JP5311109B2 - Permanent magnet commutator motor and electric tool using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress spark discharge or flashover in a commutator, without having to insert a large-capacity electrolytic capacitor in a full-wave rectifier circuit in a permanent-magnet commutator motor. <P>SOLUTION: An armature coil 6 is designed to be driven at a full-wave rectified voltage of a single-phase AC power supply 1, which has an effective value of more than 100 V. A plurality of commutator pieces 5f are formed in a number which is equal to a multiple (twice or more) of the number "n" of slots 5c formed in an armature core, that is, the number of commutator pieces is 2n, 3n, etc. In order to reduce spark discharges, the number (61, 62, and 63) of armature coils 6 wound in each slot 5c is set to an integral multiple of, for example, 2n, 3n, etc. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a permanent magnet commutator motor that can be driven by a commercial power source having a single-phase AC voltage exceeding 100 V, and a power tool using the permanent magnet commutator, and in particular, flashing in a commutator piece caused by a high voltage drive power source. The present invention relates to a permanent magnet commutator motor that prevents the occurrence of over and a power tool using the same.

  Conventionally, a permanent magnet commutator motor that uses a permanent magnet as a stator and applies a full-wave rectified commercial single-phase AC voltage to a coil wound around an armature core has been applied to a coil wound around the stator core. Since it can be reduced in size and weight as compared with a universal motor that generates a field by energizing an electric current, it is generally used as a drive source of an electric tool.

  However, as shown in FIG. 7, the permanent magnet commutator motor using the permanent magnets 3 b and 3 c as the field magnets of the stator 3 is driven by a DC power source that is a single-phase AC rectified by a full-wave rectifier. Since the rectification performance is significantly worse than that of a universal motor, an electrolytic capacitor 7 is inserted in parallel between the full-wave rectifier 2 and the brush 4 of the motor, and the waveform obtained by full-wave rectification of the single-phase AC power source 1 is further smoothed. Has been done to drive. The electrolytic capacitor 7 used for smoothing is put into practical use even if it is not inserted when the commercial AC power supply is 100V. However, it is inserted when driving with a voltage exceeding 100V, particularly 200V or more. It is common to do.

  Further, as disclosed in Patent Document 1 below, in a DC commutator motor in which an electrolytic capacitor is connected in parallel to the output side of the full-wave rectifier circuit, it is connected to the positive electrode side of a DC power source in order to reduce spark discharge. There is known a technique in which a brush having a high specific resistance is formed and a brush connected to a negative electrode side of a DC power source is formed of a material having a low specific resistance.

JP 2001-8424 A

  The present inventors have found that the following problems arise when a conventional permanent magnet commutator motor is driven by a full-wave rectified DC power supply having a single-phase AC voltage exceeding 100V.

  That is, in the conventional permanent magnet commutator motor (see FIG. 7), when driving with the single-phase AC 100V of the commercial power source 1, it is not necessary to insert the smoothing electrolytic capacitor 7 on the output side of the full-wave rectifier circuit 2. The rectification worsens at a level where there is no practical problem. However, when the single-phase AC voltage as the driving power source exceeds 100 V, particularly 200 V or more, when the electrolytic capacitor 7 for smoothing the pulsating voltage is not inserted on the output side of the full-wave rectifier circuit, The degree to which the commutation by the commutator 5a deteriorates becomes severe, and sparks are generated between the positive electrode side brush 4 and the negative electrode side brush 4 at the time of start-up and during operation. In particular, when the pulsating voltage exceeds a certain limit, the amount of charged particles flowing between the brushes increases abruptly, and an excessive spark discharge (flashover) occurs so that a large current flows between the brushes. It turns out that it leads to the failure. In order to suppress this flashover, when the commercial power source is driven at a voltage exceeding 100 V (for example, the single-phase AC voltage is 200 V), an electric field capacitor 7 of several tens μF or more is provided on the output side of the full-wave rectifier circuit. It was found that the intended purpose can be achieved by inserting and smoothing the pulsating flow power supply.

  However, the large-capacity electrolytic capacitor 7 has a drawback that the frequency of failure of the commutator motor increases because liquid leakage and expansion are likely to occur. Furthermore, since a large occupied space is required for mounting a large volume electrolytic capacitor, there is a problem that the motor and the electric tool are increased in size, and the number of assembling steps for the motor or the electric tool increases, resulting in an increase in cost. There was also a drawback of becoming.

  On the other hand, the technique of making the material of the positive side brush disclosed in Patent Document 1 different from the material of the negative side brush is to prevent misuse of the positive side brush and the negative side brush. Since it is necessary to change the shape, the number of parts and the number of assembling steps at the time of assembling are increased, resulting in a cost increase.

  Accordingly, an object of the present invention is to solve the above problems, and to use a permanent magnet commutator motor in which spark discharge is reduced with a power supply voltage exceeding a single-phase AC power supply 100V without inserting an electric field capacitor. It is to provide a power tool.

  Among the inventions disclosed in accordance with the present invention in order to solve the above problems, the characteristics of typical ones will be described as follows.

One feature of the present invention is that a stator having a pair of opposing permanent field magnets, an armature core having a plurality of slots formed so as to extend along the rotation axis direction , and the armature an armature coil wound in each slot of the core, has a plurality of commutator segments which are electrically insulated from each other, for supplying the drive current before Symbol armature coils through the commutator pieces A commutator, power supply circuit means for full-wave rectification of a single-phase AC power supply, and electrically connected to the power supply circuit means, and slides on the commutator to supply the drive current to the armature coil In a permanent magnet commutator motor comprising a pair of brushes, a full-wave rectified voltage of a single-phase AC power source having an effective value of 200 V or more is applied to the armature coil without being smoothed, and the number of slots is 12, The number of commutator pieces is 36, and each slot With 3 the number of the armature coils wound around the bets, lies in that is configured to prevent a spark discharge.

  According to still another aspect of the present invention, the permanent magnet is composed of a rare earth sintered body.

  According to still another aspect of the present invention, an inner radius (rm) of the permanent field magnet is larger than an outer radius (ra) to the outer peripheral surface of the armature core, and an inner radius ( rm) is shifted from the center of the outer radius (ra) of the armature core by a predetermined value (δ), so that the gap between the permanent field magnet and the armature core is changed to the center of the permanent field magnet. It is configured to continuously expand from the end toward the end.

  According to still another aspect of the present invention, a housing, an electric motor housed in the housing, a tip tool for machining a workpiece to be mounted on one end of the housing, and in the housing And a power transmission mechanism unit that is housed and drives the tip tool by the power of the electric motor. The electric motor is a permanent magnet commutator motor having the above characteristics.

  According to the characteristics of the present invention, the plurality of commutator pieces are an integer multiple (2n, 3n,...) That is at least twice the number of slots (n) formed in the armature core. .) And the number of the armature coils wound in each slot is set equal to the integral multiple (2n, 3n,...) To reduce spark discharge. The flashover that flashes between the pair of brushes can be suppressed. Thereby, abrasion of a brush and a commutator can be suppressed. In particular, by setting the commutator piece of the commutator to three times or more with respect to the number of slots n, it is possible to prevent the occurrence of flashover for a single-phase AC voltage having an effective value of 200 V or more.

  According to the other feature of the present invention, since the field magnet of the stator is made of a rare earth sintered body, the amount of magnetic flux can be increased by the stator magnet, and the total number of turns of the armature coil is reduced. be able to. As a result, the number of coil turns between the commutator pieces can be reduced, further commutation can be improved, and the spark discharge suppressing effect can be increased. Conversely, if the number of coil turns is not reduced, the permanent magnet can be made smaller, and the motor can be made smaller by pulling it.

  Furthermore, according to the other feature of the present invention, the inner radius rm of the permanent magnet is made larger than the outer radius ra of the armature core, and the center of the inner radius rm of the permanent magnet is made larger than the center of the outer radius ra of the armature core. By shifting the predetermined value δ, the gap between the permanent magnet and the armature core can be continuously expanded from the central portion toward the end portion of the permanent magnet. Thereby, by eliminating a sudden change in magnetic flux at the end of the permanent magnet, the cogging torque (torque unevenness) of the armature can be suppressed, and the mechanical sliding contact between the carbon brush and the commutator is stabilized. be able to. In this case, spark discharge caused by unstable slidability of the carbon brush can be suppressed.

  The above and other objects, and the above and other features of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Moreover, the same code | symbol is attached | subjected also about the member or component similar to the prior art mentioned above.

[Overall Configuration of Electric Tool 100]
FIG. 1 is a cross-sectional view (front view) of an entire electric power tool according to an embodiment when the permanent magnet commutator motor of the present invention is applied to a rotary hammer drill. First, the configuration of the entire power tool will be described with reference to FIG.

  The rotary hammer drill (electric tool) 100 uses a permanent magnet commutator motor 70 (hereinafter simply referred to as “commutator motor 70”) as a driving source of power. The housing 101 includes a body housing portion 101a that extends along the same direction as the rotation axis of the commutator motor 70, and a handle housing portion 101b that hangs from one end of the body housing portion 101a.

  A power cable 104 for supplying a single-phase AC 200V commercial power source serving as a driving power source for the commutator motor 70 is led out at the lower end of the handle housing portion 101b. Further, a switch mechanism portion 106 is mounted in the handle housing portion 101b, and the switch mechanism portion 106 can be turned on / off to supply power to the commutator motor 70 in accordance with a trigger pulling operation by an operator. , Trigger 105 is mechanically coupled. A full-wave rectifier (circuit board) 2 for full-wave rectifying the single-phase AC power supply 200V is mounted between the power cable 104 and the switch mechanism unit 106.

  The stator 3 of the commutator motor 70 mounted in the body housing portion 101a includes a pair of permanent magnets (N pole and S pole field magnets) 3b, 3c made of a rare earth sintered body having a high magnetic flux density, It is comprised from the circular shaped stator yoke 3a which forms the magnetic path of a pair of permanent magnet. The armature 5 of the commutator motor 70 includes an armature core 5b insulated from the armature shaft 5e by the resin insulating layer 5g, an armature coil 6 wound around the armature core, and an armature coil 6. And a commutator 5a electrically connected to one end. A pair of brushes 4 are provided in contact with the commutator 5a. The pair of brushes 4 are constituted by carbon brushes held by a brush holder 4a, and the pair of brushes 4 are electrically connected to the positive electrode side and the negative electrode side of the DC output (rectified output) of the full-wave rectifier circuit board 2, respectively. It is connected.

  The rotational output of the commutator motor 70 is transmitted to the power transmission mechanism 107 via a pinion gear (not shown) coupled to the output shaft of the rotary shaft 5e. Although not shown, the power transmission mechanism 107 includes a speed reduction mechanism including a pinion gear and the like, and an impact mechanism including a cylinder, a piston, a clutch mechanism, and the like. By this power transmission mechanism 107, the rotational output of the commutator motor 70 is simultaneously applied as a rotational force and a striking force to the drill bit (tip tool) 103 attached by the tool holding unit 102, and the tip tool 103 is driven to rotate. be able to. A cooling fan (not shown) is attached to the rotation output shaft (power transmission mechanism 107 side) of the commutator motor 70 and is configured to suck cooling air from the wind window 108.

  In such an electric tool 100, when an operator pulls the trigger 105 and drives the commutator motor 70 via the switch mechanism unit 106, the rotational force on the output shaft (5e) of the commutator motor 70 is transmitted as power. The mechanism 107 is decelerated and converted into a striking force, and the decelerating rotational force and striking force are transmitted to the tip tool 103. Thereby, the drill 103 can implement a drilling operation in the workpiece.

[Configuration of Commutator Motor 70]
In the electric power tool 100, in particular, the commutator motor 70 is configured as follows.
The armature core 5b of the commutator motor 70 includes twelve armature cores separated from each other by twelve slots 5c (1 to 12), as shown in an armature coil development view (schematic diagram) in FIG. It is comprised by the teeth part 5d. The commutator 5a is composed of 36 commutator pieces 5f (1 to 36) separated from each other by an insulating layer (not shown). That is, the commutator piece 5f has a number 3n (for example, 36) that is three times the number n (for example, 12 slots) of the slots 5c formed in the armature core 5b.

  The armature coil 6 having one end electrically connected to the commutator piece 5f has three slots 5c (slot No. 1 and slot No. 6 in FIG. 3) opposed to each other in the armature core 5b. The number of commutator pieces 3n / slot number n = 3 coils 61, 62 and 63 are wound. That is, three coils 61, 62 and 63 connected to three adjacent pairs of commutator pieces 5f (for example, No. 36, No. 1 and No. 2 commutator pieces 5f) are connected to the same slot No. 1 is wound. Each so-called slot becomes a three-held coil around which three coils are wound. The DC power source that has been full-wave rectified by the full-wave rectifier circuit board 2 is supplied to the armature coil 6 via the pair of carbon brushes 4 and the commutator 5a. FIG. 2 shows a circuit diagram of the commutator motor 70.

  Further, as shown in FIG. 3, the position of the carbon brush 4 is opposite to the rotation direction of the armature 5 from the middle position between the N pole 3b and the S pole 3c of the permanent magnet, so-called geometric neutral point. The position is shifted to an angle θ in the direction. The pair of carbon brushes 4 electrically connected to the positive electrode side and the negative electrode side of the DC power source 2 are both made of the same material having the same specific resistance and the same shape and size. As shown in FIG. 3, the width b of the carbon brush 4 is 2.5 times or less of the width a of the commutator piece 5f constituting the commutator 5a in consideration of the processing accuracy of the carbon brush, that is, The brush covering is configured to be 2.5 or less.

  According to the configuration of the commutator motor 70, a single-phase AC voltage exceeding 100 V (effective value) can be obtained without connecting a large electrolytic capacitor (7) having a high breakdown voltage and a high capacity as shown in FIG. Flashover can be prevented. Of course, as shown in FIG. 7, if necessary, one capacitor 8a is provided between the single-phase AC power supply lines on the input side of the full-wave rectifier circuit 2 in order to suppress electromagnetic noise (pulsed surge voltage). A capacitor set composed of two capacitors 8b and 8c may be mounted between the ground. In this case, since the line capacitance inserted between the single-phase AC power supply lines is about 0.6 μF at maximum with no polarity, a smoothing effect on the rectified voltage cannot be obtained at all and there is no action of suppressing flashover.

[Commutation performance of commutator motor 70]
According to the commutator motor 70, the following commutation performance can be obtained.
(1) When the supply voltage between the pair of carbon brushes 4 on the positive electrode side and the negative electrode side, that is, the voltage between armatures is Va (effective value) and the number of commutator pieces 5f is Nseg, The voltage Vseg is Vseg = 2Va / Nseg. For example, if the number of slots 5c of the armature core is 12 and the number of commutator pieces 5f is 36, the number of commutators 5a is 36. The voltage Vseg between 5f can be reduced to 2/3.

  In addition, the number of armature coils 6 disposed in each slot is two (2) as many as the number of armature coils 6 when 24 commutators 5a of commutator pieces 5f are used. Since three (three) can be provided, the coil resistance Rseg and the coil inductance Lseg inserted between the adjacent commutator pieces 5f can be reduced.

  Accordingly, since the supply voltage Va between the commutator pieces 5f, the coil resistance Rseg, and the coil inductance Lseg can be set small, the number of the armature core slots 5c is 12, and the number of commutator pieces 5f is 36 commutators. 5a can suppress the occurrence of flashover, which is an excessive spark generated between the positive and negative carbon brushes 4 at the time of start-up and operation, compared to the case where several 24 commutators 5a of commutator pieces 5f are used. It is considered experimentally.

  FIG. 4 shows a case where the number of the armature core slots 5c is 12 and the number of the commutator pieces 5f is three times 36, and the number of the armature core slots 5c is 12 and the number of the commutator pieces 5f is 2 The result of measuring the spark discharge (occurrence of flashover) at the time of start-up by changing the voltage value (effective value) of the single-phase AC power supply 1 in the case of 24 times the number is shown. The outer diameter of the armature core 5b of the commutator motor 70 used in this study is 35.7 mm, the thickness of the armature core 5b is 22 mm, and the input power of the commutator motor 70 is about 650 W.

  As is clear from FIG. 4, the flashover occurs at the power supply voltage of 200V for the 24 commutator pieces, whereas the flashover occurs at the power supply voltage of 260V for the 36 commutator pieces. Although not shown in FIG. 4, occurrence of flashover was observed for 12 commutator pieces at a power supply voltage of 150 V or less. As a result, as shown in FIG. 5, when the power supply voltage exceeds 100 V and is 200 V or less, 24 commutator pieces are used and the number of coils is two. When the power supply voltage exceeds 200 V and is 260 V or less, 36 commutator pieces are used. If the number of coils is set to 3, the occurrence of flashover can be suppressed. According to the present invention, in particular, in order to suppress flashover for a single-phase AC power supply voltage of 200 V, the number of coils in the slot may be three with 36 commutator pieces.

  (2) The permanent magnet motor 70 shifts the carbon brush 4 from the geometric neutral point by an angle θ in the direction opposite to the rotation direction of the armature 5 so that the rectifying coil of the armature coil 6 has a magnetic flux density. It can be short-circuited by the carbon brush 4 at a small position, and the electrical rectification performance can be further improved.

  (3) The permanent magnet motor 70 has a brush covering of 2.5 or less, and the four commutator pieces 5f are not short-circuited by one carbon brush 4, thereby reducing the number of coils that are simultaneously rectified. . Thereby, the effect of the rectification improvement is further improved.

[Modification of Commutator Motor 70]
As shown in FIG. 6, the inner radius rm of the pair of permanent magnets 3b, 3c fixed to the stator yoke 3a is larger than the outer radius ra of the armature core 5b, and the inner radius rm of the permanent magnets 3b, 3c. Is shifted from the center of the outer radius ra of the armature core 5b by δ, so that the gap (separation distance) between the permanent magnets 3b and 3c and the armature core 5b is directed from the center of the permanent magnets 3b and 3c toward the end. May be continuously expanded. Thereby, the cogging torque (torque nonuniformity) of the armature 5 can be suppressed by eliminating a sudden change in the magnetic flux at the ends of the permanent magnets 3b and 3c. Further, since the mechanical sliding contact between the carbon brush 4 and the commutator 5a can be stabilized, the rectification performance can be further stabilized and spark discharge can be suppressed.

  In the above embodiment, the material of the pair of permanent magnets 3a and 3b fixed to the inner peripheral surface of the ferromagnetic stator yoke 3a is preferably composed of a rare earth sintered magnet having a high magnetic flux density. . As a result, the motor can be reduced in size and weight. Moreover, the occurrence of flashover can be prevented regardless of the motor without the electromagnet coil that forms the field magnet of the stator.

  As will be apparent from the above description of the embodiment, according to the present invention, spark discharge or flashover can be suppressed with respect to a voltage with a single-phase AC power supply voltage exceeding 100V. In particular, it can be applied to driving with a high voltage power supply of 200 V or higher, and spark discharge or flashover can be suppressed without using a large smoothing electrolytic capacitor. Thereby, since it becomes possible to omit the connection of the conventional smoothing electrolytic capacitor (7), an inexpensive and highly reliable commutator motor and electric tool can be provided.

  As mentioned above, although the invention made | formed by this inventor was demonstrated based on embodiment, this invention is not limited to the said embodiment, A various change is possible within the range which does not deviate from the summary.

Sectional drawing of the permanent magnet commutator motor and electric tool which concern on one Embodiment of this invention. The circuit diagram of the permanent magnet commutator motor shown in FIG. FIG. 2 is a development view of the permanent magnet commutator motor shown in FIG. 1. The graph which calculated | required experimentally the relationship between a single phase alternating current power supply voltage and spark discharge about the permanent magnet commutator motor shown in FIG. The characteristic table which calculated | required the relationship between a single phase alternating current power supply voltage and a spark discharge from the graph shown in FIG. Sectional drawing which shows the modification of the permanent magnet commutator motor which concerns on this invention. The circuit diagram which shows the conventional permanent magnet commutator motor.

Explanation of symbols

1: Single-phase AC power supply (commercial power supply) 2: Full-wave rectifier circuit (substrate)
3: Stator 3a: Stator yoke 3b, 3c: Stator permanent magnet 4: Brush 4a: Brush holder 5: Armature 5a: Commutator 5b: Armature core 5c: Armature core slot 5d: Armature core teeth 5e: Armature shaft 5f: Commutator piece 6: Armature coil 61: First armature coil 62: Second armature coil 63: Third armature coil 7: Electrolytic capacitors 8a, 8b, 8c: Noise Capacitor for suppression 70: Permanent magnet commutator motor 100: Hammer drill (electric tool) 101: Housing 101a: Body housing part 101b: Handle housing part 102: Tool holding part 103: Tip tool 104: Power cable 105: Trigger 106: Switch mechanism Part 107: Power transmission mechanism part 108: Wind window a: Commutator piece width b: Width in rotation direction of carbon brush a: outside the armature core radius rm: inner radius of the permanent magnet [delta]: rm and deviation of the center of ra

Claims (4)

A stator with a pair of opposing permanent field magnets;
An armature core having a plurality of slots formed to extend along the rotation axis direction ;
An armature coil wound in each slot of the armature core;
A plurality of commutator segments which are electrically insulated from each other, and commutator for supplying a drive current before Symbol armature coils through the commutator pieces,
Power supply circuit means for full-wave rectification of a single-phase AC power supply;
In a permanent magnet commutator motor comprising a pair of brushes electrically connected to the power supply circuit means and sliding on the commutator to supply the drive current to the armature coil,
A full-wave rectified voltage of a single-phase AC power source having an effective value of 200 V or more is applied to the armature coil without being smoothed,
The number of slots is 12, the number of commutator pieces is 36, and the number of armature coils wound in each slot is 3, so that spark discharge is prevented. Permanent magnet commutator motor characterized by The permanent magnet commutator motor according to claim 1 , wherein the permanent magnet is made of a rare earth sintered body. The inner radius (rm) of the permanent field magnet is made larger than the outer radius (ra) to the outer peripheral surface of the armature core, and the center of the inner radius (rm) of the permanent field magnet is set to the outer radius of the armature core. The gap between the permanent field magnet and the armature core is continuously expanded from the center to the end of the permanent field magnet by shifting by a predetermined value (δ) from the center of (ra). The permanent magnet commutator motor according to claim 1, wherein the permanent magnet commutator motor is provided. A housing; an electric motor housed in the housing; a tip tool for machining a workpiece mounted on one end of the housing; and the tip of the tip housed in the housing by the power of the electric motor A power transmission mechanism for driving the tool,
The said electric motor was comprised by the permanent magnet commutator motor described in any one of Claim 1 thru | or 3. The electric tool characterized by the above-mentioned.

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