Rotation output device

A rotation output device including a lock mechanism for automatically locking an output shaft without inertia or a need to pivot the output shaft by the operator after the input shaft stops rotating. The rotation output device includes an output gear for inputting a rotation driving force; a lock ring restricted from rotating; output rings for rotating integrally with the spindle; a click spring for rotating the output rings with respect to the output gear; float gears which are held by the output ring to be urged radially outward and are fixedly engageable with the lock ring; and central pin insertion through-holes and side pin insertion through-holes provided in the output rings for releasing the float gears radially outward and fixedly engaging the float gears with the lock ring. The click spring relatively rotates the output rings by the stoppage of the rotation driving of the output gear.

FIELD OF THE INVENTION

The present invention relates to a rotation output device usable in, for example, an electric tool such as an electric driver or the like and capable of locking an output shaft of a motor when the motor is controlled to stop and thus the output shaft is stopped.

BACKGROUND ART

Conventionally, electric tools having a function of locking an output shaft (spindle) when the motor is controlled to stop as described above are known (for example, Japanese Laid-Open Patent Publication No. 11-37187, hereinafter “Patent Document 1”).

A lock mechanism described in Patent Document 1 has a play angle between an output shaft and an input shaft and includes, on the output shaft side, a locking plate which is urged radially outward (in a locking direction) and a holding plate for restricting the position of the locking plate by a guide groove.

The lock mechanism acts as follows. While the input shaft is being rotated (driven), the holding plate restricts the locking plate at a radially inward position. Therefore, the output shaft is not locked and rotates freely. When the motor stops rotating and thus the input shaft stops rotating, the output shaft is rotated by a play angle because of inertia. Therefore, the locking plate associated with the input shaft moves radially outward through the guide groove of the holding plate. As a result, the output shaft is automatically locked.

As described above, the lock mechanism described in Patent Document 1 instantaneously locks the output shaft using inertia when the motor is stopped. Therefore, the operator does not need to pivot the output shaft by the play angle after the motor is stopped, which significantly improves the operability.

However, the lock mechanism described in Patent Document 1 which uses inertia has the following problem.

When, for example, the motor is stopped after rotating at a low speed, “pivoting because of inertia” is not generated to a sufficient degree. Then, the output shaft is not automatically locked.

In this case, the following occurs. If the operator pivots the output shaft in the same direction as the direction in which the output shaft has been rotated, this means that the output shaft is pivoted in the same direction as the “pivoting because of inertia.” Therefore, the output shaft is locked. By contrast, if the operator pivots the output shaft on the opposite direction, the input shaft is also pivoted in the same direction as the output shaft. Therefore, the relative positions of the locking plate and the input shaft are not changed. As a result, the output shaft is not locked.

When the output shaft is not locked as described above, the lock mechanism does not provide its function. In addition, since the output shaft is not locked, the operator needs to pivot the output shaft in the state of receiving a load of the stoppage of the motor for an extended period of time. This deteriorates the operability.

In order to solve this problem, Patent Document 1 adds a lock operating mechanism using a planet gear set with such a structure, in whichever direction the operator may pivot the output shaft, the relative positions of the locking plate and the input shaft are necessarily changed so as to guarantee that the output shaft is locked.

However, in the case where such a lock operating mechanism is added, a complicated mechanism of the planet gear set is additionally required, which may lower the reliability, durability or the like of the lock mechanism itself. A space for the lock operating mechanism is also required, and the lock mechanism cannot be formed to be compact.

SUMMARY OF THE INVENTION

The present invention has an object of providing a rotation output device including a lock mechanism for automatically locking an output shaft without inertia and with no need of pivoting the output shaft by the operator after the input shaft stops rotating.

In one embodiment, a rotation output device according to the present invention comprises a rotation input body configured to input a rotation driving force; a rotation output body located coaxially with the rotation input body and configured to receive a driving force from the rotation input body with a predetermined play angle and to output a rotation force; a fixing member provided around an outer circumferential surface of the rotation output body and restricted from rotating; a guide holding plate fixed to the rotation output body and configured to rotate integrally with the rotation output body; a relative rotation means fixed to the rotation output body and configured to rotate the guide holding plate with respect to the rotation input body; a movement locking plate that is held by the guide holding plate, wherein the movement locking plate is configured to be urged radially outward and to fixedly engage the fixing member; a lock operation groove provided in the guide holding plate and configured to release the movement locking plate radially outward and fixedly engage the movement locking plate with the fixing member; and a release operation groove provided in the rotation input body and configured to guide the movement locking plate radially inward and to release the movement locking plate from the fixed engagement with the fixing member by the rotation of the rotation input body. The relative rotation means is configured to relatively rotate the guide holding plate upon stoppage of the rotation driving of the rotation input body.

The stoppage of the rotation driving occurs when, and after, the rotation driving is stopped. According to the above-described structure, the relative rotation means rotates the guide holding plate with respect to the rotation input body by the stoppage of the rotation driving of the rotation input body. Therefore, the lock operation groove provided in the guide holding plate releases the movement locking plate radially outward and fixedly engages the guide holding plate with the fixing member. Thus, the lock mechanism can be automatically placed into a lock state.

By the rotation of the rotation input body, the release operation groove provided in the rotation input body guides the movement locking plate radially inward and releases the movement locking plate from the fixed engagement with the fixing member. Thus, the lock mechanism can be automatically released from the lock state.

In one embodiment of the present invention, the relative rotation means is configured to rotate the guide holding plate with respect to the rotation input body in a direction in which the rotation input body was last rotated after the rotation input body stops rotating.

The above-described structure reduces the change in relative positions of the lock operation groove and the release operation groove needed to release the lock mechanism from the lock state. As a result, the movement locking plate can be released radially outward and fixedly engaged with the fixing member with certainty, and thus the lock mechanism can be placed into a lock state.

In one embodiment of the present invention, the relative rotation means rotates the guide holding plate with respect to the rotation input body by an angle corresponding to the play angle.

The above-described structure eliminates the need to change the relative positions of the lock operation groove and the release operation groove to release the lock mechanism from the lock state. As a result, the movement locking plate can be released radially outward and fixedly engaged with the fixing member with further certainty, and thus the lock mechanism can be placed into a lock state. Since the movement locking plate can be engaged with the fixing member without loosely engaging the movement locking plate with the lock operation groove or the release operation groove, a lock mechanism with no play can be provided.

In one embodiment of the present invention, the relative rotation means comprises a plurality of click springs. According to the above-described structure, as compared to a structure having one click spring, the force for rotating the guide holding plate with respect to the rotation input body can be increased. Thus, the guide holding plate can be rotated with respect to the rotation input body with certainty.

In one embodiment of the present invention, the rotation input body includes an arc-shaped groove and each click spring comprises an arc-shaped claw having substantially the same shape as that of the arc-shaped groove and being configured to engage the arc-shaped groove. According to the above-described structure, the rotation of the guide holding plate with respect to the rotation input body can be smoothly caused by the arc-shape of the arc-shaped groove and the arc-shaped claw. Thus, the guide holding plate can be rotated with respect to the rotation input body with further certainty.

In one embodiment of the present invention, the arc-shaped claw of each click spring is engaged with the arc-shaped groove with an elastic force. According to the above-described structure, as compared to, for example, a structure in which the arc-shaped claw is engaged with the arc-shaped groove by a driving force from a separate driving source, the number of parts and components can be reduced and the assembly thereof is easier. In the case where the arc-shaped claw is engageable with the arc-shaped groove by an elastic force, the structure is relatively simple. Therefore, the possibility of the reliability, durability or the like of the lock mechanism itself being deteriorated can be lowered.

In one embodiment of the present invention, an escaping portion is provided between the movement locking plate and the rotation output body. According to the above-described structure, an escaping portion is formed. Therefore, the rotation of the rotation output body is not transmitted.

Accordingly, the movement locking plate can be certainly prevented from rotating by an angle corresponding to the “escaping portion” together with the rotation output body. Thus, the movement locking plate can be certainly prevented from rotating together with the rotation output body. Accordingly, even when the rotation input body and the rotation output body are rotated together with no play angle, the movement locking plate is not rotated. As a result, the lock function can be provided with certainty.

In one embodiment of the present invention, the guide holding plate has a plurality of lock operation grooves; and the movement locking plate has a plurality of engagement projections configured to be engaged with the lock operation grooves. According to the above-described structure, the locking operation is performed by engaging a plurality of engagement projections of the movement locking plate with a plurality of lock operation grooves of the guide holding plate.

Therefore, the guide holding plate and the movement locking plate are engaged with each other at a plurality of positions, which improves the rigidity at the plurality of positions and thus improves the lock torque in the lock state. As a result, the lock torque by the movement locking plate in the lock state is improved, which provides a more certain and stable lock function.

In one embodiment of the present invention, the guide holding plate comprises a fixing part that is thicker than the remaining part of the guide holding plate, and the fixing part is configured to fix the guide holding plate to the rotation output body. According to the above-described structure, the thickness of a fixing part of the guide holding plate for fixing the guide holding plate and the rotation output body to each other is made greater than the thickness of the remaining parts. Therefore, the area which receives the pressure from the rotation output body can be enlarged.

Accordingly, the guide holding plate can receive the rotation torque from the rotation output body with certainty while the guide holding plate is made thinner. Thus, the guide holding plate can receive the rotation torque from the rotation output body with certainty and thus the lock torque can be improved, while the guide holding plate is formed to be compact.

In one embodiment of the present invention, the rotation output device further comprises a restriction plate configured to restrict a positional change of the movement locking plate. The restriction plate is provided between the movement locking plate and the fixing member, and is further configured to integrally rotate with the movement locking plate such that an outer end of the restriction plate contacts the fixing member. According to the above-described structure, the restriction plate does not slide along the movement locking plate while being in contact therewith. This prevents the restriction plate from adversely influencing the locking or releasing operation of the movement locking plate.

Thus, even though the restriction plate is provided, the locking function of the movement locking plate can be stably provided with no undesirable possibility of being inhibited. The positional change of the movement locking plate is restricted by the restriction plate. Therefore, the movement locking plate, which is in the release state, is prevented from being placed into the lock state by an external force other than the rotation input body.

In one embodiment of the present invention, the rotation output device further comprises a sliding resistance increasing means for increasing a sliding resistance, the sliding resistance increasing means being provided at a position where the restriction plate contacts the fixing member. The sliding resistance increasing means encompasses means formed of an elastic material. According to the above-described structure, the restriction plate contacts the fixing member with a higher sliding resistance. This makes the restriction plate more easily influenced by the restriction on the rotation by the fixing member. As a result, the position of the restriction plate in the rotation direction is maintained with certainty, and the position of the movement locking plate in the rotation direction is maintained certainly by the restriction plate.

In the case where the sliding resistance increasing means is formed of an elastic material, the restriction plate and the fixing member are allowed to contact each other constantly. Namely, since the relative positional offset between the restriction plate and the fixing member is absorbed by the elastic material, the restriction plate and the fixing member can be in contact with each other constantly. Therefore, the position of the movement locking plate in the rotation direction is maintained constantly and certainly by the restriction plate.

In one embodiment of the present invention, the rotation output device includes a plurality of movement locking plates in a circumferential direction, wherein the plurality of movement locking plates are configured to be integrally rotated by the restriction plate.

According to the above-described structure, the lock torque can be increased by providing a plurality of movement locking plates. Since the plurality of movement locking plates are integrally rotated by one restriction plate, the plurality of movement locking plates are provided with a completely equal force of maintaining the position thereof in the rotation direction. Accordingly, the positions of the movement locking plates in the rotation direction are not separately maintained. Even in the case where a plurality of movement locking plates are provided, the positions thereof in the rotation direction can be constantly maintained in synchronization with each other.

A rotation output device according to the present invention is usable in an output system of an electric tool and also an appliance requiring a rotation output. Thus, the operations of the electric tool or the like in a lock state can be performed very easily.

According to the present invention, in a rotation output device including a lock mechanism for automatically locking an output shaft when the input shaft stops rotating, the output shaft is certainly locked without a complicated structure of a planet gear set or the like, or inertia.

DESCRIPTION OF REFERENCE NUMERALS

10Rotation output device

10A Lock mechanism

DETAILED DESCRIPTION

One embodiment of the present invention will be described in detail with reference to the drawings.FIG. 1shows an electric tool adopting a rotation output device according to the present invention. As shown inFIG. 1, the electric tool includes a housing1having a handle1a to be held by the operator when the operator uses the electric tool, an electric cord2provided below the handle la, a spindle3provided forward to the housing1, a chuck4attached to the spindle3, and a drill bit5supported by the chuck4.

The housing1includes a main body case II and a gear case12attached to a front part of the main body case11. The housing1accommodates therein a motor M selectably rotatable in a forward direction or a reverse direction and a rotation output device10(seeFIG. 2) described later. A rotation driving force of the motor M is transmitted to the spindle3via the rotation output device10. A switch handle6for inputting a driving signal to the motor M is provided in an upper front part of the handle1of the housing1.

This embodiment is described with a general type electric tool having an electric cord. The power source of the electric tool is not specifically limited, and the present invention is also applicable to a portable type electric tool using a battery. The present invention is not limited to being used in an electric tool and is also applicable to an appliance used in a driver, grinder, router or the like. The present invention is not limited to being used in an appliance driven by electricity, and is applicable to an appliance driven by compressed air, a hydraulic appliance or the like.

Next, with reference toFIG. 2andFIG. 3, the rotation output device10provided in the electric tool will be described. The rotation output device10includes a lock mechanism10A in the gear case12. The lock mechanism10A transmits the rotation output from an output shaft M1of the motor M, and locks or releases the spindle3.

The lock mechanism10A mainly includes the following elements: an output gear31for receiving a rotation driving force from the output shaft M1of the motor M, a lock ring33located at an outer edge of the lock mechanism10A for fixing the lock mechanism10A to the gear case12, two float gears34engageable with inner teeth of the lock ring33, two output rings32(32a,32b) fixedly engageable with the spindle3for holding the float gears34from the front and the rear in the axial direction of the lock mechanism10A, and a click spring38fixedly engageable with the spindle3and stopped by the output gear31with these elements, the lock mechanism1OA automatically locks the spindle3at the same time when, or after, the motor M is stopped, and automatically releases the spindle3when the motor M starts rotating.

As shown inFIG. 2, the output shaft M1is located at the direction of 7 o'clock with respect to the spindle3when seen from the back (inFIG. 2bottom left). Outer circumferential teeth of an input gear M2for transmitting the rotation driving force of the output shaft M1to the output gear31, and outer circumferential teeth of an outer gear of the output gear311may be of a helical gear type or a spar gear type.

With reference toFIG. 4andFIG. 5, a detailed structure of the lock mechanism10A will be described.FIG. 4shows the elements of the lock mechanism10A in the rotation output device10in an exploded state. InFIG. 4, the elements are shown both in a front view and a rear view.FIG. 5is an exploded perspective view showing the elements of the lock mechanism10A in the rotation output device10.

As shown inFIG. 4, the lock mechanism10A includes the chuck-side output ring32bthe lock ring33, the two float gears34, two coil springs35, a legged O-ring36, a delay plate37, the motor-side output rings32a, the click spring38, and the output gear31. These elements are arranged in this order from the side of the chuck4. These elements, except for the two float gears34and the coil spring35, are assembled as a ring and coaxially provided.

The spindle3includes a chuck shaft insertion section3a, a hexagonal section3b, a shaft fixing section3c, an oblong connection section3d, and a shaft fixing section3ewhich are arranged in this order from the side of the chuck4shown inFIG. 1. The hexagonal section3bhas a hexagonal shape, when seen from the front, generally inscribed to a circle having a diameter which is about 1.5 times the diameter of the chuck shaft insertion section3a. The shaft fixing section3chas a cross section having substantially the same diameter as that of the cross section of the chuck shaft insertion section3a, and is axially supported by a bearing13(FIG. 3) which is provided in a front part of the inside of the gear case12. The oblong connection section3dhas an oblong cross section having a diameter shorter by a certain degree than that of the cross section of the chuck shaft insertion section3a. Herein, “oblong” refers to a shape obtained by changing two separate portions of a circle interposing the center of the circle into two parallel straight lines each having a shorter length than the diameter of the circle. The shaft fixing section3ehas a cross section having a diameter which is about a half of the diameter of the chuck shaft insertion section3aand is axially supported by a bearing (not shown) provided at about the center of the inside of the gear case12.

The output gear31is a spar gear having a diameter which is about three times the diameter of the oblong connection section3dand an appropriate thickness. The output gear31has a circular recessed portion31ain a front surface thereof. The circular recessed portion31ahas a diameter which is about ⅘ of the diameter of the output gear31and a depth which is about 1/7 of the thickness of the output gear31. The output gear31has a shaft insertion hole31bat the center of the output gear31when seen from the front. The shaft insertion hole31bis loosely engageable with the oblong connection section3d. The output gear31also has pin insertion holes31copposed to each other with the shaft insertion hole31binterposed therebetween. Into the pin insertions31c, stoppage pins provided at the center of the float gears34as described later are to be inserted. The output gear31may be a helical gear.

The shaft insertion hole31bhas a generally oblong shape when seen from the front, in which a top part and a bottom part are arc-shaped and projecting outward. The oblong connection section3dis loosely engageable with the shaft insertion hole31bwith a play angle α (seeFIG. 6). The pin insertion holes31ceach have a generally isosceles triangular shape formed of three continuous circles each having a diameter slightly longer than that of the stoppage pin of the float gears34, when seen from the front. The three circles are located at positions of three angles (in this embodiment, located at positions of 0 degrees, 102 degrees and 258 degrees). The pin insertion holes31ceach have a depth which is about ¼ of the thickness of the output gear31. The pin insertion holes31care projected radially outward.

The arcs forming the bottom side of each isosceles triangle are located at a pitch corresponding to the differential provided by the play angle α of the stoppage pin. The pin insertion holes31cmay be through-holes in the output gear31.

In a circumferential surface of the circular recessed portion31a, arc-shaped engagement grooves31dengageable with hooks at the tip of the click spring38as described later are formed. The engagement grooves31dare opposed to each other with the center of the circular recessed portion31ainterposed therebetween, namely, on both sides of the shaft insertion hole31b. The phantom straight line connecting the engagement grooves31dperpendicularly crosses the phantom straight line connecting the pin insertion holes31c. The length of each engagement groove31dcorresponds to the play angle α at which the oblong connection section3dand the circular recessed portion31aare loosely engaged with each other.

In more detail, the engagement grooves31dare to rotate with respect to the hooks at the tip of the click spring38so as to press spring arms described below. In order to realize such a relative rotation, the diameter of the arc of each engagement groove31dis changed in the direction in which the engagement grooves31drotate with respect to the hooks.

The click spring38is generally Z-shaped when seen from the front, and includes two arc-shaped, elastic spring arms38aopposed to each other with the center of the click spring38interposed therebetween. The click spring38also includes a longitudinal oblong central plate38b. The spring arms38aand the central plate38bare integrally formed. The central plate38bhas two arc portions opposed to each other with the center thereof interposed therebetween. Each arc portion of the central plate38band the spring arm38aconnected thereto form a substantial quarter circumference of a circle having a diameter which is slightly shorter than the diameter of the circular recessed portion31a.

Each spring arm38ahas a hook38cat the tip thereof. The hook38cprotrudes radially outward and is engageable with the respective engagement groove31d. The central plate38bhas a shaft insertion hole38dhaving substantially the same shape as that of the cross section of the oblong connection section3d, at the center of the central axis running in the longitudinal direction of the central plate38b. The central plate38balso has pin insertion through-holes38ehaving the same shape as that of the pin insertion holes31cwhen seen from the front. The pin insertion through-holes38eare located in positional correspondence with the pin insertion holes31c, on the central axis of the shaft insertion section38dand outside of the shaft insertion section38d.

The motor-side output ring32ahas a generally oblong shape, and has substantially the same diameter as that of the circular recessed portion31aand an appropriate thickness. The motor-side output ring32ahas engagement claws32cat about the center of side straight portions. The engagement claws32care formed by bending portions near the side straight portions toward the chuck4. The motor-side output ring32aalso has a shaft insertion hole32d, at the center thereof, having substantially the same shape as that of the cross section of the oblong connection section3d, and central pin insertion through-holes32ein positional correspondence with the pin insertion holes31c. The engagement claws32care engageable with engagement holes32fof the chuck-side output ring32b.

Each central pin insertion through-hole32eis formed of three continuous circles each having a diameter slightly longer than that of the stoppage pin of the float gears34. The three circles are located at positions of three angles (in this embodiment, located at positions of 0 degrees, 134 degrees and 226 degrees). Both of two ends of a half circle of the upper circle are respectively connected to each of the two bottom circles by a radial straight line having a length of ¼ of the radius of each of the three continuous circles. Among the three arcs of the three circles, the arcs of the two bottom circles are located at a pitch corresponding to the differential provided by ½ of the play angle α of the stoppage pin.

A part around the shaft insertion hole32dhaving an appropriate width is projected toward the chuck4, namely, is formed to be thicker than the remaining part of the output ring32a. In more detail, the part around the shaft insertion hole32dhas a thickness which is about 1.3 times the thickness of the remaining part.

The delay plate37is formed of a thin plate which is smaller by a certain degree than the phantom circle made of the teeth of the output gear31. The delay plate37has a stoppage groove37aaround the outer perimeter thereof. The stoppage groove37ais circular when seen from the front and has an arc-shaped cross section protruding toward the motor M. The legged O-ring36slides in engagement with the stoppage groove37a. The delay plate37has a through-hole37bat the center thereof, which is circular when seen from the front and has a diameter larger by a certain degree than that of the oblong connection section3d.

The delay plate37has two pin insertion through-holes37chaving the same shape as that of the central pin insertion through-holes32e. The pin insertion through-holes37chave a generally isosceles triangular shape protruding radially outward, and are opposed to each other with the through-hole37binterposed therebetween. The delay plate37also has two rectangular through-holes37dfor allowing the engagement claws32cto pass therethrough. The rectangular through-holes37dare opposed to each other with the through-hole37binterposed therebetween. The phantom straight line connecting the rectangular through-holes37dperpendicular crosses the phantom straight line connecting the pin insertion through-holes37c, and the rectangular through-holes37dare longer in the direction of the phantom straight line connecting the pin insertion through-holes37c.

The legged o-ring36includes a circular ring portion36ahaving a circular cross section and being slidable in engagement with the stoppage groove37a. The legged O-ring36also includes cylindrical legs36bhaving a height which is substantially the same as the diameter of the cross section of the circular ring portion36aand an appropriate diameter.

The legs36bare provided at positions of three angles (0 degrees, 120 degrees, and 240 degrees) which divide the circular ring portion36asubstantially equally. A radially inward part of the circumference of each leg36bcoincides with the inner circumference of the circular ring portion36a. A front circular surface of each leg36bprojects toward the chuck4from the circular ring portion36a. The appropriate diameter of the legs36bis determined such that, when the legged O-ring36is attached to the lock ring33, the radially outer end of each leg36bis inner to the outer circumference of the lock ring33and such that the legs36bcan be inserted into insertion recesses33ddescribed later. The circular ring portion36aand the legs36bare integrally formed of an elastic rubber or resin material.

The float gears34are each generally comb-shaped with four legs and an arc-shaped portion34aprojecting upward. The arc-shaped portion34ahas a diameter which is slightly smaller than the diameter of the phantom circle made of the inner teeth of the lock ring33described later. The arc portion34ahas three teeth34b, at the center of the top edge thereof, which are engageable with the inner teeth of the lock ring33. The three teeth34bare located to be right and left symmetrical with respect to the central line of the float gear34.

Each float gear34has a loose engagement portion34c, at the center of the bottom portion thereof. The oblong connection section3dis loosely engageable with the loose engagement portion34cwith the play angle α. Each float gear34also has right and left symmetrical center legs34dforming a leg portion of the loose engagement portion34c. The distance between each leg34dand the respective outer end of the float gear34is about ¼ of the entire width of the float gear34.

Each float gear34has right and left symmetrical outer legs34e, at two ends thereof in the width direction and therefore outside the center legs34d, with an appropriate distance from the center legs34d. The bottom surface of each outer leg34dis at about the same level as the ends of the arc of the loose engagement portion34c, and each center leg34dhas a length which is about twice the length of the outer leg34eand a width which is about a half of the width of the outer leg34e.

The appropriate distance between the outer leg34eand the center leg34dis longer by a certain degree than the diameter of the coil spring35in the width direction described later. A spring attachment portion34floosely engageable with the coil spring35is formed between each outer leg34eand the corresponding center leg34d.

Each float gear34has a stoppage pin34gon the central axis thereof in the width direction, at about the center between the top edge of the arc portion34aand the top edge of the loose engagement portion34c. The stoppage pin34gfixedly runs through the float gear34and has an appropriate diameter and an appropriate length. The length of a part of the stoppage pin34gwhich protrudes from the rear surface of the float gear34toward the motor M is fixed to be about four times the length of a part of the stoppage pin34gwhich protrudes from the front surface of the float gear34toward the chuck4.

The float gear34also has right and left symmetrical stoppage projections34hat about the center between the top edge of the arc portion34aand the top edge of the loose engagement34c, at an appropriate distance from the stoppage pin34g. The stoppage projections34hare circular when seen from the front, have substantially the same diameter as that of the stoppage pin34g, and are projected toward the chuck4by press working. The length of a part of each stoppage projection34hwhich protrudes from the front surface of the float gear34toward the chuck4is fixed to be about 1.5 times the length of the part of the stoppage pin34gwhich protrudes from the front surface of the float gear34toward the chuck4. The stoppage projections34hare only needed to operate and function in the same manner as the stoppage pin34g. The stoppage projections34hmay be fixed to the front gear34instead of being formed by press working as in this embodiment.

The lock mechanism10A has two upper and lower symmetrical floating gears34, and one coil spring35is provided to be loosely engaged with the spring attachment portion34fof the upper and lower symmetrical floating gears34on the right side, and another coil spring35is provided to be loosely engaged with the spring attachment portion34fof the upper and lower symmetrical floating gears34on the left side.

The lock ring33is ring-shaped with an outer circumference which is larger by a certain degree than the phantom circle made of the teeth of the output gear31and with an inner circumference which is slightly smaller than the circular recessed portion31a. The lock ring33has inner teeth33aengageable with the float gears34, on an inner circumferential surface thereof. The lock ring33has fixing projections33bwhich are circular when seen from the front, at positions of three angles (90 degrees, 210 degrees, and 330 degrees) which divide the lock ring33substantially equally. The fixing projections33beach have a predetermined diameter and are projected toward the chuck4by press working. The lock ring33has an arc-shaped cutout33cprojecting radially inward, at a bottom left position of the outer circumference thereof. The cutout33cis provided for preventing interference between the output shaft M1of the motor M and the lock ring33.

The fixing projections33bare provided for fixedly engaging the lock ring33with the gear case12. Recessed portions on the rear surface of the lock ring33which are formed by the press working for forming the fixing projections33beach form the insertion recesses33d, into which the leg36bis to be inserted.

The chuck-side output ring32bhas a circular shape, when seen from the front, having the same diameter as that of the arc-shaped portions of the motor-side output ring32aand has an appropriate thickness. Like the motor-side output ring32a, the chuck-side output ring32bhas a shaft insertion hole32d, at the center thereof, having substantially the same shape as that of the cross section of the oblong connection section3d, and central pin insertion through-holes32e. A part around the shaft insertion hole32dhaving an appropriate width is projected toward the chuck4, namely, is formed to be thicker than the remaining part of the output ring32b.

The chuck-side output ring32bhas right and left symmetrical side pin insertion through-holes32gon the right and on the left of each central pin insertion through-hole32e. The distance between each side pin insertion through-hole32gand the central pin insertion through-hole32eis substantially the same as the distance between the stoppage pin34gand each stoppage projection34h. Each side pin insertion through-hole32ghas a shape deformed from the central pin insertion through-hole32eas follows. The side pin insertion through-hole32gis formed of three continuous circles and thus has arcs projecting in three directions, but one of the two bottom circles, among the three circles forming the central pin insertion through-hole32e, is lower than the other bottom circle. The higher bottom circle of the side pin insertion through-hole32gis located closer to the vertical central line of the chuck-side output ring32b.

The chuck-side output ring32bhas insertion holes32fengageable with the insertion claws32cand opposed to each other with the center of the chuck-side output ring32binterposed therebetween. The phantom straight line connecting the insertion holes32fperpendicularly crosses the phantom straight line connecting the two central pin insertion through-holes32e. The pin insertion holes31c, the central pin insertion through-holes32e, and the pin insertion through-holes38eare located at the same distance from the radial center of the lock mechanism10A.

Owing to the above-described structure, as shown inFIG. 6, the upper and lower symmetrical float gears34are engaged with the lock ring33, such that the teeth34bare engaged with the inner teeth33aof the lock ring33and the coil springs35in a compressed state are loosely engaged with the right and left spring attachment portions34f. In this state, the legs36bare inserted into the insertion recesses33d, thereby attaching the legged O-ring36into the lock ring33. The stoppage pins34gprojecting toward chuck4are inserted into the central pin insertion through-holes32eof the chuck-side output ring32b. The stoppage projections34hare respectively inserted into the side pin insertion through-holes32g. The engagement claws32cinserted through the rectangular through-holes37dare engaged with the engagement holes32f, such that the motor-side output ring32aand the chuck-side output ring32bhold the delay plate37, the legged O-ring36, the lock ring33and the float gear34therebetween. Thus, the rear surface of the legged O-ring36interposed between the delay plate37and the lock ring33is contactable and thus slidable with the stoppage groove37ahaving the arc-shaped cross section.

Then, the output rings32, the lock ring33and the like which are assembled together as described above are positioned coaxially with the click spring38and the output gear31, and the shaft fixing section3eof the spindle3is inserted from the shaft insertion hole32dof the chuck-side output ring32bup to the position where the shaft insertion hole32dof the chuck-side output ring32bsubstantially contacts the end surface of the oblong connection section3dbordering the shaft fixing section3cof the spindle3. In this manner, the lock mechanism10A is assembled as shown inFIG. 6.

Next, the locking function of the lock mechanism10A having the above-described structure will be described with reference toFIG. 6throughFIG. 10.FIG. 6is a front view of the lock ring33, the float gears34, the motor-side output ring32a, and the output gear31in a lock state.FIG. 7is a front view of the output gear31, the click spring38, and the delay plate37in the same state.FIG. 8is a front view of the lock ring33, the float gears34, the motor-side output ring32a, and the output gear31in a release state where the output gear31is rotated in the direction of arrow r1by the driving force of the motor M.FIG. 9is a front view of the output gear31, the click spring38, and the delay plate37in the same state.FIG. 10is a front view of the output gear31, the click spring38, and the delay plate37in a release state where the output gear31is rotated in the direction of arrow r3by the driving force of the motor M.

Hereinafter, the operation in each state will be described with respect to the respective figures. First, as shown inFIG. 6andFIG. 7, in the lock state when the motor M is at a stop, the upper and lower float gears34are pressed radially outward by an urging force of the coil springs35(not shown inFIG. 6orFIG. 7). As a result, the inner teeth33aare put into engagement with the teeth34b. The stoppage pins34gand the stoppage projections34hare stopped at a locked position L, which is at a radially outward position of the pin insertion holes31c, the central pin insertion through-holes32eand the side pin insertion through-hole32g. Therefore, the output rings32and the output gear31are nonrotatable with respect to the lock ring33. As a result, the spindle3having the oblong connection section3dinserted into the shaft insertion hole32dwith no play angle, together with the output rings32, is nonrotatable with respect to the gear case12with which the lock ring33is fixedly engaged.

In this state, the rotation of the motor M (FIG. 1) is transmitted from the output shaft M1(FIG. 2) to the output gear31(FIG. 2), and the shaft insertion hole31band the pin insertion holes31care rotated in the direction of arrow r1. However, due to the play angle α of the oblong connection section3dand the engagement grooves31d, the rotation of the shaft insertion hole31bis not transmitted to the spindle3until the output gear31rotates by α degrees. As a result, the output gear31rotates with respect to the spindle3, the output rings32and the like by the play angle α.

By the relative rotation of the output gear31in the direction of arrow r1, the stoppage pins34g, which are pressed in the rotation direction by a post-rotation upper side surface AC1of the pin insertion holes31c, are guided radially inward along the post-rotation upper side surface AC1and a post-rotation lower side surface AC2to a released position R1.

The delay plate37slides along the legged O-ring36attached to the lock ring33, and therefore restricts the rotation of the stoppage pins34gpressed in the rotation direction by the post-rotation upper side surface AC1of the pin insertion holes31c. Thus, the float gears34can be guided, with certainty, radially inward along the post-rotation upper side surface and the post-rotation lower side surface AC2to the released position R1.

In a consequence, as shown inFIG. 8, the float gears34move radially inward against the urging force of the coil springs35, the teeth34band the inner gears33aare disengaged from each other, and the lock mechanism10A is automatically released from the lock state. Accordingly, the rotation of the output gear31is transmitted to the oblong connection section3dby the post-rotation lower side surface AC2of the shaft insertion hole31b, and thus the spindle3can be rotated. The float gears34, which have moved radially inward, are also rotated together with the output gear31.

The stoppage pins34gare engaged with the pin insertion through-holes37c, and therefore the delay plate37rotates together with the float gears34. However, since the delay plate37slides along the legged O-ring36attached to the lock ring33, the delay plate37constantly exerts a force in the direction opposite to the rotation direction on the stoppage pins34g. Therefore, the stoppage pins34gcan be held at the released position R1with certainty while the lock mechanism10A is rotating. Accordingly, even if an external force in the rotation direction or the opposite direction exerts on the spindle3during the rotation of the lock mechanism10A, the spindle3can be held in the release state with certainty.

Since the lock mechanism10A is automatically released from the lock state by the rotation driving force of the motor M, the rotation driving force of the motor M can be output from the spindle3easily and normally. Thus, the electric tool can be operated in a normal manner.

Owing to the loose engagement portions34cof the float gears34, the interference of the oblong connection section3dand the float gears34can be prevented while the float gears34moves radially inward, which guarantees the automatic release operation.

As described above, in the state shown inFIG. 8andFIG. 9, the rotation driving force of the motor M is transmitted and thus the spindle3is rotated. At this point, as shown inFIG. 9, a part of each hook38cis stopped by a trailing angled portion c1, in the rotation direction r1, of the engagement groove31d. Owing to such a state, the lock mechanism10A is rotated while the spring arm38ais pressed radially inward.

Accordingly, when the motor M stops rotating and the spindle3gets rid of the load, the click spring38is guided by a radially outward urging force of the spring arm38ato the above-mentioned angled portion c1and the arc-shaped side surface of the engagement groove31d. Thus, the click spring38is rotated together with the spindle3in the direction of arrow r2such that the hook38cis accommodated in the engagement groove31d.

The output rings32which are fixed to the spindle3are also rotated in the direction of arrow r2by the rotation of the spindle3, but the output gear31having the play angle α (FIG. 6) with the oblong connection section3dis not rotated. Since the length of the arc-shaped surface of the engagement groove31dand the length of the arc-shaped portion of the hook38care determined in accordance with the play angle α of the output gear31, the output rings32and the output gear31are relatively rotated in the opposite direction to the direction for releasing the lock mechanism10A from the lock state.

Therefore, the stoppage pins34gat the released position R1are pressed in the direction of arrow r2by a post-rotation lower side surface AC3of the central pin insertion through-holes32e, and are also moved to the locked position L by the urging force of the coil springs35. The lock mechanism10A is placed into the lock state shown inFIG. 6andFIG. 7.

When the output gear31is rotated in the direction of arrow r3(FIG. 7) from the lock state shown inFIG. 6, the stoppage pins34gare guided radially inward to a released position R2(FIG. 7) by the pin insertion holes31cin substantially the same manner as described above, and the lock mechanism10A is released from the lock state. In the state shown inFIG. 10, the rotation driving force of the motor M is transmitted and the spindle3is rotated. At this point, as shown inFIG. 10, a part of each hooks38cis stopped by a trailing angled portion c2, in the rotation direction (arrow r3), of the engagement groove31d. Owing to such a state, the lock mechanism10A is rotated while the spring arm38ais pressed radially inward.

Accordingly, when the motor M stops rotating and the spindle3gets rid of the load, the click spring38is guided by a radially outward urging force of the spring arm38ato the above-mentioned angled portion c2and the arc-shaped side surface of the engagement groove31d. Thus, the click spring38is rotated together with the spindle3in the direction of arrow r4such that the hook38cis accommodated in the engagement groove31d. The output rings32which are fixed to the spindle3are also rotated in the direction of arrow r4by the rotation of the spindle3. The stoppage pins34gat the released position R2are moved to the locked position L (FIG. 7) by the urging force of the central pin insertion through-holes32eand the coil springs35. The lock mechanism10A is placed into the lock state shown inFIG. 6andFIG. 7.

As described above with reference toFIG. 9andFIG. 10, in accordance with whether the output gear31is rotated in the direction of arrow r1or r2, the hook38ccontacts a different position, i.e., the angled portion c1or c2of the engagement groove31d. Therefore, the part from the center of the arc-shaped surface of the engagement groove31dto the angled portion c2is formed to have a larger radius than the part from the center of the arc-shaped surface of the engagement groove31dto the angled portion c1.

Owing to such a structure, regardless of whether the output gear31is rotated in the direction of arrow r1or r2, the hook38is prevented from being completely deviated from the engagement groove31d. Therefore, by relatively rotating the spindle3in the direction in which the output gear31has been rotated by a radially outward urging force of the spring arm38awhen the motor M stops rotating and the spindle3gets rid of the load, the stoppage pins34gcan be moved to the locked position L and the locking function of the lock mechanism10A is provided with certainty.

As described above, by automatically locking the output rings32, the spindle3is locked. In a consequence, the detachment of the chuck4(FIG. 1) and the manual operations of the electric tool can be performed easily. The loose engagement portions34care formed with a play angle with respect to the oblong connection section3d. Owing to such a structure, even if the spindle3is rotated by the relative rotation of the output rings32and the like, the float gears34are prevented from interfering with the relative rotation of the spindle3.

Next, the functions and effects of the rotation output device10including the lock mechanism10A having the above structure will be described. As described above, the rotation output device10in this embodiment includes the output gear31for inputting a rotation driving force; the spindle3located coaxially with the output gear31for receiving the driving force from the output gear with the predetermined play angle α and outputting a rotation force; the lock ring33provided around an outer circumferential surface of the spindle3and is restricted from rotating; the output rings32fixed to the spindle3for rotating integrally with the spindle3; the click spring38fixed to the spindle3for rotating the output rings32with respect to the output gear31; the float gears34which are held by the output ring32to be urged radially outward, and fixedly engageable with the lock ring33; the central pin insertion through-holes32eand the side pin insertion through-holes32gprovided in the output rings32for releasing the float gears34radially outward and fixedly engaging the float gears34with the lock ring33; and pin insertion holes31cprovided in the output gear31for guiding the float gears34radially inward and releasing the float gears34from the fixed engagement with the lock ring33by the rotation of the motor M. The click spring38relatively rotates the output rings32by the stoppage of the rotation driving of the output gear31.

According to the above-described structure, the click spring38rotates the output rings32with respect to the output gear31by the stoppage of the rotation driving of the output gear31. Therefore, the central pin insertion through-holes32eprovided in the output rings32release the float gears34radially outward and fixedly engage the float gears34with the lock ring33. Thus, the lock mechanism10A can be automatically placed into a lock state.

By the rotation of the output gear31, the pin insertion holes31cprovided in the output gear31guide the float gears34radially inward and release the float gears34from the fixed engagement with the lock ring33. Thus, the lock mechanism10A can be automatically released from the lock state.

When the rotation driving of the output gear31is stopped, the click spring38rotates the output rings32with respect to the output gear31in the direction in which the output gear31has been rotated. Therefore, the change in the relative positions of the pin insertion holes31cand the central pin insertion through-holes32eby the relative rotation of the output gear31for releasing the lock mechanism10A from the lock state can be reduced. As a result, the float gears34can be released radially outward and fixedly engaged with the lock ring33with certainty, and thus the lock mechanism10A can be placed into a lock state.

The click spring38rotates the output rings32with respect to the output gear31by an angle corresponding to the play angle α. Therefore, the change in the relative positions of the pin insertion holes31cand the central pin insertion through-holes32eby the relative rotation of the output gear31for releasing the lock mechanism10A from the lock state can be eliminated. As a result, the float gears34can be released radially outward and fixedly engaged with the lock ring33with further certainty, and thus the lock mechanism10A can be placed into a lock state. Since the float gears34can be engaged with the lock ring33without loosely engaging the float gears34with the pin insertion holes31or the central pin insertion through-holes32e, a lock mechanism with no play can be provided.

Two sets of the engagement groove31dand the hook38care provided so as to be opposed to each other with the center interposed therebetween. As compared to a structure having one set of the engagement groove31dand the hook38c, the force for rotating the output rings32with respect to the output gear31can be increased. Thus, the output rings32can be rotated with respect to the output gear31with certainty.

The engagement grooves31dand the hooks38care formed so as to have substantially the same arc-shape. Therefore, the rotation of the output rings32with respect to the output gear31can be smoothly caused by the arc-shape of the engagement grooves31dand the hooks38c. Thus, the output rings32can be rotated with respect to the output gear31with further certainty.

The hooks38care engageable with the arc-shaped engagement grooves31dby an elastic force. Therefore, as compared to, for example, a structure in which the hooks38care engaged with the engagement grooves31dby a driving force from a separate driving source, the number of parts and components can be reduced and the assembly thereof is easier. In the case where the hooks38care engageable with the arc-shaped engagement grooves31dby an elastic force, the structure of the rotation output device10, especially the structure of the lock mechanism10, is relatively simple. Therefore, the possibility of the reliability, durability or the like of the lock mechanism10itself being deteriorated can be lowered.

The loose engagement portions34care formed between the float gears34and the spindle3. Therefore, when the position of the float gears34in the rotation direction is maintained by the delay plate37, the rotation of the spindle3is not transmitted to the float gears34.

Therefore, the float gears34can be certainly prevented from rotating by an angle corresponding to the “loose engagement portions34c”together with the spindle3, and thus the float gears34can be certainly prevented from rotating together with the spindle3. Accordingly, even when the output gear31and the spindle3are rotated together with no play angle α, the float gears34are not rotated. As a result, the relative positions of the float gears34and the output gear31change with certainty, which provides the lock function.

The central pin insertion through-holes32eand/or the side pin insertion through-holes32gare formed in the output rings32, and the stoppage pins34gand/or the stoppage projections34hengageable with the central pin insertion through-holes32eand/or the side pin insertion through-holes32gare formed in the float gears34. Therefore, the stoppage pins34gand/or the stoppage projections34hof the float gears34are engaged with the central pin insertion through-holes32eand/or the side pin insertion through-holes32gof the output rings32. Thus, the lock mechanism10A performs the locking operation.

Therefore, the output rings32and the float gears34are engaged with each other at a plurality positions, which improves the rigidity at the plurality of positions and thus improves the lock torque in the lock state. As a result, the lock torque by the float gears34in the lock state is improved, which provides a more certain and stable lock function.

The thickness of the parts of the output rings32around the shaft insertion holes32dis made greater than the remaining parts of the output rings32. Therefore, the area of the output rings32which receives the pressure from the spindle3can be enlarged.

Accordingly, the output rings32can receive the rotation torque from the spindle3with certainty while the output rings32are made thinner. Thus, the output rings32can receive the rotation torque from the spindle3with certainty and thus the lock torque can be improved, while the output rings32are formed to be compact.

The delay plate37for restricting the positional change of the float gears34is interposed between the float gears34and the lock ring33, and the delay plate37is rotated integrally with the float gears34such that the outer end of the delay plate37contacts the lock ring33. Therefore, the delay plate37does not slide along the float gears34while being in contact therewith. This prevents the delay plate37from adversely influencing the locking or releasing operation of the float gears34.

Thus, even though the delay plate37is provided, the locking function of the float gears34can be stably provided with no undesirable possibility of being inhibited. The positional change of the float gears34is restricted by the delay plate37. Therefore, the float gears34, which are in the release state, are prevented from being placed into the lock state by an external force other than the rotation driving force of the output gear31.

The legged O-ring36for increasing a sliding resistance is provided at the position where the delay plate37contacts the lock ring33. As a result, the delay plate37contacts the lock ring33with a higher sliding resistance. This makes the delay plate37more easily influenced by the restriction on the rotation of the lock ring33. As a result, the position of the delay plate37in the rotation direction is maintained with certainty, and the position of the float gears34in the rotation direction is maintained certainly by the delay plate37.

The legged O-ring36is formed of an elastic rubber or resin material. This allows the delay plate37and the lock ring33to contact each other constantly. Namely, since the relative positional offset between the delay plate37and the lock ring33is absorbed by the legged O-ring36, the delay plate37and the lock ring33can be in contact with each other constantly. Therefore, the position of the float gears34in the rotation direction is maintained constantly and certainly by the delay plate37.

Two float gears34are provided in the circumference direction and set to rotate integrally with the delay plate37. Owing to this structure, the lock torque can be increased.

Since the two float gears34are set to be rotated integrally with each other by one delay plate37, the two float gears34are provided with a completely equal force of maintaining the position thereof in the rotation direction. Accordingly, the positions of the float gears34in the rotation direction are not separately maintained. Even in the case where two float gears34are provided, the positions thereof in the rotation direction can be constantly maintained in synchronization with each other.

The rotation output device10according to the present invention can be provided in any device requiring a rotation output, as well as an output system of an electric tool. Thus, the present invention significantly facilitates the operation of locking an electric tool or the like.

In this embodiment, the rotation output device10is provided in the output system of the electric tool. The rotation output device10according to the present invention is usable in any device requiring a rotation output.

In this embodiment, the output gear31has the engagement grooves31dand the click spring38has hooks38c. Alternatively, the click spring38may have the engagement grooves31dand the output gear31may have the hooks38c. In this embodiment, the click spring38is provided between the output gear31as an input element and the spindle3as an output element. Alternatively, the click spring38may be provided between the lock ring33which is a fixing element and the spindle3as an output element.

The elements of the present invention and the elements in the above-described embodiment correspond as follows.

The rotation input body of the present invention corresponds to the output gear31;

the rotation output body corresponds to the spindle3;

the release operation groove corresponds to the pin insertion holes31c;

the arc-shaped groove corresponds to the engagement grooves31d;

the guide holding plate corresponds to the output rings32;

the fixing part corresponds to the shaft insertion hole32d;

the lock operation groove corresponds to the central pin insertion through-holes32eand the side pin insertion through-holes32g;

the fixing member corresponds to the lock ring33;

the engagement hole corresponds to the insertion recesses33d;

the movement locking plate corresponds to the float gears34;

the escaping portion corresponds to the loosely engagement portions34c;

the engagement projection corresponds to the stoppage pins34gand the stoppage projections34h;

the sliding resistance increasing means corresponds to the legged O-ring36;

the restriction plate corresponds to the delay plate37; and

the arc-shaped claw corresponds to the hooks38c.

However, the present invention is not limited to the above-described embodiment.