JP2015013369A - Portable electric cutter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently cool a circuit board for motor driving by securing an arrangement space for the circuit board without largely changing a shape of a housing in which the motor is accommodated and without spoiling operability.SOLUTION: A portable electric cutter includes: a housing 2 in which a motor 1 is accommodated; a saw blade driven to rotate by the motor; a base 6 coupled to the housing 2 and having a bottom surface slidable on material to be cut; a fan 7 driven to rotate by the motor; a driving circuit for switching power supplied to the motor; and a control circuit for controlling the driving circuit. A circuit board 60 on which the driving circuit, the control circuit or the like are mounted is arranged in the housing located between a handle 3 of the housing 2 and the base 6 and in a passage of fan wind to be cooled.

Description

  The present invention relates to a portable electric cutting machine such as a portable electric circular saw, and more particularly to a cooling structure of a circuit board for driving a motor.

  Recently, the use of a brushless motor in a portable electric circular saw has been studied for the purpose of reducing the size and weight and increasing the efficiency. In general, a portable electric circular saw includes a housing having a handle at the top, a circular saw blade that is driven to rotate by a motor housed in the housing, and a base that is connected to the housing and can slide on a material to be cut. However, particularly when a brushless motor is employed as the motor, there is a problem in securing the arrangement space of the circuit board for driving the brushless motor and the heat dissipation countermeasure.

  The following Patent Document 1 is an example of an electric tool in which a brushless motor that rotationally drives a polishing grindstone is housed in a cylindrical housing that is gripped by hand, and the back of the motor opposite to the front end side of the housing provided with the grinding grindstone The motor drive circuit is divided into a plurality of substrates and stored in the housing.

JP 2010-173042 A

  By the way, the portable electric circular saw does not have a relatively long cylindrical housing as in the above-mentioned Patent Document 1, and uses a very high output motor as a motor. Therefore, it is necessary to devise a method for securing the space for arranging the circuit board for driving the motor and for cooling the circuit board. Moreover, it is necessary to have a housing shape that does not hinder the operability of the portable electric circular saw.

  The present invention has been made in view of such a situation, and an object of the present invention is to secure an arrangement space for a circuit board for driving a motor without deteriorating the operability without largely changing the shape of a housing for housing the motor. Another object is to provide a portable electric cutting machine that can cool the circuit board satisfactorily.

An aspect of the present invention is a portable electric cutting machine including a brushless motor,
A housing having a motor housing for housing the motor;
A saw blade that is rotationally driven by the motor;
A base connected to the housing, having a bottom surface capable of sliding on a material to be cut, and having an opening capable of projecting the saw blade downward from the bottom surface;
A fan that is driven to rotate by the motor and that cools the motor by fan air generated during rotation;
A drive circuit including a switching element for switching power supplied to the motor;
A control circuit for controlling the drive circuit;
A circuit board on which either or both of the drive circuit and the control circuit are mounted;
Rotation state detecting means for generating a signal in the control circuit according to the rotation position of the motor,
The rotation state detection means is provided in the motor housing portion,
The housing has a plurality of wind windows on the anti-saw blade side,
The motor is disposed in the fan wind passage between one of the wind windows and the fan;
At least a part of the circuit board is disposed in the fan air passage between the other one of the wind windows and the fan, and the circuit board extends in parallel with the rotation axis of the motor at a side position of the motor. It is arranged so that it may be arranged.

  The said aspect WHEREIN: The said circuit board is good to be arrange | positioned rather than the said motor at the cutting direction back side.

  In the above aspect, the circuit board may be disposed substantially orthogonal to the upper surface of the base in a state where the motor is close to the base.

  In the above aspect, a handle and a saw cover may be provided on the housing, and a lever for adjusting a protruding amount of the saw blade from the bottom surface of the base may be provided between the handle and the saw cover.

  In the above aspect, the rotational state detecting means includes a sensor magnet rotated by the motor, a sensor substrate disposed so as to face and close to the sensor magnet, and a rotational position detecting element disposed on the sensor substrate. Good.

  In the above aspect, the sensor board and the circuit board may be electrically connected.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, the circuit board for driving the motor is disposed in the housing located between the handle and the base of the housing that houses the motor and in the fan-like passage. Without greatly changing the shape, it is possible to secure an arrangement space for the circuit board without impairing the operability, and to cool the circuit board satisfactorily.

BRIEF DESCRIPTION OF THE DRAWINGS It is 1st Embodiment of the portable electric cutting machine which concerns on this invention, Comprising: The top view which made the principal part the cross section. FIG. The front view. The rear view. The same side view. The top view which made the principal part explaining the air path in 1st Embodiment the cross section. The top view which made it the 2nd Embodiment of this invention, and made the principal part a cross section. FIG. The rear view which abbreviate | omitted the circular saw blade similarly. The same side view. The top view which made the cross section the principal part explaining the air path in 2nd Embodiment. The top view which made it the 3rd Embodiment of this invention, and made the principal part a cross section. FIG. The rear view which abbreviate | omitted the circular saw blade similarly. The same side view. The top view which made the principal part explaining the air path in 3rd Embodiment the cross section. It is a circuit diagram which shows one example of the drive circuit and control circuit for brushless motors in each embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  A first embodiment of a portable electric cutting machine according to the present invention will be described with reference to FIGS. 1 to 6 and FIG. The first embodiment is a portable electric circular saw, which is provided with a housing 2 that houses a brushless motor 1 and a housing 2 that is integrated or connected as a separate member, and controls the driving of the motor 1 shown in FIG. A handle 3 having a switch 3a, a circular saw blade 4 that is driven to rotate by the motor 1, and a shape that covers the upper half of the outer periphery of the circular saw blade 4 and is attached to the housing 2, A saw cover 5 that houses a part of the side surface on the motor 1 side, and a bottom surface 6a that is connected to the housing 2 via the saw cover 5 and that can slide on a material to be cut such as wood, and the saw blade 5 from the bottom surface 6a. A base 6 having an opening that can project downward, and a centrifugal fan 7 that is fixed to the output shaft 1a of the motor 1 and rotates by driving the motor 1 and cools the motor 1 by fan air generated during rotation. The a, and a fan guide 5d for fan air compartments a fan air outlet 5c and fan air outlet 5c for discharging to the inside of the saw cover 5 formed having a configuration in which the inside of the housing 2. The motor 1 and the fan 7 are disposed in the motor housing portion 2a that is inside the portion of the housing 2 that protrudes toward the side opposite to the side where the saw cover 5 is disposed, and the fan guide 5d is disposed on the outer periphery of the fan 7 in the motor housing portion 2a. Is provided so as to surround the ring. As shown in FIG. 4, a slit-shaped cooling air window 2b that communicates between the motor housing portion 2a and the outside is formed in the housing 2 (a slit-shaped gap is formed at the base of the ridge 2c).

  As shown in FIGS. 3 and 4, the portable electric circular saw is provided with a safety cover 17 having a shape covering almost half of the outer periphery of the circular saw blade 4. The safety cover 17 is rotatably held coaxially with the drive shaft 10 of the circular saw blade 4 in the saw cover 5 and can be stored in the saw cover 5, and the safety cover 17 is biased by a biasing means such as a spring (not shown). The rotation position where most part protrudes below the bottom surface 6a of the base 6 and prevents the outer periphery of the circular saw blade 4 from being exposed is the initial state. At the time of cutting, the front end (right side in FIG. 3) of the safety cover 17 in the cutting direction comes into contact with the end of the material to be cut, and in this state, the portable electric circular saw slides in the cutting direction to form a spring. The circular saw blade 4 is exposed on the bottom surface 6 a of the base 6. In the case of a window extraction operation or the like in which a cutting process is performed on the upper surface of the material to be cut that is not continuous with the end surface, the safety cover 17 is also rotated by the operator operating the lever 17a, and the saw blade 4 is moved on the bottom surface 6a of the base 6. Can be exposed. The drive shaft 10 to which the circular saw blade 4 is attached and fixed is interlocked with the output shaft 1a of the motor 1 through a gear mechanism.

  The saw cover 5 as described above is connected to the base 6 so as to sandwich the circular saw blade 4 in the vicinity of both ends in the longitudinal direction of the base 6. Although details are omitted, a mechanism for adjusting the protruding amount of the circular saw blade 4 from the bottom surface of the base 6 by operating the lever 18 and a rotating surface of the circular saw blade 4 with respect to the base 6 (that is, the base 6 A mechanism for tilting the housing 2 with respect to the housing 2 is provided.

  The adoption of the brushless motor 1 can improve the efficiency and reduce the size and weight. For example, the circuit configuration as shown in FIG. 17, that is, the drive circuit 20 including a switching element that switches the power supplied to the brushless motor 1. A control circuit 30 for controlling this, a rectifying / smoothing circuit 40 for converting AC power (AC100V commercial power) input from a power cord 25 drawn from the back of the housing 2 into DC power for driving a brushless motor, and a brushless motor The rotation state detection means 50 which generates a signal according to the rotation position of 1 is required.

  1 and 17, the brushless motor 1 has a rotor 1A, a stator 1B, and a sensor magnet 1C integrated with the rotor 1A.

  The AC power supply input is full-wave rectified by a rectifier (for example, a diode bridge) 41 of a rectifying / smoothing circuit 40, smoothed by a capacitor 42, and supplied to the drive circuit 20. The drive circuit 20 includes an inverter circuit including six switching elements Q1 to Q6 such as FETs connected in a three-phase bridge format. A control signal from the control circuit 30 is applied to each of the gates of the six switching elements Q1 to Q6 that are bridge-connected, and each drain or each source of the six switching elements Q1 to Q6 is a star-connected motor. Connected to one stator winding U, V, W. The six switching elements Q1 to Q6 perform a switching operation in accordance with a control signal, and a stator winding is obtained by using DC voltages supplied to the inverter circuit as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw. Electric power is supplied to U, V, and W, and the brushless motor 1 is started and rotated. The control circuit 30 includes, for example, a microcomputer.

  The rotation state detection means 50 includes a sensor magnet 1C integrated with the rotor 1A of the motor 1 and a rotation position detection element 52 (for example, a hall element) disposed on the sensor substrate 51 shown in FIG. (However, the rotational position detecting element 52 is not shown in FIG. 1). As shown in FIG. 1, the sensor substrate 51 is disposed behind the motor 1 and in close proximity to the sensor magnet 1 </ b> C. The control circuit 30 receives a signal from the rotational position detection element 52 and transmits a control signal for controlling the driving of the motor 1 to the drive circuit 20.

  In the circuit configuration of FIG. 17, the cooling of the drive circuit 20 that handles a large amount of power and generates a large amount of heat is a problem. In the first embodiment, as shown in FIGS. 1 and 6, the circuit board 60 in which the drive circuit 20, the control circuit 30, and the rectifying / smoothing circuit 40 are mounted on one board is accommodated in the circuit board in the housing 1. Arranged in the portion 65. For example, switching elements Q1 to Q6, a rectifier 41, a capacitor 42, and the like are mounted on the upper side of the circuit board 60. Further, the microcomputer or the like of the control circuit 30 is arranged at a board position that is not easily affected by those heat generating components. Note that the motor 1, the sensor substrate 51, and the circuit substrate 60 are electrically connected by a number of wires 68.

  The circuit board housing portion 65 is located at a height position between the handle 3 and the base 6 and is a housing located on the radially outer side of the fan 7 when the direction perpendicular to the rotation axis of the fan 7 is a radial direction. The circuit board cooling air windows 66 formed on the side opposite to the saw blade of the housing 2 as shown in FIG. Except for a large number of circuit board cooling wind windows 67 formed on the side surface of the housing 2, substantially four side surfaces are surrounded by a partition wall 67 between the outer wall portion of the housing 2 and the motor housing portion 2 a. However, a space is provided behind the fan guide 5d, that is, between the back surface of the fan guide 5d and the outer wall portion of the housing 2, which serves as an air passage that allows the motor housing portion 2a and the circuit board housing portion 65 to communicate with each other. The reason why the circuit board housing portion 65 is provided at a height position between the handle 3 and the base 6 is to prevent the operator holding the handle 3 from interfering with the operation. The reason for the arrangement is to generate cooling air from the circuit board cooling wind windows 66 and 67 to the inside of the fan guide 5d by effectively utilizing the negative pressure inside the fan guide 5d due to the rotation of the fan 7.

  In the first embodiment described above, at the time of the cutting operation, the operator holding the handle 3 activates the brushless motor 1 by turning on the switch 3a with the bottom surface 6a of the base 6 placed on the workpiece. While the saw blade 4 is driven to rotate, the base 6 is slid to cut the material to be cut.

  The cooling of the brushless motor 1 and the cooling of the circuit board 60 after the start of the brushless motor 1 are performed as shown in FIG. That is, the centrifugal fan 7 attached and fixed to the output shaft 1a of the motor 1 rotates, and the fan air for cooling is introduced into the motor housing 2a from the slit-shaped cooling air window 2b behind the motor 1, While cooling the motor 1 through the gap between the rotor 1A and the stator 1B, it enters the inside of the fan guide 5d and is discharged to the saw cover 5 side through the fan air discharge port 5c.

  Further, as the fan 7 rotates, the pressure inside the fan guide 5d becomes more negative than the circuit board housing portion 65, so that the circuit board housing portion 65 can be moved from the circuit board cooling air windows 66 and 67 (see FIGS. 4 and 5). The fan wind is introduced into the motor housing portion 2a through the circuit board housing portion 65 while cooling the circuit board 60 on which the switching elements Q1 to Q6, the rectifier 41, the capacitor 42 and the like are mounted, and the fan guide 5d. To the inside. Here, since the cooling air that cools the brushless motor 1 and the cooling air that cools the circuit board 60 are taken in from different openings, the brushless motor 1 and the circuit board 60 can be efficiently cooled. Further, since the circuit board housing portion 65 and the motor housing portion 2a communicate with each other downstream of the cooling air passage of the brushless motor 1 and the cooling air passage of the circuit board 60, one of the brushless motor 1 and the circuit board 60 is connected. By cooling, the other is not cooled with heated air.

  According to the present embodiment, the following effects can be achieved.

(1) Since the circuit board 60 for driving the brushless motor 1 is disposed in the housing located between the handle 3 and the base 6 of the housing 2 housing the motor 1 and in the fan-like passage, the motor The circuit board 60 can be cooled without deteriorating the operability without greatly changing the shape of the housing 2 that houses the housing 1.

(2) Since the circuit board 60 is disposed on the radially outer side of the fan 7 when the direction orthogonal to the rotation axis of the centrifugal fan 7 is the radial direction, the centrifugal fan 7 rotates inside the fan guide 5d. It is possible to generate a fan wind that enters through the circuit board cooling wind windows 66 and 67 and passes through the circuit board 60 by effectively utilizing the negative pressure generated along with the above.

(3) Since the circuit board cooling wind window 66 is provided on the opposite side of the housing 2 from the side where the circular saw blade is provided, the cutting material chips are less likely to enter the housing 2 from the window 66. .

(4) Since the circuit board 60 is positioned below the handle 3, wiring with the switch 3a and the power cord 25 on the handle 3 side is easy.

  A second embodiment of the present invention will be described with reference to FIGS. Since the configuration other than the circuit board cooling structure is substantially the same as that of the first embodiment, differences will be described.

  In the second embodiment, the drive circuit 20 and the rectifying / smoothing circuit 40 of FIG. 17 are mounted on the first circuit board 60A, the control circuit 30 is mounted on the second circuit board 60B, and the first circuit board 60A. Is disposed in the housing located between the handle 3 and the base 6, that is, in the circuit board housing portion 65A. The circuit board housing portion 65 </ b> A has a convex portion 69 </ b> A (projecting toward the saw cover 5) provided on the portion of the housing 2 positioned on the radially outer side of the fan 7 when the direction orthogonal to the rotation axis of the fan 7 is the radial direction. The point formed inside is the same as that of the first embodiment described above, but the first circuit board 60A is made smaller by providing the control circuit 30 as a separate board and provided in the housing 2 portion. The convex portion 69A (projecting toward the saw cover 5) is also small, which is advantageous in terms of operability.

  The second circuit board 60B on which the control circuit 30 is mounted is disposed at a position away from the first circuit board 60A, for example, in a gap between the inner wall surface of the motor housing portion 2a and the stator 1B of the motor 1 (see FIG. 7 is arranged perpendicular to the paper surface). In this case, the electrical connection between the rotation position detection element 52 of FIG. 17 mounted on the sensor substrate 51 and the control circuit 30 is shortened, and the arrangement is less susceptible to noise and the like.

  The cooling of the brushless motor 1 and the cooling of the first and second circuit boards 60A and 60B after the startup of the brushless motor 1 are performed as shown in FIG. That is, the centrifugal fan 7 attached and fixed to the output shaft 1a of the motor 1 rotates, and the fan air for cooling is introduced into the motor housing portion 2a from the slit-like cooling wind window 2b behind the motor, and the motor 1 rotates. The motor 1 is cooled through the gap between the child 1A and the stator 1B, and enters the inside of the fan guide 5d while cooling the second circuit board 60B through the outside of the stator 1B. After that, it is discharged to the saw cover 5 side.

  Further, as the fan 7 rotates, the pressure inside the fan guide 5d becomes more negative than the circuit board housing portion 65A. Therefore, the circuit board cooling air windows 66 and 67 shown in FIGS. The fan wind is introduced, and the first circuit board 60A on which the switching elements Q1 to Q6, the rectifier 41, the capacitor 42 and the like are mounted is cooled, passes through the circuit board housing part 65A, and enters the motor housing part 2a. It reaches the inside of the guide 5d.

  The effect of the second embodiment is substantially the same as that of the first embodiment, but the first circuit board on which the drive circuit 20 and the rectifying / smoothing circuit 40 are mounted by using the control circuit 30 as a separate board. By reducing the area of 60A and reducing the amount of protrusion toward the saw cover 5 side of the housing 2, the control circuit 30 is a separate substrate so that the heat generating components of the drive circuit 20 and the rectifying / smoothing circuit 40 are not affected. The second circuit board 60B on which the control circuit 30 is mounted is arranged near the sensor board 51, thereby shortening the electrical connection between the rotational position detecting element 52 and the control circuit 30 in FIG. The difference is that the structure can be made less susceptible.

  A third embodiment of the present invention will be described with reference to FIGS. Since the configuration other than the circuit board cooling structure is substantially the same as that of the first embodiment, differences will be described.

  In the third embodiment, the drive circuit 20 of FIG. 17 is mounted on the first circuit board 60C, the control circuit 30 is mounted on the second circuit board 60D, and the second circuit board 60D is connected to the handle 3 and the base. 6 is disposed inside the housing, that is, in the circuit board housing portion 65B. The circuit board housing portion 65B is inside the portion of the housing 2 that is located radially outside the fan 7 when the direction orthogonal to the rotation axis of the fan 7 is the radial direction. Since the second circuit board 60D on which the control circuit 30 is mounted is reduced by using a separate board, the convex portion (protruding toward the saw cover 5) for providing the second circuit board 60D in the portion of the housing 2 is eliminated. be able to. For this reason, it becomes advantageous in terms of operability. For example, it becomes easy to operate the lever 18 for adjusting the protruding amount of the circular saw blade 4 from the bottom surface of the base 6 in FIGS.

  The first circuit board 60C on which the drive circuit 20 and the rectifying / smoothing circuit 40 are mounted is disposed in a gap between the inner wall surface of the motor housing portion 2a and the stator 1B of the motor 1 that is located away from the second circuit board 60D. Has been. A circuit board cooling air window 67 is also formed in a side wall portion of the motor housing portion 2a.

  The cooling of the brushless motor 1 and the cooling of the first circuit board 60C and the second circuit board 60D after the activation of the brushless motor 1 are performed as shown in FIG. That is, the centrifugal fan 7 attached and fixed to the output shaft 1a of the motor 1 rotates, and the fan air for cooling is introduced into the motor housing 2a from the slit-like cooling wind window behind the motor 1 to rotate the motor 1. The motor 1 is cooled through the gap between the child 1A and the stator 1B, and the first circuit board 60C on which the switching elements Q1 to Q6, the rectifier 41, the capacitor 42 and the like are mounted is cooled through the outside of the stator 1B. While entering the fan guide 5d, it is discharged to the saw cover 5 side through the fan wind outlet 5c.

  Further, as the fan 7 rotates, the pressure inside the fan guide 5d becomes more negative than the circuit board housing portion 65B, so that the fan is moved from the circuit board cooling air windows 66 and 67 of FIGS. 14 and 15 to the circuit board housing portion 65B. Wind is introduced and the second circuit board 60D is cooled while passing through the circuit board housing part 65B to enter the motor housing part 2a and further into the fan guide 5d.

  In the case of the third embodiment, since the control circuit 30 is a separate board, that is, the second circuit board 60D, the second circuit board 60D has a small area, and the circuit board housing portion 65B for housing this can be made small. Thus, the amount of protrusion of the housing 2 toward the saw cover 5 can be further reduced. The operability of the lever 18 for adjusting the protruding amount of the circular saw blade 4 from the bottom surface of the base 6 is improved. Further, the first circuit board 60C on which the drive circuit 20 and the rectifying / smoothing circuit 40 are mounted is easily disposed through the side of the motor 1 in the motor housing portion 2a so that sufficient fan air can be passed.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

  In the first embodiment, the circuit board 60 has a structure in which a plurality of boards are stacked, and a drive circuit component with high power consumption is mounted on the uppermost board, and a control circuit with lower power consumption is provided on the lower board. You may make it mount. In this case, the substrate floor area can be reduced.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Housing 2a Motor accommodating part 3 Handle 4 Circular saw blade 5 Saw cover 6 Base 7 Centrifugal fan 10 Drive shaft 17 Safety cover 18 Lever 20 Drive circuit 30 Control circuit 40 Rectification smoothing circuit 50 Rotation state detection means 51 Sensor substrate 52 Rotation Position detection element 60, 60A, 60B Circuit board 65, 65A, 65B Circuit board housing part 66, 67 Air window 68 Wiring

Claims (6)

A portable electric cutting machine equipped with a brushless motor,
A housing having a motor housing for housing the motor;
A saw blade that is rotationally driven by the motor;
A base connected to the housing, having a bottom surface capable of sliding on a material to be cut, and having an opening capable of projecting the saw blade downward from the bottom surface;
A fan that is driven to rotate by the motor and that cools the motor by fan air generated during rotation;
A drive circuit including a switching element for switching power supplied to the motor;
A control circuit for controlling the drive circuit;
A circuit board on which either or both of the drive circuit and the control circuit are mounted;
Rotation state detecting means for generating a signal in the control circuit according to the rotation position of the motor,
The rotation state detection means is provided in the motor housing portion,
The housing has a plurality of wind windows on the anti-saw blade side,
The motor is disposed in the fan wind passage between one of the wind windows and the fan;
At least a part of the circuit board is disposed in the fan air passage between the other one of the wind windows and the fan, and the circuit board extends in parallel with the rotation axis of the motor at a side position of the motor. A portable electric cutting machine characterized by being arranged as described above.   The portable electric cutting machine according to claim 1, wherein the circuit board is disposed behind the motor in a cutting direction rear side.   The portable electric cutting machine according to claim 1 or 2, wherein the circuit board is disposed substantially orthogonal to the upper surface of the base in a state where the motor is close to the base.   The handle is provided with a handle and a saw cover, and a lever for adjusting a protruding amount of the saw blade from the bottom surface of the base is provided between the handle and the saw cover. The portable electric cutting machine as described in any one of Claims.   The rotational state detecting means includes a sensor magnet rotated by the motor, a sensor substrate disposed so as to face and oppose the sensor magnet, and a rotational position detecting element disposed on the sensor substrate. The portable electric cutting machine according to any one of claims 1 to 4.   The portable electric cutting machine according to claim 5, wherein the sensor board and the circuit board are electrically connected.

Images