JP2004181607A - Working method of bore inner surface of engine block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working method of a bore inner surface of an engine block for surely and easily improving working efficiency, and reducing equipment cost with a simple constitution. <P>SOLUTION: A rough boring work process is performed for working an inner surface of a prepared hole B of a bore up to first shape accuracy, and next, while continuously performing cutting work by a working blade tool 3 arranged in a cutting tool 1 by allowing the cutting tool 1 to autorotate, a finishing boring work process is performed for cutting the inner surface of the prepared hole B up to second shape accuracy by revolvingly moving along the inner surface of the prepared hole B in a prescribed diameter, and afterwards, a finishing honing work process is performed for grinding the inner surface of the prepared hole B in desired shape accuracy. When performing the rough boring work process or the finishing boring work process, chamfer work is continuously performed by moving in the shaft direction while gradually changing a revolving moving diameter of the cutting tool 1 by an opening of an end part of the prepared hole B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for processing the inner surface of a bore of an engine block, and more particularly to a method for processing the inner surface of a bore formed in an engine block by rough boring.
[0002]
[Prior art]
As a conventional technique regarding the method of processing the inner surface of the bore of the engine block, generally, a boring hole serving as a bore of a cylinder block formed by a die casting method is formed, and then, a honing process is performed for precision finishing. I have.
As shown in FIG. 4, in the boring process, a fine boring finishing process (finishing boring process S20) is performed after the medium finishing process (rough boring process S10), and the rough finishing honing process is performed in the honing process. It is known that a total of four steps are performed in two steps of S30 and a finish honing step S40 (see the related art in Patent Document 1 or Patent Document 2).
[0003]
[Patent Document 1]
JP-A-8-267353 [Patent Document 2]
Japanese Patent Application Laid-Open No. 9-2540011
Patent Document 2 discloses a boring means used in the fine boring finishing processing step S20, which includes a rotatable processing spindle to which a processing chip (processing blade) is attached, and the processing spindle is provided so as to be able to advance and retreat in the axial direction. (Paragraph number 0005). That is, in the conventional fine boring finishing process, as shown in FIG. 5, the central axis G 'of the processing tool 1' coincides with the central axis K of the prepared hole B as a bore, and the processing tool 3 ' Cutting was performed continuously in a state of being constantly in contact with the inner surface of the.
[0005]
[Problems to be solved by the invention]
In the above-mentioned Patent Documents 1 and 2, in a portion where the processing efficiency in the honing process is poor, the finishing honing is performed in a tapered shape so that the grinding process in the finishing honing process S40 is reduced as compared with other portions. In order to make it uniform as a whole by combining with other parts when the processing step S40 is completed, the conventional technique generally performs a larger amount of grinding than other parts in the rough honing processing step S30. Thus, the cutting in the finish boring step S20 is performed in a larger amount than in other parts, so that the rough honing step S30 described above is made unnecessary.
[0006]
Then, in the conventional fine boring processing step S20, as shown in FIG. 5, the cutting tool 3 'continuously cuts while the processing tool 3' is always in contact with the inner surface of the prepared hole B. The problem is that the cutting speed is limited and the machining efficiency cannot be improved due to the rapid wear of the steel and the temperature rises due to friction. There was a problem.
Further, in the conventional rough honing step S30, since a plastic fluidized layer is formed thickly on the inner surface of the prepared hole B by the coarse grindstone, the machining allowance in the subsequent finish honing step S40 increases, There is also a problem that the material constituting the block W is wasted and the processing efficiency is reduced.
[0007]
Further, chamfered portions Ba and Bb (see FIG. 3) are usually formed at both ends of the bore of the engine block W for convenience of assembling a piston or the like. Since it is difficult to change the diameter, a chamfered portion Bb is generally formed at the lower end opening of the prepared hole (rear chamfering) by a dedicated facility prior to the rough boring step S10, and a predetermined axial position of the spindle or the holder is set. And a rough boring process S10 or a finishing boring process S20 is performed, and when the tool 1 'is lowered in the axial direction, the chamfered portion forming blade is opened at the upper end of the prepared hole B. Had to be chamfered. For this reason, there was a problem that the equipment could not be simplified and the number of steps was large and complicated.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems in an advantageous manner, and has a simple structure, and can reliably and easily improve machining efficiency and machining shape accuracy and reduce equipment cost in a bore of an engine block. An object of the present invention is to provide a method of processing an inner surface.
Another object of the present invention is to provide a method of machining the inner surface of a bore of an engine block, which is capable of reliably and easily chamfering a pilot hole with a simple configuration, in order to solve the above-described problem. It is intended for that purpose.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to the first aspect of the present invention relates to a method of processing an inner surface of a bore formed in an engine block, wherein the inner surface of the bore is rotated while rotating a cutting tool. Performs a boring process of revolving and moving at a predetermined diameter along with a cutting tool intermittently with a cutting tool provided on the cutting tool and processing the inner surface of the bore to a predetermined shape accuracy, and then to a desired shape accuracy A honing process for honing the inner surface of the bore is performed.
According to a second aspect of the present invention, there is provided a method for machining an inner surface of a bore of an engine block according to the first aspect of the present invention. It is characterized by performing a preliminary boring process for processing.
Further, in order to achieve the above object, the invention according to a third aspect of the present invention relates to a method for machining an inner surface of a bore of an engine block. It is characterized in that at least one of processing and backside processing is performed.
[0010]
According to the first aspect of the present invention, in the boring step, the cutting tool is revolvingly moved at a predetermined diameter along the inner surface of the bore while rotating, and the cutting tool is intermittently cut by a cutting tool provided in the cutting tool, thereby making it desirable. The inner surface of the bore is cut to a predetermined shape accuracy less than the shape accuracy. Since the cutting tool performs cutting work intermittently, its wear is suppressed and the temperature does not rise, so it is possible to improve the processing efficiency, and it does not require cutting fluid unlike the conventional technology Therefore, dry processing becomes possible. In the boring process of the present invention, since the cutting tool performs the cutting operation intermittently and without difficulty, the formed predetermined shape accuracy is approximately the same level of shape accuracy as the conventional rough honing process. It becomes. Therefore, in the present invention, since there is no need to perform the conventional rough honing process, the honing process is performed after the boring process, and a bore having a desired processing accuracy is easily formed with a small number of facilities.
According to a second aspect of the present invention, in the first aspect of the invention, prior to the boring step, a preliminary boring step of processing the inner surface of the bore to the preliminary shape accuracy is performed. This makes it possible to reliably process the inner surface of the bore to a predetermined shape accuracy in the boring process.
According to a third aspect of the present invention, in the first or second aspect of the invention, when performing the finishing honing process, the cutting tool is moved in the axial direction while gradually changing the revolving diameter of the cutting tool at the opening at the end of the bore. This makes it possible to continuously perform at least one of the surface chamfering process and the back surface chamfering process.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of a method for processing the inner surface of a bore of an engine block according to the present invention will be described in detail with reference to FIGS. Note that the same reference numerals indicate the same or corresponding parts.
The method of machining the inner surface of the bore of the engine block W of the present invention is provided on the cutting tool 1 by revolving the cutting tool 1 at a predetermined diameter along the inner surface of the prepared hole B as the bore while rotating the cutting tool 1 on its own. The inner surface of the prepared hole B is intermittently cut by the cutting tool 3 to perform a boring process S1 for processing the inner surface of the bore to a predetermined shape accuracy, and thereafter, the inner surface of the prepared hole B is ground to a desired shape accuracy. The honing process S2 is performed.
In this embodiment, the method of machining the inner surface of the bore of the engine block W according to the present invention includes a preliminary boring process S0 for machining the inner surface of the prepared hole B to the preliminary shape accuracy prior to the boring process S1. It is something to keep going.
Further, the method for machining the inner surface of the bore of the engine block W according to the present invention is such that when performing the preliminary boring process S0 or the boring process S1, the orbit of the cutting tool 1 at the opening at the end of the prepared hole B is gradually increased. By moving in the axial direction while changing, at least one of the surface chamfering process and the back surface chamfering process (see FIG. 3) is continuously performed to form at least one of the chamfered portions Ba and Bb.
[0012]
FIG. 1 is a block diagram conceptually showing each step performed according to the present invention, and FIG. 2 shows a process for intermittently cutting the inner surface of a prepared hole B to be a bore in a boring process S1. FIG. 3 is a bottom view for conceptually explaining rotation and revolving of the cutting tool 1 provided with a plurality of cutting blades 3 as cutting tools along the inner surface of the prepared hole B. FIG. FIG. 2 is a cross-sectional view shown for explaining an outline of a configuration of a boring device used for the present invention.
[0013]
As shown in FIG. 3, the boring device used in the finishing boring process in this embodiment has a configuration in which a cutting tool 1 is provided with a plurality of cutting blades 3 on the outer periphery of a tip end portion of a holder 2. The holder 2 of the tool 1 is attached to the tip of the main shaft 4 and is driven to rotate around its central axis G, and the orbital diameter adjusting mechanism 6 adjusts the central axis of the housing 5 (on the extension of the central axis of the pilot hole B). The center axis G of the main shaft 4 is driven to rotate around the center axis K, that is, revolve at a predetermined speed in a state adjusted to be eccentric with respect to K) by a predetermined amount.
[0014]
In the embodiment shown in FIG. 3, the orbital diameter adjusting mechanism 6 includes an eccentric shaft 8 that rotatably supports the main shaft 4 around its central axis G via bearings 7, 7 and a bearing 9, 9. And a revolving shaft 10 rotatably supported about the center axis K with respect to the housing 5 while supporting the eccentric shaft 8 rotatably about the center axis H. The revolving shaft 10 is formed so that its outer peripheral surface and inner peripheral surface are eccentric, and is driven to rotate around the center axis H of the outer peripheral surface with respect to the housing 5. The eccentric shaft 8 is formed so that the outer peripheral surface and the inner peripheral surface are eccentric, and is rotated together with the revolving shaft 10 in a normal state. The relative rotation of the revolution shaft 10 and the eccentric shaft 8 around the axis changes the amount of eccentricity of the center axis G of the tool 1 attached to the main shaft 4, that is, the revolution diameter of the cutting tool 1.
[0015]
The boring device thus configured is moved up and down along the center axis K in a state where the center axis K of the housing 5 is positioned so as to be coaxial with the center axis of the pilot hole B (in the case of FIG. 3). Z direction). Then, as shown in FIG. 2, when the tool 1 is driven to rotate and revolve, each cutting edge 3 intermittently contacts the inner surface of the prepared hole B to perform cutting. The revolving diameter of the tool 1 is changed by the revolving diameter adjusting mechanism 6 while the cutting blade 3 moves up and down along the central axis K near the end opening of the prepared hole B, so that the inner surface of the prepared hole B is formed. At least one of a process for forming the surface chamfered portion Ba and a process for forming the back surface chamfered portion Bb can be performed continuously from the boring process.
[0016]
A pilot hole B is formed at a location to be a bore of the engine block W formed by a die casting method or the like. In the method of the present invention, when necessary, for example, when it is difficult to perform cutting to a predetermined shape accuracy in the boring process due to the shape accuracy of the prepared hole serving as the bore of the formed engine block, the preliminary boring process S0 ( In FIG. 1), the inner surface of the prepared hole B is cut to a preliminary shape accuracy using a conventionally used boring device or the above-described boring device. Note that the preliminary shape accuracy is a range from the shape accuracy of the prepared hole B of the engine block W as formed by the die casting method or the like to the final shape accuracy of the bore ground in the honing step S2. This refers to shape accuracy that leaves the possibility of cutting to a predetermined shape accuracy in a later boring process S1. In addition, when the precision of the shape of the pilot hole serving as the bore of the molded engine block is relatively good, the preliminary boring process S0 is not performed, and the boring process is first performed using the above-described boring apparatus or the like. Perform S1.
[0017]
When performing the boring process S1 using the boring device configured as described above to cut the inner surface of the prepared hole B to a predetermined shape accuracy, the boring device is used for cutting the inner surface of the prepared hole B. The relative rotation between the revolution shaft 10 and the eccentric shaft 8 is determined according to the revolution diameter of the cutting tool 1, and the cutting tool 1 is eccentric from the center axis K. The housing 5 is positioned so that its central axis K is located on an extension of the central axis of the pilot hole B, and is moved up and down along the central axis K. Therefore, the tool 1 is driven to rotate around its central axis G and revolved around the central axis K of the housing 5 to move in the circumferential direction and the axial direction (Z direction) along the inner surface of the prepared hole B. The inner surface of the prepared hole B is cut to a predetermined shape accuracy. At this time, in the present invention, each cutting blade 3 intermittently contacts the inner surface of the prepared hole B by the rotation of the cutting tool 1 to perform cutting.
[0018]
As will be clear from the examples described later, the predetermined shape accuracy of the prepared hole B in the boring process (S1 in FIG. 1) of the present invention is different from that in the conventional rough honing process (S30 in FIG. 4). It is at the same level as the shape accuracy of Therefore, in the present invention, the cutting tool is revolved along the inner surface of the bore with a predetermined diameter while rotating, and the cutting tool is intermittently cut by a cutting tool provided in the cutting tool, so that the bore of the bore is formed to a predetermined shape accuracy. The conventional finish boring process (S20 in FIG. 4) and the rough honing process (FIG. 4) in which the cutting is continuously performed by the cutting tool 3 'by simply performing the simple single boring process S1 of processing the inner surface. 4 and S30), the same shape accuracy as in the two steps can be obtained. Therefore, the boring process (S1 in FIG. 1) of the present invention is performed independently, instead of the conventional finish boring process (S20 in FIG. 4) and the rough honing process (S30 in FIG. 4). Only the number of processes and the number of facilities for the processes are reduced, and the efficiency is improved.
[0019]
Furthermore, in the present invention, the abrasion of the cutting edge 3 is suppressed as compared with the conventional technique (see FIG. 5) in which the cutting edge 3 ′ is always in contact with the inner surface of the prepared hole B to perform continuous cutting. Since the service life is extended and the temperature does not rise due to cooling while being away from the inner surface of the prepared hole B, it is possible to increase the speed of at least one of the rotation and the revolution of the cutting tool 1. As a result, it is not necessary to supply a cutting fluid such as a coolant for the purpose of cooling, so that dry machining can be performed, and equipment costs can be reduced.
The surface roughness of the prepared hole B cut in the boring step (S1) is determined by the rotation ratio between the rotation of the main shaft 4 provided with the cutting edge 3 and the rotation of the eccentric shaft 8 and the revolving shaft 10; By controlling the number of the cutting blades 3 provided on the holder 2 or the moving speed of the housing 5 in the axial direction (Z direction) per revolution of the revolution shaft 10 (axial speed per revolution of the tool 1). Can be adjusted to the required level.
[0020]
When the boring process (S1) of the present invention is completed, a honing process (S2 in FIG. 1) is subsequently performed to form a bore whose inner surface is finally finished to a desired shape accuracy. That is, a crosshatch functioning as an oil groove is formed on the inner surface of the bore by a grinding wheel for finishing honing. Further, in the boring process (S1) according to the present invention, since the plastic fluidized bed that needs to be removed is not formed thick as in the prior art, the necessary allowance by grinding in the honing process (S2) is reduced. And the processing efficiency can be improved.
[0021]
When the inner surface of the pilot hole B is cut using the boring apparatus (FIG. 3) configured as described above, the tool 1 is positioned at at least one of the upper end and the lower end of the pilot hole B. At this time, the revolving shaft 10 and the eccentric shaft 8 of the revolving diameter adjusting mechanism 6 are relatively rotated around the axis to change the revolving diameter of the tool 1 attached to the main shaft 4 while moving up and down in the axial direction. As shown in FIG. 3, at least one of the chamfered portions Ba and Bb by chamfering and back chamfering can be performed continuously with the cutting of the prepared hole B.
[0022]
【Example】
The following is a comparison between examples of the shape accuracy by the boring process (S1 in FIG. 1) of the present invention and the shape accuracy by the finish boring process and the rough honing process (S20 and S30 in FIG. 4) of the prior art. Shown to do.
The precision of the shape of the prepared hole B subjected to the finish boring process (S20 in FIG. 4) by the conventional technique (FIG. 5) is 6.5 μm at the position above the prepared hole B and 6.0 at the intermediate position. 2 μm, 9.0 μm at the lower position, parallelism 10.2 μm in the X direction, 9.0 μm in the Y direction, cylindricity 21.5 μm, surface roughness 9.3 Rz (old JIS), surface hardness Hv305 there were.
The shape accuracy of the prepared hole B subjected to the conventional rough honing process (S30 in FIG. 4) is as follows: the roundness is 5.8 μm at the position above the prepared hole B, 5.6 μm at the intermediate position, and Was 5.4 μm, the parallelism was 6.9 μm in the X direction, 7.0 μm in the Y direction, the cylindricity was 8.7 μm, the surface roughness was 7.4 Rz (old JIS), and the surface hardness was Hv302.
[0023]
On the other hand, the shape accuracy of the prepared hole B by the boring process (S1 in FIG. 1) of the present invention is such that the roundness is 5.8 μm at the position above the prepared hole B, 4.0 μm at the middle position, and Was 6.5 μm, the parallelism was 5.5 μm in the X direction, 7.5 μm in the Y direction, the cylindricity was 10.7 μm, the surface roughness was 4.1 Rz (former JIS), and the surface hardness was Hv242.
[0024]
As is clear from the above, the shape accuracy of the prepared hole B by the boring process (S1 in FIG. 1) of the present invention is the same as the shape accuracy of the prepared hole B by the conventional rough honing process (S30 in FIG. 4). It will be at the same level as. Therefore, the two steps of the conventional finish boring process (S20 in FIG. 4) and the rough honing process (S30 in FIG. 4) can be replaced with the boring process (S1 in FIG. 1) of the present invention alone. Therefore, the number of steps can be reduced.
[0025]
【The invention's effect】
According to the present invention, it is possible to provide a method for machining the inner surface of the bore of an engine block, which can reliably and easily improve machining efficiency and machining shape accuracy and reduce equipment cost with a simple configuration.
Further, according to the present invention, it is possible to provide a method of machining the inner surface of the bore of the engine block, which can easily and reliably chamfer the prepared hole with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a procedure of a method for machining an inner surface of a bore of an engine block according to the present invention.
FIG. 2 is a conceptual diagram for explaining the rotation and revolving motion of a boring device used in a finishing boring process of the present invention with respect to a pilot hole of a tool.
FIG. 3 is a cross-sectional view showing one embodiment of a boring device used in a finish boring process.
FIG. 4 is a block diagram showing a procedure of a conventional method for processing the inner surface of a bore of an engine block.
FIG. 5 is a conceptual diagram for explaining the movement of a boring device used in a conventional finish boring process with respect to a pilot hole of a tool.
[Explanation of symbols]
W Engine block B Bore prepared hole 1 Cutting tool 3 Cutting blade (cutting tool)
K Center axis H of the housing Center axis S0 of the tool Preliminary boring process S1 Boring process S2 Honing process

Claims (3)

A method of processing an inner surface of a bore formed in an engine block,
A boring process in which the cutting tool is revolved along the inner surface of the bore with a predetermined diameter while rotating and the cutting tool is intermittently cut by a cutting tool provided on the cutting tool to process the inner surface of the bore to a predetermined shape accuracy. Do
Thereafter, a honing process for honing the inner surface of the bore to a desired shape accuracy is performed. 2. The method according to claim 1, wherein prior to the boring process, a preliminary boring process is performed for pre-processing the inner surface of the bore to the preliminary shape accuracy. The method according to claim 1 or 2, wherein at least one of surface chamfering and back chamfering is performed by changing a revolving diameter of the cutting tool.

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