Work machine

Abstract

To improve convenience of a work machine.SOLUTION: A nail driving machine 10 comprises: a hollow case part including a cylinder 27; and a piston part 28 which defines a pressure chamber 26 in the case part, and moves to a lower side by a pressure of a gas in the pressure chamber 26, thereby striking a fastener. The piston part 28 has: a base member having a side wall; an X ring 41 which is attached to the base member so as to be interposed between the side wall and the cylinder 27; and an O ring 42 which is interposed between the side wall and the cylinder 27, and is attached at a different position in a vertical direction M1 with respect to the X ring 41. The X ring 41 has a first base part, and a lip part which is erected from the first base part and contacts the cylinder 27. The O ring 42 has a second base part, and does not have a lip part which is erected from the second base part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a work machine such as a nail driver. [Background technology]

[0002] As an example of a work machine, a fastener driver is known that has a cylindrical cylinder, a piston that reciprocates within the cylinder, a striking portion that strikes a fastener by the downward movement of the piston, and a sealing member provided on the piston.

[0003] As an example of the above-mentioned driving machine, Patent Document 1 discloses a working machine (driving machine) in which an X-ring is provided on the piston as the sealing member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 100943 Summary of the Invention [Problem to be solved by the invention]

[0005] In the driving machine described in the above-mentioned Patent Document 1, an X-ring is provided on the piston as a sealing member to prevent air leakage from the contact surface between the piston and the cylinder. However, the X-ring hardens at low temperatures, which can reduce the sealing ability of the X-ring.

[0006] The deterioration of the sealing ability of the X-ring at low temperatures can be improved by increasing the interference between the X-ring and the cylinder inner wall (the ratio of the compression amount to the wire diameter of the X-ring), but in that case, the lubricant applied to the cylinder inner wall is scraped out and the oil film breaks at room temperature. When the oil film breaks, the sealing ability enhanced by the oil film decreases, causing air leakage.

[0007] If an air leak occurs, the worker must stop the driving operation to replenish the air, which may result in a loss of usability of the driving tool.

[0008] An object of the present invention is to provide a work machine with improved convenience. [Means for solving the problem]

[0009] A working machine in one embodiment includes a hollow case portion including a cylinder having a cylindrical shape extending in a first direction and an inner wall, and a piston portion movable in the first direction inside the cylinder, cooperating with the case portion to define a pressure chamber inside the case portion, and moving to one side in the first direction due to the pressure of gas inside the pressure chamber to strike a stopper, the piston portion including a base member having a side wall facing the inner wall of the cylinder, a first seal member attached to the base member so as to be interposed between the side wall and the inner wall, and a second seal member attached to the base member so as to be interposed between the side wall and the inner wall and positioned at a different position in the first direction relative to the first seal member, wherein the first seal member has a first base and a lip portion standing upright from the first base and in contact with the cylinder in a cross-sectional view of a cut surface parallel to the first direction, and the second seal member has a second base and does not have a lip portion standing upright from the second base in the cross-sectional view. Effect of the Invention

[0010] According to the present invention, the convenience of a work machine can be improved. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional side view of a structure of a working machine according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of the structure of the working machine shown in FIG. 1 as viewed from the front. [Diagram 3]2 is a partially enlarged cross-sectional view showing a piston and its surrounding structure which are assembled to the working machine shown in FIG. 1. [Figure 4] FIG. 4 is a perspective view showing the shape of an X-ring provided on the piston shown in FIG. [Diagram 5] FIG. 5 is a side view showing the shape of the X-ring shown in FIG. 4. [Figure 6] 6 is a cross-sectional view showing the structure cut along the line AA in FIG. 5. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing the structure of part B in FIG. [Figure 8] 4 is a cross-sectional view showing the shape of an O-ring provided on the piston shown in FIG. 3. [Figure 9] FIG. 9 is a partial cross-sectional view showing an interference caused by an O-ring shown in FIG. 8. [Figure 10] 4 is a partially enlarged cross-sectional view showing a structure in which a seal member of a first modified example is provided on the piston shown in FIG. 3. FIG. [Figure 11] 11 is a partially enlarged cross-sectional view showing the shape of a seal member (V ring) of a first modified example shown in FIG. [Figure 12] 4 is a partially enlarged cross-sectional view showing a structure in which a seal member (D ring) of a second modified example is provided on the piston shown in FIG. 3. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of a nail driver (working machine) according to the present invention will be described with reference to the drawings.

[0013] (Embodiment) 1 and 2 is an air compression type working machine also called a driving machine, and has a housing 11, a striking unit 12, a nose unit 13, a power supply unit 14, an electric motor 15, a winding mechanism 17, and a pressure accumulator 18. The housing 11 is an outer shell element of the nail driver 10, and has a cylinder case 19, a handle 20, a motor case 21, and a mounting unit 22. The cylinder case 19 is cylindrical, and the handle 20 and the motor case 21 are connected to the cylinder case 19. In addition, the mounting unit 22 is connected to the handle 20 and the motor case 21.

[0014] The power supply unit 14 can be attached to and detached from the mounting portion 22. The electric motor 15 is disposed in a motor case 21. A head cover 25 is provided on the cylinder case 19, and the pressure accumulator vessel 18 is disposed throughout the cylinder case 19 and the head cover 25.

[0015] Furthermore, a cylindrical cylinder 27 extending in the vertical direction (first direction) M1 is housed within the cylinder case 19, and the pressure accumulator vessel 18 has a cap 23 and a holder 24 attached to the cylinder 27, and is a vessel that closes an upper (other) end of the cylinder 27 in the vertical direction (first direction) M1 and whose interior communicates with the interior of the cylinder 27. The cylinder 27 is made of metal, for example, aluminum or iron. The cylinder 27 is positioned relative to the cylinder case 19 in the direction along a center line A1 and in the radial direction. The center line A1 passes through the center of the cylinder 27. The radial direction is the radial direction of an imaginary circle centered on the center line A1.

[0016] Further, a pressure chamber 26 is formed throughout the pressure accumulator container 18 and the cylinder 27. Specifically, the pressure accumulator container 18 and the cylinder 27 are hollow case parts, and the pressure chamber 26 formed between the pressure accumulator container 18 and the cylinder 27 is filled with compressed gas. The compressed gas may be air or an inert gas. Examples of the inert gas include nitrogen gas and rare gas. In this embodiment, an example in which the pressure chamber 26 is filled with air will be described. The pressure chamber 26 is also a biasing part that biases the striking part 12 downward (one side) in the up-down direction (first direction) M1.

[0017] The striking portion 12 is disposed from the inside to the outside of the housing 11. The striking portion 12 has a piston portion 28 and a driver blade 29. The driver blade 29 is made of, for example, metal, non-ferrous metal, or steel. The piston portion 28 and the driver blade 29 are provided as separate members, and the piston portion 28 and the driver blade 29 are connected to each other.

[0018] The piston portion 28 is operable in the cylinder 27 in a direction along the center line A1. Specifically, the piston portion 28 is movable in the vertical direction (first direction) M1 inside the cylinder 27, and defines a pressure chamber 26 inside the pressure accumulator container 18 and the cylinder 27 in cooperation with the pressure accumulator container 18 and the cylinder 27. The piston portion 28 strikes the nail (fastener) 78 by moving downward (one side) in the vertical direction (first direction) M1 due to the pressure of the compressed air in the pressure chamber 26. In other words, the striking portion 12 consisting of the piston portion 28 and the driver blade 29 strikes the nail (fastener) 78 by moving downward (one side) in the vertical direction (first direction) M1 due to the pressure of the compressed air in the pressure chamber 26.

[0019] An annular seal member is attached to the outer circumferential surface of the piston portion 28 that faces the cylinder 27. This seal member abuts against an inner wall 27a of the cylinder 27 to suppress air leakage from within the cylinder 27. The seal member attached to the piston portion 28 will be described in detail later.

[0020] The nose portion 13 of the nail driver 10 is disposed across the inside and outside of the cylinder case 19. The nose portion 13 has a bumper support portion 31, an injection portion 32, and a tube portion 33. The bumper support portion 31 is tubular. A bumper 35 is disposed within the bumper support portion 31. The bumper 35 may be made of either synthetic rubber or silicone rubber. The bumper 35 has a guide hole 36. The center line A1 passes through the guide hole 36. The driver blade 29 is disposed within the guide hole 31a of the bumper support portion 31 and within the guide hole 36.

[0021] The striking section 12 can operate in a striking direction D1 and a return direction D2 along the center line A1. The striking direction D1 and the return direction D2 are opposite to each other. The striking direction D1 is the direction in which the piston section 28 approaches the bumper 35. The return direction D2 is the direction in which the piston section 28 moves away from the bumper 35. The striking section 12 is constantly biased in the striking direction D1 by the gas pressure in the pressure chamber 26. The striking section 12 operating in the striking direction D1 can be defined as a downward movement. The striking section 12 operating in the return direction D2 can be defined as an upward movement. The striking direction D1 is the same as the lower (one side) of the vertical direction (first direction) M1. The return direction D2 is the same as the upper (other side) of the vertical direction (first direction) M1.

[0022] Furthermore, the ejection portion 32 is connected to the bumper support portion 31 and protrudes from the bumper support portion 31 in a direction along the center line A1. The ejection portion 32 has an ejection passage 37 that is provided along the center line A1. The driver blade 29 can operate in the ejection passage 37 in a direction along the center line A1.

[0023] The electric motor 15 is disposed within the motor case 21. The electric motor 15 has a rotor 39 and a stator 40. The stator 40 is attached to the motor case 21. The rotor 39 is rotatably supported by the motor case 21 via a bearing 38. The electric motor 15 is, for example, a brushless motor, and when a voltage is applied to the electric motor 15, the motor shaft 47 rotates together with the rotor 39 about a center line A2. As shown in FIG. 2, the center line A2 is shifted from the center line A1 in the left-right direction R1.

[0024] Furthermore, a reduction gear mechanism 45 is provided inside the motor case 21. The reduction gear mechanism 45 includes a plurality of planetary gear mechanisms. A rotating shaft 46 connected to a motor shaft 47 is provided inside the cylindrical portion 33. The rotating shaft 46 and the reduction gear mechanism 45 are arranged concentrically about the center line A2. The reduction gear mechanism 45 is disposed on a power transmission path from the electric motor 15 to the rotating shaft 46, and is a mechanism that reduces the speed of rotation of the rotor 39 of the electric motor 15 and transmits the rotation to the winding mechanism 17.

[0025] The winding mechanism 17 is a mechanism that converts the rotational force of the rotating shaft 46 into a force that biases the striking unit 12 in the return direction D2. As shown in FIG. 2, the winding mechanism 17 includes the driver blade 29, a plurality of racks 29a provided on the driver blade 29, a pinwheel 50 that is a rotating unit, and a plurality of pins 50a provided on the pinwheel 50. When the pinwheel 50 rotates in the rotational direction E1 by the driving force of the electric motor 15, the plurality of pins 50a of the pinwheel 50 and the plurality of racks 29a of the driver blade 29 sequentially engage with each other, and the striking unit 12 including the driver blade 29 is pushed upward (in the return direction D2). A position detection switch 72 that detects the position of the driver blade 29 in the up-down direction (first direction) M1 is provided in the ejection unit 32.

[0026] 1, the nail driver 10 is provided with a trigger 75 and a trigger switch 71. The trigger 75 and the trigger switch 71 are provided on the handle 20. The trigger switch 71 detects the presence or absence of an operating force applied to the trigger 75, and outputs a signal according to the detection result.

[0027] The power supply unit 14 has a housing case 76 and a battery housed in the housing case 76. The battery has a plurality of battery cells. These battery cells are secondary batteries that can be charged and discharged, and any known battery cell can be used, such as a lithium ion battery, a nickel metal hydride battery, a lithium ion polymer battery, or a nickel cadmium battery.

[0028] The electric motor 15 is operated by power supplied from the battery attached to the attachment portion 22 of the housing 11. A control unit 73 is housed inside the attachment portion 22. The control unit 73 includes a microcomputer composed of a CPU, ROM, RAM, etc., and controls the electric motor 15. Specifically, the control unit 73 changes the duty ratio of the motor current supplied to the electric motor 15 according to the control mode. In other words, the control unit 73 controls the electric motor 15 by PWM (Pulse Width Modulation).

[0029] As shown in FIG. 2, the nail driver 10 is provided with a magazine 77. The magazine 77 is supported by the ejection unit 32 and the mounting unit 22. Nails (fasteners) 78 are loaded in the magazine 77. The magazine 77 has a feeder, which sends the nails 78 in the magazine 77 to the ejection path 37. That is, the feeder moves the nails 78 in the magazine 77 forward in the front-rear direction N1 shown in FIG. 1. The ejection unit 32 is made of metal or synthetic resin. A push lever 79 is attached to the ejection unit 32. The push lever 79 can be operated within a predetermined range in a direction along the center line A1 relative to the ejection unit 32. An elastic member (not shown) is provided to bias the push lever 79 in a direction along the center line A1. The elastic member is, for example, a metal spring, and biases the push lever 79 in a direction away from the bumper support unit 31.

[0030] The push lever 79 can be switched between ON and OFF by being pressed by the operator against the mating material 30. When the push lever 79 is pressed against the mating material 30 and moves upward against the bias of the spring, a signal is output. When the operator operates the trigger 75, the trigger switch 71 built into the handle 20 is actuated, and a signal for the driving operation is output.

[0031] When both the signal by the operation of the push lever 79 and the signal by the operation of the trigger 75 are input, the control unit 73 supplies a motor current to the electric motor 15 to operate the electric motor 15. This rotates the pinwheel 50, pushes up the driver blade 29, and moves the piston unit 28 from the bottom dead center to the top dead center. Then, the driver blade 29 provided on the piston unit 28 is disengaged from the pinwheel 50 at the top dead center and released. With the release of the driver blade 29, the air pressure from the pressure chamber 26 causes the striking unit 12 including the driver blade 29 to start descending and move from the top dead center toward the bottom dead center. In other words, the striking unit 12 consisting of the piston unit 28 and the driver blade 29 reciprocates between the bottom dead center and the top dead center, and the nail 78 is struck by the driver blade 29, and the nail 78 is driven out.

[0032] Next, a seal member provided in the piston portion 28 of the nail driver 10 will be described. As shown in Fig. 3, the piston portion 28 includes a base member 28a having a side wall 28b facing the inner wall 27a of the cylinder 27. The piston portion 28 further includes a first seal member attached to the base member 28a so as to be interposed between the side wall 28b and the inner wall 27a, and a second seal member attached to the base member 28a so as to be interposed between the side wall 28b and the inner wall 27a and disposed at a different position in the up-down direction (first direction) M1 with respect to the first seal member.

[0033] In this embodiment, an X-ring 41 is taken as an example of the first seal member, and an O-ring 42 is taken as an example of the second seal member for explanation. That is, the X-ring 41 and the O-ring 42 are attached to the side wall 28b of the base member 28a of the piston portion 28 as seal members for the cylinder 27. Slide rings 43 and 44 are attached to the side wall 28b of the base member 28a of the piston portion 28 for the purpose of suppressing inclination of the piston portion 28 when it slides.

[0034] The X-ring 41 is a ring-shaped elastic member whose cross section is formed in an X-shape as shown in Figures 4 to 7. On the other hand, the O-ring 42 is a ring-shaped elastic member whose cross section is formed in an O-shape as shown in Figure 8.

[0035] In a cross-sectional view of a cut surface parallel to the vertical direction (first direction) M1 shown in Fig. 7, the X ring 41 has a circular base (first base) 41a and lip portions 41b, 41c erected from the circular base 41a and in contact with the cylinder 27 in Fig. 3. That is, the X ring 41 has a cross-sectional shape in which the circular base 41a is disposed in the center of the X-shaped cross section and four lip portions 41b, 41c erected so as to protrude in four directions from the circular base 41a. In detail, the X ring 41 has two lip portions 41b obliquely protruding upward in the vertical direction (first direction) M1 from the circular base 41a and two lip portions 41c obliquely protruding downward in the vertical direction (first direction) M1 from the circular base 41a.

[0036] On the other hand, the O-ring 42 has a circular base (second base) 42a and does not have a lip portion erected from the base 42a in cross section viewed along a cut surface parallel to the up-down direction (first direction) M1 shown in Fig. 8. In other words, the O-ring 42 has only the circular base 42a, and has a cross-sectional shape that does not have a lip portion protruding from the circular base 42a.

[0037] As shown in FIG. 3, an X-ring 41 is attached to groove portion 28c provided on the upper side of side wall 28b of base member 28a of piston portion 28 in the vertical direction (first direction) M1, and an O-ring 42 is attached to groove portion 28d provided on the lower side of side wall 28b in the vertical direction (first direction) M1.

[0038] In other words, the X-ring 41 is attached to the side wall 28b of the base member 28a of the piston portion 28 at a position closer to the pressure chamber 26 (see Figure 1) than the O-ring 42, while the O-ring 42 is attached to a position farther from the pressure chamber 26 than the X-ring 41.

[0039] The contact force of the X-ring 41 against the cylinder 27 is greater than the contact force of the O-ring 42 against the cylinder 27. In other words, the X-ring 41 contacts the cylinder 27 with a greater pressure than the O-ring 42. For example, the interference of the X-ring 41 against the cylinder 27 is greater than the interference of the O-ring 42 against the cylinder 27.

[0040] Here, the tightening of each seal member will be explained. First, the tightening of the O-ring 42 will be explained with reference to FIG. 9. The tightening of the O-ring 42 is expressed as a tightening ratio by the following formula. Tightening ratio = (W1 - H1) / W1 (1). In this case, W1 = the wire diameter of the O-ring 42, and H1 is the height (depth) from the bottom surface 28e of the groove portion 28d. However, for the wire diameter W1 of the O-ring 42, the wire diameter that makes the volume when the inner diameter of the O-ring 42 is expanded (volume after deformation) equal to the volume before the inner diameter of the O-ring 42 is expanded (volume before deformation) is calculated from the following formulas (2) and (3). Volume before deformation: 2 × n 2 ×W 2 (O-ring inner diameter + W) (2), W is the wire diameter of the O-ring 42 before deformation, and the volume after deformation: 2 × n 2 xZ 2 (Piston inner diameter + Z) (3), Z is the wire diameter of the O-ring 42 after deformation.

[0041] From equation (2) = equation (3), the ratio of the wire diameter Z after deformation to the wire diameter W before deformation is calculated, and the wire diameter W1 of the O-ring 42 can be calculated by multiplying the actual wire diameter of the O-ring 42 before deformation by this ratio.

[0042] For example, the actual wire diameter of the O-ring 42 before deformation is 3.5 mm, and the height (depth) H1 of the groove 28d is 3.225 mm. Here, the O-ring inner diameter and the piston inner diameter are predetermined values ​​prepared in advance. In this case, the ratio of the wire diameter Z after deformation to the wire diameter W before deformation is calculated from equation (2) = equation (3), and the actual wire diameter of the O-ring 42 before deformation is multiplied by this ratio to obtain the wire diameter W1 of the O-ring 42 = 3.382. Therefore, the tightening ratio of the O-ring 42 is calculated to be 4.64 from equation (1).

[0043] The tightening ratio of the X-ring 41 can be calculated in the same way as the O-ring 42. For example, the actual wire diameter of the X-ring 41 before deformation is 3.5 mm, and the height (depth) H1 of the groove 28d is 3.225 mm. Here, the X-ring inner diameter and the piston inner diameter are predetermined values ​​prepared in advance. In this case, the ratio of the wire diameter Z after deformation to the wire diameter W before deformation is calculated from equation (2) = equation (3), and the wire diameter W1 of the X-ring 41 is obtained by multiplying the actual wire diameter of the X-ring 41 before deformation by the ratio. Therefore, the tightening ratio of the X-ring 41 is calculated to be 7.57 from equation (1).

[0044] In other words, the tightening rate of the X-ring 41 is greater than the tightening rate of the O-ring 42, and it is found that the tightening rate of the X-ring 41 is greater than the tightening rate of the O-ring 42.

[0045] By making the interference of the X-ring 41 larger than that of the O-ring 42 as described above, the contact force of the X-ring 41 against the cylinder 27 can be made larger than that of the O-ring 42. This makes it possible to make the surface pressure of the seal surface 41d between the X-ring 41 and the cylinder 27, shown in FIG. 3, larger than the surface pressure of the seal surface 42b between the O-ring 42 and the cylinder 27. As a result, the sealing performance of the X-ring 41 at low temperatures can be improved, and air leakage at low temperatures can be suppressed. However, if only the X-ring 41 is installed, there is a concern that the oil film may break at room temperature.

[0046] Therefore, in the nail driver 10 of this embodiment, in addition to the X-ring 41, an O-ring 42 is attached to the piston portion 28.

[0047] The O-ring 42 is attached so that its interference is smaller than that of the X-ring 41. If the interference is small, the surface pressure of the seal surface 42b is smaller than that of the seal surface 41d of the X-ring 41, so that the lubricant can be prevented from being scraped out. The O-ring 42 also acts as a stopper that prevents the lubricant scraped out downward by the X-ring 41 from being scraped out downward beyond the O-ring 42, and holds the lubricant between the X-ring 41 and the O-ring 42. This makes it possible to prevent the occurrence of oil film breakage at room temperature, and the oil film can improve the sealing performance even at room temperature. As a result, the O-ring 42 can prevent air leakage caused by the deterioration of sealing performance due to oil film breakage at room temperature.

[0048] In other words, in the nail gun 10, an X-ring 41, which has a larger tightening margin, and an O-ring 42, which has a smaller tightening margin, are combined and attached to the piston portion 28, so that the X-ring 41 improves sealing performance at low temperatures, while the O-ring 42 suppresses oil film rupture at room temperature, ensuring sealing performance, and thereby the O-ring 42 can suppress air leakage at room temperature.

[0049] The tightening margin of the X-ring 41 in the nail driver 10 of this embodiment is larger than that of the O-ring 42, but is set smaller than that of the X-ring in a conventional nail driver in which the X-ring alone is attached to the piston. That is, in the nail driver 10 of this embodiment, the tightening margins of both the X-ring 41 and the O-ring 42 are set smaller than that of the X-ring in a conventional nail driver.

[0050] Furthermore, the X-ring 41 is preferably made of a material having higher mechanical strength and wear resistance than the O-ring 42. Examples of materials for forming the X-ring 41 include hydrogenated nitrile rubber (HNBR). Hydrogenated nitrile rubber has both high pressure resistance and high mechanical strength, and is an appropriate material for high-pressure parts and sliding parts that require wear resistance. By making the X-ring 41 of a material having higher mechanical strength and wear resistance than the O-ring 42, the strength of the X-ring 41 can be ensured, and the sealing performance at normal temperature and low temperature can be improved for a long period of time.

[0051] On the other hand, the O-ring 42 is preferably made of a material having higher cold resistance than the X-ring 41. Examples of materials for forming the O-ring 42 include ethylene-propylene rubber (EPDM). Ethylene-propylene rubber is a material that can maintain its strength even at low temperatures because of its low brittle temperature. By making the O-ring 42 of a material having higher cold resistance than the X-ring 41, the sealing performance at low temperatures can be further improved. The material for forming the O-ring 42 may be nitrile rubber (NBR). Nitrile rubber generally has a property of being less cold resistant than ethylene-propylene rubber, but the cold resistance can be sufficiently improved by adjusting the compounding ratio of the materials constituting the nitrile rubber and increasing the hardness.

[0052] Here, the shape of the X-ring 41 will be described in detail. As shown in FIG. 7, the X-ring 41 includes a circular base (first base) 41a and four lip portions 41b, 41c protruding from the circular base 41a in a cross-sectional view. The protruding direction G1 of the two lip portions 41b protruding upward from the base 41a among the four lip portions 41b, 41c is a direction inclined with respect to the radial direction J1 so that the outer side of the lip portion 41b in the radial direction J1 of the cylinder 27 (see FIG. 1) faces the upper (other) side of the vertical direction (first direction) M1. That is, the protruding directions G1 of the two lip portions 41b from the base 41a are different from each other and obliquely upward. Similarly, the protruding directions of the two lip portions 41c from the base 41a are different from each other and obliquely downward.

[0053] In addition, in a cross-sectional view of the X-ring 41, the thickness T1 of the lip portion 41b in the orthogonal direction K1 perpendicular to the protruding direction G1 in which the lip portion 41b protrudes from the base portion 41a is smaller than the minor axis P1 of the base portion 41a. As an example, T1=0.972 mm, and P1=2.8 mm. Furthermore, in a cross-sectional view of the X-ring 41, the length L1 of the lip portion 41b in the protruding direction G1 in which the lip portion 41b protrudes from the base portion 41a is equal to the thickness T1 of the lip portion 41b in the orthogonal direction K1 perpendicular to the protruding direction G1. Specifically, the length L1 of the lip portion 41b is within a range of plus or minus 20% of the thickness T1 of the lip portion 41b or more. As an example, L1=0.872 mm.

[0054] Next, the arrangement of the X-ring 41 and the O-ring 42 in the vertical direction (first direction) M1 will be described. As shown in FIG. 3, the X-ring 41 is attached to the groove 28c above the O-ring 42 in the vertical direction (first direction) M1, while the O-ring 42 is attached to the groove 28d below the X-ring 41 in the vertical direction (first direction) M1. Here, as shown in FIG. 1, in the nail driver 10, the pressure chamber 26 is provided above the cylinder 27. Therefore, the X-ring 41 is attached to the piston portion 28 at a position closer to the pressure chamber 26 than the O-ring 42, while the O-ring 42 is attached to a position farther from the pressure chamber 26 than the X-ring 41. Then, the piston portion 28 is pushed down by the pressure of the air from the pressure chamber 26. At this time, a large pressure of the air from the pressure chamber 26 is applied to the seal member arranged on the upper side of the piston portion 28.

[0055] Therefore, in the nail driver 10 of this embodiment, an X-ring 41 is disposed on the side wall 28b of the base member 28a of the piston portion 28 on the side closer to the pressure chamber 26 (top dead center side), and an O-ring 42 is disposed on the side farther from the pressure chamber 26 (bottom dead center side). By disposing the X-ring 41 on the top dead center side, it is possible to ensure the sealing performance of the piston portion 28 even against the large pressure of the air from the pressure chamber 26.

[0056] That is, the X-ring 41 is provided with two lip portions 41b each protruding obliquely upward as shown in FIG. 7, and these two lip portions 41b abut against the inner wall 27a of the cylinder 27 to mainly ensure sealing. At that time, when the air pressure from the pressure chamber 26 is applied to the X-ring 41 from above, the air enters the upper side of the X-ring 41, and the X-ring 41 is crushed downward. At this time, the X-ring 41 is deformed so that the tip side of the lip portion 41b protruding obliquely upward is pushed outward. That is, the two lip portions 41b are deformed so as to abut more strongly against the inner wall 27a of the cylinder 27. As a result, the surface pressure of the X-ring 41 against the inner wall 27a of the cylinder 27 becomes higher, and the sealing property by the X-ring 41 can be further improved. That is, by arranging the X-ring 41 on the top dead center side, the surface pressure of the X-ring 41 against the cylinder 27 is further increased, and the sealing property of the piston portion 28 can be further improved.

[0057] In addition, since the X-ring 41 originally has a larger interference than the O-ring 42 to increase the surface pressure, the increased surface pressure can improve the sealing performance, especially at low temperatures. As a result, air leakage can be suppressed even at low temperatures. As described above, by locating the X-ring 41 on the top dead center side, the surface pressure can be increased, and the sealing performance at low temperatures can be improved.

[0058] On the other hand, in that case, there is a concern that the oil film of the lubricant may break at normal temperature. However, in the nail driver 10 of this embodiment, the O-ring 42 is arranged on the bottom dead center side. On the bottom dead center side, the surface pressure does not increase due to the large pressure of the air from the pressure chamber 26, unlike the above-mentioned X-ring 41. Furthermore, the O-ring 42 has a smaller tightening margin than the X-ring 41, so the surface pressure of the O-ring 42 is originally small. As a result, the oil film is less likely to break on the O-ring 42. Furthermore, since the O-ring 42 is circular in shape and does not have a lip portion, the contact surface with the cylinder 27 is small, and the oil film is less likely to break compared to the X-ring 41. That is, the O-ring 42 arranged on the bottom dead center side is less likely to break the oil film. Furthermore, the O-ring 42 acts as a stopper that prevents the lubricant scraped out downward by the X-ring 41 from being scraped out downward beyond the O-ring 42, and holds the lubricant between the X-ring 41 and the O-ring 42. As a result, oil film breakdown at room temperature can be reduced and the sealing performance provided by the lubricant (oil film) can be ensured.

[0059] As described above, in the nail driver 10 of the present embodiment, by arranging a sealing member (X-ring 41) that has a high surface pressure at low temperatures and a sealing member (O-ring 42) that has a low surface pressure at normal temperatures, it is possible to ensure sealing while suppressing oil film rupture. This makes it possible to suppress air leakage, and to reduce the frequency with which an operator needs to stop driving work to refill air. In other words, air leakage from the nail driver 10 is suppressed, allowing the nail driver 10 to be used for a long period of time. As a result, the convenience of the nail driver 10 can be improved.

[0060] Next, modified examples of this embodiment will be described. In the first modified example shown in Fig. 10, a V-ring 48 is used as the first seal member instead of the X-ring 41 on the top dead center side of the side wall 28b of the base member 28a of the piston portion 28, and an O-ring 42 is attached on the bottom dead center side.

[0061] As shown in Fig. 11, in a cross-sectional view, the V-ring 48 includes a circular base (first base) 48a disposed in the center of the V-shaped cross section, and two lip portions 48b protruding in two directions from the circular base 48a. The two lip portions 48b protrude upward. Specifically, the protruding direction G1 of the two lip portions 48b from the base 48a is a direction inclined with respect to the radial direction J1 such that the outer side of the lip portion 48b in the radial direction J1 of the cylinder 27 (see Fig. 1) faces the upper (other) side of the vertical direction (first direction) M1. That is, the protruding directions G1 of the two lip portions 48b from the base 48a are different obliquely upward.

[0062] In addition, in a cross-sectional view of the V ring 48, the thickness T1 of the lip portion 48b in the orthogonal direction K1 perpendicular to the protruding direction G1 in which the lip portion 48b protrudes from the base portion 48a is smaller than the minor axis P1 of the base portion 48a. In addition, in a cross-sectional view of the V ring 48, the length L1 of the lip portion 48b in the protruding direction G1 in which the lip portion 48b protrudes from the base portion 48a is equal to the thickness T1 of the lip portion 48b in the orthogonal direction K1 perpendicular to the protruding direction G1. Specifically, the length L1 of the lip portion 48b is within the range of plus or minus 20% of the thickness T1 of the lip portion 48b or more.

[0063] As shown in FIG. 10, the V-ring 48 is disposed on the top dead center side of the piston portion 28 to form a seal surface 48c at the contact point with the inner wall 27a of the cylinder 27, so that the surface pressure can be increased, and as a result, the sealing performance at low temperatures can be improved. Furthermore, the O-ring 42 is disposed on the bottom dead center side of the piston portion 28, so that the oil film breakage at normal temperatures can be reduced and the sealing performance by the lubricant (oil film) can be ensured. In other words, by disposing a seal member (O-ring 42) that minimizes the surface pressure at normal temperatures, the oil film breakage can be suppressed and the sealing performance can be ensured. This makes it possible to suppress the occurrence of air leakage, and reduces the frequency with which the worker interrupts the driving operation to refill air. In other words, the air leakage of the nail driver 10 can be suppressed, and the nail driver 10 can be used for a long period of time. As a result, even if the V-ring 48 is adopted instead of the X-ring 41, the convenience of the nail driver 10 can be improved.

[0064] 12, an X-ring 41 is disposed as a first seal member on the top dead center side of the side wall 28b of the base member 28a of the piston portion 28, and a D-ring 49 is used as a second seal member on the bottom dead center side instead of the O-ring 42. By disposing the X-ring 41 on the top dead center side of the piston portion 28, the surface pressure on the top dead center side can be increased, thereby improving the sealing performance at low temperatures. Furthermore, by disposing the D-ring 49 on the bottom dead center side of the piston portion 28, it is possible to reduce oil film breakdown at room temperature and ensure the sealing performance by the lubricant (oil film), similar to the case of the O-ring 42.

[0065] The D-ring 49, like the O-ring 42, has only a circular base (second base) 49a and does not have a lip. Therefore, the surface pressure can be reduced at room temperature on the seal surface 49b of the D-ring 49 at the contact point with the cylinder 27, and the oil film of the lubricant can be prevented from running out. In other words, by arranging the X-ring 41 on the top dead center side and the D-ring 49 on the bottom dead center side, the oil film can be prevented from running out and the sealability can be ensured. This can prevent air leakage, and the frequency with which the worker stops the driving operation to refill the air can be reduced. In other words, the air leakage of the nail driver 10 can be prevented, and the nail driver 10 can be used for a long period of time. As a result, the convenience of the nail driver 10 can be improved even when the D-ring 49 is used instead of the O-ring 42.

[0066] The present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the present invention. For example, in the above embodiment, the second seal member is described as a seal member having a circular or D-shaped cross section, but the second seal member may have a rectangular or elliptical cross section. The positions of the X-ring 41 and the O-ring 42 may be reversed from those in the above embodiment, and the O-ring 42 may be disposed closer to the top dead center than the X-ring 41. In this case, the effect of increasing the sealing performance of the X-ring 41 by the air pressure from the pressure chamber 26 is reduced compared to the above embodiment, but the effect of holding the lubricant between the X-ring 41 and the O-ring 42 remains unchanged, and air leakage caused by oil film breakdown can be reduced. In this case, too, the tightening margin of the X-ring 41 can be increased compared to the above embodiment, thereby improving the sealing performance of the X-ring 41 and suppressing air leakage at low temperatures. [Explanation of symbols]

[0067] 10... nail gun (working machine), 11... housing, 12... striking part, 13... nose part, 14... power supply part, 15... electric motor, 17... winding mechanism, 18... pressure accumulator, 19... cylinder case, 20... handle, 21... motor case, 22... mounting part, 23... cap, 24... holder, 25... head cover, 26... pressure chamber, 27... cylinder, 27a... inner wall, 28... piston part, 28a... base member, 28b... side wall, 2 8c, 28d...groove portion, 28e...bottom surface, 29...driver blade, 29a...rack, 30...mate material, 31...bumper support portion, 31a...guide hole, 32...ejection portion, 33...tubular portion, 35...bumper, 36...guide hole, 37...ejection path, 38...bearing, 39...rotor, 40...stator, 41...X-ring (first seal member), 41a...base (first base), 41b, 41c...lip portion, 41d...seal surface, 42...O-ring (second seal member), 2 seal member), 42a...base (second base), 42b...seal surface, 43, 44...slide ring, 45...reduction mechanism, 46...rotating shaft, 47...motor shaft, 48...V ring (first seal member), 48a...base (first base), 48b...lip portion, 48c...seal surface, 49...D ring (second seal member), 49a...base (second base), 49b...seal surface, 50...pinwheel, 50a...pin, 71...trigger switch Chi, 72...position detection switch, 73...control section, 75...trigger, 76...storage case, 77...magazine, 78...nail (fastener), 79...push lever, A1, A2...center line, D1...driving direction, D2...return direction, E1...rotation direction, G1...projection direction, H1...height, J1...radial direction, K1...orthogonal direction, L1...length, M1...up-down direction (first direction), N1...front-back direction, P1...minor diameter, R1...left-right direction, T1...thickness, W1...wire diameter

Claims

1. A hollow case portion including a cylinder having a cylindrical shape extending in a first direction and an inner wall; a piston portion that is movable in the first direction inside the cylinder, cooperates with the case portion to define a pressure chamber inside the case portion, and moves to one side in the first direction due to the pressure of gas inside the pressure chamber to strike a stopper, the piston portion includes a base member having a side wall facing the inner wall of the cylinder, a first seal member attached to the base member so as to be interposed between the side wall and the inner wall, and a second seal member attached to the base member so as to be interposed between the side wall and the inner wall and disposed at a different position in the first direction with respect to the first seal member, The first seal member has a first base portion and a lip portion extending from the first base portion and contacting the cylinder in a cross-sectional view of a cut surface parallel to the first direction, The second seal member, in the cross-sectional view, has a second base portion and does not have a lip portion standing upright from the second base portion.

2. The work machine according to claim 1 , wherein a contact force of the first seal member against the cylinder is greater than a contact force of the second seal member against the cylinder.

3. 3. The work machine according to claim 2, wherein an interference between the first seal member and the cylinder is greater than an interference between the second seal member and the cylinder.

4. The work machine according to claim 1 , wherein the first seal member is disposed on the other side in the first direction than the second seal member.

5. The work machine according to claim 1 , wherein the first seal member is made of a material having a higher mechanical strength than the second seal member.

6. The work machine according to claim 1 , wherein the second seal member is made of a material having higher cold resistance than the first seal member.

7. 2. The work machine according to claim 1, wherein, in the cross-sectional view of the first seal member, a protruding direction in which the lip portion of the first seal member protrudes from the first base portion is inclined with respect to the radial direction so that an outer side in the radial direction of the cylinder faces the other side in the first direction.

8. The work machine according to claim 1, wherein in the cross-sectional view of the first seal member, a thickness of the lip portion in a direction perpendicular to a protruding direction in which the lip portion of the first seal member protrudes from the first base is smaller than a minor axis of the first base.

9. 2. The work machine according to claim 1, wherein, in the cross-sectional view of the first seal member, a length of the lip portion of the first seal member in a protruding direction in which the lip portion protrudes from the first base is equal to a thickness of the lip portion in a perpendicular direction perpendicular to the protruding direction.

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