Work equipment

Abstract

To provide a work machine which achieves the optimal layout while enabling driving suitable for work by devising arrangement of a switch part for switching a coil connection method.SOLUTION: A work machine 1 has a control board 11, a relay substrate 30, and multiple battery connection terminals 27 within a battery attachment part 23. The multiple battery connection terminals 27 face the lower side of the battery attachment part 23. The relay substrate 30 is provided above the battery connection terminals 27. Multiple relay elements 31 are mounted on an upper surface of the relay substrate 30. The multiple relay elements 31 switch a coil connection method of a motor 40 between delta connection and star connection. The control board 11 is provided above the relay substrate 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a work machine in which the wiring method of the coils of a motor can be switched. [Background technology]

[0002] There is known a technology that enables driving suited to a task by changing the wiring method of the motor coil. Patent Document 1 describes an electric power tool as a work machine in which the wiring method of the motor coil can be switched depending on the type of power source (power source voltage) connected. Patent Document 2 describes an electric power tool as a work machine in which the wiring method of the motor coil can be switched by the operator operating a wiring changeover switch.

[0003] Patent Document 3 describes an electric power tool as a work machine in which the coils of the motor are star-connected (Y-connected) and the number of series or parallel connections of the coils in the star connection can be changed depending on the load on the motor. Furthermore, it describes that when switching the connection relationship of the coils, a period is set during which the connection relationship is repeatedly changed, thereby suppressing sudden changes in torque and rotation speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-121158 [Patent Document 2] Japanese Patent Application Publication No. 2019-047605 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-111734 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, a relay for switching the coil wiring method is mounted on a motor board housed in a cutting section. In Patent Document 2, a wiring changeover switch is provided between the housing and the power cord or in the grip. However, Patent Documents 1 and 2 do not consider the optimal placement of the relay or changeover switch in the work machine.

[0006] In Patent Document 3, the coil connections must be switched at high speed using semiconductor switching elements, which makes the control complex. Also, although the coil connections must be switched at high speed using semiconductor switching elements, when driving a motor with three coils, an induced electromotive force is generated in the three unused coils, which applies a high voltage in the reverse direction to the switching elements, potentially damaging the switching elements, and the circuitry required to address this becomes complex.

[0007] In this situation, the present inventors have recognized the following problems. Problem 1: To provide a work machine that can realize a suitable layout while enabling drive suited to the work by devising the arrangement of a switching unit for switching the coil wiring method. ·Problem 2: To provide a work machine that can suppress abrupt changes in motor rotation speed due to switching of the coil connection method using simple control.

[0008] The present invention aims to solve at least one of the above problems 1 and 2. [Means for solving the problem]

[0009] One aspect of the present invention is a work machine. a motor including a stator having a plurality of teeth, a plurality of coils provided on the teeth and connected to each other by a predetermined connection method, and a rotor rotatable relative to the stator; a tool holder driven by the motor and holding a tool bit; an operation switch for instructing start and stop of the motor; a motor housing that accommodates the motor; ,before a handle housing in which the operation switch is provided; , Ba a housing having a battery mounting portion provided with a battery connection terminal; a connection switching unit accommodated in the housing for switching a connection method of the plurality of coils from a first connection method to a second connection method different from the first connection method; a drive circuit section housed in the housing and configured to drive the motor; It is a work machine , A direction parallel to the rotation shaft of the motor is defined as a left-right direction, The direction perpendicular to the left-right direction and parallel to the direction of travel of the work machine is defined as the front-rear direction, If the direction perpendicular to the left-right and front-back directions is the up-down direction, The tool bit extends downward from the housing, The handle housing is located above the motor housing, extends downward, and has the operation switch at its upper end. the battery attachment portion is connected to a lower portion of the handle housing; the connection switching unit is disposed below the drive circuit unit; It is characterized by:

[0010] Another aspect of the present invention is a work machine. a motor including a stator having a plurality of teeth, a plurality of coils provided on the teeth and connected to each other by a predetermined connection method, and a rotor rotatable relative to the stator; a tool holder driven by the motor and holding a tool bit; an operation switch for instructing start and stop of the motor; a housing including a motor housing that accommodates the motor, a handle housing in which the operation switch is provided, and a battery mounting portion in which a battery connection terminal is provided; a connection switching unit for switching a connection method of the plurality of coils from a first connection method to a second connection method different from the first connection method; a drive circuit unit that drives the motor, a first substrate on which the drive circuit unit is mounted and a second substrate on which the connection switching unit is mounted; The overlap when viewed from a direction perpendicular to the plane of the first substrateand the housing is adapted to receive the It is characterized by:

[0011] Another aspect of the present invention is a work machine. a motor including a stator having a plurality of teeth, a coil provided on the teeth, and a rotor rotatable relative to the stator; a trigger switch for instructing the start and stop of the motor; a connection switching unit for switching the connection method of the coil, The coil connection method is switchable between a delta connection and a star connection, When the trigger switch is operated, the coil is connected in the delta connection to drive the motor; When the load on the motor exceeds a first threshold, a first control is executed to keep the current flowing through the motor constant in the delta connection state or to reduce the rotation speed of the motor in response to an increase in the load on the motor; When the load exceeds a second threshold value that is greater than the first threshold value during the first control, the coil connection method is switched to the star connection. Another aspect of the present invention is a work machine. a motor including a stator having a plurality of teeth, a coil provided on the teeth, and a rotor rotatable relative to the stator; a trigger switch for instructing the start and stop of the motor; a connection switching unit for switching the connection method of the coil; a drive circuit unit that drives the motor; a control unit that controls the drive circuit unit, the connection switching unit includes a first relay unit used when the coil is delta-connected and a second relay unit used when the coil is star-connected, the control unit is configured to, when switching the coil from the delta connection to the star connection, stop driving the drive circuit unit, then turn off the first relay unit, and then turn on the second relay unit to start driving the drive circuit unit. It is characterized by: Another aspect of the present invention is a work machine. a motor including a stator having a plurality of teeth, a coil provided on the teeth, and a rotor rotatable relative to the stator; a trigger switch for instructing the start and stop of the motor; a connection switching unit for switching the connection method of the coil; a drive circuit unit that drives the motor; a control unit that controls the drive circuit unit, the connection switching unit includes a first relay unit used when the coil is delta-connected and a second relay unit used when the coil is star-connected, the control unit is configured to stop driving the drive circuit unit and then turn off the second relay unit when switching the coil from the star connection to the delta connection, and then turn on the first relay unit to start driving the drive circuit unit. It is characterized by:

[0012] Any combination of the above components and conversion of the present invention between methods, systems, etc. are also valid aspects of the present invention. [Effects of the Invention]

[0013] According to the present invention, at least one of the above problems 1 and 2 can be solved. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a right side view of a work machine 1 according to a first embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 3 is a cross-sectional view of the motor 40 of the work machine 1. [Figure 4] Enlarged view of the main part of Figure 2. [Figure 5] FIG. [Figure 6] FIG. 2 is a perspective view of the work machine 1 with the left handle housing 24 omitted. [Figure 7] 2 is a perspective view showing the internal configuration of the battery mounting section 23 of the work machine 1 together with the battery pack 7. FIG. [Figure 8] Left side cross-sectional view of the same. [Figure 9] 3 is a diagram showing the relay board 30 of the work machine 1 as viewed from above. FIG. [Figure 10] 2 is a left side cross-sectional view of the work machine 1, showing the flow of the air current (cooling air) generated by the fan 17. FIG. [Figure 11] Cross section AA of Figure 10. [Figure 12] FIG. 11 is an enlarged perspective view of part B in FIG. [Figure 13] 13 is a diagram of FIG. 12 with the trigger switch 6 removed. [Figure 14] FIG. 4 is a left side cross-sectional view of a work machine 1A according to a second embodiment of the present invention. [Figure 15] FIG. 11 is a left side view of a work machine 1B according to a third embodiment of the present invention. [Figure 16] FIG. [Figure 17] FIG. 10 is a perspective view of a work machine 1C according to a fourth embodiment of the present invention. [Figure 18] FIG. [Figure 19A] Cross section CC of Figure 18. [Figure 19B] 19B is a cross-sectional view showing a state in which the left opening of the intermediate housing 324 in FIG. 19A is covered with a cover member 328. FIG. [Figure 20] FIG. 1C is a circuit block diagram of a work machine 1C. [Figure 21] 10 is a state transition diagram of the control of the work machine 1C. [Figure 22] 1A is a flowchart of an operation for switching the coil connection method of the motor 340 in the work machine 1C from a delta connection to a star connection, and FIG. 1B is a flowchart of an operation for switching the coil connection method of the motor 340 in the work machine 1C from a star connection to a delta connection. [Figure 23] This graph shows the relationship between torque and saw blade rotation speed when the torque of motor 340 in work machine 1C increases, along with the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to delta connection without switching, the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to star connection without switching, and the relationship between torque and saw blade rotation speed in balanced type comparison example 1. [Figure 24] 10 is a graph showing the relationship between the current and torque of a motor 340 when the torque of the motor 340 is increased in a work machine 1C, together with the relationship between the current and torque in a balanced comparative example 1. [Figure 25] 24 is a graph in which the graph of the balanced type comparative example 1 in FIG. 23 is replaced with the graph of the high rotation type comparative example 2. [Figure 26] 25 is a graph in which the graph of the balanced type comparative example 1 in FIG. 24 is replaced with the graph of the high rotation type comparative example 2. [Figure 27] 24 is a graph in which the graph of the balanced type comparative example 1 in FIG. 23 is replaced with the graph of the high torque type comparative example 3. [Figure 28]25 is a graph in which the graph of the balanced type comparative example 1 in FIG. 24 is replaced with the graph of the high torque type comparative example 3. [Figure 29] This graph shows the relationship between torque and saw blade rotation speed when the torque of motor 340 in work machine 1C decreases, along with the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to delta connection without switching, the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to star connection without switching, and the relationship between torque and saw blade rotation speed in balanced type comparison example 1. [Figure 30] FIG. 22 is a state transition diagram of control in Comparative Example 4 in which control C in FIG. 21 is eliminated. [Figure 31] 24 is a graph in which the graph of the fourth embodiment in FIG. 23 is replaced with the graph of the fourth comparative example. [Figure 32] 25 is a graph in which the graph of the fourth embodiment in FIG. 24 is replaced with the graph of the fourth comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following, identical or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted where appropriate. The embodiments are illustrative and do not limit the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0016] (Embodiment 1) 1 to 13 relate to a work machine 1 according to a first embodiment of the present invention. FIG. 1 defines the front-rear and up-down directions of the work machine 1, which are perpendicular to each other. The front-rear direction is a direction parallel to the axial direction of a motor shaft 41 of the work machine 1. The work machine 1 is a driver drill. The work machine 1 includes a housing 20.

[0017] The housing 20 is, for example, a resin molded body having a two-part structure, left and right, and is formed by fastening a left housing 24 and a right housing 25 shown in Fig. 5 together and integrating them with screws or the like. In Fig. 5, an elastomer 29 covering at least a portion of the outer surfaces of the left housing 24 and the right housing 25 is shown separated from the left housing 24 and the right housing 25. The housing 20 includes a motor housing (body portion) 21 that houses the motor 40 etc., a handle housing (handle portion) 22 that is gripped by the operator, and a battery attachment portion 23.

[0018] The motor housing 21 is a cylindrical part whose central axis is approximately parallel to the front-to-rear direction. A clutch dial 8, a sleeve 9, and a chuck part 10 are provided in front of the motor housing 21. The chuck part 10 holds a tool bit or other tool tip (not shown). The chuck part 10 and the tool tip held therein are examples of an output part.

[0019] The handle housing 22 has one end (upper end) connected to the middle part of the motor housing 21 in the front-to-rear direction and extends downward from the middle part. A trigger switch (operation switch) 6 is provided at the upper end of the handle housing 22, which allows the user to start and stop the motor 40.

[0020] The battery attachment section 23 is provided at the other end (lower end) of the handle housing 22, and the battery pack 7 can be detachably attached thereto. The work machine 1 operates using power from the battery pack 7. The work machine 1 has an operation panel 16 on the top surface of the battery attachment section 23. The user can switch the operation mode of the work machine 1 using the operation panel 16.

[0021] The work machine 1 has a motor 40, a fan 17, a reduction mechanism 4, and a clutch mechanism 5 inside the motor housing 21 and the clutch dial 8.

[0022] The motor 40 is an inner rotor type brushless motor. The supply of electricity to the motor 40 is controlled by a controller (controller) and switching elements 13 provided on a control board 11. As shown in Fig. 3, the motor 40 includes a motor shaft (output shaft) 41, a rotor core 42, a rotor magnet (permanent magnet) 43, a stator core 44, and a stator coil 45.

[0023] The rotor core 42 is provided around the motor shaft 41 and rotates integrally with the motor shaft 41 relative to the stator core 44. There are four rotor magnets 43, which are inserted and held at 90-degree intervals in the circumferential direction of the rotor core 42. The rotor cores 42 and the rotor magnets 43 constitute the rotor of the motor 40.

[0024] The stator core 44 is disposed so as to surround the outer periphery of the rotor core 42. The stator core 44 constitutes the stator of the motor 40. The stator core 44 includes a cylindrical (annular) yoke portion 46 and six teeth (teeth portions) 47 that protrude radially inward from the yoke portion 46. A stator coil 45 is provided on each tooth 47. Each tooth 47 forms a winding slot.

[0025] The reduction mechanism 4 is located in front of the motor 40 and reduces the rotation of the motor 40 before transmitting it to the chuck 10. The clutch mechanism 5 cuts off the transmission of rotation from the reduction mechanism 4 to the chuck 10 when the torque set by the clutch dial 8 is exceeded.

[0026] The fan 17 is directly connected (attached) to the front of the motor shaft 41. The fan 17 is a centrifugal fan driven by the motor 40, and generates cooling air to cool the motor 40 and other components. As will be described later with reference to Figures 10 and 11, the cooling air generated by the fan 17 also cools the control board 11, the relay board 30, and the elements mounted thereon.

[0027] As shown in FIGS. 2 and 4, the work machine 1 has, inside the battery mounting section 23, a control board (control circuit board) 11, a board holder 15, a relay board 30, a plurality of battery connection terminals 27, and a terminal holder 28.

[0028] The plurality of battery connection terminals 27 are held by a terminal holder 28 and face downward from the battery mounting section 23. The plurality of battery connection terminals 27 come into contact with terminals of the battery pack 7 mounted in the battery mounting section 23 and are electrically connected thereto.

[0029] The relay board 30 is provided above the battery connection terminals 27. The relay board 30 has a plurality of relay elements 31 mounted on its upper surface. The relay board 30 and the plurality of relay elements 31 are positioned between the motor 40 and the plurality of battery connection terminals 27, between the handle housing 22 and the plurality of battery connection terminals 27, and between the control board 11 and the plurality of battery connection terminals 27 in the vertical direction.

[0030] The plurality of relay elements 31 constitute a relay unit. The plurality of relay elements 31 is an example of a connection switching unit for switching the connection method of the stator coil 45. As shown in Fig. 9, the plurality of relay elements 31 includes three delta-connection relay elements 32 as a first relay unit and three star-connection relay elements 33 as a second relay unit.

[0031] The delta connection relay element 32 and the star connection relay element 33 are turned on and off exclusively by a controller (such as a microcomputer) provided on the control board 11. When the delta connection relay element 32 is on, the stator coil 45 is delta connected. When the star connection relay element 33 is on, the stator coil 45 is star connected.

[0032] The control board 11 is located above the relay board 30 and is housed in a board holder 15. The board holder 15 is, for example, an aluminum case. Using an aluminum case can improve the heat dissipation effect, and the cooling effect of the control board 11 (particularly the switching elements 13) by the airflow flowing inside the housing 20 (described later) can be improved. The control board 11 is equipped with a controller as a control unit, and has multiple switching elements 13 mounted on its underside. The multiple switching elements 13 are covered with an insulating sheet 14. The multiple switching elements 13 constitute a drive circuit unit (inverter circuit) that energizes and drives the motor 40 under the control of the controller.

[0033] A plurality of openings 26 are provided on each of the left and right side surfaces of the battery mounting section 23. The plurality of openings 26 form air windows (air intakes) that connect the inside and outside of the battery mounting section 23. The relay element 31 is disposed inside the battery mounting section 23 so as to face the openings 26. The control board 11 is located closer to the motor 40 (above) than the openings 26 when viewed from the left-right direction.

[0034] 1, a plurality of exhaust ports 35 are provided on each of the left and right side surfaces of the motor housing 21 at positions radially outward from the fan 17. The plurality of exhaust ports 35 form air windows that connect the inside and outside of the motor housing 21.

[0035] As shown in Figures 10 and 11, the airflow generated by the fan 17 enters the battery mounting section 23 through the opening 26, flows upward while cooling the control board 11, relay board 30, and the elements mounted thereon (such as the switching element 13 and relay element 31), passes through the handle housing 22, reaches the motor housing 21, passes through the fan 17, and is exhausted to the outside of the motor housing 21 through the exhaust port 35.

[0036] As shown in Figures 2, 12, and 13, the handle housing 22 has a rib 22a that supports the switch body 6a of the trigger switch 6. The rib 22a is a protrusion that rises from the inner surface of the handle housing 22 to form a rectangle when viewed from the left and right. Notches 22b are provided on the upper and lower edges of the rib 22a. As shown in Figure 12, the presence of the notches 22b creates a gap 22c between the switch body 6a and the rib 22a. The gap 22c provides a passage for airflow through the handle housing 22.

[0037] According to this embodiment, the following effects can be achieved.

[0038] (1) A suitable layout can be achieved by arranging the multiple relay elements 31 that constitute the wiring switching unit in the battery mounting section 23. For example, if the relay elements 31 were arranged inside the motor housing 21, space for arranging the relay elements 31 would have to be secured inside the motor housing 21, which is densely packed with components, making it difficult to increase the size of the motor housing 21 and optimize the layout relative to other components. Furthermore, if the relay elements 31 were arranged inside the handle housing 22, the diameter of the grip would increase, making it difficult to use. In contrast, if the relay elements 31 are arranged in the battery mounting section 23 as in this embodiment, although the battery mounting section 23 needs to be larger in the vertical direction, the relay elements 31 are laid out close to the control board 11, making it easier to organize the wiring and make the device more compact.

[0039] (2) Since the control board 11 and the relay board 30 are configured to be opposite each other in the vertical direction, the increase in size in the front-to-back and left-to-right directions can be suppressed compared to when the relay element 31 is mounted on the control board 11. Therefore, the battery mounting section 23 only needs to be larger in the vertical direction compared to a conventional battery mounting section that does not accommodate the relay element 31, and the impact on appearance caused by the placement of the relay element 31 can be suppressed.

[0040] (3) The opening 26 is provided on the side of the battery mounting section 23, and the airflow generated by the fan 17 flows in through the opening 26 to cool the control board 11, the relay board 30, and the elements mounted thereon, thereby preventing the elements from overheating. In addition, by arranging the control board 11, particularly the switching element 13 which is prone to heat generation, above the opening 26, the switching element 13 can be effectively cooled while the relay element 31 is cooled.

[0041] (4) The notch 22b of the rib 22a supporting the switch body 6a of the trigger switch 6 forms a gap 22c that serves as a passage for the airflow flowing inside the handle housing 22. Therefore, the passage area for the airflow generated by the fan 17 inside the handle housing 22 is increased, the airflow flows more efficiently, and the cooling efficiency is improved.

[0042] (Embodiment 2) Figure 14 relates to a work machine 1A according to a second embodiment of the present invention. Figure 14 defines the front-rear and up-down directions of the work machine 1A, which are perpendicular to each other. The front-rear direction is a direction parallel to the axial direction of a motor shaft 141 of the work machine 1A. The work machine 1A is an impact driver. The work machine 1A includes a housing 120.

[0043] The housing 120 is, for example, a resin molded body, and includes a motor housing (body portion) 121 that houses the motor 140 and the like, a handle housing (handle portion) 122 that is gripped by an operator, and a battery attachment portion 123. The motor housing 121 is a cylindrical portion whose central axis is approximately parallel to the front-rear direction.

[0044] The work machine 1A has a motor 140, a fan 117, a speed reduction mechanism 104, a hammer 105, and an anvil 108 inside a motor housing 121. The motor 140 has the same configuration as the motor 40 of the first embodiment.

[0045] The reduction mechanism 104 is located in front of the motor 140 and reduces the speed of the rotation of the motor 140 before transmitting it to the hammer 105. The hammer 105 rotates or rotary strikes the anvil 108. A chuck portion 110 is provided at the tip of the anvil 108. The chuck portion 110 holds a tool tip such as a bit (not shown).

[0046] One end (upper end) of the handle housing 122 is connected to the middle part in the front-to-rear direction of the motor housing 121 and extends downward from the middle part. A trigger switch (operation switch) 106 is provided at the upper end of the handle housing 122, which allows the user to start and stop the motor 140.

[0047] The battery mounting section 123 is provided at the other end (lower end) of the handle housing 122, and the battery pack 107 can be detachably mounted thereon. The work machine 1A operates using power from the battery pack 107. The work machine 1A has an operation panel 116 on the top surface of the battery mounting section 123. The user can use the operation panel 116 to switch the operation mode of the work machine 1A.

[0048] The fan 117 is directly connected (attached) to the rear of the motor shaft 141. The fan 117 is a centrifugal fan driven by the motor 140, and generates cooling air to cool the motor 140, the control board 11, the relay board 30, and the elements mounted thereon.

[0049] Similar to the work machine 1 of the first embodiment, the work machine 1A has a control board 11, a board holder 15, a relay board 30, and a plurality of battery connection terminals 127 inside the battery mounting section 123. The plurality of battery connection terminals 127 come into contact with terminals of the battery pack 107 mounted in the battery mounting section 123 and are electrically connected to them.

[0050] The layout relationship of the control board 11 and relay board 30 in the battery mounting section 123, and the elements mounted thereon (such as the switching element 13 and relay element 31) is the same as in the first embodiment.

[0051] A plurality of openings 126 are provided on each of the left and right side surfaces of the battery mounting section 123. The plurality of openings 126 form air windows (air intakes) that connect the inside and outside of the battery mounting section 123. The relay element 31 is disposed inside the battery mounting section 123 so as to face the openings 126. The control board 11 is located closer to the motor 140 (above) than the openings 126 when viewed from the left-right direction.

[0052] A plurality of exhaust ports 135 are provided on each of the left and right side surfaces of the motor housing 21 at positions radially outward of the fan 117. The plurality of exhaust ports 135 form air windows that connect the inside and outside of the motor housing 121.

[0053] This embodiment can also achieve the same effects as the first embodiment.

[0054] (Embodiment 3) 15 and 16 relate to a work machine 1B according to a third embodiment of the present invention. FIG. 15 defines the front-rear and up-down directions of the work machine 1B, which are perpendicular to each other. The front-rear direction is a direction parallel to the axial direction of a motor shaft 241 of the work machine 1B. The work machine 1B is a grinder. The work machine 1B includes a housing 220.

[0055] The housing 220 is, for example, a resin molded body, and includes a motor housing (body portion) 221 that houses the motor 240 and the like, a handle housing (handle portion) 222 that is gripped by the operator, and a battery attachment portion 223.

[0056] The motor housing 221 is a cylindrical part whose central axis is approximately parallel to the front-to-rear direction. The work machine 1B has an operation panel 216 on the top surface of the motor housing 221. A user can switch the operation mode of the work machine 1B using the operation panel 216. A gear case 224 is provided in front of the motor housing 221.

[0057] The handle housing 222 is a cylindrical part whose central axis is approximately parallel to the front-to-rear direction and connected to the rear of the motor housing 221. An operation switch (slide switch) 206 is provided on the left side surface of the handle housing 222, which allows the user to start and stop the motor 240.

[0058] The battery mounting portion 223 is provided at the rear end of the handle housing 222, and allows the battery pack 207 to be detachably mounted thereon. The work machine 1B operates using the power of the battery pack 207.

[0059] The work machine 1B has a motor 240 and a fan 217 inside a motor housing 221. The work machine 1B has a speed reduction mechanism 204 inside a gear case 224. The motor 240 has the same configuration as the motor 40 of the first embodiment.

[0060] The speed reducing mechanism 204 is located in front of the motor 240, and reduces the speed of the rotation of the motor 240, converts the direction of the rotation axis into a vertical direction, and transmits the rotation to a rotating tool 209 such as a grindstone.

[0061] The fan 217 is directly connected (attached) to the front of the motor shaft 241. The fan 217 is an axial flow fan that is driven by the motor 240 to generate a forward airflow, and generates cooling air that cools the motor 240, the control board 211, the relay board 30, and the elements mounted thereon.

[0062] The work machine 1B has a control board 211, a board holder 215, a relay board 30, and a plurality of battery connection terminals 227 inside the battery mounting section 223.

[0063] The plurality of battery connection terminals 227 face the rear of the battery mounting section 223. The plurality of battery connection terminals 227 come into contact with terminals of the battery pack 207 mounted in the battery mounting section 223 and are electrically connected thereto.

[0064] The relay board 30 is provided in front of the battery connection terminal 227. The multiple relay elements 31 are turned on and off by a controller (such as a microcomputer) provided on the control board 211. The relay board 30 and the multiple relay elements 31 are located between the motor 240 and the multiple battery connection terminals 227, between the handle housing 222 and the multiple battery connection terminals 227, and between the control board 211 and the multiple battery connection terminals 227 in the front-rear direction.

[0065] Control board 211 is located in front of relay board 30 and is housed in board holder 215. Board holder 215 is, for example, an aluminum case. Control board 211 is equipped with a controller as a control unit and multiple switching elements that form an inverter circuit controlled by the controller. This configuration can achieve the same effects as in embodiment 1.

[0066] A plurality of openings 226 are provided on each of the left and right side surfaces of the battery mounting section 223. The plurality of openings 226 form air windows (air intakes) that communicate between the inside and outside of the battery mounting section 223. The relay element 31 is disposed inside the battery mounting section 223 so as to face the openings 226. The control board 211 is located closer to the motor 240 (forward) than the openings 226 when viewed from the left-right direction.

[0067] An exhaust port 235 is provided on each front surface of the gear case 224. The exhaust port 235 forms a ventilating window that connects the inside and outside of the gear case 224.

[0068] The airflow generated by the fan 217 enters the battery mounting section 223 through the opening 226, flows forward while cooling the control board 211, the relay board 30, and the elements mounted thereon (such as switching elements and relay elements 31), passes through the handle housing 222, reaches the motor housing 221, flows forward while cooling the motor 240, passes through the fan 217, enters the gear case 224, and is exhausted to the outside of the gear case 224 through the exhaust port 235.

[0069] This embodiment can also achieve the same effects as the first embodiment.

[0070] (Fourth embodiment) 17 to 29 relate to a work machine 1C according to a fourth embodiment of the present invention. Figs. 18 and 19A define the mutually perpendicular front-rear, up-down, and left-right directions of the work machine 1C. The left-right direction is a direction parallel to the axial direction of a motor shaft 341 of the work machine 1C. The work machine 1C is a portable circular saw. The work machine 1C includes a housing 320.

[0071] The housing 320 is, for example, a resin molded body, and includes a motor housing 321 that houses the motor 340 and the like, a handle housing 322 that is held by the operator, a battery mounting portion 323, and an intermediate housing 324.

[0072] The motor housing 321 is a cylindrical part whose central axis is approximately parallel to the left-right direction. The handle housing 322 extends obliquely in the front-to-back and up-down directions above the right part of the motor housing 321. A trigger switch 306 is provided at the upper end of the handle housing 322, which allows the user to start and stop the motor 340.

[0073] A metal gear case (saw cover) 325 is connected to the left side of the handle housing 322. The gear case 325 houses a speed reduction mechanism (not shown) and covers the upper half of the saw blade 309.

[0074] The battery attachment section 323 extends leftward from the rear end of the handle housing 322, and a battery pack 307 (FIG. 20) can be detachably attached to it. The work machine 1C operates using power from the battery pack 307. The work machine 1C has an operation panel 316 on the top surface of the battery attachment section 323. The user can use the operation panel 316 to switch the operation mode of the work machine 1C.

[0075] The intermediate housing 324 is located behind the motor housing 321 , to the side (right side) of the battery mounting portion 323 , and below the handle housing 322 .

[0076] The work machine 1C has a motor 340 inside a motor housing 321. The motor 340 has the same configuration as the motor 40 of the first embodiment. The rotation of the motor 340 is reduced in speed by a reduction mechanism in a gear case 325 and transmitted to the saw blade 309.

[0077] The work machine 1C has a control board 311 and a plurality of battery connection terminals 327 inside a battery mounting section 323. The plurality of battery connection terminals 327 face downward from the battery mounting section 323. The plurality of battery connection terminals 327 come into contact with terminals of a battery pack 307 mounted in the battery mounting section 323 and are electrically connected thereto.

[0078] The work machine 1C has a relay board 30 inside an intermediate housing 324. The relay board 30 is equipped with a plurality of relay elements 31 similar to those in the first embodiment. The relay board 30 is attached to the intermediate housing 324 with screws or the like. The intermediate housing 324 has an opening on the left side. This opening is covered by a battery pack 307 attached to a battery attachment section 323. As shown in FIG. 19B , a cover member 328 is attached to this opening with screws or a latch, and covering the opening with the cover member 328 prevents the relay board 30 from falling off and provides waterproofing and dust protection.

[0079] Fig. 20 is a circuit block diagram of the work machine 1C. The circuit configuration and operation shown in Fig. 20 are common to the first to third embodiments described above.

[0080] The inverter circuit 64 is made up of six switching elements connected in a three-phase bridge. The inverter circuit 64 is provided between the output terminals of the battery pack 307. The detection resistor 65 is provided in the path of the current (hereinafter referred to as "motor current") flowing through the stator coil 345. The inverter circuit 64 is mounted on the control board 311.

[0081] The control power supply circuit 51 converts the output voltage of the battery pack 307 into a power supply voltage for the calculation unit 50 and other components, and supplies it to the calculation unit 50 and other components. The current detection circuit 52 detects the motor current from the voltage across the detection resistor 65 and sends it to the calculation unit 50, which serves as a control unit. The switch operation detection circuit 53 detects the operation of the trigger switch 306 and sends it to the calculation unit 50. The battery type detection circuit 54 detects the type of battery pack 307 (rated voltage, rated capacity, etc.) from the voltage of an identification terminal (not shown) of the battery pack 307 and sends it to the calculation unit 50. The voltage detection circuit 55 detects the output voltage of the battery pack 307 and sends it to the calculation unit 50. The control power supply circuit 51 and other circuits, as well as the calculation unit 50, are mounted on a control board 311.

[0082] The control signal circuit 56 outputs control signals that control the on / off of each switching element of the inverter circuit 64 under the control of the calculation unit 50. The rotational position detection circuit 57 detects the rotational position of the motor 340 from the output signal of a Hall IC (magnetic sensor) 63 provided near the rotor magnet 343 and sends the signal to the calculation unit 50. The rotation speed detection circuit 58 detects the rotation speed of the motor 340 (hereinafter referred to as "motor rotation speed") from the output signal of the rotational position detection circuit 57 and sends the signal to the calculation unit 50. The operation mode detection circuit 59 detects the operation mode in accordance with the operation of the operation mode switch 60 by the user and sends the signal to the calculation unit 50. The illumination LED drive circuit 61 drives the illumination LED 62 under the control of the calculation unit 50.

[0083] The calculation unit 50 includes a microcontroller and the like, and controls the overall operation of the work machine 1C. The calculation unit 50 controls the driving of the inverter circuit 64 via the control signal circuit 56, and controls the drive current supplied to the stator coil 345. The calculation unit 50 controls the on / off of the relay element 31, and switches the wiring method of the stator coil 345 (hereinafter referred to as the "coil wiring method") between the delta connection and the star connection. Specifically, the calculation unit 50 sets the coil wiring method to the delta connection by turning on the delta connection relay element 32 and turning off the star connection relay element 33, and sets the coil wiring method to the star connection by turning on the star connection relay element 33 and turning off the delta connection relay element 32.

[0084] 21 is a state transition diagram of the control of the work machine 1C. When the calculation unit 50 detects that the trigger switch 306 is on without detecting any errors in a state in which the motor 340 is stopped (S1), it executes control A (S2).

[0085] In control A, the calculation unit 50 uses a delta connection for the coil connection method and performs constant speed control on the motor 340. Constant speed control is a control that senses the motor rotation speed and adjusts (controls) the duty and lead angle to maintain a constant rotation speed, thereby controlling the motor output. In control A, fixed duty control may be used instead of constant speed control. In fixed duty control, the duty (hereinafter referred to as "duty") of the drive signal (PWM signal) of the inverter circuit 64 is fixed to the maximum (100%), for example.

[0086] If the load on the motor 340 (hereinafter referred to as "load") exceeds a first threshold while control A is being executed, the calculation unit 50 executes control C (S3). That is, if the load on the motor 340 increases (if an increase in the load is detected), the calculation unit 50 switches from control A to control C. The fact that the load has exceeded the first threshold can be detected by an increase in the motor current or a decrease in the motor rotation speed.

[0087] In control C, the calculation unit 50 executes, as the first control, constant current control to keep the motor current constant when the coil connection method is delta connection. Constant current control is a control that senses the motor current and adjusts (controls) the duty and lead angle to keep the current constant, thereby controlling the motor output. The motor current in constant current control is a predetermined value that is lower than the threshold value for overcurrent protection and close to the threshold value. Instead of constant current control, the first control may be a control that gradually reduces the motor output (rotation speed) as the load increases.

[0088] The calculation unit 50 returns to control A (S2) when the load falls below the first threshold (when the load decreases) during execution of control C. The fact that the load has fallen below the first threshold can be detected by a decrease in motor current or an increase in motor rotation speed.

[0089] If the load exceeds a second threshold value that is greater than the first threshold value while Control C is being executed, the calculation unit 50 switches the coil connection method to star connection (S4) and executes Control B (S5). That is, if the load on the motor 340 increases further (if a further increase in the load is detected), the calculation unit 50 switches from Control C to Control B. The fact that the load has exceeded the second threshold value can be detected by a decrease in the motor rotation speed.

[0090] In control B, the calculation unit 50 executes fixed duty control in a state where the coil connection method is star connection. Fixed speed control may be used instead of fixed duty control.

[0091] When the load falls below a third threshold value that is lower than the first threshold value (when the load decreases) during execution of control B, the calculation unit 50 switches the coil connection method to the delta connection (S6) and returns to control A (S2). The fact that the load has fallen below the third threshold value can be detected by a decrease in the motor current.

[0092] When the calculation unit 50 detects any of various errors or when it detects that the trigger switch 306 is off, it stops the motor 340 (S1).

[0093] 22(A) is a flowchart of the operation (S4 in FIG. 21) for switching the coil connection method of the motor 340 in the work machine 1C from delta connection to star connection. The calculation unit 50 stops driving the inverter circuit 64 (S11), turns off the delta connection relay element 32 (S12), turns on the star connection relay element 33 (S13), and starts driving the inverter circuit 64 (S14).

[0094] 22(B) is a flowchart of the operation (S6 in FIG. 21) of switching the coil connection method of the motor 340 in the work machine 1C from star connection to delta connection. The calculation unit 50 stops driving the inverter circuit 64 (S21), turns off the star connection relay element 33 (S22), turns on the delta connection relay element 32 (S23), and starts driving the inverter circuit 64 (S24).

[0095] In this way, by providing a predetermined waiting time between turning off one of the delta connection relay element 32 and the star connection relay element 33 and turning on the other, it is possible to prevent the delta connection relay element 32 and the star connection relay element 33 from being turned on simultaneously. Furthermore, by stopping the inverter circuit 64 when switching on and off the delta connection relay element 32 and the star connection relay element 33, it is possible to prevent inadvertent operation.

[0096] Fig. 23 is a graph showing the relationship between torque and saw blade rotation speed as the torque of motor 340 (hereinafter referred to as "torque") increases in work machine 1C, along with the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to a delta connection without switching, the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to a star connection without switching, and the relationship between torque and saw blade rotation speed in balanced comparative example 1. Fig. 24 is a graph showing the relationship between current and torque of motor 340 as the torque of motor 340 is increased in work machine 1C, along with the relationship between current and torque in balanced comparative example 1.

[0097] In the example of FIG. 23 , in control A, the calculation unit 50 executes constant speed control of the motor 340 in a delta connection state so that the rotational speed of the saw blade 309 (hereinafter referred to as the "saw blade rotational speed") is 5,000 rpm. In constant speed control, the duty is increased as the torque increases to maintain the saw blade rotational speed at 5,000 rpm, but the duty reaches its maximum when the torque reaches 2 N m. Therefore, in control A, in a torque range exceeding 2 N m, the saw blade rotational speed decreases as the torque increases.

[0098] When the calculation unit 50 detects that the load has exceeded the first threshold and the saw blade rotation speed has decreased from 5,000 rpm (for example, to 4,800 rpm or below) due to a decrease in motor rotation speed or an increase in motor current to a value slightly above 60 A, the calculation unit 50 transitions to Control C. In Control C, constant current control is performed to keep the motor current constant at a value slightly above 60 A in a delta connection state. In constant current control, the saw blade rotation speed decreases as the torque increases.

[0099] When the calculation unit 50 detects from the decrease in motor rotation speed that the load has exceeded the second threshold and the saw blade rotation speed has fallen to around 2,300 rpm, it switches the coil connection method from delta connection to star connection and transitions to Control B. In Control B, fixed duty control is performed in the star connection state. In Control B, the calculation unit 50 stops the motor 340 when the motor current exceeds the overcurrent threshold.

[0100] The balanced type comparative example 1 shown in Figures 23 and 24 is an example of a medium rotation / medium torque type in which the coil connection method is fixed to star connection and the number of turns is set differently from that of motor 340. In this embodiment, compared to comparative example 1, the saw blade rotation speed can be increased in a torque range of approximately 3 N m or less, improving work efficiency. Note that cutting work is basically possible with a torque range of 2 N m or less.

[0101] 25 and 26 is an example of a high-speed, low-torque motor with the same motor configuration as this embodiment, but with a fixed delta coil connection. Compared to Comparative Example 2, this embodiment can increase the motor speed in a torque range exceeding approximately 3 N m, and can maintain the motor's speed until it stops.

[0102] The high-torque comparative example 3 shown in Figures 27 and 28 is an example of a low-speed, high-torque type with the same motor configuration as this embodiment, but with a fixed star-connected coil connection. Compared to comparative example 3, this embodiment can increase the saw blade rotation speed in the torque range of approximately 3 N m or less, improving work efficiency. Furthermore, compared to comparative example 3, the current flowing through the motor 340 can be reduced.

[0103] Figure 29 is a graph showing the relationship between torque and saw blade rotation speed when the torque of motor 340 in work machine 1C decreases, along with the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to delta connection without switching, the relationship between torque and saw blade rotation speed when the coil wiring method is fixed to star connection without switching, and the relationship between torque and saw blade rotation speed in balanced type comparison example 1.

[0104] When the calculation unit 50 detects that the torque has fallen below 2 N m while control B is being executed by a decrease in motor current or an increase in motor rotation speed, it transitions to control A. The motor current when transitioning from control B to control A is set lower than the motor current when transitioning from control A to control C. This makes it possible to prevent unnecessary control switching. It is advisable to set the motor rotation speed when transitioning from control B to control A 20% or more lower than the motor rotation speed when transitioning from control A to control C.

[0105] According to this embodiment, a suitable layout can be achieved by arranging the relay board 30 inside the intermediate housing 324, which has a relatively large space. In addition, the relay element 31 is laid out close to the control board 311, which makes it easy to organize the wiring and make it compact.

[0106] Control A provides a pleasant feel with constant speed and high rotation speed under light loads, while Control C provides high torque (tenacity) that prevents immediate stalling under heavy loads. Furthermore, by sandwiching Control C between Control A and Control B, constant current control is performed to maintain the motor current constant near the overcurrent threshold in a delta connection before transitioning to a star connection. This prevents a sudden decrease in saw blade rotation speed, ensuring a high saw blade rotation speed under medium loads and improving workability. Furthermore, by preventing a sudden decrease in saw blade rotation speed, poor finish on the cut surface of the workpiece can be prevented. Meanwhile, the decrease in saw blade rotation speed in response to an increase in torque under Control C is clearly noticeable by the user, which is expected to have the effect of making the user aware of a high load. Furthermore, unlike Patent Document 3, there is no need to rapidly switch the coil connection method using a switching element, and the control is simple and preferable.

[0107] Fig. 30 is a state transition diagram of control in Comparative Example 4 in which Control C in Fig. 21 is eliminated. In Comparative Example 4, when the calculation unit 50 detects that the trigger switch 306 is on without detecting any errors in a state in which the motor 340 is stopped (S1), it executes Control A (S32).

[0108] If the load exceeds a first threshold value while control A is being executed, the calculation unit 50 switches the coil wiring method to star connection (S34) and executes control B (S35). If the load becomes equal to or less than a third threshold value that is smaller than the first threshold value while control B is being executed, the calculation unit 50 switches the coil wiring method to delta connection (S36) and returns to control A (S32). If the calculation unit 50 detects any of various errors or if it detects that the trigger switch 306 is off, it stops the motor 340 (S1).

[0109] Fig. 31 is a graph in which the graph of embodiment 4 in Fig. 23 is replaced with the graph of comparative example 4. Fig. 32 is a graph in which the graph of embodiment 4 in Fig. 24 is replaced with the graph of comparative example 4. In comparative example 4, when switching from control A to control B, the saw blade rotation speed drops sharply from around 5,000 rpm to approximately 3,000 rpm. Therefore, compared to embodiment 4, the saw blade rotation speed under a medium load is lower, and workability deteriorates.

[0110] While the present invention has been described above using the embodiments as examples, those skilled in the art will understand that various modifications are possible to the components and processes of the embodiments within the scope of the claims. For example, the specific values ​​of the saw blade rotation speed, motor current, torque, etc., which are used to switch control, are merely examples and can be changed as appropriate. The technical concept of the present invention can be applied to all work machines capable of switching coil connection methods, regardless of the specific types of work machines illustrated in the embodiments. [Explanation of symbols]

[0111] DESCRIPTION OF SYMBOLS 1, 1A to 1C...working machine, 4...reduction mechanism, 5...clutch mechanism, 6...trigger switch, 6a...switch main body, 7...battery pack, 8...clutch dial, 9...sleeve, 10...chuck portion, 11...control board (control circuit board), 13...switching element, 14...insulating sheet, 15...board holder, 16...operation panel, 17...fan, 20...housing, 21...motor housing (body portion), 22...handle housing (handle portion), 22a...rib, 22b...notch, 22c...gap, 23...battery mounting portion, 24...left housing, 25...right housing, 26...opening (intake port), 27...battery connection terminal, 28...terminal holder, 29...elastomer, 30...relay board, 31...relay element (relay), 32...delta connection relay element, 33...star connection relay element, 35...exhaust port, 40...motor, 41...motor shaft (output shaft), 42...rotor core, 43...rotor magnet (permanent magnet), 44...stator core, 45...stator coil, 46...yoke portion, 47...teeth (teeth portion), 50...calculation unit (control unit), 51...control power supply circuit, 52...current detection circuit, 53...switch operation detection circuit, 54...battery type detection circuit, 55... Voltage detection circuit, 56... control signal circuit, 57... rotation position detection circuit, 58... rotation speed detection circuit, 59... operation mode detection circuit, 60... operation mode switch, 61... lighting LED drive circuit, 62... lighting LED, 63... Hall IC (magnetic sensor), 64... inverter circuit, 65... detection resistor, 104... reduction mechanism, 105... hammer, 106... trigger switch, 107... battery pack, 108... anvil, 110... chuck part, 116... operation panel, 117... fan, 120... housing, 121... motor housing (body part), 122... handle housing (handle part), 12 3...battery mounting section, 126...ventilation window (intake port), 127...battery connection terminal, 135...exhaust port, 140...motor, 141...motor shaft, 204...reduction mechanism, 206...operation switch, 207...battery pack, 209...rotating tool (tip tool), 211...control board, 215...board holder, 216...operation panel, 217...fan, 220...housing, 221...motor housing, 222...handle housing, 223...battery mounting section, 224...gear case, 226...ventilation window (intake port), 227...battery connection terminal, 235...exhaust port, 240...motor, 241...motor shaft,306... trigger switch, 307... battery pack, 309... saw blade, 311... control board, 320... housing, 321... motor housing, 322... handle housing, 323... battery mounting section, 324... intermediate housing, 325... gear case (saw cover), 327... battery connection terminal, 328... cover member, 340... motor, 341... motor shaft, 343... rotor magnet (permanent magnet), 345... stator coil.

Claims

1. a motor including a stator having a plurality of teeth, a plurality of coils provided on the teeth and connected to each other by a predetermined connection method, and a rotor rotatable relative to the stator; a tool holder driven by the motor and holding a tool bit; an operation switch for instructing start and stop of the motor; a housing including a motor housing that accommodates the motor, a handle housing in which the operation switch is provided, and a battery mounting portion in which a battery connection terminal is provided; a connection switching unit accommodated in the housing for switching a connection method of the plurality of coils from a first connection method to a second connection method different from the first connection method; a drive circuit unit housed in the housing and driving the motor, A direction parallel to the rotation shaft of the motor is defined as a left-right direction, The direction perpendicular to the left-right direction and parallel to the direction of travel of the work machine is defined as the front-rear direction, If the direction perpendicular to the left-right and front-back directions is the up-down direction, The tool bit extends downward from the housing, The handle housing is located above the motor housing, extends downward, and has the operation switch at its upper end. the battery attachment portion is connected to a lower portion of the handle housing; the connection switching unit is disposed below the drive circuit unit; A work machine characterized by:

2. The work machine according to claim 1, a first substrate located above the motor and having a control unit mounted thereon that controls the drive circuit unit; the connection switching unit is disposed below the first board in the vertical direction and at substantially the same position as the motor; A work machine characterized by:

3. The work machine according to claim 2, the first substrate is equipped with the drive circuit unit that drives the motor under the control of the control unit; A work machine characterized by:

4. The work machine according to claim 2, a second substrate on which the connection switching unit is mounted, the first board is housed in the housing so as to extend in a left-right direction substantially parallel to a motor shaft of the motor and to extend in a front-rear direction intersecting the left-right direction; the second substrate is housed in the housing so as to extend in the front-rear direction and also in a vertical direction intersecting the front-rear direction and the left-right direction; A work machine characterized by:

5. The work machine according to claim 4, The first substrate and the second substrate are disposed at positions where at least a portion of each substrate overlaps with each other in the front-rear direction. A work machine characterized by:

6. a motor including a stator having a plurality of teeth, a plurality of coils provided on the teeth and connected to each other by a predetermined connection method, and a rotor rotatable relative to the stator; a tool holder driven by the motor and holding a tool bit; an operation switch for instructing start and stop of the motor; a housing including a motor housing that accommodates the motor, a handle housing in which the operation switch is provided, and a battery mounting portion in which a battery connection terminal is provided; a connection switching unit for switching a connection method of the plurality of coils from a first connection method to a second connection method different from the first connection method; a drive circuit unit that drives the motor, a first board on which the drive circuit unit is mounted and a second board on which the connection switching unit is mounted are accommodated in the housing so as to overlap when viewed from a direction perpendicular to the plane of the first board; A work machine characterized by:

7. The work machine according to claim 6, The battery mounting portion is located below the motor housing in the up-down direction, the connection switching unit or the second board is accommodated in a range of the housing where the battery mounting unit is provided in a direction intersecting the up-down direction and in which a motor shaft of the motor extends; A work machine characterized by:

8. The work machine according to claim 7, the drive circuit unit or the first board is accommodated in a range of the housing where the battery mounting portion is provided in a direction intersecting the up-down direction and in which a motor shaft of the motor extends; A working machine characterized by:

9. The work machine according to claim 6, The first substrate is positioned above the second substrate. A work machine characterized by:

10. A work machine according to any one of claims 1 to 9, a fan attached to a motor shaft of the motor; an opening communicating the inside and the outside of the housing; the wiring switching unit is disposed inside the housing so as to face the opening. A work machine characterized by:

11. A work machine according to any one of claims 1 to 9, The coil connection method is switchable between a delta connection and a star connection, When the operation switch is operated, the coil connection method is changed to the delta connection to drive the motor, When the load on the motor exceeds a first threshold, a first control is executed to keep the current flowing through the motor constant in the delta connection state or to reduce the rotation speed of the motor in response to an increase in the load on the motor; When the load exceeds a second threshold value that is greater than the first threshold value in the first control, the wiring method of the coils is switched to the star connection. A work machine characterized by:

12. The work machine according to claim 11, In the delta connection state and before the first control state, a constant speed control for maintaining a constant rotation speed of the motor or a fixed duty control is executed. A work machine characterized by:

13. The work machine according to claim 11 or 12, and when a load on the motor becomes equal to or less than a third threshold while the motor is being driven in the star connection, the connection method of the coils is switched to the delta connection. A work machine characterized by:

14. The work machine according to claim 13, The third threshold is smaller than the first threshold. A work machine characterized by:

15. A work machine according to any one of claims 1 to 9, the wiring switching unit has a relay unit, The relay unit includes a first relay unit used when the coil is delta-connected, and a second relay unit used when the coil is star-connected. A work machine characterized by:

16. The work machine according to claim 15, a control unit that controls the drive circuit unit; the control unit is configured to, when switching the coil from the delta connection to the star connection, stop driving the drive circuit unit, then turn off the first relay unit, and then turn on the second relay unit to start driving the drive circuit unit. A work machine characterized by:

17. The work machine according to claim 15, a control unit that controls the drive circuit unit; the control unit is configured to, when switching the coil from the star connection to the delta connection, stop driving the drive circuit unit, then turn off the second relay unit, and then turn on the first relay unit to start driving the drive circuit unit. A work machine characterized by:

18. A work machine according to any one of claims 1 to 9, The coil connection method is switchable between a delta connection and a star connection, When the operation switch is operated, the coil connection method is changed to the delta connection to drive the motor, When the load on the motor exceeds a first threshold, a first control is executed to keep the current flowing through the motor constant in the delta connection state or to reduce the rotation speed of the motor in response to an increase in the load on the motor; When the load exceeds a second threshold value that is greater than the first threshold value in the first control, the wiring method of the coils is switched to the star connection. A work machine characterized by:

19. A work machine according to any one of claims 1 to 9, a control unit that controls the drive circuit unit, the connection switching unit includes a first relay unit used when the coil is delta-connected and a second relay unit used when the coil is star-connected, the control unit is configured to, when switching the coil from the delta connection to the star connection in response to an increase in the load of the motor, stop driving the drive circuit unit, then turn off the first relay unit, and then turn on the second relay unit to start driving the drive circuit unit. A work machine characterized by:

20. A work machine according to any one of claims 1 to 9, a control unit that controls the drive circuit unit, the connection switching unit includes a first relay unit used when the coil is delta-connected and a second relay unit used when the coil is star-connected, the control unit is configured to, when switching the coil from the star connection to the delta connection in response to a decrease in load on the motor, stop driving the drive circuit unit, then turn off the second relay unit, and then turn on the first relay unit to start driving the drive circuit unit. A work machine characterized by:

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