Patent Grant
11986924
This application is a 371 application of the international PCT application serial no. PCT/JP2017/019711, filed on May 26, 2017, which claims the priority benefit of Japan application no. 2016-130338, filed on Jun. 30, 2016 and Japan application no. 2017-013050, filed on Jan. 27, 2017. The entirety of each of the above-mentioned patent applications is hereby incorporated by references herein and made a part of this specification.
The present invention relates to an electrically powered tool such as a disk grinder.
In portable electrically powered tools such as a disk grinder, a handle connected to protrude to the rear side from a motor housing in which a motor is held is provided. An operator grips the handle with one hand and performs an operation by pressing the motor housing itself or a side handle attached to the motor housing with the other hand. The housing of the disk grinder is a housing made of a metal or a synthetic resin. However, unlike a small size disk grinder, a medium or larger size disk grinder has a cylindrical motor housing because the size and output of the motor are larger and has, for example, a left and right division type handle housing that is divided in a cross section including a longitudinal axis on the rear side thereof. A configuration of the grinder in which a handle is provided behind such a motor housing is known in Patent Literature 1. In addition, in order to reduce vibration generated during working transmitted from a main body of an electrically powered tool to a handle (switch handle) connected to the main body of the tool, a vibration isolation mechanism is generally provided in a part connected to the handle. In an electrically powered tool including such a vibration isolation handle, an elastic body is inserted into a part connecting the main body of the electrically powered tool and the handle and the elastic body effectively absorbs vibration generated from the main body of the tool. For example, an electrically powered tool including a vibration isolation handle is disclosed in Patent Literature 2.
For tools having various working forms, it is important to have operability accordingly. For example, a disk grinder may have a working form such as polishing and cutting, and an operation is performed by changing a position of a tip tool. In order to perform polishing using the disk grinder, a grinding stone is attached and an annular surface of the disk-shaped grinding stone is pressed against a surface to be polished for a polishing operation. On the other hand, in order to perform cutting using the disk grinder, a rotary blade is attached and pressing is performed so that a surface of a disk-shaped rotary blade is orthogonal to a surface of a material to be polished for a cutting operation. In this manner, in the case of the disk grinder, an orientation of a body part during working is changed according to the tip tool attached. However, in this case, the position of the handle is also changed according to the change of the orientation of the body part.
In recent years, by adopting a brushless DC motor, electrically powered tools have become smaller and lighter. In addition, there is a trend for further increasing an output. A brushless DC motor is driven by using an inverter circuit using a semiconductor switching element. For the semiconductor switching element used in the inverter circuit, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), and the like are used. However, since such electronic elements generate a large amount of heat, it is necessary to cool them sufficiently. In addition, in electrically powered tools having an input of greater than 1,000 w, it is necessary to increase the capacity of IGBTs or electrolytic capacitors, a circuit board having these mounted thereon becomes larger, and thus it is necessary to devise a circuit board disposition method therefor.
The present invention has been made in view of the above background, and an objective of the present invention is to provide an electrically powered tool having improved workability by making a handle section rotatable with respect to a body part. Another objective of the present invention is to provide an electrically powered tool in which a vibration isolation elastic body is disposed between a body part and a handle section, excess deformation of the vibration isolation elastic body is prevented, and performance can be maintained over a long time of usage. Still another objective of the present invention is to provide an electrically powered tool using a cylindrical motor housing and in which switching elements and capacitors for driving a brushless motor are effectively disposed and a cooling effect thereof is improved. Yet another objective of the present invention is to provide an electrically powered tool in which a drive circuit for driving a motor is mounted on a body part on the side in front of a handle rotation mechanism section that rotates with respect to a main body of the electrically powered tool, cooling air is introduced into a motor housing through the rotation mechanism section from a handle side, and thus the cooling efficiency of the drive circuit is not reduced even in the handle rotation mechanism.
Representative aspects of the invention disclosed in this specification will be described as follows. According to one aspect of the present invention, there is provided an electrically powered tool including a cylindrical integral motor housing that accommodates and supports a brushless motor; a cooling fan that is rotated by the brushless motor; a spindle that is rotated by the brushless motor; a power transmission mechanism configured to transmit a rotational force of the brushless motor to the spindle; a gear case which is attached to an other side of the motor housing in an axial direction and in which the power transmission mechanism is accommodated; a handle housing which is connected to one side of the motor housing and in which a grip section is formed; and a drive circuit on which a switching element is mounted and which drives the brushless motor, wherein an air flow window is provided in the handle housing and a discharge opening is provided in the gear case. When the cooling fan rotates, air is sucked from the air flow window into the handle housing, the sucked air passes through an inside of the motor housing and cools the drive circuit, and then cools the brushless motor, and is discharged from the discharge opening to an outside. The handle housing has a diameter-increased section that has a larger diameter than the grip section and is connected to the motor housing, the diameter-increased section is positioned between the grip section and the motor housing, and the air flow window is provided in the diameter-increased section. In addition, the drive circuit is mounted on a first circuit board that extends in a direction substantially perpendicular to a rotation axis of the brushless motor. The first circuit board is accommodated in a case having an opening, and the opening of the case is disposed to face an air intake side.
According to another aspect of the present invention, an elastic body is provided between the motor housing and the handle housing, and the handle housing is supported by the motor housing via the elastic body. In addition, a rotation mechanism including a support member is provided between the motor housing and the handle housing, and the support member supports the handle housing to be rotatable about an axis of the brushless motor. In addition, the elastic body includes an inner elastic body provided on the side close to a central axis of the motor housing and an outer elastic body provided on the side far from the central axis of the motor housing, and the inner elastic body and the outer elastic body are provided superimposed on each other in the axial direction of the brushless motor. A metal annular member is provided between the outer elastic body and the handle housing.
According to still another aspect of the present invention, the rotation mechanism includes a swing supporting section that supports the handle housing in a swinging manner, and when the handle housing swings with respect to the motor housing, the elastic body provided in the swing supporting section is compressed. The rotation mechanism includes the support member that is fixed to the motor housing side and an intermediate member that is supported by the support member, the support member is formed of two or more separate pieces, and the intermediate member is clamped by the support member. The handle housing and the intermediate member are supported by the support member to be rotatable about an axis of the brushless motor. The intermediate member includes a rail part that rotatably supports the handle housing, the swing supporting section is formed on the side of the support member, a groove is formed on the side of the handle housing, the inner elastic body is provided in the swing supporting section. When the groove and the rail part are engaged, the handle housing is supported to be rotatable about an axis of the brushless motor.
According to still another aspect of the present invention, the drive circuit of the brushless motor is mounted on a first circuit board accommodated in the motor housing and further includes a second circuit board on which an operation unit configured to control the switching element is mounted, and the first circuit board is disposed between the second circuit board and the brushless motor. The handle housing has a diameter-increased section which has a larger diameter than the grip section and is connected to the motor housing, the diameter-increased section is positioned between the grip section and the motor housing, the air flow window is provided in the diameter-increased section, and the second circuit board is accommodated in the diameter-increased section. In addition, the handle housing is divisible and the second circuit board is held by being clamped by the handle housing. The first circuit board and the second circuit board are disposed to extend in a direction substantially perpendicular to a rotation axis of the brushless motor. The air flow window is disposed between the first circuit board and the second circuit board.
According to still another aspect of the present invention, the handle housing accommodates a third circuit board on which a noise filter circuit is mounted, and the second circuit board is disposed between the first circuit board and the third circuit board in a rotating shaft direction. The handle housing has a rim part having a larger diameter than the grip section on side of the grip section opposite to the diameter-increased section and the third circuit board is accommodated in the rim part. In addition, the diameter-increased section and the rim part are formed to gradually increase in diameter away from the grip section. The third circuit board includes a filter element that protrudes from a mounting surface, and the third circuit board is inclined with respect to a rotation axis and is accommodated so that a protrusion direction of the filter element and an extension direction of the grip section cross each other. A power cord for commercial AC power supply is provided in the rim part, a switch configured to turn the brushless motor on and off by an operation thereof is provided in the grip section, and inside the electrically powered tool, in the rotational axis direction, from the rear side, the power cord, the third circuit board, the switch, the first circuit board, and the brushless motor are accommodated in this order and electrically connected in this order. In addition, a rectifier circuit configured to rectify power supplied from the power cord is provided, and the rectifier circuit is mounted on the first circuit board is electrically connected between the switch and the switching element.
According to still another aspect of the present invention, there is provided an electrically powered tool including a motor; a cylindrical motor housing in which the motor is accommodated; and a handle that is connected to one side of the motor housing in an axial direction and is rotatable about the axial direction with respect to the motor housing, wherein an intermediate member which rotates integrally with the handle and in which a rotating shaft mechanism (either a rotating shaft part or a rotating groove) is formed, and a support member which is fixed to the side of the motor housing and in which a rotating shaft mechanism (a rotating groove or a rotating shaft part) corresponding to the rotating shaft mechanism (a rotating shaft part or a rotating groove) of the intermediate member is formed is provided. The support member and the intermediate member slide around an axis, and thus the motor housing and the handle are rotatably held. In addition, the power supplied to the motor is supplied from the side of the handle to the side of the motor housing via a wiring, and a through-hole through which the wiring passes is provided at the center of the rotating shaft of the intermediate member and the support member.
According to still another aspect of the present invention, a holding section that extends to a rear side from an outer edge of the through-hole while increasing in diameter is formed on a surface on a side opposite to the support member in the intermediate member. A handle housing that forms the handle is formed such that the handle housing is able to be divided into two parts on a surface including an axis of the rotating shaft part. The handle housing is attached to the intermediate member to clamp the holding section such that the handle housing is slidable along a curved outer circumferential surface of the holding section. In addition, an outer circumferential shape of the handle in the vicinity of a part connecting to the intermediate member is substantially circular, and a vibration isolation member formed of an elastic member is disposed at a position overlapping the rotating shaft part in the axial direction between a rear surface outer peripheral edge of the support member and a front outer peripheral edge of the handle. In addition, a second vibration isolation member for preventing sliding of the intermediate member and the handle is provided in the holding section of the intermediate member. The intermediate member is produced by integral molding of a synthetic resin and the support member is able to be divided on a surface including the axial direction so that the rotating shaft part of intermediate member is able to be clamped.
According to still another aspect of the present invention, there is provided an electrically powered tool including a cylindrical motor housing in which a motor is accommodated; and a handle that is connected to one side of the motor housing in an axial direction and has a left and right division type handle housing for the motor housing. The motor is disposed in the motor housing such that a rotating shaft is positioned in a longitudinal direction of the motor housing. An inverter circuit for driving the motor is mounted between a rear end of the rotating shaft of the motor and the rotation mechanism of the support member. A control circuit which controls the inverter circuit and includes a microcomputer is mounted at the same position as the inverter circuit or mounted separately on the handle housing side. The power supplied to the motor is supplied from the side of the handle to the side of the motor housing via a wiring, and a through-hole through which the wiring passes is provided at the axial center of the intermediate member and the support member. In addition, a plurality of air flow windows are provided on the outer circumferential side of the through-hole of the intermediate member and the support member and thus flowing of air from the side of the handle into the motor housing is allowed. The inverter circuit includes a plurality of switching elements mounted on a circuit board disposed orthogonal to a rotation axis of the motor. A cooling fan for generating cooling air is provided on the rotating shaft of the motor. Air sucked from the air flow window formed in the handle according to rotation of the cooling fan is introduced into the motor housing through the air flow window formed in the intermediate member and the support member, and cools the inverter circuit and the motor, and is then discharged in a direction of the other end of the motor housing (forward direction).
According to the present invention, since a cylindrical integral motor housing is provided, it is possible to firmly fix the motor. In addition, since an air flow window (intake port) and a discharge opening (exhaust port) are provided in parts other than the motor housing, there is no need to provide a hole for sucking or exhausting air on the side surface of the motor housing, and it is possible to secure sufficient rigidity for the motor housing. In addition, since the drive circuit is cooled earlier than the motor, it is possible to effectively cool switching elements that generate heat. In addition, since the handle section rotates around the mother shaft with respect to the body part, the handle section can be appropriately rotated to a position according to the working orientation. In addition, since the vibration isolation members are provided at a plurality of positions in the vicinity of the outer circumferential part and the inner circumference, it is possible to greatly reduce vibration transmitted to the handle section from the side of the body part during working. The above and other objectives of the present invention and new aspects will be clearly understood from the following descriptions in this specification and drawings.
Embodiments of the present invention will be described below in detail with reference to the drawings. Here, in all drawings for explaining embodiments, members having the same function are denoted with the same reference numerals and repeated descriptions thereof will be omitted. In addition, in this specification, front-rear, left-right, and up-down directions are assumed to be directions shown in the drawings.
The body part 2 includes the motor housing 3 made of, for example, a metal material, a gear case 4 made of, for example, a metal material, the disk-shaped grinding stone 10 attached to a spindle 21 that is pivotally supported on the gear case 4 by a bearing 22, and a wheel guard 27 that protects a part of the grinding stone 10. The motor housing 3 is formed in a substantially cylindrical shape, and has an integral structure which has an opening on the front side and the rear side and is made of a metal. The brushless DC type motor 5 that rotates according to a drive current controlled by an inverter circuit 20 is accommodated therein. The motor 5 is accommodated therein from the front side opening of the cylindrical motor housing 3. A rotating shaft 5c of the motor 5 is rotatably held by a bearing 8b that is provided in the vicinity of a center part of the motor housing 3 and a front side bearing 8a that is held by the gear case 4. A cooling fan 6 that rotates in synchronization with the motor 5 attached coaxially with the rotating shaft 5c is provided on the side in front of the motor 5 between it and the bearing 8a, and an inverter circuit board 19 for driving the motor 5 is disposed behind the motor 5. An air flow generated by the cooling fan 6 is taken from a slit-shaped air intake hole 66 formed on the side of the handle section 60, and then caused to pass through an air flow window (to be described below in
The inverter circuit board 19 is a substantially circular double-sided board having substantially the same diameter as the external form of the motor 5 and is disposed orthogonal to the rotation axis A1. On the circuit board, six switching elements such as an insulated gate bipolar transistor (IGBT) (not shown) are mounted. A control circuit board 18 is disposed on the front side of the inverter circuit board 19 so that it is parallel to the inverter circuit board 19 and is a substantially circular both-sided board having substantially the same diameter as the motor 5, and on which a control circuit including a microcomputer (hereinafter referred to as a “microcom”) is mounted. A disk-shaped sensor magnet 12 is provided in the vicinity of a rear end of the rotating shaft 5c, and a small sensor board 13 is disposed at a predetermined interval therefrom on the side behind the sensor magnet 12. Three position detecting elements such as a Hall IC (not shown) are mounted on the side of the sensor board 13 facing the sensor magnet 12 (motor side). The sensor board 13, the control circuit board 18, and the inverter circuit board 19 that are accommodated in a cup-shaped cylindrical case 15 are accommodated from the rear side opening of the motor housing 3 into a space behind a holding section of the bearing 8b. The cylindrical case 15 is fixed by the support member 30 installed on the rear side thereof.
The handle section 60 is a part that an operator grips during working and includes the handle housing 61 of a left and right two-division type formed by molding a plastic. A power cord 11 for supplying commercial power from the outside is connected to the rear end side of the handle section 60. A rectifier circuit (not shown), a trigger switch (not shown), a noise prevention electrical component (not shown) and the like connected to the power cord 11 are accommodated inside the handle housing 61. A trigger lever 64 for controlling turning the motor 5 on and off is provided below the handle housing 61. The trigger lever 64 is used to operate a trigger switch (not shown) and the trigger switch is connected to the control circuit board 18 through a plurality of (for example, two) signal lines. AC power (for example, commercial 100 V) supplied from the power cord 11 is converted into a high voltage DC (for example, direct current 141 V) by the rectifier circuit (not shown). The rectifier circuit can be realized as a known configuration including a diode bridge and a smoothing circuit, and the rectifier circuit is disposed inside the handle section 60 or mounted on the inverter circuit board 19. An output of the rectifier circuit is transmitted to the inverter circuit board 19 through a through-hole (to be described below) at the center part of the intermediate member 50 and the support member 30 via two power lines (not shown). In addition, a signal line (not shown) for connecting a switch operated by the trigger lever 64 and the control circuit board 18 passes through the through-hole (to be described below) at the center part of the intermediate member 50 and the support member 30.
In the gear case 4, a pair of bevel gears 23 and 24 that change a direction of a rotational force of the rotating shaft 5c of the motor 5 and transmit it to the spindle 21 are disposed. The grinding stone 10 is fixed to a lower end of the spindle 21 by a pressing fitting 26 via a bracket 25. A side handle mounting hole 4a is provided in an upper part of the gear case 4, and although not shown, the same side handle mounting hole is provided in a right side surface and a left side surface of the gear case 4, and a side handle (not shown) can be attached to respective parts. In this example, since the handle section 60 is rotatable with respect to the body part 2, a side handle can be attached at a position (any of upper, right, and left positions) at which it is easy to use when the handle section 60 is rotated 90 degrees. When an operator uses the disk grinder 1, if the handle section 60 is gripped by one hand and the side handle is gripped by the other hand, and the trigger lever 64 is pulled, the motor 5 is rotated, the grinding stone 10 is pressed against a workpiece (workpiece material), and an iron material is ground. At this time, since the grinding stone 10 rotates about the axis of the spindle 21, a reaction force in the rotation direction about the spindle 21 is transmitted to the motor housing 3.
A vibration isolation member 45 as a first elastic body is fitted into a peripheral part of the rear side opening of the motor housing 3. In a cross-sectional external form in a direction perpendicular to the central axis, shapes of an end of the motor housing 3 and a facing end of the handle housing 61 are not particularly limited, but they are circular. The vibration isolation member 45 is interposed between a rear end part (here, the support member 30) of the motor housing 3 and a peripheral part (front outer peripheral edge) of a front side opening edge of the handle housing 61, and when movement of the handle housing 61 in an axial vibration direction with respect to the motor housing 3 is restricted, vibration transmitted from the side of the body part 2 to the handle section 60 is reduced. On the rear end upper side of the motor housing 3, a stopper 28 for preventing rotation of the handle housing 61 about the rotation axis A1 is provided. The stopper 28 is movable in a direction (front-rear direction) parallel to the rotation axis A1, and a position on the handle section 60 in the rotation direction is fixed when a stopper piece 28a that extends rearward in the axial direction is engaged with a fixing hole (to be described below) of the intermediate member 50. Here, the handle section 60 may be rotated about the rotation axis A1 from the state in
Next, a configuration in the vicinity of the rotation mechanism of the disk grinder 1 will be described with reference to
When a force is applied to the handle section 60 in a direction of an arrow 91 when a reaction of a force applied from a tip tool, the mounting member 62 swings in directions of arrows 92 and 93. Although this swinging is slight, a force acts in a direction in which the elastic member 69 is compressed in an upper side part, and a force acts in a direction in which the elastic member 68 is compressed in a lower part. That is, the elastic members 68 and 69 act as second vibration isolation members and swinging of the handle section 60 is prevented by the elastic members 68 and 69. In addition, a lower side of the front side cylindrical edge of the handle housing 61 comes in contact with the vibration isolation member 45 as indicated by an arrow 95. On the other hand, an upper side of the front side cylindrical edge of the handle housing 61 moves away from the vibration isolation member 45 as indicated by an arrow 94. Since the vibration isolation member 45 is disposed at a position overlapping a rotating shaft part (a connection part between the intermediate member 50 and the support member 30) in the axial direction, and a rotation support part of the handle section 60 and the vibration isolation member 45 can be disposed without being separated in a direction parallel to the rotation axis A1, it is possible to minimize an increase in the size of a main body, and swinging of the handle section 60 is effectively reduced by an action of the vibration isolation member 45. In this manner, the handle housing 61 is configured such that the intermediate member 50 is rotatably held by the rotating shaft 58 with respect to the support member 30, and vibration isolation is performed in two inside and outside places when viewed from the mounting member 62. As a result, as indicated by the arrows 94 and 95, slight vibration in the axial direction is allowed, and this vibration is damped by the vibration isolation member 45 and the elastic members 68 and 69. Therefore, as a result, it is possible to significantly damp the vibration generated from the side of the body part 2 and transmitted to the handle section 60.
When the body part 2 vibrates due to a connection structure of the handle housing 61 and the mounting member 62 described above, the handle housing 61 vibrates around a spherical center point (swing center point) of a spherical outer circumferential surface of the intermediate member 50. However, in this case, the mounting member 62 slips or slides on a hemispherical outer circumferential surface of the intermediate member 50 and thus moves along a curved surface (the inner wall surface 62b), and the elastic members 68 and 69 having an O-ring shape disposed between the intermediate member 50 and the mounting member are compressed, and thus it is possible to damp vibration. The inner wall surface 62b is formed in the same manner as a part of a sphere centered on the swing center point. In addition, a cylindrical outer circumference front edge of the mounting member 62 comes in contact with the vibration isolation member 45. The vibration isolation member 45 has substantially the same cross-sectional shape in the circumferential direction except for protrusions 46a to 46d for preventing rotation to be described below with reference to
When the handle housing 61 swings around the swing center point, a movement distance of the handle housing 61 partially varies according to a distance from the swing center point. Specifically, a partial movement distance of the handle housing 61 is larger farther from the swing center point. The vibration isolation member 45 has a shorter distance from the swing center point than that of disposition positions of the elastic members 68 and 69, and a partial movement distance of the handle housing 61 in contact therewith is relatively large. Therefore, in this example, a spring constant of the inner elastic members 68 and 69 having an O-ring shape is larger than a spring constant of the outer vibration isolation member 45. That is, the elastic members 68 and 69 having an O-ring shape are elastic bodies that are harder than the vibration isolation member 45. Therefore, during swinging when a predetermined load is applied to the handle housing 61, the elastic members 68 and 69 can exhibit a sufficient vibration isolation effect with less compression even if they are disposed further inward than the vibration isolation member 45. In addition, in such a configuration, it is possible to effectively offset vibrations with different frequency components. That is, since high frequency vibration can be offset by the elastic members 68 and 69 with a large spring constant, and low frequency vibration can be offset by the vibration isolation member 45 with a small spring constant, it is possible to reduce vibration during working.
On the outer circumferential side of a through-hole 51a of the intermediate member 50, the cone-shaped holding section 51 is formed. A collar section 51b that extends outward in the radial direction is formed in the outer circumferential part of the rear side opening edge of the holding section 51, restricts a rotatable range of the mounting member 62, and performs pressing so that the mounting member 62 does not fall off of the intermediate member 50 to the rear side. When a contact angle θ between the holding section 51 and the mounting member 62 increases to a certain extent, it is possible to improve ease of swinging and a vibration control effect in the vibration isolation member 45 during swinging. In addition, when a swing angle θ is larger, a load in the thrust direction can be effectively received. The elastic member 69 is disposed between the collar section 51b and the mounting member 62. In addition, the elastic member 68 is disposed between a disk section 50a of the intermediate member 50 and the mounting member 62. The vibration isolation member 45 can limit a sliding distance of the handle housing 61 when a load is applied in cooperative action with the outer edge part of the mounting member 62, and thus the operability can be improved. The outer circumferential shape of the mounting member 62 of the handle housing 61 is formed in a cylindrical shape. In the cylindrical part, additionally, a step part 62c whose outside protrudes to the front side and whose inside retracts to the rear side is formed, and comes in contact with the vibration isolation member 45 in an inside retracted area. The vicinity of the outer edge part of the handle housing does not come in contact with the support member 30 and the intermediate member 50, and comes in contact with only the vibration isolation member 45. In addition, on the rear side of the vibration isolation member 45, the protrusion 47c that extends in a rib shape in the axial direction is formed. Therefore, it is possible to reduce resistance when the vibration isolation member 45 as a non-rotation member and the handle housing 61 as a rotation member rotate, and it is possible to effectively control vibration when vibration is initially input. In addition, when an amplitude of vibration increases, the protrusion 47c sufficiently crushed and then comes in contact with a body part of the vibration isolation member 45. Therefore, it is possible to realize a damping mechanism having high rigidity and a strong vibration control effect. Here, degrees of initial damping characteristics of the handle housing 61 and a shape of the outer circumferential surface may be optimally set according to required damping characteristics, a rigidity, and the like.
The vibration isolation member 45 is formed in a ring shape, and the support member 30 is screwed to the motor housing 3, and is then fitted into a step part 40 formed in the vicinity of the rear surface outer peripheral edge of the support member 30. The vibration isolation member 45 is made of an elastic body having a strong vibration control effect, for example, a rubber body, and four parts on the inner circumferential side are partially engaged with the screw holes 33a to 33d, and thus the protrusions 46a to 46d that prevent rotation of the vibration isolation member 45 about the rotation axis A1 are provided. Since the protrusions 46a to 46d are fitted into dent parts (escape groove parts of the support member 30 provided behind the screw holes 33a to 33d) for applying a tool such as a driver to the screw holes 33a to 33d, the vibration isolation member 45 does not rotate relative to the support member 30. A cross-sectional shape of the surface including the rotation axis A1 of the vibration isolation member 45 is arbitrary. However, in order to effectively reduce vibration due to a compression load in the axial direction, the flange-like protrusions 47a and 47b which are continuous in the axial direction are formed on the outer circumferential surface.
In the intermediate member 50, a plurality of air flow windows 55, 56a, 56b, and 57 (here, 56a is not shown in
Next, a circuit configuration of a drive control system of the motor 5 will be described with reference to
The bridge diode 72 performs full-wave rectification of an alternating current input from a commercial AC power supply 100 and outputs it to the smoothing circuit 73. The smoothing circuit 73 smooths a pulsating flow included in the current rectified by the power supply circuit 71 such that it becomes close to a direct current and outputs it to the inverter circuit 80. The smoothing circuit 73 includes an electrolytic capacitor 74a, a film capacitor 74b, and a discharging resistor 75. The inverter circuit 80 includes the six switching elements Q1 to Q6 connected in the form of a 3-phase bridge. Here, insulated gate bipolar transistors (IGBTs) are used as the switching elements Q1 to Q6, but metal oxide semiconductor field effect transistors (MOSFETs) may also be used.
The rotor 5a having a permanent magnet rotates inside the stator 5b of the motor 5. The sensor magnet 12 for position detection is connected to the rotating shaft 5c of the rotor 5a. When the position of the sensor magnet 12 is detected by a rotating position detecting element 77 such as a Hall IC, the operation unit 98 detects a rotation position of the motor 5. The rotating position detecting element 77 is mounted on the sensor board 13 (refer to
The operation unit 98 is a control device for controlling on and off and rotation of a motor and mainly includes a microcomputer (not shown). The operation unit 98 is mounted on the control circuit board 18 and controls a current flowing time and a driving voltage for U, V, and W coils in order to rotate the motor 5 based on a start signal input according to an operation of a trigger switch 65. Although not shown here, a speed change dial for setting a rotational speed of the motor 5 is provided, and the microcomputer may adjust a speed to match a speed set by the speed change dial. The output of the operation unit 98 is connected to gates of the six switching elements Q1 to Q6 of the inverter circuit 80 and supplies drive signals H1 to H6 for turning the switching elements Q1 to Q6 on and off.
Emitters or collectors of the six switching elements Q1 to Q6 of the inverter circuit 80 are connected to star-connected U-phase, V-phase, and W-phase coils. The switching elements Q1 to Q6 perform a switching operation based on the drive signals H1 to H6 input from the operation unit 98, and supply a direct current voltage supplied from the commercial AC power supply 100 through the power supply circuit 71 and the smoothing circuit 73 as 3-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw to the motor 5. A magnitude of the current supplied to the motor 5 is detected by the operation unit 98 when a voltage value at both ends of a current detection resistor 76 connected between the smoothing circuit 73 and the inverter circuit 80 is detected.
The low voltage power supply circuit 90 is a low voltage constant power supply circuit which is directly connected to the output side of the bridge diode 72 and supplies a direct current of a stabilized reference voltage (low voltage) to the operation unit 98 constituted by a microcomputer or the like. The low voltage power supply circuit 90 is a known power supply circuit including a diode, a smoothing capacitor, an IPD circuit, a regulator, and the like. Although not shown in
As above, while an example of the disk grinder having substantially a cylindrical motor housing and the handle section that extends to the rear side has been described in Example 1, the present invention is not limited to a disk grinder, and it can be similarly applied to a rotation mechanism of an arbitrary electrically powered tool including a body part including a motor and a handle section that extends from the body part to the rear side or the lateral side. In addition, in the above example, the motor housing 3, the support member 30, the intermediate member 50, and the handle section 60 are disposed in this order from the front to the rear side, but the present invention is not limited to this order. The present invention may be an electrically powered tool having a structure in which the handle section is rotatably supported by the support member 30 and is supported by the intermediate member 50 in a swinging manner. For example, positions of the support member 30 and the intermediate member 50 may be reversed. Here, while the electrically powered tool in which the rotation axis of the motor 5 and the rotation axis of the handle section 60 coincide with each other has been exemplified in the above example, an electrically powered tool in which such rotation axes do not coincide with each other may be used.
Next, a second example in which disposition of a circuit board in an electrically powered tool is improved will be described.
The body part 102 is constituted by a part accommodated in the cylindrical motor housing 200 and a power transmission mechanism connected to the front side thereof. The brushless type motor 105 is accommodated inside the motor housing 200. The motor 105 includes a rotor 105a having a permanent magnet that is disposed on the inner circumferential side and a stator 105b having a coil on the outer circumferential side, and is accommodated inside from the front side opening of the motor housing 200. A rotating shaft 105c of the motor 105 is rotatably held by a bearing 108b provided in the vicinity of the center part of the motor housing 200 and a front side bearing 108a held by a gear case 104. The power transmission mechanism has substantially the same configuration as that of the first example except for sizes and shapes, and includes the disk-shaped grinding stone 10 attached to a spindle 121 that is pivotally supported on the gear case 104 by a bearing 122 and a wheel guard 127. A pair of bevel gears 123 and 124 are disposed in the gear case 104, and change a direction of a rotational force of the rotating shaft 105c of the motor 105 and transmit it to the spindle 121. The grinding stone 10 is fixed to a lower end of the spindle 121 by a pressing fitting 126 via a bracket 125. A side handle mounting hole 104a is provided at the upper part of the gear case 104, and a same side handle mounting hole (not shown) is provided in a right side surface and a left side surface of the gear case 104.
An inverter circuit part 230 is inserted from the rear side opening of the motor housing 200, and the opening is then covered with a support member 130 and an intermediate member 150. The support member 130 combines a plurality of separate members and fixes outer circumferential parts thereof with a rubber damper 158 which is a first elastic body. When left and right divided pieces of the support member 130 are combined, a swing supporting section 151 of the intermediate member 150 is inserted into the vicinity of the center of the support member 130. In addition, a washer 159 is fitted into the rear side of the rubber damper 158. A circuit board 241 of the inverter circuit part 230 is a substantially circular multi-layer board having a slightly larger diameter than the external form of the motor 105 and its surface is disposed orthogonal to the rotation axis A1. In this manner, since the circuit board 241 is disposed orthogonal to the rotation axis A1, it is possible to shorten the entire length (size in a front-rear direction) of the electrically powered tool. Switching elements (to be described below) such as six insulated gate bipolar transistors (IGBTs) are mounted on the circuit board 241. The circuit board 241 on which switching elements are mounted that is accommodated inside a cylindrical case 231 having a container shape is disposed in the motor housing 200. Since the motor 105 used in Example 2 is larger and has a higher output than the motor 5 used in Example 1, for an inverter circuit driving it, a large semiconductor element (IGBT) that can switch a large current is used, and the size of the circuit board 241 necessary for mounting them increases. Therefore, the diameter of the motor housing 200 in a part in which the inverter circuit part 230 is accommodated is formed to be slightly thicker than a part in which the motor 105 is accommodated. A small annular sensor board 117 is mounted between the bearing 108b and the stator 105b when viewed in the direction of the rotation axis A1. The sensor board 117 has an annular board part and three rotating position detecting elements 114 (to be described below) such as a Hall IC are mounted at intervals of 60 degrees on the side facing the stator 105b. The rotating position detecting element 114 (to be described below) detects a magnetic field generated by the rotor 105a and thus detects a position of the rotor 105a. An attachment part (not shown) that extends outward in the radial direction from two opposing parts of a board part of the sensor board 117 is provided. The sensor board 117 is screwed to the motor housing 200 using a screw hole provided in the attachment part and a screw boss (not shown) formed in the part of a rib 211.
A cooling fan 106 is provided on the side in front of the motor 105 between it and the bearing 108a. The cooling fan 106 is a centrifugal fan and sucks air on the side of the motor 105 and discharges it outward in the radial direction. According to an air flow generated by the cooling fan 106, an air flow is generated in a direction indicated by a black arrow in the drawing. First, outside air is taken from a slit-shaped air intake hole 165 formed on the side of the handle section 160, and then caused to pass through a through-hole and an air flow window (to be described below in
The air flow passes between the rotor 105a and the stator 105b, and between the stator 105b and an inner wall part of the motor housing 200, is sucked from the vicinity of the axial center of the cooling fan 106, flows outward in the radial direction of the cooling fan 106, and passes through an air hole formed on the outer circumferential side of a bearing holder 107. Some of cooling air discharged from the bearing holder 107 is discharged to the outside through an exhaust port (not shown) formed in the gear case 104 as indicated by an arrow 109a, and the remaining air is discharged to the outside through an exhaust port (not shown) in the vicinity of the lower side of the bearing holder 107 as indicated by an arrow 109b. As described above, outside air is sucked by the handle section 160 using the cooling fan 106 and the air flows from the rear side to the front side of the motor housing 200. In this case, since the inverter circuit part 230 with the largest amount of heat generated is disposed on a windward side in cooling air in which air is most likely to cool, which is a part ahead of the motor 105 (the bearing 108b), electronic elements mounted on the inverter circuit part 230, particularly, semiconductor switching elements can be efficiently cooled. In addition, when the cylindrical integral motor housing 200 is formed, it is possible to firmly pivotally support the motor 105 compared to supporting by a housing that can be divided, and sufficient rigidity can be secured.
The handle section 160 is a part that an operator grips during working, and a case body thereof includes a handle housing 161 of a left and right two-division type formed by molding a plastic, and is fixed by four screws 166a to 166d. The handle section 160 can be rotated 90 degrees to one side and 90 degrees to the other side about the rotation axis A1 from the state in
The support member 130 and the intermediate member 150 that are in a relatively non-rotatable state are held on the side of the motor housing 200, the handle housing 161 is relatively rotatable with respect to the intermediate member 150, and thus the rotation mechanism of the handle section 160 is realized. That is, the intermediate member 150 and the handle housing 161 constitute the rotation mechanism. In addition, the hollow and cone-shaped (bell-shaped) swing supporting section 151 is formed on the side in front of the intermediate member 150 and its bell-shaped outer circumferential surface (curved surface part) is held by the support member 130. Therefore, the support member 130 and the intermediate member 150 are disposed to realize a vibration control mechanism of the handle section 160, the intermediate member 150 is slightly swingable with respect to the support member 130, and an elastic body to be described below is disposed within the swing range. The principle of vibration control, that is, movement of the swing supporting section 151 and the intermediate member 150, is the same as movement of the holding section 51 of the mounting member 62 of Example 1 (refer to
A control circuit part 260 is accommodated behind the intermediate member 150. The control circuit part 260 is sandwiched by the handle housing 161 such that it extends in a direction perpendicular to the rotation axis A1. In the control circuit part 260, a control circuit board 262 (to be described below) as a second circuit board is accommodated in a shallow case having a container shape. A control circuit of the motor 105 including a microcomputer is mounted on the control circuit board 262. When an inverter circuit and a control circuit are divided into separate boards (a first circuit board and a second circuit board), it is possible to minimize an increase in the size of a circuit board when all circuits are concentrated on a single board and it is possible to reduce the size of the tool. The control circuit part 260 is provided slightly rearward from a position at which the air intake hole 165 is formed when viewed in a direction of the rotation axis A1, and the air intake hole 165 as an air flow window is disposed between the circuit board 241 and the control circuit part 260. Since an amount of heat generated by an electronic component mounted on the control circuit part 260 is not so large, the priority for cooling with cooling air is lower than that for the circuit board 241 on which an inverter circuit is mounted. When the air intake hole 165 is disposed between the circuit board 241 and the control circuit part 260, cooling air flowing from the air intake hole 165 first hits the circuit board 241 and objects mounted thereon among the electronic elements and the circuit board 241 (inverter circuit) can be preferentially cooled. In this manner, as long as the circuit board 241 (board on which an inverter circuit is mounted) can be preferentially cooled, a position at which the air intake hole 165 is formed may be freely set in the handle section 160.
The power cord 11 for commercial AC power supply is connected to a rear end side of the handle section 160, and at position close to the drawn power cord 11, a filter circuit part 270 on which an electrical component for noise reduction is mounted is provided. The configuration of the filter circuit part 270 is realized in the same manner as in the configuration of the control circuit part 260 and is formed by accommodating a third circuit board on which a filter circuit such as a choke coil 272, a discharge resistor, a film capacitor, a varistor, and a pattern fuse is mounted in a rectangular parallelepiped housing case (not shown) having an opening on one side, pouring a curable resin into the housing case and performing curing. Here, some of parts such as a choke coil are exposed to the outside from the curable resin, but almost all of the other parts are covered with the curable resin.
The filter circuit part 270 is bent forward and then disposed so that a center surface C1 parallel to the third circuit board has an angle θ1 with respect to the vertical surface. The opening of the housing case in this case is on the front side and the choke coil 272 protrudes from a part of the opening to the front side. That is, the third circuit board of the filter circuit part 270 is inclined with respect to the rotation axis A1 and accommodated so that a protrusion direction of the choke coil 272 as a filter element and an extension direction of the grip section cross each other. The reason why the filter circuit part 270 that is inclined to the front side is disposed in this manner is that, when the center surface C1 is made to be oblique, the shape on the rear side relative to a grip part (grip section) of the handle section 160 has a shape that extends obliquely downward. When a grip section 162b is formed to have a small diameter in order to secure operability, an internal space is easily restricted due to formation of screw bosses. However, when the third circuit board is obliquely accommodated and a protrusion direction of the filter element is adjusted, it is easy to accommodate the third circuit board in a rim part adjacent to the grip section. In addition, according to this structure, in the shape, an oblique line 280 shape is secured, and when an operator grips the grip section, a rim part (protrusion part) 162c for accommodating the filter circuit part 270 is unlikely to hit a finger, and the operator can smoothly grip it. In addition, when the filter circuit part 270 is tilted to the front side, it is possible to prevent the choke coil 272 from interfering with a screw boss 167b for a screw 166b. In addition, since a space for leading the power cord 11 can be secured on the rear side of the filter circuit part 270, this is advantageous in terms of routing of the power cord 11.
A switch unit 170 for controlling turning the motor 105 on and off is disposed at the center part of the handle housing 161. The switch unit 170 includes a trigger switch 174 and a swing type trigger lever 176 disposed therebelow. The trigger lever 176 is an operation body for moving a plunger 178 of the trigger switch 174 and has one side that is pivotally supported by a rear swing shaft 177. A spring 175 that biases the trigger lever 176 in a predetermined direction is provided between the trigger switch 174 and the trigger lever 176. The operator can operate the trigger switch 174 by gripping the handle section 160. The trigger switch 174 can turn a plurality of (for example, two) power lines for commercial power supply on or off at the same time, and a power line (not shown) on the output side is transmitted to the inverter circuit part 230 through a through-hole (to be described below) of the center part of the intermediate member 150 and the support member 130. In addition, six signal lines (not shown) for transmitting a gate signal from the control circuit part 260 to a semiconductor switching element (to be described below) and other signal lines (not shown) pass through the through-hole (to be described below) of the center part of the intermediate member 150 and the support member 130.
As described above, in Example 2, from the rear side in a direction of the rotating shaft 105c, the power cord 11, a third circuit board 271, the switch unit 170, the second circuit board (the control circuit board 262), the first circuit board (the circuit board 241), and the motor 105 are accommodated in this order, and also electrically connected in this order. Therefore, since electrical elements can be disposed in the order of circuit configurations, the wiring can be shortened and simplified, costs can be reduced, and an increase in the size of the tool due to unnecessary wiring can be minimized.
Next, internal structures of the motor housing 200 and the inverter circuit part 230 accommodated on the rear side thereof will be described with reference to the exploded view in
The inverter circuit part 230 is formed by an IGBT circuit element group 240 in which electronic components are mounted on the circuit board 241 and the cylindrical case 231 a container shape for accommodating them. The cylindrical case 231 blocks one side (front side) of a substantially cylindrical outer circumferential surface 233 with a bottom surface 232 and the IGBT circuit element group 240 is accommodated in its internal space. By disposing a switching element for driving a motor in the cylindrical case 231, it can be disposed on the side of the motor 105 relative to the control circuit board 262. Therefore, the wiring from the circuit board 241 to the motor 105 can be shortened, assembling becomes easier, a space for unnecessary wiring installed is accordingly reduced, and thus an increase in the size of the electrically powered tool can be minimized. The cylindrical case 231 is disposed such that the opening side is the side of the handle section 160 (rearward), that is, an air intake side, and the bottom surface 232 as a closed surface is disposed to face the side of the motor 105 (forward). When the inverter circuit part 230 is accommodated inside the circuit board housing section 204 on the rear side of the motor housing 200, the support member 130 is installed from the rear side thereof. The support member 130 supports the intermediate member 150 (refer to
On the rear side opening of the motor housing 200, screw bosses 206a to 206d in which a hole through which a screw passes is formed are formed. Semi-cylindrical pressing members 133a to 133d that extend to the front side are formed in a screw passing area of the support member 130. The pressing members 133a to 133d press a part of the rear side opening edge of the cylindrical case 231 at a position at which it abuts the cylindrical outer circumferential surface of the screw bosses 206a to 206d on the side of the motor housing 200, and thus the cylindrical case 231 is stably fixed to the inside of the motor housing 200. On outer side in the radial direction from the through-holes 132a and 132b, according to a network form of a plurality of ribs 136a and 136b, a plurality of air flow windows 137a and 137b for allowing air to flow in the axial direction are formed. In addition, a plurality of cylindrical ribs 135a to 135f which form a cylindrical outer circumferential surface from the vicinity of the outer edge of the right side 131a and the left side 131b to the rear side are formed. The cylindrical ribs 135a to 135f serve as holding sections for fitting the rubber damper 158 (to be described below in
In the outer circumferential shape of the cylindrical case 231, dents, rail parts or the like that are continuous in the axial direction are formed along the inner shape of the circuit board housing section 204 of the motor housing 200. First, rotation preventing holding sections 234a to 234d recessed to avoid the cylindrical screw bosses 206a to 206d of the motor housing 200 are formed. In addition, rail parts 237a and 237b that extend in a direction of the rotation axis A1 are formed to be fitted to grooves 207a and 207b formed in the inner wall part of the motor housing 200. In both left and right side parts of the cylindrical case 231, incision parts 236a and 236b for securing an air passage through which cooling air that flows from the rear side of the support member 130 in the axial direction hits the vicinity of the IGBT and flows toward the motor 105 are formed.
A through-hole 151a is formed at the center of the intermediate member 150, and a size of the through-hole 151a is set to be sufficiently large to allow two power lines (not shown) and a signal line from a microcomputer to the inverter circuit part 230 to pass therethrough. In addition, a part of the through-hole 151a is also used for allowing cooling air to pass therethrough. A mesh shape is formed on the outer circumferential side of the through-hole 151a so that air can pass through in the axial direction, and a plurality of ribs 155 are formed in a network shape, and thus a plurality of air flow windows 156 are formed. These air flow windows 156 are formed at positions corresponding to the air flow windows 137a and 137b formed in the support member 130 and thus cooling air easily flows from the rear side of the intermediate member 150 toward the front side of the support member 130 through the air flow window 156 and the air flow windows 137a and 137b (refer to
The rubber damper 158 is a first elastic body fitted to the outer circumferential side of the cylindrical ribs 135a to 135f of the support member 130, and holds the right side 131a and the left side 131b on the support member 130. The rubber damper 158 is compressed when the handle housing 161 swings in a direction (in the case of polishing, the downward direction, and in the case of cutting, the left-right direction) in which the operation of the handle housing progresses, and when movement of the handle housing 161 with respect to the motor housing 200 in the axial vibration direction is restricted, vibration transmitted from the side of the body part 102 to the handle section 160 during working can be effectively offset. Here, the rubber damper 158 is not limited to a damper made of rubber, and can be realized by a member or a mechanism that can obtain a vibration control effect with an elastic body made of a silicone elastic resin or other materials. Although the rubber damper 158 is shown on the rear side of the intermediate member 150 in
The control circuit part 260 is accommodated in an internal space of the handle housing 161 on the rear side of the intermediate member 150. The control circuit part 260 is obtained by accommodating the control circuit board 262 on which electronic elements (not shown) such as a microcomputer and a constant voltage circuit are mounted in a container-shaped housing case 261 having a substantially rectangular parallelepiped and an opening (in the drawing, not shown) on one side. A liquid curable resin is poured into the housing case 261 and cured while the control circuit board 262 and all electronic elements mounted thereon are covered, and thus the mounted microcomputer and electronic elements are not exposed to dust or water. The housing case 261 is clamped by the handle housing 161 configured as a left and right division type and held in the handle section 160.
The diameter-increased section 162a has a front side on which a circular opening is formed and an inner circumferential surface in which the rotating groove 163 (163a and 163b) are formed. On the rear side of the rotating groove 163, a clamping groove 164 for clamping the housing case 261 (refer to
Next, the internal structure of the motor housing 200 in
The rear side of the rib 211 is a space for accommodating the inverter circuit part 230, and the grooves 207a and 207b and a rail part 208 are formed on the inner circumferential surface of the circuit board housing section 204. A rear end position of the cylindrical bearing holder 210 is set to be on the side to the rear of a rear end position of the rib 211, and a rear end opening surface of the bearing holder 210 is fitted to a cylindrical convex part formed in the vicinity of the center of the bottom surface 232 of the cylindrical case 231 of the inverter circuit part 230. As a result, the circuit board 241 is accommodated in the cylindrical case 231 having a container shape and thus assembling become easier, and since the opening of the cylindrical case 231 faces the side of the intake port, air from the intake port easily hits the board (air easily enters the case), and a cooling effect is improved. In addition, on the bottom surface 232 and an inlet part of the air flow window 212, a predetermined interval is provided in the axial direction. Therefore, cooling air flowing from the side upstream from the air flow window 212 can flow not only in the axial direction but also in the radial direction. The motor 105 is inserted from the front side opening of the motor housing 200 and grooves 209a and 209b for holding the stator 105b of the motor 105 are formed. Rail parts formed on the outer surface part of the stator 105b of the motor 105 are engaged with groove parts of the grooves 209a and 209b and thus the motor 105 is held.
The bridge diode 242 is provided in an upper part of the cylindrical case 231. The bridge diode 242 is a combination of four diodes contained in one package and the metal heat dissipation plate 242a is attached to a rear surface of the bridge diode 242. The bridge diode 242 is disposed such that a planar direction of the heat dissipation plate 242a extends in the left-right and front-rear directions, that is, parallel to a direction in which cooling air flows. The two capacitors 243 and 244 are mounted as parts below the bridge diode 242. The capacitors 243 and 244 constitute a rectifier circuit together with the bridge diode 242, and a large capacity electrolytic capacitor is used here. Although the capacitor 244 of the circuit board 241 and right side parts of the semiconductor switching elements Q1 and Q4 are not shown here, a terminal for soldering a power line connected from the trigger switch 174, a terminal for soldering a power line that transmits U-phase, V-phase, and W-phase drive power to the motor 105, and a connector terminal for connecting a wire harness for connection to the control circuit part 260 are provided. The power line connected to the motor 105 is wired through a space formed between dents 238a and 238b for leading the power line on the outer circumferential part and the inner wall surface of the motor housing 200.
The trigger switch 174 is a double-pole switch that can turn the two contact points 174a and 174b on or off at the same time. In this example, the trigger switch 174 is provided on the upstream side of the bridge diode 242 and thus supply of power to the inverter circuit part 230 mounted on the circuit board 241 can be directly controlled. Branch lines 269a and 269b for supplying power to the control circuit board 262 are connected from the upstream side of the trigger switch 174, and these are connected to a low voltage power supply circuit 263. An operation unit 298 and the low voltage power supply circuit 263 for supplying a predetermined constant voltage thereto are provided on the control circuit board 262. The low voltage power supply circuit 263 includes a bridge diode 267, an electrolytic capacitor 268, an IPD circuit 264, a capacitor 265, and a three-terminal regulator(Reg) 266.
The semiconductor switching elements Q1 to Q6 including six IGBTs are mounted on the inverter circuit part 230 and constitute a drive circuit for driving a motor. The capacitors 243 and 244 are provided in parallel between the semiconductor switching elements Q1 to Q6 and the bridge diode 242. A shunt resistor 248 is mounted within the circuit to the semiconductor switching elements Q1 to Q6, and a voltage thereof is monitored by the operation unit 298. The gate signals H1 to H6 of the semiconductor switching elements Q1 to Q6 are supplied by the operation unit 298. The output of the inverter circuit part 230 is connected to U-phase, V-phase, and W-phase coils of the motor 105.
The operation unit 298 is a control device for controlling on and off and rotation of a motor and includes a microcomputer (not shown). The operation unit 298 controls a current flowing time for U, V, and W coils and a driving voltage for rotating the motor 105 based on a start signal (obtained by an electronic switch (not shown)) input according to an operation of the trigger switch 174. An output of the operation unit 298 is connected to gates of the six switching elements Q1 to Q6 of the inverter circuit part 230. Collectors or emitters of the six switching elements Q1 to Q6 of the inverter circuit part 230 are connected to star-connected U-phase, V-phase, and W-phase coils. Regarding a rotational speed of the motor 105, the rotating position detecting element 114 such as a Hall IC detects a change in the magnetic pole of the rotor 105a having a permanent magnet, and thus the operation unit 298 detects a rotation position of the motor 105.
As above, according to Example 2, in order to increase the cooling efficiency for the inverter circuit part 230, when the inverter circuit part 230 is disposed behind the motor 105, cooling air generated by the cooling fan 106 is efficiently applied in the structure. In addition, since an electrically powered tool with high input power needs to have a semiconductor switching element having a large size and a capacitor with a large capacity, there is a problem that it is difficult to mount them collectively on one circuit board spatially. This problem is solved by separating the circuit board 241 for an inverter circuit and the control circuit board 262 for a control circuit. In addition, the circuit board 241 for an inverter circuit is mounted inside the motor housing 200 and the control circuit board 262 is mounted inside the handle housing 161 separately, and thus an increase in the size of the electrically powered tool can be minimized. In addition, the control circuit board 262 and the circuit board 241 for an inverter circuit are connected through the through-hole 151a at the center of the intermediate member 150 disposed between the body part 102 and the handle section 160. However, the circuit board 241 for an inverter circuit is not directly fixed to the rear side of the stator 105b of the motor 105, and they are disposed in separate spaces separated to the front side and the rear side in the axial direction by the bearing holder 210 and the rib 211 within the motor housing 200. Therefore, it is possible to reduce the number of wirings necessary for connection to the motor 105 during production. In addition, in the structure of the second example, the circuit board 241 on which the semiconductor switching elements Q1 to Q6 and the like are mounted is disposed in the cylindrical case 231 and a liquid urethane is then injected and cured and thus welded parts of the semiconductor switching elements Q1 to Q6 and the circuit board 241 can be covered at once. Therefore, it is possible to improve mass productivity and perform production at low cost.
A curable resin is poured into the circuit board 241A in the cylindrical case 231 and terminal parts of elements to be soldered are completely covered. On the other hand, for terminal parts of the semiconductor switching elements Q1 to Q6 (in the drawing, only Q3 and Q6 are shown) to be soldered to the IGBT board 321, it is not possible to apply a fixing method of pouring in a curable resin, and curing. Therefore, an assembling worker manually applies a silicon resin one by one. In the shape of the rib 211A at the positions at which the semiconductor switching elements Q1 to Q6 are mounted, a recess is formed in order to prevent the semiconductor switching elements Q1 to Q6 from being in contact therewith. On a surface (surface on the front side) opposite from the side on which the semiconductor switching elements Q1 to Q6 of the IGBT board 321 are mounted, at positions facing a rotational locus of the permanent magnet of the rotor 105a, the three rotating position detecting elements 114A are mounted. The switching elements Q1 to Q6 are disposed in a space (around the bearing 108b) used as an air passage and thus mounted on the circuit board 241A. Therefore, it is not necessary to increase the size of the motor housing 200A in order to mount switching elements on separate boards, and an increase in the size can be minimized and it is possible to secure an accommodation space for the cylindrical case 231. In addition, according to this example, since cooling air hits the bridge diode 242 earlier than the switching elements, the bridge diode 242 can be preferentially cooled. In addition, in Example 3, since circuits are divided into four circuit boards, and additionally, these are disposed in the electrically powered tool so that they extend in the up-down direction, an increase in the size of the circuit board can be minimized, and an increase in the size of the electrically powered tool in the front-rear direction can be minimized, compared to when all circuits are integrated on one circuit board.
The control circuit part 260 is held at a position slightly moved rearward and downward from the disposition of Example 2, but the shape of the control circuit part 260 and the internal circuit configuration are the same as those in Example 2. A reactor 347 is disposed above the control circuit part 260. The reactor 347 is used for minimizing harmonics generated by a switching operation in the inverter circuit and is electrically connected between the capacitors 343 to 345 and a power supply input unit. While it is necessary to increase the size of the reactor 347 as a countermeasure for harmonics, since the electrically powered tool has a higher high output, the reactor 347 is disposed in a certain space between the switch unit 170 (power supply input side) and the capacitors 343 to 345, and thus the wiring from the capacitors 343 to 345 to the reactor 347 can be shortened, and a space for disposing the large size reactor 347 can be secured. The switch unit 170 accommodated inside the handle section 360 is the same as that used in Example 2 and Example 3. Here, the position of the screw boss 367d is shifted, and thus the stopper mechanism 128 (refer to
According to Example 4, since it is not necessary to mount the capacitors 343 and 344 with a large capacity on the circuit board 241B of the inverter circuit part 230B, installation of the switching elements Q1 to Q6 to be mounted on the circuit board 241B becomes easier and it is possible to further increase the size of the IGBT used as a switching element. In addition, since it is possible to prevent the capacitors 343 and 344 from being mounted in the vicinity of the switching elements Q1 to Q6 and the bridge diode 242 with a large amount of heat generated, it is possible to prolong the lifespan of the capacitors 343 and 344 and cooling air can easily hit the switching elements Q1 to Q6 and the bridge diode 242. Here, in order to improve assembling performance, the three capacitors 343 to 345 may be mounted on a newly provided circuit board.
While the present invention has been described above based on Examples 1 to 4, the present invention is not limited to the above examples, and various modifications can be made without departing from the spirit and scope of the invention. For example, while an example of a disk grinder including a substantially cylindrical motor housing and a handle section that extends to the rear side has been described in the above examples, the electrically powered tool of the present invention is not limited to a disk grinder, and it can be similarly applied to an arbitrary electrically powered tool including a body part including a motor and a handle section that extends from the body part to the rear side or the lateral side.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-130338 | Jun 2016 | JP | national |
| 2017-013050 | Jan 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/019711 | 5/26/2017 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/003369 | 1/4/2018 | WO | A |
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| 20190358769 A1 | Nov 2019 | US |
