The present application claims priority from Japanese Patent Application No. 2012-070602 filed on Mar. 27, 2012, the content of which is hereby incorporated by reference into this application.
The present invention relates to a power tool in which a tip tool is driven by a driving source, such as an electric motor, a pneumatic pressure motor, or the like.
As one example of the power tool in which a tip tool is driven by a driving source, such as an electric motor, a pneumatic pressure motor, or the like, an impact driver, an impact wrench or the like has been known. A driver bit and a socket serving as tip tools are attached to the impact driver and the impact wrench. The tip tool to be attached to the impact driver and the impact wrench is driven to rotate and an impact force (impact) is applied thereto.
The above-mentioned power tool is provided with a driving source, a reducer mechanism for decelerating the rotation of the driving source, a transmission mechanism that transmits the output of the reducer mechanism to the tip tool, and a housing that houses these members. The housing is provided with a handle unit to be grabbed by a worker, and a body unit that is integrally molded with one end of the handle unit. The driving source, the reducer mechanism and the transmission mechanism are housed in the body unit. More specifically, the driving source is housed on one end side of an internal space of the body unit, and the reducer mechanism and the transmission mechanism are housed in a case that is housed on the other end side of the internal space of the body unit.
In the power tool having the above-described structure, air inside the case is expanded due to heat generated during operations of the reducer mechanism and the transmission mechanism, resulting in an increase of the internal pressure. In such a situation, grease which is shielded inside the case for lubricating the reducer mechanism and the transmission mechanism sometimes leaks from the case.
For this reason, Japanese Patent Application Laid-Open Publication No. 2008-62342 (Patent Document 1) describes an electric tool in which an air release passage having a labyrinth shape is formed between the case and the housing so that the internal space of the case is allowed to communicate with the air through the air release passage.
Japanese Patent Application Laid-Open Publication No. 2011-131358 (Patent Document 2) describes a hammer drill in which a pressure adjusting mechanism for preventing the grease leakage is installed in a gear housing.
Japanese Patent Application Laid-Open No. 2009-178803 (Patent Document 3) describes an impact tool in which a through hole is formed in a hammer case so as to prevent the grease leakage.
Since the air release passage described in Patent Document 1 has the labyrinth shape, its flow resistance is high. The pressure adjusting mechanism described in Patent Document 2 largely jetties toward the inside of a gear housing. Therefore, when this pressure adjusting mechanism is adopted in a power tool provided with a planetary gear mechanism, the overall length of the power tool is required to be made longer so as to avoid interference between the planetary gear and the pressure adjusting mechanism. As described in Patent Document 3, when a through hole is formed in a hammer case, the strength of the hammer case is lowered, resulting in degradation of the durability of the power tool.
A preferred aim of the present invention is to effectively suppress a pressure increase inside a case in which a reducer mechanism and a transmission mechanism are housed, without causing an increase in size and degradation in durability of a power tool.
In one aspect of the present invention, a power tool is provided with a reducer mechanism of a planetary gear type that decelerates an output of a driving source and a transmission mechanism that transmits the output of the reducer mechanism to a tip tool. The reducer mechanism and the transmission mechanism are housed in a case, and the case is connected to a housing. The power tool is further provided with a cover member that covers an opening of the case, a ring gear that is included in the reducer mechanism and supported by the cover member, a bearing that rotatably supports a spindle that is included in the transmission mechanism, the bearing being disposed inside the case, and a space portion that is placed between the cover member and the ring gear in a periphery of the bearing, the space portion being capable of stocking a grease, and a first through hole formed in the cover member so as to allow the inside and outside of the case to communicate with each other through the space portion.
According to the present invention, it is possible to effectively suppress a pressure increase inside the case in which the reducer mechanism and the transmission mechanism are housed, without causing an increase in size and degradation in durability of the power tool.
The following description will explain one example of an embodiment of the present invention in detail.
As illustrated in
The housing 2 has a handle unit 20 to be grabbed by a worker, that is, an operator, and a body unit 21 having a cylindrical shape that is integrally molded with one end of the handle unit 20. On one end side of an inner space of the body unit 21, an electric motor 30, which is driven by a battery (not illustrated) serving as a power source housed in the battery case 3, is housed. On the other end side of the inner space of the body unit 21, a reducer mechanism 31 and a case 33 made of metal (an aluminum alloy in the present embodiment) and housing an impact mechanism 32 serving as a transmission mechanism are housed. An output shaft 30a of the electric motor 30 is rotatably supported on bearings 40a and 40b disposed on the front and rear sides in the axial direction. When using the impact driver 1, the one end side of the body unit 21 in which the electric motor 30 is housed forms the rear end.
As illustrated in
The rotation of the electric motor 30 is decelerated by the reducer mechanism 31 of a planetary gear type and transmitted (inputted) to the spindle 41. The reducer mechanism 31 includes a sun gear (pinion gear 50) attached to the tip of the output shaft 30a, an outer gear (ring gear 51) fixed relative to the rotation direction of the output shaft 30a and two planetary gears 52 that are meshed with the pinion gear 50 and the ring gear 51. The respective planetary gears 52 are pivotally and rotatably supported by a support shaft 53 secured to a flange unit 41a formed on the rear end portion of the spindle 41. By using this reducer mechanism 31 of the planetary gear type, the rotation of the electric motor 30 is decelerated and transmitted (inputted) to the spindle 41.
A cylindrical hammer 60 is attached on the outside of the spindle 41 so as to be movable along the axial direction. A plurality of hammer claws 60a formed on the tip of the hammer 60 are made to be meshed with anvil claws 43a formed on the anvil 43. The anvil 43 is rotated by the hammer 60 in accordance with the mesh between the hammer claws 60a and the anvil claws 43a. Ina cylindrical groove formed in the hammer 60, a spring 61 that abuts a bottom surface of the groove and the flange unit 41a of the spindle 41 is disposed. A pressing force toward the anvil 43 is applied to the hammer 60 by the spring force of the spring 61.
Steel balls 62 are disposed between a cam groove 41b formed on an outer circumferential surface of the spindle 41 and a cam groove 60b formed on an inner circumferential surface of the hammer 60, so that the rotation of the spindle 41 is transmitted to the hammer 60 by the steel balls 62. The hammer 60 is reciprocatably moveable in the axial direction with respect to the spindle 41, so that, by the movement of the hammer 60 in the axial direction exerted by the spring force of the spring 61 and the rotation of the hammer 60 exerted by the spindle 41, the anvil claws 43a are impacted by the hammer claws 60a.
When the striking energy of the hammer 60 is reduced to cause a reduction in the rotary torque of the anvil 43 after the impacting, the hammer 60 repels from the anvil 43. Then, the hammer 60 retracts toward the reducer mechanism 31 along the cam grooves 41b and 60b. However, prior to abutting against a stopper 63, the hammer 60 is made to move forward toward the anvil 43 by the spring force of the spring 61. Here, the rotation of the spindle 41 is transmitted to the hammer 60 via the steel balls 62 disposed between the two cam grooves 41b and 60b, so that the hammer 60 is accelerated. The rotation of the spindle 41 continues even during the retraction of the hammer 60 toward the stopper 63; therefore, when the hammer claws 60a that have moved over the anvil claws 43a again impact the anvil claws 43a, the anvil 43 is impacted by the hammer 60 that has been rotated by 180 degrees. In this manner, the impacting onto the anvil 43 is repeatedly carried out by the movements of the hammer 60 in the axial directions and rotations thereof around the axis, and the striking torque is continuously given to the screw member so that the screw member is tightened.
In this case, inside the body unit 21 of the housing 2, a cover member (inner cover 70), which is fixed relative to the rotation direction of the output shaft 30a of the electric motor 30, is installed. The inner cover 70, which is fixed to the body unit 21 as described above, is on the other hand fitted to the case 33 so as to cover the opening of the case 33. The ring gear 51, which is installed inside the case 33, is engaged with the inner cover 70 so as to be fixed relative to the rotation direction of the output shaft 30a of the electric motor 30. The following description will explain the structure in detail.
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In an impact driver 1 constructed as described above, the air inside the case 33, which is expanded due to heat generated by the reducer mechanism 31 and the impact mechanism 32 during their operations, is released to the outside of the case 33 through the air release passage. In this case, since most of the air release passage is composed of the through holes 77, 74 and 82, the flow resistance of the air release passage is small so that the air inside the case 33 is smoothly released. In addition, since the through holes 77, 74 and 82 forming most part of the air release passage are disposed on one straight line, the flow resistance of the air release passage is made further smaller, and the air inside the case 33 is released further smoothly. Moreover, since the felt member 75 is disposed between the through holes 74 and 77 forming the air release passage, grease stocked in the concave portion 73 is prevented from leaking.
Additionally, the ring gear 51 is detented relative to the inner cover 70 by the protrusion 51a inserted into a gap between the upper side horizontal portion 76a and the lower side horizontal portion 76b of the rubber member 76 housed in the concave portion 73 of the inner cover 70. Therefore, shock in the rotation direction of the ring gear 51 is absorbed by the rubber member 76 so as to be attenuated. Moreover, the felt member 75 is interposed between the vertical portion 76c of the rubber member 76 housed in the concave portion 73 of the inner cover 70 and the bottom of the concave portion 73. Therefore, shock in the axial direction of the ring gear 51 is absorbed by the felt member 75 so as to be attenuated. That is, the rubber member 76 functions as a shock attenuation mechanism that attenuates the shock in the rotation direction of the ring gear 51. Moreover, the felt member 75 functions as an impact alleviating mechanism that attenuates the shock in the axial direction of the ring gear 51. In this case, as described above, the felt member 75 also functions as a filter that prevents grease from leaking.
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The present invention is not limited by the above-mentioned embodiments, but may be variously modified without departing from the gist of the present invention. For example, in the present embodiment, a space portion for use in stocking grease is formed by the concave portion 73 formed in the inner cover 70; however, this space portion may be formed at an optional position on the circumference of the bearing 42, between the inner cover 70 and the ring gear 51. Moreover, the present invention may be adopted in a power tool other than an impact driver (for example, an impact wrench). The present invention may also be applied to a power tool with a cord. The present invention may be also adopted in a power tool provided with a driving source other than an electric motor, such as a pneumatic pressure motor or the like.
Number | Date | Country | Kind |
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2012-7062 | Mar 2012 | JP | national |