WO2018147256A1 - Brushless dc motor - Google Patents

Abstract

Provided is a brushless DC motor comprising: a stator; a magnet rotor; a position detection unit for detecting the positional relationship between the magnet rotor and windings; a speed instruction unit for outputting a voltage in accordance with the rotation speed of the magnet rotor; a motor-driver IC (16) configured so that the following are integrated, an inverter circuit (8) which includes a switching element and which is connected to the stator, a duty determination unit (10) which determines the duty of an impressed voltage imparted to the stator on the basis of a speed instruction signal from the speed instruction unit, and a drive control unit (11) which, on the basis of the positional relationship detected by the position detection unit and the duty determined by the duty determination unit, distributionally outputs a duty signal to the switching element of the inverter circuit; and a thermosensitive resistance element (12) which lowers the voltage serving as the speed instruction signal imparted to the duty determination unit (10) from the speed instruction unit, such lowering carried out by detecting the temperature of a solder connection section (23) of the motor driver IC (16) and then increasing resistance in accordance with a rise in temperature.

Description

Brushless DC motor

The present invention relates to a brushless DC motor, for example, a brushless DC motor used for a ventilation fan such as a ventilation fan, a range hood, or an air purifier.

In recent years, since brushless DC motors are efficient, save power, and have excellent durability, for example, they are increasingly installed in ventilation fans such as ventilation fans, range hoods, and air purifiers. In such a brushless DC motor, when an abnormal state such as a lock or overload occurs, the temperature rises abnormally, causing a dielectric breakdown or defective insulation in the winding, and in the worst case, there is a possibility of firing. Therefore, the brushless DC motor has a function of detecting an abnormality when an abnormality occurs and suppressing a temperature rise of the winding or the like.

Conventionally, as an example of this type of brushless DC motor, those shown in FIGS. 7 and 8 are known.

Hereinafter, the configuration will be described with reference to FIGS.

FIG. 7 is a block diagram showing functions of a conventional brushless DC motor. As shown in FIG. 7, the windings U, V, and W of the brushless DC motor 101 are connected to a plurality of switching elements 102 that supply driving signals Vu, Vv, and Vw of the windings U, V, and W, respectively. The plurality of switching elements 102 are provided with transistors Q1, Q2, Q3, Q4, Q5, and Q6, and diodes are connected in parallel to the transistors Q1 to Q6. Driving signals Vu, Vv, and Vw for the windings U, V, and W are output from connection points of the transistors Q1 and Q4, the transistors Q2 and Q5, and the transistors Q3 and Q6, respectively.

The collectors of the transistors Q1 to Q3 are connected to the positive electrode of the DC power supply 103, and the emitters of the transistors Q4 to Q6 are connected to the negative electrode of the DC power supply 103.

The position detecting means 104 is connected to the switching element on / off signal generating means 105. The switching element on / off signal generating means 105 is connected to drive means 106 for outputting a control signal for turning on / off the transistors Q1 to Q6 of the plurality of switching elements 102. A signal output from the switching element on / off signal generating means 105 is input to the drive means 106.

Further, the speed indicating means 107 and the overcurrent detecting means 108 are connected to the switching element on / off signal generating means 105.

The speed instruction means 107 compares the rotational speed command signal 109 for determining the rotational speed of the brushless DC motor 101 with the triangular wave from the triangular wave generating circuit by a comparator. Then, the speed instruction unit 107 drives the brushless DC motor 101 by outputting to the switching element on / off signal generating unit 105 the on-duty duty of the transistors Q1 to Q6 corresponding to a predetermined rotational speed. A motor current having the same magnitude as the current flowing through the windings U, V, and W of the brushless DC motor 101 flows through the current detection resistor 110 via the plurality of switching elements 102.

FIG. 8 shows a block diagram of the overcurrent detection means 108.

The overcurrent detection means 108 compares the voltage generated when the motor current flowing through the windings U, V, and W flows through the current detection resistor 110 with the reference voltage 111 by the comparator 112. The comparator 112 outputs a signal for turning off the transistors Q1 to Q6 to the switching element on / off signal generating means 105 when the voltage generated in the current detection resistor 110 is larger than Vref which is the reference voltage 111. The switching element on / off signal generation means 105 receives the signal input from the comparator 112 and turns off the transistors Q1 to Q6 via the drive means 106.

Further, the temperature sensing resistor element 113 whose resistance value increases as the temperature increases, the common power source 114 of the drive circuit, and the voltage dividing resistor 115 having a resistance value R1 sufficiently larger than that of the temperature sensing resistor element at the normal temperature include a current detection resistor. 110 and the comparator 112 are connected. When the voltage of the common power supply 114 is E and the resistance value of the temperature-sensitive resistance element 113 when a certain temperature is reached is Rt, the voltage V0 input to the comparator 112 is a voltage generated by the current limiting resistor 110. V0 = E * Rt / (Rt + R1) is added. That is, the switching element on / off generating means 105 increases the signal for turning off the transistors Q1 to Q6, thereby reducing the current flowing through the brushless DC motor 101 and suppressing the temperature rise of the windings U, V, W. Yes.

Japanese Patent Laid-Open No. 10-201280

In such a conventional configuration, the temperature detected by the temperature-sensitive resistance element is likely to vary depending on use conditions and design requirements. Moreover, it is the structure which suppresses the temperature rise of a motor by determining temperature using components, such as a semiconductor, in addition to a temperature sensitive resistive element. For this reason, there is a problem that reliability is reduced due to an increase in circuit parts, and that cost reduction and size reduction cannot be achieved.

Therefore, the present invention solves the above-described conventional problems, and an object of the present invention is to provide a small brushless DC motor that is highly reliable, low in cost, and has no special temperature determination means.

In order to achieve this object, a brushless DC motor according to the present invention includes a stator having three-phase windings, a magnet rotor that rotates by supplying power to the stator, a magnet rotor, A position detection unit that detects a positional relationship with the winding, a speed instruction unit that outputs a voltage corresponding to the rotation speed of the magnet rotor as a speed instruction signal, and a plurality of switching elements, which are connected to the stator. An inverter circuit, a duty determining unit that determines a duty of an applied voltage to be applied to the stator based on a speed instruction signal from the speed indicating unit, a positional relationship detected by the position detecting unit, and a duty determined by the duty determining unit A motor driver IC configured integrally with a drive control unit that distributes and outputs a duty signal to a plurality of switching elements included in the inverter circuit, and a motor driver I The voltage as a speed instruction signal given from the speed instruction section to the duty determination section is reduced by detecting the temperature of the solder connection section, which is a connection terminal for connecting to the substrate, and increasing the resistance in response to the temperature rise. And a temperature sensitive resistance element.

According to the present invention, it is possible to obtain an effect of realizing a highly reliable, low-cost and small brushless DC motor without any special temperature determination means.

FIG. 1A is a side view of a ventilation blower equipped with a brushless DC motor according to the present invention. FIG. 1B is a bottom view of a ventilation blower equipped with a brushless DC motor according to the present invention. FIG. 1C is a front view of a ventilation blower equipped with a brushless DC motor according to the present invention. FIG. 2 is a block diagram showing functions of the brushless DC motor according to the present invention. FIG. 3 is a connection diagram of the motor driver IC and the temperature sensitive resistance element according to the present invention. FIG. 4 is a connection diagram of the motor driver IC and the temperature sensitive resistance element through the through hole according to the present invention. FIG. 5 is a cross-sectional view of a brushless DC motor according to the present invention. FIG. 6 is a characteristic graph of the temperature-sensitive resistance element according to the present invention. FIG. 7 is a block diagram showing functions of a conventional brushless DC motor. FIG. 8 is a schematic circuit diagram of conventional overcurrent detection means.

The brushless DC motor according to the present invention includes a stator provided with three-phase windings, a magnet rotor that rotates when power is supplied to the stator, and a position that detects a positional relationship between the magnet rotor and the windings. A detection unit, a speed instruction unit that outputs a voltage corresponding to the rotation speed of the magnet rotor as a speed instruction signal, an inverter circuit having a plurality of switching elements and connected to the stator, and a speed from the speed instruction unit A plurality of switching elements included in the inverter circuit based on the duty determination unit that determines the duty of the applied voltage to be applied to the stator based on the instruction signal, the positional relationship detected by the position detection unit, and the duty determined by the duty determination unit; A motor driver IC configured integrally with a drive control unit that distributes and outputs a duty signal, and a connection terminal for connecting the motor driver IC to the substrate And a temperature sensitive resistor element to reduce the voltage as the speed instruction signal applied to the duty determination unit from the velocity instruction part by increasing the resistance in response to an increase in temperature by detecting the temperature of a solder connection.

Thereby, the temperature-sensitive resistance element detects the temperature rise of the motor driver IC through the connection terminal for connecting the motor driver IC to the substrate, and increases the resistance value. As a result, the voltage as the speed instruction signal is reduced, and the duty of the voltage applied to the stator winding is suppressed. For this reason, the temperature rise of the stator winding can be suppressed without special temperature determination means. Therefore, there is an effect that a small brushless DC motor with high reliability and low cost is realized.

Further, the temperature sensitive resistance element may be connected to and close to the solder connection portion.

By connecting the temperature sensitive resistance element to the connection terminal for connecting the motor driver IC to the substrate and bringing it close to the board, the temperature rise of the motor driver IC is detected more accurately through the connection terminal, and further reliability is improved. Can be increased.

Further, the temperature-sensitive resistance element may be connected in series on a connection connecting the speed instruction unit and the duty determination unit.

By connecting in series on the connection, the temperature can be detected without using components or semiconductors other than the temperature sensitive resistance element, and the reliability can be further improved.

In addition, the temperature-sensitive resistance element is arranged on the back surface of the surface on which the motor driver IC is disposed, and is connected to the solder connection portion through a through hole provided in the substrate in the vicinity of the solder connection portion of the motor driver IC. May be.

This makes it possible to accurately detect the temperature even when a temperature-sensitive resistance element is connected to the back surface while effectively using the back surface.

Also, the temperature sensitive resistance element may be a surface mount component.

Since the temperature-sensitive resistance element used as a surface-mounted component is small, it can be easily placed close to the solder connection part of the motor driver IC, contributing to the miniaturization of the board.

Further, the distance between the solder connection part, which is a connection terminal for connecting the temperature-sensitive resistance element to the substrate, and the solder connection part, which is a connection terminal for connecting the motor driver IC to the board, is in the range of 0.1 mm to 5 mm. It is good.

As a result, the temperature of the motor driver IC is increased by connecting the temperature sensitive resistance element to the connection terminal for connecting the motor driver IC to the substrate and bringing the temperature sensitive resistance element close within a range of 0.1 mm to 5 mm. Can be detected accurately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention. In addition, throughout the drawings, the same portions are denoted by the same reference numerals, and the second and subsequent descriptions are omitted. Furthermore, in each drawing, the description of the details of each part not directly related to the present invention is omitted.

(Embodiment)
FIG. 1A is a side view of a ventilation blower equipped with a brushless DC motor according to the present embodiment. FIG. 1B is a bottom view of the ventilation blower equipped with the brushless DC motor according to the present embodiment. FIG. 1C is a front view of a ventilation blower equipped with a brushless DC motor according to the present embodiment.

As shown in FIG. 1A, FIG. 1B, and FIG. 1C, the ventilation blower includes a casing 1, a brushless DC motor 2, a blower fan 3, and an external circuit 4. The ventilation blower has a structure in which a brushless DC motor 2 is attached to a casing 1, a blower fan 3 is attached to the brushless DC motor 2, and an external circuit 4 is attached to the top surface of the casing 1. This ventilation blower is attached to the ceiling, and the centrifugal blower fan 3 is rotated based on the control by the external circuit 4 so that indoor air is taken in and exhausted outside to ventilate the room.

Next, the configuration of the brushless DC motor will be described with reference to FIG. FIG. 2 is a block diagram showing functions of the brushless DC motor according to the present embodiment.

The brushless DC motor 2 includes a stator 5, a magnet rotor 6, a position detection unit 7, an inverter circuit 8, a speed instruction unit 9, a duty determination unit 10, a drive control unit 11, a temperature sensitive resistance element. 12. The brushless DC motor 2 is connected to an AC power supply 15 via a rectifying unit 13 and a smoothing capacitor 14. The motor driver IC 16 is obtained by integrating the inverter circuit 8, the drive control unit 11, and the duty determination unit 10 into one package.

The stator 5 has a hollow cylindrical shape whose outer periphery is covered with a plurality of teeth. Three-phase windings U, V, and W are wound around each tooth portion through a resin-molded insulator. The stator 5 generates a magnetic field by energizing the three-phase windings U, V, and W.

The magnet rotor 6 is provided with the inner periphery of the stator 5 and the outer periphery of the magnet rotor 6 facing each other. The magnet rotor 6 is rotationally driven by being affected by the magnetic field generated by the stator 5. That is, the magnet rotor 6 is rotated by supplying electric power to the windings U, V, and W wound around the stator 5.

The position detector 7 is composed of, for example, a Hall element or a Hall IC. The position detector 7 detects the positional relationship between the magnet rotor 6 and the stator 5 by detecting the switching of the N pole / S pole of the magnet rotor 6. In other words, the position detector 7 detects the positional relationship between the magnet rotor 6 and the windings U, V, and W wound around the stator 5. Here, the positional relationship is indicated by, for example, how many angles the reference position of the magnet rotor 6 has with respect to the reference position of the stator 5.

The AC power supply 15 is, for example, a 100V AC power supply.

The rectification unit 13 is constituted by a full-wave rectification diode bridge, and full-wave rectifies the AC power supply 15 to convert it into a DC voltage including a ripple of the power supply frequency.

The smoothing capacitor 14 smoothes the voltage converted into a direct current by the rectifying unit 13 and smoothes the AC power supply 100V into a DC power supply of about 140V. The rectified and smoothed DC power supply of about 140 V is input to the inverter circuit 8.

The inverter circuit 8 has a three-phase bridge structure, and the switching elements Q1, Q2, and Q3 constituting the three-phase bridge constitute upper arm switching elements of the windings U, V, and W, respectively. Similarly, the switching elements Q4, Q5, Q6 constitute lower arm switching elements of the windings U, V, W, respectively. As shown in FIG. 2, the connection points of the switching element Q1 and the switching element Q4, the switching element Q2 and the switching element Q5, the switching element Q3 and the switching element Q6, and the windings U, V, and W are connected.

The speed instruction unit 9 instructs the rotation speed of the magnet rotor 6. For example, the speed instruction unit 9 determines the rotation speed of the magnet rotor 6 based on the rotation speed determined by an external switch or the like, and outputs a voltage corresponding to the determined rotation speed to the duty determination unit 10 as a speed instruction signal. To do.

The duty determination unit 10 includes a triangular wave generation circuit (not shown) and a comparator (not shown). The duty determination unit 10 determines the duty by comparing a voltage as a speed instruction signal input from the speed instruction unit 9 with a triangular wave using a comparator. The determined duty is output to the drive control unit 11.

The drive control unit 11 generates ON / OFF output patterns of the switching elements Q1 to Q6 of the inverter circuit 8 from the position signal input from the position detection unit 7. At the same time, the duty is input from the duty determination unit 10 to the drive control unit 11. The drive control unit 11 combines the output pattern input from the position detection unit 7 and the duty input from the duty determination unit 10 and distributes and outputs the duty signal to the inverter circuit 8.

The inverter circuit 8 applies a PWM waveform voltage of a DC power supply having a peak value of approximately 140 V to the windings U, V, and W of the stator 5 based on the duty signal input from the drive control unit 11, and magnets The rotor 6 is rotated.

The temperature sensitive resistance element 12 is provided in series on the connection connecting the speed instruction unit 9 and the duty determination unit 10. In the present embodiment, since the duty determination unit 10 is included in the motor driver IC 16, the temperature-sensitive resistance element 12 is provided in series on the connection connecting the speed instruction unit 9 and the motor driver IC. It can be said that.

FIG. 3 is a connection diagram of the motor driver IC and the temperature sensitive resistance element according to the present embodiment. As shown in FIG. 3, the motor driver IC 16 and the temperature sensitive resistance element 12 are mounted on the printed circuit board 17.

The motor driver IC 16 has a die pad 18 on which the inverter circuit 8, the drive control unit 11, and the duty determination unit 10 are mounted. These are electrically connected on the die pad 18.

The die pad 18 is electrically connected to the lead 20 via the bonding wire 19 and is also thermally connected. Further, the outer package (package) of the motor driver IC 16 is formed by filling the resin 21. Components such as the internal die pad 18 are fixed by a resin 21.

The motor driver IC 16 and the temperature-sensitive resistance element 12 are solder-connected to the printed circuit board 17 at the solder connection portion 23 on the copper foil pattern 22. The solder connection portion 23 is provided on the copper foil pattern 22 and is a connection terminal for connecting electronic components such as the motor driver IC 16 and the temperature sensitive resistance element 12 to the printed circuit board 17. Since the solder connection part 23 of the motor driver IC 16 and the solder connection part 23 of the temperature-sensitive resistance element 12 are close to each other and the copper foil pattern 22 has high thermal conductivity, the motor driver IC 16 and the temperature-sensitive resistance element 12 are mutually connected. Heat is easily transmitted. That is, when the temperature of the motor driver IC 16 rises, the heat of the motor driver IC 16 is efficiently transmitted to the temperature sensitive resistance element 12. Thereby, the temperature sensitive resistance element 12 detects the temperature of the motor driver IC 16. Further, as described above, the solder connection portion 23 of the temperature-sensitive resistance element 12 and the solder connection portion 23 of the motor driver IC 16 are close to each other. That is, it can be said that the temperature-sensitive resistance element 12 detects the temperature of the solder connection portion 23 that is a connection terminal for connecting the motor driver IC 16 to the printed circuit board 17. Here, the solder connection portion 23 of the motor driver IC 16 and the solder connection portion 23 of the temperature-sensitive resistance element 12 may be separated by a resist 24 that is an insulating film that electrically insulates each solder connection portion 23. Even if the solder connection portions 23 are integrated with each other without the resist 24, the functions are equivalent, but it is desirable to provide the resist 24 because solder mounting can be performed with high quality. Here, the distance between the solder connection portion 23 of the motor driver IC 16 and the solder connection portion 23 of the temperature-sensitive resistance element 12 is preferably 0.1 mm or more in order to perform solder mounting with high quality as described above. In order to detect the heat generation of the motor driver IC 16 with higher accuracy, it is preferable to set it to 5 mm or less.

Further, the temperature-sensitive resistance element 12 is a surface-mounted component, and since it is small, heat is easily transmitted, and since the surface area is small, self-heat dissipation is also small, and heat generation of the motor driver IC 16 is detected more accurately.

FIG. 4 is a connection diagram when the motor driver IC and the temperature-sensitive resistance element are connected through a through hole. As shown in FIG. 4, when the temperature-sensitive resistance element 12 is provided on a surface different from the connection surface of the motor driver IC 16, that is, on the back surface of the printed board, the connection is made as shown in FIG.

The through hole 25 electrically and thermally connects the solder connection portion 23 of the motor driver IC 16 and the solder connection portion 23 of the temperature-sensitive resistance element 12 disposed on the back surface of the printed circuit board 17 on which the motor driver IC 16 is disposed. It is a through-hole connected to. The surface of the through hole 25 is made of gold plating or the like, and is connected to the copper foil pattern 22 on the front surface and the back surface of the printed board 17.

FIG. 5 is a cross-sectional view of the brushless DC motor 2 according to the present embodiment. As shown in FIG. 5, a winding 26 is provided on the stator 5. The magnet rotor 6 includes a permanent magnet 27 and a ball bearing 28. Further, the connector 29, which is an interface between the motor driver IC 16 and the external circuit 4 (not shown in FIG. 5), the position detection unit 7 (not shown in FIG. 5), and the temperature sensitive resistance element 12 are the printed circuit board 17. And are electrically connected to each other. Further, the winding 26 of the stator 5 is electrically connected on the printed circuit board 17 (not shown in FIG. 5), and the stator 5 and the winding 26 are BMC (Bulk Molding Compound) as a resin. ) 30 to form a part of the outline of the brushless DC motor 2. Further, the magnet rotor 6 is held by a stator 5 and a bracket 31 integrated with the outer shell. An insulating film 32 is disposed between the bracket 31 and the printed circuit board 17 to ensure insulation between the bracket 31 that is the outline of the brushless DC motor 2 and the printed circuit board 17. Furthermore, the temperature-sensitive resistance element 12 is close to the motor driver IC 16 and accurately detects the temperature rise of the motor driver IC 16.

FIG. 6 is a diagram showing the characteristics of the temperature-sensitive resistance element according to the present embodiment. In the present embodiment, a PTC (Positive Temperature Coefficient Thermistor, a positive temperature coefficient thermistor) is used as the temperature sensitive resistance element 12. In FIG. 6, the vertical axis indicates the resistance value change ratio of the temperature-sensitive resistance element 12 with 25 ° C. as a reference, and the horizontal axis indicates the temperature of the temperature-sensitive resistance element 12. PTC has a resistance value that is substantially constant from room temperature (25 ° C.) to a certain temperature, but has a property that the resistance value rapidly increases when a certain temperature is exceeded. For example, in the case of the characteristic C, when the resistance value at 25 ° C. is 1000Ω, the resistance value rapidly increases from around the temperature of 80 ° C., and at about 130 ° C., the resistance value is about 400 times, that is, about 400 kΩ. .

Here, the operation when abnormality such as rotation abnormality or lock occurs in the brushless DC motor 2 will be described.

The upper limit value of the temperature of the winding 26 is determined by the dielectric breakdown temperature or standard of the film of the winding 26, and is 150 ° C., for example, in the present embodiment. At this time, similarly to the winding 26, the motor driver IC 16 also generates heat and rises in temperature.

In the motor driver IC 16, the inverter circuit 8 generates the most heat, but as shown in FIGS. 3 and 4, the heat is well transmitted to the lead 20 by the die pad 18, the bonding wire 19, and the filled resin 21. Since the lead 20 has a lower thermal resistance than the resin 21, the lead 20 has good thermal conductivity. The motor driver IC 16 and the temperature sensitive resistance element 12 are connected in close proximity via the lead 20, the copper foil pattern 22 of the printed circuit board 17, and the solder connection portion 23. Since the lead 20, the copper foil pattern 22, and the solder connection portion 23 are made of metal or an alloy thereof, the heat sensitive resistance element 12 can accurately detect the temperature of the motor driver IC 16 because the heat propagates well.

The voltage as a speed instruction signal output from the speed instruction unit 9 when rotation abnormality or lock occurs is likely to be the highest when the duty determined by the duty determination unit 10 is Max. Is a high condition. In the present embodiment, for example, the duty max = 5.8V and the output of the speed instruction unit 9 is Vo = 6V. Further, the voltage at which the duty becomes Min is assumed to be the duty min = 2.0V.

The duty determination unit 10 inputs a voltage as a speed instruction signal to the comparator as described above. Since the input impedance of the comparator is high, the current Iin flowing through the input portion of the speed instruction signal of the comparator is small, about 25 μA.

Assuming that the resistance value of the temperature-sensitive resistance element 12 in a certain state is the resistance value Rth and the voltage as the speed instruction signal input to the duty determining unit 10 is the voltage Vin, the voltage Vin can be expressed by the following equation.

Vin = Vo−Iin × Rth (Formula 1)
Here, when the brushless DC motor 2 mounted with the temperature sensitive resistance element 12 having the characteristic C is in the locked state with the output Vo = 6V of the speed instruction unit 9, two of the three phases are used in the three-phase full-wave drive. Energization is fixed to the phase. For example, a current is passed from the winding U to W. The temperature of the windings U and W rises because the lock current continues to flow. The winding V that is not energized also rises at a lower temperature than the windings U and W in response to the temperature fluctuations of the windings U and W.

At this time, since the current of the motor driver IC 16 is the same as the current flowing from the winding U to the winding W, the temperature rises in a state approximately proportional to the temperature rise of the windings U and W.

Here, for example, when the temperature of the windings U and W that are the windings 26 is 130 ° C., the package temperature of the motor driver IC 16 is 135 ° C., and the temperature of the temperature sensitive resistance element 12 is 127 ° C. Further, the temperature-sensitive resistance element 12 has a resistance value 200 times, that is, 200 kΩ, and from Equation 1, Vin = 6V−25 μA × 200 kΩ
And
Vin = 1V
Therefore, it is smaller than the duty Min voltage of 2.0 V, the duty is 0%, that is, the drive is turned off.

Then, the temperature of the winding 26 and the motor driver IC 16 is lowered, and the current is limited so as not to exceed the upper temperature limit 150 ° C. of the winding 26.

That is, the temperature-sensitive resistance element 12 functions so as to decrease the determined value of the duty determining unit 10 with respect to the temperature increase of the motor driver IC 16 having a correlation with the temperature increase of the winding 26. Further, the increase of the resistance according to the temperature rise at the time of abnormal rotation of the temperature sensitive resistance element 12 is determined by the predetermined value of the duty determined by the duty determining unit 10 and the temperature increase range of the winding 26 at the time of abnormal rotation. It will be lowered below the range temperature.

Thereby, the temperature rise of the winding 26 can be suppressed.

As described above, by measuring the temperature rise of the motor driver IC 16, the temperature rise of the winding 26 can be increased by selecting the characteristics of the temperature sensitive resistance element 12 in a range not exceeding the upper limit of the temperature of the winding 26 in advance. Can be limited. Further, as shown in FIG. 5, the temperature-sensitive resistance element 12 increases the temperature of the motor driver IC 16 without measuring the temperature of the winding 26 via the air layer between the BMC 30 and the printed circuit board 17. By detecting with high accuracy, the temperature rise of the winding 26 can be limited.

In the present embodiment, an example in which the duty determined by the duty determining unit 10 is 0% is shown, but the present invention is not limited to this. Actually, the temperature rise is suppressed while the duty is output within a range not exceeding the upper limit of the temperature of the winding 26 due to the thermal resistance of the brushless DC motor 2 itself, the ambient temperature, etc. In many cases.

Although it has been described that the drive method is three-phase full-wave drive and energized in two phases, three-phase energization may be used as a sine wave energization, and there is no difference in the operational effect depending on the drive method. Furthermore, although the voltage applied to the inverter circuit 8 is a DC voltage of approximately 140 V obtained by full-wave rectification from the AC power supply 15, a low voltage such as DC 24 V or 42 V may be used. Furthermore, the inverter circuit 8, the drive control unit 11, and the duty determination unit 10 of the motor driver IC 16 may have a one-chip structure configured on the same chip, and there is no difference in operation and effect. Further, in FIG. 5, the configuration in which the stator 5 is covered with the BMC is described. However, there is no difference in operational effect depending on the type of resin as long as the stator 5 can be held with insulation performance and heat resistance.

Since the brushless DC motor according to the present invention can suppress the temperature rise of the stator winding without any special temperature determination means, the reliability is high, and the cost and size can be reduced. Therefore, it is useful as a brushless DC motor used in a ventilation blower, for example, a ventilation blower such as a ventilation fan, a range hood, or an air purifier.

DESCRIPTION OF SYMBOLS 1 Casing 2,101 Brushless DC motor 3 Blower fan 4 External circuit 5 Stator 6 Magnet rotor 7 Position detection part 8 Inverter circuit 9 Speed instruction | indication part 10 Duty determination part 11 Drive control part 12,113 Temperature sensitive resistance element 13 Rectification part 14 Smoothing capacitor 15 AC power supply 16 Motor driver IC
17 Printed Circuit Board 18 Die Pad 19 Bonding Wire 20 Lead 21 Resin 22 Copper Foil Pattern 23 Solder Connection 24 Resist 25 Through Hole 26, U, V, W Winding 27 Permanent Magnet 28 Ball Bearing 29 Connector 30 BMC
31 Bracket 32 Insulating film

Claims (6)

A stator with three-phase windings;
A magnet rotor that rotates by supplying power to the stator;
A position detector for detecting a positional relationship between the magnet rotor and the winding;
A speed instruction unit that outputs a voltage corresponding to the rotational speed of the magnet rotor as a speed instruction signal;
An inverter circuit having a plurality of switching elements, connected to the stator, a duty determination unit for determining a duty of an applied voltage to the stator based on the speed instruction signal from the speed instruction unit; A drive control unit that distributes and outputs a duty signal to the plurality of switching elements of the inverter circuit based on the positional relationship detected by the position detection unit and the duty determined by the duty determination unit is integrated. Motor driver IC,
The temperature given from the speed instruction unit to the duty determination unit by detecting the temperature of the solder connection part, which is a connection terminal for connecting the motor driver IC to the substrate, and increasing the resistance according to the rise in temperature. A brushless DC motor comprising: a temperature-sensitive resistance element that reduces the voltage as a speed instruction signal. The temperature sensitive resistance element is:
The brushless DC motor according to claim 1, wherein the brushless DC motor is connected to and close to the solder connection portion. The temperature sensitive resistance element is:
The brushless DC motor according to claim 1, wherein the brushless DC motor is connected in series on a connection connecting the speed instruction unit and the duty determination unit. The temperature sensitive resistance element is:
Disposed on the back surface of the substrate on which the motor driver IC is disposed;
4. The brushless DC motor according to claim 1, wherein the brushless DC motor is connected to the solder connection portion through a through hole provided in the substrate in the vicinity of the solder connection portion of the motor driver IC. The temperature sensitive resistance element is:
The brushless DC motor according to any one of claims 1 to 4, which is a surface mount component. A distance between a solder connection portion that is a connection terminal for connecting the temperature-sensitive resistance element to the substrate and a solder connection portion that is a connection terminal for connecting the motor driver IC to the substrate is 0.1 mm or more and 5 mm. The brushless DC motor according to claim 2, which is in the following range.

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