JP4666178B2 - Honing processing method and processing apparatus - Google Patents

Description

  The present invention relates to a honing method and a processing apparatus for grinding a cylindrical inner surface by rotating a honing head having a grindstone while moving it in the axial direction with respect to a workpiece having a cylindrical inner surface conveyed on a processing line. About.

  As a workpiece having a cylindrical inner surface, for example, a cylinder bore of a cylinder block is an important part that determines engine performance, and thus there is a high demand for shape accuracy and surface properties. As shape accuracy, in order to reduce piston sliding resistance, roundness and cylindricity are required to be as high as possible. In addition, in order to reduce the seizure (scuffing) of the piston, it is desirable that the surface texture is sufficient to retain the oil and graphite as the fixed lubricant is exposed as much as possible on the bore surface.

  In order to satisfy these conditions, as shown in FIG. 8, a honing head 5 provided with a grindstone 3 is inserted into the bore inner peripheral surface of the cylinder bore 1, and the honing head 5 is rotated and moved in the axial direction. The honing process for grinding is performed (see Patent Documents 1 and 2 below). A plurality of the above-described grindstones 3 are provided in the circumferential direction, and processing is performed while pressing with a predetermined expansion pressure toward the radially outer side, that is, toward the bore inner circumferential surface of the cylinder bore 1.

In the honing process described above, a certain amount of machining allowance is required in order to remove the surface roughness in the boring process, which is the pretreatment. For this reason, in order to minimize the honing time, the most part of the machining allowance is usually done by rough honing with high grinding efficiency. After rough honing, finishing honing with low grinding efficiency aimed at improving shape accuracy and surface properties Processing is in progress.
JP-A-5-57597 JP-A-5-57598

  By the way, at the time of rough honing, in order to increase the machining allowance as described above, the deformation due to the expansion pressure that is the pressing pressure of the grindstone 3 against the cylinder bore 1 is large. FIG. 9A shows a deformed state of the cylinder bore 1 during rough honing. According to this, while the upper opening side of the cylinder bore 1 is greatly expanded radially outward in the drawing, the inner diameter of the lower side in the drawing is deformed to be small.

  In this deformed state, when the expansion pressure by the grindstone 3 is released and the workpiece is left, the action of the inner peripheral surface of the cylinder bore 1 being pressed back to the center side, that is, the spring back indicated by the arrow S occurs, for example, FIG. The shape is as shown in (b).

  However, if the subsequent finish honing process is performed in the deformed state as shown in FIG. 9A, it is difficult to ensure a highly accurate shape due to the influence of the spring back during the process. In addition, there is a problem that the degree of exposure of graphite as a fixed lubricant to the bore surface becomes insufficient.

  In view of the above, an object of the present invention is to make the degree of exposure of the graphite, which is a fixed lubricant, to the processed surface particularly satisfactory.

The present invention relates to a honing method for grinding a cylindrical inner surface by rotating a honing head having a grindstone while moving it in the axial direction with respect to a workpiece having a cylindrical inner surface conveyed on a processing line. In the machining process, after roughing the cylindrical inner surface using a honing head equipped with a roughing grindstone, the honing head used in the roughing process is pulled out of the cylinder in the idle process. In a state where the workpiece is not inserted , the workpiece is left for a predetermined time while supplying a coolant to the workpiece, and a spring back is generated. In a subsequent finishing process, the honing head including a finishing grindstone is Rotating in the opposite direction to the machining process, honing is performed so as to cancel the plastic flow generated in the roughing process, The most important feature to expose the graphite.

According to the present invention, in the finishing process, the honing head is rotated in the opposite direction to the roughing process, so that the plastic flow of the machined surface generated in the finishing process occurs in the opposite direction to the plastic flow in the roughing process. The action of canceling the plastic flow during roughing works, the plastic flow during finishing is reduced, and the generation of micro burrs is suppressed, so that a highly accurate machining surface can be obtained and the workpiece machining surface can be obtained. The graphite can be exposed and the lubrication performance of the processed surface can be enhanced.
In addition, since there is an idle process in which the workpiece is allowed to stand for a predetermined time between the roughing process and the finishing process, a coolant is supplied during the idle process and deformation due to the spring back of the work occurs. The influence of the springback in the finishing process can be eliminated, and a highly accurate shape can be secured and a high degree of graphite exposure can be achieved. Since this idle process is set on the same line between the roughing process and the finishing process, there is no need for a separate abandonment space, and there is no wasted time, extending the processing time. Has been avoided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a honing method according to an embodiment of the present invention. (A) is a roughing process in the honing process, and (c) is a finishing process in the honing process. An idle process (b) for leaving the workpiece for a predetermined time is provided between the roughing process (a) and the finishing process (c). These processes are set on the same processing line. Yes. On this same line, the cylinder block 11 of the engine having a cylindrical inner surface is conveyed as a workpiece in the order of the roughing process (a), the idle process (b), and the finishing process (c).

  As shown in the roughing process of FIG. 1A, a honing head 15 is inserted into the cylinder bore 13 of the cylinder block 11. In the outer peripheral portion of the honing head 15, a plurality of rectangular parallelepiped roughing grindstones 17 that are long in the vertical direction in the figure are provided at equal intervals along the circumferential direction.

  The roughing grindstone 17 can be pressed at a predetermined expansion pressure T1 toward the inner peripheral surface of the cylinder bore 13 by an expansion pressure mechanism (not shown). The honing head 15 provided with such a roughing grindstone 17 performs rough honing on the inner peripheral surface of the cylinder bore 13 while rotating while moving in the vertical axial direction in the drawing.

  In the cylinder block 11 described above, the cylinder bore 13 is finished using the honing head 21 provided with the finishing grindstone 19 in the finishing process of FIG. As with the roughing grindstone 17, the finishing grindstone 19 is also provided with a plurality of rectangular parallelepiped shapes that are long in the vertical direction in the figure at equal intervals along the circumferential direction. It can be pressed toward the inner peripheral surface of the cylinder bore 13 with a predetermined expansion pressure T2.

  The honing head 21 equipped with such a finishing grindstone 19 also rotates while moving in the axial direction in the same manner as during roughing, but this rotational direction is opposite to that during roughing.

  In each of the above-described steps (a), (b), and (c), coolant nozzles 23, 25, and 27 that supply coolant as a coolant into the cylinder bore 13 are installed. Each of the coolant nozzles 23, 25, 27 is supplied from a common coolant supply source 29 via a pipe 31.

  The cylinder block 11 subjected to the rough machining on the cylinder bore 13 in the roughing process (a) is transported to the next idle process (b), where it is left for 60 seconds as a predetermined time. During this time, roughing and finishing are performed on the other cylinder blocks in the roughing process (a) and the finishing process (c) before and after that. In addition, the leaving time of the cylinder block 11 in the idle process (b) may be at least 30 seconds.

  Immediately after the roughing in the roughing step (a), as shown by the two-dot chain line in FIG. 1 (b), the cylinder bore 13 is deformed in the same manner as in FIG. 9 (a) by the expansion pressure T1 by the roughing grindstone 17. is doing. From this deformed state, in the next idle step (b), the cylinder block 11 is left as it is without inserting the honing head into the cylinder bore 13, so that the cylinder bore 13 is shown by the solid line in FIG. Then, it is contracted and deformed by the action of the spring back S.

  As shown in FIG. 2, the cylinder bore 13 after the contraction and deformation is in a state in which the amount of spring back is almost maximum by setting the standing time to 60 seconds. The cylinder bore 13 in the state in which the spring back amount is maximized in this way has an upper diameter in the drawing as shown in the solid line in FIG. Unlike the shape that is larger and has a smaller diameter at the lower part, it has recesses 13a, 13b,... Having substantially the same inner diameter along the axial direction, and the projections 13c, 13d, 13e having substantially the same inner diameter adjacent to the recesses. , ... respectively.

  As described above, the cylinder block 11 left for 60 seconds after the roughing is transported to the next finishing step (c), where the honing head 21 equipped with the finishing grindstone 19 is moved to the roughing step (a). Rotate in the opposite direction to finish honing.

  In the roughing process (a), in order to process a large machining allowance in a short time, the expansion pressure T1 is set several times higher than the expansion pressure T2 at the time of finishing. For this reason, the spring back of the cylinder block 11 after the rough machining is very large, and it takes about 60 seconds as described above until the return deformation due to the spring back becomes substantially maximum.

  The effects of setting such an idle process (b) include the following two points.

  One point is that during the finishing process, the influence of the springback after the roughing process is extremely small, so that the machining accuracy can be determined almost by the ability of the finishing process alone. The other point is as follows.

  During rough machining, the cylinder bore 13 has a shape expanded by the roughing grindstone 17 as shown by a two-dot chain line in FIG. 1 (b). As shown by the solid line 1 (b), the concave portions 13a, 13b,... And the convex portions 13c, 13d, 13e,... Are generated, so that the contact of the finishing grindstone 19 with the processed surface is shown in FIG. As shown, it is per local.

  At this time, since the finishing grindstone 19 is pressed against the machining surface with a constant force F, the surface pressure of the portion of the finishing grindstone 19 that is in contact with the local area increases. The honing process has a feature that the grinding efficiency increases as the surface pressure increases, and the amount of abrasive grains biting into the processing surface increases. For this reason, the processing time is shorter when the processing surface has irregularities than when the processing surface does not exist (when the grindstone hits the entire processing surface).

  Here, the protrusion amount h (see FIG. 3) of the protrusions 13c, 13d, and 13e on the processed surface from the recesses 13a and 13b is about 30% to 50% of the machining allowance in the finishing process. As a result, the processing time in the finishing process is reduced by about 10% compared to the conventional process.

  Further, as shown in FIG. 4, the abrasive grains 33 of the finish processing grindstone 19 increase in load due to an increase in the amount of biting into the processed surface 35, and fragile 33a is likely to occur (so-called self-generated as a grindstone). A new cutting edge 33b is born and the sharpness is improved. In FIG. 4, the direction indicated by the arrow A is the moving direction of the finishing grindstone 19, the reference numeral 37 indicates the plastic flow generated in the roughing process (a), and 39 indicates the resistance force (load) due to the plastic flow 37. .

  As a result, a reduction in grinding resistance → reduction in bore deformation / reduction in plastic flow → improvement in machining accuracy results in a chain effect.

  If the finishing process described above is continued, the local contact of the finishing grindstone 19 with respect to the processing surface 35 gradually disappears and the entire surface grinds. However, since the abrasive grains 33 remain sharp, the processing is completed (the grindstone The above-mentioned effect is continued until the machining allowance until the machining is completed after the contact with the entire surface is about φ10 to 15 μm).

  By these actions, the shape accuracy (roundness, cylindricity) of the cylinder bore 13 is compared with the conventional processing method A in the processing method C when the idle process (b) is provided, as shown in FIG. About 30%. Further, regarding the degree of graphite exposure on the inner peripheral surface of the cylinder bore 13, as shown in FIG. 6, the processing method C in the case where the idle process (b) is provided is 40% compared to the conventional processing method A. The improvement is seen.

  The reason why the graphite exposure level is improved is the reduction of plastic flow, which will be described later.

  Next, the effect in the case where the rotation direction of the honing head 21 in the finishing process (c) is opposite to the rotation direction of the honing head 15 in the roughing process (a) will be described below.

  As described above, in the roughing step (a), the expansion pressure T1 by the roughing grindstone 17 is large, and the grain size of the roughing grindstone 17 is larger than that of the finishing grindstone 19 in order to improve the grinding efficiency. Is used. For this reason, as shown in FIG. 7, a roughened machining results in a machined surface 35 having a relatively deep plastic flow 37 and a small burr 41. In addition, a large number of graphite 43 that is not exposed on the surface of the processed surface 35 is generated due to this influence.

  Reversing the rotation direction of the honing head 21 in the finishing process (c) with respect to the roughing process means that the abrasive grains 33 move in the direction opposite to the plastic flow 37 in the roughing process. The known material peeling effect occurs, and the plastic flow 37a caused by the abrasive grains 33 of the finishing grindstone 19 is generated in the opposite direction to the plastic flow 37 in the rough machining. The action to counteract works.

  Due to these actions, it is possible to obtain a machined surface 35a in which the plastic flow 37a in the finishing process is small and the minute burrs 41 are hardly generated. Since the graphite 43a is not easily affected by the small plastic flow 37a, the graphite 43a is easily exposed to the surface. As shown in FIG. 6, the processing method B for performing reverse reverse rotation as shown in FIG. Compared with A, it is improved by about 20%. As for the shape accuracy, as shown in FIG. 5, the processing method B that performs the finish reverse rotation is improved by about 30% compared to the conventional processing method A.

  In the case where the finishing process is performed by rotating the honing head in the same direction as the roughing process as in the past, the above effect cannot be obtained, and only the effect of the finishing process is obtained. For example, the cork material is replaced with a grindstone. Additional processing such as cork honing used and plateau honing with a grindstone having a finer grain than the finishing grindstone is required, resulting in an increase in cost.

  Next, the effect when combining the case where the idle step (b) is provided and the case where the honing head is reversely rotated in the finishing step (c) will be described.

  As described in the effect when the idle process (b) is provided, the grinding resistance is reduced and the shape accuracy of the processed surface is improved by improving the sharpness of the grindstone. If the effect of reverse rotation is added to this, the grinding resistance is further reduced, and the shape accuracy of the processed surface is further improved by about 10% as in the processing method D (B + C) of FIG. That is a 40% improvement in total. Moreover, about the graphite exposure degree, the improvement of 60% is seen compared with the conventional processing method A like the processing method D (B + C) of FIG.

  As shown in FIG. 4, the action of reverse rotation of the honing head in the finishing step (c) is caused by the grinding resistance due to the movement of the abrasive grains 33 of the finishing grindstone 19 so as to overcome the plastic flow 37 in rough machining. Load) 39 is almost equal to the reduction in grinding resistance due to the material peeling effect, and the total grinding efficiency is not sufficient.

  However, when the above-described action by the reverse rotation is added to the action by the idle process (b), the resistance component of the plastic flow becomes a further load 39 on the abrasive grains, and no self-acting action is obtained only by providing the idle process (b). As a result, even the abrasive grains that grow are self-generated and the sharpness of the abrasive grains is further increased. As a result, the grinding resistance is reduced as compared with the case where only the idle process (b) is provided, and the shape accuracy of the processed surface is improved.

  In order to improve the shape accuracy, since the expansion speed of the roughing grindstone 17 in the roughing step (a) is not lowered and the finishing time is not lengthened, the machining time is extended. It has been avoided.

  Next, the effect by supplying coolant in an idle process (b) is demonstrated.

  In the idle process (b), as shown in FIG. 1, the coolant having the same temperature condition is supplied from the common coolant supply source 29 to all of the roughing process (a), the idle process (b), and the finishing process (c). To supply. If the workpiece is simply left in the idle process (b) after the rough machining, a sudden temperature change occurs after the rough machining with the coolant supplied, and the amount of spring back on the inner peripheral surface of the cylinder bore is affected by the temperature change. As a result, it is not even, and a lot of machining allowance is required for finishing.

  Therefore, by supplying the coolant in the idling step (b), the amount of spring back is more evenly generated, thereby shortening the finishing time.

  Note that the coolant supplied in the above-described idle process (b) does not need to use the common coolant supply source 29 for the roughing process (a) and the finishing process (c), and uses a single coolant supply source. However, by using the common coolant supply source 29, the coolant temperature in each process becomes substantially equal, and it is not necessary to provide a dedicated coolant supply source separately in the idle process (b), and the entire apparatus Simplification can be achieved.

  According to the present invention, since there is an idle process in which the workpiece is left for a predetermined time between the roughing process and the finishing process on the same line, deformation due to the springback of the work occurs during the idle process, The influence of springback in the subsequent finishing process can be eliminated, and a highly accurate shape can be secured and a high degree of graphite exposure can be achieved. Since this idle process is set on the same line between the roughing process and the finishing process, there is no need for a separate abandonment space, and there is no wasted time, extending the processing time. Has been avoided.

  In addition, by supplying coolant to the workpiece in the idle process described above, the temperature change of the workpiece is made uniform as a whole, and the amount of springback is also made uniform on the entire machining surface, so the machining allowance in finishing machining is more than necessary. The finishing time can be shortened without increasing.

  Furthermore, by making the temperature of the coolant supplied in the idle process equal to the temperature of the coolant used in the roughing process and the finishing process, the coolant supply source can be shared, and a dedicated dedicated process is provided in the idle process. There is no need to provide a coolant supply source, and simplification of the entire apparatus can be achieved.

  Also, by letting the workpiece to stand for at least 30 seconds in the idle process, the amount of return deformation due to the springback action after rough honing will be sufficient, and the influence of pulling back in subsequent finishing will be eliminated. Can do. If the workpiece leaving time has not reached 30 seconds, as shown in FIG. 3, the amount of return deformation due to the spring back action after rough honing is insufficient, and the effect of pulling back is affected by the subsequent finishing. I will receive it.

It is a manufacturing process figure which shows the honing processing method concerning one Embodiment of this invention. FIG. 5 is a correlation diagram between a workpiece leaving time after rough machining and a springback amount. It is explanatory drawing which shows the contact state to the processed surface of a finishing grindstone. It is explanatory drawing which shows the self-generated action of a grindstone. It is explanatory drawing which showed the shape precision of the processing surface by comparing with a prior art example and this invention. It is explanatory drawing which showed the release degree of the graphite exposed to a process surface by comparing with a prior art example and this invention. It is explanatory drawing which shows the principle of surface property improvement of a process surface. It is sectional drawing which shows a honing process. It is sectional drawing of a cylinder bore, (a) shows the thing immediately after roughing, (b) shows what was left for a predetermined time after roughing.

Explanation of symbols

11 Cylinder block (work)
15, 21 Honing head 17 Roughing grindstone 19 Finishing grindstone 37 Plastic flow in roughing 37a Plastic flow in finishing 43,43a Graphite

Claims (4)

In a roughing process in a honing method for grinding a cylindrical inner surface by rotating a honing head equipped with a grindstone while moving it in the axial direction with respect to a workpiece having a cylindrical inner surface conveyed on a processing line, After performing roughing on the inner surface of the cylinder using a honing head equipped with a roughing grindstone, the honing head used in the roughing process is not drawn out and inserted into the cylinder in the idle process. Then, while supplying the coolant to the workpiece , the workpiece is allowed to stand for a predetermined time to generate a springback, and the honing head equipped with a finishing grindstone in the subsequent finishing processing step is the roughing step. Rotating in the reverse direction, honing is performed so as to cancel the plastic flow generated in the roughing process, and graphite is applied to the cylindrical inner surface of the workpiece. Honing processing method for causing out. The temperature of the cooling liquid, the roughing step and honing method according to claim 1, characterized in that equal to the temperature of the cooling liquid used in the finishing process. 3. The honing method according to claim 1, wherein a workpiece leaving time in the idle process is at least 30 seconds. In a honing apparatus that grinds the cylindrical inner surface by rotating a honing head having a grindstone while moving it in the axial direction with respect to a workpiece having a cylindrical inner surface conveyed on the processing line, the processing line includes: A roughing process for roughing the cylindrical inner surface using a honing head equipped with a roughing grindstone, and a finishing process for finishing the cylindrical inner surface using a honing head equipped with a finishing grindstone provided the door on the same line, between the rough machining step and the finishing step, the roughing step honing head used in, pulling against the said cylinder, with no insert, relative to the workpiece Te while supplying coolant is provided an idle step of generating the spring back of the workpiece after the rough machining and left for a predetermined time, the finishing additive The honing process is characterized in that the rotation direction of the honing head is opposite to the roughing process, and the graphite is exposed on the cylindrical inner surface of the workpiece so as to cancel the plastic flow generated in the roughing process. Processing equipment.

Images