JPS58217224A - Internal surface grinding method - Google Patents

Abstract

PURPOSE:To enable a workpiece to be processed with an extremely small current while allowing the processing surface to be always activated by scraping off an oxidized film, etc., produced by an electrolytic action directly after they are produced by dividing a conductive band and allowing non-conductive abrasive bands to exist among said divided conductive bands. CONSTITUTION:The columnar whetstone 1 is formed by sintering non-conductive abrasive grains using a non-conductive binder. A conductive substance is buried in long grooves along the body circumferential surface to form conductive bands 2, and said conductive bands 2 and abrasive bands 3 made of non-conductive abrasive grains are alternately formed longitudinally in approximately parallel to each other. The whetstone 1 is only capable of rotating on its own axis, and rotary feed opposite to the turning direction of a material M to be cut along the wall surface within an opening H is provided. At the instant the material M and the conductive band 2 of the whetstone 1 contact with each other, the surface of the material M is electrolyzed and melted to produce metal ions. Since the abrasive bands 3 pass through the neighborhood of said surface, the abrasive grains scrape off melted portions and an oxidized film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal grinding method for grinding and finishing the inner surface of a cylinder using a grinding wheel capable of performing electrical and mechanical actions alternately.

Machining methods for the inner surface of a cylinder include boring, hammering, and grinding, but these finishing methods do not provide sufficient accuracy or surface roughness for internal combustion engine cylinder inner surfaces, high-speed bearing surfaces, etc.

In particular, for recently developed cemented carbides, conventional mechanical grinding techniques had limitations in terms of finishing accuracy and efficiency of the inner surface.

Furthermore, it is believed that the difficulty in controlling the dimensions and shape during precision line processing of ceramics limits its range of application.

The present invention has been made to improve the above-mentioned points, and improves the efficiency and efficiency of the inner surface of holes in difficult-to-cut materials such as cemented carbide and ceramics.
The object of the present invention is to provide an internal grinding method that enables accurate grinding.

Next, an example will be described.

<A> Column-shaped grindstone body The column-shaped body (11) of the grindstone (1) is a non-conductive cylindrical body made by baking non-conductive abrasive grains with a non-conductive binder.

As an example of the abrasive grain, green car Hz random, white alundum, pink alundum, silica, etc. can be used.

<Opening> Conductive band A long groove of a certain depth is formed on the circumferential surface of this cylindrical body (11) toward the axis, parallel to the longitudinal direction of the shaft (4) or at a certain intersecting angle. Open multiple cylinders B at regular intervals or at irregular intervals.

A conductive material is buried in the long groove to form a conductive band (2).

The following materials can be used as the conductive material.

1) Fine powder of metals (Muta, Ou%Ni, etc.) or alloys made of these as a paste is hardened with conductive paste (phenol epoxy, Adalite, etc.).

2) A mixture of the following hard nonmetallic compound in 1) above.

Diamond) 41 Case Random (8i0), Silica (5iOz), Zero Nitride (BN) (Carbonized Zero (B2O), etc.).

3) A mixture of the following superhard substances in 1) above.

Alumina (kOs), tungsten carpai) (
WO), titanium carbide (TiO), titanium nitride (TiN), tantalum carbide (Tag), niobium carbide (NbO), etc.

4) A mixture of 1) above with the following lubricating substance.

Graphite, carzene, molybdenum disulfide, etc.

Kuno・〉 A donut-shaped current carrying plate (5) is attached to the end face of the current carrying plate main body (11) to electrically connect between the shaft (4) and each conductive band (2).

As a result, a current-carrying plate (5) is placed around the cylindrical main body (11).
Conductive bands (2) electrically connected to the abrasives and polishing bands (3) made of non-conductive abrasive grains are alternately formed substantially parallel to the longitudinal direction.

Next, the grinding method will be explained.

<A> Object to be ground prepared for grinding (M) A positive electrode is connected to K, and a negative electrode is connected to the shaft (4) of the grindstone (1) placed in the opening (n), and electricity is applied.

At the same time, rotation is given to the grindstone (1) and/or the object to be ground (M), and machining fluid is supplied.

The grindstone (1) is given only its own rotation, or is given rotational feed along the wall surface in the opening (H) in a direction opposite to the rotational direction of the object to be ground (M). (Figure 4) As a result, the object to be ground (M)
The conductive band (2) and the abrasive body (3) alternately pass through the contact surface.

Further, when the opening (fl) is a long hole, the grinding wheel (1) K gives reciprocating motion in the longitudinal direction of the shaft (4) in addition to the above-mentioned movement.

<Mouth> The electrolytically ground object (M) and the conductive band (2) of the grindstone (1) are in contact -5
= At the moment of contact, electrolysis occurs on the surface of the rigid material (M), and the surface of the rigid material (M) turns into metal ions and begins to melt.

In the case of metal carbides such as cemented carbide 0, which are difficult to metal ionize, metal oxides are produced by the interaction of oxygen generated by water electrolysis and the material to be stiffened (M).

Mechanical grinding action Immediately after this, the abrasive band (3) of the whetstone (1) passes through, so the abrasive grains scrape off the dissolved parts and oxide film. That is, the processed surface is always activated because the oxide film and the like are removed immediately after they are generated.

Therefore, electrolysis is possible with a small current.

Unlike conventional electrolytic grinding wheels, electrical discharge machining has discontinuous conductive bands (2).

Therefore, one conductive band (2) only momentarily contacts the material to be ground (M).

As a result, a discharge phenomenon occurs due to the pulsed current, and sparks fly between the two at the moment of contact.

6. The spark immediately turns into a thin arc column, that is, a flow of electrons with extremely high current density, melting and blowing away one point on the rigid material (M).

When electrical discharge machining is performed in this manner, K is obtained.

<3> Embodiment 2 In the above embodiment, the case where the grinding is carried out by applying a direct current has been explained in detail, but it is also possible to use an alternating current.

When an alternating current is applied, it is now possible to electrically grind non-conductive grinding objects (M), which were conventionally considered impossible to process.

That is, ceramic is a dielectric material and a non-conductor of heat.

Therefore, a resonance effect occurs due to the high frequency power, and the surface layer of the ceramic becomes conductive.

As a result, an electric field and a discharge phenomenon were generated, and grinding could be performed in the same manner as in the previous example.

<4> Example 3 In each of the above examples, conductive bands and non-conductive bands (abrasive bands) were provided alternately.

However, even if a completely conductive grindstone without a non-conductive band is used, the same grinding effect as described above can be expected.

To do this, the voltage between the workpiece to be ground (M) and the grinding wheel (1') must be maintained at the boundary between positive and negative voltage for a certain period of time (1) as shown in Figure 5.
Provides a voltage waveform through zero voltage.

Similarly, it is also possible to supply a voltage waveform in which only positive voltage or negative voltage is generated throughout the zero voltage time6 (6th
(Figure) Next, the case of grinding using this conductive grindstone (1') will be explained.

The motion acting on the grinding wheel (1') and the object to be ground (M) is similar to the previous embodiment.

Therefore, a voltage having the above waveform is applied as the grindstone (1') rotates.

The time CP=> when the supply voltage is positive or negative is the grinding wheel (1'
) and the object to be ground (M), and electrolytic action and discharge due to pulse waves occur.

During time (1) when the supply voltage is zero, no current is applied and mechanical grinding by the abrasive grains of the grindstone (1') proceeds.

Since both operations are repeated alternately after a short period of time, it is possible to perform extremely efficient grinding and obtain a ground surface with high precision, similar to the previous embodiment.

In particular, by increasing the frequency of the voltage waveform provided, even if the object to be ground (M) is a non-conductive material such as glass, ceramic, or crystal, there is a so-called electrostatic capacity between the grinding wheel (1') and the object to be ground (M). It can be easily processed by generating an energized state.

Since the present invention is as described above, the following effects can be expected. (a) The conductive band is divided into parts, and a non-conductive polishing belt exists between them.

Therefore, oxide films and the like produced by electrolytic action are scraped off the moment they occur, and the machined surface is constantly activated.

Therefore, compared to conventional electrolytic grinding, the It is now possible to process with flow.

<Exposure> Since the conductive band is discontinuous, the conductive band only momentarily contacts the rigid material.

At the moment of contact, an electrical discharge phenomenon occurs between the two, producing sparks that melt and blow away the machined surface, resulting in electrical discharge machining.

As described above, the method of the present invention consists of ■electrolysis, ■discharge, and ■
Since grinding is performed using two mechanical actions, extremely efficient internal grinding is possible.

Since the grinding wheel is prevented from clogging due to the generation of pulses, the scooping surface and nibbling surface of the grinding wheel are always secured and internal grinding is performed in the best condition.

[Brief explanation of drawings]

Figure 1: An explanatory diagram of one embodiment of the grinding wheel used for grinding according to the present invention. Figure 2: A partial sectional view of the tip of the whetstone in Figure 1. Figure 3.4: An explanatory diagram of the 11 o'clock time to grind. Figure 5.6. : Explanatory diagram of pulse waves used in other examples 1.1 □: Grinding wheel 2: Electromagnetic band 10- 3: Polishing band 4: Shaft 5: Current-carrying plate Patent applicant Applied Magnetic Research Institute Ltd.-11-・ゑFigure 4H Figure 5 p-12←p→ Flute 6-p -+-t -+-p times

Claims (1)

[Claims] (1) A grinding wheel is used in which non-conductive polishing bands and conductive bands are alternately formed on the curved surface of the bar-shaped grinding wheel, and a current is applied between the discharge band of the grinding wheel and the object to be ground. An internal grinding method characterized by the fact that a conductive grinding wheel is used, and a predetermined voltage with zero voltage is applied between the grinding wheel and the object to be ground. An internal grinding method characterized by