EP4751844A1

EP4751844A1 - Grinding method and grindstone with shaft

Info

Publication number: EP4751844A1
Application number: EP24868060.5A
Authority: EP
Inventors: Tadashi Okada
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2023-09-19
Filing date: 2024-08-28
Publication date: 2026-06-03
Also published as: WO2025062980A1; CN121443419A; JP7662958B2; JP2025043698A

Abstract

A grindstone (10) with a shaft includes a base (11), a grindstone shaft (12) having one end supported by the base (11), and a grindstone (13) attached to the grindstone shaft (12). The base (11) is provided with a guide structure (15a, 17, 18, 18a) so that a grinding fluid discharged toward an outer peripheral surface of the base (11) is supplied to a grinding portion of the workpiece (1) while a flow direction of the grinding fluid is changed.

Description

TECHNICAL FIELD

The present disclosure relates to a grinding method and a grindstone with a shaft.

BACKGROUND ART

For internal grinding of a workpiece, a grindstone with a shaft, which is a grindstone attached to a grindstone shaft rotated by a wheel head, has been used (see Patent Document 1).
The internal grinding applies a grinding load to the grindstone, and the grindstone shaft deflects. The deflection is not negligible compared to the machining accuracy required for grinding. Thus, high-precision internal grinding requires spark-out grinding, which is a process of suspending the axial movement of the grindstone shaft for several seconds until the deflection is eliminated. If a target hole to be machined is long and narrow, the grindstone shaft needs to be long and narrow as well. Such a grindstone shaft is less rigid, and takes long time to perform the spark-out grinding to recover the deflection of the grindstone shaft, increasing machining time.
The internal grinding requires a grinding fluid to be supplied to a grinding portion of the workpiece. For machining a narrow hole having a small diameter, it is necessary to dispose a port for jetting the grinding fluid so that the grinding fluid smoothly enters a gap between the grindstone shaft and the target hole. If the target hole is a blind hole, the grinding fluid needs to be supplied to the grinding portion of the workpiece from the same side from which the grindstone shaft is inserted. Patent Document 1 discloses that a supply pipe for the grinding fluid is bent along the axial direction of the grindstone shaft to face the port for jetting the grinding fluid toward the target hole.

CITATION LIST

PATENT DOCUMENT

Patent Document 1: Japanese Unexamined Patent Publication No. 2014-69303

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

If the grindstone shaft is shortened to improve the rigidity and reduce the time for the spark-out grinding and the machining time, the distance between the workpiece and the wheel head decreases too much when the innermost portion of the target hole is ground. This makes it difficult to appropriately dispose the port for jetting the grinding fluid. Insufficient supply of the grinding fluid to the grinding portion causes problems such as grinding burn involving a temperature rise of the grinding portion to 500°C or higher, and shortened life of the grindstone.
An object of the present disclosure is to provide a grinding method and a grindstone with a shaft capable of sufficiently supplying a grinding fluid to a grinding portion of a workpiece, with a grindstone shaft shortened to ensure its rigidity.

SOLUTION TO THE PROBLEM

A first aspect is directed to a grinding method for performing internal grinding of a workpiece (1) by rotating a grindstone (13) attached to a grindstone shaft (12) protruding from a base (11), wherein a distance between the base (11) and the workpiece (1) during the grinding changes, and the distance is equal to or less than 5 mm when the innermost portion of the workpiece (1) is ground, and a grinding fluid discharged toward an outer peripheral surface of the base (11) is supplied to a grinding portion of the workpiece (1) while a flow direction of the grinding fluid is changed by a guide structure (15a, 17, 18, 18a) provided on the base (11).
In the first aspect, although the grindstone shaft (12) is shortened to set the distance between the base (11) and the workpiece (1) during the grinding equal to or less than 5 mm, the guide structure (15a, 17, 18, 18a) provided on the base (11) allows sufficient supply of the grinding fluid to the grinding portion of the workpiece (1). This can reduce grinding burn, and can provide a grindstone with a shaft with longer life by reducing the wear of the grindstone (13).
A second aspect is an embodiment of the first embodiment. In the second aspect, the internal grinding of the workpiece (1) is performed with the base (11) covered with a non-rotating umbrella-shaped member (21).
In the second aspect, the grinding fluid can be kept from splashing off the outer peripheral surface of the base (11), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
A third aspect is directed to a grindstone with a shaft, including: a base (11); a grindstone shaft (12) having one end supported by the base (11); and a grindstone (13) attached to the grindstone shaft (12) and configured to rotate together with the grindstone shaft (12) to perform internal grinding of a workpiece (1), wherein the base (11) is provided with a guide structure (15a, 17, 18, 18a) so that a grinding fluid discharged toward an outer peripheral surface of the base (11) is supplied to a grinding portion of the workpiece (1) while a flow direction of the grinding fluid is changed.
In the third aspect, although the grindstone shaft (12) is shortened to set the distance between the base (11) and the workpiece (1) during the grinding equal to or less than 5 mm, the guide structure (15a, 17, 18, 18a) provided on the base (11) allows sufficient supply of the grinding fluid to the grinding portion of the workpiece (1). This can reduce grinding burn, and can provide a grindstone with a shaft with longer life by reducing the wear of the grindstone (13). Further, with the grindstone shaft (12) shortened, the machining accuracy can be kept from decreasing due to deflection of the grindstone shaft (12), and the time required for the spark-out grinding can be reduced. This shortens the machining time, that is, improves the machining speed.
A fourth aspect is an embodiment of the third aspect. In the fourth aspect, the base (11) includes a truncated conical portion (15) having the grindstone shaft (12) at a top, and a cylindrical portion (16) connected to a bottom of the truncated conical portion (15), an outer peripheral surface of the truncated conical portion (15) is formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a), an inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and the concave surface (15a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
In the fourth aspect, the jetting pressure of the grinding fluid causes the grinding fluid discharged toward the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the concave surface (15a). This allows the grinding fluid to be supplied from the top of the truncated conical portion (15) to the grinding portion of the workpiece (1) along the grindstone shaft (12).
A fifth aspect is an embodiment of the third aspect. In the fifth aspect, the base (11) includes a truncated conical portion (15) having the grindstone shaft (12) at a top, and a cylindrical portion (16) connected to a bottom of the truncated conical portion (15), and an outer peripheral surface of the truncated conical portion (15) is provided with a plurality of twisted blades (17) as the guide structure (15a, 17, 18, 18a).
In the fifth aspect, rotating the plurality of blades (17) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the outer peripheral surface of the base (11) against the centrifugal force, supplying the grinding fluid to the grinding portion of the workpiece (1) from the top of the truncated conical portion (15) along the grindstone shaft (12).
A sixth aspect is an embodiment of the fifth aspect. In the sixth aspect, the outer peripheral surface of the truncated conical portion (15) between the plurality of blades (17) is also formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a), an inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and the concave surface (15a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
In the sixth aspect, the effect of the fourth aspect can be achieved in addition to the effect of the fifth aspect.
A seventh aspect is an embodiment of the fifth or sixth aspect. In the seventh aspect, a lid member (19) is provided on the truncated conical portion (15) to cover the plurality of blades (17).
In the seventh aspect, the grinding fluid can be kept from splashing off the outer peripheral surface of the truncated conical portion (15), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
An eighth aspect is an embodiment of the third aspect. In the eighth aspect, the base (11) includes a truncated conical portion (15) having the grindstone shaft (12) at a top, and a cylindrical portion (16) connected to a bottom of the truncated conical portion (15), and an outer peripheral surface of the truncated conical portion (15) is provided with a plurality of twisted grooves (18) as the guide structure (15a, 17, 18, 18a).
In the eighth aspect, rotating the plurality of grooves (18) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the plurality of grooves (18) against the centrifugal force, supplying the grinding fluid to the grinding portion of the workpiece (1) from the top of the truncated conical portion (15) along the grindstone shaft (12).
A ninth aspect is an embodiment of the eighth aspect. In the ninth aspect, a bottom surface of each of the plurality of grooves (18) is also formed into a concave surface (18a) as the guide structure (15a, 17, 18, 18a), an inclination angle θ of the concave surface (18a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and the concave surface (18a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
In the ninth aspect, the jetting pressure of the grinding fluid causes the grinding fluid discharged toward the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the bottom surface of each groove (18) of the truncated conical portion (15), that is, the concave surface (18a), supplying the grinding fluid more efficiently to the grinding portion of the workpiece (1).
A tenth aspect is an embodiment of the eighth or ninth aspect. In the tenth aspect, a lid member (19) is provided on the truncated conical portion (15) to cover the plurality of grooves (18).
In the tenth aspect, the grinding fluid can be kept from splashing off the outer peripheral surface of the truncated conical portion (15), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 is a perspective view of a grinding device including a grindstone with a shaft according to an embodiment.
[FIG. 2] FIG. 2 is a cross-sectional view of the grinding device including the grindstone with the shaft according to the embodiment.
[FIG. 3] FIG. 3 is a perspective view of the grindstone with the shaft according to the embodiment.
[FIG. 4] FIG. 4 is a side view of the grindstone with the shaft according to the embodiment (a view seen from the direction perpendicular to a grindstone shaft).
[FIG. 5] FIG. 5 is a perspective view of a grindstone with a shaft according to a first variation.
[FIG. 6] FIG. 6 is a perspective view of a grindstone with a shaft according to a second variation.
[FIG. 7] FIG. 7 is a perspective view of a grindstone with a shaft according to a third variation.
[FIG. 8] FIG. 8 is a side view of a grinding device including a grindstone with a shaft according to a fourth variation (a view seen from the direction perpendicular to a grindstone shaft).
[FIG. 9] FIG. 9 is a cross-sectional view of a grinding device including a grindstone with a shaft according to Comparative Example 1.
[FIG. 10] FIG. 10 is a cross-sectional view of a grinding device including a grindstone with a shaft according to Comparative Example 2.

DESCRIPTION OF EMBODIMENTS

(Embodiment)

An embodiment of the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the embodiment shown below, and various changes can be made within the scope without departing from the technical concept of the present disclosure. Since each of the drawings is intended to illustrate the present disclosure conceptually, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding. The numerical values in the following embodiment are merely examples, and the present disclosure is not limited to them.

As illustrated in FIGS. 1 to 4, a grinding device (100) mainly includes a grindstone (10) with a shaft for performing internal grinding of a workpiece (1), a wheel head (20) for rotating the grindstone (10) with the shaft, and a grinding fluid supply unit (30) for supplying a grinding fluid to a grinding portion of the workpiece (1).
The grindstone (10) with the shaft includes a base (11) made of metal, a long and narrow grindstone shaft (12) having one end supported by the base (11), and a grindstone (13) exchangeably attached to the grindstone shaft (12). The base (11) has, for example, a truncated conical portion (15) having the grindstone shaft (12) at the top and a cylindrical portion (16) connected to the bottom of the truncated conical portion (15). The cylindrical portion (16) may be chamfered so that a spanner can be used for attachment to the wheel head (20). The grindstone shaft (12) may be made of the same material as the base (11) and integrally formed with the base (11). For higher rigidity of the grindstone shaft (12), the grindstone shaft (12) may be made of a superhard material and inserted and joined to the base (11). The grindstone (13) may have, for example, a cylindrical shape, and may be fixed to the grindstone shaft (12) with the grindstone shaft (12) inserted into a cylindrical hole of the grindstone (13). The grindstone (13) rotates together with the grindstone shaft (12) to perform the internal grinding of the workpiece (1). The diameter of the grindstone (13) is smaller by about several millimeters than the diameter of a hole formed in the workpiece (1).
The base (11) of the grindstone (10) with the shaft has a fixture member (14) on the opposite side of the grindstone shaft (12) for attaching the grindstone (10) with the shaft to a rotating mechanism (not shown) of the wheel head (20). The fixture member (14) may be, for example, a mounting screw or a draw-in taper (a fastener). The wheel head (20) is configured to move the grindstone (10) with the shaft back and forth in the axial direction of the grindstone shaft (12).
A grinding fluid jetting port (31) of the grinding fluid supply unit (30) is disposed to be able to discharge the grinding fluid to an outer peripheral surface of the base (11) of the grindstone (10) with the shaft, specifically, an outer peripheral surface of the truncated conical portion (15). The grinding fluid supply unit (30) may supply the grinding fluid from the grinding fluid jetting port (31) in the direction perpendicular to the grindstone shaft (12) or a direction inclined from the perpendicular direction toward the grindstone (13). A pipe of the grinding fluid supply unit (30) to the grinding fluid jetting port (31) may be disposed along an outer wall (non-rotating portion) of the wheel head (20).
In the grinding device (100), the grindstone (13) may be rotated at a high speed, and the workpiece (1) may be rotated at a low speed. In this case, the workpiece (1) may be held on a worktable that is rotatable. Alternatively or in addition to the configuration in which the grindstone (10) with the shaft is moved back and forth in the axial direction of the grindstone shaft (12) together with the wheel head (20), the workpiece (1) may be moved back and forth in the axial direction of the grindstone shaft (12) together with a worktable holding the workpiece (1).

For the internal grinding of the workpiece (1), the grindstone (13) is inserted in a recess (a target hole to be machined) formed in the workpiece (1) and is rotated to grind the inner surface of the target hole. The grindstone (13) inserted in the target hole of the workpiece (1) is movable in the axial direction of the grindstone shaft (12) and also in the radial direction of the grindstone shaft (12). This makes it possible to process the inner surface of the target hole into a desired shape.
When the internal grinding of the workpiece (1) is performed by the grinding method of the present embodiment, the grindstone (13) is moved in the axial direction of the grindstone shaft (12). This changes the distance between the base (11) and the workpiece (1) (an end surface of the workpiece (1) facing the base (11)). In the present embodiment, the grindstone (10) with the shaft that has the short grindstone shaft (12) is used so that the distance between the base (11) and the workpiece (1) is equal to or less than 5 mm when the innermost portion of the target hole of the workpiece (1) is ground with the grindstone (13) without bringing the base (11) and the workpiece (1) into contact. Thus, while the flow direction of the grinding fluid discharged toward the outer peripheral surface of the base (11) is changed by a guide structure (15a, 17, 18, 18a) provided on the base (11), the grinding fluid is supplied to the grinding portion of the workpiece (1). In other words, the base (11) is provided with the guide structure (15a, 17, 18, 18a) so that the grinding fluid discharged toward the outer peripheral surface of the base (11) is supplied to the grinding portion of the workpiece (1) while the flow direction of the grinding fluid is changed. The guide structure (15a, 17, 18, 18a) allows the grinding fluid blown to the outer peripheral surface of the base (11) to be supplied to the grindstone shaft (12) and the grindstone (13) located radially inside against the centrifugal force while the maximum rigidity of the grindstone shaft (12) and the base (11) is maintained. The guide structure (15a, 17, 18, 18a) on the outer peripheral surface of the base (11) changes the flow direction of the grinding fluid from the direction of the grinding fluid jetted from the grinding fluid jetting port (31) to the direction toward the grinding portion of the workpiece (1).
Specifically, as illustrated in FIG. 4, the outer peripheral surface of the truncated conical portion (15) of the base (11) may be formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a). The concave surface (15a) has an inclination angle θ of 0° or more and 20° or less with respect to the grindstone shaft (12) (a center axis J of the grindstone shaft (12)) at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (15a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. The angle φ is equal to the inclination angle of the concave surface (15a) with respect to the center axis J of the grindstone shaft (12) at the bottom of the truncated conical portion (15).
The shape of the base (11) is obtained by combining the truncated conical portion (15) having the outer peripheral surface inclined at an angle of, for example, 45° with respect to the bottom surface and the cylindrical portion (16) in which the fixture member (14) for fixing the base (11) to the wheel head (20) is inserted. However, in the example shown in FIG. 4, the outer peripheral surface of the truncated conical portion (15) is shaped into the curved concave surface (15a). As illustrated in FIG. 4, when the grindstone (10) with the shaft is viewed from the direction perpendicular to the grindstone shaft (12), a curve (e.g., a parabola or an arc) which is the concave surface (15a) starts to extend from the top of the truncated conical portion (15) having a diameter slightly larger (e.g., by about 1 to 2 mm) than the diameter of the grindstone (13) at an inclination angle θ of about 0° to 20° with respect to the grindstone shaft (12), and the inclination angle θ greatly changes toward the bottom of the truncated conical portion (15). The curve is connected to the outer peripheral surface of the cylindrical portion (16) having a larger diameter than the grindstone (13) at an angle φ of 40° or more and 90° or less.
The rigidity of the base (11) shaped as shown in FIG. 4 slightly decreases compared to when the outer peripheral surface of the truncated conical portion (15) is not formed into the concave surface (15a). However, the decrease in the rigidity of the base (11) is negligible compared to the increase in the rigidity by shortening the grindstone shaft (12).
On the other hand, when the base (11) is shaped as shown in FIG. 4, the inclination angle θ of the concave surface (15a) as the outer peripheral surface of the truncated conical portion (15) with respect to the grindstone shaft (12) increases from the top to the bottom of the truncated conical portion (15). Thus, the jetting pressure of the grinding fluid causes the grinding fluid discharged toward the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the concave surface (15a). Further, the inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is as gentle as 0° or more and 20° or less at the top of the truncated conical portion (15), allowing the grinding fluid to be supplied from the top of the truncated conical portion (15) to the grinding portion of the workpiece (1) along the grindstone shaft (12).
When the base (11) is shaped as shown in FIG. 4, the inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) increases from the top to the bottom of the truncated conical portion (15), and the concave surface (15a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. Thus, even if the grinding fluid is discharged in the direction perpendicular or substantially perpendicular to the grindstone shaft (12) (the center axis J of the grindstone shaft (12)) toward the outer peripheral surface of the truncated conical portion (15), specifically, the outer peripheral surface near the bottom of the truncated conical portion (15), the grinding fluid is less likely to splash back from the outer peripheral surface of the base (11). This can enhance the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1). This effect is enhanced as the difference between the inclination angle θ of the concave surface (15a) of the truncated conical portion (15) on which the grinding fluid from the grinding fluid jetting port (31) directly hits and the angle of the grinding fluid jetted from the grinding fluid jetting port (31) (an angle with respect to the grindstone shaft (12)) is reduced. Thus, if the grinding fluid is jetted at an angle of 90° or approximately 90°, the inclination angle θ of the concave surface (15a) of the truncated conical portion (15) on which the grinding fluid from the grinding fluid jetting port (31) directly hits may be 70° or more and 90° or less.

[First Variation]

As a first variation shown in FIG. 5, the outer peripheral surface of the truncated conical portion (15) of the base (11) may be provided with a plurality of twisted blades (17) as the guide structure (15a, 17, 18, 18a). The plurality of blades (17) extend from the top to the bottom of the truncated conical portion (15) to be twisted in the rotation direction of the grindstone (10) with the shaft, that is, the base (11). Thus, rotating the plurality of blades (17) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the outer peripheral surface of the base (11) between the blades (17) against the centrifugal force. This allows the grinding fluid to be discharged from the top of the truncated conical portion (15) in the direction along the grindstone shaft (12), and the grinding fluid can be supplied to the grindstone (13), that is, the grinding portion of the workpiece (1), through a gap between the target hole of the workpiece (1) and the grindstone shaft (12).
In the first variation shown in FIG. 5, the outer peripheral surface of the truncated conical portion (15) between the plurality of blades (17) may be formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a). The inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) (the center axis J) is 0° or more and 20° or less at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (15a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. This configuration can provide the same effects as those of the embodiment shown in FIG. 4 in addition to the effects described above.
In the first variation shown in FIG. 5, the plurality of blades (17) may be formed on the outer peripheral surface of the truncated conical portion (15) of the base (11) without forming the outer peripheral surface into the concave surface (15a). This configuration can also provide the above-described effect. The plurality of blades (17) may be provided only in part of the area between the top and the bottom of the truncated conical portion (15), for example, only around the top.

[Second Variation]

As a second variation shown in FIG. 6, the outer peripheral surface of the truncated conical portion (15) of the base (11) may be provided with a plurality of twisted grooves (18) as the guide structure (15a, 17, 18, 18a). The plurality of grooves (18) extend from the top to the bottom of the truncated conical portion (15) to be twisted in the rotation direction of the grindstone (10) with the shaft, that is, the base (11). Thus, rotating the plurality of grooves (18) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the plurality of grooves (18) against the centrifugal force. This allows the grinding fluid to be discharged from the top of the truncated conical portion (15) in the direction along the grindstone shaft (12), and the grinding fluid can be supplied to the grindstone (13), that is, the grinding portion of the workpiece (1), through a gap between the target hole of the workpiece (1) and the grindstone shaft (12). The configuration of the second variation shown in FIG. 6 corresponds to a configuration obtained by increasing the width (width in the rotation direction) of the plurality of blades (17) of the first variation shown in FIG. 5.
In the second variation shown in FIG. 6, the bottom surface of each of the plurality of grooves (18) may be formed into a concave surface (18a) as the guide structure (15a, 17, 18, 18a). The inclination angle θ of the concave surface (18a) with respect to the grindstone shaft (12) (the center axis J) is 0° or more and 20° or less at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (18a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. That is, the concave surface (18a) which is the bottom surface of each groove (18) is curved similarly to the concave surface (15a) which is the outer peripheral surface of the truncated conical portion (15) of the embodiment shown in FIG. 4. Thus, for the same reason described in the embodiment shown in FIG. 4, the jetting pressure of the grinding fluid causes the grinding fluid discharged toward the outer peripheral surface of the base (11) to easily flow along the grooves (18) of the truncated conical portion (15), remarkably exhibiting the above-described effect. In this case, if the outer peripheral surface of the truncated conical portion (15) between the grooves (18) is curved similarly to the concave surface (15a) which is the outer peripheral surface of the truncated conical portion (15) of the embodiment shown in FIG. 4, the splashing of the grinding fluid can be further reduced, exhibiting the above-described effects more remarkably.
In the second variation shown in FIG. 6, the bottom surface of each groove (18) may not be formed into the concave surface (18a). This configuration can also provide the above-described effect. The plurality of grooves (18) may be provided only in part of the area between the top and the bottom of the truncated conical portion (15), for example, only around the top.

[Third Variation]

A third variation shown in FIG. 7 is different from the first variation shown in FIG. 5 in that a lid member (19) is provided on the truncated conical portion (15) to cover the plurality of blades (17). The lid member (19) may be joined to the plurality of blades (17) by brazing. The lid member (19) may be provided to partially cover each of the plurality of blades (17). When the lid member (19) is provided, the grinding fluid is supplied to the outer peripheral surface of the truncated conical portion (15) through a gap between the lid member (19) and the cylindrical portion (16). This can keep the grinding fluid from splashing off the outer peripheral surface of the truncated conical portion (15), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
In the second variation shown in FIG. 6, a lid member similar to the lid member (19) of the third variation may be provided on the truncated conical portion (15) to cover the plurality of grooves (18). This can provide the same effects as those of the third variation.

[Fourth Variation]

A fourth variation shown in FIG. 8 is different from the third variation shown in FIG. 7 in that instead of the lid member (19) provided on the truncated conical portion (15), a non-rotating umbrella-shaped member (21) that is attached to the outer wall (non-rotating portion) of the wheel head (20) with an arm covers the outer peripheral surface of the base (11) (particularly, the truncated conical portion (15)). When the umbrella-shaped member (21) is provided, the grinding fluid is supplied to the outer peripheral surface of the truncated conical portion (15) through a gap between the umbrella-shaped member (21) and the wheel head (20). This can keep the grinding fluid from splashing off the outer peripheral surface of the truncated conical portion (15), that is, the base (11), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
In the fourth variation shown in FIG. 8, the umbrella-shaped member (21) is provided to cover the outer peripheral surface of the base (11) of the first variation shown in FIG. 5, but similarly, the umbrella-shaped member (21) may be provided to cover the outer peripheral surface of the base (11) of the embodiment shown in FIG. 4 or the outer peripheral surface of the base (11) of the second variation shown in FIG. 6.

The grinding method of the embodiment is a method for performing internal grinding of the workpiece (1) by rotating the grindstone (13) attached to the grindstone shaft (12) protruding from the base (11). The distance between the base (11) and the workpiece (1) during the grinding changes, the distance is equal to or less than 5 mm when the innermost portion of the workpiece (1) is ground, and the grinding fluid discharged toward the outer peripheral surface of the base (11) is supplied to the grinding portion of the workpiece (1) while the flow direction of the grinding fluid is changed by the guide structure (15a, 17, 18, 18a) provided on the base (11).
By the grinding method of the embodiment, although the grindstone shaft (12) is shortened to set the distance between the base (11) and the workpiece (1) during the grinding equal to or less than 5 mm, the guide structure (15a, 17, 18, 18a) provided on the base (11) allows sufficient supply of the grinding fluid to the grinding portion of the workpiece (1). This can reduce grinding burn, and can provide the grindstone (10) with the shaft with longer life by reducing the wear of the grindstone (13). Further, with the grindstone shaft (12) shortened, the machining accuracy can be kept from decreasing due to deflection of the grindstone shaft (12), and the time required for the spark-out grinding can be reduced. This shortens the machining time, that is, improves the machining speed.
When the internal grinding of the workpiece (1) is performed by the grinding method of the embodiment with the base (11) covered with the non-rotating umbrella-shaped member (21), the grinding fluid can be kept from splashing off the outer peripheral surface of the base (11), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
The grindstone (10) with the shaft of the embodiment includes the base (11), the grindstone shaft (12) having one end supported by the base (11), and the grindstone (13) that is attached to the grindstone shaft (12) and rotates together with the grindstone shaft (12) to perform the internal grinding of the workpiece (1). The base (11) is provided with the guide structure (15a, 17, 18, 18a) so that the grinding fluid discharged toward the outer peripheral surface of the base (11) is supplied to the grinding portion of the workpiece (1) while the flow direction of the grinding fluid is changed.
In the grindstone (10) with the shaft of the embodiment, although the grindstone shaft (12) is shortened to set the distance between the base (11) and the workpiece (1) during the grinding equal to or less than 5 mm, the guide structure (15a, 17, 18, 18a) provided on the base (11) allows sufficient supply of the grinding fluid to the grinding portion of the workpiece (1). This can reduce grinding burn, and can provide the grindstone with the shaft with longer life by reducing the wear of the grindstone (13). Further, with the grindstone shaft (12) shortened, the machining accuracy can be kept from decreasing due to deflection of the grindstone shaft (12), and the time required for the spark-out grinding can be reduced. This shortens the machining time, that is, improves the machining speed.
On the other hand, when a supply pipe for the grinding fluid is bent along the axial direction of the grindstone shaft so that the port for jetting the grinding fluid is disposed toward the target hole as in the previous manner, the grinding fluid jetting port (31) can be disposed toward the target hole if the grindstone shaft (12) is long as in Comparative Example 1 shown in FIG. 9, but the grinding fluid jetting port (31) cannot be disposed toward the target hole if the grindstone shaft (12) is short as in Comparative Example 2 shown in FIG. 10. In Comparative Examples 1 and 2 shown in FIGS. 9 and 10, the same components as those of the embodiment shown in FIG. 2 are denoted by the same reference numerals. As described above, the grindstone shaft should be kept as short as possible to ensure the rigidity. However, when the distance between the workpiece and the base of the grindstone shaft or the wheel head is about 5 mm or less, the target hole of the workpiece is blocked by the base or the wheel head as in Comparative Example 2 shown in FIG. 10, and the grinding fluid jetting port cannot be appropriately disposed. In this case, the grinding fluid cannot be sufficiently supplied to the grinding portion of the workpiece, causing problems such as grinding burn involving the temperature rise of the grinding portion to 500°C or higher, and shortened life of the grindstone, or the like.
In the grindstone (10) with the shaft of the embodiment, the base (11) includes the truncated conical portion (15) having the grindstone shaft (12) at the top and the cylindrical portion (16) connected to the bottom of the truncated conical portion (15), and the outer peripheral surface of the truncated conical portion (15) may be formed into the concave surface (15a) as the guide structure (15a, 17, 18, 18a). The inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (15a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. Thus, the jetting pressure of the grinding fluid causes the grinding fluid discharged to the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the outer peripheral surface of the truncated conical portion (15), that is, the concave surface (15a). Further, the inclination of the concave surface (15a) with respect to the grindstone shaft (12) is gentle at the top of the truncated conical portion (15), allowing the grinding fluid to be supplied from the top of the truncated conical portion (15) to the grinding portion of the workpiece (1) along the grindstone shaft (12).
In the grindstone (10) with the shaft of the embodiment, the base (11) includes the truncated conical portion (15) having the grindstone shaft (12) at the top and the cylindrical portion (16) connected to the bottom of the truncated conical portion (15), and the outer peripheral surface of the truncated conical portion (15) may be provided with a plurality of twisted blades (17) as the guide structure (15a, 17, 18, 18a). In this configuration, rotating the plurality of blades (17) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the outer peripheral surface of the base (11) against the centrifugal force. This allows the grinding fluid to be supplied from the top of the truncated conical portion (15) to the grinding portion of the workpiece (1) along the grindstone shaft (12). In this case, the outer peripheral surface of the truncated conical portion (15) between the plurality of blades (17) may be also formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a). The inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (15a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. Thus, the jetting pressure of the grinding fluid causes the grinding fluid discharged to the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the concave surface (15a), supplying the grinding fluid more effectively to the grinding portion of the workpiece (1). Further, when the truncated conical portion (15) is provided with the lid member (19) covering the plurality of blades (17), the grinding fluid can be kept from splashing off the outer peripheral surface of the truncated conical portion (15), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).
In the grindstone (10) with the shaft of the embodiment, the base (11) includes the truncated conical portion (15) having the grindstone shaft (12) at the top and the cylindrical portion (16) connected to the bottom of the truncated conical portion (15), and the outer peripheral surface of the truncated conical portion (15) may be provided with a plurality of twisted grooves (18) as the guide structure (15a, 17, 18, 18a). In this configuration, rotating the plurality of grooves (18) together with the base (11) allows the grinding fluid discharged toward the outer peripheral surface of the base (11) to flow toward the grindstone shaft (12) along the plurality of grooves (18) against the centrifugal force. This allows the grinding fluid to be supplied from the top of the truncated conical portion (15) to the grinding portion of the workpiece (1) along the grindstone shaft (12). In this case, the bottom surface of each groove (18) may be formed into a concave surface (18a) as the guide structure (15a, 17, 18, 18a). The inclination angle θ of the concave surface (18a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15), and the inclination angle θ increases from the top to the bottom of the truncated conical portion (15). The concave surface (18a) is connected to the outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less. Thus, the jetting pressure of the grinding fluid causes the grinding fluid discharged toward the outer peripheral surface of the truncated conical portion (15) of the base (11) to flow along the bottom surface of each groove (18), that is, the concave surface (18a), supplying the grinding fluid more effectively to the grinding portion of the workpiece (1). Further, when the truncated conical portion (15) is provided with the lid member (19) covering the plurality of grooves (18), the grinding fluid can be kept from splashing off the outer peripheral surface of the truncated conical portion (15), enhancing the effect of intensively supplying the grinding fluid to the grinding portion of the workpiece (1).

(Other Embodiments)

In the above-described embodiment and variations, the concave surface (15a, 18a), the blades (17), and the grooves (18) formed on the outer peripheral surface of the truncated conical portion (15) are described as examples of the guide structure (15a, 17, 18, 18a). However, the present disclosure is not limited to these examples, and the base (11) may be provided with another guide structure so that the grinding fluid discharged toward the outer peripheral surface of the base (11) is supplied to the grinding portion of the workpiece (1) while the flow direction of the grinding fluid is changed.
It will be understood that the embodiments and variations described above can be modified with various changes in form and details without departing from the spirit and scope of the claims. The foregoing embodiments and variations may be appropriately combined or replaced as appropriate.

INDUSTRIAL APPLICABILITY

As described above, the present disclosure is useful for a grinding method and a grindstone with a shaft.

DESCRIPTION OF REFERENCE CHARACTERS

1: Workpiece
10: Grindstone with Shaft
11: Base
12: Grindstone Shaft
13: Grindstone
15: Truncated Conical Portion
15a: Concave Surface (Guide Structure)
16: Cylindrical Portion
17: Blade (Guide Structure)
18: Groove (Guide Structure)
18a: Concave Surface (Guide Structure)
19: Lid Member
21: Umbrella-Shaped Member

Claims

A grinding method for performing internal grinding of a workpiece (1) by rotating a grindstone (13) attached to a grindstone shaft (12) protruding from a base (11), wherein
a distance between the base (11) and the workpiece (1) during the grinding changes, and the distance is equal to or less than 5 mm when the innermost portion of the workpiece (1) is ground, and

a grinding fluid discharged toward an outer peripheral surface of the base (11) is supplied to a grinding portion of the workpiece (1) while a flow direction of the grinding fluid is changed by a guide structure (15a, 17, 18, 18a) provided on the base (11).
The grinding method of claim 1, wherein
the internal grinding of the workpiece (1) is performed with the base (11) covered with a non-rotating umbrella-shaped member (21).
A grindstone with a shaft, comprising:
a base (11);

a grindstone shaft (12) having one end supported by the base (11); and

a grindstone (13) attached to the grindstone shaft (12) and configured to rotate together with the grindstone shaft (12) to perform internal grinding of a workpiece (1),

wherein

the base (11) is provided with a guide structure (15a, 17, 18, 18a) so that a grinding fluid discharged toward an outer peripheral surface of the base (11) is supplied to a grinding portion of the workpiece (1) while a flow direction of the grinding fluid is changed.
The grindstone with the shaft of claim 3, wherein
the base (11) includes
a truncated conical portion (15) having the grindstone shaft (12) at a top, and

a cylindrical portion (16) connected to a bottom of the truncated conical portion (15),

an outer peripheral surface of the truncated conical portion (15) is formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a),

an inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15),

the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and

the concave surface (15a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
The grindstone with the shaft of claim 3, wherein
the base (11) includes
a truncated conical portion (15) having the grindstone shaft (12) at a top, and

a cylindrical portion (16) connected to a bottom of the truncated conical portion (15), and

an outer peripheral surface of the truncated conical portion (15) is provided with a plurality of twisted blades (17) as the guide structure (15a, 17, 18, 18a).
The grindstone with the shaft of claim 5, wherein
the outer peripheral surface of the truncated conical portion (15) between the plurality of blades (17) is also formed into a concave surface (15a) as the guide structure (15a, 17, 18, 18a),

an inclination angle θ of the concave surface (15a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15),

the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and

the concave surface (15a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
The grindstone with the shaft of claim 5 or 6, wherein
a lid member (19) is provided on the truncated conical portion (15) to cover the plurality of blades (17).
The grindstone with the shaft of claim 3, wherein
the base (11) includes
a truncated conical portion (15) having the grindstone shaft (12) at a top, and

a cylindrical portion (16) connected to a bottom of the truncated conical portion (15), and

an outer peripheral surface of the truncated conical portion (15) is provided with a plurality of twisted grooves (18) as the guide structure (15a, 17, 18, 18a).
The grindstone with the shaft of claim 8, wherein
a bottom surface of each of the plurality of grooves (18) is also formed into a concave surface (18a) as the guide structure (15a, 17, 18, 18a),

an inclination angle θ of the concave surface (18a) with respect to the grindstone shaft (12) is 0° or more and 20° or less at the top of the truncated conical portion (15),

the inclination angle θ increases from the top to the bottom of the truncated conical portion (15), and

the concave surface (18a) is connected to an outer peripheral surface of the cylindrical portion (16) at the bottom of the truncated conical portion (15) at an angle φ of 40° or more and 90° or less.
The grindstone with the shaft of claim 8 or 9, wherein
a lid member (19) is provided on the truncated conical portion (15) to cover the plurality of grooves (18).