JPH0425620A - Working method for rolling member rolling face in bearing and the bearing - Google Patents

Abstract

PURPOSE:To improve reproducing performance of working depth and smoothness on a rolling member running face by arranging an electrode in a face-to-face-relation on a bearing basic body having a rough rolling face formed by rough working after forming the bearing basic body, interposing electrolyte between the rough rolling face and the electrode, and applying voltage between them for removing the rough rolling face chemically. CONSTITUTION:A rotating grinding wheel 4 is abutted against the part of a sliding base 1 preliminarily sementation hardened on which a rolling face is formed, and it is ground to form a rough rolling face 11'. After an electrode 5 is arranged with a specified gap to each rough surface 11', electrolyte 6 is flowed in between the face 11' and the electrode 5, and also a pulse D.C voltage 7 is applied to a part between the sliding base 1 and the electrode 5 so that a current is supplied from the side of the sliding base 1 to the side of electrode 5. As a result, the rough rolling face 11' contacting the electrolyte 6 is melted out in the electrolyte 6, and the formation of four lines of load rolling faces 11 is completed on the sliding base 1. Uniform working conditions of voltage application time and the like makes the working depth substantially uniform at every sliding base 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bearing including a rolling element, such as a linear sliding bearing, a swivel bearing, or a ball screw, and a method of machining the rolling element raceway surface thereof. The present invention relates to a machining method that can dramatically improve the machining accuracy of raceway surfaces.

[Prior Art] Mechanisms that guide linear motion or rotational motion between two objects are broadly classified into sliding guides and rolling guides. Of these, the latter type of rolling guide, which utilizes the rolling motion of rolling elements such as balls or rollers, ■can minimize frictional resistance and save power energy compared to sliding guides, ■depends on the intended use. By applying an appropriate preload to the rolling elements, it has the advantage of increasing the rigidity of the bearing and achieving high-precision movement without rattling. Rolling guide bearings (hereinafter referred to as bearings) that support various types of motion, such as splines and ball screws, are widely used in various industries.

As a specific structure, for example, a linear sliding bearing has a raceway having a raceway surface along the axial direction, a load region having a load raceway surface facing opposite to this raceway surface, and both ends of this load region. A sliding base equipped with an endless track consisting of a no-load area that communicates and connects the two, and a load that circulates within the endless track and applies a load between the rolling surface of the way base and the loaded rolling surface of the sliding base. The rolling elements move the sliding table and the wayway relatively by rolling on the rolling surface and the loaded rolling surface (hereinafter collectively referred to as the rolling surface). , it is a mechanism for linearly guiding movable bodies fixed to these track bases or sliding bases.

By the way, although this type of bearing has the above-mentioned advantages, due to its structure, the machining depth of the rolling surface of the rolling element greatly affects the movement accuracy such as rattling of the guided object. It is required to control the machining depth with high precision.

In addition, from the viewpoint of reducing the friction coefficient of the raceway surface, reducing the amount of wear on the raceway surface during the early stage of bearing use, and achieving high-precision motion without vibration, the raceway surface has extremely high smoothness. required to be present.

Conventionally, the processing of raceway surfaces with such requirements involves grinding the hardened raceway surface formation area using a rotary grindstone, and then performing a so-called lapping process as a finishing process, specifically using abrasive grains. A common method is to perform grinding using a rubber grindstone in which particles are dispersed.

[Problems to be Solved by the Invention] However, in the grinding process in which the tool is brought into mechanical contact with the raceway surface, such as the above-mentioned lapping process, it is difficult to control the amount of grinding, and the actual amount of grinding is less than the target grinding 1. This results in an error of approximately several + μm.

Therefore, for products manufactured using conventional processing methods, the actual amount of grinding of the raceway surface, that is, the processing depth, differs depending on the product even if the product has the same specifications.For example, the linear sliding bearing mentioned above In this case, the distance between the raceway surface of the wayway and the load rolling surface of the slide table that face each other differs from one slide table to another, although the distance is very small.

This presents a major problem when applying preload to the rolling elements. In other words, in this type of bearing, the amount of preload is adjusted by selecting the diameter of the rolling elements in micrometers, but even if the same rolling elements are installed in products of the same standard, the preload applied to each bearing will vary. The amount will be different.

For this reason, for example, when a table is guided in a straight line by incorporating multiple slides into a negative track, it is necessary to equalize the amount of preload on each slide. It is necessary to select and adjust the amount of preload, making assembly of the bearing extremely troublesome.

In addition, as mentioned above, the motion accuracy of a bearing is easily affected by the surface roughness of the rolling surface, but if you want to improve the smoothness by grinding, you will have to spend a lot of time using high-precision tools and machines. Processing was required, which inevitably increased costs and reduced mass productivity. Therefore, there is a strong desire for the emergence of a new method for processing raceway surfaces that can improve smoothness, is low cost, and has high mass productivity.

The present invention was made in view of these problems.
The purpose of this is to provide good reproducibility of the machining depth in machining the rolling element raceway of a bearing, and to be able to control the machining depth in units of 1710 μm. An object of the present invention is to provide a processing method for a rolling element rolling surface that can improve the smoothness of the rolling element, and a bearing using this processing method.

"Means for Solving the Problems" As a result of intensive studies to achieve the above object, the inventors of the present application focused on an electrolytic processing method used for surface treatment of metal processed products.

This electrolytic machining method involves arranging electrodes to face the machined surface of a workpiece obtained by electrical discharge machining, and filling the gap between the workpiece and the electrode with an electrolytic solution such as sodium nitrate or sodium chloride. The surface of the workpiece is treated by flowing an electrolytic solution at high speed and applying a DC voltage between the workpiece and the electrode (Japanese Patent Laid-Open No. 61-7192).
No. 1, Japanese Unexamined Patent Application Publication No. 60-44228, etc.), it has characteristics such as improved machined surface roughness and easy removal of a deteriorated layer by processing.

The inventor of the present application has discovered that by applying this surface treatment method to chemically form the raceway surface, it is possible to dramatically improve the reproducibility of the processing depth, and has This led to his invention.

That is, the present invention provides a method for processing a rolling element rolling surface in a bearing that has a rolling element such as a ball or roller between a pair of bases and supports rotational motion or linear motion between an object fixed to the base. After forming a bearing base having a rough rolling surface by rough machining, electrodes are disposed to face the rough rolling surface, and an electrolyte is interposed between the rough rolling surface and the electrodes, and The present invention is characterized in that a DC voltage is applied between the bearing base and the electrodes to chemically remove the rough raceway surface to form a raceway surface.

In such technical means, as long as the bearing to which the above processing method is applicable has a rolling surface on the bearing base on which rolling elements such as balls or rollers roll, the structure etc. can be selected as appropriate. It's okay to do that. For example, it is applicable to linear sliding bearings, ball splines, ball screws, swing bearings, etc.

In addition, as a method for forming a bearing base having a rough rolling surface, cutting, grinding, drawing, etc. can be used as long as the rough rolling surface, which is the preliminary stage of the rolling surface, can be formed with a certain degree of precision.
You may select the method as appropriate.

Further, as long as the electrode is arranged facing the rough rolling surface formed by rough machining with a predetermined gap (for example, 0.3M), its structural shape may be changed as appropriate. There is no problem, for example, the electrodes may be arranged individually to face the plurality of raceway surfaces provided in the bearing, or by devising the shape, the - electrodes may be arranged to face the plurality of raceway surfaces. You can also do it.

Furthermore, when machining a raceway surface on a long track or spline shaft, it is possible to perform the machining by step-driving the electrode in the axial direction of the workpiece.

Furthermore, the DC voltage applied between the bearing base and the electrodes may be changed as appropriate in its time waveform as long as it is applied so that a current flows from the bearing base to the electrodes. However, from the viewpoint of obtaining a rolling surface with good surface roughness, it is preferable to continuously apply a pulsed DC voltage having a predetermined pulse width.

Moreover, as the electrolytic solution, those used in the electrolytic processing method described above, such as sodium nitrate and sodium chloride, can be used.

Further, according to the results obtained through experiments by the inventor of the present application, it has been found that in the processing method of the present invention, there is a proportional relationship between the application time of the DC voltage and the amount of chemical removal of the rough rolling surface.

Therefore, in the present invention, by adjusting the application time of the DC voltage based on the proportional relationship confirmed by experiments, it is possible to control the amount of chemical removal from the rough rolling surface in units of approximately 1710μ. . The experimental results obtained by the inventor of the present application will be described in detail later.

[Work] The above technical means works as follows.

Since the rolling surface is formed by chemically removing the rough rolling surface formed on the bearing base, various factors such as the gap between the bearing base and the electrodes, voltage application time, electrolyte properties and flow rate etc. By unifying the Roe conditions, the removal amount becomes a substantially constant value, and variations in the machining depth of the raceway surface for each product are suppressed.

In addition, the cutting 110 is controlled by the port for adjusting the voltage application time.
The amount of rough rolling surface formed during machining is controlled with high precision.
The machining depth of the raceway surface can be easily controlled.

Furthermore, since the rough rolling surface is eluted into the electrolytic solution and the rolling surface is formed, the smoothness of the rolling surface formed by this processing method is improved.

[Example] Hereinafter, a method for forming a rolling element rolling surface in a bearing of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows 730 steps of machining the load rolling surface 11 on the slide table 1 (bearing base) of a linear sliding bearing. As shown in FIG. 2, the sliding table 1 to be processed here has a horizontal portion 12 and a pair of oil portions 13 hanging down from both ends thereof, and is formed into a substantially U-shaped cross section.
A row of four holes 3 (rolling elements) that roll while applying a load between the load rolling surface 11 formed on the inner surface of the track 2 and the rolling surface 21 formed on the way 2 (bearing base). It moves linearly on the track 2 in its axial direction (in the direction perpendicular to the plane of the paper in FIG. 2).

The processing steps will be explained according to the order of FIGS. 1(A) to (0).

(1) First, as shown in FIG. 1(A), a rough raceway surface 11' is formed by cutting the raceway surface forming portion of the slide table 1, which has been previously carburized and quenched. The cutting process is performed by grinding by bringing the rotary grindstone 4 into contact with the relevant part and moving it in the axial direction of the slide table 1 (in the direction perpendicular to the plane of the paper). In this embodiment, in order to ensure the parallelism of the four load rolling surfaces 11, a so-called one-pass grinding method is used in which each load rolling surface 11 is ground simultaneously.

(2) Next, as shown in FIG. 1(8), electrodes 5 (for example, Cu) are placed facing each of the rough rolling surfaces 11' formed in the previous step with a constant gap maintained therebetween. In this case, the electrodes 5 may be arranged individually against the four rough rolling surfaces 11', but in this embodiment, in order to reduce the effort of positioning, the electrodes 5 may be arranged simultaneously against each of the rough rolling surfaces 11'. The electrode 5 is manufactured in advance and is fitted into the sliding table 1.

Note that the electrode 5 has been subjected to lapping processing in advance so as to have a surface roughness of approximately 0.3 μm Rmax.

■ Next, as shown in FIG. 1(C), an electrolytic solution 6 (for example, 10 to 50% wt.
A pulsed DC voltage 7 is applied between the sliding table 1 and the electrode 5. The mode of voltage application is opposite to so-called electroplating, and the voltage is applied so that a current flows from the workpiece, that is, the sliding table 1 side to the electrode 5 side. As a result, the rough rolling surface 11' in contact with the electrolytic solution 6 is eluted into the electrolytic solution, and the formation of the four-striped load rolling surface 11 on the sliding table 1 is completed (see Fig. 1 (D)). )
. In this example, the above steps (1) and (2) will be collectively referred to as electrolytic polishing.

In this way, in the processing method of this embodiment, the load rolling surface 11 is obtained by chemically removing the rough rolling surface 11', so that the gap between the sliding table 1 and the electrode 5 or the DC voltage By unifying various processing conditions, such as the application time of .

Therefore, the error in machining depth is caused only by the cutting process, but since there is an error in the path distance when the same cutting process is performed using the same processing machine, the load rolling on each slide table is It is possible to reproduce the machining depth of the surface between paths.

Here, we will report on the results of an experiment conducted by the inventor regarding the relationship between the DC voltage application time and the machining depth in this electropolishing process.

In this experiment, electrodes were placed opposite to the workpiece, and an electrolytic solution was flowed between both members, and the machining current (250A>
The machining depth of the workpiece in each case was measured by changing the current application time. Further, the machining depth at each energization time was theoretically calculated from the elution weight of iron, the energization time, and the specific gravity of the workpiece.

FIG. 3 shows a graph of experimental results and theoretically calculated values.

According to the results shown in FIG. 3, it is clear that there is a proportional relationship between the application time of the machining current and the machining depth, and the theoretically calculated values also showed a proportional relationship similar to this.

In addition, by applying a machining current in units of several m5ec,
It was also confirmed that the machining depth could be controlled in units of 1/100 μm.

Therefore, in the machining method of the present invention, by repeatedly applying a pulsed DC voltage with an on-time of several m5ec, it is possible to control the machining depth of the raceway surface with high precision in proportion to the number of applied pulses. It is possible.

Therefore, after cutting with the above-mentioned culm ■, the rough rolling surface 11'
By measuring the machining depth of the load rolling surface 11 and determining the applied pulse width and number of pulses based on the measured values, the machining depth error caused by cutting can be absorbed and the target machining depth of the load rolling surface 11 can be achieved. It is possible to standardize the machining depth with an error of about 1710 μm.

Next, the smoothness of the load rolling surface 11 formed by this processing method will be described.

Figure 4 (^) shows the rough rolling surface 11 created by the cutting process.
Fig. 4 (B) shows an example of a roughness curve obtained by actually measuring the surface roughness of 11', and Fig. 4 (B) shows a rough rolling surface 11' according to the roughness curve of (A) above, which was subjected to electrolytic polishing. It shows the roughness curve of the loaded rolling surface 11. Moreover, FIG. 4(C) is a roughness curve showing a loaded rolling surface which has been finished with a finishing h-edge by conventional lapping.

According to the actual measurement results, the rough raceway surface 11' has a continuous sharp roughness with an extremely short period, whereas the loaded raceway surface 11 which has been subjected to electrolytic polishing has a relatively large period and a sharp roughness. Continuous rounded roughness at the tip.

Furthermore, the surface roughness has also been improved from a maximum of about 3 μm to about 2 μm.

From this, it is understood that in electrolytic polishing, the peaks of the cut surface are easily eluted into the electrolytic solution, thereby forming a smoother processed surface.

In addition, the load raceway surface formed by electrolytic polishing has a rounder roughness and convex shape compared to that formed by lapping, and is more rounded than the raceway surface formed by conventional processing methods. It can be seen that the smoothness has improved.

Therefore, the load raceway surface 11 of the sliding table 1 formed by the processing method of the present invention has reduced frictional resistance compared to that formed by the conventional processing method, and the load raceway surface 11 in the axial direction Fluctuations in the frictional resistance in the slide table 1 become small, and high precision movement of the slide table 1 can be achieved.

Moreover, since the smoothness is high, initial wear of the load rolling surface 17 caused by rolling of the balls 3 can be suppressed, and the motion accuracy of the slide table 1 can be maintained over a long period of time.

Furthermore, in order to confirm the corrosion resistance of the load raceway surface 11 formed by this processing method, the inventors placed the processed slide table in an autoclave and conducted a corrosion acceleration test.

According to the results, it was confirmed that the load raceway surface 11 formed by electrolytic polishing has improved corrosion resistance compared to the load raceway surface 11 formed by the conventional processing method. This is considered to be because the load rolling surface 11 has been chemically surface-treated.

Therefore, the sliding table 1 of this embodiment has excellent environmental resistance and can be expected to have a long service life.

Further, in this processing method, the rough rolling surface 11' is chemically removed to form the loaded rolling surface 11, so that the altered layer in which residual stress is generated by cutting is removed. Therefore, the fatigue limit of the load rolling surface 11 is improved, and in this respect as well, the life of the sliding table 1 can be expected to be extended.

In the embodiments described above, the case where the present invention is applied to machining the load rolling surface 11 of the sliding table 1 has been explained.
It is also possible to apply the present invention to processing the rolling surface 21 of the track base 2.

However, since the track base 2 is required to be manufactured with a length of several meters, unlike the case of the load raceway surface 11 of the sliding base 1, the entire length of the rough raceway surface that has been cut is It is quite difficult to arrange the electrodes 5 facing each other with a constant gap.

Therefore, as shown in FIG. 5, a short electrode 5 is arranged opposite to a part of the rough rolling surface 21', and is driven in steps along the longitudinal direction of the track 2 to process the rolling surface 21. Is it realistic to do this?

FIG. 6 shows a concrete implementation device. This device consists of an electrode 5 inside a box-shaped casing 8 with one side open.
The opening of the casing 8 is brought into contact with the track 2 so that the electrode 5 faces the rough rolling surface 21' to form a sealed liquid chamber 81. Machining is performed by applying a DC voltage between the electrode 5 and the track base 2 while causing the electrolytic solution 6 to flow in and out. Then, this casing 8 is connected to a stepping motor (not shown).
By moving the track in stages along the two axial directions, it is possible to uniformly electrolytically polish the rough rolling surface 21' formed by cutting. In FIG. 6, the reference numeral 82 is a sealing member that seals between the casing 8 and the track 2, and the reference numeral 71 is a brush power feeder that comes into sliding contact with the track 2.

Further, FIG. 7 shows an example in which the above-mentioned apparatus is applied to process a shaft 9 of a ball bushing whose outer circumferential surface 91 serves as a ball rolling surface. However, in the case of such a shaft 9, since it is necessary to uniformly process the outer peripheral surface 91, the process is performed by combining the rotation of the shaft 9 and the movement of the casing 8 in the axial direction.

Furthermore, since the present processing method can be applied to the long shaft 9, the present processing method can also be applied to the spiral ball rolling groove of the ball screw shaft. In this case, the electrode 5 of the above device
As shown in FIG. 8, the screw shaft 10 is provided with a protrusion 51 corresponding to the pitch of the hole rolling groove 92, and the rotation of the screw shaft 10 is made such that the protrusion 51 traces the ball rolling groove 92. And h loe is performed by controlling the movement of the casing 8.

The raceway surface 21 of the track 2 or the outer circumferential surface 91 of the shaft 9 formed by this processing method in this way
As with the load rolling surface 11 of the sliding table 1 described above, it goes without saying that the reproducibility of the machining depth and the smoothness of the surface are improved.

U Effects of the Invention] As explained above, according to the method for processing the rolling element raceway surface in a bearing of the present invention, the rough raceway surface formed on the bearing base is chemically removed to form the raceway surface. This improves the reproducibility of the machining depth of the raceway surface for each product, making it possible to standardize the work of applying preload to the bearing.

In addition, by adjusting the voltage application time, it becomes easy to control the machining depth of the raceway surface, so it is possible to manufacture a bearing with higher precision without chattering.

Furthermore, since the smoothness of the rolling surface is improved, it is possible to manufacture a bearing with high precision in this respect as well, and the precision can be maintained over a long period of time.

[Brief explanation of the drawing]

Figures 1 (A) to (D) are explanatory diagrams showing the outline of the processing method of the present invention, Figure 2 is a sectional view showing a linear sliding bearing to which the processing method of the present invention can be applied, and Figure 3 is an electrolytic A graph showing the relationship between voltage application time and machining depth in polishing, FIG. 4(A) is a roughness curve showing the surface roughness of the rough rolling surface in the present invention, and FIG. 4(B) is a graph showing the relationship between the voltage application time and the machining depth in the present invention. Figure 4 (C) is a roughness curve showing the surface roughness of the raceway surface processed by conventional lapping. An explanatory diagram showing an outline of a method for forming a raceway surface on a long object, Fig. 6 is a schematic diagram showing a device for processing a raceway surface on a raceway of a linear sliding bearing, and Fig. 7 is an explanatory diagram showing a method for forming a raceway surface on a raceway of a linear sliding bearing. FIG. 8 is a schematic diagram showing an apparatus for machining the outer peripheral surface, and FIG. 8 is a schematic diagram showing the arrangement of electrodes when machining a ball screw shaft. [Description of symbols] 1:1 moving base (bearing base) 2: Track base (bearing base) 3: Ball (rolling element) 5: Electrode 6: Electrolyte 7: DC voltage

Claims (5)

[Claims] (1) A method of processing a rolling element rolling surface in a bearing that has rolling elements such as balls or rollers between a pair of bases and supports rotational motion or linear motion between objects to which the bases are fixed. , after forming a bearing base having a rough raceway surface by rough machining, electrodes are arranged to face the rough raceway surface, and an electrolyte is interposed between the rough raceway surface and the electrodes; A method for processing a rolling element raceway, comprising applying a DC voltage between a base and an electrode to chemically remove the rough raceway to form a raceway. (2) The method for machining a rolling element rolling surface according to claim 1, characterized in that a pulsed DC voltage is applied between the bearing base and the electrode. (3) The method for processing a rolling element raceway surface according to claim 1 or 2, characterized in that the amount of chemical removal of the rough raceway surface is controlled by adjusting the voltage application time. (4) The rolling element rolling surface according to any one of claims 1 to 3, characterized in that the rolling surface is formed by relatively moving the rough rolling surface of the bearing base and the electrode arranged opposite thereto. How to process the running surface. (5) In a bearing that supports rotational motion or linear motion between objects to which the base bodies are fixed, a rolling element such as a ball or roller is interposed between rolling surfaces formed on a pair of base bodies, respectively. For the raceway surface, electrodes are placed opposite to the rough raceway surface formed on the bearing base by rough machining, and an electrolyte is interposed between the rough raceway surface and the electrodes. A bearing characterized in that it is formed by chemically removing the rough rolling surface with a DC voltage applied between the bearing.