JP4185176B2 - Non-circular boring machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a boring apparatus capable of cutting a cross section perpendicular to an axis into a noncircular shape in boring of a cylindrical inner surface of a machine part, for example, when a piston pin hole is made in a piston.
[0002]
[Prior art]
In recent internal combustion engine pistons, the pressure applied to the pin holes tends to increase more than before, and the pin hole center axis perpendicular cross-section as in the past cannot resist this pressure. It was not uncommon for cracks to occur.
In order to solve this problem, a pin hole having a non-circular cross section at right angles has recently been adopted.
[0003]
Thus, in order to perform non-circular boring, machining methods such as a copying method, a hydraulic servo method, a servo motor method, and a workpiece swing method have been used. The outline and problems of each system are as follows.
[0004]
In the copying method, an elastic deformable body is provided between the main shaft and the tool holder, and the elastic deformable body is deformed in one direction perpendicular to the axis by a spring force or the like, so that the tool holder is deformed by an amount of deformation with respect to the axis of the main shaft. The axis is shifted. A stylus and a tool (tool) are installed in the direction to shift the axis of the tool holder.
On the other hand, a master having a non-circular cylindrical inner surface to be processed is fixed on the outer circumference bed of the tool holder concentrically with the main shaft. At this time, the stylus fixed to the tool holder is pressed against the inner surface of the master by a spring force or the like provided on the elastic deformable body.
During machining, after the work is mounted concentrically with the spindle, the tool holder rotates while the stylus is pressed against the inner surface of the master due to deformation of the elastic deformable body. Rotate while vibrating in the radial direction. As a result, the work inner surface is processed into a non-circular shape.
[0005]
The problem with such a profiling method is that it takes a lot of time and cost to manufacture and change over the master and fixing jig (to the bed), and the shape of the processing from the point of followability of profiling to the master. For example, there are limitations (only specific ellipses can be machined), it is not possible to deal with shapes with large changes, and high-speed rotation machining is difficult.
[0006]
In the hydraulic servo system, an elastic deformable body is provided between the spindle and the tool holder, and the elastic deformable body is deformed by a specified amount in one direction perpendicular to the axis by hydraulic pressure, so that the amount of deformation of the tool holder with respect to the axis of the main spindle is reduced. The axis is shifted. In addition, the tool is installed in the direction of shifting the axis of the tool holder.
In this case, unlike the profiling method, in order to perform non-circular machining, the amount of displacement of the tool (the amount of deformation of the elastic deformation body) for each axial position and rotation angle is stored, and the hydraulic pressure to be executed as it is is stored. Computer control is required.
In order to perform actual tool displacement more accurately when cutting resistance is applied, feedback control of the amount of tool displacement is performed.
[0007]
The problems with this hydraulic servo system are that the response of the hydraulic cylinder by hydraulic control is low, and the oil pressure changes due to changes in the oil temperature, which affects the machining accuracy. Difficult things, and high speed rotary machining is difficult for these reasons.
[0008]
The servo motor system is the same as the hydraulic servo system except that the elastic deformation body in the hydraulic servo system is deformed by a servo motor attached to the main shaft.
The problem with the servo motor system is that the motor's inertial force increases and the ball screw and feed table are elastically deformed because the motor is frequently rotated forward and backward. Therefore, accurate control of the amount of tool displacement is possible. In other words, the responsiveness is deteriorated, and the processing accuracy is finally deteriorated.
[0009]
The above three methods fix the workpiece and vibrate the tool holder over the entire range in the radial direction, whereas the workpiece rocking method vibrates (swings) the workpiece. . In principle, the workpiece can be swung by means such as copying, hydraulic pressure, servo motor, and the like, as in the above-described three methods.
The problem with such a workpiece swing method is that, in principle, even if it can swing at all angles, it is difficult in practice, and it can only swing in one direction (vibration). They are limited (only a specific ellipse can be machined), and the weight of the workpiece and its mounting jig is increased, and the inertial force due to swinging is also increased.
[0010]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems, and the purpose thereof is to produce a complicated non-circular inner surface shape without the necessity of producing a master or a fixing jig according to the processing shape. An object of the present invention is to provide a non-circular boring apparatus capable of processing at high speed and with high accuracy.
[0011]
[Means for Solving the Problems]
The above problem is that in a device for attaching a boring tool to a main shaft via a tool eccentric vibration device and performing non-circular boring on a workpiece by causing the boring tool to vibrate eccentrically in synchronization with the rotation of the main shaft. attaching the tool holder via an elastic deformation body, by deforming the vibration perpendicular two axial to the mounting axis of the boring tool by a piezoelectric element to the elastic deformable body, perpendicular to its mounting axis boring tool 2 This can be achieved by the above non-circular boring apparatus characterized by causing axial eccentric vibration.
An eccentric vibration of the boring tool may be performed by a magnetostrictive element instead of the piezoelectric element.
Further, it is desirable to perform feedback control by detecting a displacement amount of the elastic deformable body in the direction perpendicular to the axis with a displacement sensor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view of an embodiment of a non-circular boring apparatus in which a uniaxial eccentric vibration perpendicular to its mounting axis is applied to a boring tool, and FIG. FIG. 3 is a control system diagram of the machining apparatus shown in FIG. 1, and FIG. 4 is a non-circular medium in which eccentric vibration in one axial direction perpendicular to the mounting axis is applied to the boring tool . FIG. 5 is a schematic view of another embodiment of a boring apparatus, and FIG. 5 is a schematic view of a non-circular boring apparatus according to the present invention in which a biaxial eccentric vibration perpendicular to its mounting axis is applied to a boring tool . perspective view showing the structure of the spindle tip of the embodiment, FIG. 6 is an enlarged view of the embodiment shown in FIG. 5 from the front end side of the spindle, FIG. 7, the non-circular boring machining apparatus according to the present invention It is a graph which shows the example of a process of the piston pin hole by.
[0013]
1 to 3, 1 is a main shaft of the processing apparatus, 2 is an elastic deformation body attached to the tip of the main shaft, 3 is a tool holder attached to the tip of the elastic deformation body, 4 is a boring tool attached to the tool holder, 5 is a piezoelectric element (or magnetostrictive element) provided inside the elastic deformable body 2, 6 is a displacement sensor for detecting the amount of displacement of the elastic deformable body 2 in the direction perpendicular to the axis, 7 is a motor for rotating the main shaft, and 8 is a rotation angle of the main shaft. A rotary encoder for detection, 9 is a slip ring that takes out the output of the displacement sensor 6 and supplies a drive current to the piezoelectric element 5, 11 is an NC device that controls machining feed and other operations, and 12 is from the NC device 11 A computer that controls processing of a non-circular boring shape by controlling the operation of the piezoelectric element 5 on the basis of the control signal and the output signal from the displacement sensor 6 and the rotary encoder 8. Is a D / A converter, 14 is an A / D converter, 15 is a piezoelectric element controller that controls the operation of the piezoelectric element based on a control signal from the computer 12, 16 is a piezoelectric element driver that supplies a drive current to the piezoelectric element 5, 21 is a feed table, 22 is a servo motor for driving the X-axis direction of the feed table, 23 is a servo motor for driving in the Y-axis direction, and 24 is a workpiece to be subjected to boring.
[0014]
In the above embodiment, the piezoelectric element or the magnetostrictive element 5 is assembled to the elastic deformable body 2 attached to the main shaft 1, and the rotation speed and the rotation angle of the main shaft 1 detected by the rotary encoder 8 are attached to the piezoelectric element or the magnetostrictive element 5. A controlled output voltage is applied through the slip ring 9 in synchronism with the desired non-circular locus.
As a result, the elastic deformable body 2 is pressed and deformed in one direction perpendicular to the axis (attachment direction of the tool 4), and the tool holder 3 and the tool 4 integrated with the elastic deformable body are deformed by the amount of deformation of the elastic deformable body. Displace in the direction perpendicular to the axis.
That is, as shown in FIGS. 2 and 3, the grooves 2 a and 2 b are formed on the outer wall surface of the elastic deformable body 2, and the distal end side of these grooves is displaced in the vertical direction in the drawing by the expansion and contraction vibration of the piezoelectric element 5. As a result, the tool holder 3 rotates eccentrically by the rotation of the main shaft 1.
A desired non-circular boring process can be performed by rotating the spindle while controlling the amount of tool displacement in the direction perpendicular to the axis for each axial position and rotation angle using the NC device 11 and the computer 12. .
The workpiece 24 is, for example, a piston in the example shown in FIG. 3, and shows a state in which a pin hole 24a having a non-circular cross section is bored.
In order to perform processing with higher accuracy, it is desirable to detect the amount of displacement of the elastic deformation body 2 in the direction perpendicular to the axis by the displacement sensor 6 and perform feedback control.
[0015]
This operation will be described below with a specific processing step.
(1) The work 24 is set on the feed table 21.
(2) The spindle rotating motor 7 is rotated. Thereby, the elastic deformation body 2 and the tool holder 3 attached to the main shaft 1 also rotate.
(3) The feed table 21 is moved to the spindle side by the servo motor 22.
(4) When the workpiece 24 reaches a predetermined position near the tool 4 attached to the tool holder 3, a command is sent from the computer 12 to the piezoelectric element controller 15 to operate the piezoelectric element driver 16.
(5) The piezoelectric element driver 16 supplies a driving current to the piezoelectric element 5 provided inside the elastic deformable body 2 through the slip ring 9.
(6) The piezoelectric element 5 is displaced by this current and deforms the elastic deformable body 2. Thereby, the tool holder 3 attached to the front end surface of the elastic deformation body and the tool 4 attached thereto are also displaced.
(7) The rotational angle position of the main shaft is detected by the rotary encoder 8 attached to the main shaft 1, and the displacement amount of the piezoelectric element is changed according to the divided angle position of the machining section based on the shape stored in the computer 12 in advance. Process any shape.
(8) The amount of displacement of the elastic deformable body 2 is detected by the displacement sensor 6, the output signal is sent to the computer 12 through the slip ring 9, and the operation of the piezoelectric element controller 15 is feedback controlled to improve the processing accuracy. .
[0016]
In the embodiment shown in FIG. 4, the piezoelectric element 5 is provided outside the elastic deformable body 2 so as to deform the elastic deformable body.
That is, the main shaft 1 is provided with a column 1a, the piezoelectric element 5 is inserted between the bearing 10 attached to the base of the tool holder 3 and the column 1a, and the tool holder 3 is displaced in the direction perpendicular to the axis by expansion and contraction of the piezoelectric element. It has become.
[0017]
Next, the non-circular boring apparatus according to the present invention shown in FIGS. 5 and 6 applies the vibration of the piezoelectric element in two axial directions perpendicular to the axis of the tool holder 3.
That is, the main shaft 1 is provided with columns 1a and 1b, and the piezoelectric elements 5A and 5B are inserted between the bearing 10 attached to the base of the tool holder 3 and the columns 1a and 1b, respectively. The elastic deformation body 2 is configured to be pressure-deformed in the biaxial direction. The amount of deformation is detected by the displacement sensors 6A and 6B, and the motion trajectory of the tool is biaxially controlled while performing feedback control.
According to this method, responsiveness twice as high as the driving frequency of the elastic deformable body can be obtained, so that stable non-circular boring with higher speed rotation is possible compared to single-axis control.
[0018]
FIG. 7 shows an example in which an elliptical piston pin hole P having a major axis of 36 mm is machined using the non-circular boring machine according to the present invention. On the graph, the 0 ° position is the piston head side, and the 180 ° position is the skirt side.
[0019]
【The invention's effect】
The non-circular boring apparatus according to the present invention has the following advantages over the conventional method.
(1) With respect to the copying method, (1) it becomes unnecessary to manufacture a copying master and the like, and the cost is reduced including shortening of the setup change time.
(2) Shapes with large changes can be processed, and high-speed rotation processing is also possible.
(2) Pressurization response is better than (1) hydraulic pressure compared to hydraulic servo system.
(2) Since no oil is used, there is no effect of oil temperature, and accurate control is possible.
(3) For these reasons (1) and (2), it is possible to process even a shape having a large change, and high-speed rotation processing is also possible.
(4) For the same reason (1) and (2), the machining accuracy is particularly high in the case of the same shape and the same rotational machining.
(3) With respect to the servo motor system, (1) since there is no frequent forward / reverse rotation of the motor, there is no increase in the inertia force of the motor, and there is no elastic deformation of the ball screw and feed table, enabling accurate control.
(2) Therefore, it is possible to process even a shape having a large change, and high-speed rotation processing is also possible. In addition, the machining accuracy in the case of the same shape and the same rotational machining is also high.
(4) With respect to the workpiece swinging method, (1) since the tool can be freely displaced in all 360 ° directions, the shape that can be machined is not limited, and various non-circular machining is possible.
(2) Compared with the swinging of a heavy workpiece or the like, if it has the same shape, it can be rotated at a higher speed.
[0020]
As described above, according to the present invention, there is no need to prepare a master or a fixing jig according to a processing shape, and a complicated non-circular inner surface shape can be processed at high speed and with high accuracy. A non-circular boring apparatus having the following advantages can be provided.
[0021]
The present invention is not limited to the above-described embodiments, and the shape and attachment method of the elastic deformation body, the attachment form of the piezoelectric element or magnetostrictive element to this, and the like can be appropriately changed as necessary. Accordingly, the present invention includes all modifications that can be easily conceived by those skilled in the art from the above description within the scope of the object.
[Brief description of the drawings]
FIG. 1 is a schematic view of an embodiment of a non-circular boring apparatus in which a uniaxial eccentric vibration perpendicular to its mounting axis is applied to a boring tool .
FIG. 2 is a perspective view showing a configuration of a tip end portion of the main shaft.
FIG. 3 is a control system diagram of the machining apparatus shown in FIG.
FIG. 4 is a schematic view of another embodiment of a non-circular boring apparatus in which a boring tool is subjected to uniaxial eccentric vibration perpendicular to its mounting axis .
FIG. 5 is a perspective view showing a configuration of a spindle tip portion of an embodiment of a non-circular boring apparatus according to the present invention in which an eccentric vibration in a biaxial direction perpendicular to the mounting axis is applied to a boring tool . It is.
6 is an enlarged view of the embodiment shown in FIG. 5 as viewed from the front end side of the main shaft. FIG.
FIG. 7 is a graph showing an example of processing of a piston pin hole by the non-circular boring apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main axis | shaft of processing apparatus 1a, 1b Support | pillar 2 Elastic deformation body 2a, 2b Groove 3 Tool holder 4 Boring tool 5 Piezoelectric element (or magnetostrictive element)
6 Displacement sensor 7 Spindle motor 8 Rotary angle detection rotary encoder 9 Slip ring 10 Bearing 11 NC device 12 Computer 13 D / A converter 14 A / D converter 15 Piezo element controller 16 Piezo element driver 21 Feed table 22 X-axis direction Servo motor for driving 23 Servo motor for driving in Y-axis direction 24 Workpiece

Claims (3)

In the apparatus for attaching the boring tool (4) to the main spindle (1) via a tool eccentric vibration device and performing non-circular boring on the workpiece by causing the boring tool to vibrate eccentrically in synchronization with the rotation of the main spindle, The tool holder (3) is attached to the main shaft (1) via the elastic deformation body (2), and the elastic deformation body (2) is perpendicular to the attachment axis of the boring tool (4) by the piezoelectric elements (5A, 5B). The non-circular boring apparatus described above , wherein the boring tool (4) is caused to vibrate eccentrically in a biaxial direction perpendicular to its mounting axis by deforming and vibrating in a biaxial direction . The non-circular boring apparatus according to claim 1, wherein eccentric vibration of the boring tool (4) is performed by a magnetostrictive element instead of the piezoelectric element ( 5A, 5B ). 2. The non-circular boring apparatus according to claim 1, wherein a feedback control is performed by detecting a displacement amount in a direction perpendicular to the axis of the elastic deformable body (2) by a displacement sensor ( 6A, 6B ).

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