JP2006326784A - Power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-noise power tool capable of suppressing occurrence of rattling even over a long-term use. <P>SOLUTION: An elastic member 1 is composed of a first elastic member 14a positioned at the side to be compressed when a second gear is driven to rotate with a first gear 10, and a second elastic member 14b positioned at the opposite side to the first elastic member 14a with respect to a wall surface part 12A. The first and second elastic members 14a, 14b are positioned between a recessed part 10a and the wall surface part 12A in a compressed state, and the spring constant of the second elastic member 14b is made smaller than the spring constant of the first elastic member 14a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric tool having a gear mechanism.

2. Description of the Related Art Conventionally, in an electric power tool, rotational fluctuations occur due to an excitation force due to an alternating current, a gear pitch error, eccentricity, and the like, and the driving shaft side gear and the driven shaft side gear repeatedly collide and vibrate on their respective tooth surfaces. Noise is generated by this collision or the like, and the collision force between the tooth surface and the tooth surface becomes an excitation force, and noise is generated from other than the gear portion. In particular, at the time of start-up, since the torque on the drive shaft side is large, the impact is large and noise is generated.

  In order to solve this problem, measures have been taken by improving gear accuracy and changing the shape of the tooth surface. As a method of structurally reducing noise, a steel key provided on the inner diameter of the gear is used to connect the drive shaft and the drive gear, and as shown in Patent Document 1, the drive shaft and For example, a driving force is transmitted to and from the driving gear via an elastic member.

JP-A-3-49883

  The conventional electric tool described above generates noise due to a collision or the like, and the collision force between the tooth surface and the tooth surface becomes an excitation force, and noise is generated from other than the gear portion. In particular, at the time of start-up, since the torque on the drive shaft side is large, the impact is large and noise is generated. In order to reduce this noise, when the steel key is used, the steel key may be deformed and become larger due to long-term use, which may be a noise source.

  An object of the present invention is to provide an electric tool that suppresses the occurrence of backlash even during long-term use and has low noise.

  The object is a rotary shaft, a member press-fitted into the rotary shaft, an intermediate member having a convex portion, and a gear arranged coaxially with the rotary shaft, and a gap is provided between the convex portion and the rotational direction. A power tool having a first gear having a recess that can be held and engaged, an elastic member provided on both sides in the rotation direction of the projection in the recess, and a second gear meshing with the first gear The elastic member includes: a first elastic member positioned on a side compressed when the second gear is rotationally driven with the first gear; and the first elastic member with respect to the convex portion. A second elastic member located on the opposite side, and the first and second elastic members are positioned between the concave portion and the convex portion in a compressed state, and the spring of the second elastic member This can be achieved by making the constant smaller than the spring constant of the first elastic member.

  According to the first aspect of the present invention, since the spring constant of the second elastic member is smaller than the spring constant of the first elastic member, the second elastic member has a lower elastic constant than the first elastic member. The initial compression amount can be set large. Therefore, even if the first elastic member is plastically deformed, the compression portion of the second elastic member is opened, so that the occurrence of rattling can be prevented. Therefore, it is possible to suppress the deterioration of the gear sound due to the occurrence of rattling.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  A configuration of a disc grinder as an example of an electric power tool according to an embodiment of the present invention will be described with reference to FIGS. A disc grinder 1 shown in FIG. 1 mainly includes a housing 2 that supports and accommodates a motor 3 therein, a grinding wheel 5 that is rotationally driven by the motor 3, a cover 6, and a fan 7. The housing 2 includes a switch (not shown) that controls the driving of the motor 3. The grinding wheel 5 is attached to a spindle 11 which will be described later, and can rotate only in a cutting direction (forward rotation direction). The cover 6 is attached to the housing 2 and has a shape that covers the upper half of the outer periphery of the grinding stone 5. A fan 7 for generating fan wind by rotation to cool the motor 3 is fixed to the drive shaft 4 of the motor 3.

  A pinion gear 8, which is a helical bevel gear, is provided on one end side of the drive shaft 4. The drive shaft 4 and the pinion gear 8 are rotatably supported by a first bearing 9 </ b> A provided in the housing 2. A spindle 11 that extends at right angles to the drive shaft 4 and serves as a rotation shaft for rotating the grinding wheel 4 is supported in the housing 2 by a second bearing 9B and a third bearing 9C. A gear 10, which is a helical bevel gear that meshes with the second gear 8, is fixed coaxially with the spindle 11 on the housing 2 side of the spindle 11. A pair of fixing members 11 </ b> C are attached to the spindle 11 so as not to rotate with respect to the spindle 11. The grinding stone 5 is sandwiched and fixed between the pair of fixing members 11C. In the claims, the first gear and the second gear are the gear 10 and the pinion gear 8, respectively.

  The configuration of the gear device included in the electric power tool according to the embodiment of the present invention will be described with reference to FIG. The gear 10 has a recess 10a formed in the side surface thereof in the axial direction of the gear 10, and a hole 10b is formed in the recess 10a. A convex portion 10 </ b> A is formed in the concave portion 10 a so that a cross section of the concave portion 10 a protrudes toward the central axis direction of the gear 10. 10 A of convex parts are comprised from 10 A-1 of convex parts, and convex part 10 A-2, and this convex part 10 A is provided in the position of the mutually opposite side of the diameter direction of the recessed part 10a. The gear 10 is inserted into the first shaft 11A of the spindle 11 through the hole 10b. The inner diameter of the hole 10b is slightly larger than the first shaft 11A.

The first shaft 11A protruding into the recess 10a in a state where the gear 10 is extrapolated to the first shaft 11A
The hole 12a of the intermediate member 12 is externally inserted and press-fitted. The intermediate member 12 forms a wall surface 12B and includes a pair of wall surface portions 12A provided on opposite sides in the diameter direction of the intermediate member 12, and a pair of protruding portions 12C provided at positions substantially orthogonal to the wall surface portion 12A. I have. When the intermediate member 12 is extrapolated, the protrusion 12C is inserted into the gap 10d between the protrusions 10A-1 and 10A-2 of the recess 10a. Since the protruding portion 12C and the protruding portion 10A are arranged at positions where they can contact each other, the protruding portion 12C can move only between the protruding portion 10A-1 and the protruding portion 10A-2, and the protruding portion 12C is provided. The intermediate member 12 thus made can only rotate during this time. The wall surface portion 12A is disposed in the gap 10c between the pair of convex portions 10A.

  Further, the gear 10 is held by the spindle 11 and the intermediate member 12 at the proximal end position of the first shaft 11A. The intermediate member 12 is press-fitted and tightly fitted, but is not press-fitted to the position where the gear 10 is fixed, and the gear 10 and the spindle 11 are relatively rotatable.

  After the intermediate member 12 is press-fitted, as shown in FIG. 3, the elastic members 14 are respectively arranged in the gaps 10c partitioned by the wall surface portion 12A. In addition, the convex part and recessed part in a claim are the wall surface part 12A and the recessed part 10a, respectively.

The elastic member 14 is made of rubber having heat resistance and oil resistance. The elastic member 14 has a substantially elliptical cross section, and one surface forming the elliptical shape faces the side surface 10B in the gap 10c, and the other surface forming the elliptical shape faces the wall surface 12B of the wall surface portion 12A. And since this wall surface part 12A becomes the shape pinched | interposed between the 1st elastic member 14a and the 2nd elastic member 14b in the clearance gap 10c,
The wall surface portion 12A is positioned substantially at the center in the gap 10c. Therefore, the protruding portion 12C provided at a position substantially orthogonal to the wall surface portion 12A is positioned at the approximate center of the gap 10d, as shown in FIG. 3, and between the protruding portion 12C and the protruding portion 10A. A gap is formed in the protrusion 12C so that the protrusion 12C does not contact the protrusion 10A in a state where no load is applied.

  The concave portion 10a that encloses the elastic member 14 is formed symmetrically with respect to the center axis as a point on a plane having the normal axis as the center axis of rotation of the gear 10. Further, the spindle 11 and the intermediate member 12 are formed point-symmetrically with respect to the center axis as a point on a plane having the normal axis as the center axis of rotation of the spindle 11. When the elastic member 14 is disposed in the gap 10c, the elastic member 14 faces the side surface 10B and the wall surface 12B and is in contact with the outer peripheral surface of the intermediate member 12 so as to be compressed and held between the intermediate member 12 and the first gear 10. The Since the concave portion 10a, the intermediate member 12 and the spindle 11 are formed point-symmetrically, the positional relationship between the intermediate member 12 and the spindle 11 and the first gear 10 through the elastic member 14 having substantially the same shape, Since the central axes of the respective rotations are substantially the same, and the elastic member 14 is compressed and held, the positional relationship between the intermediate member 12 and the spindle 11 and the first gear 10 is also maintained without any deviation. Be drunk.

  The washer 13 has a hole 13a formed in the center thereof, and is attached to hold the elastic member 14 disposed in the recess 10a in the recess 10a. With the elastic member 14 disposed, the washer 13 is inserted into the second shaft 11B protruding from the first shaft 11A through the hole 13a and press-fitted. Since the hole 13a is also provided with a predetermined allowance for the second shaft 11B, the washer 13 is inserted into the second shaft 11B by being inserted into the second shaft 11B through the hole 13a, and is tightly fitted. Is done. The washer 13 prevents the elastic member 14 from being discharged from the place where it is disposed. With the above configuration, the spindle 11 and the gear 10 can rotate together. A gear device is configured including the gear 10, the spindle 11, the intermediate member 12, and the elastic member 14.

  The operation of the disc grinder 1 configured as described above will be described. In the disc grinder 1, the motor 3 rotates when an operator inputs it with a switch (not shown) of the disc grinder 1, and this rotation is transmitted to the pinion gear 8 and the gear 10, and finally the spindle 11 connected to the gear 10. The grinding wheel 5 held between and fixed to is rotated. Since the center axis of rotation of the gear 10 and the spindle 11 is substantially the same, vibration due to the swing of the center axis of rotation between the spindle 11 and the gear 10 is reduced.

  At this time, the gear 10 rotates clockwise. Since the grinding wheel 5 is stopped when the switch is turned on, the spindle 11 to which the grinding wheel 5 is fixed and the intermediate member 12 press-fitted into the spindle 11 try to stop at that position due to the inertial force. Rotate in a counterclockwise direction relative to. However, since the wall surface portion 12A provided in the intermediate member 12 and the side surface 10B in the recess 10a abut via the elastic member 14A, the elastic member 14a is compressed, so that the intermediate member 12 and the gear 10 are compressed. Prevents contact and rotates smoothly with low noise.

  When the disc grinder 1 is rotating and starts to grind a material to be ground such as a plate, a load is applied to the grinding wheel 5 for grinding. This load is determined by the material, thickness, etc. of the material to be ground, but not all of the material to be ground becomes the same load, and a change occurs in the load caused by the grinding part. Due to this change in load, the spindle 11 and the intermediate member 12 try to rotate clockwise and counterclockwise with respect to the gear 10, but the force generated by these rotations is the elasticity between the intermediate member 12 and the gear 10. Since the first gear 10 is absorbed by the member 14, the first gear 10 is not easily affected by the change in the load. As a result, rattling between the teeth of the gear 10 and the pinion gear 8, and noise, deformation, and the like caused by the rattling are caused. Occurrence can be suppressed.

  Even during normal rotation where no load is generated, the rotational speed of the gear 10 slightly changes due to the excitation force of the AC power supply, the pitch error between the gear 10 and the pinion gear 8, eccentricity, and the like. Since it is absorbed by the elastic member 14 between the intermediate member 12 and the gear 10, it is difficult to be transmitted to the spindle 11 and the intermediate member 12, and the spindle 11 and the intermediate member 12 including the grinding wheel 5 are connected to the grinding wheel 5. Then, it rotates constantly. For this reason, generation | occurrence | production of the vibration of the grindstone 5 and the generation | occurrence | production of the noise resulting from this vibration can be suppressed. In some cases, impacts due to subtle rotational deviations may occur between the intermediate member 12 and the first gear 10, but these impacts are absorbed by the elastic member 14. It is possible to reduce an impact that causes a sense of discomfort to the person.

  When the disc grinder 1 stops, the switch is turned off when the operator removes his / her hand from the switch, and the electromagnetic brake is applied to the motor 3. Due to the electromagnetic brake, a load is generated in the rotation of the pinion gear 8, and the rotation of the gear 10 also stops rapidly. However, the spindle 11 and the intermediate member 12 including the grinding wheel 5 rotate in the clockwise direction relative to the gear 10 due to the inertial force of the grinding wheel 5. At this time, the wall surface portion 12A provided in the intermediate member 12 and the side surface 10B in the recess 10a abut via the elastic member 14b, and the elastic member 14b is compressed, so that the intermediate member 12 and the gear 10 are in contact with each other. It is possible to prevent contact and stop without causing an impact or the like.

  In addition, when the grinding wheel 5 is stopped from rotating instantaneously, for example, when the grinding wheel 5 is pinched by the grinding material that is ground during grinding, the rotation is stopped, or when grinding is performed, The grinding material may be a material that cannot be ground by the disc grinder 1. In this case, the grinding wheel 5 and the spindle 11 for fixing the grinding wheel 5 stop, but the intermediate member 8 and the gear 10 connected to the motor 3 try to rotate. At this time, the elastic member 14 interposed between the intermediate member 12 and the gear 10 is compressed between the wall surface 12B and the side surface 10B. When an excessive pressure is applied to the elastic member 14, the elastic member 14 is plastically deformed and loses its elastic characteristics. Therefore, in order to prevent this, in order to prevent the elastic member 14 from being deformed to the plastic region, the intermediate member 12 is not rotated more than a certain rotation angle with respect to the gear 10 in a state where it is compressed more than a certain value. To.

  Specifically, the protrusion 12 </ b> C of the intermediate member 12 and the protrusion 10 </ b> A of the gear 10 come into contact with each other, thereby preventing the intermediate member 12 from rotating more than the contact portion with respect to the gear 10. The convex portion 10A comes into contact with the protruding portion 12C in the clockwise direction, the protruding portion 10A-1, the convex portion 10A-2 in the counterclockwise direction, and the protruding portion 12C rotating in any direction. Is provided.

  Therefore, when the grinding wheel 5 is stopped instantaneously, the gear 10 rotates while the positions of the spindle 11 and the intermediate member 12 are stopped. Therefore, the second elastic member 14b is contracted and the projecting portion 12C and the projecting portion 10A are contracted. -2 contacts. After the contact, the first gear 10 and the intermediate member 12 rotate together. At this time, if the reaction force due to the grinding wheel 5 being stopped has not been reduced, the reaction force is transmitted to the motor 3 via the pinion gear 8 connected to the gear 10. As a result, the motor 3 may be damaged.

  However, the intermediate member 12 is only press-fitted into the first shaft 11 </ b> A of the spindle 11, and the intermediate member 12 can rotate with respect to the spindle 11 with an axial torque of 30 Nm to 50 Nm or more. Since the grinding wheel 5 stops instantaneously and the reaction force applied between the spindle 11 and the gear 10 exhibits an axial torque of 50 Nm or more, in this case, slipping occurs between the intermediate member 12 and the spindle 11. Arise. Therefore, even if the grinding wheel 5 and the spindle 11 stop rotating, the gear 10 and the intermediate member 12 integrated with the gear 10 rotate for a certain period due to the slip between the intermediate member 12 and the spindle 11, The pinion gear 8 absorbs the energy related to the shaft torque as the frictional force of the press-fitting point until the shaft torque related to the first gear 0 becomes equal to or less than the shaft torque necessary for the slip between the intermediate member 12 and the spindle 11. As a result, even when the grinding wheel 5 is suddenly stopped, the motor 3 is stopped without applying a load, and the elastic member 14 can be prevented from being deteriorated during the stop.

  The present invention is characterized in that the spring constant of the second elastic member 14b is smaller than that of the first elastic member 14a.

  As shown in FIGS. 4 to 7, when the second elastic member 14b has an inclination, a protrusion, and a step, the contact area is smaller than the first elastic member 14a having a straight shape, so that the initial spring constant is obtained. Can be lowered.

  The effect obtained by reducing the spring constant of the second elastic member 14b will be described. By reducing the spring constant of the second elastic member 14b, the compression amount of the second elastic member 14b can be set larger than that of the first elastic member 14a. Therefore, the release amount of the elastic member 14b increases. Therefore, when the first elastic member 14a is plastically deformed due to long-term use, the second elastic member 14b is released at the reduced portion of the first elastic member 14a, and the generation of rattling can be suppressed, and the gear noise is deteriorated. Can be prevented.

  In addition, since the second elastic member 14b has a large initial compression amount, there is a concern that the second elastic member 14b may be plastically deformed with use. However, in the power tool such as the disc grinder exemplified in this example, Since no large load is generated on the elastic member 14b, there is no problem because compression deformation is not performed.

Moreover, in the gear apparatus mentioned above, although all absorbed the excessive load using the slip between the intermediate member 12 and the spindle 11 which is a rotating shaft, the apparatus which absorbs an excessive load is provided elsewhere. In the case where it is not necessary to absorb with the gear device or when an excessive load is not generated, the wall surface portion or the protruding portion may be provided directly on the rotating shaft without providing the intermediate member 12. And the elastic member 14 which includes the wall surface part 12A and the protrusion part 12C in the recessed part of the 1st gearwheel 10 like the above-mentioned Example, and a contact location comprises a curved surface is arrange | positioned. With such a configuration, the elastic member 14 absorbs an impact generated between the rotating shaft and the first gear 10, and the elastic member 14 protrudes so as not to be plastically deformed when a load due to the impact is large. It becomes possible to arrange the portion 12C and the convex portion 10A and prevent the elastic member 14 from being excessively deformed.

Sectional drawing of the disc grinder which is an example of the electric tool which concerns on embodiment of this invention. The disassembled perspective view of the gear apparatus contained in the electric tool which concerns on embodiment of this invention. The perspective view of the gear apparatus contained in the electric tool which concerns on embodiment of this invention. The perspective view of the elastic member contained in the electric tool which concerns on embodiment of this invention. The perspective view of the elastic member contained in the electric tool which concerns on embodiment of this invention. The perspective view of the elastic member contained in the electric tool which concerns on embodiment of this invention. The perspective view of the elastic member contained in the electric tool which concerns on embodiment of this invention.

Explanation of symbols

1 is a disc grinder, 2 is a housing, 3 is a motor, 4 is a drive shaft, 5 is a grinding wheel, 6 is a cover, 7 is a fan, 8 is a pinion gear, 9A is a first bearing, 9B is a second bearing, 9C Is a third bearing, 10 is a gear, 10A is a convex portion, 10B is a side surface, 10a is a concave portion, 10b is a hole, 10c is a gap, 10d is a gap, 11 is a spindle, 11A is a first axis, 11B is a second axis, 12 is an intermediate member, 12A is a wall surface portion, 12B is a wall surface, 12C is a protruding portion, 12a is a hole, 13 is a washer, 13a is a hole, 14 is an elastic member, 14a is a first elastic member, and 14b is a second elastic member. It is a member.

Claims (1)

A rotation axis;
An intermediate member that is press-fitted into the rotating shaft and has a convex portion;
A first gear having a concave portion engageable with a gap in a rotational direction with the convex portion, the gear being arranged coaxially with the rotation shaft;
An elastic member provided on both sides of the convex portion in the rotational direction in the concave portion;
A second gear meshing with the first gear;
In an electric tool having
The elastic member is
A first elastic member located on a side to be compressed when the second gear rotates with the first gear;
A second elastic member located on the opposite side of the convex portion from the first elastic member;
Have
The first and second elastic members are positioned between the concave portion and the convex portion in a compressed state,
An electric power tool characterized in that a spring constant of the second elastic member is made smaller than a spring constant of the first elastic member.

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