JP2012012957A - Cylinder block made of aluminum alloy, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder block made of an aluminum alloy which is inexpensively manufacturable while securing a necessary characteristic for a cylinder bore surface, and a method of manufacturing the same.SOLUTION: A surface of a cylinder bore is formed so that, when it is assumed that effective load roughness, initial wear height and oil sump depth are Rk, Rpk and Rvk, respectively, Rk+Rpk<1.0 μm, Rk+Rvk<2.0 μm and Rk>0.65 μm are satisfied, and the width of a pit blank region spirally formed on the surface of the cylinder bore and having the height difference of irregularity <2 μm is set ≤1.0 mm.

Description

  The present invention relates to a cylinder block made of an aluminum alloy and a method for manufacturing the same.

  In recent years, replacement of cast block material with cast aluminum has been promoted for the purpose of reducing engine weight. In general, such a cylinder block made of an aluminum alloy is formed by integrating a cast iron cylinder liner into a block base made of aluminum alloy by casting or press-fitting. In such cylinder blocks, cast iron cylinder liners ensure the necessary wear resistance, scuff resistance, sliding characteristics, etc., on the cylinder bore surface.

  On the other hand, linerless aluminum cylinder blocks have been developed in which cast iron cylinder liners have been abolished for the purpose of further reducing the weight of such aluminum alloy cylinder blocks. These linerless aluminum cylinder blocks generally use an aluminum alloy with a high silicon content (high silincon aluminum) to ensure wear resistance, scuff resistance, sliding characteristics, etc. on the cylinder bore surface. It has become.

  Conventionally, in Patent Document 1, an aluminum alloy crystallized from primary silicon having an average particle size of 3 μm to 10 μm is used, and the surface of the cylinder bore is made surface roughness Ra = 0.05 to 0 by performing honing. A cylinder block made of high silicon aluminum with a thickness of 3 μm has been proposed. According to such a cylinder block, primary silicon is projected onto the cylinder bore surface, and seizure resistance and wear resistance are ensured.

Japanese Patent Laid-Open No. 2002-221077

  In such a conventional cylinder block, although seizure resistance and wear resistance of the cylinder bore surface can be ensured, the cost is high because a high-cost silicon alloy alloy is used.

  The present invention has been made in view of such circumstances, and the problem to be solved is a cylinder block made of an aluminum alloy that can be manufactured at low cost while ensuring necessary characteristics on the surface of the cylinder bore, and its It is to provide a manufacturing method.

  In order to solve the above-mentioned problems, the invention according to claim 1 is the cylinder block made of aluminum alloy, in which the effective load roughness is “Rk”, the initial wear height is “Rpk”, and the oil sump depth is “Rvk”. , The surface of the cylinder bore is formed so that “Rk + Rpk <1.0 μm” and “Rk + Rvk <2.0 μm”.

  In this way, the cylinder block made of aluminum alloy with the cylinder bore surface has the same sliding characteristics and oil retention ability as the cast iron cylinder liner, without using an aluminum alloy with a high Si content. This can be done. Therefore, according to the above configuration, it is possible to manufacture the cylinder bore surface at low cost while ensuring necessary characteristics on the cylinder bore surface.

  Further, according to claim 2, the effective load roughness Rk is larger than 0.65 μm, and the width of the pit blank region formed in a spiral shape on the surface of the cylinder bore and having a height difference of less than 2 μm is 1.0 mm. If it is set as follows, it becomes possible to ensure scuff resistance higher than that of a cast iron cylinder liner on the surface of the cylinder bore.

The surface of the cylinder bore as described above can be formed by performing honing after roughening the surface by plasma irradiation.
Incidentally, as a material of such an aluminum alloy cylinder block, ADC 12 can be used as in claim 4.

  Moreover, in order to solve the said subject, invention of Claim 5 as a manufacturing method of the cylinder block made from an aluminum alloy is the process which plasma-irradiates the surface of a cylinder bore, The said cylinder roughened by the plasma irradiation Through the honing process on the bore surface, the effective bore roughness is "Rk", the initial wear height is "Rpk", and the oil sump depth is "Rvk". Rk + Rpk <1.0 μm ”and“ Rk + Rvk <2.0 μm ”.

  In this way, the cylinder block made of aluminum alloy with the cylinder bore surface has the same sliding characteristics and oil retention ability as the cast iron cylinder liner, without using an aluminum alloy with a high Si content. This can be done. Therefore, according to the above method, it is possible to manufacture the cylinder bore surface at a low cost while ensuring necessary characteristics on the surface of the cylinder bore.

  Further, according to claim 6, through the plasma irradiation step and the honing step, the effective load roughness Rk of the cylinder bore surface is larger than 0.65 μm, and the surface of the cylinder bore is spiraled. When the width of the pit blank area where the height difference of the unevenness is less than 2 μm is set to 1.0 mm or less, the surface of the cylinder bore is secured with scuff resistance equal to or higher than that of a cast iron cylinder liner. You will be able to

  As a material of the aluminum alloy cylinder block manufactured in this way, ADC 12 can be used as in claim 7.

The figure which shows a special roughness curve and a load curve. Schematic diagram schematically showing the property distribution on the cylinder bore surface The figure which shows the surface roughness curve along the III-III line | wire of FIG. The graph which shows the relationship between Rk + Rvk and an oil retention amount. The perspective view which shows the perspective structure of a reciprocating sliding test machine. The graph which shows the relationship between Rk + Rpk and an average friction coefficient. The graph which shows transition of the frictional force during the test with a reciprocating sliding test machine. The graph which shows the relationship between Rk and scuff time. The graph which shows the relationship between the width | variety of a pit blank area, and a scuff time.

Hereinafter, an embodiment embodying an aluminum alloy cylinder block and a manufacturing method thereof according to the present invention will be described in detail with reference to FIGS.
The aluminum alloy cylinder block of the present embodiment uses an aluminum die-cast material (ADC12) for the cylinder bore portion. The surface of the cylinder bore is subjected to honing after plasma irradiation for roughening and hardening. The plasma irradiation at this time is performed at an output of 200 W and a processing capacity of 20 cubic millimeters / second.

  Further, the surface properties of the cylinder bore are as follows. The effective load roughness Rk, the initial wear height Rpk, and the oil sump depth Rvk measured at a plurality of locations with a contact type roughness measuring machine satisfy the following conditions (A) to (C). It is formed to satisfy everything.

Rk + Rpk <1.0 μm (A)
Rk + Rvk <2.0 μm (B)
Rk> 0.65 μm (C)

Here, the effective load roughness Rk, the initial wear height Rpk, and the oil sump depth Rvk that define the conditions (A) to (C) are defined as follows.

  The curve shown on the left side of FIG. 1 is obtained by filtering the surface roughness curve in a manner defined by ISO13565 and DIN4776 and removing the waviness. Further, the load curve shown on the right side of FIG. 1 is obtained by using a special roughness curve as an extraction curve and obtained from the evaluation length method and the μm method, and corresponds to the cumulative probability density function referred to in statistics. ing.

  Further, the line segment AB shown in the figure has a width of 40% in the direction of the load length rate (tp value) in the load curve, and finds a position where the difference in height between the both ends is minimized. It shows a straight line passing through (minimum slope straight line). Note that point A in the figure is the intersection of this minimum inclination straight line and the limit line of tp = 0%, and point C is the intersection of the horizontal line from this point A and the load curve. Point B is the intersection of the minimum inclination straight line and the limit line of tp = 100%, and point D is the intersection of the horizontal line from this point B and the load curve.

  In these figures, the initial wear height Rpk is equal to the area surrounded by the 0% limit line, the side AC, and the load curve, and is on the limit line of tp = 0% that forms a right triangle with one side AC as one side. It is height. The oil sump depth Rvk is equal to the area surrounded by the 100% limit line, the side BD, and the load curve, and has a height on the 100% limit line that forms a right triangle with the side BD as one side. . The effective load roughness Rk is a difference in height between points C and D.

Incidentally, the measurement conditions of the surface roughness in the present embodiment are as follows.
Evaluation length: 0.8mm
Measurement length: 4mm
Front and rear preliminary length (running distance): Front and rear 0.4mm each
Measurement speed: 0.5 mm / s
Stylus shape: 2 μm, apex angle 60 °
Filter: Gaussian By the way, the above-described plasma irradiation of the cylinder bore surface is performed by irradiating the plasma while spirally scanning the inner periphery of the cylinder bore. In order to reduce the cost of such plasma irradiation, it is necessary to suppress the plasma irradiation amount (irradiation length per cylinder) to the minimum necessary. For this purpose, it is effective to maximize the irradiation pitch, that is, the distance between the trajectories of the irradiation center as shown in FIG. If the irradiation pitch is increased to some extent, the plasma irradiation amount is large in the vicinity of the locus of the irradiation center, and the plasma irradiation amount is small in a portion away from the irradiation center locus. Therefore, on the surface of the cylinder bore at this time, there are no areas where pits are formed by roughening by plasma irradiation (pit areas) and no conspicuous pits in the direction perpendicular to the locus of the plasma irradiation center. Pit blank areas appear alternately and repeatedly.

  FIG. 3 shows a roughness curve of the cylinder bore surface along the line III-III in FIG. Between the pit area and the pit area, a pit blank area having a height difference of less than 2 μm is formed. In the present embodiment, the plasma irradiation pitch is set so that the width of such a pit blank area is 1.0 mm or less.

Next, the reason why the conditions (A) to (C) and the width of the pit blank area are defined will be described.
The inventors changed the plasma irradiation conditions and the honing conditions, created test pieces having various surface properties, and evaluated the oil retention amount. The oil retention amount is evaluated by leaving the test piece coated with oil standing for 4 hours while standing, and measuring the mass difference before and after that. In consideration of the amount of oil consumption of the engine when applied to an actual engine, it is desirable to reduce the amount of oil retained on the cylinder bore surface.

  From the evaluation results, as shown in FIG. 4, it was confirmed that the oil retention amount has a correlation with the added value (Rk + Rvk) of the effective load roughness and the oil sump depth. This result is reasonable considering that oil accumulates in the recess formed on the cylinder bore surface. As shown in the figure, if the oil retention amount is to be equal to or less than that of a cast iron cylinder liner (0.1 mg / square cm or less), Rk + Rvk needs to be smaller than 2.0 μm.

  In addition, the inventors conducted a friction evaluation test on a large number of test pieces having different surface properties. This test is performed by creating a reciprocating sliding tester as shown in FIG. This reciprocating sliding tester includes two tables, a table 2 to which the test piece 1 is fixed and a table 4 to which the piston ring cutout piece 3 is fixed. The test machine reciprocates the table 4 up and down while pressing the test piece 1 against the cut piece 3 under a load, and the sliding friction force between the test piece 1 and the cut piece 3 at that time is the load cell. It is comprised so that an evaluation test may be performed by measuring at 5.

  From the results of the friction evaluation test using such a reciprocating sliding tester, it is confirmed that the friction has a correlation with the added value (Rk + Rpk) of the effective load roughness and the initial wear height as shown in FIG. It was. As shown in the figure, if it is desired to make the friction coefficient equal to or less than that of the cast iron cylinder liner (0.03 or less), Rk + Rpk needs to be smaller than 1.0.

  Furthermore, the inventors have also conducted a scuff resistance evaluation test for a large number of test pieces having different surface properties. This scuff resistance evaluation test is also performed using the reciprocating sliding tester shown in FIG.

  FIG. 7 shows the transition of the sliding frictional force between the test piece 1 and the cut piece 3 under test. After starting the test, the sliding frictional force between the test piece 1 and the cut piece 3 remains small, but increases rapidly when scuffing occurs. Therefore, here, the evaluation test is performed by measuring the time (scuff time) from the start of the test until the sliding frictional force increases rapidly as the index value of the scuff resistance.

  FIG. 8 shows the relationship between the effective load roughness Rk and the scuff time. From this relationship, the scuff time is equal to or longer than that of the cast iron cylinder liner (5 minutes or more) at least when the effective load roughness Rk exceeds “0.65 μm”. However, some of the test pieces having an effective load roughness Rk exceeding “0.65 μm” have a scuff time of less than 5 minutes.

  As a result of further investigation, it was confirmed that the scuff resistance has a correlation with the width of the pit blank area. FIG. 9 shows the relationship between the width of the pit blank area of the test piece located within the dotted frame in FIG. As shown in the figure, the test piece having a pit blank area width of 1 mm or more has a scuff time of less than 5 minutes. This is because, in the pit blank area, the oil retention is reduced and a local oil film breakage occurs, and the test piece 1 and the cut piece 3 are likely to be in direct contact with each other. This is thought to be due to scuffing at the starting point.

The results of the above evaluation tests are summarized as follows.
In order to keep the oil retention amount of the cylinder bore equal to or less than that of the cast iron cylinder liner, it is necessary to make the added value (Rk + Rvk) of the effective load roughness and the oil sump depth smaller than 2.0 μm.

  In order to make the friction coefficient between the cylinder bore and the piston ring equal to or less than that of the cast iron cylinder liner, it is necessary to make the added value (Rk + Rpk) of the effective load roughness and the initial wear height smaller than 1.0.

  In order to make the cylinder bore scuff resistance equal to or higher than that of a cast iron cylinder liner, it is necessary to make the effective load roughness Rk larger than 0.65 μm and the width of the pit blank area to be 1.0 mm or less. .

According to the present embodiment described above, the following effects can be obtained.
(1) In this embodiment, when the effective load roughness is “Rk”, the initial wear height is “Rpk”, and the oil sump depth is “Rvk”, the surface of the cylinder bore is “Rk + Rpk <1. 0 μm ”and“ Rk + Rvk <2.0 μm ”. In this way, the cylinder block made of aluminum alloy with the cylinder bore surface has the same sliding characteristics and oil retention ability as the cast iron cylinder liner, without using an aluminum alloy with a high Si content. This can be done. Therefore, according to the present embodiment, it is possible to manufacture the cylinder bore surface at a low cost while ensuring the necessary characteristics on the cylinder bore surface.

  (2) In the present embodiment, the effective load roughness Rk is made larger than 0.65 μm, and the width of the pit blank area formed in a spiral shape on the surface of the cylinder bore and having a height difference of less than 2 μm is set to 1 0.0 mm or less. As a result, the scuff resistance higher than that of the cast iron cylinder liner can be secured on the cylinder bore surface.

  (3) In this embodiment, since an aluminum die-cast material (ADC12) that is less expensive than a high Si material is used, an aluminum alloy cylinder block can be manufactured relatively inexpensively.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the ADC 12 is used as the material for the cylinder block, but other aluminum alloys may be used.

  DESCRIPTION OF SYMBOLS 1 ... Test piece, 2 ... Table, 3 ... Piston ring cut piece, 4 ... Table, 5 ... Load cell, Rk ... Effective load roughness, Rpk ... Initial wear height, Rvk ... Oil sump depth.

Claims (7)

An aluminum alloy cylinder block,
When the effective load roughness is “Rk”, the initial wear height is “Rpk”, and the oil sump depth is “Rvk”, the surface of the cylinder bore is
Rk + Rpk <1.0 μm and Rk + Rvk <2.0 μm
An aluminum alloy cylinder block characterized by being formed to be The effective load roughness Rk is larger than 0.65 μm, and the width of a pit blank area formed in a spiral shape on the surface of the cylinder bore and having an uneven height difference of less than 2 μm is 1.0 mm or less. 1. An aluminum alloy cylinder block according to 1. 3. The aluminum alloy cylinder block according to claim 1, wherein a surface of the cylinder bore is formed by performing a honing process after being roughened by plasma irradiation. 4. The said cylinder block is formed by ADC12. The aluminum alloy cylinder block of any one of Claims 1-3. A method for producing a cylinder block made of aluminum alloy,
Performing plasma irradiation on the surface of the cylinder bore;
Honing the surface of the cylinder bore roughened by the plasma irradiation;
The surface of the cylinder bore when the effective load roughness is “Rk”, the initial wear height is “Rpk”, and the oil sump depth is “Rvk”,
Rk + Rpk <1.0 μm and Rk + Rvk <2.0 μm
A method for producing an aluminum alloy cylinder block, wherein Through the step of performing the plasma irradiation and the step of performing the honing process, the effective load roughness Rk of the surface of the cylinder bore is larger than 0.65 μm, and the surface of the cylinder bore is spirally formed. The method for producing a cylinder block made of aluminum alloy according to claim 5, wherein the width of the pit blank area having a height difference of unevenness of less than 2 µm is 1.0 mm or less. The said cylinder block is formed by ADC12. The manufacturing method of the aluminum alloy cylinder block of Claim 5 or 6.

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