with a conductive resin screw receiver,
The brushless motor is characterized in that a screw for fixing the bearing holder and the chassis on the main body side is fixed to the screw receiver. In a direct PWM type brushless motor that directly controls on / off of a switching element of a motor driving circuit and controls energization to a motor driving coil by modulating a switching pulse width for the switching element.
A rotor that rotates integrally with a rotating shaft that is rotatably supported by a bearing, a stator that includes a stator core around which the driving coil is wound, and a circuit board that includes a circuit pattern for energizing the driving coil. Comprising a metal substrate to be configured, and the motor drive circuit configured on the metal substrate,
Causes short-circuited to the fixed potential by a conductive metal material of the metal plate constituting the metal substrate,
The brushless motor according to claim 1, wherein an insulation resistance between the mounting portion of the motor and the attachment on the main body side chassis and the metal plate is 1 kΩ or more and 100 kΩ or less. In Claim 9, the metal plate and the stator core are electrically connected to each other by the conductive metal material, the circuit board is formed with a wiring pattern connected to the fixed potential,
A brushless motor characterized in that both the metal plate and the stator core are connected to the fixed potential by electrically connecting the metal plate and the wiring pattern.   11. The brushless motor according to claim 10, wherein the fixed potential is either a ground potential or a power supply potential of the motor driving circuit.   12. The conductive metal material according to claim 11, wherein the conductive metal material includes a first conductive metal material that electrically connects the metal plate and the stator core, and a land portion that is connected to the wiring pattern at a predetermined position of the metal plate. And a second conductive metal material for electrically connecting the metal plate and the brushless motor. The brushless motor according to claim 9, wherein an insulation resistance between the attachment portion and the stator core is 1 kΩ or more and 100 kΩ or less.   10. The brushless motor according to claim 9, wherein a capacitor having a capacitance of 0.1 μF or more is electrically connected in parallel with the motor power source between the motor driving circuit and the motor power source.

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