JPH0780121B2 - How to condition an ultra-strong polishing horn - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to honing finishes, and more particularly to conditioning ultra-high strength abrasive materials used in honing finishes.

Although horns containing technical diamond are hard and therefore have a high abrasive effect, they have the disadvantage that the diamond cannot withstand high temperatures and reacts with the steel or iron to be honed. Further, it is difficult to firmly bond the diamond and the metal bonding matrix supporting the diamond, and as a result,
Diamond prematurely detaches from the metal bond matrix.

Also, horns containing vitrified and bonded cubic boron nitride (CBN) are currently in use. Cubic boron nitride is extremely hard, and the bonding matrix is strongly bonded to the surface of the cubic boron nitride particles. Therefore, most of the boron nitride particles do not detach from the binding matrix before they wear. Yet another important advantage is that the cubic boron nitride crystals fracture at the cleavage planes to re-form sharp cutting edges in order to anchor the particles by a strong bond.

The present invention relates to conditioning horns containing vitrified bonded cubic boron nitride or industrial diamond or the like. As used herein, the term "super-strength abrasive" includes not only these two materials, but also other equivalent materials used in horn finishing or that may be used in the future. Is intended.

For example, when honing a cylinder bore of an engine, the resulting surface finish depends largely on how the phon is prepared. These horns are typically strips mounted on an expandable honing head. The honing head is a drum formed of a plurality of sectors that can move radially in synchronism with each other to press the horn into contact with the inner surface of the cylinder bore. The drum rotates and moves axially with respect to the cylinder, often causing the horn to move along a helical path having a predetermined helix angle. The cylinder bore is formed with a spiral groove so that lubricating oil can be retained on the cylinder surface for the purpose of lubrication. It is essential that the surface of the cylinder bore not be dented by dragging, i.e. the surface should not be distorted or stressed. Therefore the surface finish is very important and the horn must be well prepared.

Currently, horns containing diamond or cubic boron nitride are manufactured using a vitrified wheel or grinding wheel mounted on a honing head, or honing drum. The grinding wheel is rotated and brought into tangential contact with a drum rotating at a low speed. The grinding wheel and the drum are moved relative to each other in the axial direction, whereby the horn is ground to the cylindrical surface. When a horn containing metal bonded diamond or cubic boron nitride is used, a relatively slow spinning wheel of silicon carbide or similar material is used to make the horn. It

The result of this operation is a horn having a relatively smooth cylindrical surface with the abrasive particles substantially flush with the binder or matrix surface. In this state, the cylindrical surface is not ready for use. The horn can still be used in this state, but its ability to remove metal is such that the binder abrades the work material in contact with it and abrades it to the extent that it exposes abrasive particles. Until, it is not high enough to show effective working capacity. Therefore,
Prior to use, the horn is ground with a natural grindstone to roughen its surface and expose diamond or cubic boron nitride particles, but this method provides an accurate and repeatable horn surface finish. Is difficult to do.

A horn that has been adjusted to an incorrect state initially
It exhibits unpredictable properties close to those of burnishing. In such cases, the horn requires higher contact pressure to machine, resulting in surface metal deformation on the honed surface. Primarily for this reason, these materials have not been used commercially for cylinder bores.

The surface of the horn wears out during use, allowing a consistent and consistent surface finish after several workpieces have been honed. However, the results obtained immediately after conditioning the horn are unpredictable.

The present invention alleviates the above disadvantages and allows the horn to be used immediately, allowing the condition of the surface of the honed workpiece to be accurately determined by a conditioning operation. It is intended to provide a method of conditioning a.

The present invention rotates a drum carrying a horn, rotates a diamond grinding wheel, presses the diamond grinding wheel and the horn so as to contact each other, and relatively moves the diamond grinding wheel and the horn in the axial direction. In the method for conditioning a vitrified, bonded, ultra-strong abrasive horn, the surface speed of the horn is significantly greater than the surface speed of the diamond grinding wheel, and the horn and the diamond grinding wheel are Of the vitrified binder and the super-strong abrasive material by contact with the horn, and controlling the machining depth and the axial movement speed to determine the surface finish of the machined workpiece by the horn. A method characterized by the above is provided.

When grinding the surface, the surface finish state can be changed by changing the conditions used for shaping the grinding wheel. The grinding wheel is shaped by rotating it at a high operating speed and moving axially a diamond or diamond wheel (ie, a diamond grinding wheel) that abrades the surface of the grinding wheel relative to the grinding wheel. The speed of rotation of the grinding wheel during shaping with respect to a fixed diamond wheel or a rotating diamond wheel modifies the effective abrasive hardness of the grinding wheel. Further, the surface finish state of the workpiece ground by the grinding wheel changes depending on the axial movement speed of the grinding wheel with respect to the diamond or the diamond wheel during shaping. Such a grinding wheel can be used immediately after shaping, unlike a horn shaped by a conventional method. Further, the surface finish state of the workpiece can be adjusted depending on how the grinding wheel is shaped.

The invention is based on the recognition that in the above method, if a drum carrying a horn is used instead of a grinding wheel, the same results will be obtained with a horn as with a grinding wheel.

Such a method of the present invention differs from the prior art that has been used to condition the horn by rotating the drum at a low speed and rotating the grinding wheel at a higher speed that is not directly related to the speed of the drum. Notably different. Given that the relative velocities of the contacts may be important, it may seem at first glance that the same effect can be obtained by rotating either the diamond wheel or the grinding wheel and the drum at high speed. However, in practice,
It turned out not to be. It is considered that the reason is that the surface density, particle size and strength of the abrasive particles of the grinding wheel and the horn to be shaped are not the same. By conditioning the horn in the manner proposed by the present invention, the horn can be used without any further adjustment, and the surface speed, depth of cut (or working depth) and speed of movement adjusted. Therefore, it has been found that the surface finish obtained by using the horn can be adjusted.

The surface of the conditioning drum is preferably moved at a speed at least equal to the speed of the activated drum.
This ensures that the horn works properly at normal speed conditions to maintain proper clearance and proper machining. Even at lower speeds,
Similar results are obtained with a corresponding reduction in grinding wheel speed, but longer horn preparation times are required.

Experiments have shown that the relative particle size of the abrasive particles of the conditioning wheel is important in order to obtain the desired grinding action. The particles of the conditioning wheel should be considerably larger than the particles of the horn, preferably in the range of 4 to 5 times the particles of the horn.

The method of the present invention is applicable not only to expanding honing heads of the type used for honing cylinder bores, but also to tapered one-pass operating horns that are held at a constant diameter during honing. At present, all such one-pass operating horns are formed as diamond horns and are not conditioned prior to use. The present invention allows the surface finish condition to be adjusted and allows the horn to be reconditioned in the event of wear over extended periods of time, thus vitrifying the one-pass operating horn to provide a bonded ultra-strength. It can be formed of an abrasive material.
Condition a one-pass operated horn held at a rotational speed and feed rate adjusted to a conditioning diamond wheel, as is the case with a horn mounted on an expandable honing head used for polishing cylinder bores. By doing so, it is possible to adjust the surface finish obtained on the workpiece by using the horn.

Although the greatest advantage is obtained by using vitrified cubic boron nitride, other vitrified bonded ultra high strength abrasive materials including diamond, aluminum oxide and silicon carbide are conditioned by the method of the present invention. It is also beneficial to do so.

The equipment which can be used to carry out the method of the invention is of a conventional type per se and is no different from the equipment currently used. Therefore, it is not considered necessary to describe this device in detail in connection with the present invention.

Claims (5)

[Claims] 1. A drum carrying a horn is rotated, a diamond grinding wheel is rotated, the diamond grinding wheel and the horn are pressed so as to contact each other, and the diamond grinding wheel and the horn are relatively axially moved. In a method of conditioning a vitrified, bonded, ultra-strength abrasive horn adapted to move, the surface speed of the horn is significantly greater than the surface speed of the diamond grinding wheel, and the horn and the diamond grinding wheel are To crush the vitrified binder and super-strong abrasive material by contact with and to control the machining depth and axial movement speed to determine the surface finish of the machined workpiece by horn The method characterized by what you did. 2. A method according to claim 1, characterized in that the particle size of the diamond wheel is made considerably larger than the particle size of the super-strong abrasive material of the horn. . 3. The method according to claim 2, wherein the diamond particles of the diamond grinding wheel are sized in the range of 4 to 5 times the particles of the super-strong abrasive material of the horn. A method characterized by the following. 4. A method according to any one of claims 1 to 3, characterized in that the drum is an expandable honing head. 5. The method according to any one of claims 1 to 3, wherein the horn is a tapered one-pass operating horn.