Battery pack and electric working machine

A device of the present disclosure includes an electronic component, a metal plate, a housing, and a wavelength selective heat radiating member. The metal plate is thermally coupled to the electronic component. The housing houses the electronic component and the metal plate. The wavelength selective heat radiating member is mounted on a surface of the metal plate, so as to face an inner side surface of a specific portion of the housing. The wavelength selective heat radiating member is configured to convert thermal energy from the electronic component into heat radiation having a wavelength that penetrates the specific portion of the housing, and emit the heat radiation toward the inner side surface of the specific portion of the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No. 2016-199188 filed in Japanese Patent Office on Oct. 7, 2016, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a battery pack and an electric working machine, and to the corresponding devices.

Japanese Patent Publication No. 4547036 discloses a battery pack that is attached to an electric power tool. The battery pack includes therein an FET (i.e., field-effect transistor), and a heat sink.

SUMMARY

However, in the above-described battery pack, heat from the FET is discharged to the inside of the battery pack through the heat sink. Therefore, heat from the FET will stay in the battery pack, and the heat sink cannot effectively lower the temperature of the FET. It is also possible that poor dissipation of heat increases the temperature in the battery pack. This temperature rise may adversely affect components other than the FET (e.g., other electronic components, battery cells, etc.) in the battery pack. Further, such disadvantages resulting from the poor dissipation of heat can also occur in an electric working machine as well.

In the present disclosure, for example, it is desirable to efficiently release heat from a built-in electronic component to the outside of a housing of a device such as a battery pack, an electric working machine or the like.

A device according to one aspect of the present disclosure includes an electronic component, a metal plate, a housing, and a wavelength selective heat radiating member. The metal plate is thermally coupled to the electronic component. The housing is configured to house the electronic component and the metal plate.

The wavelength selective heat radiating member is mounted on a surface of the metal plate, so as to face an inner side surface of a specific portion of the housing. The wavelength selective heat radiating member is configured to convert thermal energy from the electronic component into heat radiation having a wavelength that penetrates the specific portion of the housing, and emit the heat radiation toward the inner side surface of the specific portion of the housing.

In such a device, the thermal energy from the electronic component is transmitted to the wavelength selective heat radiating member via the metal plate. The thermal energy is converted into heat radiation having a wavelength that can penetrate the specific portion of the housing by the wavelength selective heat radiating member, and emitted toward the inner side surface of the specific portion of the housing. Thus, the thermal energy from the electronic component penetrates the specific portion of the housing in the form of heat radiation, and is released to the outside of the housing.

Therefore, the heat from the electronic component built in the device can be efficiently discharged to the outside of the housing. Heat from the electronic component is removed from the housing, which improves effect of lowering the temperature of the electronic component. Furthermore, since the temperature rise in the housing is reduced, the possibility that the temperature rise affects other components in the housing is also reduced.

A thickness of the specific portion of the housing may be smaller than a thickness of a periphery of the specific portion in the housing. Small thickness improves heat dissipation from the specific portion of the housing. This is because, the smaller the thickness of the specific portion is, the more easily the heat radiation can penetrate the specific portion.

The device may include a wall portion configured to inhibit air of a periphery of the wavelength selective heat radiating member from moving. The wall portion can inhibit the temperature of the wavelength selective heat radiating member from being lowered due to convection in the device. Therefore, it is possible to inhibit a decrease in conversion efficiency of thermal energy into heat radiation by the wavelength selective heat radiating member. The heat dissipation from the specific portion of the housing can be enhanced.

According to one aspect of the present disclosure, a battery pack for an electric working machine may include an electronic component, a metal plate, a housing, and a selective heat radiating member.

In this battery pack, the metal plate is thermally coupled to the electronic component. The housing is configured to house the electronic component and the metal plate. The wavelength selective heat radiating member is mounted on a surface of the metal plate, so as to face an inner side surface of a specific portion of the housing. The wavelength selective heat radiating member is configured to convert thermal energy from the electronic component to heat radiation having a wavelength that penetrates the specific portion of the housing, and emit the heat radiation toward the inner side surface of the specific portion.

According to one aspect of the present disclosure, the housing of the battery pack may include an attachment portion for attachment to the electric working machine. An outer side surface of the specific portion of the housing may be a non-attachment portion of an outer side surface of the housing. According to this battery pack, effect of releasing thermal energy to the outside from the housing (i.e., heat dissipation effect) can be enhanced. This is because the release of thermal energy from the housing is not blocked by the main body of the electric working machine.

According to one aspect of the present disclosure, an electric working machine may be provided that includes an electronic component, a metal plate, a housing, and a selective heat radiating member.

In the electric working machine, the metal plate is thermally coupled to the electronic component. The housing is configured to house the electronic component and the metal plate. The wavelength selective heat radiating member is mounted on a surface of the metal plate, so as to face an inner side surface of a specific portion of the housing. The wavelength selective heat radiating member is configured to convert thermal energy from the electronic component into heat radiation having a wavelength that penetrates the specific portion of the housing, and emit the heat radiation toward the inner side surface of the specific portion.

In such an electric working machine, thermal energy from the electronic component is transmitted to the wavelength selective heat radiating member via the metal plate. The thermal energy is converted into heat radiation having a wavelength that can penetrate the housing by the wavelength selective heat radiating member, and is emitted toward the inner side of the specific portion of the housing. Therefore, the thermal energy from the electronic component penetrates the specific portion of the housing in the form of heat radiation, and is released to the outside of the housing.

Therefore, the heat from the electronic component built in the housing of the electric working machine can be efficiently released to the outside. In other words, heat from the electronic component is inhibited from staying in the electric working machine, and the effect of lowering the temperature of the electronic component is improved. Furthermore, since a temperature rise in the electric working machine can be reduced, the possibility that the temperature rise affects other components than the electronic component in the housing is also reduced.

In the battery pack and/or the electric working machine, a thickness of the specific portion of the housing may be smaller than a thickness of a periphery of the specific portion in the housing. According to the thus constructed battery pack and/or the electric working machine, effect of heat dissipation from the specific portion of the housing is improved. This is because the smaller the thickness of the specific portion is, i.e., the thinner the specific portion is, the more easily the heat radiation penetrates that specific portion.

The battery pack and/or the electric working machine may include a wall portion configured to inhibit air near a periphery of the wavelength selective heat radiating member from moving. According to the thus constructed battery pack and/or the electric working machine, the temperature of the wavelength selective heat radiating member is inhibited from being lowered due to convection in the housing. Therefore, it is possible to inhibit a decrease in conversion efficiency of thermal energy into heat radiation by the wavelength selective heat radiating member. The heat dissipation from the specific portion of the housing can be enhanced.

The housing of the electric working machine may include a portion to which the battery pack is attached. The electric working machine may be configured so that electric power is supplied from the battery pack. In this case, an outer side surface of the specific portion of the housing may be a portion of an outer side surface of the housing different from the portion where the battery pack is attached. According to the electric working machine configured as described above, the effect of releasing thermal energy from the specific portion of the housing to the outside can be enhanced. This is because the release of thermal energy from the housing is not blocked by the battery pack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. Overall Configuration of Grinder

As an example of an electric working machine,FIGS. 1 and 2show a grinder1of the present embodiment. The grinder1is an electric working machine that can perform processing such as grinding, polishing, cutting, etc. on a workpiece.

As shown inFIGS. 1 and 2, the grinder1includes a main body2and a battery pack50. The main body2includes a main housing5, a tool bit6, a cover7, and an operation switch8.

The main housing5, which is a housing of the main body2, is made of resin, and at least partially forms an outer side surface of the main body2. Inside the main housing5, a motor11and a controller13shown inFIG. 3are housed.

The motor11is a power source of the grinder1. The motor11is disposed at a front end of the main housing5(i.e., right side inFIG. 1). The motor11is an electric motor, and may be, but not limited to, a brushless motor, for example.

The controller13(seeFIG. 3) is configured to mainly control the motor11. The controller13is disposed, for example, at a rear end of the main housing5(i.e. left side inFIG. 1).

The rear end of the main housing5is provided with a battery attachment portion9for attaching the battery pack50to the main body2. The battery pack50is configured to be attachable to and detachable from the battery attachment portion9.

As shown inFIG. 4, the battery pack50houses a plurality of batteries52. Specifically, the plurality of batteries52are housed in a battery housing51, which is a housing of the battery pack50. Each of circles shown inFIG. 4corresponds to one of the batteries52. Each of the batteries52is called a battery cell or simply a cell.

Electric power from the batteries52can be provided to the main body2when the battery pack50is attached to the main body2, as shown inFIG. 1. Each electric load such as the motor11, the controller13, or the like in the main body2is configured to operate by the electric power supplied from the batteries52.

The tool bit6is a member for machining a workpiece by being in contact with the workpiece. The tool bit6is rotated and driven by the motor11. Examples of the tool bit6include a grinding wheel, a cutting grindstone, a wire brush and the like.

The cover7is used to protect a user from scattering of broken pieces of the workpiece and the tool bit6caused during processing of the workpiece by the tool bit6. The cover7is formed in a substantially semicircular shape, so as to cover a part of an outer periphery of the tool bit6.

The operation switch8is a switch for rotating the tool bit6. When the user presses the operating switch8, the motor11is driven. Thereby, the tool bit6is rotated and driven.

The controller13operates by electric power of the batteries52to control driving of the motor11. When the operation switch8is pressed by the user, the controller13supplies the electric power to the motor11to rotate the motor11.

2. Heat Dissipation Structure of Housing

As shown inFIG. 3, the controller13includes a printed circuit board (hereinafter referred to as PCB)21and an electronic component23mounted on the PCB21.

Heat is generated from the electronic component23. Therefore, measures to dissipate heat from the electronic component23are necessary. The electronic component23includes, for example, an electronic component related to driving of the motor11. The electronic component23includes, for example, a switching element constituting an inverter that supplies electric power to the motor11. The switching element is, for example, a power MOSFET. The switching element may be other types of transistors. The electronic component23may be an electronic component other than the switching element, with heat generation.

A metal plate25serving as a heat sink is mounted on a surface23aof the electronic component23opposite to the PCB21. The metal plate25is thermally coupled to the electronic component23. Specifically, the PCB21and the metal plate25are disposed so that the surface23aof the electronic component23and a surface of the metal plate25are in contact with each other. Therefore, heat generated in the electronic component23is transmitted to the metal plate25. Material of the metal plate25is, for example, aluminum, but may be a metal such as iron or copper. Between the electronic component23and the metal plate25, an additional member (not shown) such as an elastic material having thermal conductivity may be provided.

A sheet-like wavelength selective heat radiating member27is mounted on a surface25aof the metal plate25opposite to the electronic component23. The heat radiating member27is mounted on the surface25aof the metal plate25, for example, by an adhesive having high thermal conductivity. Thus, thermal energy from the electronic component23is transmitted to the heat radiating member27through the metal plate25.

The heat radiating member27converts the thermal energy from the electronic component23transmitted to the heat radiating member27into heat radiation having a wavelength that can penetrate the main housing5and emits the heat radiation from a surface27aopposite to the metal plate25. The heat radiating member27is, for example, an aluminum sheet on which a large number of micro-cavities which are two-dimensionally arranged are formed. Such a heat radiating member27is also called a metamaterial. In the present embodiment, the heat radiation having a wavelength that can penetrate the main housing5is a heat radiation in the infrared wavelength range (i.e., infrared light), but may be a heat radiation in another wavelength range. Examples of such heat radiating member27is disclosed in Japanese Unexamined Patent Application Publication No. 2014-33062.

The surface27aof the heat radiating member27is arranged so as to face an inner side surface29aof a specific portion29of the main housing5. Thus, the heat radiating member27is mounted on the surface25aof the metal plate25so as to face the inner side surface29aof the specific portion29of the main housing5.

An outer side surface29bof the specific portion29of the main housing5is a portion (a non-attachment portion) of an outer side surface of the main housing5that is different from a portion (an attachment portion) where the battery pack50is attached or may be attached. For example, the upper side inFIG. 3corresponds to the right side inFIG. 1. As shown inFIG. 1, the specific portion29of the main housing5is, for example, an upper portion near the rear end of the main housing5. The upper side inFIG. 1is the upper side when the grinder1is horizontally used.

A thickness t1of the specific portion29as shown inFIG. 3is smaller than a thickness t2of the other portion in the main housing5including a periphery of the specific portion29. Specifically, a recess31that can house the heat radiating member27is formed inside the specific portion29of the main housing5. A concave surface of the recess31corresponds to the inner side surface29afacing the heat radiating member27.

The metal plate25is disposed so as to be brought into contact with an inner side surface5aof a periphery of the recess31in the main housing5. Therefore, the metal plate25is disposed so that the main housing5is brought into contact with the portion25bof the surface25aof the metal plate25of a periphery of the heat radiating member27. For this reason, the heat radiating member27is brought into a substantially sealed state in the recess31. That is, a wall portion31aof the recess31perpendicular to the surface25aof the metal plate25functions to hinder air of the periphery of the heat radiating member27from moving. There may be a slight gap between the portion25bof the surface25aof the metal plate25and the inner side surface5aof the periphery of the recess31in the main housing5.

A distance L1between the heat radiating member27and the inner side surface29ais configured to be as small as possible. For example, the distance L1corresponds to a tolerance range required for assembling, which is 0.5 mm or less.

3. Effect of Heat Dissipation Structure of Housing

According to the heat dissipation structure of the main housing5as described above, the following effects are achieved.

(3a) The thermal energy from the electronic component23is transmitted to the heat radiating member27via the metal plate25. The thermal energy is converted into heat radiation having a wavelength that can penetrate the main housing5by the heat radiating member27and is emitted toward the inner side surface29aof the specific portion29of the main housing5. Therefore, the thermal energy from the electronic component23penetrates the specific portion29of the main housing5in the form of heat radiation, and is released to the outside of the main housing5.

Therefore, the heat from the electronic component23built in the main housing5can be efficiently released to the outside of the main housing5. Therefore, the heat from the electronic component23is removed from the grinder1. Accordingly, effect of lowering the temperature of the electronic component23can be improved. Furthermore, temperature rise in the grinder1is inhibited. Therefore, the possibility that the temperature rise affects other components than the electronic component23is also reduced.

(3b) The thickness t1of the specific portion29of the main housing5is smaller than the thickness t2of the portion other than the specific portion29of the main housing5. Therefore, effect of releasing the thermal energy from the specific portion29of the main housing5to the outside (i.e., heat dissipation effect) can be enhanced. This is because the smaller the thickness t1of the specific portion29is, the more easily the heat radiation penetrates the specific portion29.

(3c) The wall portion31aof the main housing5hinders the air of the periphery of the heat radiating member27from moving. Therefore, the temperature of the heat radiating member27can be inhibited from being lowered due to convection in the grinder1(i.e., in the main housing5). As a result, it is possible to inhibit a decrease in conversion efficiency of thermal energy into heat radiation by the heat radiating member27. High conversion efficiency improves the heat dissipation from the specific portion29of the main housing5.

(3d) The outer side surface29bof the specific portion29of the main housing5is a portion (a non-attachment portion) of the outer side surface of the main housing5that is different from the portion (the attachment portion) where the battery pack50is attached or may be attached. Therefore, release of thermal energy from the main housing5is not blocked by the battery pack50. Such a heat dissipation structure can enhance the heat dissipation from the specific portion29of the main housing5. In the main housing5, the specific portion29facing the heat radiating member27is not limited to the portion of the wall of the main housing5indicated by a reference numeral “29” inFIG. 1.

(3e) The distance L1between the heat radiating member27and the specific portion29of the main housing5is made as small as possible. The small distance L1improves the heat dissipation from the specific portion29.

4. Heat Dissipation Structure of Battery Pack

As shown inFIG. 4, in the battery housing51, the above-described plurality of batteries52are housed. Furthermore, a monitoring control circuit53is also housed in the battery housing51. The battery housing51is made of resin. The battery housing51at least partially forms an outer side surface of the battery pack50.

InFIG. 4, an upper surface of the battery housing51is a surface facing the main body2when the battery housing51is attached to the main body2of the grinder1. Therefore, the upper side inFIG. 4corresponds to the right side inFIG. 1. The left side inFIG. 4corresponds to the upper side inFIG. 1, for example. Terms “up”, “down”, “left”, and “right” used in the description related to the battery pack50below correspond to directions shown inFIG. 4.

The monitoring control circuit53operates by electric power of the batteries52. The monitoring control circuit53is configured, for example, to monitor electric current into and out of the batteries52(i.e., charging and discharging current), and/or a voltage of the batteries52. The monitoring control circuit53, when abnormality occurs in the electric current and/or voltage to be monitored, notifies the controller13of the grinder1of the occurrence of abnormality, and/or, disconnects a charge and discharge path of the batteries52. The monitoring control circuit53includes a PCB61, and an electronic component63mounted on the PCB61.

The electronic component63may include, for example, an electronic component associated with power supply. The electronic component63, for example, includes a switching element provided in the charge and discharge path of the batteries52to switch between connection and disconnection of the charge and discharge path. The switching element is, for example, a power MOSFET. However, the switching element may be other types of transistors. The electronic component63may be an electronic component other than the switching element. The electronic component63, for example, may be a current detection resistor provided in the charge and discharge path of the batteries52. Heat is generated from the electronic component63.

As shown inFIG. 4, the PCB61of the monitoring control circuit53is provided on an upper side of the batteries52in the battery housing51. The electronic component63is mounted on an upper surface of the PCB61, namely, a surface61aof the PCB61opposite to the batteries52.

A metal plate65serving as a heat sink is mounted on the surface63aof the electronic component63opposite to the PCB61. Specifically, in the battery housing51, the PCB61and the metal plate65are fixed so that the surface63aof the electronic component63and a surface of the metal plate65are brought into contact with each other. Therefore, the metal plate65is thermally coupled to the electronic component63. Thus, heat generated in the electronic component63is transmitted to the metal plate65. Material of the metal plate65is, for example, aluminum, but may be a metal such as iron or copper. Between the electronic component63and the metal plate65, an additional member (not shown) such as an elastic material having thermal conductivity may be provided.

The metal plate65is formed by bending a flat metal plate at a substantially right angle. The metal plate65includes a first flat plate portion66, and a second flat plate portion67. The first flat plate portion66is a flat plate-shaped portion of the metal plate65which extends in parallel to the PCB61. The first flat plate portion66is in contact with the electronic component63. The second flat plate portion67is a plate-like portion of the metal plate65which extends downward from a left end of the first flat plate portion66. The second flat plate portion67is disposed substantially parallel to a specific portion69which is a part of a left side wall of the battery housing51.

In other words, in the battery housing51, the metal plate65is fixed to the PCB61through the electronic component63so that the first flat plate portion66of the metal plate65contacts the electronic component63and the second flat plate portion67of the metal plate65is substantially parallel to the specific portion69of the battery housing51.

A heat radiating member70similar to the heat radiating member27is attached to a surface67aof the second flat plate portion67on the side of the specific portion69, i.e., a surface facing an inner side surface69aof the specific portion69. In other words, in the battery pack50, the heat radiating member70is mounted on the surface67aof the metal plate65so as to face the inner side surface69aof the specific portion69in the battery housing51.

Thermal energy from the electronic component63is transmitted to the heat radiating member70via the metal plate65. The heat radiating member70converts the thermal energy transmitted from the electronic component63via the metal plate65into heat radiation having a wavelength that can penetrate the battery housing51and emits the heat radiation toward the inner side surface69aof the specific portion69in the battery housing51. The heat radiation is a heat radiation in the infrared wavelength range (i.e., infrared light), but may be a heat radiation in another wavelength range. The heat radiating member70may be mounted on the surface67aof the metal plate65, for example, by an adhesive having high thermal conductivity.

An outer side surface69bof the specific portion69of the battery housing51is a portion of an outer side surface of the battery housing51different from the portion attached to the main body2of the grinder1.

Further, a thickness t3of the specific portion69that faces the heat radiating member70in the battery housing51is smaller than a thickness t4of the other portion including a periphery of the specific portion69of the battery housing51.

Specifically, in the battery housing51, a recess71having an area larger than the heat radiating member70is formed inside the specific portion69. A concave surface of the recess71is the inner side surface69afacing the heat radiating member70.

Further, a surface70aof the heat radiating member70facing the specific portion69is on the same plane as the inner side surface51aof a periphery of the recess71of the battery housing51. In other words, this is a substantially “co-planar arrangement.”

Therefore, a wall portion71aof the recess71perpendicular to the surface67aof the second flat plate portion67of the metal plate65functions to hinder air of a periphery of the heat radiating member70from moving. However, the surface70aof the heat radiating member70may not be on the same plane as the inner side surface51aof the battery housing51. In other words, a part in the thickness direction of the heat radiating member70may enter the recess71, creating a “penetrating arrangement.” A portion67bof the surface67aof the second flat plate portion67of the periphery of the heat radiating member70may be in contact with the inner side surface51aof the battery housing51, creating a “peripheral contact arrangement.”

The heat radiating member70and the inner side surface69aare configured so that a distance L2between the heat radiating member70and the inner side surface69ais as small as possible. For example, the distance L2is a tolerance range required for assembling, which is specifically 1 mm or less.

5. Effect by Heat Dissipation Structure of Battery Pack

According to the heat dissipation structure of the battery pack50as described above, the following effects are achieved.

(5a) The thermal energy from the electronic component63is transmitted to the heat radiating member70through the metal plate65. The thermal energy is converted to heat radiation having a wavelength that can penetrate the battery housing51by the heat radiating member70, and emitted toward the inner side surface69aof the specific portion69of the battery housing51. Therefore, the thermal energy, in the form of heat radiation, penetrates the specific portion69of the battery housing51, and is discharged to the outside of the battery housing51.

Therefore, the heat from the electronic component63built in the battery housing51can be efficiently discharged to the outside of the battery housing51. Thus, the heat from the electronic component63is inhibited from staying in the battery pack50. The effect of lowering the temperature of the electronic component63is improved. Furthermore, temperature rise in the battery pack50is inhibited. Therefore, the possibility that the temperature rise affects other components than the electronic component63is also reduced.

(5b) The thickness t3of the specific portion69of the battery housing51is smaller than the thickness t4of the other portion of the battery housing51. Therefore, the effect of releasing the thermal energy to the outside from the specific portion69of the battery housing51(i.e., heat dissipation effect) can be enhanced. This is because the smaller the thickness t3of the specific portion69is, the more easily the heat radiation penetrates the specific portion69.

(5c) The wall portion71aof the battery housing51hinders the air of the periphery of the heat radiating member70from moving. Therefore, the temperature of the heat radiating member70can be inhibited from being lowered by convection inside the battery pack50(i.e., inside the battery housing51). As a result, it is possible to maintain a high conversion efficiency of thermal energy to heat radiation by the heat radiating member70. High conversion efficiency improves the heat dissipation from the specific portion69of the battery housing51.

(5d) The outer side surface69bof the specific portion69of the battery housing51is a portion of the outer side surface of the battery housing51different from the portion attached to the main body2of the grinder1. Therefore, release of thermal energy from the battery housing51is not blocked by the main body2. Such a heat dissipation structure can enhance the heat dissipation from the specific portion69of the battery housing51. In the battery housing51, the specific portion69that faces the heat radiating member70may be a part of a lower wall or a part of a right wall of the battery housing51inFIG. 4.

(5e) The distance L2between the heat radiating member70and the specific portions69of the battery housing51is made as small as possible. Small distance L2improves the heat dissipation from the specific portion69.

6. Other Embodiments

An embodiment of the present disclosure has been described in the above, but the present disclosure is not limited to the above embodiment and can be modified in various ways.

For example, the present disclosure can be applied to various electric working machines such as an electric hammer, an electric hammer drill, an electric drill, an electric driver, an electric wrench, an electric reciprocating saw, an electric jigsaw, an electric cutter, an electric chainsaw, an electric plane, an electric circular saw, an electric nailer including an electric tacker, an electric hedge trimmer, an electric lawn mower, an electric lawn trimmer, electric grass cutter, an electric cleaner, an electric blower and the like.

Further, a plurality of function of a single component in the above embodiment may be implemented by a plurality of components, and one of the function of a single component may be implemented by a plurality of components. Further, a plurality of functions of a plurality of components may be implemented by a single component, and one of the functions implemented by a plurality of components may be implemented by a single component. Also, part of the configuration of the above embodiment may be omitted. Any aspect included in the technical idea specified from the language as set forth in the appended claims is an embodiment of the present disclosure. The present disclosure can also be implemented in various forms such as a heat dissipation method of a battery pack, a heat dissipation method of an electric working machine, or the like.