Setting method for machining conditions of cylinder block and bore surface
Patent Information
- Application Number
- JP2021125710
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-07-30
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2041-07-30
AI Technical Summary
Existing bore surfaces in cylinder blocks face challenges in achieving both low fuel consumption and low blow-by gas due to increased oil retention and machining marks that act as oil reservoirs, leading to higher combustion chamber oil burning and blow-by gas entry.
The bore surface is honed to meet specific conditions: Rk+Rpk ≤ 0.5 μm, oil sump amount Vo ≥ 0.005 mm³/cm², and surface layer oil pool amount D ≤ 0.25 μm, with controlled honing processes to achieve a flat surface and minimal machining marks.
This approach reduces friction and fuel consumption while minimizing oil burning and blow-by gas, resulting in improved engine efficiency and performance.
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for setting machining conditions for a cylinder block and a bore surface. [Background technology]
[0002] During operation of a typical internal combustion engine, sliding resistance occurs in various parts. Of these, the sliding resistance between the bore surface of the cylinder block and the outer surface of the piston is the greatest, so reducing friction in this area is the most effective way to improve engine fuel efficiency.
[0003] For example, Patent Document 1 below indicates that the ten-point average roughness (Rz) of the outer surface of the piston ring that slides against the bore surface should be 0.7 μm or less, and the initial wear roughness (Rpk) should be 0.07 to 0.14 μm. This is said to improve the surface roughness of the mating material in a short time during initial break-in, resulting in a significant reduction in friction loss.
[0004] Furthermore, Patent Document 2, described below, shows that when forming numerous fine depressions on the bore surface of a cylinder block by laser processing, the depressions are shaped so that they are more open towards the opening than towards the back. This is said to reduce the shear resistance of the oil film containing oil held in the depressions, thereby reducing the coefficient of friction between the depressions and the mating member. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] Japanese Patent Publication No. 2007-232026 [Patent Document 2] Japanese Patent Publication No. 2004-230402 [Overview of the Initiative] [Problems that the invention aims to solve]
[0006] It is common practice to grind or polish the bore surface, such as through honing. In this case, countless linear machining marks remain on the bore surface, and these marks function as oil reservoirs. Therefore, increasing the number of machining marks formed on the bore surface increases the amount of oil held on the bore surface, reducing friction between the two and improving fuel efficiency. However, an increase in the amount of oil held on the bore surface increases the amount of oil burned in the combustion chamber, worsening the LOC (Liquid Oxide). Furthermore, if deep groove machining marks connecting the crankcase to the combustion chamber are formed on the bore surface, combustion gases from the combustion chamber can more easily enter the crankcase through the machining marks, potentially increasing the amount of blow-by gas.
[0007] Therefore, the present invention aims to provide a bore surface characteristic that achieves both low fuel consumption and low LOC / low blow-by gas. [Means for solving the problem]
[0008] The inventors have found that if the bore surface satisfies all of the following conditions, it is possible to achieve both low fuel consumption and low LOC / low blow-by gas. (1) The value of Rk + Rpk is less than or equal to a predetermined value. (2) The oil reservoir volume Vo is above a predetermined value. (3) The surface oil accumulation amount D is below a predetermined value.
[0009] The oil reservoir volume Vo is expressed by the following formula and represents the amount of oil per unit area held in the valleys of the bore surface. Vo = (100 - Mr²) × Rvk / 2000 [mm 3 / cm 2 ]
[0010] The surface oil reservoir amount D is expressed by the following formula and indicates the amount of oil held near the surface of the bore. D=Rk×(1-(Mr1+Mr2) / 200)+Rvk×(1 / 2-Mr2 / 200) [μm]
[0011] Rk, Rpk, Rvk, Mr1, and Mr2 are the level difference Rk of the core, the height Rpk of the protruding peak, the depth Rvk of the protruding valley, and the load length ratios Mr1 and Mr2 of the core, as defined in JIS B0671-2-2002 (ISO13565-2-1996). Specifically, in the load curve (right figure) of the roughness curve (left figure) shown in Figure 6, a straight line (secant line) is drawn connecting two points 40% apart in the horizontal direction, and the secant line with the gentlest slope is defined as the equivalent line L. From the points where this equivalent line L intersects the vertical axis at the positions Mr=0% and Mr=100%, horizontal lines H1 and H2 parallel to the horizontal axis are drawn. The vertical distance between these two horizontal lines H1 and H2 is the "level difference Rk of the core". Furthermore, within the load curve, the vertical dimension of the region above the upper horizontal line H1 is the "protruding peak height Rpk," and the vertical dimension of the region below the lower horizontal line H2 is the "protruding valley depth Rvk." Also, the horizontal axis coordinates of the intersection points of each horizontal curve H1, H2 and the load curve are the "core load length ratios Mr1, Mr2."
[0012] As shown in condition (1) above, when the value of Rk + Rpk of the bore surface is less than or equal to a predetermined value, it indicates that the proportion of peaks and intermediate parts in the roughness curve of the bore surface is small, that is, there are few peaks on the bore surface that come into contact with the piston ring and cause friction.
[0013] As shown in condition (2) above, when the oil reservoir Vo on the bore surface is above a predetermined value, it indicates that a large total amount of oil is held on the bore surface. As a result, sufficient oil is supplied to the sliding part between the bore surface and the cylinder, thus improving fuel efficiency.
[0014] As shown in the above condition (3), the surface oil accumulation amount D on the bore surface being below a predetermined value indicates that there is little oil retained near the surface of the bore surface. Thus, although the total amount of oil retained on the bore surface according to the present invention is large (condition (2)), the oil retained on the surface layer of the bore surface is small (condition (3)). That is, while ensuring the total amount of oil by retaining oil in the valleys of the bore surface, the oil retained near the surface of the bore surface is reduced. Thus, by having little oil retained near the surface of the bore surface, the amount of oil burned in the combustion chamber is reduced, and LOC is improved.
[0015] Moreover, the peak height of the bore surface being low and the amount of oil retained near the surface of the bore surface being small indicates that there are many flat surfaces on the surface of the bore surface, that is, the number of machining marks (valleys) on the bore surface is small. Thus, by having a small number of machining marks on the bore surface, it becomes difficult for the combustion gas in the combustion chamber to penetrate into the crank chamber through the machining marks, and the blow-by gas amount is reduced.
[0016] Specifically, for example, the value of Rk + Rpk of the bore surface is 0.5 μm or less, and the oil accumulation amount Vo of the bore surface is 0.005 mm 3 / cm 2 or more, and the surface layer oil accumulation amount D of the bore surface is set to 0.25 μm or less.
[0017] The cross-hatch angle of the machining marks is preferably set within a predetermined range. Specifically, it is preferably 20° or more and 45° or less.
[0018] The method for setting the machining conditions for obtaining the bore surface as described above includes a step of performing honing on the bore surface of the cylinder block, a step of measuring the values of Rk + Rpk, oil accumulation amount Vo, and surface layer oil accumulation amount D of the bore surface after honing, and a step of adjusting the honing conditions based on the values of Rk + Rpk, oil accumulation amount Vo, and surface layer oil accumulation amount D of the bore surface.
Advantages of the Invention
[0019] According to the cylinder block having the bore surface properties as described above, it is possible to achieve both low fuel consumption and low LOC / low blow-by gas.
Brief Description of the Drawings
[0020] [Figure 1] It is a cross-sectional view showing a state where honing is performed on the bore surface of the cylinder block. [Figure 2] (a) is a cross-sectional view of the bore surface after boring, (b) is a cross-sectional view of the bore surface after rough honing, (c) is a cross-sectional view of the bore surface after finish honing, and (d) is a cross-sectional view of the bore surface after super finish honing. [Figure 3] It is a cross-sectional view of the cylinder block. [Figure 4] The upper figure is a photograph of the bore surface of the comparative product taken from the inner peripheral side, and the lower figure is the surface roughness waveform of the same bore surface. [Figure 5] The upper figure is a photograph of the bore surface of the implemented product taken from the inner peripheral side, and the lower figure is the surface roughness waveform of the same bore surface. [Figure 6] The left figure is the roughness curve of the measurement target surface, and the right figure is the load curve of the same roughness curve.
Modes for Carrying Out the Invention
[0021] Hereinafter, embodiments of the present invention will be described based on the drawings. <Honing is performed in several steps. In this embodiment, rough honing, finish honing, and super-finishing honing are performed in order.
[0024] As shown in Figure 2(a), rough machining marks 2a (for example, about 20 μm deep) are formed on the bore surface 2 before honing due to cutting processes such as boring. By performing rough honing on this bore surface 2, the machining marks 2a are removed, and fine machining marks 2b (for example, about 5 μm deep) are formed by the grinding wheel, as shown in Figure 2(b).
[0025] Next, the bore surface 2 is subjected to finish honing. In the finish honing process, a grinding wheel 12 with finer abrasive grains than the grinding wheel used in the rough honing process is used. This removes the machining marks 2b from the rough honing process, and the dimensions of the bore surface 2 are adjusted. As shown in Figure 2(c), after the finish honing process, machining marks 2c (for example, about 2 μm deep) are formed on the bore surface 2, which are finer than the machining marks 2b from the rough honing process and have deep grooves 2d.
[0026] Subsequently, the bore surface is subjected to super-finishing honing. In super-finishing honing, a grinding wheel 12 with finer abrasive grains than the grinding wheel used for finishing honing is used. As a result, as shown in Figure 2(d), the peaks of the machining marks 2c from finishing honing are removed, forming a nearly flat surface 2e. After super-finishing honing, the bore surface 2 retains the deep valleys 2d formed by finishing honing.
[0027] The bore surface 2, which has undergone the honing process described above, satisfies all of the following conditions (1) to (3). (1) Rk + Rpk is 0.5 μm or less (preferably 0.25 μm or less) (2) Oil accumulation volume Vo is 0.005 mm 3 / cm 2 (preferably 0.007 mm) 3 / cm 2 (End) (3) Surface oil accumulation amount D is 0.25 μm or less (preferably 0.2 μm or less)
[0028] As shown in Figure 2(d), the bore surface 2 that satisfies the above conditions (1) to (3) has a substantially flat surface 2e with extremely minute irregularities due to superfinishing, and a deep valley 2d that is much deeper than the valleys of the substantially flat surface 2e.
[0029] As a result of condition (2) above, a sufficient amount of oil is retained on the bore surface 2, so sufficient oil can be supplied to the sliding part between the bore surface 2 and the piston, thereby improving fuel efficiency. Also, as a result of condition (3) above, less oil is retained near the surface (ridges) of the bore surface 2, so the amount of oil burned in the combustion chamber is reduced, improving LOC. Furthermore, as a result of conditions (1) and (3) above, the number of deep grooves 2d formed on the bore surface 2 is small, so the amount of combustion gas entering the crankcase from the combustion chamber through the machining marks (deep grooves 2d) is reduced, and the amount of blow-by gas is reduced. In summary, by having the bore surface 2 satisfy the above conditions (1) to (3), it is possible to achieve both low fuel consumption and low LOC / low blow-by gas volume.
[0030] The honing process is adjusted to form the bore surface 2 as described above. Specifically, in order to form the bore surface 2 with the surface texture shown in Figure 2(d), it is important to deeply excavate a small number of deep grooves 2d during the finish honing process {see Figure 2(c)}. For this purpose, the type of grinding wheel used for the finish honing process (size and density of abrasive grains, type of binder, etc.) and the control conditions of the honing head 10 (rotation speed, processing time, etc.) are adjusted. In this embodiment, after performing the above honing process on the bore surface 2 of a sample of the cylinder head 1 under predetermined conditions, the values of Rk+Rpk, oil reservoir amount Vo, and surface oil reservoir amount D of the bore surface 2 are measured. Then, the honing process is adjusted so that these values satisfy the above conditions (1) to (3). By repeating the above steps, the honing process conditions for forming the bore surface 2 that satisfy the above conditions (1) to (3) are set.
[0031] As shown in Figure 3, cross-hatch patterned machining marks are formed on the honed bore surface 2, and in the illustrated example, the deep valleys 2d appear as lines. The cross-hatch angle θ of the machining marks on the bore surface 2 is preferably within a predetermined range, specifically set to 20° or more and 45° or less. In this embodiment, the cross-hatch angle θ of the machining marks is set to 30°.
[0032] The present invention is not limited to the embodiments described above. For example, the super-finishing honing step may be omitted from the honing process. In this case, the bore surface 2 at the time of engine completion has the surface properties shown in Figure 2(c), but during break-in, the bore surface 2 and the piston slide against each other, causing the peaks of the bore surface 2 to be removed, forming a bore surface 2 similar to that shown in Figure 2(d). In this case, the number of processes is reduced, leading to improved productivity and reduced manufacturing costs. On the other hand, if super-finishing honing is performed as described above, a bore surface 2 that satisfies the above conditions (1) to (3) is already formed at the time of engine completion, thus providing low fuel consumption, low LOC, and low blow-by gas characteristics from the beginning of operation. In either case, the bore surface 2 after a break-in period of a predetermined time or more (e.g., 100 hours or more) satisfies the above conditions (1) to (3).
[0033] Alternatively, after the super-finishing honing, further honing may be performed with a finer grinding wheel (for example, deburring honing). [Examples]
[0034] To confirm the effects of the present invention, the following tests were conducted.
[0035] First, two types of cylinder blocks with different bore surface characteristics (comparative and actual) were formed. The bore surfaces of the comparative and actual products were subjected to rough honing, finish honing, and super-finishing honing, as in the embodiment described above, with different processing conditions for the finish honing (especially the type of grinding wheel). Engines were assembled using the comparative and actual products, and each was broken in on a motoring bench. The break-in period was performed at a constant rotational speed of 2000 rpm for more than 100 hours. Engine oil with a viscosity of 0W-16 was used.
[0036] After break-in, photographs and surface roughness waveforms were obtained at three locations (a total of nine locations) spaced circumferentially in the upper, middle, and lower parts of the bore surface of both the comparison product and the prototype, in the sliding region with the piston. Figure 4 shows the photograph and surface roughness waveform at one location on the bore surface of the comparison product, and Figure 5 shows the photograph and surface roughness waveform at one location on the bore surface of the prototype. Then, for both the comparison product and the prototype, the values of Rpk, Rk, Rvk, Mr1, and Mr2 were calculated from the surface roughness waveforms of each part, and the values of each parameter shown in Table 1 below were calculated based on the average values of these values.
[0037] [Table 1]
[0038] Also, using an engine having a comparative product and an implemented product after running-in operation, the friction torque (i.e., mechanical loss), LOC, and blow-by gas amount during operation were measured. Specifically, a torque meter was sandwiched and attached between the crankshaft of the engine and the motor, and the value of the torque meter when the crankshaft of the engine was rotated by the motor was taken as the friction torque. As a result, the friction torque during operation of the implemented product was about 10 to 20% smaller than that of the comparative product. Therefore, it was confirmed that the implemented product has less mechanical loss than the comparative product, that is, the friction between the bore surface and the piston is small, and fuel consumption reduction can be expected. Also, the comparative product exhibits excellent LOC and blow-by gas amount, and the implemented product also obtained LOC and blow-by gas amount equivalent to this. From the above, the value of Rk + Rpk of the bore surface is 0.5 μm or less, and the oil reservoir amount Vo is 0.005 mm 3 / cm 2 or more, and it was confirmed that an implemented product with a surface layer oil reservoir amount D of 0.25 μm or less of the bore surface can reduce fuel consumption and maintain low LOC / low blow-by gas amount compared to a comparative product that does not satisfy these conditions.
[0039] That is, by setting the value of Rk + Rpk of the bore surface to be below a certain value, further setting the oil reservoir amount Vo of the bore surface to be above a certain value, and setting the surface layer oil reservoir amount D of the bore surface to be below a certain value, which are considered to be conflicting setting conditions, it was found that it is possible to contribute to both fuel consumption reduction and maintenance of low LOC / low blow-by gas amount.
Explanation of Signs
[0040] 1 Cylinder block 2 Bore surface 2a Machining mark 2b Machining mark 2c Machining mark 2d Deep valley part 2e Flat surface 10 Honing head 11 Head body 12 Grinding stone θ Cross-hatch angle
Claims
1. The value of Rk+Rpk on the bore surface is equal to or less than a predetermined value, The amount of oil pooled on the bore surface is equal to or greater than a predetermined value, A cylinder block in which the amount D of oil pooled on the surface of the bore surface is equal to or less than a predetermined value.
2. The value of Rk+Rpk on the bore surface is 0.5 μm or less, The amount of oil pooled on the bore surface is 0.005 mm ３ / cm ２ That's all, 2. The cylinder block according to claim 1, wherein the amount D of oil pool on the surface of the bore surface is 0.25 μm or less.
3. 3. The cylinder block according to claim 1, wherein the crosshatch angle of the machining marks formed on the bore surface is 20 degrees or more and 45 degrees or less.
4. a step of honing the bore surface of the cylinder block; a step of measuring values of Rk+Rpk, an oil accumulation amount Vo, and a surface oil accumulation amount D of the bore surface after honing; and adjusting the honing conditions based on the values of Rk+Rpk, the oil accumulation amount Vo, and the surface oil accumulation amount D of the bore surface.