JP6722543B2 - Electric tool - Google Patents

Description

The present invention relates to an electric power tool configured to drive a tip tool using a motor as a drive source.

2. Description of the Related Art An electric power tool that drives a tip tool using a motor as a drive source is known. In such an electric tool, the motor may be overheated due to overload, and if the motor is continued to be used as it is, the motor may eventually burn out. Therefore, for example, as disclosed in Patent Document 1, the heat storage amount of the motor is calculated from the current value of the motor and the drive time and stop time of the tool, and when the heat storage amount exceeds a predetermined threshold value. An electric power tool that performs a protective operation for a motor is known.

JP 2002-354886 A

In the above power tool, whether or not to perform the motor protection operation is determined by comparing the heat storage amount of the motor with a predetermined threshold value. On the other hand, since the load is applied intermittently and irregularly, the actual temperature rise history of the motor is complicated. Therefore, depending on the set threshold value, the motor may be burned before the protection operation is performed, or the motor protection operation may be started at a time when the possibility of the burnout is low. Therefore, there is a demand for a technique capable of more appropriately detecting the possibility of motor burnout and controlling the drive of the motor.

It is an object of the present invention to provide a technique capable of more appropriately detecting the possibility of burnout of a motor and controlling the drive of the motor in an electric tool using a motor as a drive source.

According to one aspect of the invention, there is provided a power tool configured to drive a tip tool. This electric power tool is provided with a housing, a motor arranged in the housing, a detector configured to detect a specific gas generated in response to an overheated state of the motor, and a detection result obtained by the detector. And a controller configured to limit the number of rotations of the motor.

The motor may fall into an overheated state due to various causes such as overload, deterioration over time, environmental temperature, and poor cooling. It is known that when a motor falls into an overheated state, a specific gas is generated corresponding to this overheated state. The detection unit can detect that the specific gas is actually generated in response to the overheated state of the motor. For this reason, the possibility of burnout of the motor can be detected more appropriately than in the case where the amount of accumulated heat of the motor whose temperature changes intricately is calculated from the current value. The control unit can protect the motor by limiting the rotation speed of the motor according to the detection result of the detection unit.

The "power tool" here is also called "power tool" and refers to general tools that use electric power as power, such as tools used for work (eg grinders, circular saws, chainsaws) and gardening. Tools (eg, mowers, hedge clippers, etc.).

The motor may be a DC motor or an AC motor. Further, the motor may be a motor having a brush or a so-called brushless motor having no brush.

As an example of "a specific gas generated in response to an overheated state of a motor", typically, when a motor is placed in an overheated state, a coating of a winding of a motor and a varnish that insulates or fixes the winding. And a gas generated by at least one of the windings themselves being excessively heated and oxidized or decomposed. As a method for detecting the specific gas by the detection unit, any method may be adopted from various known methods including a semiconductor method, a catalytic combustion method, an electrochemical method, a solid electrolyte method, and an infrared method. The detector may include not only so-called gas sensors but also so-called odor sensors and smoke sensors.

The “limitation of the number of rotations of the motor” by the control unit includes both reducing the number of rotations of the motor and making the number of rotations zero (that is, stopping driving of the motor).

According to one aspect of the invention, the power tool may further include a fan disposed within the housing and driven by the motor. The fan is configured to form an air flow that flows through the housing in a predetermined path, and the detection unit may be arranged on the path of the air flow. According to this aspect, the specific gas included in the airflow and flowing can be effectively detected by the detection unit arranged on the path of the airflow.

According to one aspect of the present invention, the detection unit may be arranged in a downstream region including a portion on the downstream side of the motor in the direction of the air flow in the path of the air flow. It is assumed that the specific gas generated by the specific gas corresponding to the overheated state of the motor flows downstream of the motor in the air flow path. Therefore, by providing the detection unit in the downstream region, it is possible to detect the specific gas more effectively.

The electric power tool according to an aspect of the present invention may include a plurality of detection units. In this case, the control unit may be configured to limit the rotation speed according to the detection results of the plurality of detection units. According to this aspect, the detection accuracy of the specific gas can be increased by using the detection results of the plurality of detection units.

According to one aspect of the present invention, the plurality of detection units may include a downstream detection unit and an upstream detection unit. The downstream-side detection unit is arranged in a downstream-side area including a portion on the downstream side of the motor in the direction of the airflow in the airflow path. The upstream side detection unit is arranged in an upstream side region including a portion on the upstream side of the motor in the direction of the air flow in the path of the air flow. The control unit may be configured to limit the rotation speed according to the detection results of both the upstream detection unit and the downstream detection unit. It is assumed that the specific gas generated corresponding to the overheated state of the motor flows downstream of the motor in the air flow path and is detected by the downstream detection unit. On the other hand, when the specific gas is also detected by the upstream detection unit, the specific gas may not be generated in response to the overheated state of the motor. Therefore, by utilizing the detection results of both the upstream detection unit and the downstream detection unit, it is possible to suppress the possibility of erroneous detection of the possibility of burnout of the motor and to more appropriately control the drive of the motor.

In one aspect of the present invention, the control unit limits the rotation speed when the concentration of the specific gas detected by the downstream detection unit is higher than the concentration of the specific gas detected by the upstream detection unit. May be configured. If the concentration of the specific gas detected by the downstream detection unit is the same as or lower than the concentration of the specific gas detected by the upstream detection unit, the specific gas will be overheated by the motor. It is assumed that it did not occur in response, but existed around the power tool due to external factors. On the other hand, when the concentration of the specific gas detected by the downstream detection unit is higher than the concentration of the specific gas detected by the upstream detection unit, the specific gas is generated according to the overheated state of the motor. Since it is assumed that the motor is protected, the motor can be protected by limiting the rotation speed of the motor.

In one aspect of the present invention, the control unit is configured such that the difference between the concentration of the specific gas detected by the downstream detection unit and the concentration of the specific gas detected by the upstream detection unit is a preset tolerance. When it exceeds, the number of rotations may be limited. According to this aspect, when the concentration of the specific gas detected on the downstream side of the motor is somewhat higher than the amount detected on the upstream side, the rotation speed of the motor is limited. It is possible to reduce the possibility of being damaged.

According to one aspect of the present invention, the plurality of detection units may include a first gas detection unit and a second gas detection unit. The first gas detection unit is configured to detect, as the specific gas, the first gas generated corresponding to the first state in which the degree of overheating of the motor is lower in the overheating state. The second gas detection unit detects, as the specific gas, a second gas different from the first gas, which is generated corresponding to the second state in which the degree of overheating is higher than the first state among the overheated states. Is configured to. The control unit may be configured to limit the rotation speed according to the detection results of the first gas detection unit and the second gas detection unit. By providing the first gas detector and the second gas detector, the degree of overheating of the motor can be detected. Therefore, the control unit can perform appropriate control according to the degree of overheating of the motor.

The electric power tool according to an aspect of the present invention may further include a first operation unit configured to receive a drive instruction for normally driving the motor in response to an external operation by an operator. The control unit maintains the limited state despite the drive instruction when a new drive instruction is received from the first operation unit when the motor is placed in the limited state in which the rotation speed is limited. It may be configured as follows. According to this aspect, it is possible to maintain the motor in the restricted state so as not to bring the motor into a state closer to burning.

The electric power tool according to one aspect of the present invention may further include a second operation unit configured to receive an instruction to release the restriction on the rotation speed of the motor by the control unit in response to an external operation by an operator. The control unit may be configured to cancel the restricted state when the second operation unit receives a cancellation instruction while the motor is in the restricted state. According to this aspect, even if the motor is once placed in the restricted state, if the operator confirms that the restricted state can be released and operates the second operation unit, the electric tool is returned to the normal state again. Can be used. For example, if the motor is placed in a restricted state due to some malfunction, or if overheating subsides after being placed in a restricted state, the operator can take appropriate action depending on the situation, improving convenience. ..

According to an aspect of the present invention, the control unit limits the motor when the concentration of the specific gas detected by the detection unit is lower than a preset allowable concentration when the motor is placed in the limit state. It may be configured to release the state. Even if the motor is once placed in the restricted state, it is assumed that the overheated state of the motor has subsided unless the specific gas exceeds the allowable concentration and is thereafter detected. According to this aspect, in such a case, the restricted state is automatically released, so that convenience is improved.

The electric power tool according to an aspect of the present invention may further include a notification unit that notifies information corresponding to the detection result. According to this aspect, the worker can recognize the condition of the motor (such as the possibility of burning) based on the information according to the detection result, and take measures to reduce the load if necessary. it can.

According to one aspect of the present invention, the first permissible concentration and the second permissible concentration higher than the first permissible concentration may be preset for the specific gas. In this case, when the detection unit detects the specific gas that exceeds the first allowable concentration, the notification unit notifies the first information indicating that the specific gas has exceeded the first allowable concentration. The control unit may be configured to limit the rotation speed when the detection unit detects a specific gas exceeding the second allowable concentration. According to this aspect, the first information is notified, so that the worker can recognize that the motor has a high load and can take measures to reduce the load. Even if the first information is notified, if the specific gas increases and exceeds the second allowable concentration, the control unit can protect the motor by limiting the rotation speed of the motor. it can. That is, according to this aspect, the rotation speed of the motor is limited only when the measure for reducing the load is not taken after the concentration of the specific gas exceeds the first allowable concentration. Therefore, it is possible to prevent unnecessary protection operation of the motor.

According to one aspect of the present invention, the notification unit, when the detection unit detects the specific gas exceeding the second allowable concentration, indicates that the specific gas exceeds the second allowable concentration. The information may be notified in a manner different from that of the first information. By informing the second information in a mode different from that of the first information, the operator can easily recognize that the possibility of burnout of the motor has increased.

The electric power tool according to an aspect of the present invention may further include a notification unit that notifies information corresponding to the detection result. In this case, the first permissible gas concentration for the first gas and the second permissible gas concentration for the second gas may be set in advance. Furthermore, when the first gas detection unit detects the first gas that exceeds the first gas allowable concentration, the notification unit indicates that the first gas has exceeded the first gas allowable concentration. The control unit may be configured to notify the information, and may be configured to limit the rotation speed when the detection unit detects the second gas that exceeds the second allowable gas concentration. According to this aspect, the first information is notified, so that the worker can recognize that the motor has a high load and can take measures to reduce the load. Despite the notification of the first information, if the degree of overheating becomes higher and the detected concentration of the second gas exceeds the allowable concentration of the second gas, the control unit rotates the motor. By limiting the number, the motor can be protected. That is, according to this aspect, the rotation speed of the motor is limited only when the measure for reducing the load is not taken after the first gas exceeds the first allowable gas concentration. Therefore, it is possible to prevent unnecessary protection operation of the motor.

According to one aspect of the present invention, when the detection unit detects the second gas that exceeds the second allowable gas concentration, the second gas indicates that the second gas has exceeded the second allowable gas concentration. The information may be notified in a manner different from that of the first information. By informing the second information in a mode different from that of the first information, the operator can easily recognize that the possibility of burnout of the motor has increased.

It is a longitudinal cross-sectional view of the grinder according to the first embodiment. It is a block diagram which shows the electric constitution of a grinder. It is a flow chart of drive control processing concerning a first embodiment. It is a flowchart of the 1st modification of 1st embodiment. It is a flowchart of the 2nd modification of 1st embodiment. It is a flowchart of a 2nd modification and is a continuation of FIG. It is a longitudinal cross-sectional view of the grinder which concerns on 2nd embodiment. It is a block diagram which shows the electric constitution of a grinder. It is a flow chart of drive control processing concerning a second embodiment. It is a flowchart of the modification of 2nd embodiment. It is a longitudinal cross-sectional view of a circular saw according to a third embodiment. It is a block diagram which shows the electric constitution of a circular saw. It is a flow chart of drive control processing concerning a third embodiment. It is a flowchart of the drive control process which concerns on 3rd embodiment, and is a continuation of FIG. It is a cross-sectional view of the chain saw which concerns on 4th embodiment. It is a longitudinal cross-sectional view of a hammer drill according to a fifth embodiment. It is a longitudinal cross-sectional view of a hammer drill according to a sixth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the following embodiment, a plurality of types of electric tools are exemplified.

[First embodiment]
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 3. In the present embodiment, as an example of an electric power tool, a grinder 1 configured to rotationally drive a disc-shaped tip tool around a predetermined rotation axis is illustrated. A grindstone, a rubber pad, a brush, a blade, or the like is prepared as a tip tool that can be mounted on the grinder 1. The operator selects an appropriate tip tool according to the desired machining operation and attaches it to the grinder 1. The grinder 1 is capable of performing processing operations such as grinding, polishing, and cutting on a workpiece by rotating the tip tool. In the description of the present embodiment, an example in which a grindstone 81 is attached to the grinder 1 is used as the tip tool.

First, the overall configuration of the grinder 1 will be described with reference to FIG. As shown in FIG. 1, the outer contour of the grinder 1 is formed by an elongated hollow main body housing 100. The main body housing 100 may be configured as one housing by connecting a plurality of parts (motor housing, gear housing, etc.). At one end of the main body housing 100 in the long axis direction, a spindle 130 for driving the grindstone 81 has a rotation axis A1 intersecting the long axis direction of the main body housing 100 (more specifically, a direction that is substantially orthogonal). It is arranged to extend to. One end of the spindle 130 is exposed to the outside from the main body housing 100, and is configured as a tool mounting portion 131 to which the grindstone 81 can be attached and detached.

Hereinafter, for convenience of description, the extending direction of the rotation axis A1 of the spindle 130 is defined as the vertical direction of the grinder 1, and the one end side where the tool mounting portion 131 is provided is defined as the lower side. Further, the direction orthogonal to the rotation axis A1 of the spindle 130 and corresponding to the long axis of the main body housing 100 is defined as the front-rear direction of the grinder 1, and one end side where the spindle 130 is arranged in the main body housing 100 is defined as the front side. To do.

The front side portion of the main body housing 100 mainly constitutes a motor 110, a transmission mechanism 120, and a drive portion housing portion 101 that houses the spindle 130. In the present embodiment, the motor 110 is configured as a DC brushless motor, and rotationally drives the output shaft 111 with the electric power supplied from the rechargeable battery 90. The motor 110 is arranged behind the spindle 130 in the main body housing 100. Further, the motor 110 is arranged such that the rotation axis of the output shaft 111 extends orthogonally to the rotation axis A1 of the spindle 130 in the front-rear direction. The output shaft 111 is rotatably supported by bearings 112 and 113 on the front and rear sides of the motor 110.

A fan 117 for cooling the motor 110 is fixed to the output shaft 111 between the main body portion (stator and rotor) of the motor 110 and the front bearing 112. The fan 117 is configured to form an air flow that flows through the main body housing 100 in a predetermined path. Although not shown in detail, the main body housing 100 is formed with an intake port and an exhaust port that communicate the inside and outside of the main body housing 100. When the fan 117 is rotated along with the driving of the motor 110, the fan 117 flows into the main body housing 100 from an intake port rearward of the motor 110, and flows forward in the vicinity of the motor 110 as indicated by an arrow in the figure. After that, an airflow that flows out from the exhaust port in front of the motor 110 is formed. This airflow functions as cooling air for the motor 110.

A gas sensor 140 is arranged on the path of the air flow formed by the fan 117. More specifically, the gas sensor 140 is provided in an area including a portion on the downstream side of the motor 110 (hereinafter referred to as a downstream area) in the flow direction of the airflow flowing in the main body housing 100 as indicated by an arrow in the drawing. It is arranged. The term “downstream of the motor 110” as used herein refers to a downstream side of a portion of the motor 110 arranged in the uppermost stream in the flow direction of the airflow (in this embodiment, the rear end of the motor 110). Means In the present embodiment, the gas sensor 140 is fixed inside the main body housing 100 near the front end of the motor 110.

The gas sensor 140 is configured to detect a specific gas generated corresponding to the overheated state of the motor 110. In general, when the motor 110 is placed in an overheated state, the winding insulation film (for example, polyester resin) for winding or insulation of the winding is fixed before the winding of the motor 110 is short-circuited or broken. The varnish (for example, epoxy resin) and other accessories are heated and oxidized or decomposed to generate a specific gas. It is believed that as the concentration of this particular gas increases, the possibility of motor burnout increases. Therefore, in the present embodiment, in order to detect the possibility of motor burnout, a gas sensor capable of detecting a specific gas (for example, carbon monoxide, toluene, hydrocarbons, styrene, acrylonitrile) generated from the insulating coating or varnish. 140 has been adopted. From this, it is preferable that the gas sensor 140 is arranged in a region of the winding of the motor 110 that includes a portion on the downstream side of a portion arranged on the uppermost stream in the airflow direction.

The method of detecting a specific gas by the gas sensor 140 is not particularly limited, but in the present embodiment, a semiconductor gas sensor that can output the amount of change in the resistance value of the semiconductor as a voltage is used as the gas sensor 140. In this case, the magnitude of the voltage value detected by the gas sensor 140 corresponds to the magnitude of the concentration of the specific gas. Therefore, in the control process by the controller 170, which will be described later, it is possible to determine the presence or absence of the specific gas by setting the threshold value for the voltage value. The gas concentration may be represented by a unit volume ratio (unit is ppm or the like) or by weight (unit is mg/m ³ or the like).

The spindle 130 is arranged on the front side of the motor 110 so as to extend in the vertical direction, and is rotatably supported by bearings 132 and 133. The tool mounting portion 131 protruding downward from the front end portion of the main body housing 100 is configured to sandwich the grindstone 81 from the upper side and the lower side by the two flange portions and fix the grindstone 81 to the spindle 130. Since the configuration of the tool mounting portion 131 is well known, detailed description thereof is omitted here.

The transmission mechanism 120 is configured to reduce the rotation of the output shaft 111 of the motor 110 and then transmit the rotation to the spindle 130. The transmission mechanism 120 of the present embodiment is configured as a reduction gear mechanism including a small bevel gear fixed to the front end of the output shaft 411 and a large bevel gear fixed to the upper end of the spindle 130 and meshing with the small bevel gear. Has been done. The rotation of the motor 110 is decelerated by the transmission mechanism 120 and transmitted to the spindle 130. As a result, the grindstone 81 fixed to the tool mounting portion 131 is rotationally driven together with the spindle 130.

A wheel cover 138 is fixed to the lower end portion of the front end portion of the main body housing 100 to prevent the fragments and dust of the work piece generated in the working operation from scattering and protect the operator from the grindstone 81. .. Since the structure of the wheel cover 138 is well known, detailed description thereof is omitted here.

A rear side portion of the main body housing 100 (a portion rearward of a portion where the motor 110 is housed) constitutes a grip portion 103 that is gripped by an operator. The grip section 103 is provided with a first operation section 150 and a second operation section 160 configured to receive an instruction in response to an external operation by an operator.

The first operation unit 150 includes a trigger 151 and a trigger switch 152. The trigger 151 is provided at the lower end of the grip 103 and is configured to be capable of being pressed from the outside by an operator. The trigger switch 152 is housed in the grip 103. The trigger switch 152 switches between an ON state (a state in which a drive instruction for instructing normal driving of the motor 110 is received) and an OFF state (a state in which no drive instruction is received) according to a pressing operation on the trigger 151. To be More specifically, the trigger switch 152 is maintained in the OFF state in the initial state where the pressing of the trigger 151 is released, and outputs a signal indicating the OFF state, while the operator pushes the trigger 151. Is switched to the ON state and outputs a signal indicating the ON state.

The second operation unit 160 includes a reset button 161 and a reset switch 162 (see FIG. 2). The reset button 161 is provided at the upper rear end portion of the grip portion 103 and is configured to be capable of being pressed from the outside by an operator. The reset switch 162 is housed in the grip portion 103. The reset switch 162 is in an ON state (a state in which a release instruction for releasing a drive inhibition state of the motor 110, which will be described later, is received) and an OFF state (a state in which the release instruction is not received) in response to a pressing operation on the reset button 161. Can be switched between. More specifically, the reset switch 162 is normally maintained in the OFF state and outputs a signal indicating the OFF state, while the reset switch 162 is brought into the ON state only when the operator presses the reset button 161 to change the ON state. It is configured to output the indicated signal.

At the rear end of the grip portion 103, a battery mounting portion 105 configured such that the battery 90 can be attached and detached is provided. A controller 170 that controls driving of the motor 110 is arranged in the rear end portion of the grip portion 103. A warning lamp 180 for notifying the possibility of burnout of the motor 110 is provided adjacent to the controller 170 and the reset button 161 at the upper rear end of the grip 103. In this embodiment, the warning lamp 180 is composed of an LED.

Next, the electrical configuration of the grinder 1 will be described with reference to FIG. As shown in FIG. 2, the controller 170 that controls driving of the motor 110 includes a control circuit 171 and a drive circuit 173. In the present embodiment, the control circuit 171 is composed of a microcomputer including a CPU, ROM, RAM and the like. The drive circuit 173 is configured to supply electric power from the battery 90 mounted on the battery mounting portion 105 and cause a current to flow through the winding of the motor 110, and operates according to the control signal output from the control circuit 171. .. The control circuit 171 operates by receiving power supply from the battery 90 via a power supply circuit (not shown).

The gas sensor 140, the trigger switch 152, the reset switch 162, and the warning lamp 180 are electrically connected to the control circuit 171. The gas sensor 140 outputs a signal indicating a voltage value (hereinafter, referred to as a detected value) corresponding to the detected concentration of the specific gas. The trigger switch 152 and the reset switch 162 output signals corresponding to the ON state and the OFF state, respectively. The control circuit 171 controls the lighting of the warning lamp 180 by a control signal.

Hereinafter, the drive control processing of the grinder 1 executed by the controller 170 (more specifically, the CPU of the control circuit 171) will be described with reference to FIG. The drive control process of FIG. 3 is started when the battery 90 is mounted in the battery mounting unit 105 to start the power supply to the grinder 1, and is ended when the power supply is stopped. It should be noted that in the following description, each “step” in the process is abbreviated as “S”.

As shown in FIG. 3, first, the controller 170 acquires the detection value of the gas sensor 140 and determines whether the detection value exceeds a threshold value (S101). The threshold value is set in advance as a value corresponding to an upper limit concentration that is allowed as a value that does not reach the burnout of the motor 110 with respect to the concentration of the specific gas. Therefore, the detection value exceeding the threshold value is equivalent to the concentration of the specific gas detected by the gas sensor 140 exceeding the upper limit concentration. The threshold may be stored in advance in the ROM included in the control circuit 171, for example.

When the detected value does not exceed the threshold value (S101: NO), the controller 170 monitors the signal from the trigger switch 152, and waits while the trigger switch 152 is in the OFF state, that is, while not receiving the drive instruction. Yes (S102: NO, S102). When the trigger 151 is pressed by the operator and the trigger switch 152 is switched to the ON state, that is, the state in which the drive instruction is accepted (S102: YES), the controller 170 drives the motor 110 at a preset normal rotation speed. Is started (S103). More specifically, the drive circuit 173 starts energizing the motor 110 in response to a control signal from the control circuit 171.

After starting the driving of the motor 110, the controller 170 controls the driving of the motor 110 according to the detection value of the gas sensor 140. Specifically, when the detected value does not exceed the threshold value, that is, when the detected concentration of the specific gas does not exceed the upper limit concentration (S104: NO), the trigger switch 152 is in the ON state (S105). : YES), the process directly returns to S104 to continue monitoring the detected value. During this time, the driving of the motor 110 is continued. On the other hand, although the detected concentration of the specific gas does not exceed the upper limit concentration (S104: NO), the operator cancels the pressing operation of the trigger 151 and the trigger switch 152 is in the OFF state, that is, the driving instruction is accepted. When it is placed in the non-existent state (S105: NO), the controller 170 stops driving the motor 110 by stopping energization of the motor 110 (S106), and returns to the process of S101.

When the detected value exceeds the threshold value after the start of driving the motor 110 (S104: YES), the concentration of the specific gas detected by the gas sensor 140 exceeds the upper limit concentration, that is, the possibility of burnout of the motor 110 is It means that the driving power of 110 has increased to some extent as compared with the time of starting driving. Therefore, in order to protect the motor 110, the controller 170 stops driving the motor 110 by stopping energization of the motor 110 (S107). At the same time, the RAM included in the control circuit 171 stores information indicating that the motor 110 is in the drive prohibited state in which the drive is prohibited. Further, the controller 170 lights the warning lamp 180 to notify the operator that the concentration of the specific gas exceeds the upper limit concentration (S108).

The controller 170 monitors the signal from the reset switch 162, and stands by while the reset switch 162 is in the OFF state, that is, while it does not accept the drive prohibition state release instruction (S109: NO, S109). During this time, even if the operator presses the trigger 151 and turns on the trigger switch 152, the controller 170 does not drive the motor 110 according to the information indicating that the motor 110 is in the drive prohibited state. When the reset button 161 is pressed by the operator and the reset switch 162 is switched to the ON state (S109: YES), the controller 170 cancels the information indicating that the drive of the motor 110 is prohibited, and the warning lamp. The light 180 is turned off (S110), and the process returns to S101.

When the detected value still exceeds the threshold value after the warning lamp 180 is turned off (S101: NO), the operator presses the reset switch 162, but the concentration of the specific gas detected by the gas sensor 140 is higher than the upper limit concentration. Also means not low. Therefore, the controller 170 turns on the warning lamp 180 again without driving the motor 110 (S108). If the detected value exceeds the threshold value immediately after the start of the drive control process (S101: NO), the controller 170 proceeds directly to the process of S108.

On the other hand, when the detected value does not exceed the threshold value after the warning lamp 180 is turned off (S101: YES), it is assumed that the concentration of the specific gas has been reduced to the upper limit concentration or less and the overheated state of the motor 110 has been improved to some extent. To be done. Therefore, the controller 170 proceeds to the process of S102, and when the trigger switch 152 is turned on, starts the driving of the motor 110 again (S102: YES, S103). In this way, the controller 170 controls the driving of the motor 110 according to the detection value of the gas sensor 140.

As described above, the grinder 1 of the present embodiment includes the gas sensor 140 configured to detect the specific gas generated corresponding to the overheated state of the motor 110. The gas sensor 140 can detect that the specific gas is actually generated in response to the overheated state of the motor 110. Therefore, the possibility of burnout of the motor 110 can be detected more appropriately as compared with the case where the amount of heat storage of the motor whose temperature changes in a complicated manner is calculated from the current value. Then, the controller 170 can protect the motor 110 by limiting the rotation speed of the motor 110 according to the detection result of the gas sensor 140.

In particular, in the present embodiment, the gas sensor 140 is configured to be able to detect, as the specific gas, the gas that is considered to be generated before the winding of the motor 110 is short-circuited or disconnected, although the motor 110 is overheated. There is. For this reason, it is possible to increase the room for the operator to take some measures before the motor 110 is actually burned and needs to be replaced.

In the present embodiment, the gas sensor 140 is arranged on the path of the air flow formed by the fan 117, so that it is possible to effectively detect a specific gas included in the air flow and flowing. Note that it is assumed that the specific gas flows downstream of the motor 110 in the air flow path. In the present embodiment, since the gas sensor 140 is particularly arranged in the downstream side region including the portion on the downstream side of the motor 110 in the path of the air flow, it is possible to detect the specific gas more effectively. it can.

In the present embodiment, the grinder 1 includes a first operation unit 150 including a trigger 151 and a trigger switch 152, and a second operation unit 160 including a reset button 161 and a reset switch 162. After the detection value becomes equal to or more than the threshold value and the motor 110 is placed in the drive prohibited state, the controller 170 keeps the motor 110 running even if the drive instruction is accepted by the trigger switch 152 unless the reset switch 162 is turned on. It is configured not to drive but to maintain the drive prohibited state. Therefore, it is possible to maintain the motor 110 in the drive prohibited state so as not to bring the motor 110 into a state closer to burning.

On the other hand, when the reset switch 162 is turned on and the cancel instruction is received, the controller 170 is configured to cancel the drive prohibited state. Therefore, even if the motor 110 is once placed in the drive-prohibited state, if the operator confirms that the drive-prohibited state may be released and operates the reset button 161, the grinder 1 is used again in the normal state. be able to. For example, when the motor 110 is placed in the drive-prohibited state due to some malfunction, or when overheating subsides after being placed in the drive-prohibited state, the operator can take appropriate action depending on the situation, which is convenient. Is improved. In particular, in the present embodiment, when the motor 110 is placed in the drive prohibited state, the warning lamp 180 is turned on, so that the worker recognizes the situation of the motor 110 (there is a possibility of burning) and needs it. Therefore, it is possible to take measures to reduce the load.

[First modification]
Hereinafter, with reference to FIG. 4, a first modified example of the drive control process (see FIG. 3) of the first embodiment will be described. In the description of the present modification, steps having the same contents as those of the processing of the embodiment will be denoted by the same step numbers, and description thereof will be omitted or simplified as appropriate.

In the above-described first embodiment, when the second operation unit 160 including the reset button 161 and the reset switch 162 receives a cancel instruction for canceling the drive-prohibited state of the motor 110, then the detection value by the gas sensor 140 is the threshold value. If it is smaller than the above, driving of the motor 110 is allowed. On the other hand, in the present modified example, when the detected value exceeds the threshold value, the subsequent re-driving of the motor 110 is prohibited.

Specifically, as shown in FIG. 4, when the drive control process is started, the controller 170 drives the motor 110 when the detection value of the gas sensor 140 does not exceed the threshold value, and the detection value is equal to or higher than the threshold value. Then, the driving of the motor 110 is stopped, the warning lamp 180 is turned on, and the state of the reset switch 162 is monitored (S101 to S109). When the reset switch 162 is turned on by pressing the reset button 161 (S109: YES), the controller 170 turns off the warning lamp 180 (S110). In this modification, the information indicating the drive prohibition state stored in the RAM in the process of S107 is maintained without being canceled. As a result, even if the operator subsequently presses the trigger 151 and turns on the trigger switch 152, the controller 170 does not drive the motor 110 according to this information.

As described above, in this modification, once the driving of the motor 110 is stopped, the stopped state of the motor 110 is maintained regardless of the state of the reset switch 162 and the detection value of the gas sensor 140. Therefore, it is possible to prevent the possibility of burning of the motor 110 from increasing due to the motor 110 being driven again, and it is possible to more reliably protect the motor 110.

[Second modification]
Hereinafter, a second modification of the drive control process (see FIG. 3) of the first embodiment will be described with reference to FIGS. 5 and 6. In the second modified example, two thresholds that are compared with the detection value of the gas sensor 140 are set, and the point that the warning to the operator and the drive stop of the motor 110 are performed in stages is the process of the first embodiment. Is different from.

In this modification, a first threshold value and a second threshold value are set as two types of threshold values, and are stored in advance in the ROM of the control circuit 171, for example. The second threshold value is a value corresponding to the upper limit concentration described in the first embodiment. On the other hand, a value corresponding to a density lower than the upper limit density, that is, a value smaller than the second threshold is set as the first threshold. The first threshold is a concentration at which a warning is given to an operator in a state where the possibility of burnout of the motor 110 is lower before the concentration of a specific gas reaches the upper limit concentration when the motor 110 is overheated (hereinafter , Warning density).

As shown in FIG. 5, first, the controller 170 acquires the detection value of the gas sensor 140 and determines whether the detection value exceeds the first threshold value (S121). When the detected value does not exceed the first threshold value, that is, when the concentration of the specific gas does not exceed the warning concentration (S121: NO), the controller 170 issues a drive instruction while the trigger switch 152 is in the OFF state. It waits while it is not being accepted (S122: NO, S122). When the operator pushes the trigger 151 and the trigger switch 152 is switched to the ON state (S122: YES), the controller 170 starts driving the motor 110 at a preset normal rotation speed (S123).

After starting the driving of the motor 110, the controller 170 controls the driving of the motor 110 according to the detection value of the gas sensor 140. Specifically, when the detection value does not exceed the first threshold value (S124: NO), and the trigger switch 152 is in the ON state (S125: YES), the process directly returns to S124 to continue monitoring the detection value. To do. During this time, the driving of the motor 110 is continued. On the other hand, if the detected concentration of the specific gas does not exceed the warning concentration (S124: NO), but the operator cancels the pressing operation of the trigger 151 and the trigger switch 152 is placed in the OFF state ( (S125: NO), the controller 170 stops driving the motor 110 (S126), and returns to the process of S121.

When the detected value exceeds the first threshold value after the driving of the motor 110 is started (S124: YES), it means that the concentration of the specific gas exceeds the warning concentration. Therefore, the controller 170 blinks the warning lamp 180 to notify the operator that the concentration of the specific gas exceeds the warning concentration (S127).

Subsequently, as shown in FIG. 6, the controller 170 acquires the detection value of the gas sensor 140 and determines whether the detection value exceeds the second threshold value (S128). If the detected value does not exceed the second threshold value, that is, if the concentration of the specific gas does not exceed the upper limit concentration (S128: NO), if the trigger switch 152 is in the ON state (S129: YES), then S128 remains. Then, the process returns to the process (1) to continue monitoring the detected value. During this time, driving of the motor 110 and blinking of the warning lamp 180 are continued. On the other hand, when the detected concentration of the specific gas does not exceed the upper limit concentration (S128:NO), but the trigger switch 152 is placed in the OFF state (S129:NO), the controller 170 causes the motor 110 to operate. The driving is stopped (S130), and the process returns to S121 (see FIG. 5).

When the detected value exceeds the second threshold value (S128: YES), that is, when the concentration of the specific gas exceeds the upper limit concentration, the controller 170 stops driving the motor 110 to protect the motor 110 ( S131), the RAM of the control circuit 171 stores the information indicating the drive inhibition state. Further, the controller 170 lights up the warning lamp 180 to notify the operator that the concentration of the specific gas exceeds the upper limit concentration (S132). Thereafter, the controller 170 waits while the reset switch 162 is in the OFF state (S133: NO, S133), and when the reset switch 162 is in the ON state (S133: YES), turns off the warning lamp 180 (S134). ), and the process returns to S121 (see FIG. 5). The processing of S131 to S134 is the same as the processing of S107 to S110 (see FIG. 3) of the first embodiment.

When the detected value exceeds the first threshold value after the warning lamp 180 is turned off (S121: YES in FIG. 5), although the operator presses the reset switch 162, the concentration of the specific gas detected by the gas sensor 140 is detected. Means that at least the warning concentration is exceeded. Therefore, the controller 170 determines the detection value and the second threshold value (S141). When the detected value exceeds the second threshold value (S141: YES), it means that the concentration of the specific gas also exceeds the upper limit concentration. Therefore, the controller 170 proceeds to the above-described processing of S132 (see FIG. 6) without driving the motor 110, and turns on the warning lamp 180 again.

On the other hand, if the detected value does not exceed the second threshold value (S141: NO), it means that the concentration of the specific gas exceeds the warning concentration but is reduced to the upper limit concentration or less. Therefore, the controller 170 gives a warning to the operator by blinking the warning lamp 180 again (S142). The controller 170 waits while the trigger switch 152 is off (S143: NO, S143), and when the trigger switch 152 is turned on (S143: YES), starts driving the motor 110 (S144), and the above-mentioned Then, the process proceeds to S128 (see FIG. 6) to monitor whether the detected value exceeds the second threshold value.

On the other hand, when the detected value does not exceed the first threshold value after the warning lamp 180 is turned off (S121: NO), the concentration of the specific gas is lower than the warning concentration, and the overheated state of the motor 110 is improved to some extent. It is assumed that Therefore, the controller 170 proceeds to the process of S122, and when the trigger switch 152 is turned on (S122: YES), starts driving the motor 110 (S123). In this way, the controller 170 controls the driving of the motor 110 according to the detection value of the gas sensor 140.

As described above, in the present modification, regarding the specific gas detected by the gas sensor 140, the first threshold value corresponding to the warning concentration and the two threshold values corresponding to the upper limit concentration higher than the warning concentration are set in advance. ing. Then, when the detected value exceeds the first threshold value (that is, when the detected concentration of the specific gas exceeds the warning concentration), the warning lamp 180 blinks so that the concentration of the specific gas changes to the warning concentration. The operator is informed that the value exceeds the limit. Therefore, the worker can recognize that the motor 110 is heavily loaded and can take measures to reduce the load. Furthermore, when the specific gas increases and the detected value exceeds the second threshold value even when the warning is given by blinking the warning lamp 180 (that is, the detected specific gas concentration is When the upper limit concentration is exceeded), the driving of the motor 110 is stopped. Thereby, the motor can be protected. That is, in the present modification, the motor 110 is stopped only when the measure for reducing the load is not taken after the concentration of the specific gas exceeds the warning concentration. Therefore, it is possible to prevent unnecessary protection operation of the motor 110.

Further, when the detected value exceeds the first threshold value, the warning lamp 180 blinks, while when the detected value exceeds the second threshold value, the warning lamp 180 is turned on, so that It is reported that the gas has exceeded the upper limit concentration. In this way, the warning lamp 180 notifies the operator of the burnout of the motor 110 by giving different notifications depending on whether the detected concentration of the specific gas exceeds the warning concentration or exceeds the upper limit concentration. You can easily recognize that the possibility has increased.

[Second embodiment]
The second embodiment will be described below with reference to FIGS. 7 to 9. In this embodiment, a grinder 2 different from the first embodiment is illustrated as an example of an electric power tool. Although there are some differences, the basic structure of the grinder 2 is common to the grinder 1 shown in FIG. Therefore, in the following, the same reference numerals will be given to the basic configurations common to both, and the description will be omitted or simplified as appropriate, and different configurations will be mainly described. The main differences from the grinder 1 are the configuration of the motor 210 of the grinder 2, the configurations of the gas sensors 241-243, and the drive control processing of the motor 110 according to the detection results of the gas sensors 241-243.

First, the overall configuration of the grinder 2 will be described with reference to FIG. 7. As shown in FIG. 7, the outer contour of the grinder 2 is formed by the main body housing 100 extending in the front-rear direction, like the grinder 1. At the front end of the main body housing 100, a spindle 130 extending in the vertical direction is arranged. A motor 210 is arranged on the rear side of the spindle 130. In this embodiment, an AC motor having a brush is used as the motor 210. Similar to the first embodiment, the output shaft 211 of the motor 210 rotatably supported by the bearings 112 and 113 is arranged so as to extend in the front-rear direction orthogonal to the rotation axis A1 of the spindle 130.

A fan 117 for cooling the motor 210 is fixed to the output shaft 211 as in the first embodiment. In this embodiment, three gas sensors 241 to 243 are arranged on the path of the air flow formed by the fan 117. More specifically, the gas sensors 241 and 242 are both arranged in the downstream side region, and the gas sensor 243 is located closer to the motor 210 than the motor 210 in the flow direction (indicated by an arrow in the figure) of the air flow flowing in the main body housing 100. Is also arranged in a region including the upstream side portion (hereinafter referred to as the upstream side region). The term “upstream side of the motor 210” as used herein means an upstream side of a portion of the motor 210 that is arranged at the uppermost stream in the flow direction of the airflow (in this embodiment, the rear end of the motor 210). Means

In the present embodiment, the gas sensors 241 and 242 are fixed inside the main body housing 100 near the front end portion of the motor 210, and the gas sensor 243 is inside the main body housing 100 near the bearing 113 on the rear end side of the motor 210. It is fixed to. In the following description, the gas sensors 241, 242 are also referred to as the downstream sensors 241, 242, and the gas sensor 243 is also referred to as the upstream sensor 243.

Each of the gas sensors 241 to 243 is configured to be able to detect the same type of specific gas. Specifically, as in the first embodiment, each of the gas sensors 241 to 243 detects a specific gas generated from the insulating coating or the varnish.

In addition, in the present embodiment, the drive unit accommodating portion 101 forming the front side portion of the main body housing 100 corresponds to the fact that the AC motor with a brush is adopted as the motor 210. It is longer than the portion 101 in the front-back direction. As in the first embodiment, the controller 170 (see FIG. 8) and the first operation unit 150 including the trigger 151 and the trigger switch 152 are arranged in the grip 103 that constitutes the rear side portion of the main body housing 100. .. On the other hand, unlike the first embodiment, the second operation unit 160 (reset button 161 and reset switch 162) is not provided. A power cable 91 for connecting to an external AC power source is provided at the rear end of the grip 103 (rear end of the main body housing 100). Further, in the present embodiment, the main body housing 100 is provided with a buzzer 280 (see FIG. 8) instead of the warning lamp 180 of the first embodiment.

Hereinafter, the electrical configuration of the grinder 2 will be described with reference to FIG. As shown in FIG. 8, as in the first embodiment, the controller 170 that controls driving of the motor 210 includes a control circuit 171 and a drive circuit 173. Further, the gas sensors 241-243, the trigger switch 152, and the buzzer 280 are electrically connected to the control circuit 171. Each of the gas sensors 241 to 243 outputs a signal indicating a detected value. The trigger switch 152 outputs a signal corresponding to an ON state or an OFF state. The control circuit 171 controls the sound output of the buzzer 280 according to the control signal.

Hereinafter, drive control processing of the grinder 2 executed by the controller 170 (more specifically, the CPU of the control circuit 171) will be described with reference to FIG. 9. The drive control process of FIG. 9 is started when the power cable 91 is connected to the external power supply and the power supply to the grinder 2 is started, and is ended when the power supply is stopped.

As shown in FIG. 9, the controller 170 acquires the first detection value (S151) and further acquires the second detection value (S152). In the present embodiment, the average value of the detection values output from the two downstream sensors 241, 242 is used as the first detection value. On the other hand, the second detection value is the detection value output from the upstream sensor 243.

The controller 170 calculates the difference value between the first detection value and the second detection value, and determines whether the difference value exceeds the threshold value (S153). The difference value between the first detection value and the second detection value corresponds to the difference between the concentrations of the specific gas detected in the upstream region and the specific gas detected in the downstream region. In general, the specific gas generated in response to the overheated state of the motor 210 is included in the airflow and flows downstream from the motor 210, and therefore is disposed in the main body housing 100 in an upstream region with respect to the motor 210. When the concentration of the specific gas detected by the downstream sensors 241, 242 arranged in the downstream region with respect to the motor 210 becomes higher than the concentration of the specific gas detected by the upstream sensor 243 that has been operated. is assumed. On the other hand, when the motor 210 is not overheated and a specific gas existing around the grinder 2 flows from the outside of the main body housing 100 due to an external factor, the specific gas detected by the upstream sensor 243 is detected. It is assumed that the concentration of the gas and the concentration of the specific gas detected by the downstream sensors 241, 242 are substantially equal to each other or the concentration on the upstream side is higher.

Therefore, in the present embodiment, a value of zero or more is preset as the threshold value. As the threshold value is set to a value closer to zero, the motor 210 is protected even if the amount of the specific gas that is assumed to be generated due to the overheated state of the motor 210 is small. Therefore, as in the first embodiment, it is preferable that the threshold value is set to a value corresponding to the upper limit concentration difference that is not reached to the burnout of the motor 210. In this case, it is possible to reduce the possibility that the driving of the motor 210 is unnecessarily stopped due to the detection error of the gas sensors 241-243. The threshold may be stored in the ROM of the control circuit 171, for example.

When the difference value does not exceed the threshold value (S153: NO), the controller 170 monitors the signal from the trigger switch 152 and stands by while the trigger switch 152 is in the OFF state (S154: NO, S154). When the trigger 151 is pressed by the operator and the trigger switch 152 is switched to the ON state (S154: YES), the controller 170 starts driving the motor 210 at a preset normal rotation speed (S155).

After starting the driving of the motor 210, the controller 170 controls the driving of the motor 210 according to the detection values of the gas sensors 241 to 243. Specifically, the controller 170 acquires the first detection value and the second detection value again (S156, S157), and when the difference value does not exceed the threshold value (S158: NO), the trigger switch 152 is in the ON state. If there is (S159: YES), the process returns to S156 to continue monitoring whether the difference value exceeds the threshold value (S156 to S158). During this time, the driving of the motor 210 is continued. On the other hand, when the difference value does not exceed the threshold value (S158: NO), but the operator cancels the pressing operation of the trigger 151 and the trigger switch 152 is turned off (S159: NO), the controller 170 determines that The driving of the motor 210 is stopped (S160), and the process returns to S151.

When the difference value exceeds the threshold value after the start of driving the motor 210 (S158: YES), it means that the possibility of burnout of the motor 210 is increased to some extent as compared with when the motor 210 is started. Therefore, the controller 170 stops driving the motor 210 to protect the motor 210 (S161). At the same time, the RAM of the control circuit 171 stores information indicating the drive inhibition state. Further, the controller 170 issues a warning sound from the buzzer 280 to notify the operator that the concentration difference of the specific gas detected in the upstream region and the downstream region exceeds the upper limit concentration difference (S162). ).

After sounding the buzzer 280, the controller 170 acquires the first detection value and the second detection value (S163, S164), and if the state where the difference value exceeds the threshold value continues (S165: YES), S163. The process returns to step S3 to continue monitoring (S163 to S165). During this time, even if the operator presses the trigger 151 and turns on the trigger switch 152, the controller 170 does not drive the motor 210 according to the information indicating that the drive of the motor 210 is prohibited. When the difference value does not exceed the threshold value (S165: NO), the controller 170 cancels the information indicating that the motor 210 is in the drive prohibited state, and stops issuing the warning sound from the buzzer 280 (S166). , And returns to the processing of S154. When the trigger switch 152 is turned on (S154: YES), the controller 170 starts driving the motor 210 again (S155). In this way, the controller 170 controls the driving of the motor 210 according to the detection values of the gas sensors 241 to 243.

As described above, the grinder 2 of the present embodiment includes the upstream sensor 243 and the downstream sensors 241, 242 arranged in both the upstream area and the downstream area of the motor 210. Then, the controller 170 is configured to stop the motor 210 according to the detection results of both the upstream sensor 243 and the downstream sensors 241, 242. The specific gas has a higher concentration of the specific gas detected in the upstream region of the motor 210 or has a higher concentration of the specific gas detected in the upstream region and the downstream region of the motor 210 in the air flow path. If not so different, the particular gas may not have been generated in response to the overheated state of the motor 210. Therefore, as in the present embodiment, by utilizing the detection results of both the upstream side sensor 243 and the downstream side sensors 241, 242, the possibility of erroneous detection of the possibility of burnout of the motor 210 is suppressed, and the motor 210 is prevented. The drive can be controlled more appropriately.

In the present embodiment, when the motor 210 is placed in the drive prohibited state, the warning sound of the buzzer 280 is emitted. Therefore, the worker can recognize that there is a possibility of burning of the motor 210 based on the warning sound, and can take measures to reduce the load as necessary.

Further, in the present embodiment, even when the motor 210 is placed in the drive prohibited state, the difference between the first detection value and the second detection value, that is, the specific gas detected in the upstream region and the specific gas detected in the downstream region are detected. When the difference in the concentration of the specified specific gas becomes lower than the preset upper limit concentration difference, the drive inhibition state is released, and the motor 210 is driven again. In this way, even if the motor 210 is once placed in the drive prohibited state, if it is assumed that the overheated state of the motor 210 has subsided thereafter, the drive prohibited state is automatically released. The convenience of is improved.

[Modification]
Hereinafter, with reference to FIG. 10, a modified example of the drive control process (see FIG. 9) of the second embodiment will be described. In the description of the present modification, steps having the same contents as those of the processing of the embodiment will be denoted by the same step numbers, and description thereof will be omitted or simplified as appropriate.

In the above-described second embodiment, the difference value between the first detection value and the second detection value is used as the criterion for determining whether to start driving the motor 210 (S153 and S165). On the other hand, in this modification, at least one of the first detection value and the second detection value is used instead of the difference value.

Specifically, as shown in FIG. 10, after the controller 170 acquires the first detection value and the second detection value (S151 to S152), at least one of the first detection value and the second detection value is It is determined whether the preset threshold is exceeded (S1530). This threshold value is different from the value (a value corresponding to the upper limit density difference that is assumed to have not reached the burnout of the motor 210) used at the time of determining whether to stop the drive of the motor 210 in S158. As with the first embodiment, the value is a value corresponding to the upper limit concentration of the specific gas itself, which is permissible as if the burnout of the motor 110 has not been reached.

When at least one of the first detection value and the second detection value exceeds the preset threshold value (S1530: YES), the specific gas reaches the upper limit concentration on the upstream side or the downstream side of the motor 210. Means that Therefore, the controller 170 proceeds to the processing of S162 without starting the driving of the motor 210, and issues a warning sound from the buzzer 280. On the other hand, when neither the first detection value nor the second detection value exceeds the threshold value (S1530: NO), the controller 170 starts driving the motor 210 according to the operation of the trigger 151 (S154 to S155).

After the driving of the motor 210 is started, the difference value between the first detection value and the second detection value exceeds the threshold value, the driving of the motor 210 is stopped, and a warning sound is emitted (S155 to S162). The controller 170 acquires the first detection value and the second detection value (S163 to S164), and determines whether at least one of the first detection value and the second detection value exceeds a preset threshold value. Yes (S1650). When at least one of these exceeds the threshold value (S1650: YES), the controller 170 returns to the process of S163. When neither the first detection value nor the second detection value exceeds the threshold value (S1650: NO), the controller 170 stops the warning sound (S166) and returns to the process of S154.

As described above, in this modification, the drive of the motor 210 is started when the specific gas does not reach the upper limit concentration on either the upstream side or the downstream side of the motor 210, and then the first detected value is reached. When the difference value between the second detection value and the second detection value exceeds the threshold value, the driving of the motor 210 is stopped. Therefore, the overheated state due to the driving of the motor 210 can be detected more appropriately. In this modification, both the first detection value and the second detection value are compared with the threshold value. However, for example, only the first detection value by the downstream side sensors 241, 242, or the first detection value by the upstream side sensor 243 is used. Only two detection values may be compared with the threshold value.

[Third embodiment]
The third embodiment will be described below with reference to FIGS. 11 to 13. In this embodiment, a portable circular saw 3 is illustrated as an example of an electric tool. The circular saw 3 is configured to perform a cutting operation for cutting a workpiece by rotationally driving a disc-shaped tip tool. In the description of the present embodiment, an example in which a circular saw 3 is equipped with a disk-shaped saw blade 82 is used as a tip tool.

The overall configuration of the circular saw 3 will be described below with reference to FIG. As shown in FIG. 11, the outer contour of the circular saw 3 is formed by a long rectangular box-shaped main body housing 300 as a whole and a handle housing 303 which is formed in a substantially U shape and whose both ends are connected to the main body housing 300. ing. A spindle 330 for driving the saw blade 82 is arranged at one end of the main body housing 300 in the long axis direction (direction orthogonal to the paper surface of FIG. 11). Specifically, the spindle 330 is rotatably arranged so that its rotation axis extends in a direction intersecting the major axis direction of the main body housing 300 (more specifically, a direction substantially orthogonal to the main axis). One end of the spindle 330 is exposed to the outside from the main body housing 300, and is configured as a tool mounting portion 331 to which the saw blade 82 can be attached and detached.

Hereinafter, for convenience of description, the extending direction of the rotation axis A3 of the spindle 330 is defined as the left-right direction of the circular saw 3, and the one end side where the tool mounting portion 331 is provided is defined as the right side. Further, the direction orthogonal to the rotation axis A3 of the spindle 330 and corresponding to the long axis of the main body housing 300 (the direction orthogonal to the paper surface of FIG. 11) is defined as the front-back direction of the circular saw 3, and the spindle 330 in the main body housing 300 is The one end side (the front side of the paper surface of FIG. 11) arranged is defined as the front side.

The main body housing 300 mainly accommodates the motor 310, the transmission mechanism 320, and the spindle 330. In the present embodiment, the motor 310 is configured as a DC brushless motor, and rotationally drives the output shaft 311 by the electric power supplied from the rechargeable battery 90. The motor 310 is housed in the right front end portion formed in a cylindrical shape in the main body housing 300. The motor 310 is arranged such that the rotation axis of the output shaft 311 extends in the left-right direction in parallel with the rotation axis A3 of the spindle 330. The output shaft 311 is rotatably supported by bearings 312 and 313 on the left and right sides of the motor 310.

A fan 317 for cooling the motor 310 is fixed to the output shaft 311 between the main body (stator and rotor) of the motor 310 and the right bearing 313. The fan 317 is configured to form an air flow that flows through the main body housing 300 in a predetermined path. As in the first embodiment, the fan 317 is rotated by the driving of the motor 310, so that the fan flows into the main body housing 300 from the intake port on the left side of the motor 310, and as shown by an arrow in the drawing, the vicinity of the motor 310 is indicated. After flowing to the right through the exhaust gas, an air flow that flows out from the exhaust port on the right side of the motor 310 is formed. In this embodiment, the controller 370 for controlling the drive of the motor 310 is arranged between the motor 310 and the fan 317.

Two gas sensors 341 and 342 are arranged on the path of the air flow formed by the fan 317. In the present embodiment, the gas sensors 341 and 342 are both arranged in the downstream region with respect to the motor 310. More specifically, the gas sensors 341 and 342 are arranged on the substrate of the controller 370.

In the present embodiment, of the two gas sensors 341, 342, the gas sensor 341 is a specific gas (hereinafter, referred to as a specific gas) generated corresponding to a first state in which the motor 310 has a lower degree of overheating among the overheated states of the motor 310. A first gas). On the other hand, the gas sensor 342 detects a specific gas (hereinafter, referred to as a second gas) generated corresponding to the second state in which the degree of overheating is higher than the first state among the overheated states of the motor 310. It is configured. The types of specific gas to be detected are different between the gas sensors 341 and 342.

The first gas and the second gas are not particularly limited, but for example, when the motor 310 is placed in an overheated state, the resin forming the insulating coating of the winding of the motor 310 forms the varnish. When it is known that a specific gas is generated by being oxidized or decomposed before the resin to be used, a gas sensor 341 capable of detecting the gas generated from the insulating coating of the winding is used as the first gas. A gas sensor 342 capable of detecting the gas generated from the varnish may be used as the second gas. Hereinafter, the gas sensors 341 and 342 are also referred to as the first gas sensor 341 and the second gas sensor 342, respectively.

The transmission mechanism 320 is configured to reduce the rotation of the output shaft 311 of the motor 110 and then transmit the rotation to the spindle 330. The transmission mechanism 320 of this embodiment is configured as a reduction gear mechanism including an intermediate shaft and a plurality of gears. Since the structure of the transmission mechanism 320 is well known, it will be briefly described. The intermediate shaft is arranged parallel to the output shaft 311 and the spindle 330. The intermediate shaft has a driven gear that meshes with a drive gear that is provided at the front end of the output shaft 311, and a drive gear that meshes with the driven gear that is provided at the center of the spindle 330. The rotational power of the motor 310 is decelerated by the transmission mechanism 320 and transmitted to the spindle 330. As a result, the saw blade 82 fixed to the tool mounting portion 331 is rotationally driven together with the spindle 330.

The tool mounting portion 331 protruding leftward from the left end portion of the main body housing 300 is configured to sandwich the saw blade 82 from the left side and the right side by two flange portions and fix the saw blade 82 to the spindle 330. Since the configuration of the tool mounting portion 331 is well known, detailed description thereof is omitted here. A blade cover 305 for protecting the operator from the saw blade 82 is provided integrally with the main body housing 300 at the left end of the main body housing 300. Since the configuration of the blade cover 305 is well known, detailed description thereof will be omitted here.

Further, a base portion 307 having a mounting surface 308 that can be mounted on a workpiece is connected to the main body housing 300. Since the configuration of the base portion 307 is well known, it will be briefly described here. An opening is formed in the base portion 307, and the lower portions of the saw blade 82 and the blade cover 305 project downward from this opening. The mounting surface 308 of the base portion 307 is brought into surface contact with the upper surface of the workpiece, and the circular saw 3 is moved forward, whereby the saw blade 82 which is projected downward from the mounting surface 308 and rotated is used to process the workpiece. Can be cut. The rotation surface P1 of the saw blade 82 extends in a direction intersecting with the mounting surface 308.

In the main body housing 300, a battery mounting portion (not shown) in which a rechargeable battery 90 is detachably mounted is provided behind the housing portion of the motor 310. Further, a second operation unit 360 similar to the second operation unit 160 of the first embodiment and a warning lamp 380 are provided on the upper part of the housing of the motor 310. The second operation unit 360 includes a reset button 361 that can be pressed by an operator and a reset switch 362 (see FIG. 12) that is housed in the main body housing 300 and that receives an instruction to release the drive prohibited state of the motor 310. A warning lamp 380 for notifying the possibility of burnout of the motor 310 is arranged adjacent to the reset button 361, and is composed of an LED as in the first embodiment.

The handle housing 303 is connected to the upper portion of the main body housing 300 and projects upward in an inverted U shape. The upper part (protruding part) of the handle housing 303 constitutes a gripping part that is gripped by an operator during carrying or processing work. The handle housing 303 is provided with a first operation unit 350. Similar to the first operation unit 150 of the first embodiment, the first operation unit 350 includes a trigger 351 that can be pressed from the outside by an operator, and a trigger switch that is housed in the handle housing 303 and receives a drive instruction of the motor 310. 352 and (see FIG. 12).

Next, the electrical configuration of the circular saw 3 will be described with reference to FIG. As shown in FIG. 12, the controller 370 that controls driving of the motor 310 includes a control circuit 371 and a drive circuit 373. In the present embodiment, the control circuit 371 is composed of a microcomputer including a CPU, a ROM, a RAM and the like, like the control circuit 171 of the first embodiment. The drive circuit 373 is configured to supply electric power from the battery 90 mounted in the battery mounting portion and supply a current to the winding of the motor 310, and operates according to the control signal output from the control circuit 371. The control circuit 371 operates by receiving power supply from the battery 90 via a power supply circuit (not shown).

The aforementioned first gas sensor 341, second gas sensor 342, trigger switch 352, reset switch 362, and warning lamp 380 are electrically connected to the control circuit 371. The first gas sensor 341 and the second gas sensor 342 each output a signal indicating a detection value. The trigger switch 352 and the reset switch 362 each output a signal corresponding to an ON state or an OFF state. The control circuit 371 controls the lighting of the warning lamp 380 by a control signal.

The drive control processing of the circular saw 3 executed by the controller 370 (more specifically, the CPU of the control circuit 371) will be described below with reference to FIGS. 13 and 14. The drive control process of FIGS. 13 and 14 is started when the battery 90 is mounted in the battery mounting portion and power supply to the circular saw 3 is started, and is ended when power supply is stopped.

Here, the threshold value used for comparison with the detected value in the present embodiment will be described. In the present embodiment, the first threshold value that is compared with the detection value (hereinafter, referred to as the first detection value) output corresponding to the concentration of the first gas detected by the first gas sensor 341, and the second gas sensor 342. The second threshold value to be compared with the detection value (hereinafter, referred to as the second detection value) output from is preset.

As described above, the first gas is generated in correspondence with the first state in which the motor 110 has a lower degree of overheating, and the second gas is generated in correspondence with the second state in which the degree of superheating of the motor 110 is higher. To do. Therefore, for example, as the first threshold value, the concentration of the first gas corresponding to the state in which the first gas is generated to some extent but the second gas is not generated is experimentally specified, and the warning concentration Along with the setting, as the second threshold value, the upper limit concentration of the second gas corresponding to a state where the second gas is generated to some extent but has not reached the burnout of the motor 310 is experimentally specified and set. be able to. The first threshold value and the second threshold value may be stored in advance in the ROM of the control circuit 371, for example.

As shown in FIG. 13, when the drive control process is started, the controller 370 acquires the first detection value output from the first gas sensor 341 and determines whether the first detection value exceeds the first threshold value. Is determined (S171). When the first detection value does not exceed the first threshold value, that is, when the concentration of the first gas does not exceed the warning concentration (S171: NO), the controller 370 waits while the trigger switch 352 is in the OFF state. Yes (S172: NO, S172). When the trigger 351 is pressed by the operator and the trigger switch 352 is switched to the ON state (S172: YES), the controller 370 starts driving the motor 310 at a preset normal rotation speed (S173).

After the driving of the motor 310 is started, the controller 370 controls the driving of the motor 310 according to the detection values of the first gas sensor 341 and the second gas sensor 342. Specifically, if the first detection value does not exceed the first threshold value (S174: NO) and the trigger switch 352 is in the ON state (S175: YES), the process directly returns to S174 and the first detection value is reached. Continue to monitor. During this time, the driving of the motor 310 is continued. On the other hand, when the detected concentration of the first gas does not exceed the warning concentration (S174: NO) but the trigger switch 352 is placed in the OFF state (S175: NO), the controller 370 causes the motor 310 to operate. Is stopped (S176), and the process returns to S171.

When the first detection value exceeds the first threshold value after the start of driving the motor 310 (S174: YES), it means that the concentration of the first gas exceeds the warning concentration. Therefore, the controller 370 blinks the warning lamp 380 to notify the operator that the concentration of the specific gas is equal to or higher than the warning concentration (S177).

Subsequently, as shown in FIG. 14, the controller 370 acquires the second detection value output from the second gas sensor 342 and determines whether the second detection value exceeds the second threshold value (S178). When the second detection value does not exceed the second threshold, that is, when the concentration of the second gas does not exceed the upper limit concentration (S178: NO), if the trigger switch 352 is in the ON state (S179: YES). , And returns to the processing of S178 as it is and continues to monitor the second detected value. During this time, driving of the motor 310 and blinking of the warning lamp 380 are continued. On the other hand, when the detected concentration of the second gas does not exceed the upper limit concentration (S178: NO) but the trigger switch 352 is placed in the OFF state (S179: NO), the controller 370 causes the motor 310 to operate. Is stopped (S180), and the process returns to S171 (see FIG. 13).

When the second detected value exceeds the second threshold value (S178: YES), that is, when the concentration of the second gas exceeds the upper limit concentration, the controller 370 drives the motor 310 to protect the motor 310. The operation is stopped (S181), and the RAM of the control circuit 371 stores the information indicating the drive inhibition state. Further, the controller 370 notifies the operator that the concentration of the second gas exceeds the upper limit concentration by turning on the warning lamp 380 (S182). Thereafter, the controller 370 waits while the reset switch 362 is in the OFF state (S183: NO, S183), and when the reset switch 362 is in the ON state (S183: YES), turns off the warning lamp 380 (S184). ), the drive control process ends. In the present embodiment, as in the first modification of the first embodiment, the information indicating the drive prohibition state stored in the RAM in the processing of S181 is maintained without being canceled. As a result, even if the operator subsequently presses the trigger 351 and turns on the trigger switch 352, the controller 370 does not drive the motor 310 according to this information.

As described above, the circular saw 3 of this embodiment includes the first gas sensor 341 and the second gas sensor 342. The first gas sensor 341 detects the first gas generated corresponding to the first state in which the degree of overheating of the motor 310 is lower, and the second gas sensor 342 indicates that the degree of overheating of the motor 310 is higher than that in the first state. The second gas generated corresponding to the high second state is detected. In this way, by providing the first gas sensor 341 and the second gas sensor 342, the controller 370 can perform appropriate control according to the degree of overheating of the motor 310.

Furthermore, in this embodiment, the first threshold value corresponding to the warning concentration related to the first gas and the second threshold value corresponding to the upper limit concentration related to the second gas are preset. When the first detected value exceeds the first threshold value, that is, when the concentration of the first gas exceeds the warning concentration, a warning is issued by the warning lamp 380, so that the operator can put a high load on the motor. It is possible to recognize that there is a problem and take measures to reduce the load. Despite the warning, if the degree of overheating becomes higher and the second detected value exceeds the second threshold value, that is, if the concentration of the second gas exceeds the upper limit concentration, the controller 370 causes the motor to operate. By stopping the driving of 310, the motor can be reliably protected. As described above, in the present embodiment, the rotation speed of the motor 310 is limited only when the measure for reducing the load is not taken after the first gas exceeds the warning concentration. Therefore, it is possible to prevent unnecessary protection operation of the motor 310.

Further, when the first detection value exceeds the first threshold value, the warning lamp 380 blinks, whereas when the second detection value exceeds the second threshold value, the warning lamp 380 is turned on. Then, it is reported that the second gas exceeds the upper limit concentration. In this way, the warning lamp 380 gives a notification in a different manner depending on the degree of overheating of the motor 310, so that the operator can easily recognize that the possibility of burning of the motor 310 has increased. You can

[Fourth Embodiment]
The fourth embodiment will be described below with reference to FIG. In this embodiment, the chain saw 4 is illustrated as an example of an electric tool. The chain saw 4 is configured to perform a cutting operation for cutting a workpiece by rotationally driving a chain-shaped tip tool. More specifically, the chain saw 4 is configured to drive the loop-shaped chain blade 83, which is stretched around the guide bar 409, along the outer periphery of the guide bar 409.

As shown in FIG. 15, the outer contour of the chain saw 4 is formed by a hollow main body housing 400. Inside the main body housing 400, a motor 410, a transmission mechanism 420, and a spindle 430 for driving the chain blade 83 are mainly arranged. The motor 410 and the spindle 430 are arranged such that the rotation axis of the output shaft 411 of the motor 410 and the rotation axis A4 of the spindle 430 are parallel to each other.

One end of the spindle 430 protrudes from the main body housing 400 to the outside, and the sprocket 431 is integrally rotatably fixed to the spindle 430 at this one end. The sprocket 431 is configured to be able to mesh with the chain blade 83. The long guide bar 409 around which the chain blade 83 is stretched is detachably fixed to the main body housing 400 at one end portion in the long axis direction thereof. The guide bar 409 protrudes from the main body housing 400 in a direction intersecting the rotation axis A4 of the spindle 430 (more specifically, a direction substantially orthogonal to the rotation axis A4).

Hereinafter, for convenience of description, the extending direction of the rotation axis A4 of the spindle 430 is defined as the left-right direction of the chain saw 4, and the one end side where the sprocket 431 is provided is defined as the right side. A direction orthogonal to the rotation axis A4 of the spindle 330 and corresponding to the extending direction of the guide bar 409 is defined as the front-back direction of the chain saw 4, and the protruding end side of the guide bar 409 is defined as the front side.

At the right end of the main body housing 400, a guide bar attachment portion 432 is provided on the front side of the sprocket 431 so that the guide bar 409 can be attached and detached. Since the structure of the guide bar mounting portion 432 is well known, detailed description thereof will be omitted here. After the chain blade 83 is stretched over the guide bar 409 and meshed with the sprocket 431, the guide bar 409 is fixed to the guide bar attachment portion 432. As a result, the chain blade 83 is attached to the chain saw 4.

A fan 417 for cooling the motor 410 is fixed to the output shaft 411 of the motor 410 on the right side of the main body (stator and rotor) of the motor 410. The fan 417 forms an air flow that flows through a predetermined path through the main body housing 400, as indicated by an arrow in the drawing. FIG. 15 shows an example in which four gas sensors 441 to 444 capable of detecting a specific gas are arranged. Of these, the gas sensors 441 and 442 are arranged in the downstream region with respect to the motor 410, and the gas sensors 443 and 444 are arranged in the upstream region with respect to the motor 410.

The transmission mechanism 420 is configured to reduce the rotation of the output shaft 411 of the motor 410 and then transmit the rotation to the spindle 330. The transmission mechanism 420 of the present embodiment is configured as a reduction gear mechanism including a small gear fixed to the right end portion of the output shaft 411 and a large gear fixed to the spindle 430 and meshing with the small gear. The rotation of the motor 410 is decelerated by the transmission mechanism 420 and transmitted to the spindle 430. As a result, the chain blade 83 meshed with the sprocket 431 and wound around the guide bar 409 is rotationally driven along the outer periphery of the guide bar 409.

At the rear end of the main body housing 400, a battery mounting portion 405 configured to attach and detach the rechargeable battery 90 is provided, and between the motor 410 and the battery mounting portion 405, a controller that controls driving of the motor 410. 470 is arranged. The controller 470 has the same configuration as the controller 170 (see FIG. 2) of the first embodiment. Further, although not shown, a U-shaped handle housing that constitutes a grip portion to be gripped by an operator is connected to the upper side of the main body housing 400. Similar to the circular saw 3 shown in FIG. 5, the handle housing is provided with a first operation unit (not shown) including a trigger that can be pressed by an operator and a trigger switch that receives a drive instruction of the motor 410. ing. Further, the main body housing 400 may be provided with a second operation unit including a reset button and a reset switch, a warning lamp or a buzzer.

In the chain saw 4 having such a configuration, the drive control processing of the motor 410 performed by the controller 470 may be the same as the processing of any of the above-described embodiment and its modification, or a part of any processing is changed. The processing may be performed or a combination of a plurality of processes may be performed. For example, when the above-described four gas sensors 441 to 444 can all detect the same type of specific gas, the controller 470 determines the downstream gas sensors 441 and 442 and the upstream gas sensors 443 and 444 as in the second embodiment. The drive of the motor 410 can be controlled according to the detection result of (see FIG. 9). In this case, the average value of the detection values of the gas sensors 441 and 442 may be the first detection value, and the average value of the detection values of the gas sensors 443 and 444 may be the second detection value.

On the other hand, for example, among the gas sensors 441 to 444, the gas sensor 441 on the downstream side and the gas sensor 443 on the upstream side detect the first gas generated corresponding to the first state in which the degree of overheating of the motor 410 is lower. The downstream gas sensor 442 and the upstream gas sensor 444 may be configured to detect the second gas generated corresponding to the second state in which the degree of overheating of the motor 410 is higher. Although illustration is omitted, in this case, the controller 470 performs a process in which the drive control process of the second embodiment (see FIG. 9) and the drive control process of the third embodiment (see FIGS. 13 and 14) are combined. It can be carried out. That is, the controller 470 issues a warning when the difference value between the detection value of the gas sensor 441 and the detection value of the gas sensor 443 exceeds the first threshold value, and the difference value between the detection value of the gas sensor 442 and the detection value of the gas sensor 444. When exceeds the second threshold value, the driving of the motor 410 may be stopped.

[Fifth Embodiment]
The fifth embodiment will be described below with reference to FIG. 16. In this embodiment, the hammer drill 5 is illustrated as an example of an electric tool. The hammer drill 5 drives a tip tool (hammer bit, drill bit, etc. (not shown)) coaxially mounted on a cylindrical tool holder 530 so as to perform a chipping work or a drilling work on a workpiece. It is configured.

As shown in FIG. 16, the outer contour of the hammer drill 5 is mainly formed of a main body housing 500 and a handle housing 503. The main body housing 500 includes a drive mechanism housing portion 501 and a motor housing portion 502. The drive mechanism accommodating portion 501 is formed in a long shape extending in the striking axis A5 direction. A tool holder 530 to which a tip tool is detachably attached is arranged in one end of the drive mechanism housing 501 in the long axis direction. The motor housing portion 502 extends from the other end portion of the drive mechanism housing portion 501 in the major axis direction in a direction intersecting the striking axis A5 (strictly, a substantially orthogonal direction).

In the following description, for convenience, the extending direction of the striking shaft A5 (longitudinal direction of the drive mechanism housing portion 501) is defined as the front-back direction of the hammer drill 5, and the side where the tool holder 530 is provided is defined as the front side. Further, the direction orthogonal to the striking axis A5 and corresponding to the extending direction of the motor housing portion 502 is defined as the vertical direction of the hammer drill 5, and the side where the drive mechanism housing portion 501 and the motor housing portion 502 are connected is the upper side. Stipulate.

The motor housing portion 502 houses a motor 510 and a controller 570 that controls driving of the motor 510. The motor 510 is configured as a brushless motor, and is arranged such that the rotation axis of the output shaft 511 of the motor 510 is orthogonal to the striking axis A5. A drive gear 532 is fixed to the upper end of the output shaft 511. A fan 517 for cooling the motor 510 is fixed between the main body (stator and rotor) of the motor 510 and the drive gear 532. The fan 517 forms an air flow through the main body housing 500 through a predetermined path. Note that the airflow flows from the bottom to the top in the motor housing portion 502, as indicated by the arrow in FIG. FIG. 16 shows an example in which two gas sensors 541 and 542 capable of detecting a specific gas are arranged in the downstream side area, that is, the upper side area with respect to the motor 510.

A controller 570 is arranged below the motor 510. The controller 570 has the same configuration as the controller 170 (see FIG. 2) of the first embodiment. An upper portion of the motor housing portion 502 constitutes a protruding portion that protrudes rearward, and a battery mounting portion 505 to which the rechargeable battery 90 is attachable/detachable is provided below the protruding portion.

The drive mechanism accommodating portion 501 accommodates a motion converting mechanism 531, a striking element 533, and a rotation transmitting mechanism 535. The rotation of the motor 510 is transmitted to the motion conversion mechanism 531 and the rotation transmission mechanism 535 via the drive gear 532. Since the configurations of the motion converting mechanism 531, the striking element 533, and the rotation transmitting mechanism 535 are well known, they will be briefly described here.

The motion converting mechanism 531 is configured to convert the rotation of the intermediate shaft, which is rotationally driven by the rotation of the output shaft 511, into the linear motion of the piston in the striking axis A5 direction by the swinging of the swinging member. ing. The striking element 533 is arranged so as to be linearly movable in the striking axis A5 direction. The striking element 533 is configured to apply a striking force in the striking axis A5 direction to the tip tool mounted on the tool holder 530 with the linear movement of the piston. The tip tool is linearly driven in the striking axis A5 direction by the motion converting mechanism 531 and the striking element 533 as the motor 510 is driven. The rotation transmission mechanism 535 of this embodiment is configured as a reduction gear mechanism including a plurality of gears, and after appropriately decelerating the rotation of the motor 510, the rotation transmission mechanism 535 transmits the rotation to the tip tool via the tool holder 530 as the final shaft. Is configured to. The tip tool is driven to rotate around the striking axis A5 by the rotation transmission mechanism 535 as the motor 510 is driven.

The hammer drill 5 has a hammer mode in which the tip tool is linearly driven in a predetermined striking axis A5 direction, a drill mode in which the tip tool is rotationally driven around the striking axis A5, and linear driving and rotary driving of the tip tool at the same time. It is configured to operate in one of the hammer drill modes selected by the operator. For this reason, the drive mechanism accommodating portion 501 is provided with a mechanism for mode switching. However, the configuration of this mechanism is well known, and a description thereof will be omitted here.

The elongated handle housing 503 is arranged so as to extend in the vertical direction, and an upper end portion and a lower end portion thereof project rearward from the rear end of the drive mechanism housing portion 501 and the rear end of the motor housing portion 502, respectively. It is connected to the protrusion. The handle housing 503 constitutes a grip portion that is gripped by an operator. The front end of the drive mechanism accommodating portion 501 is formed in a tubular shape, and the auxiliary handle 504 is attachable to and detachable from the outer peripheral surface thereof.

The handle housing 503 is provided with a first operation unit 550 including a trigger 551 that is pressed by an operator and a trigger switch 552 that receives a drive instruction of the motor 510. Further, the main body housing 500 may be provided with a second operation unit including a reset button and a reset switch, a warning lamp or a buzzer.

In the hammer drill 5 having such a configuration, the drive control processing of the motor 510 performed by the controller 570 may be the same as the processing of any of the above-described embodiment and its modification, or a part of any processing is changed. The processing may be performed or a combination of a plurality of processes may be performed. For example, when the gas sensors 541 and 542 described above can detect the same type of specific gas, the controller 570 uses the average value of the detection values of the two gas sensors 541 and 542 to detect the first embodiment and its modification. Similar processing (see FIGS. 3, 4, 5, and 6) can be performed. Further, for example, when the gas sensors 541 and 542 can detect the first and second gases respectively generated corresponding to the first and second states having different degrees of overheating, the process of the third embodiment (see FIG. 13 and (See FIG. 14) may be adopted.

[Sixth Embodiment]
The sixth embodiment will be described below with reference to FIG. In this embodiment, the hammer drill 6 is illustrated as an example of an electric tool. Although the hammer drill 6 of the present embodiment has some differences, the basic configuration thereof is common to the hammer drill 5 of the fifth embodiment shown in FIG. Therefore, in the following, the same reference numerals will be given to the basic configurations common to both, and the description will be omitted or simplified as appropriate, and different configurations will be mainly described.

The motor 610 of the hammer drill 6 is configured as an AC motor driven by electric power supplied from an external power supply. Therefore, a power cable 92 for connecting to an external power source is provided at the lower end of the main body housing 500 (motor housing portion 502). In the hammer drill 6 as well, the motor 610 is arranged such that the rotation axis of the output shaft 611 thereof is orthogonal to the striking axis A5. A drive gear 532 that transmits the rotation of the motor 610 to the motion conversion mechanism 531 and the rotation transmission mechanism 535 is fixed to the upper end portion of the output shaft 611. The motion converting mechanism 531 of the hammer drill 6 is configured to convert the rotary motion of the intermediate shaft into a linear motion of the piston by using a crank mechanism. The hammer drill 6 is configured to operate in any one selected from the drill mode and the hammer drill mode.

In the hammer drill 6, a fan 617 for cooling the motor 610 is fixed to the output shaft 611 below the main body (stator and rotor) of the motor 610. The fan 617 forms an air flow that flows through the main body housing 500 through a predetermined path. Note that the airflow flows from the top to the bottom in the motor housing portion 502, as indicated by the arrow in FIG. In FIG. 17, two gas sensors 641 and 642 capable of detecting a specific gas of the same type are provided in a downstream region, that is, a lower region and an upstream region, that is, an upper region, with respect to the main body of the motor 510. An example is shown that is arranged in the area and.

Although not shown, a controller is arranged in the main body housing 500 and controls the drive of the motor 610. The drive control process of the motor 510 performed by the controller 570 may be the same as the process of any of the above-described embodiment and its modification, or a part of any process may be changed. Alternatively, a combination of a plurality of processes may be used.

The above-described embodiment and its modifications are merely examples, and the power tool according to the present invention is not limited to the configurations of the illustrated grinders 1, 2, the circular saw 3, the chain saw 4, and the hammer drills 5, 6. For example, the modifications exemplified below can be made. It should be noted that, as for these changes, only one of them or a plurality of them are the same as the grinders 1 and 2 shown in the embodiment, the circular saw 3, the chain saw 4, the hammer drills 5 and 6, or the invention described in the claims. It can be adopted in combination.

For example, the present invention may be applied to a power tool configured to drive a tip tool by using a motor as a driving source, other than those exemplified. Examples of such electric tools include driver drills, impact drivers, cutters, reciprocating saws, electric hammers, mowers and hedge clippers, but electric tools other than these examples are not excluded.

Since the working state of the hand-held power tool varies greatly depending on the worker, the load applied to the motor tends to be unsteady or atypical. In addition, since the hand-held power tool is used in various work postures, it may be difficult for the worker to notice the possibility of burning. Therefore, it can be said that the present invention is particularly suitable for a hand-held power tool.

The number and arrangement of the gas sensors in the power tool exemplified in the above-described embodiment and its modification, and the drive control processing according to the detection result of the gas sensors can be appropriately changed. The number and placement of gas sensors in any of the illustrated power tools may be applied to other power tools. It should be noted that the gas sensor does not necessarily have to be arranged in the main body housing, but at least one is arranged in the main body housing so that the specific gas generated corresponding to the overheated state of the motor can be detected more reliably. Preferably. Further, in order to more surely detect the possibility of burnout of the motor, the gas sensor is preferably arranged in the downstream region with respect to the motor, but may be arranged in another position in the main body housing. When detecting the first gas generated corresponding to the first state where the degree of overheating of the motor is lower, and the second gas generated corresponding to the second state where the degree of overheating of the motor is higher, The two detection units may be realized as one gas sensor that can detect both the first gas and the second gas.

In the above-described embodiment and modified example, as the specific gas, when the motor is placed in an overheated state, a gas that is known to be generated before a short circuit or disconnection occurs in the winding of the motor is detected. Examples are given. In this case, the possibility that the motor can be protected before it burns out increases, which is preferable. However, the power tool may be configured to detect the gas generated in response to the burning of the winding itself and stop the driving of the motor. In addition, in the embodiment and the modification, the detection unit capable of detecting a specific gas is referred to as a gas sensor, but what is called an odor sensor or a smoke sensor may be adopted.

The drive control process in any of the exemplified power tools may be applied to other power tools, or two or more parts of the exemplified drive control processes may be appropriately combined. A part of the exemplified drive control processing may be appropriately changed. For example, in the drive control process of the first embodiment and its modification, for example, as a process of limiting the rotation speed of the motor according to the detection result by the gas sensor, the drive of the motor is stopped (the rotation speed of the motor is set to zero). ) Instead of the process, a process of changing the rotation speed of the motor to a rotation speed larger than zero and lower than the normal rotation speed may be performed. Further, the reduction of the rotation speed of the motor and the stop of the driving of the motor may be combined. For example, in the process of the second modified example of the first embodiment (see FIGS. 5 and 6), when the detected value exceeds the first threshold value, the motor is driven at a rotation speed lower than the normal rotation speed (S127 and S144), and thereafter, if the detected value exceeds the second threshold value, a process of stopping the driving of the motor (S131) may be performed. Furthermore, for example, when the detected value exceeds the first threshold value, the motor is driven at the first rotation speed lower than the normal rotation speed (S127 and S144), and then the detected value exceeds the second threshold value. In addition, the process of driving the motor at the second rotation speed lower than the first rotation speed (S131) may be performed.

Further, as a reference for determining whether or not to perform the process of limiting the number of rotations of the motor, instead of comparing the detection value with a preset threshold value, the rate of increase of the detection value during a predetermined period (that is, The increase rate of the concentration of the specific gas) may be compared with a preset upper limit increase rate. Then, when the increase rate during the predetermined period exceeds the upper limit increase rate, the process of limiting the rotation speed of the motor may be performed.

The presence/absence, arrangement, and configuration of the first operation unit, the second operation unit, the warning lamp, and the buzzer can also be appropriately changed according to the control process to be applied. Further, the motor may be configured as a DC motor or an AC motor in any power tool, and the presence or absence of the brush is not particularly limited.

For example, in the above-described embodiment and modification, the detection result of the gas sensor is detected by the light emitted by the warning lamp (LED) and the sound emitted by the buzzer together with the limitation on the rotation speed of the motor (stopping the drive or decreasing the rotation speed). However, such notification does not necessarily have to be performed. In the process of the second modified example of the first embodiment (see FIGS. 5 and 6) and the process of the third embodiment (see FIGS. 13 and 14), notification is performed in two stages. The notification may be performed only in the first stage, and only the rotation speed of the motor may be limited in the second stage. Further, the mode of notification is not limited to that by light or sound, and may be performed, for example, by displaying characters or figures on the display.

In the above-described embodiments and modified examples, the control circuit of the controller is exemplified by a microcomputer including a CPU, ROM, RAM, etc., but the control circuit is, for example, ASIC (Application Specific Integrated Circuits). , FPGA (Field Programmable Gate Array), or other programmable logic device. Further, the drive control processing of the above-described embodiment and modification may be realized by the CPU executing the program stored in the ROM. In this case, the program may be previously stored in the ROM in the control circuit, or may be stored in the non-volatile memory when the control circuit includes the non-volatile memory. Alternatively, the program may be recorded in an external storage medium that can read data (for example, a USB memory). The drive control processing of the above-described embodiment and modification may be distributed to a plurality of control circuits.

Note that some electric tools are used in almost the same posture during processing work. For example, the circular saw 3 shown in FIG. 5 is usually used with the base portion 307 placed on the workpiece, so the vertical direction of the circular saw 3 matches the actual vertical direction. In such an electric power tool, it is considered that a specific gas generated by heating the insulating material or the varnish moves upward. Therefore, it is preferable that the gas sensor is arranged above the lower end of the motor in the normal posture during the working operation of the electric tool.

Furthermore, in view of the spirit of the present invention and the above-described embodiment, the following aspects are constructed. The following aspects can be adopted in combination with the invention described in each claim.
[Aspect 1]
The power tool is a grinder configured to perform a grinding operation, a polishing operation, or a cutting operation on a workpiece by rotationally driving the disk-shaped tip tool,
The housing is formed in a long shape,
A spindle arranged at one end of the housing in the long axis direction, rotatable about a rotation axis extending in a direction intersecting the long axis direction, and having a tip tool attachable/detachable,
The electric power tool, wherein the spindle is configured to rotationally drive the tip tool around the rotation axis according to rotation of an output shaft of the motor.
[Aspect 2]
The electric power tool is a circular saw configured to perform a cutting operation on a workpiece by rotationally driving the disk-shaped tip tool,
A base portion connected to the housing and having a mounting surface configured to be mountable on the workpiece;
A spindle that is rotatably arranged around a predetermined rotation axis in the housing and is configured such that the tip tool can be attached and detached;
The spindle is configured to rotationally drive the tip tool around the rotation axis along a rotation surface extending in a direction intersecting with the mounting surface according to the rotation of the output shaft of the motor. An electric tool that is characterized by
[Aspect 3]
The power tool is a chain saw configured to perform a cutting operation on a workpiece by rotationally driving the chain-shaped tip tool,
A spindle having a sprocket that is rotatably arranged around a predetermined rotation axis in the housing and configured to be capable of meshing with the tip tool;
A guide bar around which the tip tool meshed with the sprocket is mounted,
The electric power tool, wherein the spindle is configured to rotationally drive the tip tool along an outer circumference of the guide bar in accordance with rotation of an output shaft of the motor.
[Aspect 4]
The electric power tool performs chipping work on a workpiece by linearly driving the tip tool in a predetermined striking axis direction, and rotationally driving the tip tool around the striking axis. A hammer drill configured to perform a drilling operation on the workpiece according to
A tool holding portion that is rotatably provided around the striking shaft with respect to the housing, and is configured such that the tip tool is detachable,
A striking mechanism that is linearly movable in the striking axis direction, and is configured to be driven linearly by striking the tip tool attached to the tool holding portion in the striking axis direction,
A motion conversion mechanism configured to convert the rotation of the output shaft of the motor into a linear motion in the striking axis direction and transmit the linear motion to the striking mechanism;
A rotation transmission mechanism configured to transmit the rotation of the output shaft to the tool holding portion as a rotation motion around the striking axis.

Correspondence between each component of the above-described embodiment and modification and each component of the present invention is shown below. The grinders 1, 2, the circular saw 3, the chain saw 4, and the hammer drills 5, 6 are examples of configurations corresponding to the “electric power tool” of the present invention. Each of the main body housings 100, 300, 400 and 500 is a configuration example corresponding to the “housing” of the present invention. The motors 110, 210, 310, 410, 510, 610 are examples of configurations corresponding to the “motor” of the present invention. Each of the controllers 170, 370, 470, 570 is a configuration example corresponding to the “control unit” of the present invention. Each of the fans 117, 317, 417, 517, 617 is a configuration example corresponding to the "fan" of the present invention.

Each of the gas sensors 140, 241-243, 341, 342, 441-444, 541, 542, 641, 642 is a configuration example corresponding to the "detection unit" of the present invention. Each of the gas sensors 140, 241, 242, 341, 342, 441, 442, 541, 542, 641 is a configuration example corresponding to the "downstream detection unit" of the present invention. Each of the gas sensors 243, 443, 444, 642 is a configuration example corresponding to the “upstream detection section” of the present invention. The gas sensor 341 is a configuration example corresponding to the “first gas detection unit” of the present invention. The gas sensor 342 is a configuration example corresponding to the “second gas detection unit” of the present invention.

The first operation units 150, 350, 550 are respectively configuration examples corresponding to the “first operation unit” of the present invention. The second operation units 160 and 360 are configuration examples corresponding to the “second operation unit” of the present invention. The warning lamps 180, 380 and the buzzer 280 are examples of configurations corresponding to the "notification unit" of the present invention.

1, 2: Grinders 100, 300, 400, 500: Main body housing 101: Drive part housing part 103: Grip part 105: Battery mounting part 110, 210, 310, 410, 510, 610: Motor 111, 211, 311, 411 511, 611: output shafts 112, 113: bearings 117, 317, 417, 517, 617: fan 120: transmission mechanism 130: spindle 131: tool mounting portion 132, 133: bearing 138: wheel covers 140, 241-243, 341, 342, 441 to 444, 541, 542, 641, 642: Gas sensor 150, 350, 550: First operation unit 151, 351, 551: Trigger 152, 352, 552: Trigger switch 160, 360: Second operation unit 161, 361: reset buttons 162, 362: reset switches 170, 370, 470, 570: controller 171, 371: control circuits 173, 373: drive circuit 180, 380: warning lamp 280: buzzer 3: circular saw 303: handle housing 305: Blade cover 307: Base portion 308: Mounting surface 312, 313: Bearing 320: Transmission mechanism 330: Spindle 331: Tool mounting portion 4: Chain saw 405: Battery mounting portion 409: Guide bar 420: Transmission mechanism 430: Spindle 431 : Sprocket 432: Guide bar mounting parts 5, 6: Hammer drill 501: Drive mechanism housing 502: Motor housing 503: Handle housing 504: Auxiliary handle 505: Battery mounting part 530: Tool holder 531: Motion conversion mechanism 532: Drive gear 533: Impact element 535: Rotation transmission mechanism 81: Grinding stone 82: Saw blade 83: Chain blade 90: Battery 91, 92: Power cable

Claims (13)

A power tool configured to drive a tip tool,
Housing,
A motor arranged in the housing,
A plurality of detectors configured to detect a specific gas generated corresponding to the overheated state of the motor,
An electric power tool comprising: a control unit configured to limit the number of rotations of the motor according to the detection results of the plurality of detection units. The power tool according to claim 1, wherein
A fan disposed in the housing and driven by the motor,
The fan is configured to create an air flow through the housing in a predetermined path,
The power tool, wherein the plurality of detection units are arranged on the path. The electric tool according to claim 2,
The electric power tool, wherein the plurality of detection units are arranged in a downstream region of the path that includes a portion downstream of the motor in a direction in which the air flow flows. The electric tool according to claim 2 ,
The plurality of detection units,
Of the path, a downstream detection unit arranged in a downstream region including a portion downstream of the motor in the direction in which the air flow flows,
Of the path, including an upstream detection unit arranged in an upstream region including a portion on the upstream side of the motor in the direction in which the air flow flows,
The electric power tool, wherein the control unit is configured to limit the rotation speed according to detection results of both the upstream detection unit and the downstream detection unit. The power tool according to claim 4 ,
When the concentration of the specific gas detected by the downstream detection unit is higher than the concentration of the specific gas detected by the upstream detection unit, the control unit limits the rotation speed. An electric tool characterized by being configured. The power tool according to claim 5 ,
The control unit, the difference between the concentration of the specific gas detected by the downstream side detection unit and the concentration of the specific gas detected by the upstream side detection unit, a preset tolerance The electric power tool is configured so as to limit the number of revolutions when it exceeds. The power tool according to claim 1 , wherein
Before SL plurality of the detecting portion,
As the specific gas, in the overheated state, a first gas detection unit configured to detect a first gas generated corresponding to a first state in which the degree of overheating of the motor is lower,
As the specific gas, a second gas different from the first gas, which is generated corresponding to a second state in which the degree of overheating is higher than the first state among the overheated states, is detected. And a second gas detection unit configured in
The electric power tool, wherein the control unit is configured to limit the rotation speed according to the detection results of the first gas detection unit and the second gas detection unit. A power tool configured to drive a tip tool,
Housing,
A motor arranged in the housing,
A detection unit configured to detect a specific gas generated corresponding to the overheated state of the motor,
A control unit configured to limit the rotation speed of the motor according to the detection result by the detection unit;
A first operation unit configured to receive a drive instruction for normally driving the motor according to an external operation by an operator,
A second operation unit configured to receive an instruction to release the restriction on the rotation speed of the motor by the control unit according to an external operation by the worker ,
The control unit is
When the drive instruction is newly received by the first operation unit when the motor is placed in the limited state in which the rotation speed is limited, the limited state is maintained despite the drive instruction. And configured to
An electric power tool configured to release the restricted state when the cancellation instruction is received by the second operation unit while the motor is in the restricted state. A power tool configured to drive a tip tool,
Housing,
A motor arranged in the housing,
A detection unit configured to detect a specific gas generated corresponding to the overheated state of the motor,
A control unit configured to limit the rotation speed of the motor according to the detection result by the detection unit;
A first operation unit configured to receive a drive instruction for normally driving the motor according to an external operation by an operator,
The control unit is
When the drive instruction is newly received by the first operation unit when the motor is placed in the limited state in which the rotation speed is limited, the limited state is maintained despite the drive instruction. And configured to
When the motor is placed in the restricted state, if the concentration of the specific gas detected by the detection unit is lower than a preset allowable concentration, the restricted state is released. A power tool that is characterized by A power tool configured to drive a tip tool,
Housing,
A motor arranged in the housing,
A detection unit configured to detect a specific gas generated corresponding to the overheated state of the motor,
A control unit configured to limit the rotation speed of the motor according to the detection result by the detection unit;
A notification unit for notifying information according to the detection result,
With respect to the specific gas, a first allowable concentration and a second allowable concentration higher than the first allowable concentration are preset,
When the detection unit detects the specific gas exceeding the first allowable concentration, the notification unit notifies first information indicating that the specific gas exceeds the first allowable concentration. Is configured to
The electric power tool, wherein the control unit is configured to limit the rotational speed when the detection unit detects the specific gas exceeding the second allowable concentration. The power tool according to claim 10 , wherein
The notification unit, by the detection unit, when the specific gas exceeding the second allowable concentration is detected, second information indicating that the specific gas exceeds the second allowable concentration, An electric power tool, which is configured to notify in a manner different from the first information. The electric tool according to claim 7 ,
Further comprising an informing unit for informing information according to the detection result,
The first gas permissible concentration for the first gas and the second gas permissible concentration for the second gas are preset.
When the first gas detection unit detects the first gas that exceeds the first gas allowable concentration, the notification unit determines that the first gas exceeds the first gas allowable concentration. Configured to broadcast the first information shown,
The control unit is configured to limit the rotation speed when the second gas detecting unit detects the second gas that exceeds the second allowable gas concentration. Electric tool. The power tool according to claim 12 ,
When the second gas that exceeds the second gas allowable concentration is detected by the second gas detection unit, second information indicating that the second gas has exceeded the second gas allowable concentration. Is configured to be notified in a manner different from the first information.

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