A processing method for a chrome-plated oil ring

Abstract

The present invention discloses a processing method for a chrome-plated oil ring, comprising the following steps: preparing an oil ring blank, performing profiling turning on the inner and outer circles, making a notch, roughly grinding the opening, forming and turning the outer circle groove of the oil ring, milling an oil hole, chrome-plating, medium grinding the opening, turning the inner circle and the spring groove, threading a spring and honing the outer circle oil belt, performing finish grinding on the opening of the finished product, and double-end surface fine grinding to obtain a finished oil ring. This method reduces the electroplating and processing costs, prevents the problem of burrs appearing at the oil hole, and meets the requirements of mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of the processing of chrome-plated oil rings, and particularly relates to a processing method for chrome-plated oil rings made of cast iron materials. Background Art

[0002] The structural standards of chrome-plated oil rings are ISO6625, ISO6626, and ISO6626-2. Due to their good service performance and low production costs, they are widely used in diesel engines, gasoline engines, and air compressors. For an oil ring with a chromium layer on the entire outer circular groove, the piston ring international standard ISO6626 names it DSF-CNP. The process method of the prior art is as follows: oil ring blank, internal and external circular profiling turning, cutting, flaring inspection, rough grinding of the opening, forming turning and cutting the outer circular groove, chrome plating, medium grinding of the opening, forming grinding of the outer circular groove, punching chrome plating on the outer circular groove, milling oil holes, turning the inner circle and spring groove, threading the spring and honing the outer circular oil band, and finally performing finish grinding of the opening and double-end surface lapping on the finished product to obtain the finished oil ring. The existing process method belongs to a secondary electroplating process. After plating, the outer circular groove is subjected to forming grinding treatment, and then chrome plating layer is punched on the outer circular groove, and then oil holes are milled. Although this process method can meet the requirements of the product, the processing and electroplating costs are relatively high. And because the oil holes are milled after there is a hard chromium layer on the outer groove, as shown at points A and B in Figure 1 it sometimes causes the problem of serrated burrs at the oil holes.

[0003] For such oil rings, the ISO standard requires the tolerance of the oil band width to be ±0.10 mm. It is also found that there are other process methods including a primary electroplating process. However, since they have not found the relationship between the pre-plating dimensions and the growth of the post-plating oil band width, the scatter of the outer circular oil band width is too large, and some exceed the requirements of the ISO standard, thus resulting in a large scatter of the contact pressure between the ring and the cylinder and affecting the service performance of the whole machine. Summary of the Invention

[0004] Object of the Invention: To solve the problems of the prior art, the present invention provides a processing method for chrome-plated oil rings. This method reduces the electroplating and processing costs, prevents the problem of burrs at the oil holes, the scatter of the oil band width of the processed oil rings is stably within ±0.07 mm, and it meets the requirements of mass production.

[0005] Technical Solution: The processing method for chrome-plated oil rings described in the present invention includes the following steps: preparing an oil ring blank, internal and external circular profiling turning, cutting, rough grinding of the opening, forming turning and cutting the outer circular groove of the oil ring, milling oil holes, chrome plating, medium grinding of the opening, turning the inner circle and spring groove, threading the spring and honing the outer circular oil band, and finally performing finish grinding of the opening and double-end surface lapping on the finished product to obtain the finished oil ring.

[0006] As a preferred embodiment of the present invention, the size of the outer circular groove of the formed turning oil ring (or the width of the oil band of the oil ring before chrome plating) is obtained by the following method: The line segment IJ is obtained by the intersection of the line segment FI and the line segment GJ with the outer circular surface of the oil band before chrome plating, where the line segment IJ is the width of the oil band of the oil ring before chrome plating; the distance from point F to point G is the width of the oil band of the finished oil ring; the line segment EF is the outer chamfer line segment of the oil band of the finished oil ring; the line segment HG is the inner chamfer line segment of the oil band of the finished oil ring; the straight line FI is the angle bisector of ∠EFG; the straight line GJ is the angle bisector of ∠FGH, and the projection distance of the straight line FI or the straight line GI in the horizontal direction is the thickness T of the outer circular chrome layer of the oil band of the finished oil ring.

[0007] As a preferred embodiment of the present invention, the inner chamfer and the outer chamfer of the outer circular groove of the formed turning oil ring are controlled by the following method: Taking the average value of the chrome layer thickness at the bottom of the outer circular groove of the oil ring as the reference value, the inner chamfer and the outer chamfer of the outer circular groove are determined.

[0008] As a preferred embodiment of the present invention, the chrome layer thickness at the bottom of the outer circular groove of the oil ring is 0.01 - 0.03 mm. Taking 0.02 mm as the reference value, the inner chamfer and outer chamfer dimensions of the oil band of the oil ring before chrome plating are obtained, that is, points L and K are determined. JL is the inner chamfer line segment of the oil band before chrome plating, and IK is the outer chamfer line segment of the oil band before chrome plating.

[0009] As a preferred embodiment of the present invention, the two transition arcs Rc of the outer circular edge of the oil band before chrome plating are controlled by the outer circular width of the oil band before chrome plating.

[0010] As a preferred embodiment of the present invention, the two transition arcs Rc of the outer circular edge of the oil band before chrome plating are controlled by the following method: When the outer circular width of the oil band before chrome plating ≤ 0.25 mm, Rc is 0.15 mm; when the outer circular width of the oil band before chrome plating > 0.25 mm, Rc is 0.25 mm.

[0011] As a preferred embodiment of the present invention, the depth at which the milling cutter blade penetrates the outer circular surface of the oil ring is less than the radial thickness during the oil hole milling process of the oil ring.

[0012] As a preferred embodiment of the present invention, the depth N at which the milling cutter blade penetrates the outer circular surface of the oil ring is:

[0013]

[0014] Wherein, d is the diameter of the oil ring during the oil hole milling process; d5 is the diameter of the milling cutter; M is the center distance between the center of the milling cutter blade and the center of the oil ring.

[0015]

[0016] Among them, d is the diameter of the oil ring during the milling of the oil hole; d5 is the diameter of the milling cutter; W1 is the chord length of the outer side of the oil hole; a4' is the depth of the outer circular groove before plating;

[0017] a4' = a4 - T + 0.02 (mm);

[0018] Among them, a4 is the depth of the outer circular groove of the finished oil ring, and T is the target chromium layer thickness of the oil belt outer circle of the finished oil ring.

[0019] As a preferred embodiment of the present invention, a machining allowance is reserved for the outer diameter of the oil ring.

[0020] As a preferred embodiment of the present invention, the radial thickness of the oil ring before chrome plating is a1':

[0021] a1' = N + t, where N is the depth at which the milling blade passes through the outer circular surface of the oil ring, and t is the distance between the bottom of the oil hole and the inner circular surface during the milling of the oil hole before chrome plating.

[0022] In a specific embodiment, t is 0.40 mm.

[0023] Beneficial effects: (1) The present invention adopts a one-time plating process, eliminating the outer circular groove punching chrome plating process. The outer circular groove size and profile are turned in place at one time before plating, without the need for post-plating outer circular groove forming grinding. Compared with the conventional process method, it reduces two processes of outer circular groove forming grinding and outer circular groove punching chrome plating, shortens the process flow, saves costs, and reduces costs by 10 - 15%; (2) The present invention finds out the relationship between the pre-plating size and the growth of the oil belt width after plating. The width consistency of the finished oil belt is better, and the scatter of the oil belt width is stable within ±0.07 mm; (3) The milling of the oil hole in the present invention is carried out before plating. At this time, the oil hole is milled on the matrix material of the oil ring. Since the matrix material is relatively soft, the two sides of the oil hole are not prone to hairiness during the milling of the oil hole, so the appearance quality of the oil hole is better, and the appearance yield is increased by 2 - 6% compared with the original. Brief Description of the Drawings

[0024] Figure 1 It is a cross-sectional view of a finished chrome-plated oil ring in the prior art. In the figure, points A and B are the chromium peeling burrs at the oil hole;

[0025] Figure 2 It is a processing flow chart of the chrome-plated oil ring of the present invention;

[0026] Figure 3 It is a cross-sectional view of the finished chrome-plated oil ring obtained by processing the present invention;

[0027] Figure 4 It is a front view of the finished chrome-plated oil ring obtained by processing the present invention;

[0028] Figure 5 It is the cross-sectional dimension of the oil ring before chrome plating of the present invention;

[0029] Figure 6 are the specifications of the finished chrome-plated oil ring after processing according to the present invention;

[0030] Figure 7 is a partial enlarged view of the oil band of the chrome-plated oil ring obtained by processing according to the present invention;

[0031] Figure 8 are the product dimensions when milling the oil hole of the oil ring according to the present invention;

[0032] Figure 9 are the product dimensions when milling the oil hole of the oil ring according to the present invention. Detailed implementation manners

[0033] Example 1: As Figure 2 shown, in this example, the chrome-plated oil ring is processed according to the following steps: (S1) Process the oil ring blank; (S2) Profile turning of the inner and outer circles; (S3) Notch; (S4) Rough grinding of the opening; (S5) Form turning and cutting of the outer circle groove; (S6) Milling the oil hole; (S7) Chrome plating; (S8) Medium grinding of the opening; (S9) Turning the inner circle and the spring groove; (S10) Through-spring honing of the outer circle oil band; (S11) Finish grinding of the opening of the finished product; (S12) Double-end surface lapping to obtain the finished oil ring.

[0034] For the process of form turning and cutting the outer circle groove of the present invention, it is necessary to control the profile and dimensions of the outer circle groove of the oil ring before chrome plating. The specific control parameters are as follows:

[0035] As Figures 3 to 7 shown, in the figure, d1 is the diameter of the finished chrome-plated oil ring, that is, the cylinder diameter of the whole machine; h1 is the ring height of the finished oil ring; h' is the ring height of the oil ring before chrome plating; a1 is the radial thickness of the finished oil ring; a1' is the radial thickness of the oil ring before chrome plating; B3 is the oil band spacing of the finished oil ring; B3' is the oil band spacing of the oil ring before chrome plating; a4 is the depth of the outer circle groove of the finished oil ring; a4' is the depth of the outer circle groove of the oil ring before chrome plating; t is the distance between the bottom of the oil hole and the inner circle surface in the process of milling the oil hole before chrome plating; R is the radius of the spring groove; c1 is the width of the oil hole; α is the inner chamfer of the oil band of the finished oil ring; α' is the inner chamfer of the oil band of the oil ring before chrome plating; β is the outer chamfer of the oil band of the finished oil ring; β' is the outer chamfer of the oil band of the oil ring before chrome plating; h5 is the width of the oil band of the finished oil ring; h5' is the outer circle width of the oil band before chrome plating; Rc is the transition arc of the outer circle edge of the oil band of the oil ring before chrome plating; T is the target chrome layer thickness of the outer circle of the oil band of the finished oil ring.

[0036] Control of the oil band width of the oil ring before chrome plating: The oil band width h5 of the finished oil ring, the inner chamfer α of the oil band of the finished oil ring, the outer chamfer β of the oil band of the finished oil ring, and the target chrome layer thickness T of the outer circle of the oil band of the finished oil ring are used as input values. The straight line FI is the angle bisector of ∠EFG, and the straight line GJ is the angle bisector of ∠FGH. Thus, the oil band line segment IJ of the oil ring before chrome plating is obtained, that is, the I point and the J point in the figure are determined, that is, the outer circle width h5' of the oil band before chrome plating.

[0037] Control of the outer chamfer β' and inner chamfer α' of the oil band of the oil ring before chrome plating: Affected by the "tip effect" of electroplating, during electroplating, the chrome layer is mainly deposited on the outer circle of the oil band, and the chrome layer becomes thinner as it goes down. Affected by the size of the outer circle groove depth a4' of the oil ring before chrome plating, the thickness of the chrome layer on the oil band, and the size of the outer circle width h5' of the oil band before chrome plating, the chrome layer thickness at the bottom of the outer circle groove is concentrated in the range of 0.01 - 0.03 mm. Taking the average chrome layer thickness of 0.02 mm as the reference value, the inner chamfer and outer chamfer dimensions of the oil band before plating are obtained, that is, the L point and the K point are determined. JL is the inner chamfer line segment of the oil band before plating, and IK is the outer chamfer line segment of the oil band before plating.

[0038] Control of the transition arc Rc of the outer circle edge of the oil band of the oil ring before chrome plating: Transition arcs are respectively set at the K point and the L point before plating, with a value of R0.1 mm. At the same time, transition arcs Rc are respectively set at the I point and the J point of the oil band before plating. The value of Rc is: when h5' ≤ 0.25 mm, Rc = 0.15 mm; when h5' > 0.25 mm, Rc = 0.25 mm. The reasonably valued transition arc Rc can effectively avoid the excessive growth of the chrome layer to both sides of the oil band, which is beneficial to the control of the oil band width.

[0039] In step (S5), before chrome plating, the outer circle groove is machined in place at one time by form turning. This form turning requires a form turning tool, and the form turning tool has parameters that are exactly the same as the outer circle profile and dimensions of the oil ring before chrome plating. As described above, preferably, the form turning tool is machined by optical curve grinding.

[0040] In this embodiment, before form turning, the outer diameter of the oil ring is d1 + 0.36 mm, that is, the outer diameter value after rough grinding and opening in the previous process. After this process is completed, the outer diameter of the oil ring is d1 + 0.05 mm, and the machining allowance of the outer circle is 0.15 mm.

[0041] The specific parameter control of the oil hole milling process is as follows: The parameter control of milling the oil hole before chrome plating needs to ensure that the entire radial thickness of the oil ring cannot be milled through during oil hole milling. Then, the required radial thickness is calculated accordingly. At the same time, the inner and outer circle profiling turning processes need to meet this radial thickness requirement. In addition, the blank and the ring die of the oil ring need to be designed around ensuring this radial thickness.

[0042] ① When milling the oil hole before chrome plating, the parameters determined according to the product design are: the outer chord length W1 of the oil hole; the diameter d5 of the milling cutter; the number of oil holes; the included angle θ between the centerlines of two adjacent oil holes on the opening side; the depth a4 of the outer circle groove of the finished product; the target chrome plating thickness T of the outer circle of the finished oil band. Other known parameters are: the diameter d of the ring during the oil hole milling process is d = d1 + 0.05 mm; the depth a4' of the outer circle groove before chrome plating is a4' = a4 - T + 0.02 mm;

[0043] ② To meet the outer chord length W1 of the oil hole, the center distance M between the center of the milling cutter blade and the center of the oil ring is calculated as:

[0044]

[0045] Then, the depth N of the milling cutter blade passing through the outer circle surface of the oil ring is:

[0046]

[0047] That is to say, when N = a1', the milling cutter blade just touches the inner circle surface of the ring, and at this time t = 0. Considering the machining error, in order to ensure that the milling cutter blade does not mill through the entire radial thickness, a safety margin of 0.40 mm is given to it, that is, t = 0.40 mm. Therefore, a1' = N + t = N + 0.40 mm.

[0048] Except for the above, the remaining processes can be implemented according to the common methods in the piston ring industry.

Claims

1. A processing method of a chrome-plated oil ring, characterized in that, It includes the following steps: Prepare the blank of the oil ring, perform profiling turning on the inner and outer circles, make a cut, rough grind the opening, profile turn and cut the outer circle groove of the oil ring, mill the oil hole, chrome plate, medium grind the opening, turn the inner circle and spring groove, insert the spring and hone the outer circle oil band, finish grind the opening of the finished product, and perform double-end surface finish grinding to obtain the finished oil ring; The dimensions of the outer circle groove of the profile-turned and cut oil ring are obtained by the following method: The line segment IJ is obtained by the intersection of the line segment FI and the line segment GJ with the outer circle surface of the oil band before chrome plating. Among them, the line segment IJ is the oil band width of the oil ring before chrome plating; the distance from point F to point G is the oil band width of the finished oil ring; the line segment EF is the outer chamfer line segment of the oil band of the finished oil ring; the line segment HG is the inner chamfer line segment of the oil band of the finished oil ring; the straight line FI is the angle bisector of ∠EFG; the straight line GJ is the angle bisector of ∠FGH, and the projection distance of the straight line FI or the straight line GI in the horizontal direction is the outer circle chromium layer thickness T of the oil band of the finished oil ring; The inner chamfer and outer chamfer of the outer circle groove of the profile-turned and cut oil ring are controlled by the following method: Taking the average value of the chromium layer thickness at the bottom of the outer circle groove of the oil ring as the reference value, determine the inner chamfer and outer chamfer of the outer circle groove, that is, determine points L and K. JL is the inner chamfer line segment of the oil band before chrome plating, and IK is the outer chamfer line segment of the oil band before chrome plating; The two transition arcs Rc at the outer circle edge of the oil band before chrome plating are controlled by the outer circle width of the oil band before chrome plating.

2. The processing method of the chrome-plated oil ring according to claim 1, characterized in that, The chromium layer thickness at the bottom of the outer circle groove of the oil ring is 0.01 - 0.03 mm, and 0.02 mm is taken as the reference value.

3. The processing method of the chrome-plated oil ring according to claim 1, characterized in that, The two transition arcs Rc at the outer circle edge of each oil band before chrome plating are controlled by the following method: When the outer circle width of the oil band before chrome plating ≤ 0.25 mm, Rc is 0.15 mm; when the outer circle width of the oil band before chrome plating > 0.25 mm, Rc is 0.25 mm.

4. The processing method of the chrome-plated oil ring according to claim 3, characterized in that, The depth at which the milling cutter blade penetrates the outer circle surface of the oil ring is less than the radial thickness during the oil hole milling process of the oil ring.

5. The processing method of the chrome-plated oil ring according to claim 4, characterized in that, The depth N at which the milling cutter blade penetrates the outer circle surface of the oil ring: Among them, d is the diameter of the oil ring during the oil hole milling process; d5 is the diameter of the milling cutter; M is the center distance between the center of the milling cutter blade and the center of the oil ring; Among them, d is the diameter of the oil ring during the oil hole milling process; d5 is the diameter of the milling cutter; W1 is the outer chord length of the oil hole; a4' is the depth of the outer circle groove before plating; a4' = a4 - T + 0.02; Among them, a4 is the depth of the outer circle groove of the finished oil ring, and T is the target chromium layer thickness of the outer circle of the oil band of the finished oil ring.

6. The processing method of the chrome-plated oil ring according to claim 5, characterized in that, A machining allowance is left for the outer circle diameter of the oil ring.

7. The processing method of the chrome-plated oil ring according to claim 6, characterized in that, The radial thickness of the oil ring before chrome plating is a1': a1' = N + t, where N is the depth at which the milling cutter blade penetrates the outer circle surface of the oil ring, and t is the distance between the bottom of the oil hole and the inner circle surface during the oil hole milling process before chrome plating.

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