Patent Application
20180345469
The present invention relates to a reciprocating work machine having a striking mechanism that reciprocates.
A reciprocating work machine having a striking mechanism that reciprocates is described in Patent Document 1. The reciprocating work machine according to Patent Document 1 includes a housing accommodating a motor, a motion conversion mechanism converting a rotational force of the motor into a reciprocating force, a handle connected to the housing, a cylinder provided inside the housing, a piston reciprocating inside the cylinder, a striker movably disposed inside the cylinder, an air chamber formed between the striker and the piston inside the cylinder, and an intermediate element supported by the housing and transmitting a striking force of the striker to a tool.
A first end portion of the handle is connected to the housing via elastic means, and a second end portion of the handle is rotatably connected to the housing via a supporting shaft. In the reciprocating work machine according to Patent Document 1, the piston reciprocates, and the striker strikes the tool. Due to a reaction force upon striking, the housing vibrates in a reciprocating direction of the piston. The elastic means reduces vibration transmitted from the housing to the handle.
Patent Document 1: Japanese Patent No. 4626574
The reciprocating work machine according to Patent Document 1 is not capable of sufficiently reducing the vibration transmitted from the housing to the handle, and a further reduction of the vibration of the handle has been desired.
It is an object of the present invention to provide a reciprocating work machine with good workability by further reducing vibration of a handle.
A reciprocating work machine according to one embodiment is provided with a motor, a striking mechanism reciprocating by power of the motor and striking a tool, and a housing accommodating the motor and the striking mechanism, and the reciprocating work machine includes a resin handle operably connected to the housing, an elastic body provided between the housing and the handle and expanding and contracting in a reciprocating direction of the striking mechanism when the handle is operated relative to the housing, and a weight provided to the handle and made of a material having a specific gravity higher than each of a specific gravity of a material constituting the handle and a specific gravity of a material constituting the housing.
According to the reciprocating work machine, vibration of the handle can be more reduced, and workability is improved.
Hereinafter, embodiments of the reciprocating work machine will be described with reference to the drawings.
A reciprocating work machine 10 illustrated in
The reciprocating work machine 10 includes a housing 12, and the housing 12 is configured such that a striking case 13, a motor case 14, and a gear case 15 are fixed together with a screw member 16. Also, a handle 50 is connected to the housing 12. The striking case 13 is cylindrical as in
A holder 21 is provided outside the striking case 13, and the holder 21 is fixed to a first end portion of the striking case 13 in the direction of the axis line A1 with a screw member 22. The holder 21 is cylindrical, and the holder 21 includes a supporting hole 23. The holder 21 supports the tool 11 inserted into the supporting hole 23. A second hammer 24 is disposed from the supporting hole 23 to the inside of the striking case 13. The second hammer 24 is movable in the direction of the axis line A1. The second hammer 24 is cylindrical, and the second hammer 24 has a large-diameter portion 25. An annular stopper 26 is provided inside the supporting hole 23, and an annular stopper 27 is provided inside the striking case 13. The large-diameter portion 25 comes into contact with the stopper 26 or the stopper 27, and accordingly, a moving range of the second hammer 24 in the direction of the axis line A1 is restricted.
A piston 28 is disposed inside the cylindrical portion 19 of the striker 17. The piston 28 is movable relative to the striker 17 in the direction of the axis line A1. Inside the cylindrical portion 19, an air damper chamber 29 is formed between the bottom portion 20 and the piston 28. An annular sealing member 30 is attached to an outer peripheral surface of the piston 28. The sealing member 30 is made of synthetic rubber, and the sealing member 30 is in contact with an inner peripheral surface of the cylindrical portion to form a sealing surface. The sealing member 30 seals the air damper chamber 29. A grip 31 is fixed to the striking case 13 with a fastening element 32. The fastening element 32 includes a bolt and a nut. The grip 31 is disposed outside the striking case 13, and an operator can grasp the grip 31.
As in
The two bearings 38 and 39 support the rotational shaft 36 so as to be rotatable about an axis line A2. In a front view of the reciprocating work machine 10, the axis line A1 is orthogonal to the axis line A2. A driving gear 40 is provided on an outer peripheral surface of the rotational shaft 36. The driving gear 40 is disposed inside the gear case 15. An intermediate gear 41 is disposed inside the gear case 15. The gear case 15 supports a bearing 42, and the partition wall 37 supports a bearing 43. The two bearings 42 and 43 rotatably support the intermediate gear 41. The intermediate gear 41 meshes with the driving gear 40.
A crank shaft 44 is disposed from the inside of the gear case 15 to the inside of the motor case 14. A driven gear 45 is fixed to the crank shaft 44. The gear case 15 supports a bearing 46, and the partition wall 37 supports a bearing 47. The two bearings 46 and 47 rotatably support the crank shaft 44. The driven gear 45 meshes with the intermediate gear 41.
The crank shaft 44 includes a crank pin 48, and the crank pin 48 is at a position eccentric to the crank shaft 44 in a radial direction. A connecting rod 49 is disposed from the inside of the motor case 14 to the inside of the striking case 13, and the connecting rod 49 is coupled to the crank pin 48 and the piston 28. When the crank shaft 44 is rotated, the connecting rod 49 converts a rotational force of the crank shaft 44 into a reciprocating motion force of the piston 28.
As in
As in
To the handle 50, an end portion of a power supply code 56 is attached, and a trigger 57 and a trigger switch 58 are provided to the gripping portion 51. A lead wire 59 is provided inside the gripping portion 51 and the second end portion 53, and the lead wire 59 is connected to the trigger switch 58 and the electric motor 33. The power supply code 56 is connected to a power supply, for example, a direct-current (DC) power supply or an alternating-current (AC) power supply.
A weight 61 is provided to the first end portion 52. The weight 61 is made of a metal material. As in
A guide portion 68 is provided to the gear case 15. The guide portion 68 is fixed to the gear case 15 with a screw member 69. The guide portion 68 is made of a metal material. The guide portion 68 has a base portion 70, and a pair of leg portions 71 continuous to the base portion 70. The pair of leg portions 71 is disposed along the direction of the axis line A1. In the plan view of the reciprocating work machine 10, the pair of leg portions 71 is disposed across the axis line A1 and parallel to each other as in
In the plan view of the reciprocating work machine 10, the weight 61 is disposed between the pair of leg portions 71 in the direction orthogonal to the axis line A1. An arrangement region of the protruding portion 65 overlaps with an arrangement region of the pair of leg portions 71. There is provided an engagement portion 72 protruding from the pair of leg portions 71. A direction in which the engagement portion 72 protrudes from the pair of leg portions 71 is an opposite direction of a part where the electric motor 33 is disposed. The protruding portion 65 is disposed between the engagement portion 72 and the base portion 70 in the direction of the axis line A1. When the handle 50 rotates clockwise about the supporting shaft 55 in
As in
Springs 74 and 78 are disposed between the gear case 15 and the first end portion 52. The springs 74 and 78 are metal coil springs that generate a repulsive force by receiving a compressive load. A spring constant of the spring 74 is larger than a spring constant of the spring 78. An outer diameter of the spring 78 is smaller than an inner diameter of the spring 74, and the spring 78 is disposed inside the spring 74. The gear case 15 has a supporting portion 75. The supporting portion 75 protrudes from a wall 15A of the gear case 15. The springs 74 and 78 are disposed in the recessed portion 64 and are supported by the supporting portion 75. That is, the weight 61 supports an end portion of each of the springs 74 and 78 in an expansion and contraction direction. The springs 74 and 78 are sandwiched by the gear case 15 and the base portion 62, and the springs 74 and 78 constantly receive the compressive load in the direction of the axis line A1.
The reciprocating work machine 10 includes a control unit 76 illustrated in
A material, a mass, and a specific gravity of an element constituting the reciprocating work machine 10 may be as follows, for example. The striking case 13, the motor case 14, and the gear case 15 constituting the housing 12 are each made of a metal material such as a casting aluminum alloy. Further, the holder 21 is made of a metal material such as a material harder than the casting aluminum alloy. Each specific gravity of the casting aluminum alloy constituting the housing 12 and the material constituting the holder 21 is 2.68 [g/ĉ3].
The handle 50 is made of a synthetic resin such as a polyamide resin. The polyamide resin includes nylon (trade name of INVISTA K.K.). A specific example of the handle 50 is as follows. Each of the constituent pieces 50A and 50B is 200 g in mass, and the handle 50 is 400 g in mass. A specific gravity of the polyamide resin constituting the handle 50 is 1.2 [g/ĉ3].
As the metal material constituting the weight 61, common steel or carbon steel for machine structural use, for example, is used. The weight 61 is 250 g in mass. A specific gravity of the metal material constituting the weight 61 is 7.86 [g/cm̂3].
As the metal material constituting the guide portion 68, special steel, alloy steel for machine structural use, or tool steel, for example, is used. The guide portion 68 may be 66 g in mass. A specific gravity of the metal material constituting the guide portion 68 is 7.85 [g/cm̂3].
An example of use of the reciprocating work machine 10 will be described. The operator, for example, grips the grip 31 with the left hand, grips the gripping portion 51 of the handle 50 with the right hand, and presses the tool 11 against an object. Then, the large-diameter portion 25 comes in contact with the stopper 27, and the second hammer 24 stops. Then, when the operator operates the trigger 57 to turn the trigger switch 58 on, the control unit 76 supplies the electric motor 33 with electric power, and the rotational shaft 36 is rotated. The control unit 76 controls an actual rotational speed of the rotational shaft 36 based on the target rotational speed set by the rotational speed setting unit 77.
A rotational force of the rotational shaft 36 is transmitted to the crank shaft 44 through the intermediate gear 41 and the driven gear 45, and the crank shaft 44 is rotated. When the crank shaft 44 rotates, the piston 28 reciprocates in the direction of the axis line A1, and the striker 17 strikes the second hammer 24. The piston 28 and the striker 17 constitute a striking mechanism that reciprocates by power of the electric motor 33. A striking force received by the second hammer 24 is transmitted to the tool 11, and the object is crushed. When the trigger 57 is operated to turn the trigger switch 58 off, the control unit 76 stops the electric motor 33.
During striking operation, the piston 28 and the connecting rod 49 operate in the direction of the axis line A1 while a reaction force of the striking force applied to the tool 11 is transmitted to the connecting rod 49 through the striker 17 and the piston 28, and its load is transmitted to the housing 12 through the crank shaft 44 and the bearings 46 and 47. When the housing 12 vibrates in the direction of the axis line A1, the handle 50 rotates about the supporting shaft 55 relative to the housing 12, and the springs 74 and 78 expand and contract. The springs 74 and 78 reduce vibration transmitted from the housing 12 to the handle 50. Thus, workability in using the reciprocating work machine 10 improves.
Furthermore, when the handle 50 rotates about the supporting shaft 55 relative to the housing 12, the pair of leg portions 71 slides on the outer surfaces 66A and 66B of the pair of arm portions 63. That is, the weight 61 partially reduces a part of kinetic energy transmitted from the housing 12 to the handle 50 by frictional resistance to suppress vibration of the handle 50. Furthermore, the guide portion 68 and the weight 61 restrict moving of the handle 50 in the direction of the center line D1 relative to the housing 12 and function as guides when the handle 50 moves in the direction of the axis line A1.
Further, the weight 61 is attached to the handle 50, and a natural frequency of the handle 50 to which the weight 61 is fixed is smaller than a natural frequency of the handle 50 alone. Thus, it is possible to further reduce the vibration transmitted from the housing 12 to the handle 50.
Further, the weight 61 and the springs 74 and 78 have arrangement regions in the direction of the axis line A1 that are overlapped with each other, arrangement regions in the direction of the center line D1 that are overlapped with each other, and arrangement regions in the direction of the center line B1 that are overlapped with each other. Thus, it is not necessary to provide a dedicated arrangement space for the weight 61, and it is possible to suppress an increase in size of the reciprocating work machine 10.
In the reciprocating work machine 10 according to the embodiment, the weight 61 is made of a steel material of 250 g in mass, and when the number of strikes per second corresponding to the maximum rotational speed of the electric motor 33 is 23.3 times, the vibration transmission rate is less than 68%.
In the reciprocating work machine 10 according to the embodiment, the number of strikes per second corresponding to the maximum rotational speed of the electric motor 33 can be set to 15.7 to 27.5 times, 16.6 times, 16.7 to 36.6 times, 20 to 41.7 times, 23.3 times, 30 times, 50 times, and the like according to each use or size. As the maximum rotational speed of the electric motor 33 increases, the number of strikes per second increases.
Note that the vibration transmission rate of the reciprocating work machine according to the second comparative example without a weight is 100% or more. It is apparent that the vibration transmission rate of the reciprocating work machine 10 according to the embodiment is smaller than the vibration transmission rate of the reciprocating work machine according to the second comparative example without a weight.
When vibration from the housing 12, a load of pressing the handle 50 against a side of the housing 12, and the like are transmitted to the springs 74 and 78, the springs 74 and 78 come into contact with each other while expanding and contracting and cause friction with the supporting portion 75 and the weight 61, and as a result, an abnormal noise may be generated. In particular, since the spring 78 has a spring constant smaller than that of the spring 74, vibration that causes the abnormal noise is likely to be sustained by being coincident with the natural frequency of the spring 78. In addition, since the spring 78 is not provided with a member for damping vibration such as the damper 73 which comes in contact with the spring 74, on a sandwiching surface thereof, the vibration that causes the abnormal noise is hardly damped. Accordingly, the spring 78 may continue to make the abnormal noise for a long period of time after completion of work and after pressing operation of the handle 50, and when an operator hears this abnormal noise, the noise may be offensive to his/her ears, and there might be a possibility of causing misunderstanding of any failure. Thus, the abnormal noise is not preferred.
Two dampers 80 are accommodated inside the spring 78, which is a cylindrical coil spring. An internal space 83 is formed by an inner peripheral surface of the spring 78, a rear end surface 75a in a range of being located inside in a radial direction of the spring 78 at the supporting portion 75, and a front end surface 61a in a range of being located inside in the radial direction of the spring 78 at the weight 61, and the dampers 80 are accommodated inside this internal space 83.
Each of the dampers 80 has a substantially cylindrical shape, and an end surface 81 on either side has a chamfered portion 82 where an edge portion is chamfered.
Since the damper 80 is configured so as to be accommodated inside the spring 78, a structure in which the damper 80 and the spring 78 come in contact with each other can be easily achieved without making any special devise to the shape of the damper 80. Since the damper 80 is configured so as to have the outer diameter smaller than the inner diameter of the spring 78 and to be freely movable inside the spring 78, the damper 80 is prevented from closely adhering to the spring 78 and hindering expansion and contraction of the spring 78. Since the damper 80 is configured so as to have the shape in which the edge portion of the end surface on either side of the cylinder is chamfered, it is possible to prevent the damper 80 from being caught by the spring 78 upon expansion and contraction and hindering the expansion and contraction as well as to prevent the damper 80 from wearing early. Note that, in addition to the above-described configuration, it is also possible to suppress the occurrence of the abnormal noise even in another structure allowing the damper 80 to come into contact with the spring 78, for example, in a structure in which the damper 80 is provided between the spring 78 and the spring 74 and is formed into a cylindrical shape covering an outer periphery of the spring 78.
As a mass of the damper 80 is increased and a load at which the dampers 80 come in contact with the spring 78 is increased, an effect of suppressing the vibration of the spring 78 by the damper 80 is increased. Meanwhile, in a case where the outer diameter of the damper 80 is increased in order to increase the mass of the dampers 80, an inner periphery of the spring 78 slides on an outer periphery of the dampers 80, which may hinder the expansion and contraction of the spring 78. Further, in a case where a length L in an axial direction of the damper 80 is increased, the spring 78 may come in contact with the damper 80 when it is bent while expanding and contracting, which may hinder the expansion and contraction thereof. In the configurations illustrated in
Note that, in order to achieve an effect of effectively suppressing the vibration of the spring 78, an effect of preventing the spring 80 from wearing due to contact between the damper 80 and the spring 80 by forming the damper 80 of a material having lower hardness than that of the spring 78, and an effect of suppressing generation of the abnormal noise when the damper 80 and the spring 78 come in contact with each other, it is most appropriate that the damper 80 is made of an elastic body such as rubber. However, by forming the damper 80 of a resin and the like having lower hardness than that of the spring 78 other than rubber, it is possible to achieve suppression of the abnormal noise and prevention of wearing of the spring 78.
The electric motor 33 described in the embodiment corresponds to the motor, the piston 28 and the striker 17 correspond to the striking mechanism, the springs 74 and 78 correspond to the elastic body, the outer surface 66A corresponds to a first side surface, the outer surface 66B corresponds to a second side surface, the damper 80 corresponds to a resin member, the supporting portion 75 corresponds to a spring supporting portion, the direction of the axis line A1 corresponds to the reciprocating direction, and the direction of the center line B1 corresponds to a predetermined direction. The direction of the center line B1 crosses the direction of the axis line A1.
The reciprocating work machine is not to be limited to the embodiment, and various modifications are possible within the range not deviating from the gist thereof. For example, a metal spring used as the elastic body may also be not only a coil spring, but also a torsion spring and a leaf spring. As the elastic body, it is also possible to use synthetic rubber in place of the metal spring. The power supply that supplies the electric motor with electric power includes an AC power supply and a DC power supply. The DC power supply includes a battery attached to and detached from the handle.
A conversion mechanism for converting a rotational force of the motor into a reciprocating force of the piston includes not only a crank mechanism, but also a cam mechanism. The motor includes not only an electric motor, but also a hydraulic motor, a pneumatic motor, and an internal combustion engine. A resin constituting the handle may also be not only the polyamide resin, but also a urethane resin and a polyethylene resin. The housing is a hollow container accommodating the striking mechanism, and it does not matter whether the inside is hermetically sealed or not.
When the handle of the reciprocating work machine is operable relative to the housing, it means that the handle is relatively movable. Accordingly, the reciprocating work machine may be the one with the handle rotatable about the supporting shaft relative to the housing or the one with the handle slidable via a rail member relative to the housing. In this case, the handle slides in the reciprocating direction of the striking mechanism relative to the housing.
10 . . . reciprocating work machine, 11 . . . tool, 12 . . . housing, 13 . . . striking case, 14 . . . motor case, 15 . . . gear case, 15A . . . wall, 16, 22, 60, 67, 69, 79 . . . screw member, 17 . . . striker, 18 . . . guide portion, 19 . . . cylindrical portion, 20 . . . bottom portion, 21 . . . holder, 23 . . . supporting hole, 24 . . . second hammer, 25 . . . large-diameter portion, 26, 27 . . . stopper, 28 . . . piston, 29 . . . air damper chamber, 30 . . . sealing member, 31 . . . grip, 32 . . . fastening element, 33 . . . electric motor, 34 . . . stator, 35 . . . rotor, 36 . . . rotational shaft, 37 . . . partition wall, 38, 39, 42, 43, 46, 47 . . . bearing, 40 . . . driving gear, 41 . . . intermediate gear, 44 . . . crank shaft, 45 . . . driven gear, 48 . . . crank pin, 49 . . . connecting rod, 50 . . . handle, 50A, 50B . . . constituent piece, 51 . . . gripping portion, 52 . . . first end portion, 53 . . . second end portion, 54 . . . mount, 55 . . . supporting shaft, 56 . . . power supply code, 57 . . . trigger, 58 . . . trigger switch, 59 . . . lead wire, 61 . . . weight, 61a . . . front end surface, 62, 70 . . . base portion, 63 . . . arm portion, 64 . . . recessed portion, 65 . . . protruding portion, 66A, 66B . . . outer surface, 68 . . . guide portion, 71 . . . leg portion, 72 . . . engagement portion, 73 . . . damper, 74, 78 . . . spring, 75 . . . supporting portion, 75a . . . rear end surface, 76 . . . control unit, 77 . . . rotational speed setting unit, 80 . . . damper, 81 . . . end surface, 82 . . . chamfered portion, 83 . . . internal space, A1, A2 . . . axis line, B1, D1 . . . center line, C1, C2 . . . straight line.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-230281 | Nov 2015 | JP | national |
| 2016-168064 | Aug 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/082059 | 10/28/2016 | WO | 00 |
