# Patent

## Title
Power rotary tool and impact power tool

## Abstract

A rotary power tool, such as an oil pulse driver, includes: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, an internal gear that meshes with the planet gears and a shaft that is rotationally driven by the planet gears and disposed frontward of the planet gears. The internal gear comprises an internal gear part and an internal gear retaining part for holding the internal gear part. An oil unit bearing is disposed frontward of the internal gear part, and the oil unit bearing is held at a front part of the internal gear retaining part.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No. 2013-123935, Japanese Patent Application No. 2013-123936 and Japanese Patent Application No. 2013-123937, all filed on Jun. 12, 2013, the contents of all of which are fully incorporated herein by reference.
TECHNICAL FIELD
The present disclosure is directed to a rotary power tool that includes an electric motor for rotating a tool bit or a similar accessory and to an impact tool configured to impart an impulse to a tool bit or a similar accessory.
BACKGROUND ART
Japanese Laid-Open Patent Publication No. 2008-44080 discloses a hydraulic torque wrench that includes a power transmitting apparatus. The power transmitting apparatus comprises a cylinder filled with hydraulic oil. The cylinder is located inside an outer casing part and is rotated by a drive motor via a rear-side planetary gear mechanism. A bearing that rotatably supports the cylinder is disposed between a small diameter portion of a rear part of the cylinder and the outer casing part, and an internal gear of the planetary gear mechanism is disposed on the rear side of the bearing.
The outer casing part of this device is formed of metal and further comprises: a housing that houses the motor, an outer wall of the planetary gear mechanism disposed on the front side of the housing, and a case of the cylinder disposed on the front side of the outer wall.
SUMMARY
In the above-described known hydraulic torque wrench, the small diameter part of the cylinder overlaps the bearing in the circumferential direction, and therefore the hydraulic torque wrench is made somewhat compact in the front and rear direction. However, it would be useful if such a hydraulic torque wrench or other power tool driven via a planetary gear mechanism could be made even more compact.
Therefore, a first principal feature of the present disclosure is to provide a rotary power tool that is much more compact than conventional rotary power tools.
In addition, in the conventional hydraulic torque wrench discussed above, the outer casing part is formed of metal and is therefore very strong. Nonetheless, metal can be difficult to fabricate and to combine with internal members/components, and this increases the cost of the power tool. Furthermore, metal is relatively heavy and increases the weight of the power tool. Reducing the amount of metal in a power tool can be beneficial and may improve the ease of handling of the power tool.
Therefore, a second principal feature of the present disclosure is to provide a rotary power tool that is easier to form and to handle.
In the conventional hydraulic torque wrench discussed above, the components of the outer casing part of the body are arranged in the following order: the case of the cylinder, the outer wall of the planetary gear mechanism, and the housing of the motor. There is room to make the case, the planetary gear mechanism, and the housing more compact and to improve their strength. In addition, sometimes the outer casing part of the body is subjected to external shocks, e.g., from contacting another object, and it is therefore desirable to provide protection for the outer casing part and members/components contained therein.
Therefore, a third principal feature of the present disclosure is to provide an impact tool that is much more compact than conventional tools, that exhibits greater strength than conventional tools, and that provides increased protection for internal elements/components of the tool.
In a first aspect of the disclosure, a rotary power tool comprises: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, an internal gear that meshes with the planet gears, and an output part that is rotationally driven by the planet gears and that is disposed frontward of the planet gears. The internal gear comprises an internal gear part and an internal gear retaining part for holding the internal gear part. A bearing is disposed frontward of the internal gear part, and the bearing is held at a front part of the internal gear retaining part.
In a second aspect of the disclosure, a rotary power tool comprises: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, an internal gear that meshes with the planet gears, and an output part that is rotationally driven by the planet gears and that is disposed frontward of the planet gears. The internal gear comprises an internal gear member and an internal gear retaining member for holding the internal gear member. A bearing is disposed frontward of the internal gear member, and the bearing is held at a front part of the internal gear retaining member.
In a third aspect of the disclosure, a rotary power tool comprises: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, an internal gear that meshes with the planet gears, pins that hold the planet gears, a carrier that holds the pins, and an output part rotationally driven by the carrier and disposed frontward of the planet gears. The carrier is disposed on the inner circumferential side of the internal gear.
In a fourth aspect of the disclosure, a rotary power tool comprises: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, and an internal gear that meshes with the planet gears. The internal gear comprises an internal gear part and an internal gear retaining part for holding the internal gear part, and the internal gear retaining part holds a first bearing and a second bearing. A closed space is formed by the first bearing and the second bearing.
In a fifth aspect of the disclosure, a rotary power tool comprises: a motor, a pinion rotated by the motor, planet gears that mesh with the pinion, and an internal gear that meshes with the planet gears. The internal gear comprises an internal gear member and an internal gear retaining member for holding the internal gear member, and the internal gear retaining member holds a first bearing and a second bearing. A closed space is formed by the first bearing and the second bearing.
In a sixth aspect of the disclosure, a rotary power tool comprises: a motor, a speed reducing gear part that is driven by the motor, an output part that is connected to the speed reducing gear part and is rotationally driven by the speed reducing gear part, and a case that houses the speed reducing gear part. The case is formed of resin.
In a seventh aspect of the disclosure, a cover is provided at the outer circumference of the case.
In an eighth aspect of the disclosure, for embodiments that include a housing for housing the motor, a mating part is provided on the housing, a mated part is provided on the case, and the mating part and the mated part are mated to one another.
In a ninth aspect of the disclosure, a damper is held by the cover.
In a tenth aspect of the disclosure, the output part is connected to an oil unit that is configured to generate impact torque.
In an eleventh aspect of the disclosure, in embodiments in which a housing that houses the motor is provided, the case is screwed to the housing.
In a twelfth aspect of the disclosure, in embodiments in which a housing that houses the motor is provided, an impact mechanism part is disposed inside the case.
In a thirteenth aspect of the disclosure, the case is stopped (blocked/limited) from coming off (being displaced) frontward and from rotating clockwise or counterclockwise by a frontward separation stop part of the housing. The speed reducing gear part is stopped (blocked/limited) from coming off (being displaced) rearward by a rear separation stop part of the housing.
In a fourteenth aspect of the disclosure, a hole is provided in the cover for fixing the damper, and the hole is located adjacent to an engaging part that stops (blocks/limits) the cover from rotating.
In a fifteenth aspect of the disclosure, an impact tool comprises: a motor, a housing that houses the motor, an impact mechanism part driven by the motor, a case that houses the impact mechanism part and that is connected to the housing, and a cover that covers the case and that is held by the housing.
In a sixteenth aspect of the disclosure, the housing comprises a right housing portion and a left housing portion, and the cover is interposed between the right housing portion and the left housing portion.
In a seventeenth aspect of the disclosure, the cover is held by the housing by being interposed between the right housing portion and the left housing portion when the cover is held at the outer circumference of the case.
In an eighteenth aspect of the disclosure, connecting parts of the case and the housing are disposed rearward of retaining parts of the housing and the cover.
In a nineteenth aspect of the disclosure, a circumferential surface of the case is connected to an inner surface of the housing, and the inner surface of the housing holds a lower part of the case.
In a twentieth aspect of the disclosure, at least a portion of the cover is disposed on the inner side of the housing, and at least a portion of the case is disposed on the inner side of the cover.
In a twenty-first aspect of the disclosure, a ventilation path is provided between the cover and the case.
In a twenty-second aspect of the disclosure, the ventilation path is provided between the cover and the housing.
In a twenty-third aspect of the disclosure, the cover is held between a light and the case.
These and other features and aspects of the present disclosure help make rotary power tools more compact and easier to manufacture and operate than conventional rotary power tools. These features and aspects of the disclosure also help make impact tools stronger and more compact than conventional power tools and provide improved protection for internal components thereof.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a left side elevational view of an impact driver according to an embodiment of the present disclosure.
FIG. 2 is a front elevational view of the impact driver of FIG. 1.
FIG. 3 is a center longitudinal cross sectional view of the impact driver of FIG. 1.
FIG. 4 is a partial enlarged view of a main body part of the impact driver illustrated in FIG. 3.
FIG. 5 is a transverse cross sectional view of the impact driver of FIG. 1.
FIG. 6 is a cross sectional view taken along line A-A in FIG. 3.
FIG. 7 is a cross sectional view taken along line B-B in FIG. 3.



DETAILED DESCRIPTION
Embodiments and modified examples thereof of the present disclosure are explained below, referencing the drawings where appropriate.
FIG. 1 illustrates a rechargeable oil pulse driver 1, which is one example of a rotary power tool or an impact tool according to aspects of the disclosure. The oil pulse driver 1 comprises an outer wall housing 2 that forms an outer wall of the oil pulse driver 1. It is noted that, in FIG. 1, the left side of the Figure corresponds to the front of the oil pulse driver 1. The oil pulse driver 1 further comprises a tubular main body part 4, the central axis of which is oriented in the front and rear direction, and a grip part 6 formed such that it protrudes from a lower part of the main body part 4.
The grip part 6 is the portion of the oil pulse driver 1 that is intended to be gripped by a user. An upper part of the grip part 6 is provided with a trigger type switch lever (trigger switch) 8 that can be operated by pulling on it with a user's fingertip. The switch lever 8 protrudes from a switch main body part 8a. 
The main body part 4 of the oil pulse driver 1 houses, coaxially arranged in order from the rear side: a motor 10, a planetary gear mechanism 12 that serves as a speed reducing gear part, an oil unit 13 that serves as an impact mechanism part, and a shaft 14 that serves as an output part.
The motor 10 is the drive source of the oil pulse driver 1, and the rotational speed of the motor 10 is reduced by the planetary gear mechanism 12. The rotation is transmitted to the oil unit 13, which applies an appropriate impulse to the rotation, and to the shaft 14. The shaft 14 is a structure that receives the rotational impact force and rotates around its axis.
The outer wall housing 2 comprises: a motor housing 20 (a housing), which extends from a rear part of the main body part 4 to the grip part 6, a unit case 22 disposed frontward of an upper part of the motor housing 20, a cover 24, and a damper 26.
The motor housing 20 comprises a half-split tubular (i.e. clam shell housing halves) left motor housing 20a (a left housing or left housing portion) and a right motor housing 20b (a right housing or right housing portion). The left motor housing 20a and the right motor housing 20b are fixed to one another by screws 28 (refer to FIG. 3 and FIG. 4). The motor housing 20 in the main body part 4 houses the motor 10.
On the front side of the upper part of the motor housing 20 (at a front lower part of the main body part 4) are formed: a light retaining upper housing 20f, disposed on the upper side of a light 32 (discussed later), and a light retaining lower housing 20h, disposed on the lower side of the light 32.
The unit case 22 (a case) is made of resin, and, more specifically, is made of a synthetic resin. The unit case 22 has a tubular shape (a circular cylindrical shape), and the diameter of a front part of the unit case 22 is smaller than the diameter of a rear part of the unit case 22.
The rear part of the unit case 22 is inserted into a front part of the motor housing 20 and is connected to the motor housing 20. The front part of the motor housing 20 is open and has a tubular shape (a circular cylindrical shape).
Unit case ribs 22a protrude outwardly from the rear part of the unit case 22, while unit case mounting ribs 20c protrude inwardly from the motor housing 20 in front of or behind the unit case ribs 22a on the inner side of the front part of the motor housing 20. In addition, a step part 20d is disposed frontward of the front unit case mounting rib 20c by a gap or groove in the motor housing inner wall that is equal to the thickness of the unit case rib 22a. The step part 20d is formed such that its rear side widens outward in the radial direction with respect to its front side, and its rear side inner diameter is enlarged (e.g., at the gap or groove) with respect to its front side inner diameter. Furthermore, a rib 20e protrudes inwardly from the motor housing 20 at a location rearward of the rear unit case mounting rib 20c and defines a gap equal to the thickness of the rear unit case rib 22a. 
The unit case mounting ribs 20c are disposed in front of or behind the unit case ribs 22a. The front unit case rib 22a (i.e., a mated part) fits in the gap or groove (i.e., a mating part) in the motor housing 20 between the front unit case mounting rib 20c and the step part 20d. The rear unit case rib 22a (i.e., a mated part) fits in the gap or groove (i.e., a mating part) in the motor housing 20 between the rear unit case mounting rib 20c and the rib 20e. By fitting the unit case ribs 22a on the front side or the rear side of the unit case mounting ribs 20c, the unit case 22 is fixed so that a portion of the unit case 22 extends frontward of the motor housing 20. Furthermore, the mating parts and/or the mated parts constitute connecting parts of the unit case 22 and the motor housing 20. In addition, the mating parts and/or the mated parts are also one of the frontward separation stop parts that prevent, for example, the unit case 22 from coming off frontward (i.e., separating from the motor housing 20), the unit case 22 from rotating clockwise or counterclockwise with respect to the motor housing 20, etc.
A step part 20i is formed on an inner side of a front end opening of the motor housing 20. The rear side diameter of the step part 20i is larger than the front side diameter of the step part 20i. In addition, a step part 22d is provided on a side surface of the unit case 22 at a location adjacent to the step part 20i. The rear side diameter of the step part 22d is larger than the front side diameter of the step part 20i. The sizes of the step parts 20i, 22d are equal, and combining them stops (blocks/limits) the unit case 22 from coming off (being displaced) frontward and prevents the unit case 22 from rotating clockwise or counterclockwise (i.e., a separate one of the frontward separation stop parts).
Air intake holes 22c are provided on the left and right of a center part of the unit case 22 (refer to FIG. 5).
The unit case 22 houses the planetary gear mechanism 12 (other than a rear end part thereof) and the oil unit 13, and other elements. In addition, a front part of the planetary gear mechanism 12 and a rear part of the oil unit 13 are disposed inwardly of the overlapped portion of motor housing 20 and the unit case 22.
A lower rear part of the unit case 22 is provided with a recessed part 22e which drops further downward (extends further outward) with respect to a longitudinal center line of the unit case 22 than other portions of the unit case 22. Inwardly-oriented damper holes 22f are formed to the left and right of the recessed part 22e in the unit case 22 (refer to FIG. 6). Outwardly extending projections 22g are formed on the lower sides of the resin damper holes 22f (refer to FIG. 6).
A left sandwiching part 20j of an inner wall of the left motor housing 20a makes contact with the outer side of the left projection 22g. A right sandwiching part 20k of an inner wall of the right motor housing 20b makes contact with the outer side of the right projection 22g, and the lower rear part of the unit case 22 is interposed between the left sandwiching part 20j and the right sandwiching part 20k (refer to FIG. 6).
The cover 24 is tubular (circular cylindrical shaped), and the diameter of a front part of the cover 25 is less than the diameter of a rear part of the cover 24. Outwardly-protruding damper retaining ribs 24a are provided above and below the front part of the cover 24. Slit shaped holes 24d for fixing the damper 26 to the unit case 22 are formed on the rear sides of the damper retaining ribs 24a. 
A lower part of the cover 24 is hollowed out at the upper side of the switch lever 8 in the motor housing 20 so that it avoids that portion, and a rear end of the lower part of the cover 24 is frontward of a rear end of an upper part of the cover 24. A rear end surface (lower end surface) of the lower part of the cover 24 is continuous with an upper surface of the light retaining upper housing 20f of the motor housing 20 and is supported by that upper surface. In other words, the cover 24 is held by the motor housing 20. In addition, the lower part of the cover 24 is interposed between the left motor housing 20a and the right motor housing 20b. The light retaining upper housing 20f of the motor housing 20 is disposed rearward of the connecting parts, i.e., rearward of the unit case mounting ribs 20c, the step part 20d, the rib 20e, and the unit case ribs 22a, of the unit case 22 and the motor housing 20. The lower part of the cover 24 is held between the light 32 and the unit case 22.
The cover 24 is located at the outer side of a front part of the unit case 22, namely, the cover 24 is provided on an outer circumference of the unit case 22. The cover 24 is held on the outer circumference of the unit case 22 and covers the unit case 22. The unit case 22 is partially enclosed by the cover 24, and a front end part of the unit case 22 protrudes through and frontward of a front end of the cover 24, such that a center portion of the unit case 22 is disposed inside the cover 24.
In addition, a circumferential surface of a front part of a lower part of the unit case 22 is connected to an inner surface of the light retaining upper housing 20f of a lower part of the motor housing 20. The inner surface of the light retaining upper housing 20f of the motor housing 20 holds the lower part of the unit case 22 and, in addition to playing a role in holding the light 32, also plays a role as one of retaining parts that hold the unit case 22. Furthermore, a rear end portion of the lower part of the cover 24 is disposed on the inner side of the light retaining upper housing 20f. 
Moreover, the circumferential surface of the rear part of the lower part of the unit case 22 is held by left and right unit case retaining ribs 20g (separate ones of the retaining parts that hold the unit case 22). Each of the unit case retaining ribs 20g is provided horizontally such that it protrudes inwardly from inner surfaces of the left motor housing 20a or the right motor housing 20b. 
A groove shaped engaging part 24c having a shape that corresponds to the shape of an upper part of the light retaining upper housing 20f is formed in the lower part of the cover 24. The engagement of the engaging part 24c and the light retaining upper housing 20f stops (blocks/limits) the cover 24 from coming off (being displaced) and from rotating clockwise or counterclockwise (i.e., a rotation stop part; refer to FIG. 3 and FIG. 4). The lower hole 24d is located adjacent to the engaging part 24c. 
In addition, protruding parts 24b are formed on the left and right of the cover 24 such that they bulge outward from the remaining portion of the cover 24. Gaps 25 are formed between inner surfaces of the protruding parts 24b and an outer surface of the unit case 22. The air intake holes 22c of the unit case 22 are disposed inwardly of each of the protruding parts 24b, and each of the air intake holes 22c faces its corresponding gap 25.
Furthermore, slit-shaped front intake ports 27 are formed between a front end part of the upper part of the motor housing 20 and a rear end part of the cover 24 (the interface between the motor housing 20 and the unit case 22 on the left and right of a front part of the main body part 4). The protruding parts 24b of the cover 24 are disposed frontward of the front intake ports 27.
This arrangement provides a ventilation path W0 on the left side of the main body part 4 that provides ventilation (cooling air) between the cover 24 and the left motor housing 20a via the front intake ports 27. In addition, a ventilation path W1 is formed by the gaps 25 (the inner sides of the protruding parts 24b) on the left side of the main body part 4 that extends from the ventilation path W0 to the near side (the air intake holes 22c) inside the unit case 22. The ventilation path W1 is formed between an inner surface of the cover 24 and the outer surface of the unit case 22. The path from the ventilation path W0 to the ventilation path W1 is continuous, and it is possible for air to pass from the outside to the nearside inside the unit case 22. Moreover, the ventilation paths W0, W1 are also formed on the right of the main body part 4.
Furthermore, a gap 29 is formed between an inner surface of the unit case 22 and an outer surface of the oil unit 13, and a ventilation path W2 is formed by the air intake holes 22c and the gap 29. The ventilation path W2 is in fluid connection with the ventilation path W1 via the air intake holes 22c. 
In addition, a gap is formed between the recessed part 22e of the unit case 22 and the planetary gear mechanism 12 (a lower part outer surface of an internal gear 72, which is discussed below), and this forms a ventilation path W3. The ventilation path W3 passes through the ventilation path W2.
The damper 26 is ring-shaped and elastic and has grooves 26a that are shaped to correspond to the damper retaining ribs 24a above and below the inner side of the damper 26. The damper 26 overlies the outer side of the front end part of the unit case 22 that projects beyond the cover 24. In addition, each of the grooves 26a of the damper 26 accepts a corresponding one of the damper retaining ribs 24a, and in this manner the damper 26 is held by the cover 24. Furthermore, the front end part of the unit case 22 also sticks out (protrudes) frontward slightly from a front end of the damper 26.
If a phosphorescent material is incorporated into the damper 26, the damper 26 will exhibit luminescence and be capable of emitting light in a dark location.
The unit case 22, the cover 24, the damper 26, and the lower side of the front part of the motor housing 20 (the light retaining upper housing 20f, the light retaining lower housing 20h, and extending to the peripheral parts thereof) constitute the outer wall of the front part of the main body part 4.
A forward/reverse switching lever 30, which is a switch that switches the rotational direction of the motor 10, is provided rearward of the switch lever 8 (i.e., on the upper side of the switch main body part 8a) and inside the lower part (i.e., the grip part 6) of the motor housing 20 such that it passes laterally through a boundary area between the main body part 4 and the grip part 6.
In addition, the light 32 is capable of illuminating the area in front of the oil pulse driver 1, and is provided on the upper side of the switch lever 8, frontward of the forward/reverse switching lever 30. The light retaining upper housing 20f of the motor housing 20 is disposed on the upper side of the light 32, and the light 32 is housed between the light retaining upper housing 20f and the light retaining lower housing 20h. 
The light 32 is preferably an LED and is arranged such that it overlaps the switch lever 8 in the up-down (vertical) direction. Because the light 32 overlaps the switch lever 8 in the up-down direction, the user's finger will generally not get in the way of (block) the light 32 during use of the oil pulse driver 1. This helps provide satisfactory visibility when the light 32 is illuminated. Furthermore, a recessed part (not shown) for holding lead wires of the light 32 is formed in the unit case 22.
A lower end part of the grip part 6 forms a battery mounting part 34 that extends principally frontward with respect to its upper part, and a battery 37 is held below the battery mounting part 34. The battery 37 is attachable and detachable to the battery mounting part 34 via a slider 36 for moving a hook 35 up and down. In the present embodiment, the battery 37 is a 14.4 V (volts) lithium ion battery pack.
A control circuit board 38 is disposed inside the battery mounting part 34. The control circuit board 38 is housed in a circuit board case 39 that has a flat box shape and is made of resin. The circuit board case 39 is fixed inside the battery mounting part 34 (between a lower end part of the left motor housing 20a and a lower end part of the right motor housing 20b). Six switching devices (not shown) are provided which correspond to below-described drive coils 48 for switching corresponding coils 48, and the switching devices and a microcontroller (not shown) are installed onboard the control circuit board 38. The microcontroller controls the switching devices. Furthermore, the switching devices may be installed on a sensor circuit board 44 described below.
The motor 10 is a brushless DC motor and comprises a stator 40, a rotor 42, and the sensor circuit board 44.
The stator 40 comprises a plurality of (six) coils 48 that are wound around a stator core 45 via a front insulating member 46 and a rear insulating member 47. In addition, a total of six coil connection parts (not shown) are provided on a circumferential edge of a front surface of the front insulating member 46. The coil connection parts serve as contacts that electrically connect the sensor circuit board 44 with each of the drive coils 48.
The rotor 42 comprises: a rotor shaft 50 that serves as a rotational axis, a tubular rotor core 51 fixed at the circumference of the rotor shaft 50, and permanent magnets 52 disposed at the circumference of the rotor core 51. The permanent magnets 52 are tubular, and their polarities alternate in the circumferential directions. The rotor core 51, the permanent magnets 52, and the like are disposed on the inner side of the stator core 45. Furthermore, a plurality of sensor permanent magnets (not shown) is disposed radially on the front side of the rotor 42 (on the sensor circuit board 44 side). In addition, the rotor core 51, the permanent magnets 52, and the sensor permanent magnets are assembled together (i.e., as a rotor assembly).
The sensor circuit board 44 is electrically connected by lead wires (not shown) to each of the coils 48 and is also connected to the terminal parts (i.e., the battery 37) of the battery mounting part 34 and to the control circuit board 38. The sensor circuit board 44 controls the rotation of the rotor 42 by controlling the energization state in each of the coils 48. Three magnetic sensors (not shown) are fixed to a rear surface of the sensor circuit board 44. The sensor circuit board 44 is attached to the front side of the front insulating member 46 by screws 54.
A tubular resin sleeve 55 is provided on the front side of the rotor core 51 in the rotor shaft 50. A front bearing 56 of the rotor shaft 50 is provided frontward of the resin sleeve 55. In addition, a pinion 57 is fixed to a front end part of the rotor shaft 50 and frontward of the bearing 56.
A cooling fan 60 is attached to a rear part of the rotor shaft 50 via a metal insert bushing 59. The insert bushing 59 is press fitted and therefore is firmly secured to the rotor shaft 50 of the cooling fan 60. The bearing 56 is disposed along a straight line that connects the center of the screw 28 in the center of an upper part of the main body part 4 and the screw 28 in the center of the lower part of the main body part 4. This effectively reduces vibrations of the rotor shaft 50.
Exhaust ports 61, which comprise a plurality of small holes, are formed in the motor housing 20 radially outwardly of the cooling fan 60. In addition, intake ports 62, which also comprise a plurality of small holes, are formed in the motor housing 20 radially outwardly of the front insulating member 46, the sensor circuit board 44, and the like. When the cooling fan 60 rotates with the rotor shaft 50, external air is drawn into the motor housing 20 via the intake ports 62, transits the various members of the motor 10, and is discharged via the exhaust ports 61.
A rear bearing 64 of the rotor shaft 50 is provided on the circumference of the rear end part of the rotor shaft 50. The bearing 64 is fixed on an inner side of an upper rear end part of the motor housing 20 so that it is interposed between the left motor housing 20a and the right motor housing 20b. 
The planetary gear mechanism 12 is disposed around the front end part of the rotor shaft 50, the pinion 57, and the like. The planetary gear mechanism 12 comprises: an internal gear 72, which in turn comprises an internal gear part 72c, a plurality of planet gears 74 that comprise outer gear parts 74a that mesh with the internal gear part 72c of the internal gear 72, pins 76 that are axes of the planet gears 74, and a carrier 77.
The internal gear 72 comprises a cup-shaped internal gear retaining part 72a, which is open frontward. The internal gear retaining part 72a comprises a bearing retaining part 72b disposed at a rear part thereof and that protrudes rearward and has a circular cylindrical shape. In addition, the internal gear part 72c is provided at the rear part of a circular cylindrical inner surface of the internal gear retaining part 72a and is spaced inwardly from the front part of the internal gear retaining part 72a. The internal gear part 72c forms an internal gear that meshes with the planet gears 74, and the internal gear part 72c is held by the internal gear retaining part 72a. In addition, a bearing retaining part 72d is formed in the front part of the circularly cylindrical inner surface of the internal gear retaining part 72a (on the inner side of the opening of the internal gear retaining part 72a). The bearing retaining part 72d is recessed more toward the outer side than toward the base of the internal gear in the internal gear part 72c, and its diameter is greater than that of the rear part of the circular cylindrical inner surface of the internal gear retaining part 72a. 
As shown in FIG. 7 in particular, there is a bearing retaining part 72b at the rear part of the internal gear retaining part 72a, at the center viewed from the rear, and ribs 72e extend (protrude) upward, downward, leftward, and rightward from the bearing retaining part 72b. The inside of the bearing retaining part 72b includes a hole oriented in the front and rear directions that passes through to the interior of the internal gear part 72c. A tip part of the rotor shaft 50, a rear part of the pinion 57, and the like are disposed in that hole. In addition, the front bearing 56 of the rotor shaft 50 is held inside a rear part of that hole (on the inner side of the opening) in the bearing retaining part 72b. 
The bearing retaining part 72b, the ribs 72e and the like are held by internal gear fixing ribs 78 (rear separation stop parts) that protrude inwardly from the inner surface of the motor housing 20. Each of the internal gear fixing ribs 78 protrudes as far as a position that reaches an outer surface of the bearing retaining part 72b or outer surfaces of the ribs 72e. The internal gear fixing ribs 78 (the front internal gear fixing ribs 78) that reach the internal gear retaining part 72a are formed integrally with the rib 20e for fixing the unit case 22. In addition, ventilation ports 78a (refer to FIG. 3, FIG. 4, and FIG. 7) are formed in the bases of the lower internal gear fixing ribs 78. Because the ventilation ports 78a are capable of facilitating the ventilation, they are also included in the ventilation path W3 outward of the internal gear 72.
The internal gear 72 is stopped (blocked/limited) from rearward movement by the internal gear fixing ribs 78, which internal gear fixing ribs 78 sandwich a side part, the rear part, and the like of the internal gear 72. Tip parts of the internal gear fixing ribs 78 comprise sandwiching parts 78b (refer to FIG. 7).
The rear part of the unit case 22 (the portion on the rear side of the front unit case rib 22a) is interposed between the motor housing 20 (inner surfaces of the mating parts, tip surfaces of the unit case mounting ribs 20c, and the like) and the internal gear 72 (an outer surface of the internal gear retaining part 72a). Moreover, a front end of the internal gear 72 (a front surface of the bearing retaining part 72d of the internal gear retaining part 72a) makes contact with a step part 22b in the inner surface of the unit case 22 (refer to FIG. 5). The step part 22b is formed such that the inner diameter on the rear side thereof is larger than the inner diameter on the front side thereof, and the step part 22b is disposed radially inwardly of the front unit case rib 22a (or of the mating part between the front unit case mounting rib 20c and the step part 20d).
In addition, a ring-shaped (annular) indentation 72f is provided in the inner surface of the internal gear retaining part 72a of the internal gear 72 that recesses rearward with respect to the surrounding surface. If the inner side of the internal gear retaining part 72a is suitably greased in order to ensure lubrication with respect to the planet gears 74, then that grease can be stored in the indentation 72f, thus making it possible to lengthen the time period until the grease runs out and prevent an occurrence of insufficient lubrication. The presence of the ring-shaped indentation 72f also reduces the number of times that the grease must be replenished, thereby improving maintenance properties (making the device easier to maintain). In addition, the location of the indentation 72f makes it possible to expand the surface area of the internal gear 72 more than if the indentation 72f were not present, and this allows for a more efficient dissipation of the heat generated during operation.
The planet gears 74 are provided around the pins 76 so that each of the planet gears 74 is rotatable around its corresponding pin 76. The outer gear part 74a of each of the planet gears 74 meshes with the teeth of the pinion 57.
The plate shaped carrier 77, which extends upward, downward, leftward, and rightward, is disposed on the front sides of the planet gears 74. The carrier 77 rotatably accepts the front parts of the pins 76. A spline hole is formed in the center of the carrier 77. Furthermore, the carrier 77 is disposed on an inner circumferential side (i.e., inwardly in the radial directions) of the internal gear 72.
When the rotor shaft 50 rotates and thereby rotates the pinion 57, each of the planet gears 74 rotates and revolves in accordance with the internal gear part 72c of the internal gear 72. The carrier 77 rotates at a reduced speed via the pins 76 as a result of the revolving of the planet gears 74.
The oil unit 13 comprises: a cup-shaped front oil case 80 that is open rearward, a cup-shaped rear oil case 81 that is open frontward, screws 82, an internally hollow, elastic ring 83, a ring-shaped plate 84 that presses the ring 83 from the rear, a cam 85, balls 86, blades 88, a middle seal ring 90 and a rear seal ring 92, an output adjusting mechanism 94, a seal ring 100, and a ring 102. Furthermore, the rear part of the shaft 14, a shaft bearing 104, a front seal ring 105, and the like can also be considered to be constituent elements of the oil unit 13 in preferred embodiments.
The front oil case 80 comprises a circular cylindrical tubular rib 80a that protrudes rearward from the rear surface of a front part of the front oil case 80. In addition, a step part 80b, whose diameter expands in the direction from the front side to the rear side, is formed in the inner surface of a side part of the front oil case 80.
The ring 83 is located on the outer side of the tubular rib 80a and is disposed on the inner side of a side surface of the front oil case 80. The ring 83 is a ring shaped member that is formed of resin (more specifically, a synthetic resin), and the interior of the ring 83 is filled with a gas 83a (e.g., air).
In addition, the plate 84 is disposed on the rear side of the ring 83, a rear end part of the tubular rib 80a, and the step part 80b. The plate 84 has gap parts 84a at mutually opposing positions (above and below in FIG. 3 and FIG. 4). The periphery of the ring 83 and a rearward portion of the plate 84 communicate with one another via the gap parts 84a. 
Screw holes for the screws 82 are formed in a portion of the front oil case 80 that is located frontward of the gap parts 84a. 
The rear oil case 81 comprises: a circular cylindrical sidewall part 81a, a center part 81b disposed on the rear side of the sidewall part 81a, and a rear part 81c disposed on the rear side of the center part 81b. 
The sidewall part 81a extends into the opening of the rear part of the front oil case 80 and makes contact with the front oil case 80. The middle seal ring 90 and the rear seal ring 92 are disposed between the sidewall part 81a and the front oil case 80.
Raised parts 96 are provided on the inner surface of the sidewall part 81a at positions at which they oppose one another (on the left and right in FIG. 5) and they bulge toward the inner side with respect to the rest of the inner surface (the circular cylindrical surface).
The center part 81b closes up the rear end of the sidewall part 81a. The outer surface of the center part 81b has a circular cylindrical shape and the diameter thereof is smaller than the outer diameter of the sidewall part 81a. That is, a step is formed at the interface between the sidewall part 81a and the center part 81b which step is recessed, wherein its rear diameter is smaller than its front diameter.
An oil unit bearing 97, which rotatably supports the rear oil case 81 (the oil unit 13), is disposed on the outer side of the center part 81b. A rear part of an outer surface part of theoil unit bearing 97 is fitted into the bearing retaining part 72d, and the oil unit bearing 97 is held by the bearing retaining part 72d of the internal gear retaining part 72a in the internal gear 72. An outer raceway of the oil unit bearing 97(first bearing) contacts a step 72g formed on an inner circumferential surface of the bearing retaining part 72d by the internal gear part72c. A closed space is formed in the internal gear 72 by the oil unit bearing 97 (a first bearing), the internal gear retaining part 72a, the front bearing 56 (a second bearing) of the rotor shaft 50, and the rear oil case 81 (the center part 81b and the rear part 81c). Furthermore, the oil unit bearing 97, the bearing 56, and the like are the constituent elements of the outer wall of that closed space.
The rear part 81c has a circular cylindrical shape and protrudes rearward from a rear surface of the center part 81. The diameter of the rear part 81c is smaller than that of the center part 81. The outer diameter of the rear part 81c is equal to the diameter of the spline hole of the carrier 77. A spline groove, which meshes with the spline hole of the carrier 77, is formed in an outer surface of the rear part 81c, and the carrier 77 and the rear part 81c are formed so that they are rotationally interlocked with one another. Furthermore, the rotationally-interlocking structure of the carrier 77 and the rear part 81c may be any kind of structure that prevents relative rotation, such as one that uses a hexagonal hole (a polygonal hole) and a hexagonal column (a polygonal column) instead of the spline structure.
A rear part of the shaft 14 extends into the front oil case 80 and the rear oil case 81. The shaft 14 is connected to the oil unit 13.
The hole in the center of the plate 84 and an inner surface of the tubular rib 80a contact an outer surface of the rear part of the shaft 14. The seal ring 100 and the ring 102 are provided on the front side of the tubular rib 80a so that the seal ring 100 and the ring 102 contact the outer surface of the shaft 14 in the center hole.
The shaft bearing 104, which rotatably supports the shaft 14, is disposed on the front side of the front oil case 80. The shaft bearing 104 is attached on the inner side of the front part of the unit case 22. Furthermore, the front seal ring 105 is disposed on the front side of the shaft bearing 104. The front seal ring 105 makes contact with the outer surface of the shaft 14. The front seal ring 105 is attached on the inner side of the front part of the unit case 22.
A hole is formed inside the shaft 14, which hole is oriented in the front and rear directions and extends over the entirety of the shaft 14. A front part of the hole constitutes a chuck hole 106, in which a tool bit can be mounted. A chuck 108 is provided outward of the chuck hole 106 (at a tip part of the shaft 14). In addition, the output adjusting mechanism 94 is disposed at a center part of that hole (rearward of the chuck hole 106) when the output adjusting mechanism 94 closes up that hole.
A sealed space is formed by the shaft 14, the front oil case 80, the rear oil case 81, the screws 82, the output adjusting mechanism 94, and the various seal rings, and the interior of that sealed space is filled with oil. The filling of the sealed space with the oil is accomplished via the screws 82 in a vacuum drawn state, after which the screws 82 are inserted.
In addition, the oil inside that sealed space is capable of flowing in on the rear side of the ring 83 via the gap parts 84a of the plate 84. The ring 83 is configured to contract due to the pressure imparted by the oil that flows into the space on the rear side of the ring 83 and arrives at a location adjacent to the ring 83. The ring 83 contracts principally by being compressed by the gas 83a and it contracts when the temperature of the oil becomes comparatively high which increases the pressure of the oil.
Furthermore, the cam 85 is disposed in the rear part of the hole inside the shaft 14 (rearward of the output adjusting mechanism 94). The cam 85 has a flat shape (in FIG. 3 and FIG. 4, extends frontward, rearward, upward, and downward) and is configured to rotate clockwise and counterclockwise together with the shaft 14.
The balls 86, which are made of metal (iron or steel), are disposed around the cam 85 (in FIG. 3 and FIG. 4, above and below). Each of the balls 86 is configured to contact the cam 85. Holes for receiving the balls 86 are disposed in the radial directions in the shaft 14. These holes communicate with the hole in the shaft 14 that is oriented in the front and rear directions.
The blades 88 are disposed on the outer side of (in FIG. 3 and FIG. 4, above and below) the balls 86. The blades 88 are configured to simultaneously contact the balls 86 and the inner wall of the rear oil case 81 (the sidewall part 81a). If the raised parts 96 of the sidewall part 81a are located on the left and right, then the cam 85 becomes horizontal as a result of the rotation. When the balls 86 are located on the left and right of the cam 85, the blades 88 contact the left or right raised parts 96. At this time, radial oil through-holes 110 (refer to FIG. 5), which in some configurations communicate with the rear part of the hole, are closed up by the cam 85, the balls 86, 86, and the like. This seals the interior of the rear part of the shaft 14 (a circumferential part of the cam 85), and therefore the internal pressure in that sealed portion increases with respect to the internal pressure of the oil in the remaining portion. As a result of the rise in the internal pressure in the sealed portion, the position of each of the blades 88 (the position at which the blade 88 is pressed toward the outer side by the cam 85, the balls 86, and the like and becomes capable of contacting the raised parts 96) is maintained.
The internal pressure of the oil can be adjusted by the output adjusting mechanism 94. In the output adjusting mechanism 94, the amount of the oil passing through the rear part itself is adjusted by movement of the output adjusting mechanism 94 forward and rearward, and this adjusts the internal pressure of the oil. The output adjusting mechanism 94 is moved forward and rearward by rotating an operating tool that is inserted into the chuck hole 106.
The shaft 14 is connected to the planetary gear mechanism 12 via the oil unit 13 and is rotationally driven by the planetary gear mechanism 12.
An example of the operation of the oil pulse driver 1 of this type will now be explained.
When the user grasps the grip part 6 and pulls the switch lever 8, the switching of the switch main body part 8a causes electrical power to be supplied from the battery 37 to the motor 10. The coils 48 (drive coils) are sequentially switched by the control circuit board 38 based on information from the sensor circuit board 44 and the like, and this causes the rotor shaft 50 to rotate.
The rotation of the rotor shaft 50 rotates the cooling fan 60, which creates a flow of air (a draft) from the front intake ports 27, the intake ports 62, and the like to the exhaust ports 61, thus cooling the internal components and/or mechanisms, such as the motor 10, the oil unit 13, and the like.
In greater detail, the rotation of the cooling fan 60 pushes the circumferential air toward the exhaust ports 61, thereby creating a flow of air or a draft. Furthermore, the air introduced via the intake ports 62 passes through the interior (between the stator 40 and the rotor 42, and the like) and the exterior of the motor 10, and exits from the exhaust ports 61 (in FIG. 1 and FIG. 5, refer to the chain lines in the vicinities of the motor 10 or the intake ports 62 and the exhaust ports 61). The air flow in the motor 10 and at the periphery thereof principally first passes through the outer circumference of the stator core 45 and cools the stator core 45, and then passes over the entire surface of the sensor circuit board 44, which cools the sensor circuit board 44. Continuing on in this manner, the flow of cooling air next passes the rotor core 51, the coils 48, and the inner circumference of the stator core 45, thereby cooling them.
In addition, the air introduced from the front intake ports 27 (the ventilation path W0) transits the gaps 25 (the ventilation path W1), the air intake holes 22c, and the like and flows between (along the ventilation path W2) the inner surface of the unit case 22 and the outer surface of the oil unit 13 (in FIG. 1 and FIG. 5, refer to the chain lines in the vicinities of the front intake ports 27. This air flow further passes between (along the ventilation path W3) an outer surface of the planetary gear mechanism 12 (the internal gear 72) and the inner surface of the unit case 22 (or the inner surface of the motor housing 20) reaches the interior of the motor housing 20, and passes through the ventilation ports 78a formed in the lower internal gear fixing ribs 78 (refer to the chain lines in FIG. 4). This flow of air then merges with the air introduced from the intake ports 62.
In addition, the rotational force of the rotor shaft 50 is transmitted to the planet gears 74 via the pinion 57 and is reduced in speed by the planet gears 74, which revolve while rotating inside the internal gear 72, after which the rotational force is transmitted to the carrier 77 via the pins 76. The carrier 77 causes the rear oil case 81 (and the front oil case 80) of the oil unit 13 to rotate via the rear part 81c of the rear oil case 81.
Each of the blades 88 of the oil unit 13 is normally positioned so that it makes contact with the raised parts 96 of the sidewall part 81a of the rear oil case 81. In this state, the oil through-holes 110 are closed up by the balls 86, the cam 85, and the like, and a high pressure oil sealed space is formed in the circumferential part of the cam 85. The blades 88 are pressed against the raised parts 96 by the high pressure oil, and this maintains the positions of the blades 88. Furthermore, the rotation of the rear oil case 81 is transmitted to the shaft 14 via the blades 88, the balls 86, the cam 85, the oil, and the like, and this rotates a tool bit that is held by the chuck 108, in order to, for example, tighten a screw.
In addition, when the screw has been tightened to a certain extent, the load on the shaft 14 increases. When the rotation of the shaft 14 has become slower than the rotation of the rear oil case 81, an impact torque is generated intermittently by the oil unit 13, as described below, and is imparted (in a pulsed manner) to the shaft 14. That is, the rear oil case 81 and the shaft 14 rotate relative to one another and, once the blades 88 separate from the raised parts 96, the cam 85, the balls 86, and the like open the oil through-holes 110. This opens the oil sealed space around the cam 85, and the balls 86, the blades 88, and the like are drawn toward the inner side in the radial directions. The relative rotation of the rear oil case 81 is then permitted until each of the blades 88 reaches the next raised part 96. Furthermore, when each of the blades 88 contacts its next raised part 96, the oil sealed space around the cam 85 is once again sealed and filled with oil at a comparatively high pressure, the blades 88 are held via the cam 85 and the balls 86 at positions at which they overhang toward the outer side in the radial directions and then contact the raised parts 96. In this manner, the impact torque is transmitted to the shaft 14. The same operation is repeated as appropriate.
The oil unit 13 is capable of generating impact torque, and, by virtue of the impact torque being imparted to the shaft 14, makes it possible to tighten the screw via the tool bit.
Even if, as a result of operation, the temperature of the oil increases and the volume of the oil expands, the hollow ring 83 is pressed by the oil and compresses, thereby suppressing a rise in the internal pressure due to the expanded oil. Fluctuations in the internal pressure caused by fluctuations in the oil temperature are accommodated or absorbed by the ring 83.
The above-mentioned oil pulse driver 1 may comprise: the motor 10, the pinion 57 that is rotated by the motor 10, the planet gears 74 that mesh with the pinion 57, the internal gear 72 that meshes with the planet gears 74, and the shaft 14 that is rotationally driven by and disposed frontward of the planet gear 74. The internal gear 72 comprises the internal gear part 72c and the internal gear retaining part 72a for holding the internal gear part 72c. The oil unit bearing 97 is disposed frontward of the internal gear part 72c, and the oil unit bearing 97 is held at a front part of the internal gear retaining part 72a. 
In this embodiment, the overlap of the internal gear 72 and the oil unit bearing 97 in the radial directions makes it possible to shorten the installation spaces thereof in the front and rear direction to the extent of that overlap and thereby to provide an oil pulse driver 1 that is compact and easy to handle.
In addition or in the alternative, the oil pulse driver 1 may comprise: the motor 10, the pinion 57 that is rotated by the motor 10, the planet gears 74 that mesh with the pinion 57, the internal gear 72 that meshes with the planet gears 74, the pins 76 that hold the planet gears 74, the carrier 77 that holds the pins 76, and the shaft 14 that is rotationally driven by the carrier 77 and is disposed frontward of the planet gear 74. The carrier 77 is disposed on the inner circumferential side of the internal gear 72.
In such an embodiment, fitting the carrier 77 inwardly of the internal gear 72 makes it possible to install the carrier 77 substantially in the installation space of the internal gear 72, thereby making it possible to provide an oil pulse driver 1 that is short in the front and rear direction, compact, and easy to handle.
In addition or in the alternative, the oil pulse driver 1 may comprise: the motor 10, the pinion 57 that is rotated by the motor 10, the planet gears 74 that mesh with the pinion 57, and the internal gear 72 that meshes with the planet gears 74. The internal gear 72 comprises the internal gear part 72c and the internal gear retaining part 72a for holding the internal gear part 72c. The internal gear retaining part 72a holds the oil unit bearing 97 and the front bearing 56 of the rotor shaft 50, and the closed space is formed by the oil unit bearing 97 and the bearing 56.
In such an embodiment, in the internal gear 72, the closed space can be formed by the first bearing, which is installed and utilized to rotate other members, and the second bearing, and these bearings can be provided with multiple functions, which allows for a configuration wherein the part count is reduced and waste is further reduced, making it possible to provide an oil pulse driver 1 that it is compact and lower cost.
In addition or in the alternative, the oil pulse driver 1 may comprise: the motor 10, the planetary gear mechanism 12 that is driven by the motor 10, the shaft 14 that is connected to the planetary gear mechanism 12 and rotationally driven by the planetary gear mechanism 12, and the unit case 22 that houses the planetary gear mechanism 12. The unit case 22 is formed of resin, and this helps make the unit case 22 easy to form and assemble.
In addition or in the alternative the cover 24 may be provided on the outer circumference of the unit case 22. This design would make it possible to protect the unit case 22 and thereby improve durability and, moreover, to make the outer surface of the motor housing 20 and the outer surface of the cover 24 flush with one another, thereby improving the design and handling characteristics.
In addition or in the alternative, in case the motor housing 20, which houses the motor 10, is provided, the unit case mounting ribs 20c, the step part 20d, and the rib 20e (i.e., the mating parts) may be provided in the motor housing 20, the unit case ribs 22a (i.e., the mated parts) are provided in the unit case 22, and the mating parts and the mated parts are mated. In this manner, the unit case 22 can be attached to the motor housing 20 so that strength, stiffness, and the like are high.
In addition or in the alternative, the damper 26 may be held by the cover 24, which would help to make it possible to protect the unit case 22 from shock and the like and thereby to improve durability and, moreover, to make the outer surface of the cover 24 and the like and an outer surface of the damper 26 flush with one another, thereby improving the design and the handling characteristics.
In addition, the shaft 14 is connected to the oil unit 13, which is capable of generating impact torque; thereby, it is possible to configure the oil pulse driver 1 such that it achieves the operational effects of the type described above.
In addition or in the alternative, the unit case 22 may be stopped (blocked/limited) from coming off (being displaced) frontward and stopped (blocked/limited) from rotating clockwise or counterclockwise by the frontward separation stop parts (the unit case mounting ribs 20c and the step part 20i) of the motor housing 20. The internal gear 72 is stopped (blocked/limited) from coming off (being displaced) rearward by the motor housing 20 and the internal gear fixing ribs 78, and this makes it possible to securely fix the unit case 22 and the internal gear 72 inside the motor housing 20 and to fix them in an efficient configuration wherein they are stopped (blocked/limited) from coming off (being displaced) or moving in separate directions, namely, the unit case 22 is stopped (blocked/limited) from coming off (being displaced) frontward and the internal gear 72 is stopped from coming off (being displaced) rearward.
In addition or in the alternative, in the cover 24, the holes 24d, which are for fixing the damper 26, may be provided adjacent to the engaging part 24c. This design would stop or block the rotation of the cover 24, thereby it is possible to implement, in a compact configuration, both functions of stopping (blocking/limiting) the rotation of the cover 24 and mounting the damper 26.
In addition or in the alternative, the oil pulse driver 1 may comprise: the motor 10, the motor housing 20 that houses the motor 10, the oil unit 13 that is driven by the motor 10, the unit case 22 that houses the oil unit 13 and is connected to the motor housing 20, and the cover 24, which covers the unit case 22 and is held by the motor housing 20. In this embodiment, it would be possible to connect the cover 24, which is for protecting the oil unit 13, to the motor housing 20, so that the unit case 22 of the oil unit 13 is connected, rigidly and compactly, and to provide an oil pulse driver that is compact and to sufficiently protect the internal mechanisms of the oil unit 13, etc.
In addition or in the alternative, the motor housing 20 may comprise the right motor housing 20b and the left motor housing 20a, and the cover 24 may be interposed between the right motor housing 20b and the left motor housing 20a. This design would make it possible to assemble the cover 24 in a simple manner and so that the cover 24 remains strong.
In addition or in the alternative, in case the cover 24 is interposed between the right motor housing 20b and the left motor housing 20a when the cover 24 is held at the outer circumference of the unit case 22, the cover 24 may be held by the motor housing 20. This design would make it possible to combine the unit case 22 and the cover 24 with the motor housing 20 in a strong and compact manner.
In addition or in the alternative, the connecting parts (the unit case mounting ribs 20c, the step part 20d, the rib 20e, and the unit case ribs 22a) of the unit case 22 and the motor housing 20 may be disposed rearward of the light retaining upper housing 20f of the motor housing 20, which holds the cover 24. This design would make possible a compact configuration of the cover 24, which protects the unit case 22, while rigidly holding the unit case 22.
In addition or in the alternative, the circumferential surface of the unit case 22 may be connected to the inner surface of the motor housing 20 (the upper surface of the light retaining upper housing 20f, the upper side of the unit case retaining ribs 20g, 20g, and the like), and the inner surface of the motor housing 20 may hold the lower part of the unit case 22. This design would make it possible to rigidly assemble (mount) the unit case 22 to the motor housing 20 and to make the retaining structure of the unit case 22 compact.
In addition or in the alternative, at least part of the cover 24 may be disposed on the inner side of the motor housing 20, and at least part of the unit case 22 may be disposed on the inner side of the cover 24. This would make it possible to compactly combine the motor housing 20, the unit case 22, and the cover 24.
In addition or in the alternative, the ventilation path W1 may be provided between the cover 24 and the unit case 22. This would make it possible to form the ventilation path W1 for cooling and discharging the dust in a simple and compact manner by making the cover protrude from the outer surface of the unit case 22.
In addition or in the alternative, the ventilation path W0 may be provided between the cover 24 and the motor housing 20. This would make it possible to compactly and easily form the ventilation path W0 for cooling and discharging the dust.
In addition or in the alternative, the cover 24 may be held between the light 32 and the unit case 22. This would make it possible to hold the cover 24 efficiently in a compact configuration.
Furthermore, the present disclosure is not limited to the above-mentioned embodiments. The following types of modifications can be implemented as appropriate.
The internal gear retaining part and the internal gear part may be made/formed as mutually separate bodies, namely, as an internal gear retaining member and an internal gear member. In such a case, the internal gear member may be attached to the internal gear retaining member to form the internal gear.
Furthermore, the oil pulse driver 1 may comprise: the motor 10, the pinion 57 that is rotated by the motor 10, the planet gears 74 that mesh with the pinion 57, the internal gear that meshes with the planet gears 74, and the shaft 14 that is rotationally driven by and disposed frontward of the planet gears 74. In this case the internal gear comprises the internal gear member and the internal gear retaining member for holding the internal gear member, and the oil unit bearing 97 is disposed frontward of the internal gear member, and the oil unit bearing 97 is held at the front part of the internal gear retaining member. This configuration would make it is possible to provide an oil pulse driver 1 that is short in the front and rear direction, compact, and easy to handle.
In addition or in the alternative, the oil pulse driver 1 may comprise: the motor 10, the pinion 57 that is rotated by the motor 10, the planet gears 74, that mesh with the pinion 57, and the internal gear that meshes with the planet gears 74. The internal gear mat comprise the internal gear member and the internal gear retaining member for holding the internal gear member, the internal gear retaining member holds the oil unit bearing 97, the rotor shaft 50, and the front bearing 56, and the closed space is formed by the oil unit bearing 97 and the bearing 56. With this configuration, the bearings can perform multiple functions and the part count can be reduced, which makes it possible to provide an oil pulse driver 1 that is lower cost and compact.
Alternatively, instead of combining the motor housing 20 and the unit case 22 by mating them together, the unit case 22 may be screwed onto the motor housing 20. This screw fastening can be accomplished by, for example, providing a plurality of screw hole parts on the motor housing 20, providing a plurality of screw holes in portions of the unit case 22 corresponding to the screw hole parts, and then passing screws through these screw hole parts and the screw holes. In this embodiment as well, the motor housing 20 and the unit case 22 can be combined rigidly and securely.
The battery may be any arbitrary lithium ion battery of 18 V (max. 20 V) or in the range of 18-36 V, such as 18 V, 25.2 V, 28 V, or 36 V. Furthermore, a lithium ion battery of a voltage that is less than 14.4 V or greater than 36 V may be used. Naturally, other types of batteries also may be used.
Instead of the planetary gear mechanism or together with the planetary gear mechanism, a gear group wherein the tooth counts of the gears differ from one another may be used as the speed reducing gear part (speed reducing transmission).
The unit case may be fixed to the left motor housing and the right motor housing, e.g., using four screws.
The number, arrangement, material, size, form, integration, separation, and the like of the various members can be modified as appropriate. For example, the grip part in the motor housing can be made a separate body, the number of sections of the housing can be increased, the number of the various gears installed can be increased, the form of the switch of the switch lever can be modified, and/or the damper can be made such that it is not phosphorescent.
In addition to an oil pulse driver, tools of the present disclosure can also encompass a power rotary tool, an impact tool, and the like. For example, the present disclosure also encompasses: an impact driver (i.e., a rotary impact tool) wherein the oil unit is omitted, a hammer case is substituted for the unit case, and, instead of the oil unit, an impact mechanism part that comprises a hammer and an anvil is provided inside the hammer case; a rechargeable driver drill or a vibration driver drill that is configured by omitting the oil unit, adopting a gear case in place of the unit case, further disposing a speed reducing mechanism part, such as a two-stage planetary gear mechanism, making the output shaft of the speed reducing mechanism part protrude frontward from the gear case, and fixing a tip tool or bit or accessory retaining part, which holds a tip tool or accessory (i.e., a bit), to a front part of the output shaft; and the like. In addition, it is also possible to provide a power supply cord instead of or together with the battery, to connect that power supply cord to a power source (e.g., a commercial A/C power source) and thereby to supply power from that power source.
Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved power tools.
Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.
All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.
REFERENCE NUMBER LIST


    1 Oil pulse driver (power rotary tool, impact tool)
    10 Motor
    13 Oil unit (impact mechanism part)
    14 Shaft
    20 Motor housing (housing)
    20a Left motor housing (left housing)
    20b Right motor housing (right housing)
    20c Unit case mounting rib (mating part, connecting part, frontward separation stop part)
    20d Step part (mating part, connecting part)
    20e Rib (mating part, connecting part)
    20f Light retaining upper housing
    20g Unit case retaining rib (retaining part)
    20i Step part (frontward separation stop part)
    22 Unit case (case)
    22a Unit case rib (mated part)
    22c Air intake holes
    24 Cover
    24c Engaging part (separation stop, rotation stop)
    24d Hole (for fixing damper)
    26 Damper
    32 Light
    56 Bearing (second bearing)
    57 Pinion
    60 Cooling fan
    72 Internal gear
    72a Internal gear retaining part
    72c Internal gear part
    74 Planet gear
    76 Pin
    77 Carrier
    78 Internal gear fixing rib (separation stop)
    97 Oil unit bearing (first bearing)
    W0, W1, W2, W3 Ventilation paths

## Claims

1. A rotary power tool, comprising:
a motor disposed in a first portion of the rotary power tool;
a rotatable shaft operably connected to a rotor of the motor and extending away from the motor toward an output side of the power tool;
a pinion operably connected to the rotatable shaft and configured to be rotated by the motor, the pinion extending axially frontward of the motor, the frontward direction being towards the output side of the power tool;
planet gears meshed with the pinion;
pins respectively disposed in the planet gears;
an internal gear having an internal gear part meshed with the planet gears and an internal gear retaining part holding the internal gear part;
an oil unit having an input side driven by the pins, and an output side;
an output part located on the output side of the power tool and configured to be rotationally driven by the output side of the oil unit, the output part being disposed axially frontward of the planet gears and the oil unit;
a case enclosing the oil unit; and
a first bearing disposed between the internal gear part and the oil unit in the axial direction, the first bearing radially surrounding, and rotatably supporting, a rear portion of the oil unit;
wherein a first bearing retaining part of the internal gear retaining part radially surrounds the first bearing;
a portion of the case closest to the motor radially surrounds the first bearing retaining part, the planet gears and the internal gear part;
the internal gear further includes a second bearing retaining part located between the internal gear part and the motor in the axial direction; and
a second bearing is mounted in the second bearing retaining part, the second bearing directly contacting and rotatably supporting the rotatable shaft.

2. The rotary power tool according to claim 1, wherein:
the internal gear part defines a step on an inner circumferential surface of the first bearing retaining part; and
an outer raceway of the first bearing directly contacts the step.

3. The rotary power tool according to claim 2, wherein a ventilation path is defined between a radially outer surface of the internal gear and a radially inner surface of the portion of the case disposed closest to the motor, the ventilation path being in fluid communication with a hollow space defined between the oil unit and the case.

4. The rotary power tool according to claim 3, wherein the ventilation path is defined along a circumferential range of the internal gear and the case that is closest to a trigger of the rotary power tool.

5. The rotary power tool according to claim 2, wherein the case is fastened to the motor housing by a screw.

6. The rotary power tool according to claim 1, further comprising:
a cover provided on an outer circumference of the case; and
a motor housing enclosing the motor and the internal gear, the motor housing being comprised of first and second clam shell housing halves;
wherein at least a portion of the cover is disposed on a radially inner side of the motor housing.

7. The rotary power tool according to claim 6, further including a damper held by the cover.

8. The rotary power tool according to claim 6, wherein the motor housing further includes:
a frontward separation stop part blocking the case from being displaced axially frontward and from rotating clockwise or counterclockwise about the axial direction of the rotary power tool; and
a rear separation stop part blocking the internal gear from being displaced in the axial direction toward the motor.

9. The rotary power tool according to claim 8, wherein:
four ribs protrude toward the motor from a surface of the internal gear retaining part that faces the motor, the four ribs extending in a cross-shape from an axial center of the internal gear retaining part; and
the rear separation stop part of the motor housing comprises two sets of internal gear fixing ribs and two sets of sandwiching parts that respectively receive the four ribs.

10. The rotary power tool according to claim 1, wherein:
the internal gear retaining part comprises a base and a cylindrical wall projecting axially frontward from the base and having an end edge axially spaced from the base,
the internal gear part comprises a plurality of teeth projecting radially inwardly from the cylindrical wall, and
the first bearing retaining part is located on a circumferentially-inward surface of the cylindrical wall between the plurality of teeth and the end edge in the axial direction.

11. The rotary power tool according to claim 10, wherein an inner raceway of the first bearing is located radially outward of the pins.

12. The rotary power tool according to claim 11, wherein:
each tooth of the plurality of teeth has a radially inner tip lying on a circle having a diameter; and
an outer raceway of the first bearing has a diameter larger than the diameter of the circle.

13. The rotary power tool according to claim 12, wherein the plurality of teeth defines a step on an inner circumferential surface of the cylindrical wall, the step being disposed between the outer raceway of the first bearing and the plurality of teeth.

14. The rotary power tool according to claim 13, wherein the outer raceway of the first bearing is seated against, and directly contacts, the step.

15. A rotary power tool comprising:
a motor rotatably driving a pinion,
a planetary gear mechanism driven by the pinion, the planetary gear mechanism comprising a first, cup-shaped gear case having internal gear teeth integrally defined on a circumferentially-inward surface of the first, cup-shaped gear case and planet gears meshing with the internal gear teeth,
an oil unit operably coupled to an output side of the planetary gear mechanism via pins respectively disposed within the planet gears,
a second case enclosing the oil unit,
a first bearing having an inner raceway radially surrounding and rotatably supporting a rear portion of the oil unit and an outer raceway directly contacting an inner circumferential surface of the first, cup-shaped gear case, said inner circumferential surface extending axially from the internal gear teeth toward the oil unit and radially surrounding the first bearing,
a shaft operably coupled to an output side of the oil unit, and
a chuck operably coupled to the shaft,
wherein a portion of the second case closest to the motor radially overlaps and contacts an outer circumferential surface of the first, cup-shaped gear case such that the portion of the second case closest to the motor radially surrounds the first bearing, the planet gears and the internal gear teeth.

16. The rotary power tool according to claim 15, wherein:
the internal gear teeth define a step on said inner circumferential surface of the first, cup-shaped gear case; and
the outer raceway of the first bearing directly contacts the step.

17. The rotary power tool according to claim 15, wherein:
four ribs protrude toward the motor from a surface of the first, cup-shaped gear case that faces the motor, the four ribs extending in a cross-shape relative to an axial centerline of the first, cup-shaped gear case; and
a rear separation stop part of the motor housing comprises two sets of internal gear fixing ribs and two sets of sandwiching parts that respectively receive the four ribs, the rear separation stop part blocking the first, cup-shaped gear case from being displaced axially toward the motor and from rotating relative to the motor housing about the axial centerline of the first, cup-shaped gear case.

18. The rotary power tool according to claim 17, further comprising:
a second bearing mounted in a circular recess defined on a surface of the first, cup-shaped gear case that faces the motor, the second bearing directly contacting and rotatably supporting a rotatable shaft connected to the pinion,
wherein the four ribs extend from an annular projection defining the circular recess.

19. The rotary power tool according to claim 18, wherein:
a ventilation path is defined between the outer circumferential surface of the first, cup-shaped gear case and a radially inner surface of the second case,
the ventilation path is in fluid communication with a hollow space defined between the oil unit and the second case, and
the ventilation path is defined along a range of the first, cup-shaped gear case and the second case that is closest to a trigger of the rotary power tool.

20. A rotary power tool, comprising:
a motor disposed in a first portion of the rotary power tool in an axial direction of the rotary power tool;
a pinion configured to be rotated by the motor and extending axially frontward of the motor, the frontward direction being towards an output side of the power tool;
planet gears meshed with the pinion;
pins respectively disposed in the planet gears;
an internal gear having an internal gear part meshed with the planet gears and an internal gear retaining part holding the internal gear part;
an oil unit having an input side driven by the pins, and an output side;
an output part located on the output side of the power tool and configured to be rotationally driven by the output side of the oil unit, the output part being disposed axially frontward of the planet gears and the oil unit;
a case enclosing the oil unit;
a first bearing disposed between the internal gear part and the oil unit in the axial direction, the first bearing radially surrounding, and rotatably supporting, a rear portion of the oil unit;
a cover provided on an outer circumference of the case; and
a motor housing enclosing the motor and the internal gear, the motor housing being comprised of first and second clam shell housing halves;
wherein a first bearing retaining part of the internal gear retaining part radially surrounds the first bearing;
a portion of the case closest to the motor radially surrounds the first bearing retaining part, the planet gears and the internal gear part;
at least a portion of the cover is disposed on a radially inner side of the motor housing;
the motor housing further includes:
a frontward separation stop part blocking the case from being displaced axially frontward and from rotating clockwise or counterclockwise about the axial direction of the rotary power tool; and
a rear separation stop part blocking the internal gear from being displaced in the axial direction toward the motor;

four ribs protrude toward the motor from a surface of the internal gear retaining part that faces the motor, the four ribs extending in a cross-shape from an axial center of the internal gear retaining part; and
the rear separation stop part of the motor housing comprises two sets of internal gear fixing ribs and two sets of sandwiching parts that respectively receive the four ribs.

21. The rotary power tool according to claim 20, wherein:
the internal gear further includes a second bearing retaining part located between the internal gear part and the motor in the axial direction,
a second bearing is mounted in the second bearing retaining part, the second bearing directly contacting and rotatably supporting a rotatable shaft that operably connects the motor to the pinion, and
the four ribs extend from the second bearing retaining part.

22. A rotary power tool, comprising:
a motor disposed in a first portion of the rotary power tool;
a pinion configured to be rotated by the motor and extending axially frontward of the motor, the frontward direction being towards an output side of the power tool;
planet gears meshed with the pinion;
pins respectively disposed in the planet gears;
an internal gear having an internal gear part meshed with the planet gears and an internal gear retaining part holding the internal gear part;
an oil unit having an input side driven by the pins, and an output side;
an output part located on the output side of the power tool and configured to be rotationally driven by the output side of the oil unit, the output part being disposed axially frontward of the planet gears and the oil unit;
a case enclosing the oil unit; and
a first bearing disposed between the internal gear part and the oil unit in the axial direction, the first bearing radially surrounding, and rotatably supporting, a rear portion of the oil unit;
wherein a first bearing retaining part of the internal gear retaining part radially surrounds the first bearing;
a portion of the case closest to the motor radially surrounds the first bearing retaining part, the planet gears and the internal gear part;
the internal gear part defines a step on an inner circumferential surface of the first bearing retaining part;
an outer raceway of the first bearing directly contacts the step; and
a ventilation path is defined between a radially outer surface of the internal gear and a radially inner surface of the portion of the case disposed closest to the motor, the ventilation path being in fluid communication with a hollow space defined between the oil unit and the case.

23. The rotary power tool according to claim 22, wherein the ventilation path is defined along a circumferential range of the internal gear and the case that is closest to a trigger of the rotary power tool.