JPH06210505A - Spindle hole processing method - Google Patents

Abstract

PURPOSE:To regulate the bending of an arbor and improve processing precision by supporting both ends of the arbor by means of a pair of arbor supports in the case of a method which processes simultaneously plural spindle holes by means of the boring arbor provided with plural cutting tools along the spindle direction. CONSTITUTION:In a case in which a boring arbor 4 fitted with plural (5 pieces in the case of the drawing) cutting tools 3 along a spindle direction is rotated by means of a motor 5 and the cutting processing of the bearing holes 2... of a cylinder head W that is a work is conducted simultaneously by means of respective cutting tools 3, both end portions of the arbor 4 are supported by means of the upper and lower arbor supports 7, 8. Also, at the arbor 4, a balancing portion is formed by cutting out by a predetermined quantity the opposite side surface to surface provided with cutting tools 3. As weight around an axis becomes unbalanced due to this balancing portion, centrifugal force is generated at the time of arbor rotation, and a resultant force is formed by this centrifugal force and the back partial force of the cutting resistance of the cutting tools 3, and the bending of the arbor 4 is regulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simultaneously machining a plurality of shaft holes such as line boring.

[0002]

2. Description of the Related Art Conventionally, both ends of a boring arbor provided with a plurality of cutting tools along the axial direction are supported by a pair of arbor supports, and the boring arbor is advanced by a feed unit while being rotated by a motor. A method of simultaneously processing holes is known.

As a device for machining a shaft hole as described above, for example, as shown in FIG. 7, a base end of a boring arbor 71 is fixed to a drive shaft 74 of a motor 73 through a shaft joint 72, and the boring arbor 71 is fixed. There is a device in which the tip and the root of the are supported by a pair of left and right arbor supports 75. The arbor support 75 is configured to include a bush 78 in a housing 76 via a bearing 77.
The bowling arbor 71 is inserted into the bush 78,
The boring arbor 71 and the bush 78 are arranged so that the boring arbor 71 can slide with respect to the bush 78.
A gap of 5 to 10 μm is provided between and.

In the apparatus shown in FIG. 7, the boring arbor 71 is used.
When the feed unit moves forward while rotating the motor 73 with the motor 73, the plurality of cutting tools 79 provided along the axial direction of the boring arbor 71 move forward while rotating, and thus the bearings provided on the work W on the table 80. Inner surface of hole 8
1 can be boring processed.

However, when the inner peripheral surface 81 of the bearing hole is bored by the above apparatus, the boring arbor 71 bends due to the back force of the cutting resistance received when the cutting tool 79 cuts the work W, and the amount of bending changes. Therefore, there is an inconvenience that machining accuracy such as roundness and surface roughness of the shaft hole is reduced.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a shaft hole machining method which eliminates such inconvenience and can obtain excellent machining accuracy.

[0007]

In order to achieve the above object, in the axial hole drilling method of the present invention, at least the tip of a boring arbor provided with a plurality of cutting tools along the axial direction is supported by an arbor support. In a method of machining a shaft hole in which a plurality of shaft holes are simultaneously cut by rotating the boring arbor in a state, a centrifugal force generated when the boring arbor is rotated and the boring arbor is rotated, The back force of the cutting resistance received by the tool forms a resultant force that brings the boring arbor into contact with the arbor support, and restricts the deflection of the boring arbor.

Further, the axial hole machining method of the present invention is characterized in that the boring arbor is supported at both ends thereof by a pair of arbor supports.

[0009]

According to the shaft hole machining method of the present invention, by machining the boring arbor, the centrifugal force generated when the boring arbor rotates, and the back force of the cutting resistance received by the boring arbor, A resultant force is formed to bring the boring arbor into contact with the arbor support. As a result, when the shaft hole is processed by the boring arbor, the boring arbor is in contact with the arbor support, and the bending of the boring arbor is restricted. Therefore, the amount of change in the deflection of the boring arbor is reduced, and the contact amount of the cutting tool with the inner peripheral surface of the shaft hole becomes substantially constant, so that the machining accuracy of the shaft hole is improved.

In the axial hole machining method of the present invention, when the boring arbor is supported at its both ends by a pair of arbor supports, the boring arbor has an inner circumference of the arbor support at its tip and near the base end. It comes into contact with the surface. As a result, the amount of change in the deflection of the boring arbor is further reduced, and the machining accuracy is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The shaft hole machining method of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a schematic view of a shaft hole drilling device used in the method of the present embodiment, FIG. 2 is an explanatory sectional view of a boring arbor, and FIG. 3 is a flexible shaft coupling used in the shaft hole drilling device shown in FIG. 3 is a schematic diagram, FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3, FIG. 5 is a graph showing the relationship between the force applied to the boring arbor and the amount of deflection, and FIG. 6 is an explanatory sectional view showing the state of the boring arbor and the arbor support. Is.

The axial hole drilling method of this embodiment uses the axial hole drilling apparatus 1 shown in FIG. 1 to perform boring of five crank journal bearing holes 2 provided in a cylinder head (workpiece) W. To do.

The shaft hole machining apparatus 1 comprises a boring arbor 4 provided with five cutting tools 3 along the axial direction, and a rotary drive motor 5 for rotating the boring arbor 4 around an axis. In the vicinity of its base end, it is supported by the upper arbor support 7 via the positioning member 6, and the tip is supported by the lower arbor support 8 and held in the vertical direction. By holding the boring arbor 4 vertically as described above, the boring arbor 4 does not bend due to its own weight unlike the case where the boring arbor 4 is held horizontally. A bearing 6a is provided between the positioning member 6 and the boring arbor 4, and the boring arbor 4 is rotatable along the inner peripheral surface of the positioning member 6.

The bowling arbor 4 is, as shown in FIG.
On the surface opposite to the surface on which the cutting tool 3 is provided with respect to the shaft, a balancing portion G is provided by electric discharge machining, drilling by a drill, grinding, or the like. The boring arbor 4 has an unbalanced weight around the shaft due to the balancer G, so that the centrifugal force F ₀ is generated when the boring arbor 4 rotates.
This centrifugal force F ₀ and the back force F ′ of the cutting resistance that the cutting tool 3 receives when cutting the inner peripheral surface of the bearing hole 2 form a resultant force F in the same direction, and the boring arbor 4 is arbored. The deflection of the bowling arbor 4 is regulated by abutting against the supports 7 and 8.

As shown in FIG. 1, the base end of the boring arbor 4 is connected to the drive shaft 10 of the rotary drive motor 5 via a flexible shaft joint 9. The rotary drive motor 5 is held by an elevating table 14 screwed to a feed screw rod 13 provided on an upper side surface of a cylindrical frame 12 erected on a base plate 11. It is provided so as to be vertically movable by rotationally driving the feed motor 15 provided on the upper portion.

The upper arbor support 7 and the lower arbor support 8 are provided so as to horizontally project from above and below a support member 17 attached to a frame 12 via a holding cylinder 16. A support hole 18 for supporting the boring arbor 4 is formed in the upper arbor support 7 with its axis oriented in the vertical direction, and a positioning member 6 for the boring arbor 4 is attached to a bush 19 fitted in the support hole 18. It can be inserted with a gap of 10 μm. Further, a support hole 20 for supporting the boring arbor 4 is formed in the lower arbor support 8 with its axis aligned with the axis of the support hole 18 in the vertical direction, and the bush 21 fitted into the support hole 20 is formed. The tip of the boring arbor 4 can be fitted and inserted with a gap of 5 to 10 μm.

Further, the support member 17 has a stopper 24 for preventing the cylinder head W from moving toward the frame 12 side.
Is provided.

As shown in FIG. 2, each of the cutting tools 3 is provided with an angular phase difference of 20 ° in the circumferential direction of the boring arbor 4. According to the boring arbor 4 in which the respective cutting tools 3 are arranged in this way, the cutting resistance R is distributed in the direction in which the respective cutting tools 3 on the boring arbor 4 are provided, and chipping of the cutting tools is reduced,
It is possible to improve processing accuracy such as roundness and surface roughness of the bearing hole 2.

The flexible shaft coupling 9 is integrally cut from a block-shaped metal material, and as shown in FIG.
The upper connecting member 31 and the partition member 32 are connected by a pair of rectangular thin plates 33, 33, while the partition member 32 and the lower connecting member 34 are connected by a pair of rectangular thin plates 35, 35. ing.

The upper connecting member 31, the partition member 32, and the lower connecting member 34 have the same axis, and as shown in FIG.
The thin plates 33, 33 and the thin plates 35, 35 are arranged parallel to each other with the axis line interposed therebetween. Also, thin plate 3
3, 33 and the thin plates 35, 35 are arranged so as to face each other at right angles. Thin plates 33, 33 and thin plates 35, 3
5 is provided with spring elasticity by subjecting the flexible shaft coupling 9 cut into the above shape to quenching treatment, and constitutes an upper elastic member 36 and a lower elastic member 37, respectively.
The flexible shaft coupling 9 is, as shown in FIG.
Is fixed to the drive shaft 10 via a flange 25, and the lower connecting member 34 is connected to the boring arbor 4 via a flange 26.
It is fixed to.

In the shaft hole machining apparatus 1 of this embodiment, the work supporting member 27 is provided so as to face the supporting member 17.
The work supporting member 27 is movable back and forth in the horizontal direction with the axis of the bearing hole 2 of the cylinder head W oriented in the vertical direction.

Next, the axial hole machining method of this embodiment using the axial hole machining apparatus 1 will be described.

First, in the initial state, the boring arbor 4 stands by above the upper arbor support 7, and the bite 3 is directed to the cylinder head W side.

Next, the cylinder head W is moved forward toward the frame 12 by the work supporting member 27 and moved to a predetermined position where the boring arbor 4 is inserted. At the above position, the axis of the bearing hole 2 of the cylinder head W is slightly eccentric to the work supporting member 27 side than the axes of the upper arbor support 7 and the lower arbor support 8.

Then, the feed motor 15 is operated to lower the elevating table 14 and insert the boring arbor 4 into the bearing hole 2 of the cylinder head W. Since the axis of the bearing hole 2 is eccentric to the work supporting member 27 side as described above, the boring arbor 4 can be inserted without the bite 3 interfering with the bearing hole 2.

Then, the positioning member 6 of the boring arbor 4 is fitted in the upper arbor support 7, and the tip of the boring arbor 4 is fitted in the lower arbor support 8. The axis of the drive shaft 10 does not necessarily coincide with the axes of the upper arbor support 7 and the lower arbor support 8, and the respective axes may be eccentric or have a declination, but the boring arbor 4 has a flexible shaft coupling 9 Since it is connected to the drive shaft 10 via the elastic member 36, 3
The boring arbor 4 is smoothly inserted into the upper arbor support 7 and the lower arbor support 8 by being easily absorbed by the elastic deformation of 7. Therefore, the boring arbor 4 is held in an appropriate posture with respect to each bearing hole 2 of the cylinder head W by the upper arbor support 7 and the lower arbor support 8. For the descent of the bowling arbor 4, each byte 3 is shown in Fig. 1.
As shown, the cylinder head W is stopped in a state of being positioned above each bearing hole 2.

Next, the cylinder head W is further moved toward the frame 12 by the work supporting member 27 and the stopper 24.
Is moved forward until it comes into contact with, and is moved to a predetermined processing position. At the above-mentioned position, the cylinder head W is fixed by a positioning pin or the like not shown, and is held so that the axis of the bearing hole 2 is aligned with the axes of the upper arbor support 7 and the lower arbor support 8.

Next, the rotary drive motor 5 and the feed motor 15 are operated to lower the boring arbor 4 along the feed screw rod 13 while rotating the boring arbor 4, so that the inner peripheral surface of each bearing hole 2 of the cylinder head W is moved. Boring.
The processing is, for example, a boring arbor 4 having an outer diameter of 45 mm.
Rotation speed 2400 rpm, feed speed 0.08 mm
It is performed under the condition of / rev.

During the above processing, the boring arbor 4 is
The balancer G shown in Fig. 2 is provided to reduce the weight around the shaft.
Is unbalanced, so centrifuge
Force F ₀And this centrifugal force F₀And bite 3 of bearing hole 2
The back force F'of the cutting resistance received when cutting the inner peripheral surface is
A resultant force F in the same direction is formed. Because of this, bowling
The bar 4 is brought into contact with the arbor supports 7 and 8 and its deflection is
It is regulated and the amount of change in the deflection is reduced. This conclusion
As a result, the bite 3 is brought into stable contact with the inner peripheral surface of the bearing hole 2.
And the cutting amount becomes almost constant.
Excellent processing accuracy can be obtained in terms of degree, surface roughness and the like.

Next, the balance portion G provided in the boring arbor 4 and the state of the deflection of the boring arbor 4 will be described with reference to FIGS. 2, 5 and 6.

When the boring process is performed by the axial hole machining apparatus 1 as described above, a back force F'acts from the work W of the boring arbor 4 toward the frame 12 as shown in FIG. In the example, the surface opposite to the surface on which the bite 3 is provided with respect to the axis of the boring arbor 4 having an outer diameter of 45 mm is ground by 5 g, and the balancer G shown in FIG. 2 is provided to give an unbalance amount m. However, a centrifugal force F ₀ that forms a resultant force F in the same direction as the back force F ′ is generated.

The centrifugal force F _{0 with} respect to the unbalance amount m is expressed by F ₀ = mrω ² = mr (2πN / 60) ² (ω: angular velocity, N: rotational speed) (1). ), M = 0.005 kg, N
= 2400 rpm, r = 0.0225m,
F ₀ ≈7 kgf.

As shown in FIG. 2, the back force F'is the resultant force of the back force F _n generated in the above direction from the cutting resistance R acting on each cutting tool 3, and the back force of each cutting tool 3 is obtained. When F _n is the back force components F _{1 to} F ₅ from the left of FIG. 2, F ′ = F ₁ + F ₂ + F ₃ + F ₄ + F ₅ (2)

Explaining the back force F _n using the center bite 3 as an example, the cutting resistance R acting on the bite 3 is a component force Rt directed from the bite 3 in the axial direction and a main component directed tangentially to the outer circumference of the boring arbor 4. Divided into force Rc, of which byte 3
The component force Rt from the axial direction is the back component force F ₃ .
The main component Rc causes the boring arbor 4 to generate a torsion moment.

Since each bite 3 is provided with an angular phase difference of 20 ° in the circumferential direction of the boring arbor 4, the back force components F _{1 to} F ₅ are expressed as follows using the component force Rt. It

F ₃ = Rt (3) F ₂ = F ₄ = Rt · cos 20 ° (4) F ₁ = F ₅ = Rt · cos 40 ° (5) The machining is performed under the above conditions (outside the boring arbor 4). Diameter 45m
m, rotation speed 2400 rpm, feed rate 0.08 mm / r
When performing in ev), Rt = 3 kgf, so F '= 13 kgf from equations (2) to (5).

Therefore, centrifugal force F ₀ and boring arbor 4
The total force F formed from the back force F'acting on F = F '+
F ₀ ≈20 kgf.

By the way, the boring arbor 4 is bent by an external force when the boring arbor 4 performs the boring process of the bearing hole 2 by abutting the inner peripheral surface of the bearing hole 2 of the work W and cutting. The deflection changes depending on the magnitude of the external force, but as shown in FIG. 5, the external force is within a certain range around 20 kgf (15 to 25 kgf in the graph of FIG. 5).
When it is, the amount of change is small.

In the axial hole machining method of this embodiment, the centrifugal force F ₀ generated when the boring arbor 4 is machined as described above and the boring arbor 4 rotates is about 20 kgf in the same direction as the back force F ′. As a result, the resultant force F acts as the external force, and when boring the bearing hole 2 of the cylinder head W is performed under the above conditions, the boring arbor 4 moves as shown in FIG. Then, the arbor supports 7 and 8 are contacted at four points A, B, C, and D to restrict the change. As a result, since the amount of change in deflection is reduced, the amount of contact of the cutting tool 3 with the bearing hole 2 becomes substantially constant, and the machining accuracy of the bearing hole 2 such as the roundness and surface roughness is stabilized.

When the boring process of the bearing hole 2 of the cylinder head W was carried out under the above-mentioned conditions by the method of boring the shaft hole of the present embodiment, the average roundness value was 2.26 μm (the difference between the maximum value and the minimum value). : 0.78 μm), average surface roughness 3.63 μm
(Difference between the maximum value and the minimum value: 1.55 μm), excellent processing accuracy was obtained.

The unbalance amount m given by the balancer G is that the resultant force F formed by the centrifugal force F ₀ and the back force F ′ causes the boring arbor 4 to contact the arbor supports 7 and 8. The deflection of the boring arbor 4 may be regulated (15 to 25 kgf in the graph of FIG. 5).

When the unbalance amount m is less than the above range, a sufficient resultant force F cannot be obtained, and the boring arbor 4 is shown in FIG.
As shown in (b), since there is a gap 61 between the inserted arbor supports 7 and 8, it can be freely deformed in the gap 61 without being constrained by the arbor supports 7 and 8. It is considered that it becomes unstable, and the contact amount of the cutting tool 3 with respect to the bearing hole 2 is less likely to be constant, and the machining accuracy such as the roundness and surface roughness of the bearing hole 2 is reduced.

When the unbalance amount m exceeds the above range, the resultant force F becomes excessively large, so that the deflection of the boring arbor 4 cannot be sufficiently restricted by the arbor supports 7 and 8, and the arbor supports 7 and 8 are coaxial. I can't get a degree.

The unbalance amount m is calculated by substituting the required condition into the equation (2) even when the processing condition is different from that of this embodiment.

[0045]

As is apparent from the above, according to the axial hole machining method of the present invention, since the boring arbor is brought into contact with the inner peripheral surface of the arbor support to restrict the flexure thereof, the flexure is suppressed. Is reduced. Therefore, the amount of contact between the cutting tool and the inner peripheral surface of the shaft hole becomes substantially constant, and excellent machining accuracy can be obtained in terms of roundness and surface roughness of the work.

Further, in the axial hole machining method of the present invention, since the boring arbor is supported at its both ends by a pair of arbor supports, the amount of change in the deflection of the boring arbor is further reduced, and the machining accuracy is improved. It can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a configuration example of a shaft hole drilling device used in a shaft hole drilling method of the present invention.

FIG. 2 is an explanatory cross-sectional view of a boring arbor in the shaft hole drilling device shown in FIG.

3 is a schematic view of a flexible shaft joint in the shaft hole drilling device shown in FIG.

4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a graph showing the relationship between the external force applied to the bowling arbor and the amount of deflection.

FIG. 6 is an explanatory sectional view showing a state of a boring arbor and an arbor support.

FIG. 7 is a schematic view of a conventional shaft hole drilling device.

[Explanation of symbols]

1 ... Shaft hole processing device, 2 ... Shaft hole, 3 ... Bit, 4 ...
Bowling arbor, 7, 8 ... Arbor support.

Claims (2)

[Claims] 1. A shaft for cutting a plurality of shaft holes at the same time by rotating the boring arbor about an axis while at least the tip of the boring arbor provided with a plurality of cutting tools along the axial direction is supported by an arbor support. In the boring method, the boring arbor is machined so that the boring arbor is brought into contact with the arbor support by a centrifugal force generated when the boring arbor rotates and a back force of cutting resistance received by the boring arbor. A method of forming a shaft hole, wherein a resultant force is formed to control the deflection of the boring arbor. 2. The shaft hole drilling method according to claim 1, wherein the boring arbor is supported at its both ends by a pair of arbor supports.