JP6031844B2 - Press-in method - Google Patents

Description

  The present invention relates to a method for press-fitting a press-fit member into a press-fit member.

  For example, an assembling method is known in which a shaft formed on a press-fitting member is press-fitted into a hole formed on the press-fitted member. Here, if press-fitting is not performed in a state where the center axis of the hole formed in the press-fit member and the center axis of the shaft formed in the press-fit member coincide with each other, the assembly accuracy between the press-fit member and the press-fit member is lowered. There is a fear. Therefore, when performing press-fitting, it is desirable to match the center axes of the press-fitted member and the press-fitting member as much as possible. As a method for aligning the center axes of these two members, a method using a centering action by a taper is known. (For example, Patent Document 1).

JP-A-62-255042

  By the way, when the press-fitting member is press-fitted into the press-fitted member, a large press-fitting force is applied to the press-fitting member, so that there is a possibility that the aligning action by the taper cannot be sufficiently obtained. Hereinafter, with reference to FIG. 11, the reason why the alignment action is insufficient will be described.

  As shown in FIG. 11, the press-fitting member 100 is formed in a rod shape, and an axial taper portion 100a is formed on the periphery of the tip portion. Further, the press-fitting member 200 has a hole 200b into which the press-fitting member 100 is press-fitted. And the hole side taper part 200a is formed in the opening part of the hole 200b. The press-fitting member 200 is placed on the work holding table 400. That is, the end surface 200 c orthogonal to the central axis of the hole 200 b in the press-fitted member 200 is in contact with the work holding table 400.

  When the press-fitting of the press-fitting member 100 into the press-fitted member 200 is started and the press-fitting is advanced in a state where the shaft-side tapered portion 100a of the press-fitted member 100 and the hole-side tapered portion 200a of the press-fitted member 200 are in contact with each other, The first component force FA for pressing the press-fitting member 200 against the work holding base 400, which is a component force of the pressing force D for press-fitting 100, becomes very large. Therefore, a very large frictional force is generated between the work holding base 400 and the end surface 200c of the press-fit member 200. Therefore, the contact portion S where the shaft-side taper portion 100a and the hole-side taper portion 200a are in contact with each other is a component of the pressing force D, and the axial misalignment between the press-fit member 200 and the press-fit member 100 is eliminated. The second component force FB that moves the press-fitted member 200 in the direction of the movement acts. The movement of the press-fitted member 200 by the second component force FB, that is, the movement of the press-fitted member 200 by the aligning action is the friction. There is a possibility that the aligning action by the taper is not obtained sufficiently due to the force. And when the aligning action by a taper is not fully acquired, there exists a possibility that the assembly | attachment precision of the press-fit member 100 and the press-fit member 200 may fall as mentioned above.

  FIG. 12 shows an example of a state where the assembly accuracy between the press-fitting member 100 and the press-fitted member 200 is lowered due to the press-fitting performed in a state where the alignment action by the taper is not sufficiently obtained. In FIG. 12, the assembly state of the press-fitted member 200 when it is press-fitted with the shaft center shifted is indicated by a solid line. As a comparative example, the assembled state of the press-fitted member 200 when the press-fit member 200 is press-fitted in a state where the shaft centers coincide is indicated by a two-dot chain line.

  As shown by a two-dot chain line in FIG. 12, when press-fitting is performed with the axes aligned, the press-fitting member 200 is assembled perpendicular to the central axis L <b> 1 of the press-fitting member 100. That is, the end surface 200c of the press-fit member 200 is assembled perpendicularly to the central axis L1.

  On the other hand, as shown by a solid line in FIG. 12, when the press-fit member 200 is press-fitted in a state where the axes do not coincide with each other, the press-fitted member 200 may be assembled while being tilted with respect to the press-fit member 100. Therefore, the end face 200c of the press-fit member 200 is displaced from the original assembled state, and the end face shake amount (the shake amount in the direction indicated by the arrow T in FIG. 12 (the shake amount in the direction of the central axis L1)). ) Becomes larger.

  Since a large pressing force (pressure input) is applied to the press-fitting member in this way, the alignment action by the taper may not be sufficiently obtained, and the assembly accuracy between the press-fitting member and the press-fitted member may be reduced. is there.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a press-fitting method capable of improving the assembly accuracy of the press-fitting member and the press-fitted member.

In order to achieve the above object, the invention according to claim 1 is a method of press-fitting a shaft formed on one of a press-fitting member and a press-fitted member into a hole formed on the other, the tip of the shaft At least one of the peripheral edge of the portion and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole, and the press-fitting placed on the work holding base Before press-fitting the press-fitting member into the member, it is a component force generated in the tapered portion when the peripheral edge of the tip and the opening are in contact with the tapered portion, and the radius of the hole the component force acting in the direction, and wherein the workpiece holding table have rows step be greater than the frictional force generated at the contact surface between the press-fitting member, the pressing portion to impart press-fit load abuts on the press-fitting member A biasing force smaller than the press-fitting load provided at the pressing part. And a pin that is provided in the pressing portion and that biases the press-fitting member against the press-fitted member by the biasing force of the elastic member. In the step, the pressing applied to the press-fitting member The gist is that the load is made lower than the pressing load at the time of press-fitting, and the pressing portion that is in contact with the press-fitting member is separated from the press-fitting member and the press-fitting member is urged against the press-fitted member by the pin. .

  According to this method, the following process is performed before press-fitting the press-fitting member into the press-fitted member. In other words, when the peripheral edge of the shaft and the opening of the hole are in contact with each other at the taper for alignment, the component is generated in the tapered part and acts in the radial direction of the hole, that is, the target force. A step is performed in which a component force for moving the press-fit member in a direction to eliminate the axial misalignment between the press-fit member and the press-fit member is larger than a frictional force generated on the contact surface between the work holding base and the press-fit member.

When this step is performed, the component force (corresponding to the above-described second component force FB) that moves the press-fit member in the direction to eliminate the axial misalignment is larger than the frictional force between the work holding base and the press-fit member. Become. For this reason, the press-fitted member can easily move in the direction in which the axial misalignment between the press-fitted member and the press-fitted member is eliminated, and the alignment action by the tapered portion can be easily obtained. Therefore, according to the method, the center axes of the press-fitting member and the press-fitted member can easily coincide with each other in the press-fitting process, thereby improving the assembly accuracy of the press-fitting member and the press-fitted member.
Further, according to this method, since the pressing load applied to the press-fitting member is made lower than the pressing load at the time of press-fitting, the tip end peripheral edge of the press-fitting member shaft and the opening of the hole of the press-fitting member are aligned. When the contact is made at the tapered portion, the pressing load acting on the tapered portion is lower than the pressing load at the time of press-fitting. Therefore, the component force of the pressing force that acts on the tapered portion and the component force that presses the press-fitted member against the work holder (corresponding to the first component force FA described above) is small compared to the case where the pressing load is not reduced. Become. Accordingly, the frictional force generated between the press-fitted member and the work holding base is smaller than that in the case where the pressing load is not reduced. By reducing the frictional force in this way, the component force generated in the tapered portion and acting in the radial direction of the hole, that is, in the direction to cancel the axial misalignment between the press-fitted member and the press-fitted member. The component force for moving the press-fitting member can be made relatively larger than the frictional force generated on the contact surface between the work holding base and the press-fitted member.
Moreover, according to this method, in the above-described process, the pressing load applied to the press-fitting member can be reliably reduced by separating the press portion that is in contact with the press-fitting member from the press-fitting member. Further, when the pressing portion is separated from the press-fitting member in this way, the press-fitting member is urged against the press-fitted member by the pin on which the urging force of the elastic member acts. Since the biasing force of the elastic member is smaller than the press-fitting load, the frictional force generated between the press-fitted member and the work holding base can be sufficiently reduced. Further, the biasing force of the elastic member generates a component force to move the press-fit member in a direction to eliminate the axial misalignment between the press-fit member and the press-fit member in the tapered portion. Can be obtained.

The gist of the invention described in claim 2 is that, in the press-fitting method according to claim 1 , the pressing load is repeatedly reduced in the step.
According to this method, each time the pressing load is decreased, the press-fitted member moves in a direction in which the axial misalignment is eliminated, so that the aligning action by the tapered portion can be obtained more reliably.

The invention described in claim 3 is the press-fit method according to claim 1 or 2, prior SL are the holes formed in the press-fitting member, wherein the workpiece holder, the said hole of the press-fitting member A jig having an outer diameter smaller than the inner diameter is provided to enter and exit from the workpiece holder, and the gist is to insert the jig into the hole of the press-fitted member.

According to this method, since the jig is inserted into the hole formed in the press-fitted member, the displacement of the press-fitted member before press-fitting can be suppressed. Here, since the outer diameter of the jig is smaller than the inner diameter of the hole, the press-fitting member can move in a direction in which the axial misalignment is eliminated. Therefore, the centering action by the tapered portion can be obtained while suppressing the displacement of the member to be pressed before press-fitting. Since the jig inserted into the hole can enter and exit from the work holding table, the jig does not interfere with the press-fitting when the shaft is press-fitted into the hole.
In order to achieve the above object, an invention according to claim 4 is a method of press-fitting a shaft formed on one of a press-fitting member and a press-fitted member into a hole formed on the other, the tip of the shaft At least one of the peripheral edge of the portion and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole, and the press-fitting placed on the work holding base Before press-fitting the press-fitting member into the member, it is a component force generated in the tapered portion when the peripheral edge of the tip and the opening are in contact with the tapered portion, and the radius of the hole Performing a step of making the component force acting in the direction larger than the frictional force generated on the contact surface between the work holding base and the press-fit member, and in the step, the pressing load applied to the press-fit member is Lower than the pressing load of the And summary to make returns Ri.

In order to achieve the above object, the invention according to claim 5 is a method of press-fitting a shaft formed on one of the press-fitting member and the press-fitted member into a hole formed on the other, the tip of the shaft At least one of the peripheral edge of the portion and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole, and the press-fitting placed on the work holding base Before press-fitting the press-fitting member into the member, it is a component force generated in the tapered portion when the peripheral edge of the tip and the opening are in contact with the tapered portion, and the radius of the hole Performing a step of making the component force acting in the direction larger than the frictional force generated on the contact surface between the workpiece holding base and the press-fit member, and before the press-fit , the press-fit member is gripped by a chuck, The gist is to release the chuck after the step. To.

  According to this method, since the member to be pressed is held by the chuck before press-fitting, it is possible to suppress the displacement of the member to be pressed before press-fitting. On the other hand, since the chuck is released after the above-described steps, the press-fit member can move in a direction in which the axial misalignment is eliminated. Therefore, the centering action by the tapered portion can be obtained while suppressing the displacement of the member to be pressed before press-fitting.

  According to the present invention, the assembly accuracy of the press-fitting member and the press-fitted member can be improved.

Sectional drawing of the gear pump with which one Embodiment of the press-fitting method concerning this invention is applied. The front view of the shaft of the gear pump in the embodiment. Sectional drawing of the inner gear of the gear pump in the embodiment. Sectional drawing of the workpiece holding stand which mounts the press part and inner gear which press a shaft in the embodiment. It is sectional drawing which shows the process of the press injection method in the embodiment, Comprising: (A) is sectional drawing in a support process. (B) is sectional drawing in a contact process. (C) is sectional drawing in a load reduction process. (D) is sectional drawing in an insertion process. (E) is sectional drawing in a support cancellation process. The K section enlarged view of FIG. Sectional drawing which shows the one part process of the press injection method in the modification of the embodiment. It is sectional drawing which shows the holding | maintenance method of the inner gear in the modification of the embodiment, Comprising: (A) is sectional drawing before press-fitting. (B) is sectional drawing in a load reduction process. The expanded sectional view of the shaft in the modification of the embodiment. The expanded sectional view of the inner gear in the modification of the embodiment. Sectional drawing of the press-fitting member and the press-fitting member in the conventional press-fitting method. The schematic diagram which shows the state in which the assembly | attachment precision of a press-fit member and a press-fit member is falling in the conventional press-fit method.

  Hereinafter, an embodiment embodying a press-fitting method according to the present invention will be described with reference to FIGS. In the present embodiment, the press-fitting method according to the present invention is applied as a method of press-fitting a shaft provided in an inscribed gear pump into the inner gear.

FIG. 1 shows the structure of the gear pump. Since the structure of the inscribed gear pump is well known, an outline of the structure of the gear pump will be described below.
As shown in FIG. 1, the pump 1 includes a pump case 2 provided with an inscribed gear type pump mechanism. Fixed to the pump case 2 are a pump plate 4 on which a suction part and a discharge part of the pump mechanism are formed, and a motor case 5 formed in a substantially cylindrical shape. An electric motor, a control board 7 and the like are accommodated inside the motor case 5. A cover 8 formed in a substantially disc shape is attached to the opening end of the motor case 5. A stator 10 of an electric motor is fixed inside the motor case 5.

  A cylindrical support portion 11 is formed on the pump case 2. A rod-shaped shaft 13 is rotatably supported by the support portion 11 via a bearing 14. A rotor 12 that is a constituent member of the electric motor and faces the stator 10 is fixed to the shaft 13.

  A concave housing hole 2c that functions as a pump chamber is formed on the side surface of the pump case 2. An outer gear 20 having teeth formed on the inner periphery is rotatably accommodated in the accommodation hole 2c. The outer gear 20 is meshed with an inner gear 30 having teeth formed on the outer periphery. A press-fit hole 30 a is formed at the center of the inner gear 30. The shaft portion 13a of the shaft 13 is press-fitted into the press-fitting hole 30a. The opening surface of the accommodation hole 2 c is closed by the end surface 4 a of the pump plate 4.

  In this pump 1, when the electric motor rotates, the inner gear 30 fixed to the shaft 13 rotates. When the inner gear 30 rotates, the outer gear 20 in the accommodation hole 2 c rotates while meshing with the inner gear 30. Thus, when the outer gear 20 and the inner gear 30 rotate while meshing with each other, fluid is sucked from the suction portion formed in the pump plate 4 into the housing hole 2c, and the fluid sucked into the housing hole 2c is It discharges from the discharge part formed in the pump plate 4. FIG.

  By the way, a certain amount of clearance, so-called side clearance, is provided between the end face 30b of the inner gear 30 in the axial direction of the shaft 13 and the end face 4a of the pump plate 4 facing the end face 30b.

  Here, when the shaft portion 13a of the shaft 13 that is a press-fit member is press-fitted into the press-fit hole 30a of the inner gear 30 that is a press-fit member, the center axis of the shaft portion 13a and the center axis of the press-fit hole 30a are shifted. The assembly accuracy between the shaft 13 and the inner gear 30 may be lowered. More specifically, the accuracy of the perpendicularity of the end face 30b with respect to the central axis of the shaft 13 may be lowered. If the accuracy of the perpendicularity is low, the amount of deflection of the end face 30 b increases and the end face 30 b of the inner gear 30 comes into contact with the end face 4 a of the pump plate 4. Such contact between the inner gear 30 and the pump plate 4 can be avoided by increasing the above-described side clearance. However, when the side clearance is increased, the efficiency of the pump decreases.

  In addition, if the accuracy of the perpendicularity of the end face 30b with respect to the central axis of the shaft 13 is low, the end face in the radial direction of the inner gear 30, that is, the top face of the teeth of the inner gear 30, will swing when the inner gear 30 rotates. The tooth contact with 20 worsens. For this reason, for example, abnormal noise is generated or tooth wear is promoted.

  Therefore, in this embodiment, the shaft portion 13a of the shaft 13 and the press-fitting hole 30a of the inner gear 30 are provided with alignment tapers for aligning the respective shaft centers. And the assembly | attachment precision of the shaft 13 and the inner gear 30 is improved by press-fitting the axial part 13a of the shaft 13 to the press-fit hole 30a with the following method.

First, the shape of the shaft 13 will be described.
As shown in FIG. 2, the first recess 13 b that is coaxial with the central axis of the shaft 13 and formed in a conical shape is formed on the end surface in the axial direction of the shaft 13 and inserted into the press-fitting hole 30 a. Is provided. A second recess 13c that is coaxial with the central axis of the shaft 13 and formed in a conical shape also on the end surface in the axial direction of the shaft 13 and opposite to the end surface on which the first recess 13b is formed. Is provided. A shaft-side taper portion 13 d that is coaxial with the central axis of the shaft 13 is formed at the peripheral edge (corner portion) of the shaft portion 13 a that is press-fitted into the press-fitting hole 30 a in the shaft 13.

Next, the shape of the inner gear 30 will be described.
As shown in FIG. 3, the press-fit hole 30 a perpendicular to the end face 30 b of the inner gear 30 is formed at the center of the inner gear 30. The hole diameter of the press-fitting hole 30a is made smaller than the shaft diameter of the shaft part 13a by the press-fitting allowance. And the hole side taper part 30c is formed in the opening part of the press-fit hole 30a. The taper angle of the hole-side taper portion 30c is the same as the taper angle of the shaft-side taper portion 13d.

  Next, the structure of the work holding base 70 on which the pressing portion 50 and the inner gear 30 on which the pressing force 50 for pressing the shaft 13 into the press-fitting hole 30a is applied will be described.

  As shown in FIG. 4, the pressing portion 50 has a pressing surface 54 that abuts against the end surface of the shaft 13 and applies a press-fitting load. Inside the pressing portion 50, a hole 51 formed in the direction in which the press-fitting load is applied is provided. The hole 51 is provided with a first pin 52 that protrudes from the pressing surface 54 so as to advance and retract in the press-fitting load application direction. The tip 52a of the first pin 52 is conically sharpened with the central axis of the first pin 52 as the axis, and the inclination angle of the conical surface is the same as the inclination angle of the conical surface of the second recess 13c. Has been. In the hole 51, a first spring 53 is provided as an elastic member that biases the first pin 52 so that the tip 52 a of the first pin 52 protrudes from the pressing surface 54. The biasing force of the first spring 53 is set to be smaller than a press-fit load for press-fitting the shaft 13 into the inner gear 30.

  As shown in FIG. 4, a hole 71 is formed in the work holding base 70 on which the inner gear 30 is placed during press-fitting. The hole 71 is provided with a second pin 72 that enters and exits from the work holder 70. The outer diameter of the second pin 72 is smaller than the inner diameter of the press-fit hole 30a. The distal end portion 72a of the second pin 72 is pointed in a conical shape with the central axis of the second pin 72 as an axis, and the inclination angle of the conical surface is the same as the inclination angle of the conical surface of the first recess 13b. Are the same. A second spring 73 is provided in the hole 71 to urge the work pin 70 so that the second pin 72 protrudes from the mounting surface 74 with which the inner gear 30 contacts.

  As shown in FIG. 4, the hole 51 formed in the pressing portion 50, the first pin 52 provided in the hole 51, the hole 71 formed in the work holding base 70, and the hole 71 are provided. The second pin 72 is formed on the same axis.

Next, a method for press-fitting the shaft portion 13a of the shaft 13 into the press-fitting hole 30a of the inner gear 30 will be described with reference to FIG.
In the present embodiment, the press-fitting is completed by proceeding in the order of the support process, the contact process, the load reduction process, the insertion process, and the support release process.
(Support process)
In the support step shown in FIG. 5A, first, the inner gear 30 is placed on the work holding base 70 with the second pin 72 inserted into the press-fitting hole 30a of the inner gear 30. And while fitting the front-end | tip part 72a of the 2nd pin 72 to the 1st recessed part 13b of the shaft 13, the press part 50 is advanced, ie, the press part 50 in the direction (arrow G direction shown in FIG. 5) which approaches the work holding stand 70. To move the tip 52a of the first pin 52 into the second recess 13c of the shaft 13. Thereby, the shaft 13 is supported between the pressing portion 50 and the work holding base 70.
(Contact process)
When the support of the shaft 13 is completed in the support step, in the next contact step, as shown in FIG. 5B, the pressing portion 50 is further advanced, so that the pressing surface 54 of the pressing portion 50 is moved to the shaft. 13 is brought into contact with the end face. When the shaft side taper portion 13d of the shaft 13 and the hole side taper portion 30c of the inner gear 30 come into contact with each other, the forward movement of the pressing portion 50 is stopped. Note that the contact between the shaft-side tapered portion 13d and the hole-side tapered portion 30c may be detected by an appropriate method. For example, the load applied to the pressing portion 50 in order to move the pressing portion 50 in the direction approaching the work holding base 70 increases rapidly when the shaft-side taper portion 13d and the hole-side taper portion 30c come into contact with each other. Therefore, by detecting such a rapid change in load, it is possible to detect contact between the shaft-side tapered portion 13d and the hole-side tapered portion 30c. Alternatively, it is possible to estimate the contact between the shaft-side tapered portion 13d and the hole-side tapered portion 30c by measuring the amount of movement of the pressing portion 50 from the initial position.
(Load reduction process)
When the forward stop of the pressing portion 50 is completed in the contact step, in the next load reduction step, as shown in FIG. 5C, the pressing portion 50 is temporarily retracted, that is, in a direction away from the work holder 70. The pressing part 50 is once moved in the direction of arrow P in FIG. As a result, the pressing surface 54 that has been in contact with the end surface of the shaft 13 is separated from the shaft 13, so that the pressing load applied to the shaft 13 is lower than the pressing load at the time of press-fitting. Therefore, the pressing load acting on the tapered portions (shaft side tapered portion 13d and hole side tapered portion 30c) is also lower than the pressing load at the time of press-fitting. In this load reduction process, the retraction amount of the pressing portion 50 is determined so that the shaft 13 is urged to the inner gear 30 by the first pin 52 on which the urging force of the first spring 53 acts. As a result, the pressure applied to the shaft 13 while maintaining the state in which the peripheral edge of the tip of the shaft 13 is in contact with the opening of the press-fitting hole 30a at the tapered portions (shaft-side tapered portion 13d and hole-side tapered portion 30c). The load is lower than the press-fit load.
(Insertion process)
When the backward movement of the pressing portion 50 is completed in the load reducing step, in the next insertion step, as shown in FIG. 5D, the pressing portion 50 is advanced again so that the pressing surface 54 becomes the end surface of the shaft 13. By bringing the pressing portion 50 into contact with each other, the press-fitting of the shaft portion 13a into the press-fitting hole 30a is completed. The second pin 72 is configured to be able to enter and exit from the work holding base 70. Therefore, the second pin 72 is gradually pushed by the shaft portion 13a as the shaft portion 13a is inserted into the press-fitting hole 30a, and is accommodated in the hole 71 of the work holding base 70.
(Support release process)
When the press-fitting of the shaft portion 13a into the press-fitting hole 30a is completed in the insertion step, the pressing portion 50 is largely retracted in the next support release step, as shown in FIG. Thereby, the pressing surface 54 of the pressing portion 50 is separated from the end surface of the shaft 13. And the front-end | tip part 52a of the 1st pin 52 also leaves | separates from the 2nd recessed part 13c of the shaft 13, and the support of the shaft 13 is cancelled | released. After that, the inner gear 30 into which the shaft 13 is press-fitted is removed from the work holding base 70.

Next, the operation obtained by the press-fitting method of this embodiment will be described.
As shown in FIG. 6, also in this embodiment, in order to align the shaft center of the shaft portion 13a of the shaft 13 and the press-fitting hole 30a of the inner gear 30, a taper portion for alignment is provided. That is, the shaft side taper portion 13d is formed on the periphery of the tip portion of the shaft 13 which is a press-fitting member. The inner gear 30 that is a press-fitted member is formed with a press-fit hole 30a into which the shaft portion 13a of the shaft 13 is press-fitted, and a hole-side taper portion 30c is formed at the opening of the press-fit hole 30a. . The inner gear 30 is placed on the work holding table 70, and an end surface 30 b of the inner gear 30 that is orthogonal to the central axis of the press-fitting hole 30 a is in contact with the work holding table 70.

  When the shaft 13 is pressed against the inner gear 30 by the pressing force D in a state where the shaft-side taper portion 13d and the hole-side taper portion 30c are in contact with each other, the shaft-side taper portion 13d and the hole-side taper portion 30c are A first component force F1 that is a component force of the pressing force D and presses the inner gear 30 against the work holding base 70 acts on the contact portion S that is in contact with the contact portion S in the same manner as in the past. Further, the contact portion S has a component force of the pressing force D and a component force acting in the radial direction of the press-fitting hole 30a of the inner gear 30, that is, the inner gear 30 in a direction to eliminate the axial misalignment between the inner gear 30 and the shaft 13. The second component force F <b> 2 that moves is also the same as in the conventional case.

  Here, in the press-fitting method of the present embodiment, the above-described load reducing step is performed before the shaft 13 is press-fitted into the inner gear 30 in the insertion step. By performing this load reducing step, the pressing load applied to the shaft 13 becomes lower than the pressing load at the time of press-fitting, and the tip end periphery of the shaft portion 13a and the opening of the press-fitting hole 30a are tapered for alignment. The pressing load acting on the tapered portion when contacting at the portion (shaft-side tapered portion 13d and hole-side tapered portion 30c) is also lower than the pressing load at the time of press-fitting. Therefore, the first component force F1 that presses the inner gear 30 against the work holding base 70 is smaller than that of a conventional press-fitting method that does not reduce the pressing load before press-fitting. Therefore, the frictional force generated between the end surface 30b of the inner gear 30 and the mounting surface 74 of the work holding table 70 is also smaller than when the pressing load is not reduced. When the frictional force is reduced in this way, the second component force F2 is relatively larger than the frictional force generated between the end surface 30b of the inner gear 30 and the mounting surface 74 of the work holding base 70. Therefore, the inner gear 30 is easy to move in the direction (direction of arrow M shown in FIG. 6) in which the axial shift between the inner gear 30 and the shaft 13 is eliminated by the second component force F2, and the aligning action by the tapered portion is obtained. It becomes easy. Therefore, in the press-fitting process, the shaft 13a of the shaft 13 and the central axis of the press-fitting hole 30a of the inner gear 30 are easily aligned, and the assembly accuracy of the shaft 13 and the inner gear 30 is improved.

  Further, in the above-described load reduction process, the pressing portion 50 that has been in contact with the end surface of the shaft 13 is separated from the shaft 13, so that the pressing load applied to the shaft 13 is reliably reduced. . Further, when the pressing portion 50 is separated from the shaft 13 in this way, the shaft 13 is urged to the inner gear 30 by the first pin 52 on which the urging force H of the first spring 53 acts. Since the urging force H of the first spring 53 is smaller than the press-fitting load, the frictional force generated between the end surface 30b of the inner gear 30 and the mounting surface 74 of the work holding base 70 is sufficiently small. Further, the biasing force H of the first spring 53 is at the tapered portion (shaft side taper portion 13d and hole side taper portion 30c), that is, at the contact portion S where the shaft side taper portion 13d and the hole side taper portion 30c are in contact. Then, the second component force F2 that moves the inner gear 30 in the direction in which the axial misalignment between the inner gear 30 and the shaft 13 is eliminated is generated. Therefore, even when the press-fit load from the pressing portion 50 is reduced, the aligning action by the tapered portion can be obtained.

  Further, since the second pin 72 as a jig is inserted into the press-fitting hole 30a formed in the inner gear 30, it is possible to prevent the position of the inner gear 30 from being greatly displaced before press-fitting. Here, since the outer diameter of the second pin 72 is smaller than the inner diameter of the press-fitting hole 30a, the inner gear 30 moves in the direction in which the axial misalignment is eliminated (the direction in which the second component force F2 is applied). Can do. Therefore, the centering action by the tapered portion can be obtained while suppressing the displacement of the inner gear 30 before press-fitting. The second pin 72 inserted into the press-fitting hole 30a can enter and exit from the work holding base 70. In the insertion process, the insertion of the shaft portion 13a into the press-fitting hole 30a proceeds gradually. It is accommodated in the hole 71. Therefore, when the shaft portion 13a of the shaft 13 is press-fitted into the press-fitting hole 30a, the second pin 72 does not hinder press-fitting.

As described above, according to the present embodiment, the following effects can be obtained.
(1) A taper portion that aligns the central axis of the shaft portion 13a and the central axis of the press-fit hole 30a is formed at the peripheral edge of the shaft portion 13a of the shaft 13 and the opening portion of the press-fit hole 30a of the inner gear 30, respectively. Yes. Before the shaft 13 is press-fitted into the inner gear 30 placed on the work holding base 70, the peripheral edge of the tip portion of the shaft portion 13a and the opening portion of the press-fitting hole 30a are in contact with each other at the tapered portion. A step of making the second component force F2 that is a component force that is sometimes generated in the tapered portion and acts in the radial direction of the press-fitting hole 30a larger than the friction force that is generated on the contact surface between the workpiece holding base 70 and the inner gear 30. Like to do.

  Therefore, the second component force F <b> 2 that moves the inner gear 30 in the direction to eliminate the axial misalignment is larger than the frictional force between the work holding base 70 and the inner gear 30. Therefore, the inner gear 30 is likely to move in a direction in which the axial misalignment between the shaft portion 13a of the shaft 13 and the press-fitting hole 30a of the inner gear 30 is eliminated, and the alignment action by the tapered portion is easily obtained. Thus, according to the present embodiment, the center axis of the shaft portion 13a of the shaft 13 and the center axis of the press-fitting hole 30a of the inner gear 30 can easily coincide with each other in the press-fitting process, and the assembly accuracy between the shaft 13 and the inner gear 30 is improved. become.

  (2) As the process of making the second component force F2 larger than the frictional force, the load reducing process described above is performed. That is, the pressing load applied to the shaft 13 is made lower than the pressing load at the time of press-fitting. Therefore, the frictional force generated between the inner gear 30 and the work holding base 70 becomes smaller than that in the case where the pressing load is not reduced. Therefore, the second component force F2 can be made relatively larger than the frictional force generated on the contact surface between the inner gear 30 and the work holding base 70.

  (3) A pressing portion 50 that abuts on the shaft 13 and applies a press-fitting load, a first spring 53 that is provided in the pressing portion 50 and generates a biasing force smaller than the press-fitting load, and a pressing portion 50 that is provided on the pressing portion 50. A first pin 52 that biases the shaft 13 toward the inner gear 30 by the biasing force of one spring 53 is provided. In the load reduction process, the pressing portion 50 in contact with the shaft 13 is separated from the shaft 13 and the shaft 13 is urged toward the inner gear 30 by the first pin 52. As a result, the pressing load applied to the shaft 13 can be reliably reduced. Further, since the biasing force of the first spring 53 is smaller than the press-fit load, the frictional force generated on the contact surface between the inner gear 30 and the work holding base 70 can be sufficiently reduced. The urging force of the first spring 53 generates a second component force F2 that moves the inner gear 30 in a direction in which the axial misalignment between the shaft portion 13a and the press-fitting hole 30a is eliminated in the tapered portion. Alignment effect can be obtained.

  (4) A press-fitting hole 30 a is formed in the inner gear 30. The work holding table 70 is provided with a second pin 72 that enters and exits from the work holding table 70. The second pin 72 is inserted into the press-fitting hole 30a. Therefore, a large positional shift of the inner gear 30 can be suppressed before press-fitting. Further, since the outer diameter of the second pin 72 is smaller than the inner diameter of the press-fitting hole 30a, the inner gear 30 can move in a direction in which the axial misalignment is eliminated. Therefore, the centering action by the taper portion can be obtained while suppressing a large displacement of the inner gear 30 before press-fitting. In addition, since the 2nd pin 72 inserted in the press-fit hole 30a can enter / exit from a workpiece | work holding stand, when the axial part 13a is press-fit in the press-fit hole 30a, the 2nd pin 72 does not become a hindrance to press-fit.

In addition, the said embodiment can also be changed and implemented as follows.
-You may make it repeat a fall of a press load in a load reduction process. FIG. 7 shows an example of a load reduction process in this modification.

  As shown in FIG. 7, when the forward stop of the pressing portion 50 is completed in the contact step described above, in the load reducing step in this modification, first, as shown in (C1) of FIG. A backward stroke is performed in which the pressing portion 50 is moved backward in the direction away from the workpiece holding base 70 (in the direction of arrow P in FIG. 7). The retraction amount of the pressing portion 50 in the retreat stroke is also set so that the shaft 13 is urged to the inner gear 30 by the first pin 52 on which the urging force of the first spring 53 acts as in the above embodiment. By this retreating process, the pressing load is reduced while maintaining the state in which the peripheral edge of the tip end of the shaft 13 is in contact with the opening of the press-fitting hole 30a at the taper portions (shaft side taper portion 13d and hole side taper portion 30c). Is done.

  Next, as shown in (C2) of FIG. 7, the pressing portion 50 is moved forward, that is, the pressing portion 50 is moved in a direction approaching the work holding base 70 (in the direction of arrow G shown in FIG. 7). The pre-advance process is performed in contact with the end face of the shaft 13.

  Next, as shown in FIG. 7 (C3), the above-described backward stroke is performed again, then, as shown in FIG. 7 (C4), the above-described forward travel is performed again, and then (C5 in FIG. 7). ), The reverse stroke described above is performed again to complete the load reduction process. And after completing a load reduction process, the insertion process mentioned above is continued. In this modification, the backward stroke is performed three times (C1, C3, C5), but this number can be changed as appropriate.

  If the reduction of the pressing load is repeated in this manner, the inner gear 30 moves in a direction in which the axial misalignment is eliminated each time the pressing load is reduced, so that the aligning action by the tapered portion can be obtained more reliably. Be able to.

  -The position of the inner gear 30 during press-fitting is maintained by inserting the second pin 72 into the press-fitting hole 30a. In addition, in the load reduction process, the inner gear 30 may be held in another manner as long as the inner gear 30 can move in a direction in which the axial misalignment is eliminated. For example, as shown in FIG. 8A, the inner gear 30 is gripped by the chuck 500 before press-fitting. However, as shown in FIG. 8B, the gripping portion 510 of the chuck 500 is released after the load reducing step. According to this holding method, since the inner gear 30 is gripped by the chuck 500 before press-fitting, it is possible to reliably suppress the displacement of the inner gear 30 before press-fitting. On the other hand, since the gripping portion 510 provided in the chuck 500 is released after the load reducing step described above, the inner gear 30 can move in a direction in which the axial misalignment is eliminated. Therefore, it is possible to obtain the aligning action by the tapered portion while reliably suppressing the displacement of the inner gear 30 before the press-fitting.

  In the above-described load reduction process, the pressing portion 50 is retracted in order to reduce the pressing load while maintaining the state where the tip end periphery of the shaft portion 13a is in contact with the opening of the press-fitting hole 30a in the tapered portion. Thus, the pressing surface 54 is separated from the end surface of the shaft 13 and the shaft 13 is urged toward the inner gear 30 by the first pin 52. However, you may perform a load reduction process in this other aspect. For example, in a state where the pressing surface 54 of the pressing portion 50 is in contact with the end surface of the shaft 13, a pressing load applied to the shaft 13 from the pressing portion 50 is performed by moving the pressing portion 50 forward and backward with a minute stroke. It may be lowered.

  In the above embodiment, the shaft-side taper portion 13 d is formed on the periphery of the tip portion of the shaft portion 13 a of the shaft 13, and the hole-side taper portion 30 c is formed in the opening portion of the press-fitting hole 30 a of the inner gear 30. In addition, as shown in FIG. 9, only the shaft-side tapered portion 13d may be formed. Further, as shown in FIG. 10, only the hole-side tapered portion 30c may be formed.

  In the above embodiment, the shaft 13 is a press-fitting member, the inner gear 30 is a press-fitted member, and the shaft 13 is moved in the press-fitting direction with respect to the inner gear 30. In addition, the shaft 13 may be a press-fit member, the inner gear 30 may be a press-fit member, and the inner gear 30 may be moved relative to the shaft 13 in the press-fitting direction.

Although the spring is used as the elastic member that applies the urging force to the first pin 52 and the second pin 72, other elastic members such as rubber may be used.
In the above embodiment, as an example of the press-fitting method according to the present invention, the present invention is applied to a method of press-fitting the shaft 13 of the internal gear pump into the inner gear 30. However, the application object of the present invention is not limited to the press-fitting method of the shaft 13 and the inner gear 30, and can also be applied to a method of press-fitting other press-fitting members into the press-fitted member.

  In order to make the second component force F2 larger than the frictional force generated on the contact surface between the work holding base 70 and the inner gear 30, the load reducing step is performed. F2 may be made larger than the frictional force.

  DESCRIPTION OF SYMBOLS 1 ... Pump, 2 ... Pump case, 2c ... Accommodating hole, 4 ... Pump plate, 4a ... End face, 5 ... Motor case, 6 ... Electric motor, 7 ... Control board, 8 ... Cover, 10 ... Stator, 11 ... Support part , 12 ... rotor, 13 ... shaft, 13a ... shaft portion, 13b ... first recess, 13c ... second recess, 13d ... shaft side taper portion, 14 ... bearing, 20 ... outer gear, 30 ... inner gear, 30a ... press-fitting hole, 30b ... End face, 30c ... Hole side taper part, 50 ... Press part, 51 ... Hole, 52 ... First pin, 52a ... Tip part, 53 ... First spring, 54 ... Press surface, 70 ... Work holding base, 71 ... Hole 72, second pin, 72a, tip portion, 73, second spring, 74, mounting surface, 100, press-fitting member, 100a, shaft side taper portion, 200, press-fit member, 200a, hole side taper portion, 200b ... hole, 2 0c ... end face, 400 ... work holding base, 500 ... chuck, 510 ... grip portion.

Claims (5)

A method of press-fitting a shaft formed on one of a press-fitting member and a press-fitted member into a hole formed on the other,
At least one of the peripheral edge of the shaft and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole,
Before the press-fitting member is press-fitted into the press-fitting member placed on the work holding base, the tip portion peripheral edge and the opening portion are in contact with the tapered portion. the component force acting in a radial direction of the hole a force component occurs, have rows step be greater than the frictional force generated at the contact surface between the pressed insertion member and the workpiece holding table,
A pressing portion that abuts against the press-fitting member and applies a press-fitting load;
An elastic member that is provided in the pressing portion and generates an urging force smaller than the press-fit load;
A pin that is provided at the pressing portion and biases the press-fitting member against the press-fitted member by the biasing force of the elastic member;
In the step, the pressing load applied to the press-fitting member is made lower than the pressing load at the time of press-fitting, and the pressing part that is in contact with the press-fitting member is separated from the press-fitting member and the press-fitting member is moved by the pin. A press- fitting method for urging the press- fitted member . The press-fitting method according to claim 1, wherein the pressing load is repeatedly reduced in the step. The hole is formed in the pressed-in member;
The work holding table is provided with a jig that has an outer diameter smaller than the inner diameter of the hole of the press-fitting member and enters and exits from the work holding table,
The method of press fitting according to claim 1 or 2 for inserting the jig the into the hole of the press-fitting member. A method of press-fitting a shaft formed on one of a press-fitting member and a press-fitted member into a hole formed on the other,
  At least one of the peripheral edge of the shaft and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole,
  Before the press-fitting member is press-fitted into the press-fitting member placed on the work holding base, the tip portion peripheral edge and the opening portion are in contact with the tapered portion. Performing a step of making the component force generated and acting in the radial direction of the hole larger than the frictional force generated on the contact surface between the work holding base and the press-fit member;
  In the step, the pressing load applied to the press-fitting member is made lower than the pressing load at the time of press-fitting, and the pressing load is repeatedly reduced.
  Press-in method. A method of press-fitting a shaft formed on one of a press-fitting member and a press-fitted member into a hole formed on the other,
  At least one of the peripheral edge of the shaft and the opening of the hole is formed with a tapered portion that aligns the central axis of the shaft and the central axis of the hole,
  Before the press-fitting member is press-fitted into the press-fitting member placed on the work holding base, the tip portion peripheral edge and the opening portion are in contact with the tapered portion. Performing a step of making the component force generated and acting in the radial direction of the hole larger than the frictional force generated on the contact surface between the work holding base and the press-fit member;
  Before press-fitting, the press-fitting member is held by a chuck, and the chuck is released after the step.
  Press-in method.