ELECTRIC SCREWING TOOL

Description

TECHNICAL FIELD

[0001] The present invention relates to a screw-tightening power tool used in screw-tightening work.BACKGROUND ART

[0002] A screw-tightening power tool is disclosed in US 2012 / 0319508 A1 and JP 2010-228039 A.

[0003] As disclosed in JP 2010-46739 A, a screw-tightening power tool comprises a rotary-drive part having, at a front-end part of a housing that houses a motor, a first spindle rotationally driven by the motor and a second spindle capable of holding a tip tool, the rotary-drive part being configured to be capable of tightening a screw by the transmission of the rotation of the first spindle to the second spindle when the second spindle has retracted.

[0004] Document EP 0 995 551 A2 discloses a screw-tightening tool with a motor disposed downward of the clutch. The motor is in an inclined orientation in parallel to the grip part what leads to a bulky shape of the tool.BRIEF SUMMARYPROBLEMS TO BE SOLVED

[0005] In the above-mentioned, previously existing screw-tightening power tool, a commutator motor is used as the motor; however, this causes a durability problem owing to wear of brushes and, moreover, also risks impeding miniaturization.

[0006] Accordingly, an object of the present invention is to provide a screw-tightening power tool wherein suitable durability is obtained and miniaturization also can be achieved.MEANS FOR SOLVING THE PROBLEMS

[0007] To achieve the aforementioned object, a screw-tightening power tool according to claim 1 is provided.EFFECTS

[0008] According to the present invention, the miniaturization is improved.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG 1 is an external view of a screwdriver of a first embodiment (not covered by the claims). FIG 2 is a longitudinal cross-sectional view of the screwdriver of the first embodiment. FIG 3 is an explanatory diagram of a sensor-circuit board. FIG 4 is an explanatory diagram of a modified example of a control circuit board. FIG 5 is a longitudinal cross-sectional view of the screwdriver of a second embodiment (not covered by the claims). FIG 6 is an external view of the screwdriver of a third embodiment (not covered by the claims). FIG 7 is longitudinal cross-sectional view of the screwdriver of the third embodiment. FIG 8 is a longitudinal cross-sectional view of the screwdriver of a fourth embodiment (not covered by the claims). FIG 9 is a longitudinal cross-sectional view of the screwdriver of a fifth embodiment. FIG 10 is an explanatory diagram of an operation panel. FIG 11 is a longitudinal cross-sectional view of the screwdriver of a sixth embodiment. BEST MODE(S) FOR CARRYING OUT THE TEACHINGS

[0010] Embodiments of the present teachings are explained below, with reference to the drawings.[First Embodiment (not covered by the claims)]

[0011] FIG 1 is an external view of a screwdriver 1, which is one example of a screw-tightening power tool, and FIG 2 is a longitudinal cross-sectional view thereof. In a housing 2 of the screwdriver 1, left and right half housings 2a, 2b are assembled together by screws 3, and a front housing 4 (right sides in FIGS. 1, 2 are forward), which houses an output part 53 and a brushless motor 22 described below, and a rear housing 5, which is coupled in a loop rearward of the front housing 4, are formed. Reference numeral 6 is a hook provided on a rear surface of the front housing 4. A grip part 7 is formed in an up-down direction at a rear end of the rear housing 5, and a trigger switch 8, from which a trigger 9 projects forward, is housed inside the grip part 7. A forward / reverse switching button 10 is provided upward of the trigger switch 8.

[0012] In addition, a battery pack 12, which constitutes a power supply, is attachably and detachably mounted to a mounting part 11, which is formed downward of the grip part 7. The battery pack 12 comprises a pair of left and right sliding rails 14, 14 on an upper surface of a case 13 that houses a plurality of storage batteries, and the battery pack 12 is capable of being mounted to the mounting part 11 by mating, from the rear, the sliding rails 14, 14 to and in between a pair of guide rails, which are not shown, provided on the mounting part 11 and then sliding the sliding rails 14, 14 rearward. In this mounted state, a terminal plate 16 of a terminal block 15 provided in the mounting part 11 advances into the case 13 and is electrically connected with terminals, which are not shown, inside the case 13. Reference numeral 17 is a latching hook that is provided inside the case 13 such that it protrudes and is biased upward, latches in a recessed part 18, which is provided in the mounting part 11, in the mounted state, and thereby acts to lock the battery pack 12.

[0013] Furthermore, a control circuit board 19, which is molded of resin and on which a capacitor 20, a microcontroller, etc., are installed, is provided on an upper side of the terminal block 15. The control circuit board 19 and the trigger switch 8 are electrically connected by cords 21, 21, . . ..

[0014] The brushless motor 22 is an inner-rotor-type that comprises a stator 23 and a rotor 24, and is disposed on a lower side of the front housing 4. First, the stator 23 comprises: a stator core 25; a front insulating member 26 and a rear insulating member 27, which are provided forward and rearward of the stator core 25; and a plurality of coils 28, 28, ..., which are wound around the stator core 25 via the front insulating member 26 and the rear insulating member 27. In addition, the rotor 24 comprises: a rotary shaft 29 located at an axial center; a tubular rotor core 30 disposed around the rotary shaft 29; tubular permanent magnets 31 31, . . . disposed on an outer side of the rotor core 30 and whose polarities alternate in a circumferential direction; and a plurality of sensor permanent magnets 32, disposed radially on a front side thereof. As shown in FIG 3, a sensor-circuit board 33, whereon are installed three rotation-detection devices 34, 34, ..., which detect the positions of the sensor permanent magnets 32 of the rotor 24 and output rotation-detection signals, and six switching devices 35, 35, ..., which switch the coils 28, is fixed to a front end of the front insulating member 26. Reference numerals 36 are screws that affix the sensor-circuit board 33; reference numerals 37 are projections, which are provided such that they project from a front end surface of the front insulating member 26, that mate with small holes of the sensor-circuit board 33; reference numerals 38 are coil-connection parts; and reference numeral 39 is a tongue part, which is provided such that it projects downward facing; therein, a plurality of cords 40, 40, . . . (including power-supply lines 40a for transmitting electric power from the control circuit board 19 and signal lines 40b for transmitting signals from the control circuit board 19) for electrically connecting with the control circuit board 19 is connected to the tongue part 39.

[0015] Furthermore, the stator 23 is held, with an attitude such that its axis line is oriented in the front-rear direction, inside a chamber 42 formed by ribs 41 uprightly provided on an inner surface of the front housing 4; the rotary shaft 29 is rotatably supported by a bearing 43, which is held by the rib 41 on the front side of the chamber 42, and by a bearing 44, which is held by the ribs 41 on a rear side of the chamber 42. A centrifugal fan 45 for cooling the motor is securely mounted forward of the bearing 44 on the rotary shaft 29, a plurality of air-suction ports 46, 46, . . . is formed in an outer-side region in the radial direction of the sensor-circuit board 33 in the front housing 4, and a plurality of air-exhaust ports 47, 47, . . . is formed in an outer-side region in the radial direction of the centrifugal fan 45.

[0016] Furthermore, a rear end of the rotary shaft 29 protrudes rearward from the chamber 42 and a first gear 48 is securely mounted thereon. Upward of the rotary shaft 29, a gear shaft 49 is axially supported, parallel to the rotary shaft 29, by front and rear bearings 50, 50, and a second gear 51, which is provided at a rear end of the gear shaft 49, meshes with the first gear 48. A third gear 52, the diameter of which is smaller than that of the second gear 51, is formed at a front end of the gear shaft 49.

[0017] Furthermore, the output part 53 is disposed upward of the brushless motor 22. The output part 53 comprises: a first spindle 54, which is axially supported, via a bearing 55, by the front housing 4; and a second spindle 57, which is provided such that it extends from the front housing 4 to a tubular tip housing 56 coupled forward of the front housing 4, that serves as a tip-tool retaining part axially supported via a bearing 58. A fourth gear 59 is integrally and securely mounted to a rear part of the first spindle 54, and the fourth gear 59 is meshed with the third gear 52 of the gear shaft 49. In addition, a cam 60 is integrally joined, in a rotational direction, to the front of the fourth gear 59 via a ball 61.

[0018] Moreover, the second spindle 57 is coaxially disposed forward of the first spindle 54 such that it is capable of forward-rearward movement; a mount hole 62, wherein a driver bit that is a tip tool can be inserted and mounted, is formed at a front end of the first spindle 54; and a cam part 63, which opposes the cam 60, is formed at a rear end of the first spindle 54. The cam part 63 meshes with the cam 60 in the forward rotational direction, and therefore a coil spring 64 is interposed between the cam 60 and the cam part 63. That is, a clutch (cam 60, cam part 63), through which the rotation of the second spindle 57 is transmitted when the first spindle 54 has retracted, is formed between the first spindle 54 and the second spindle 57.

[0019] Furthermore, a tip of the first spindle 54 is inserted into a bottomed hole 65, which is formed in a rear part of the second spindle 57, and a one-way clutch 66, which engages in a reverse rotational direction, is provided between both of the spindles 54, 57. Reference numeral 67 is a cap for adjusting the depth with which a front-rear position thereof is modifiably fitted to a front end of the tip housing 56.

[0020] In addition, a cap-shaped cover housing 68 is fixed to a front-end lower part of the front housing 4 forward of the brushless motor 22, and an LED 69, which serves as a light, is housed, with an attitude such that it faces diagonally frontward, downward inside the cover housing 68 and is electrically connected to the control circuit board 19 via a cord 70.

[0021] In the screwdriver 1 configured as above, when the driver bit mounted in the second spindle 57 is pressed against a screw-to-be-tightened and the second spindle 57 is retracted, the cam part 63 engages with the cam 60 of the first spindle 54. When the trigger switch 8 is turned ON by an operation of depressing the trigger 9 in this state, power is supplied from the battery pack 12, and thereby the brushless motor 22 is driven. That is, the microcontroller of the control circuit board 19 acquires the rotational state of the rotor 24 by receiving rotation-detection signals, which are output from the rotation-detection devices 34 of the sensor-circuit board 33 and indicate the positions of the sensor permanent magnets 32 of the rotor 24, sequentially supplies electric current to each of the coils 28 of the stator 23 by controlling the ON / OFF state of each of the switching devices 35 in accordance with the acquired rotational state, and thereby causes the rotor 24 to rotate. However, an amount of manipulation (press-in amount) of the trigger 9 is transmitted as a signal to the microcontroller, and the rotation of the rotor 24 is controlled in accordance with the amount of manipulation. Furthermore, another method of use is also possible wherein the second spindle 57 is caused to retract in a state in which the operation of depressing the trigger 9 has been performed beforehand and the brushless motor 22 has been caused to rotate.

[0022] Thus, when the rotor 24 rotates, the rotary shaft 29 and the first gear 48 rotate and the gear shaft 49 is rotated via the second gear 51 at a slower speed; furthermore, the first spindle 54 is rotated via the third gear 52 and the fourth gear 59 at a slower speed. Thereby, the second spindle 57, which engages with the cam 60, rotates, enabling the driver bit to perform screw tightening. As the screw tightening progresses, the second spindle 57 advances, and, when the cam part 63 disengages from the cam 60, the rotation of the second spindle 57 stops and the screw tightening terminates.

[0023] Moreover, in the case of loosening a screw, when the forward / reverse switching button 10 is switched to the reverse-rotation side, the rotor 24 rotates in reverse under the control of the microcontroller, and the first spindle 54 rotates in reverse. Because the one-way clutch 66 is provided between the first spindle 54 and the second spindle 57, the second spindle 57 also rotates in reverse, enabling the driver bit to loosen the screw.

[0024] Furthermore, when the centrifugal fan 45 rotates together with the rotary shaft 29, air drawn from the air-suction ports 46 into the chamber 42 passes between the sensor-circuit board 33 and the stator 23 and between the sensor-circuit board 33 and the rotor 24 and is discharged from the air-exhaust ports 47. Thereby, the sensor-circuit board 33 and the brushless motor 22 are cooled.

[0025] In addition, upon turning ON the trigger switch 8, the LED 69 is energized by the control circuit board 19 and turns ON. Thereby, the area ahead of the driver bit is illuminated and thus work efficiency can be maintained even in a dark location.

[0026] Furthermore, the brushless motor 22 and the LED 69 are proximate to one another, and therefore wiring is easy.

[0027] Thus, according to the screwdriver 1 of the above-mentioned first embodiment, the adoption of the brushless motor 22 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, durability is also improved because brushes are not used.

[0028] Furthermore, because the brushless motor 22 is disposed downward of the clutch, the brushless motor 22 is balanced with respect to the battery pack 12 to the rear, thereby excelling ergonomically.

[0029] In addition, because the sensor-circuit board 33 is not sandwiched between the brushless motor 22 and the first gear 48 and the like, durability with regard to heat, vibration, etc. is further increased.

[0030] Furthermore, because the tongue part 39 of the sensor-circuit board 33 is formed such that it faces downward, wiring from the control circuit board 19 to the tongue part 39 is efficient.

[0031] Furthermore, in the above-mentioned first embodiment, although the switching devices 35 are provided on the sensor-circuit board 33, they can also be provided on the control circuit board 19, as shown in FIG 4. Reference numeral 71 in FIG 4 is a microcontroller.

[0032] In addition, the speed-reducing mechanism from the rotary shaft to the first spindle likewise can be suitably modified; for example, the number of gear shafts can be increased, the gear shafts conversely can be omitted, or the like.

[0033] Next, another embodiment of the present invention will be explained. However, constituent parts identical to those in the above-mentioned first embodiment are assigned the same reference numbers, and redundant explanations thereof are omitted.[Second Embodiment (not covered by the claims)]

[0034] A screwdriver 1A shown in FIG 5 differs from the first embodiment in that the orientation of the brushless motor 22 is reversed in the front-rear direction, the sensor-circuit board 33 is located on the rear side of the stator 23, and the centrifugal fan 45 is located on the front side of the stator 23. Thereby, here, the air-suction ports 46 are disposed on the rear side of the housing 2, and the air-exhaust ports 47 are disposed on the front side of the housing 2.

[0035] In addition, a partition part 42a for spacing apart the cord 70 for the LED 69 and the outer circumference of the centrifugal fan 45 is formed, which makes it possible to supply the draft of the centrifugal fan 45 more efficiently.

[0036] Thus, in the screwdriver 1A of the above-mentioned second embodiment, too, the adoption of the brushless motor 25 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, effects the same as those in the first embodiment are obtained, such as the improvement also of durability because brushes are not used.

[0037] In particular, the sensor-circuit board 33 is closer to the control circuit board 19 than it is in the first embodiment, which is advantageous because it is possible to get by with a shorter run of wiring.[Third Embodiment (not covered by the claims)]

[0038] In a screwdriver 1B shown in FIGS. 6, 7, the housing 2 has a shape of an L turned on its side and comprises: a motor housing 72, which houses the brushless motor 22 and the output part 53 and extends in the front-rear direction, and a grip housing 73, which extends from a rear end of the motor housing 72 in the downward direction; furthermore, the mounting part 11 of the battery pack 12 is formed at a lower end of the grip housing 73. The LED 69 is housed, upward of the terminal block 15, such that it faces diagonally upward from the mounting part 11.

[0039] In addition, the control circuit board 19 herein is provided integrally with a lower part of the trigger switch 8 to form a switch assembly 74; the control circuit board 19 of the switch assembly 74 and the sensor-circuit board 33 are electrically connected via cords 84, 84, . . .; and the control circuit board 19 and the LED 69 are electrically connected via cords 85, 85. The control circuit board 19 is equipped with an IPM (Intelligent Power Module) 75 in addition to the microcontroller 71, the capacitors 20, etc. The IPM contains switching devices (IGBTs) and is encapsulated with a driver for driving, which is for driving the switching devices.

[0040] Furthermore, in the brushless motor 22, a connecting piece 76, which protrudes toward the outer side in the radial direction, is provided on the rear insulating member 27 of the stator 23 such that it protrudes therefrom, and a cord 77 that supplies electric power to the coils 28 is connected to the coils 28 through the connecting piece 76.

[0041] Furthermore, a pinion 78 is securely mounted to a front end of the rotary shaft 29, and the pinion 78 directly meshes with the first spindle 54 and an integrated gear 79.

[0042] Thus, in the screwdriver 1B of the above-mentioned third embodiment, too, the adoption of the brushless motor 22 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, effects the same as those in the first embodiment are obtained, such as the improvement also of durability because brushes are not used.

[0043] Here in particular, the adoption of the switch assembly 74 is advantageous in that the time and labor needed for assembly are reduced and in that the wiring procedure is easier because the wiring is concentrated in one location.

[0044] Furthermore, because the centrifugal fan 45 is located between the brushless motor 22 and the gear 79, direct and indirect cooling of the gear 79 is also possible, in addition to the cooling of the brushless motor 22.

[0045] Furthermore, although the positional information of the rotor 24 is output from the sensor-circuit board 33 via the signal lines 40b, the sensor-circuit board 33 is located on the rear side, and therefore the connection to the control circuit board 19 is easy. In addition, because the connecting piece 76 of the rear insulating member 27 is also on the rear side, the connection to the control circuit board 19 is easy.[Fourth Embodiment (not covered by the claims)]

[0046] In a screwdriver 1C shown in FIG 8, the orientation of the brushless motor 22 is the reverse in the front-rear direction of that of the third embodiment, and therefore the sensor-circuit board 33 is on the front side and the centrifugal fan 45 is on the rear side.

[0047] Thereby, in the screwdriver 1C of the above-mentioned fourth embodiment, too, the adoption of the brushless motor 22 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, effects the same as those in the third embodiment are obtained, such as the improvement also of durability because brushes are not used.[Fifth Embodiment]

[0048] In a screwdriver 1D shown in FIG 9, the control circuit board 19 is provided not on the trigger switch 8 but rather above the terminal block 15 as in the first embodiment, and therefore power is supplied to the coils 28 via the sensor-circuit board 33, not via the insulating members.

[0049] In addition, here, an operation panel 80 shown in FIG 10 is provided on an upper surface of the mounting part 11 and rearward of the LED 69. The operation panel 80 is provided with a light switch 81, a remaining-capacity-display switch 82, and a battery indicator 83, and is electrically connected to the control circuit board 19; furthermore, the luminous flux intensity of the LED 69 changes in steps every time the operation of pressing the light switch 81 is performed and, when the operation of pressing the remaining-capacity-display switch 82 is performed, the battery indicator 83 lights up a number of gradations in accordance with the remaining capacity of the storage battery of the battery pack 12.

[0050] Thus, in the screwdriver 1D of the above-mentioned fifth embodiment, too, the adoption of the brushless motor 22 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, effects the same as those in the first embodiment are obtained, such as the improvement also of durability because brushes are not used.

[0051] Here in particular, the illumination mode of the LED 69 can be changed by the light switch 81, and the remaining capacity of the battery is made evident at a glance by the remaining-capacity-display switch 82, thereby excelling in user-friendliness.[Sixth Embodiment]

[0052] In a screwdriver 1E shown in FIG 11, the orientation of the brushless motor 22 is the reverse in the front-rear direction of that in the fifth embodiment, that is, the sensor-circuit board 33 is on the rear side and the centrifugal fan 45 is on the front side.

[0053] Thereby, in the screwdriver 1E of the above-mentioned sixth embodiment, too, the adoption of the brushless motor 22 can be expected to increase motive-power-transmission efficiency and miniaturization, thereby enabling screw tightening at low power. In addition, effects the same as those in the fifth embodiment are obtained, such as the improvement also of durability because brushes are not used.

[0054] Furthermore, because the sensor-circuit board 33 is on the rear side, it is advantageous in that the wiring run is shorter than that in the fifth embodiment.

[0055] Furthermore, in common with the third through sixth embodiments, the reduction of speed from the rotary shaft to the first spindle is performed by the pinion and the gear, but it is also possible to achieve a reduction in speed with a planetary-gear mechanism disposed coaxially with the rotary shaft and the first spindle.

[0056] In addition, the switch assembly of the third embodiment, the operation panel of the fifth embodiment, and the like can also be adapted to a screwdriver of the type in the first and second embodiments.EXPLANATION OF THE REFERENCE NUMBERS

[0057] 1, 1A-1EScrewdriver 2Housing 4Front housing 5Rear housing 8Trigger switch 11Mounting part 12Battery pack 15Terminal block 19Control circuit board 22Brushless motor 23Stator 24Rotor 25Stator core 26Front insulating member 27Rear insulating member 28Coil 29Rotary shaft 30Rotor core 31Permanent magnet 32Sensor permanent magnet 33Sensor-circuit board 34Rotation-detection device 35Switching device 42Chamber 45Centrifugal fan 49Gear shaft 53Output part 54First spindle 57Second spindle 60Cam 63Cam part 71Microcontroller 74Switch assembly 80Operation panel 81Light switch 82Remaining-capacity-display switch

Claims

1. A screw-tightening power tool, comprising a housing (2) having a L-shape, wherein the housing (2) comprises a motor housing (72) extending in a front-rear-direction, and a grip housing (73) extending from a rear end of the motor housing (72) in the downward direction, a brushless motor (22) comprising a stator (23) fixed to the motor housing (72) and a rotor (24) rotatable with respect to the stator (23), wherein the brushless motor is housed in the motor housing (72), wherein an axis line of the stator (23) is oriented in the front-rear-direction, a tip-tool retaining part (57, 62) capable of holding a bit, a mounting part (11) formed at a lower part of the grip housing (73) for detachably mounting a battery pack, wherein a terminal block (15) is provided in the mounting part, a control circuit board (19) provided upward of the battery pack, when mounted, wherein the control circuit board is provided on an upper side of the terminal block (15) and a clutch (60, 63) disposed between the rotor and the tip-tool retaining part (57, 62), wherein the brushless motor is disposed downward of the clutch.

2. The screw-tightening power tool according to claim 1, wherein a cooling fan (45) is provided between the stator (23) and the clutch (60, 63).

3. The screw-tightening power tool according to claim 1 or 2, wherein a light (69) is disposed at the mounting part (11), and the light (69) and the control circuit board (19) are connected by a cord.

4. The screw-tightening power tool according to any one of claims 1 to 3, wherein a trigger switch (8) is provided in the grip housing, and a trigger (9) is held by the trigger switch (8).

5. The screw-tightening power tool according to claim 4, wherein a sensor-circuit board (33) fixed to the stator (23) is provided, the sensor-circuit board (33) and the trigger switch (8) are connected by a cord, and the stator (23) and the trigger switch (8) are connected by a cord.

6. The screw-tightening power tool according to claim 4 or 5, when dependent on claim 3, wherein the light (69) is connected to the trigger switch (8) by a cord.

7. The screw-tightening power tool according to any one of claims 1 to 6, wherein the control circuit board (19) is provided at a lower end of the grip housing (73).

8. The screw-tightening power tool according to any one of claims 1 to 7, wherein the stator comprises a stator core (25), a front insulating member (26) and a rear insulating member (27), which are provided forward and rearward of the stator core (25), respectively, and a plurality of coils (28) wound around the stator (23) via the front and rear insulating member (26, 27), and the brushless motor further comprises a connecting piece (76) that connects the coils (28) to a cord (77).

9. The screw tightening power tool according to any one of claims 1 to 8, wherein the clutch (60, 63) comprises a cam (60) rotated by the rotor, a cam part (63) which opposes the cam (60), and a coil spring (64) interposed between the cam (60) and the cam part (63).