JP4244085B2 - Press-fitting device and press-fitting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a press-fitting device and a press-fitting method, and more particularly to a press-fitting device and a press-fitting method suitable for press-fitting another member into a member having low rigidity.
[0002]
[Prior art]
As a device that couples two members by press-fitting, a press-fitting device that applies a load in a press-fitting direction until a predetermined press-fitting depth is obtained while measuring the press-fitting depth is known.
When such a press-fitting device is used to press-fit another member (hereinafter referred to as “receiving member” as the first member and “separate member” as the second member) into the receiving member having low rigidity. So-called stick-slip occurs due to the frictional force between them. In a stick state where the members do not slip due to the frictional force between the members, the energy for press-fitting the second member is accumulated as the elastic energy of the first member. When elastic energy is accumulated in the first member and the elastic force of the member exceeds the frictional force, the members begin to slip and shift to a slip state.
[0003]
For example, when the position of the end face on the second member side of the first member in a state where no press-fitting load is applied is used as a reference, the load applied in the press-fitting direction increases with time as shown by a straight line 101 in FIG. In addition, the displacement of the second member increases with time. On the other hand, as shown by a curve 102 in FIG. 3A, the elastic deformation causes the first member to be distorted in the press-fit axis direction. In this case, the difference between the displacement of the second member and the distortion of the first member is approximately equal to the press-fit depth. Therefore, as shown in the curve of FIG. 3B, the press-fitting depth increases irregularly over time.
[0004]
[Problems to be solved by the invention]
However, since the moment of transition from the stick state to the slip state is unpredictable and the slip amount between the members in the slip state is not constant, conventionally, when the second member is press-fitted into the first member having low rigidity, the unit is μm. It was difficult to adjust the press-in depth. That is, when a load is applied in the press-fitting direction while measuring the press-fitting depth, and a stick state occurs immediately before a predetermined press-fitting depth is obtained, increasing the force applied in the press-fitting direction until the press-fitting depth begins to increase again. There has been a problem that the slip state is entered at a certain moment, and a position deeper than a predetermined press-fit depth is pressed at once.
The present invention has been made to solve such a problem, and an object thereof is to provide a press-fitting device and a press-fitting method that improve the accuracy of the press-fitting depth.
[0005]
[Means for Solving the Problems]
According to the press-fitting device of the first aspect of the present invention, since the clamp is provided to compress the side wall of the cylindrical opening of the first member in the press-fitting axis direction and sandwich the first member, the transition from the stick state to the slip state is provided. The elastic energy required for the first member can be stored in advance in the first member. Therefore, before or immediately after the first member is elastically deformed by the friction between the side wall of the cylindrical opening and the outer wall of the second member, the members slide by the elastic energy stored in advance. Therefore, there is no transition to the stick state, or the period of the stick state is very short. Since the second member is press-fitted into the cylindrical opening by the press-fitting means in a state in which stick-slip hardly occurs, the press-fitting can be accurately performed to a predetermined depth.
[0006]
According to the press-fitting method according to claim 2 of the present invention, the method includes the step of clamping the first member by compressing the side wall of the cylindrical opening in the press-fitting axis direction, and is necessary for shifting from the stick state to the slip state. Elastic energy can be stored in the first member in advance. Therefore, before or immediately after the first member is elastically deformed by the friction between the side wall of the cylindrical opening and the outer wall of the second member, the members slide by the elastic energy stored in advance. Therefore, there is no transition to the stick state, or the period of the stick state is very short. By performing the step of press-fitting the second member into the cylindrical opening in a state where stick-slip hardly occurs, the press-fitting can be accurately performed to a predetermined depth.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plurality of examples showing embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A press-fitting device according to a first embodiment of the present invention is shown in FIG. The press-fitting device 1 press-fits the second member 3 into the clamp 10 that sandwiches the first member 2 that is the receiving member, and the cylindrical opening 4 of the first member 2. And press-fitting means 20 for joining the two. In the following description, the first member 2 is assumed to be a metal having lower rigidity than the second member 3.
[0010]
The clamp 10 clamps the first member 2 between the clamp body 11 and the contact member 16 by screwing a screw 15 into the clamp body 11 with a servo motor 13.
The end of the clamp body 11 and the contact member 16 are in contact with the edge of the cylindrical opening 4. A contact member 16 is provided at one end of the screw 15 and a gear 14 is provided at the other end. As the gear 12 meshes with the gear 14 and the servo motor 13 rotates, the screw 15 rotates. By controlling the rotation of the servo motor 13, the set load for holding the first member 2 is determined. The set load is measured by a load transducer 17 provided between the screw 15 and the contact member 16. The set load measured by the load converter 17 is fed back to the rotation of the servo motor 13 via the control device 28. The set load can be applied by a coil spring or the like. In addition, when applying a set load with a coil spring etc., it is necessary to fix the contact member 16 in the position where the predetermined load was applied. It is also possible to apply a set load from the same direction as the screw 23.
[0011]
The press-fitting means 20 press-fits the second member 3 into the cylindrical opening 4 of the first member 2 by screwing a screw 23 into the screw base 22 with a servo motor 26.
One end of the screw 23 is in contact with the second member 3, and the gear 21 is provided at the other end. The screw base 22 and the clamp body 11 are fixed to a housing (not shown). As the gear 27 meshes with the gear 21 and the servo motor 26 rotates, the screw 23 rotates. The rod 24 is in contact with the opposite side of the screw 23 of the second member 3. The displacement of the rod 24 in the press-fitting axis direction is measured by the length measuring device 25. The press-fitting depth of the second member 3 measured by the length measuring device 25 is fed back to the rotation of the servo motor 26 via the control device 28.
[0012]
Hereinafter, a method of joining the first member 2 and the second member 3 by press-fitting using the press-fitting device 1 will be described.
The maximum press-fit load that can be applied to the first member 2 via the second member 3 is measured in advance. The maximum press-fit load is the maximum load in the press-fit axis direction that the first member 2 can withstand within elastic deformation. The clamp 10 compresses the side wall of the cylindrical opening 4 of the first member 2 in the press-fitting axis direction so as to sandwich the first member 2. At this time, while measuring the set load by the load converter 17, the servo motor 13 is controlled so that the set load is substantially the same as the previously measured maximum press-fitting load, and the first member 2 is clamped. Elastic energy is accumulated in the first member 2 by the set load.
[0013]
The method of press-fitting the second member 3 by the press-fitting means 20 after the first member 2 is sandwiched between the clamps 10 is the same as the conventional method. That is, the screw 23 is screwed by the servo motor 26 to a position where a predetermined press-fitting depth is obtained by the length measuring device 25, and the first member 2 and the second member 3 are coupled.
[0014]
According to the conventional press-fitting method for press-fitting the side wall of the cylindrical opening 4 without applying a set load in the press-fitting axis direction, stick slip occurs when the rigidity of the first member 2 is low. That is, when the first member 2 and the second member 3 do not slip due to the frictional force generated between the side wall of the cylindrical opening 4 and the outer peripheral surface of the second member 3, the press-fit load applied by the screw 23 is the first When the elastic force of the first member 2 is accumulated as the elastic energy of the member 2 and exceeds the frictional force, both members slide at once.
[0015]
On the other hand, when press-fitting using the press-fitting device of the present embodiment, elastic energy can be stored in advance in the first member 2 by the clamp 10. Since this elastic energy is accumulated by applying substantially the same set load as the maximum press-fitting load, the elastic force of the first member 2 is generated between the side wall of the cylindrical opening 4 and the outer peripheral surface of the second member 3. It can be said that it is always larger than the friction force generated between them. Therefore, the frictional force does not overcome the elastic force of the first member 2 and the first member 2 is not further distorted in the press-fit axis direction from the state where the set load is applied. That is, stick slip cannot occur during press-fitting.
[0016]
As described above, according to the press-fitting device of this embodiment, since stick-slip does not occur at the time of press-fitting, the press-fitting depth increases in proportion to the rotation speed of the servo motor 26, and the second press-fitting depth is accurately set to the predetermined press-fitting depth. The member 3 can be press-fitted.
[0017]
( First Reference Example )
A press-fitting device according to a first reference example of the present invention is shown in FIG. Parts substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
A vibration unit 30 is provided at the end of the press-fitting means 20 on the second member 3 side. The vibration unit 30 is a device for applying high-frequency vibration to the second member 3.
[0018]
The vibration unit 30 has an opening formed at the end of the bottomed cylindrical vibration unit housing 31 on the second member 3 side, and a support member 35 is provided at the opening. The support member 35 supports the contact member 34 so as to be reciprocally movable. The contact member 34 is a cylindrical member having a flange 36 formed at one end. A coil spring 33 is provided in the axial gap between the flange 36 and the vibration unit housing 31 to urge the contact member 34 upward in FIG. A piezoelectric element actuator 32 is provided inside the vibration unit housing 31. The vibration end of the piezoelectric element actuator 32 is in contact with the end of the contact member 34 on the flange 36 side. The contact member 16 that holds the first member 2 and the screw base 22 are fixed to a housing (not shown).
[0019]
When the first member 2 and the second member 3 are joined by press-fitting using the press-fitting device 5, a predetermined voltage is applied by the control device 27 and the piezoelectric element actuator 32 is vibrated with an amplitude of 1 μm and a frequency of 1 kHz, while the servo motor 26 Then, the screw 23 is screwed and the second member 3 is press-fitted into the cylindrical opening 4 of the first member 2.
When the friction between the side wall of the cylindrical opening 4 and the outer peripheral surface of the second member 3 is large, the press-fitting load applied to the second member 3 by the servo motor 26 acts as a force for elastically deforming the first member 2.
[0020]
On the other hand, when the piezoelectric element extends in the press-fitting axis direction, a force is generated to push the contact member 34 downward in FIG. This force is concentrated in a very short time and is transmitted to the second member 3 via the contact member 34. Since the impulse given to the second member 3 within the period during which the piezoelectric element extends is larger than the impulse given within the same period without using the piezoelectric element actuator 32, the members easily slip. That is, the amount of strain due to elastic deformation cannot catch up with the movement displacement of the second member 3 in the press-fitting direction, and the second member 3 moves in the press-fitting direction when the first member 2 and the second member 3 slide.
[0021]
When the piezoelectric element contracts in the press-fitting axis direction, the press-fitting load is released, so that the displacement of the second member 3 in the press-fitting direction does not occur during the contraction period. Therefore, the elastic deformation of the first member 2 does not occur during the contraction period.
Therefore, when the second member 3 is press-fitted into the first member 2, the vibration of the piezoelectric element actuator 32 depends on whether the second member 3 slides on the side wall of the cylindrical opening 4 of the first member 2 or not. It happens alternately in synchronism. The amount of slip when both members slide can be reduced in accordance with the amplitude of the piezoelectric element actuator 32 by controlling the voltage applied to the piezoelectric element. In this embodiment, since the amplitude is 1 μm, the press-fitting depth of the first member 2 can be adjusted in units of 1 μm.
[0022]
As described above, according to the press-fitting device 5 according to the first reference example of the present invention, the first member 2 and the second member 3 slide periodically, and the slip amount can be controlled. By making it smaller, the second member 3 can be accurately press-fitted to a predetermined depth.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a press-fitting device according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing a press-fitting device according to a first reference example of the present invention.
FIG. 3 is a graph for explaining a relationship between a press-fitting time and a press-fitting depth by a conventional press-fitting method. (A) shows the relationship between the amount of distortion of the receiving member and the movement displacement of the separate member, and (B) shows the relationship between the press-fitting time and the press-fit depth of the separate member.

Claims (2)

An apparatus for press-fitting the second member into the cylindrical opening of the first member,
A clamp that compresses the side wall of the cylindrical opening in the press-fitting axis direction by applying the same set load as the maximum load that the first member can withstand within elastic deformation, and sandwiches the first member;
Press-fitting means for press-fitting the second member into the cylindrical opening;
A press-fitting device comprising: A method of press-fitting the second member into the cylindrical opening of the first member,
Compressing the side wall of the cylindrical opening in the press-fitting axis direction by applying the same set load as the maximum load that the first member can withstand within elastic deformation, and clamping the first member;
Press-fitting the second member into the cylindrical opening of the clamped first member;
The press-fitting method characterized by including.

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