Motor drive system

Abstract

This enables the realization of a small, lightweight, and high-output motor drive system. [Solution] This is a motor drive system 1 that boosts the voltage of a battery 2 to drive a single-phase motor 3. The motor 3 has a rotor 30 including a magnet 30a and a stator 31 including a stator core 32. It is composed of a first coil 41 concentrated on each of the teeth 32b and a second coil 42 toroidally wound on the yoke 32a. The a-phase first coil 41 is connected in series with the a-phase second coil 42, and the b-phase first coil 41 is connected in series with the b-phase second coil 42. The a-phase and b-phase first coils 41 and second coils 42 are wound in opposite directions to each other, and alternating current and direct current flow through these coils 41 and 42.

Description

[Technical Field]

[0001] The disclosed technology relates to a small, lightweight, high-output motor drive system suitable for stick-type vacuum cleaners, portable electric tools, and the like. [Background Art]

[0002] In recent years, from the perspective of improving convenience, an increasing number of electric devices have adopted a cordless configuration that does not require a cord, instead of the conventional configuration that is used with the cord connected to an outlet. For example, stick-type vacuum cleaners are popular among vacuum cleaners, and robot vacuum cleaners are also attracting attention. Cordless portable electric tools such as drills and drivers are also popular.

[0003] Regarding the disclosed technology, a stator core having coils in both concentrated winding and toroidal winding forms is disclosed in Patent Document 1. However, the object and specific configuration thereof differ from those of the disclosed technology. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. Hei 8-172759 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Cordless electric devices use a battery as a power source. In contrast, vacuum cleaners require high suction power, and electric tools require high torque. To meet these requirements, it is necessary to drive the motor at high output.

[0006] To drive a motor at high output, a high-voltage battery is required. In contrast, increasing the number of unit cells (cells) constituting the battery can achieve a higher voltage.

[0007] However, increasing the number of cells leads to problems such as higher costs, heavier weight, and larger size.

[0008] Therefore, this specification discloses a technology that enables the motor to be driven at high output without requiring a high voltage battery, thereby providing a motor drive system suitable for miniaturization and weight reduction. [Means for solving the problem]

[0009] The disclosed technology relates to a motor drive system that drives a single-phase motor by boosting the voltage of a battery through the control of a predetermined electronic circuit with a controller.

[0010] The motor includes a rotatable rotor containing magnets that constitute a plurality of magnetic poles, and a stator that includes a stator core and a plurality of coils and faces the rotor circumferentially via an air gap. The stator core has an annular yoke portion and 2N (N is a natural number) teeth portions that project radially from the yoke portion toward the rotor.

[0011] The coil is composed of a first coil consisting of a phase and b phase arranged alternately in the circumferential direction by concentrated winding on each of the teeth portions, and a second coil consisting of a phase and b phase arranged alternately in the circumferential direction by toroidal winding on each of the portions between two circumferentially adjacent teeth portions in the yoke portion. The a phase first coil is connected in series with the a phase second coil to form an a phase coil row, and the b phase first coil is connected in series with the b phase second coil to form a b phase coil row. The a phase and b phase first and second coils are wound in opposite directions to each other.

[0012] Then, alternating current and direct current flow through the first coil and the second coil, respectively.

[0013] In other words, in this motor drive system, the stator core constituting the single-phase motor has, for each of the a-phase and b-phase, a first coil concentrated on the teeth and a second coil toroidally wound on the yoke, which are alternately formed in the circumferential direction. These first and second coils of each phase are connected in series, and the first and second coils of the circumferentially adjacent a-phase and b-phase are wound in opposite directions.

[0014] As a result, when alternating current is passed through these coil arrays of each phase, a rotating magnetic field can be formed, causing the rotor to rotate. At this time, the magnetic flux generated by the second coil of each phase, which is toroidally wound in the yoke, alternates between flowing towards the teeth located in between and drawing the magnetic flux away from the teeth, thus similarly forming a rotating magnetic field.

[0015] In contrast, when a DC current is passed through the coil arrays of each phase, the second coils of each phase become summation-driven, and the direction of the generated magnetic flux becomes the same. A DC magnetic flux that passes through in the circumferential direction is formed. As a result, the second coil can function as a boost inductance, making it possible to boost the battery voltage. The magnetic flux generated by the DC current flowing through the first coil is then canceled out.

[0016] Therefore, with this motor drive system, the motor can be driven by boosting the battery voltage while the first and second coils share a single stator yoke. The motor can be driven with high output without requiring a high battery voltage. This enables the realization of a motor drive system suitable for miniaturization and weight reduction.

[0017] As described above, when a DC current flows through these coils, a DC magnetic flux is formed that passes through the yoke in the circumferential direction. As a result, the second coil functions as a boosting inductance, which can boost the battery voltage. When an AC current flows through these coils, a rotating magnetic field is formed that acts on the rotor's magnetic poles. This allows the motor to rotate. Since the motor can be driven while boosting the battery voltage, a small and lightweight configuration can be used to drive the motor at high output.

[0018] The number of magnetic poles of the rotor and the number of teeth may be equal.

[0019] Since the motor is single-phase, the number of magnetic poles in the rotor and the number of teeth in the stator can be the same. If these are the same number, a smaller motor can be obtained while still ensuring sufficient winding space.

[0020] The electronic circuit includes a positive terminal main line and a negative terminal main line, and an H-bridge circuit and a DC bus capacitor connected in parallel between the positive terminal main line and the negative terminal main line. The H-bridge circuit includes an a-phase leg and a b-phase leg, each having an upper switching element and a lower switching element arranged in series from the positive terminal main line side. With one end of the a-phase coil array and one end of the b-phase coil array connected at an intermediate point, the midpoint of the a-phase leg is connected to one end of the a-phase coil array, and the midpoint of the b-phase leg is connected to one end of the b-phase coil array. The intermediate point is configured to be connectable to the positive terminal of the battery, and the negative terminal main line is configured to be connectable to the negative terminal of the battery.

[0021] Such an electronic circuit allows for a relatively simple structure while enabling control to boost the battery voltage to drive a single-phase motor. Because the control is also simple, the electronic circuit can be integrated with a controller on a single circuit board, for example. It can also be integrated with a small motor, making it easy to miniaturize and lighten the device.

[0022] The controller may be configured to execute: sum mode control that turns both the upper switching elements of the a-phase leg and the b-phase leg and both the lower switching elements of the a-phase leg and the b-phase leg on-on or off-off during the same period; and differential mode control that turns the upper switching element of the a-phase leg and the lower switching element of the b-phase leg, and the lower switching element of the a-phase leg and the upper switching element of the b-phase leg on-on or off-off during the same period.

[0023] With sum mode control, a direct current flows through the a-phase and b-phase second coils, thereby forming a DC magnetic flux that permeates the yoke portion in the circumferential direction. Accordingly, the second coils function as boosting inductances, and can boost the voltage of the battery. With differential mode control, an alternating current flows through the a-phase and b-phase first coils, thereby forming a rotating magnetic field that acts on the magnetic poles of the rotor. Accordingly, the motor can be rotated. It has been confirmed that the second coils also contribute to the formation of the rotating magnetic field at this time. Therefore, the motor can be rotated more smoothly.

[0024] Since the motor is driven while boosting the battery voltage with simple control, high output can be achieved even with a compact and lightweight motor drive system.

[0025] At least the yoke portion of the stator core may be integrally formed over the entire circumference using a Permendur material.

[0026] With this configuration, the yoke portion has a homogeneous structure without breaks over the entire circumference and exhibits high magnetic properties, so the magnetic properties of the stator core can be optimized in a state compatible with the configuration of the motor drive system. Therefore, higher output can be achieved for the motor drive system.

[0027] The yoke portion of the stator core is constituted by an outer ring portion positioned radially outward and an inner ring portion positioned radially inward, wherein the inner ring portion is formed integrally with the tooth portions using a non-oriented electrical steel sheet, and the outer ring portion is formed using a grain-oriented electrical steel sheet such that magnetism is enhanced in the circumferential direction.

[0028] In this way, using common materials, the magnetism of the stator core can be optimized in a state that corresponds to the configuration of the motor drive system. Accordingly, higher output of the motor drive system can be achieved.

[0029] The motor drive system described above is suitable for being mounted on a vacuum cleaner or a power tool.

[0030] Since the motor can be driven at high output without increasing the battery voltage, a vacuum cleaner or the like can be reduced in size and weight while ensuring the required output. [Effects of the Invention]

[0031] According to the disclosed technology, a motor can be driven at high output without increasing the battery voltage. Accordingly, it becomes possible to provide a small, lightweight, high-output motor drive system. [Brief Description of the Drawings]

[0032] [Figure 1] It is a diagram for explaining a preferred application example of the motor drive system. [Figure 2] It is a diagram showing an application example of the motor drive system to a stick-type vacuum cleaner. [Figure 3] It is a diagram for explaining the configuration of main parts of a motor. [Figure 4A] It is a schematic diagram showing the structure of a stator core. [Figure 4B] It is a schematic diagram showing another structure of a stator core. [Figure 5] It is a simplified block diagram of the motor drive system. [Figure 6]This diagram shows the relationship between the phase voltage and the inter-phase voltage during operation. [Figure 7] These are state diagrams for differential mode control and summation mode control. [Figure 8] This is an equation relating to the motor model. [Figure 9A] This figure shows an example of the analysis results of the magnetic flux distribution of a motor. [Figure 9B] This figure shows an example of the analysis results of the magnetic flux distribution of a motor. [Figure 10] This figure shows an example of verification results obtained through electromagnetic field analysis. [Figure 11] This figure shows an example of the analysis results related to torque in electromagnetic field analysis. [Figure 12] This figure shows an example of the simulation results. [Figure 13] This is a diagram showing a modified example. [Modes for carrying out the invention]

[0033] The technologies disclosed by embodiments are described below. However, the following description is essentially illustrative.

[0034] <Suitable application examples of the disclosed technology> Figure 1 shows a preferred application example of the disclosed technology. The motor drive system 1 to which the disclosed technology is applied comprises a single-phase motor 3, a predetermined electronic circuit 5, and a controller 7, which are integrated together. The controller 7 controls the electronic circuit 5 to boost the voltage of the battery 2 and drive the motor 3.

[0035] Therefore, even with a low voltage from battery 2, motor 3 can be driven at high output. There is no need to increase the number of cells in battery 2 to achieve a higher voltage. As a result, the entire system, including battery 2, can be made lighter relative to its output. Costs can also be reduced, and the system can be made smaller.

[0036] Therefore, this motor drive system 1 is suitable for mounting on a stick-type vacuum cleaner 100, a screwdriver, a drill, or other portable power tool 200 (cordless small electrical appliance). The battery 2 is a known rechargeable secondary battery (DC power supply) composed of lithium-ion batteries or the like. The battery 2 is mounted separately from the motor drive system 1 in a detachable manner on the vacuum cleaner 100 and the power tool 200.

[0037] (Specific application examples of motor drive systems) Figure 2 shows an example of a motor drive system 1 applied to a stick-type vacuum cleaner 100. The motor drive system 1 is incorporated into a mini-fan 101 that generates suction force.

[0038] The mini-fan 101 is installed at one end of an exhaust chamber 102, which is fitted with a filter 102a around it. In addition to the motor drive system 1, the mini-fan 101 includes a shroud 103, an impeller 104, and the like. The inside of the shroud 103 forms an air passage.

[0039] The main part of the motor 3, which is incorporated into the mini fan 101, is housed in the motor case 105. The motor case 105 is also attached to the shroud 103 to form an airflow path. The shaft 10 of the motor 3 is rotatably supported in the motor case 105 around the rotation axis A.

[0040] The impeller 104 is housed in a shroud 103 and attached to a shaft 10 that protrudes from the front end of the motor case 105. During operation of the vacuum cleaner 100, the impeller 104 rotates at a very high speed in a constant direction together with the shaft 10. As a result, an airflow is formed in the air passage, as shown by the dashed arrow in Figure 2, and a suction force is generated on the upstream side of the mini fan 101.

[0041] An electronic circuit board 106 is installed at the rear end of the motor case 105. The controller 7 and electronic circuit 5 are mounted on this electronic circuit board 106. Details of the controller 7 and electronic circuit 5 will be described later. The electronic circuit 5 is a simple circuit made up of a small number of electronic components.

[0042] Therefore, the controller 7 and electronic circuit 5 can be constructed on a simple electronic circuit board 106 and integrated with the motor 3. The motor drive system 1 can be made inexpensive, lightweight, and compact.

[0043] (motor) Figure 3 illustrates the structure of the main parts of the motor 3. Figure 3 is a schematic cross-sectional view of the motor 3 as seen from the axial direction from which the rotating shaft A extends. In Figure 3, the rotor 30 and stator 31 are shown in a simplified manner. For the purposes of this explanation, the direction around the rotating shaft A is also referred to as the circumferential direction, and the direction of the radius or diameter centered on the rotating shaft A is also referred to as the radial direction.

[0044] The rotor 30 is formed in a cylindrical shape by a magnet 30a. The rotor 30 is magnetized with alternating north and south poles at equal intervals in the circumferential direction, and in this embodiment, eight magnetic poles are formed. The shaft 10 is fixed coaxially inside the rotor 30. Therefore, the rotor 30 rotates integrally with the shaft 10.

[0045] The stator 31 includes a stator core 32 and several coils 41, 42, and is located radially outward of the rotor 30. The stator 31 is mounted to the motor case 105 and faces the rotor 30 circumferentially via an air gap.

[0046] The stator core 32 consists of a substantially cylindrical member, and when viewed from the axial direction, it has an annular yoke portion 32a and eight teeth portions 32b that project radially from the inside of the yoke portion 32a toward the rotor 30 at equal intervals in the circumferential direction. Since the motor 3 is single-phase, the number of teeth portions 32b can be 2N (where N is a natural number), that is, an even number.

[0047] In this embodiment, there are eight teeth 32b on which the first coil 41, described later, is formed, corresponding to the rotor 30 which has eight magnetic poles. In other words, the number of teeth 32b (first coil 41) corresponding to the number of magnetic poles of the rotor 30 and the number of poles of the stator 31 are the same. Since the motor 3 is single-phase, by making these the same number, it is possible to obtain a miniaturized motor while securing winding space.

[0048] Each tooth portion 32b is provided with a protruding portion 32c that is biased to one side in the circumferential direction. As a result, the rotor 30 rotates only in either a clockwise or counterclockwise direction (counterclockwise in the illustrated example). Torque ripple can also be suppressed.

[0049] Furthermore, this motor 3 is extremely small. For example, the diameter Ds of the stator core 32 shown in Figure 3 is about 3 cm. Despite this, it has the performance to rotate at ultra-high speeds of over 100,000 r / min with an output of approximately 500 W.

[0050] The stator core 32 is generally formed by stacking magnetic steel plates in the axial direction. In that case, considering the difficulty of the coil formation process, the stator core is often constructed by connecting multiple segmented cores that are divided into an arc shape. In contrast, in the case of this motor 3, as shown in Figure 4A, each steel plate 33 is made from a single steel plate that has been press-formed into the ring shape of the stator core 32 (the yoke portion 32a is formed integrally around its entire circumference).

[0051] The stator core 32 may be a block of steel material rather than a laminate of steel plates 33. Furthermore, it is preferable to use Permendur material for the steel material. Permendur material is a known soft magnetic material with excellent magnetic properties. Therefore, the stator core 32 can increase the output of the motor 3 on its own.

[0052] Even without using Permendur material, the magnetism of the stator core 32 can be increased using general electrical steel sheets to accommodate this motor drive system 1.

[0053] Specifically, as shown in Figure 4B, the yoke portion 32a is composed of an outer ring portion 34a located radially outward and an inner ring portion 34b located radially inward. The inner ring portion 34b is constructed by laminating steel plates 33 that are press-formed to the shape of the inside of the stator core 32 and are integrated with the teeth portion 32b, similar to the stator core 32 described above. It may also be constructed by connecting segmented cores. However, the steel plates 33 are made of general non-oriented electrical steel.

[0054] On the other hand, the outer ring portion 34a is constructed by wrapping a strip-shaped steel plate 33 around the outer surface of the inner ring portion 34b so that it is in close contact with it. However, grain-oriented electrical steel is used for the steel plate 33 so that its magnetism is higher in the circumferential direction. In other words, the yoke portion 32a of this stator core 32 is configured so that magnetic flux flows easily in the circumferential direction and that its magnetism is superior in the circumferential direction.

[0055] In addition, the surface of the stator core 32 is generally covered with an insulating insulator, except for the tip portion of the teeth 32b. The coil is mounted on the stator core 32 via this insulator.

[0056] The coils of this motor 3 have two types of coils 41 and 42 with different winding methods. Specifically, there is a first coil 41 formed by concentrating the winding of an electrical conductor such as a wire (hereinafter also simply referred to as a wire) on each of the teeth 32b, and a second coil 42 formed by toroidally winding a wire on each of the parts between two circumferentially adjacent teeth 32b, 32b in the yoke 32a (the so-called parts facing the slots).

[0057] The first coil 41 has an a-phase and a b-phase, which are arranged alternately in the circumferential direction (in the figure, the first coil of the a-phase is shown as C1a and the first coil of the b-phase is shown as C1b). In this embodiment, there are four first coils 41 of the a-phase and four first coils 41 of the b-phase.

[0058] The second coil 42 also has a phase a and a phase b, which are arranged alternately in the circumferential direction (in the figure, the second coil of phase a is shown as C2a and the second coil of phase b is shown as C2b). In this embodiment, there are four second coils 42 of phase a and four second coils 42 of phase b.

[0059] Each of these a-phase and b-phase coils (first coil 41 and second coil 42) is configured to be connected in a single row. Specifically, as shown in the lower part of Figure 3, the a-phase first coil 41 is alternately connected in series with the a-phase second coil 42 to form the a-phase coil row 45a. The b-phase first coil 41 is alternately connected in series with the b-phase second coil 42 to form the b-phase coil row 45b. Alternatively, a group of second coils 42 connected in series and a group of first coils 41 connected in series may be connected in series as well.

[0060] As shown in Figure 3, the first coil 41 and the second coil 42 of phases a and b, which are adjacent to each other in the circumferential direction, are constructed by winding them in opposite directions.

[0061] For example, when viewed from the direction shown in Figure 3 (where the rotor 30 rotates counterclockwise), the first coil 41 (C1a) of phase a is wound such that the wire enters the slot located behind the tooth portion 32b in the direction of rotation so as to face the plane of the paper, and exits the plane of the paper in the slot located in front of the tooth portion 32b in the direction of rotation.

[0062] In contrast, the first coil 41 (C1b) of phase b is wound such that the wire enters toward the plane of the paper in the slot located in front of the teeth portion 32b in the rotational direction, and exits from the plane of the paper in the slot located behind the teeth portion 32b in the rotational direction. In other words, the winding directions of the first coil 41 of phase a and the first coil 41 of phase b are opposite.

[0063] The same applies to the second coil 42, where the winding directions of the a-phase second coil 42 and the b-phase second coil 42 are opposite. Specifically, the a-phase second coil 42 (C2a) is wound such that the wire enters towards the plane of the paper on the radially outer side of the yoke portion 32a to be wound, and then emerges from the plane of the paper in the slot formed by the yoke portion 32a.

[0064] In contrast, the second coil 42 (C2b) of phase b is wound such that the wire enters the slot to be wound toward the plane of the paper, and emerges from the plane of the paper on the radially outer side of the yoke portion 32a that constitutes the slot. In other words, the winding directions of the second coil 42 of phase a and the second coil 42 of phase b are opposite.

[0065] In this way, by configuring the coils 41 and 42, the first coil 41 in this motor drive system 1 functions as a rotational inductance that acts on the magnet 30a to form a rotating magnetic field. The second coil 42 can also form a rotating magnetic field and functions as a rotational inductance. Furthermore, the second coil 42 can store magnetic energy and also functions as a boost inductance that increases the voltage of the battery 2.

[0066] (Controller, electronic circuit) Figure 5 shows a simplified block diagram of the motor 3, controller 7, and electronic circuit 5 that constitute the motor drive system 1. As mentioned above, the controller 7 and electronic circuit 5 have a simple structure and can be mounted on the electronic circuit board 106.

[0067] The motor drive system 1 has a pair of DC input terminals (positive DC input terminal 50a and negative DC input terminal 50b). The positive DC input terminal 50a is connected to the positive terminal of the battery 2, and the negative DC input terminal 50b is connected to the negative terminal of the battery 2.

[0068] The electronic circuit 5 includes a positive terminal main line 51, a negative terminal main line 52, an H-bridge circuit 60, a DC bus capacitor 54, a-phase relay line 55a, and a-phase relay line 55b. The H-bridge circuit 60 and the DC bus capacitor 54 are connected in parallel between the positive terminal main line 51 and the negative terminal main line 52.

[0069] The DC bus capacitor 54 is connected to one end of the positive main wire 51 and the negative main wire 52. As will be described later, the DC bus capacitor 54 functions as a DC bus that applies a voltage higher than that of the battery 2 to the motor 3. The DC bus capacitor is, for example, an electrolytic capacitor (it may also be a film capacitor).

[0070] An H-bridge circuit 60 is connected to the other ends of the positive terminal main wire 51 and the negative terminal main wire 52. The negative terminal main wire 52 extends further from the H-bridge circuit 60, and its other end is connected to the negative terminal DC input terminal 50b.

[0071] The H-bridge circuit 60 includes a-phase leg 61a and a b-phase leg 61b interposed between the positive terminal main wire 51 and the negative terminal main wire 52. Two switching elements are arranged in series in each of these a-phase leg 61a and b-phase leg 61b. Specifically, the upper switching element 62u and the lower switching element 62d are arranged in order from the positive terminal main wire 51 side (S1 and S2, S3 and S4).

[0072] These switching elements 62u and 62d consist of power semiconductor elements such as MOSFETs and IGBTs. A recirculating diode is connected in antiparallel to each switching element 62u and 62d.

[0073] In motor 3, one end of the a-phase coil array 45a described above is connected to one end of the b-phase coil array 45b described above at a relay point 63. The relay point 63 is connected to the positive side DC input terminal 50a.

[0074] On the other hand, the other end of the a-phase coil array 45a is connected to the midpoint of the a-phase leg 61a via the a-phase relay line 55a. The other end of the b-phase coil array 45b is connected to the midpoint of the b-phase leg 61b via the b-phase relay line 55b.

[0075] The controller 7 consists of hardware such as a processor, memory, and interface, and software such as a control program and control data implemented in the memory. The controller 7 receives feedback values ​​from the motor 3 and the electronic circuit 5, such as DC current, AC current, DC voltage, AC voltage, motor speed, and rotation angle. Based on these feedback values, the controller 7 outputs control signals to each switching element S1 to S4 to control the on / off state of each switching element S1 to S4.

[0076] (Control of electronic circuits by a controller) In this motor drive system 1, the controller 7 controls the predetermined electronic circuit 5 described above so that alternating current iac and direct current idc flow through the first coil 41 and the second coil 42. By doing so, the single-phase motor 3 is driven while boosting the voltage of the battery 2.

[0077] Specifically, to increase the voltage of the battery 2, a control is performed in which a DC current idc flows through the first coil 41 and the second coil 42 (additive mode control), and to rotate the rotor 30, an AC current iac flows through the first coil 41 and the second coil 42 (differential mode control).

[0078] Specifically, in additive mode control, the controller 7 turns both the upper switching elements S1 and S3 of the a-phase leg 61a and the b-phase leg 61b, and both the lower switching elements S2 and S4 of the a-phase leg 61a and the b-phase leg 61b, on or off for the same period of time. The second coil functions as an inductance for boosting the voltage.

[0079] On the other hand, in differential mode control, the controller 7 turns the upper switching element S1 of the a-phase leg 61a and the lower switching element S4 of the b-phase leg 61b, and the lower switching element S2 of the a-phase leg 61a and the upper switching element S3 of the b-phase leg 61b on or off for the same period of time. In differential mode control, the first coil 41 and the second coil 42 function as inductances for motor rotation. At this time, in the (0,1) operation, the energy stored in the second coil 42 (C2a) is also used to charge the DC bus capacitor 54. Then, in the (1,0) operation, energy is stored in the second coil 42 (C2b). In this way, it also functions as a boost inductance in differential mode.

[0080] Figure 6 shows the relationship between the voltages Va and Vb of phase a and the voltage Vab between them when these phases are driven by a single pulse. The (1,0) etc. shown in Figure 6 represent the switching patterns of the upper switching elements S1 and S3 of each phase. The voltage change in each phase corresponds to the on / off state of the upper switching elements S1 and S3 of each phase. "1" indicates the on state, and "0" indicates the off state.

[0081] For example, (1,0) is a pattern where the upper switching element S1 of phase a is on and the upper switching element S3 of phase b is off. There are four switching patterns for the upper switching elements S1 and S3 of each phase: (1,0), (1,1), (0.1), and (0,0). Based on the relationship with each mode control, the switching patterns of the lower switching elements S2 and S4 of each phase are also uniquely determined in relation to these patterns.

[0082] Figure 7 shows the state of the electronic circuit 5 corresponding to these switching patterns. In differential mode control, the switching patterns are (0,1) and (1,0). In additive mode control, the switching patterns are (1,1) and (0,0). As shown by the white arrows in Figure 7, differential mode control and additive mode control are executed alternately.

[0083] In the switching patterns of differential mode control and summation mode control, alternating current iac and direct current idc flow through the electronic circuit 5. The alternating current iac rotates the motor 3. The direct current idc boosts the voltage of the battery 2. These two currents flow through a common electronic circuit 5. Therefore, copper losses can be reduced compared to when separate circuits are used for each.

[0084] In sum-mode control, a DC current idc flows due to the voltage of battery 2. This causes a boost operation to be performed in the a-phase leg 61a and b-phase leg 61b, where the magnetic energy stored in the second coil 42 is used to store charge in the DC bus capacitor 54. As a result, the voltage of the DC bus capacitor 54 is raised above the voltage of battery 2. However, even in sum-mode control, if the energy released to the DC bus capacitor 54 is less than the energy stored in the second coil 42, an AC current iac may flow through the first coil 41 and the second coil 42.

[0085] In contrast, in differential mode control, the voltage of the DC bus capacitor 54 causes an alternating current iac to flow through the first coil 41 and the second coil 42. As a result, a rotating magnetic field is formed in the motor 3, causing the rotor 30 to rotate.

[0086] In differential mode control, the DC current idc that continues to flow from the summation mode control releases the magnetic energy stored in the second coil 42 from one of the a-phase leg 61a and the b-phase leg 61b. Meanwhile, magnetic energy is stored in the other of the a-phase leg 61a and the b-phase leg 61b.

[0087] (Motor model) In this motor drive system 1, the currents flowing through phase a and phase b (phase a current ia, phase b current ib) are separated into a DC component iv and an AC component it. The transformation matrix C is shown in equation (1) of Figure 8. The first row of equation (1) represents taking the sum of the two phase currents ia and ib. The second row of equation (1) represents taking the difference between the two phase currents ia and ib.

[0088] According to equation (1), the former separates the DC component iv related to the voltage boost, and the latter separates the AC component it related to the rotational torque. Specifically, as shown in equation (2) in Figure 8, the a-phase current ia and b-phase current ib are separated into a DC component iv and an AC component by the action of C.

[0089] Equation (3) in Figure 8 is the voltage equation relating to the voltage of motor 3. Ea is the back electromotive force caused by magnet 30a, and Edc is the voltage at relay point 63 (voltage of battery 2). L1 is the rotational inductance of the first coil 41 and the second coil 42, and L2 is the boost inductance of the second coil 42. Ra is the winding resistance of the a-phase coil array 45a and the b-phase coil array 45b.

[0090] (Analysis of magnetic flux distribution) Figure 9A shows an example of the analysis results of the magnetic flux distribution of motor 3. (a) shows the state when a predetermined AC current iac is applied to motor 3, corresponding to the differential mode. (b) shows the state when a predetermined DC current idc is applied, corresponding to the summation mode.

[0091] Figure 9A(a) shows that an 8-pole rotating magnetic field is formed. In other words, in this motor drive system 1, the motor 3 can be rotated by utilizing the inductance of the first coil 41, which is concentratedly wound on the teeth portion 32b, and the second coil 42, which is toroidally wound.

[0092] At this time, considering the polarity (positive and negative) of the alternating current iac and the winding direction of the second coils 42 of phase a and phase b, when the alternating current iac flows, the second coil 42 of phase a and the second coil 42 of phase b are differentially connected. The direction of the magnetic flux generated in the second coil 42 of phase a and the direction of the magnetic flux generated in the second coil 42 of phase b are opposite. As a result, when the magnetic flux collides, there are alternating points where the magnetic flux flows toward the teeth portion 32b located between them and points where the magnetic flux from the teeth portion 32b is drawn in, forming a rotating magnetic field. No flow of magnetic flux is generated that passes through the yoke portion 32a in the circumferential direction.

[0093] In contrast, as shown in Figure 9A(b), when a DC current idc flows, the second coil 42 of phase a and the second coil 42 of phase b are connected in an additive manner. The direction of the magnetic flux generated in the second coil 42 of phase a and the direction of the magnetic flux generated in the second coil 42 of phase b are the same. Therefore, as indicated by the arrows, a flow of magnetic flux is generated that passes through the yoke portion 32a in the circumferential direction. In other words, in this motor drive system 1, the voltage can be boosted by utilizing the inductance of the second coil 42 toroidally wound on the yoke portion 32a.

[0094] Figure 9B shows the magnetic flux distribution of motor 3 under a predetermined high-power state. It can be seen that a magnetic field for rotation and a magnetic field for voltage boosting are formed, and that motor 3 can rotate while boosting the voltage of battery 2. In this example, because of the high power output, magnetic saturation was observed in a part of the yoke section 32a. However, this motor 3 is single-phase. Therefore, even if such interference with magnetic field formation due to magnetic saturation is observed, it has almost no effect on the motor output.

[0095] <Verification of Motor Drive System Performance> Figure 10 shows an example of the verification results obtained from electromagnetic field analysis regarding the effect of the second coil 42. This analysis compared the presence or absence of the second coil 42 in the motor drive system 1. In this analysis, the motor 3 was driven at a predetermined ultra-high speed of 100,000 r / min or more.

[0096] (a) shows the waveform of the induced voltage under no load, and (b) shows the electromagnetic field analysis results. From the FFT analysis results, a voltage increase effect of approximately 25% was observed in the fundamental wave component (first order). This voltage increase effect corresponded to the ratio of the number of first coils 41 and second coils 42 inside the slot. Therefore, it was confirmed that the second coil 42 contributes not only to voltage boosting but also to improving rotational output.

[0097] Figure 11 shows an example of the analysis results for torque in the FFT analysis of Figure 10. (a) is a graph showing the relationship between the AC current iac and torque, and (b) is the torque waveform at approximately 30 A rms. This analysis compares the case where there is no DC current idc (square), the case where the AC current iac is accompanied by the DC current idc (circle, corresponding to this motor drive system 1), and the case where the second coil 42 is absent (triangle).

[0098] As a result, at approximately 30 Arms, a torque increase of about 19% was observed when the AC current iac was accompanied by a DC current idc compared to when the second coil 42 was absent. In other words, while this motor drive system 1 shows a slight decrease in torque (a few percent) compared to using only the AC current iac, the improvement in rotational output due to the presence of the second coil 42 is greater, demonstrating its superiority.

[0099] (An example of a simulation) Figure 12 shows an example of the simulation results for this motor drive system 1 performed under predetermined conditions. Motor 3 is driven at the ultra-high speed rotation described above. In the simulation, the AC current iac (effective value) was set to 10A, and the command value of the DC bus voltage (corresponding to the voltage of the DC bus capacitor 54) was changed from 30V to 36V.

[0100] The simulation results confirm that the DC bus voltage and AC current iac change independently, following the command values.

[0101] Furthermore, the disclosed technology is not limited to the embodiments described above, but also encompasses various other configurations. For example, the configuration of motor 3 is just one example. The configuration can be modified as appropriate depending on the specifications.

[0102] For example, the coil may be configured such that the concentrated winding first coil 41 is omitted, and only the toroidal winding second coil 42 is used. Specifically, as shown in Figure 13, the number of turns of the second coil 42 can be increased so that the space factor does not decrease significantly due to the elimination of the first coil. In a configuration in which the axial length of the stator core 32 is increased, the output will be lower than that of the motor 3 in the embodiment described above, but effects such as a thinner motor can be obtained.

[0103] Furthermore, the number of magnetic poles of the rotor 30 may differ from the number of poles of the stator 31, such as 6 poles. However, from the viewpoint of miniaturization, it is preferable that the number be the same. The coils shown in the embodiment are simplified, and their form, such as the number of turns, depends on the specifications. [Explanation of Symbols]

[0104] 1. Motor drive system 2 batteries 3 motors 5 Electronic circuit 7 Controllers 10 shafts 30 rotors 30a Magnet 31 stata 32 stator cores 32a Yoke section 32b Teeth section 32c protrusion 33 Steel plate 34a Outer ring 34b Inner ring 41. First coil 42. Second coil 45a a-phase coil array 45b b-phase coil array 51 Positive side main line 52 Negative side main line 54 DC bus capacitors 60 H-bridge circuit 61a a phase leg 61b b-phase leg 62 Switching elements 63 relay points 100 vacuum cleaner 200 power tools

Claims

1. A motor drive system that drives a single-phase motor by boosting the battery voltage through the control of a predetermined electronic circuit with a controller, The aforementioned motor is A rotatable rotor including magnets that make up multiple magnetic poles, A stator comprising a stator core and a plurality of coils, facing the rotor in the circumferential direction via an air gap, It has, The stator core is The annular yoke section, 2N teeth (where N is a natural number) protrude radially from the yoke towards the rotor, It has, The aforementioned coil is By concentrating windings on each of the aforementioned teeth portions, a first coil consisting of a phase and b phase arranged alternately in the circumferential direction is formed. A second coil consisting of alternating a-phase and b-phase is formed by toroidal winding around each of the portions between the two circumferentially adjacent teeth portions in the yoke portion, It consists of, The first coil of phase a is connected in series with the second coil of phase a to form a phase coil array. The first coil of the b-phase is connected in series with the second coil of the b-phase to form a b-phase coil array. The first coil and the second coil of phase a and phase b are constructed by winding them in opposite directions. A motor drive system in which alternating current and direct current flow through the first coil and the second coil, respectively.

2. In the motor drive system according to claim 1, A motor drive system in which the number of magnetic poles and teeth of the rotor are equal.

3. In the motor drive system according to claim 1, The aforementioned electronic circuit is Positive electrode main wire and negative electrode main wire, An H-bridge circuit and a DC bus capacitor are connected in parallel between the positive main wire and the negative main wire. It has, The H-bridge circuit includes an a-phase leg and a b-phase leg, each having an upper switching element and a lower switching element arranged in series from the positive terminal main line side, with one end of the a-phase coil array and one end of the b-phase coil array connected to each other at an intermediate point, the midpoint of the a-phase leg and one end of the a-phase coil array connected, and the midpoint of the b-phase leg and one end of the b-phase coil array connected. A motor drive system in which the relay point is configured to be connectable to the positive terminal of the battery, and the negative terminal main line is configured to be connectable to the negative terminal of the battery.

4. In the motor drive system according to claim 3, The aforementioned controller A summation mode control that turns both the upper switching elements of the a-phase leg and the b-phase leg, and both the lower switching elements of the a-phase leg and the b-phase leg, on and off for the same period of time. Differential mode control that turns on or off the upper switching element of the a-phase leg and the lower switching element of the b-phase leg, and the lower switching element of the a-phase leg and the upper switching element of the b-phase leg, for the same period of time. A motor drive system that performs this task.

5. In the motor drive system according to claim 1, A motor drive system in which at least the yoke portion of the stator core is integrally formed around its entire circumference using Permendur material.

6. In the motor drive system according to claim 1, The yoke portion of the stator core is composed of an outer ring portion located radially outward and an inner ring portion located radially inward. A motor drive system in which the inner ring portion is formed integrally with the teeth portion using non-oriented electrical steel sheet, and the outer ring portion is formed using grain-oriented electrical steel sheet so that the magnetism is increased in the circumferential direction.

7. A vacuum cleaner equipped with the motor drive system described in any one of claims 1 to 6.

8. A power tool equipped with the motor drive system described in any one of claims 1 to 6.

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