Work machine

Abstract

To provide a work machine capable of preventing a discharge phenomenon in a filter by an inexpensive configuration.SOLUTION: A hydraulic shovel 1 includes an engine 16, a hydraulic oil tank 17 for storing hydraulic oil 20, a hydraulic actuator 29 driven by the hydraulic oil 20, a full flow filter 35 for removing a foreign matter mixed into the hydraulic oil 20 returned to the hydraulic oil tank 17 from the hydraulic actuator 29, and an antistatic device for preventing charging of the hydraulic oil 20, wherein the antistatic device includes an electric field discharge emitter 53 for applying a positive electric charge to the hydraulic oil 20, and an electric field discharge emitter control part 51 for controlling a voltage applied to the electric field discharge emitter 53, and the electric field discharge emitter 53 is provided on the upstream side of the flow of the hydraulic oil 20 from the full flow filter 35.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a work machine provided with a filter for removing foreign matter that gets mixed into hydraulic oil. [Background technology]

[0002] Work machines such as hydraulic excavators and wheel loaders use hydraulic pressure as a power source for work, and hydraulic oil is used to transmit pressure. The hydraulic oil is pressurized by a hydraulic pump, and after the pressure and flow rate are adjusted by a hydraulic valve, it is sent to hydraulic actuators such as hydraulic cylinders and hydraulic motors that drive the parts that perform the work, thereby transmitting power. After transmitting power, the hydraulic oil returns to the hydraulic oil tank, but because foreign matter such as dust can get into the hydraulic oil through gaps in the seals of the hydraulic actuators, a filter is required to remove foreign matter from the hydraulic oil.

[0003] However, when hydraulic oil passes through a filter, it becomes charged due to flow resistance (friction), and if the amount of charge becomes large, discharges can occur between the hydraulic oil and the filter, or between the hydraulic oil and other components, and unpleasant noises can occur as a secondary effect. Therefore, measures to prevent charging or discharge of hydraulic oil are needed.

[0004] An example of an anti-static device that prevents hydraulic oil from becoming electrostatically charged is the technology described in Patent Document 1. The anti-static device described in Patent Document 1 is configured by uniformly and densely mixing carbon fibers into the filtering material of the filter, and by making the filter conductive, it is possible to release the electrostatic charge generated in the hydraulic oil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-52718 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the anti-static device described in Patent Document 1 has the problem of increasing costs because it requires a complicated manufacturing process of uniformly and densely mixing carbon fibers into the filter material to make the filter conductive.In addition, because the filter is made up of a combination of multiple parts, including the filter material, the joints and combinations of these parts must be electrically connected, which also increases costs.

[0007] The present invention has been made in view of the current state of the prior art, and an object of the present invention is to provide a work machine that can prevent discharge phenomena in a filter with an inexpensive configuration. [Means for solving the problem]

[0008] In order to achieve the above object, a representative aspect of the present invention is a work machine comprising a prime mover, a hydraulic oil tank for storing hydraulic oil, a hydraulic actuator driven by the hydraulic oil, a filter for removing foreign matter mixed into the hydraulic oil returning from the hydraulic actuator to the hydraulic oil tank, and an anti-static device for preventing the hydraulic oil from becoming charged, wherein the anti-static device comprises a field emission emitter for applying a positive charge to the hydraulic oil, and a control unit for controlling the voltage applied to the field emission emitter, and the field emission emitter is provided upstream of the filter in the flow of the hydraulic oil. [Effects of the Invention]

[0009] According to the work machine of the present invention, it is possible to prevent discharge phenomena in the filter with an inexpensive configuration. Note that problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing the appearance of a hydraulic excavator according to an embodiment of the present invention. [Figure 2]FIG. 2 is a block diagram of a hydraulic system showing a circulation system of hydraulic oil. [Figure 3] FIG. 2 is an explanatory diagram showing the configuration of a hydraulic oil tank and a full-flow filter. [Figure 4] 10 is a flowchart showing a control processing operation of a field emission emitter control unit. [Figure 5] FIG. 10 is a block diagram of a hydraulic system according to a first modified example. [Figure 6] 10 is a flowchart showing the control processing operation of a field emission emitter control section in Modification 1. [Figure 7] 10 is a flowchart showing the control processing operation of a field emission emitter control section in Modification 2. [Figure 8] 13 is a flowchart showing the control processing operation of a field emission emitter control section in Modification 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a hydraulic excavator will be described as an example of a working machine according to an embodiment of the present invention.

[0012] Fig. 1 is a perspective view showing the appearance of a hydraulic excavator according to this embodiment. As shown in Fig. 1, the hydraulic excavator 1 includes a self-propelled lower traveling body 2, an upper rotating body 3 mounted on the lower traveling body 2 so as to be able to rotate freely, and a front work unit 4 attached to the front of the upper rotating body 3 so as to be able to move up and down (rotate).

[0013] The lower traveling body 2 has crawler-type traveling devices on both the left and right sides (only the left side is shown in FIG. 1), and the left and right traveling devices are each driven by a traveling motor 5 serving as a hydraulic actuator. The upper rotating body 3 is driven to rotate relative to the lower traveling body 2 by a swing motor 6 serving as a hydraulic actuator.

[0014] The front work device 4 is an articulated work device for performing work such as excavation work, and is composed of, for example, a boom 7, an arm 8, and a bucket 9 as a work implement. The base end of the boom 7 is rotatably attached to the front of the upper rotating body 3. The base end of the arm 8 is rotatably attached to the tip of the boom 7. The base end of the bucket 9 is rotatably attached to the tip of the arm 8. The boom 7, arm 8, and bucket 9 are driven by a boom cylinder 10, an arm cylinder 11, and a bucket cylinder 12, which serve as hydraulic actuators, respectively.

[0015] The upper rotating body 3 is provided with an operator's cab 13 where an operator sits. An operating device 14 that is operated by the operator is disposed inside the cab 13. The operating device 14 accepts operations by the operator to operate the hydraulic excavator 1. When the operator operates the operating device 14, the lower traveling body 2 travels, the upper rotating body 3 rotates, and the front work unit 4 operates.

[0016] Furthermore, a fuel tank 15, an engine (prime mover) 16, a hydraulic oil tank 17, a hydraulic pump 21, etc. are arranged inside the upper rotating body 3. The fuel tank 15 stores fuel to be supplied to the engine 16. The engine 16 generates driving force for operating the hydraulic excavator 1. The hydraulic oil tank 17 stores hydraulic oil to be supplied to the hydraulic pump 21. The hydraulic pump 21 rotates when the driving force of the engine 16 is transmitted to it, and supplies the hydraulic oil stored in the hydraulic oil tank 17 to the hydraulic actuators (travel motor 5, swing motor 6, boom cylinder 10, arm cylinder 11, bucket cylinder 12). Note that instead of the engine 16, an electric motor or the like may be used as the prime mover.

[0017] Fig. 2 is a block diagram of a hydraulic system showing a hydraulic oil circulation system. As shown in Fig. 2, this hydraulic system includes a hydraulic oil tank 17, a suction filter 31, a hydraulic pump 21, a motor 22, a hydraulic actuator 29, an oil cooler 28, a full-flow filter 35, a field emission emitter control unit 51, a field emission emitter 53, and a voltage sensor 55.

[0018] Hydraulic oil 20 is stored in hydraulic oil tank 17. An air breather 23 is attached to the top of hydraulic oil tank 17, and the air breather 23 removes dust and foreign matter from the outside air. A suction filter 31 is provided on the inner bottom of hydraulic oil tank 17. Suction filter 31 is a filter that removes foreign matter in hydraulic oil 20 to prevent it from entering hydraulic pump 21, thereby protecting hydraulic pump 21.

[0019] The hydraulic pump 21 is driven by a motor 22 and supplies hydraulic oil 20 stored in a hydraulic oil tank 17 to a hydraulic actuator 29. The hydraulic oil 20 supplied to the hydraulic actuator 29 returns to the hydraulic oil tank 17 from an oil cooler 28 via a pipe 50. The oil cooler 28 cools the hydraulic oil 20. The hydraulic oil 20 supplied to the hydraulic actuator 29 also returns to the hydraulic oil tank 17 from the oil cooler 28 via a flow control valve 27 and a bypass filter 46.

[0020] The full-flow filter 35 is a filter that removes (purifies) foreign matter that gets mixed into the hydraulic oil 20 that returns to the hydraulic oil tank 17 via the pipe 50, and is provided at the discharge port of the pipe 50. The structure of the full-flow filter 35 will be described later.

[0021] Field emitter 53 includes an electrical component that applies a positive charge to hydraulic oil 20, and the component is shaped like a tungsten needle with a sharp tip, or a carbon nanotube. The voltage applied to the electrode of field emitter 53 to positively charge hydraulic oil 20 is preferably +1 kV to +10 kV in the case of a tungsten needle, and +100 V to +3 kV in the case of a carbon nanotube. Field emitter 53 is connected to field emitter control unit 51 via wiring 52.

[0022] When the hydraulic oil 20 is charged due to flow resistance as it passes through the full-flow filter 35, a negative charge is generated, and the negative charge is then applied to the filter material (described later) of the full-flow filter 35. The voltage sensor 55 is a sensor that detects the amount of charge on the full-flow filter 35, and is provided at an appropriate location on the full-flow filter 35. The voltage sensor 55 is connected to the field emitter control unit 51 via wiring 54.

[0023] The field emission emitter control unit 51 controls the voltage output to the field emission emitter 53 based on the detection value of the voltage sensor 55. The field emission emitter control unit 51, the field emission emitter 53, and the voltage sensor 55 constitute an anti-static device that prevents charging of the hydraulic oil 20. The control processing operation of the field emission emitter control unit 51 will be described later.

[0024] FIG. 3 is an explanatory diagram showing the configuration of the hydraulic oil tank 17 and the full-flow filter 35 provided in the hydraulic system of FIG.

[0025] As shown in Fig. 3, a suction filter 31 and a full-flow filter 35 are installed in the hydraulic oil tank 17. The suction filter 31 is attached to the lower end of a support rod 32, and is positioned above the oil supply port at the bottom of the hydraulic oil tank 17. The support rod 32 is fixed to a tank lid 33 provided on the upper wall of the hydraulic oil tank 17.

[0026] The full-flow filter 35 includes a storage case 19 installed on top of the hydraulic oil tank 17 and a filter medium 39 placed inside the storage case 19. The storage case 19 is formed in a cylindrical shape with a bottom surface, and is fixed to the upper wall of the hydraulic oil tank 17 and extends downward inside. The top surface of the storage case 19 is open, and this opening is closed by a lid 34 that can be opened and closed.

[0027] The filter material 39 is a hollow cylindrical body made of cellulose, synthetic fiber, or the like, and is detachably disposed inside the storage case 19. A spring 36 is disposed between the filter material 39 and the lid 34, and the filter material 39 is stably supported inside the storage case 19 by the elastic force of the spring 36. A bypass valve 38 incorporating a fixed spring 37 is provided at the upper end of the interior of the filter material 39. The bypass valve 38 opens to ensure a flow path for the hydraulic oil 20 when the filter material 39 becomes clogged.

[0028] The piping 50 is connected to the outer peripheral surface of the storage case 19. The hydraulic oil 20 returning from the hydraulic actuator 29 to the hydraulic oil tank 17 flows into the interior of the storage case 19 through the piping 50. The hydraulic oil 20 that has flowed into the interior of the storage case 19 passes through the filter medium 39 from the outside to the inside, and is then discharged from the bottom of the storage case 19 into the hydraulic oil tank 17.

[0029] The field emitter 53 is provided near the discharge port of the pipe 50 upstream of the full-flow filter 35. The field emitter 53 may be provided anywhere upstream of the filter medium 39 of the full-flow filter 35, and therefore may be provided in the storage case 19 instead of the pipe 50. Although not shown, a voltage sensor 55 is provided at an arbitrary position on the filter medium 39 arranged in the storage case 19. In Fig. 3, arrow 60 indicates the flow of the hydraulic oil 20, and arrow 61 indicates the flow of the hydraulic oil 20 passing through the filter medium 39.

[0030] Fig. 4 is a flowchart showing the control processing operation of the field emission emitter control unit 51. As shown in Fig. 4, first, when the engine 16 is operated to start the hydraulic excavator 1 (step S1), the field emission emitter control unit 51 reads a detection signal from the voltage sensor 55 (step S2).

[0031] Next, the field emission emitter control unit 51 determines whether the detection result of the voltage sensor 55 is equal to or greater than a preset reference value (threshold value) (step S3). In step S3, if the detection value of the voltage sensor 55 is equal to or greater than the threshold value (YES), that is, if the amount of charge on the filter medium 39 of the full-flow filter 35 has increased, the field emission emitter control unit 51 outputs a voltage to the field emission emitter 53 (step S4), and then proceeds to step S5. As a result, the field emission emitter 53 applies a positive charge to the hydraulic oil 20 passing through the piping 50.

[0032] The hydraulic oil 20 to which a positive charge has been applied flows into the storage case 19 of the full-flow filter 35, and when it passes through the negatively charged filter material 39, it receives a negative charge from the filter material 39 due to friction. This causes the positively charged state and the negatively charged state to cancel each other out, preventing discharge within the full-flow filter 35.

[0033] On the other hand, in step S3, if the detection value of the voltage sensor 55 is below the threshold value (NO), that is, if the amount of charge on the filter material 39 of the full-flow filter 35 is small and there is no risk of a discharge phenomenon occurring, the field emission emitter control unit 51 does not output a voltage to the field emission emitter 53 and proceeds directly to step S5.

[0034] In step S5, if the engine 16 continues to operate (NO in step S5), the process returns to step S2. Then, when the engine 16 is stopped and the hydraulic excavator 1 is brought to a standstill (YES in step S5), the activation of the field emitter 53 is also stopped.

[0035] In the hydraulic excavator (work machine) 1 configured in this manner, the anti-static device that prevents the hydraulic oil 20 from becoming charged includes a field emission emitter 53 that applies a positive charge to the hydraulic oil 20 and a field emission emitter control unit 51 that controls the voltage applied to the field emission emitter 53, and since this field emission emitter 53 is provided in the piping 50 upstream of the full-flow filter 35, the positive charge that is charged to the hydraulic oil 20 before it flows into the full-flow filter 35 and the negative charge that is charged to the full-flow filter 35 cancel each other out, thereby preventing discharge within the full-flow filter 35.

[0036] In addition, the anti-static device further includes a voltage sensor 55 capable of detecting the amount of charge on the full-flow filter 35, and when the detection result of this voltage sensor 55 exceeds a reference value, the field emission emitter control unit 51 applies a voltage to the field emission emitter 53, so that a positive charge can be efficiently applied to the hydraulic oil 20 at the time when the amount of charge on the full-flow filter 35 increases to a preset reference value.

[0037] Next, various modifications of this embodiment will be described.

[0038] (Variation 1) Fig. 5 is a block diagram of a hydraulic system according to Modification 1. As shown in Fig. 5, in Modification 1, a detection signal from a sound collection sensor 56, instead of a voltage sensor 55, is taken into a field emitter control unit 51. In Fig. 5, parts corresponding to those in Fig. 2 are given the same reference numerals.

[0039] When the hydraulic oil 20 passes through the filter material 39, the frictional resistance increases the amount of charge on the full-flow filter 35, causing unpleasant noise to be generated in the hydraulic oil tank 17. The sound collection sensor 56 is a sensor that detects the volume of such abnormal noise generated in the hydraulic oil tank 17, and is provided at an appropriate location on the upper inner wall of the hydraulic oil tank 17. The sound collection sensor 56 and the voltage sensor 55 are connected to the field emitter control unit 51 via wiring 57.

[0040] Fig. 6 is a flowchart showing the control processing operation of the field emission emitter control unit 51 in Modification 1. As shown in Fig. 6, when the engine 16 is operated to start the hydraulic excavator 1 (step S11), the field emission emitter control unit 51 reads a detection signal from the sound collection sensor 56 (step S12).

[0041] Next, the field emission emitter control unit 51 determines whether the detection result of the sound collection sensor 56 is equal to or greater than a preset reference value (threshold value) (step S13). If the detection value of the sound collection sensor 56 is equal to or greater than the threshold value (YES) in step S13, that is, if the charge amount of the full-flow filter 35 has increased and abnormal noise of a volume equal to or greater than a predetermined value is occurring in the hydraulic oil tank 17, the field emission emitter control unit 51 outputs a voltage to the field emission emitter 53 (step S14), and then proceeds to step S15. As a result, the field emission emitter 53 applies a positive charge to the hydraulic oil 20 passing through the piping 50.

[0042] The positively charged hydraulic oil 20 flows into the storage case 19 of the full-flow filter 35, and when it passes through the negatively charged filter material 39, it receives a negative charge from the filter material 39 due to friction. This causes the positively charged state and the negatively charged state to cancel each other out, preventing discharge within the full-flow filter 35.

[0043] On the other hand, in step S13, if the detection value of the sound collection sensor 56 is below the threshold value (NO), that is, if the amount of charge on the full-flow filter 35 is small and no abnormal noise of a volume above a predetermined value is occurring in the hydraulic oil tank 17, the field emission emitter control unit 51 does not output voltage to the field emission emitter 53 and proceeds directly to step S15.

[0044] In step S15, if the engine 16 continues to operate (NO in step S15), the process returns to step S12. Then, when the engine 16 is stopped and the hydraulic excavator 1 is brought to a standstill (YES in step S15), the activation of the field emitter 53 is also stopped.

[0045] Even in the modified example 1 configured as above, when the detection result of the sound collection sensor 56 exceeds the reference value, the field emission emitter control unit 51 applies a voltage to the field emission emitter 53, so that the same effect as that of the present embodiment can be achieved.

[0046] (Variation 2) The hydraulic system according to the second modification is provided with a temperature sensor (not shown) that detects the temperature of the hydraulic oil 20, and the detection signal of this temperature sensor is taken in by the field emission emitter control unit 51.

[0047] Immediately after starting up the hydraulic excavator 1 that has been stopped for a long time, the temperature of the hydraulic oil 20 in the hydraulic oil tank 17 is relatively low and the viscosity of the hydraulic oil 20 is also high. Under such conditions, the hydraulic oil 20 and the filter material 39 of the full-flow filter 35 are likely to become frictionally charged, so in Modification 2, a voltage is output to the field emission emitter 53 based on the detection result of the temperature sensor.

[0048] Fig. 7 is a flowchart showing the control processing operation of the field emission emitter control unit 51 in Modification 2. As shown in Fig. 7, when the engine 16 is operated to start the hydraulic excavator 1 (step S21), the field emission emitter control unit 51 reads a detection signal from the temperature sensor (step S22).

[0049] Next, the field emission emitter control unit 51 determines whether the detection result of the temperature sensor is equal to or less than a preset reference value (threshold value) (step S23). If the detection value of the temperature sensor is equal to or less than the threshold value (YES) in step S23, that is, if the temperature of the hydraulic oil 20 in the hydraulic oil tank 17 is relatively low and the hydraulic oil 20 and the filter medium 39 of the full-flow filter 35 are likely to be frictionally charged, the field emission emitter control unit 51 outputs a voltage to the field emission emitter 53 (step S24), and then proceeds to step S15. As a result, the field emission emitter 53 applies a positive charge to the hydraulic oil 20 passing through the piping 50.

[0050] The positively charged hydraulic oil 20 flows into the storage case 19 of the full-flow filter 35, and when it passes through the negatively charged filter material 39, it receives a negative charge from the filter material 39 due to friction. This causes the positively charged state and the negatively charged state to cancel each other out, preventing discharge within the full-flow filter 35.

[0051] On the other hand, in step S23, if the detected value of the temperature sensor is equal to or greater than the threshold value (NO), that is, if the temperature of the hydraulic oil 20 in the hydraulic oil tank 17 is relatively high and the hydraulic oil 20 and the filter material 39 of the full-flow filter 35 are not easily frictionally charged, the field emission emitter control unit 51 does not output a voltage to the field emission emitter 53, and proceeds directly to step S25.

[0052] In step S25, if the engine 16 continues to operate (NO in step S25), the process returns to step S22. Then, when the engine 16 is stopped and the hydraulic excavator 1 is brought to a standstill (YES in step S25), the activation of the field emitter 53 is also stopped.

[0053] Even in the modified example 2 configured in this manner, when the detection result of the temperature sensor is equal to or lower than the reference value, the field emission emitter control unit 51 applies a voltage to the field emission emitter 53, so that the same effect as that of the present embodiment can be achieved.

[0054] (Variation 3) The hydraulic system according to the third modification is provided with a timer (not shown) that measures the time that has elapsed since the engine 16 started operating, and the detection signal of this timer is taken into the field emission emitter control unit 51.

[0055] As mentioned above, immediately after starting up the hydraulic excavator 1 that has been stopped for a long time, the temperature of the hydraulic oil 20 in the hydraulic oil tank 17 is relatively low, creating conditions that make it easy for the full-flow filter 35 to become electrically charged. However, as time passes after the hydraulic excavator 1 is started up, the temperature of the hydraulic oil 20 rises, making it difficult for the hydraulic oil 20 and the filter material 39 of the full-flow filter 35 to become electrically charged by friction. Therefore, in Modification 3, a voltage is output to the field emitter 53 when the engine 16 is operating, and the voltage output to the field emitter 53 is stopped based on the detection result of the timer.

[0056] Fig. 8 is a flowchart showing the control processing operation of the field emission emitter control unit 51 in Modification 3. As shown in Fig. 8, when the engine 16 is operated to start the hydraulic excavator 1 (step S31), a voltage is output from the field emission emitter control unit 51 to the field emission emitter 53 (step S32).

[0057] Next, the field emitter control section 51 reads the detection signal of the timer (step S33), and then determines whether the detection result of the timer is equal to or less than a preset reference value (threshold value) (step S34).

[0058] In step S34, if the detected value of the timer is below the threshold value (NO), that is, if the time that has elapsed since the hydraulic excavator 1 was started is short and the hydraulic oil 20 and the filter material 39 of the full-flow filter 35 are in a condition that makes it easy for frictional charging to occur, the process returns to step S32 and voltage output to the field emission emitter 53 continues.

[0059] On the other hand, if the detected value of the temperature sensor is equal to or greater than the threshold value in step S33 (YES), that is, if the time elapsed since the start of the hydraulic excavator 1 becomes long and the full-flow filter 35 is placed under conditions that make it difficult for it to be charged, the field emission emitter control unit 51 stops outputting voltage to the field emission emitter 53 (step S35). Then, when the engine 16 stops (step S36), the above processing operation of the field emission emitter control unit 51 also stops.

[0060] Even in the third modification configured as above, a voltage is output to the field emission emitter 53 after the engine 16 is started, and when the elapsed time after the engine is started exceeds a reference value, the voltage output to the field emission emitter 53 is stopped, so that the same effects as those of the present embodiment can be achieved.

[0061] It should be noted that the above-described embodiments are merely examples for explaining the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention.

[0062] For example, in the above embodiment, a hydraulic excavator has been described as an example of one aspect of the work machine of the present invention, but the present invention is not limited to this and may also be a wheel loader or the like. [Explanation of symbols]

[0063] 1. Hydraulic excavator (work machine) 2 Undercarriage 3 Upper rotating body 4. Work Front 5 Travel motor (hydraulic actuator) 6 Swing motor (hydraulic actuator) 10 Boom cylinder (hydraulic actuator) 11 Arm cylinder (hydraulic actuator) 12 Bucket cylinder (hydraulic actuator) 16 Engine (prime mover) 17 Hydraulic oil tank 19 Storage Case 20 Hydraulic oil 21 Hydraulic pump 29 Hydraulic Actuator 34 Lid 35 Full flow filter (filter) 39 Filter media 50 Piping 51 Field emission emitter control section 53 Field emitter 55 Voltage Sensor

Claims

1. A work machine comprising: a prime mover; a hydraulic oil tank for storing hydraulic oil; a hydraulic actuator driven by the hydraulic oil; a filter for removing foreign matter mixed into the hydraulic oil returning from the hydraulic actuator to the hydraulic oil tank; and an anti-static device for preventing the hydraulic oil from becoming electrically charged, the anti-static device includes a field emitter that applies a positive charge to the hydraulic oil, and a control unit that controls a voltage applied to the field emitter; The field emitter is provided upstream of the filter in the flow of the hydraulic oil. A work machine characterized by:

2. 2. The work machine according to claim 1, a voltage sensor capable of detecting the amount of charge on the filter; the control unit applies a voltage to the field emission emitter when the detection result of the voltage sensor exceeds a reference value. A work machine characterized by:

3. 2. The work machine according to claim 1, a sound collection sensor capable of detecting the volume of sound generated in the hydraulic oil tank; The control unit applies a voltage to the field emitter when the detection result of the sound collection sensor exceeds a reference value. A work machine characterized by:

4. 2. The work machine according to claim 1, a temperature sensor capable of detecting the temperature of the hydraulic oil stored in the hydraulic oil tank; the control unit applies a voltage to the field emission emitter when the detection result of the temperature sensor is equal to or less than a reference value. A work machine characterized by:

5. 2. The work machine according to claim 1, a timer capable of measuring the elapsed time after the operation of the prime mover; the control unit applies a voltage to the field emission emitter when the motor starts operating, and stops applying the voltage to the field emission emitter when the detection result of the timer exceeds a reference value. A work machine characterized by:

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