JP2003013710A - Sliding device, and valve system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member and a valve system of an internal combustion engine capable of remarkably reducing a sliding loss on the sliding portion of a sliding device by improving a processing method and a surface shape for the sliding surfaces of the sliding member and a mating member. SOLUTION: In this sliding device, metal members are slid on each other. Dimples are provided on the surface of at least one sliding member, and the surface hardness of the other sliding member is set larger than that of the sliding member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding device in which a cam and a metal member such as a shim of an internal combustion engine valve operating device which opens and closes a valve following a cam which performs a predetermined rotary motion slides with each other. . More specifically, it belongs to the technical field relating to the surface shape and surface treatment method of the sliding member of the sliding device.

[0002]

2. Description of the Related Art In a conventional valve operating system used in an internal combustion engine, an intake valve or an exhaust valve is driven by a cam provided on a cam shaft. At that time, the cam slides on a lifter installed on the upper end of the valve, an adjusting shim mounted on the lifter, or a rocker arm. Most of the friction loss in the valve train is caused by the friction loss between a cam follower such as a lifter sliding with the cam, an adjusting shim, or a rocker arm and the cam. A technology that can reduce friction loss and contribute to the achievement of low fuel consumption of an internal combustion engine by efficient power transmission is strongly desired from the viewpoint of environmental protection measures aiming at emission control.

Conventional cam / follower surface roughness is
Ra 0.2-0.5 μm is ground, and the follower is treated with manganese phosphate salt coating to prevent seizure. Minimum oil film thickness between cam / follower is calculated
The thickness is about 0.1 μm or less, which is very small relative to the surface roughness, and it is unavoidable that metal and metal contact each other. Therefore, it is desired to smooth these sliding surfaces as much as possible to reduce sliding friction loss.

Therefore, as shown in, for example, Japanese Patent Laid-Open No. 7-118832, the sliding surface of the sliding member that is in sliding contact with the cam is finished so that the surface roughness is 0.3 μmRz or less, and It has been proposed to coat the sliding surface with titanium nitride having a hardness of Hv1000 or more by an arc type ion plating method. According to this method, there are granular projections called droplets on the sliding surface, and the projections make the sliding surface of the cam, which is the mating sliding member, a mirror surface at the initial stage of sliding, and at the same time, slide the sliding member. The droplets on the moving surface also drop off and become mirror-finished to reduce friction loss.

[0005]

However, in order to significantly reduce the friction loss further, it is possible to further make the mirror surface. To further make the mirror surface, control the generation of droplets, It is necessary to further subject the cam and the follower surface to superfinishing, which is costly, and it is necessary to suppress manufacturing variations. There is also a follower sliding surface coated with a film such as diamond-like carbon or molybdenum disulfide, which has excellent solid lubricity, but it is expensive, and the surface roughness of the follower base material, surface hardness, film thickness and If the intermediate layer is not carefully selected, there is a problem in that the sliding causes the adhesive layer to be peeled off due to insufficient adhesive force, and sufficient durability cannot be ensured.

Further, even if surface treatment such as mirror finishing is performed, there is a limit to the reduction of sliding resistance. That is, although the sliding portion is lubricated with oil, if the surface roughness is reduced, the contact between metals is reduced, but the oil film formed by the lubricating oil formed between the sliding members is not formed. Because it is thin, the shearing force of the oil is large and sliding resistance occurs. That is, it can be considered that the liquid generally in contact with the plate moves while sticking to the plate, and the flow velocity is considered to be distributed in the oil film thickness direction. Here, τ is the shear force of the oil and ∂u / is the flow velocity distribution with respect to the oil film thickness.
If ∂r, then the relational expression τ = η (∂u / ∂r) (η is a constant) holds, and the shearing force τ increases when the oil film is thin. Therefore, in order to reduce the shearing force of the oil while ensuring the smoothness of the surface, dimples are provided on the surface,
It is possible to reduce the shearing force of the oil by ensuring the oil film thickness by the dimple portion. However, when the dimples are provided on the surface, for example, when the dimples are provided on the surface by a shot peening method or the like, the periphery of the dimples rises, which makes it difficult to provide the dimples while maintaining the surface smoothness (FIG. 1).
(See (a)).

The present invention has been made in view of the above problems, and by devising a method and a surface shape for a sliding surface of a sliding member such as a cam and a follower and a sliding surface of a mating member. An object of the present invention is to provide a sliding member and an internal combustion engine valve operating mechanism capable of significantly reducing sliding loss at a sliding portion of a sliding device.

[0008]

In order to achieve the above object, in the invention according to claim 1, in a sliding device in which metal members slide with each other, dimples are provided on at least one sliding member surface, and the other dimple is provided. The surface hardness of the sliding member is set to be larger than the surface height of the sliding member provided with the dimples.

The surface of the other sliding member has a hardness of Hv1000.
A sliding member coated with the above coating is preferable.

It is preferable that the sliding member provided with the dimples has a surface roughness of Ra 0.20 μm or less, and the sliding member coated with the coating has a surface roughness of Ra 0.10 μm or less.

The surface roughness Ra will be described below. FIG. 4 is a diagram showing a concept for calculating the surface roughness. From the extraction curve f (x) extracted to represent the cross-sectional shape of a certain surface, the reference length L is extracted in the direction of the average line, and the average line of this extracted portion is taken as the X axis and the direction of longitudinal magnification is taken as the Y axis. When the extraction curve is represented by y = f (x),
It can be calculated by the following formula.

[Formula 1] That is, Ra is the area of the portion surrounded by the extraction curve and the average line divided by the reference length, and represents the average deviation in terms of statistics. Therefore, it is a numerical value that is not affected even if there are some large scratches.

Further, the area ratio of the dimples of the sliding member provided with the dimples is preferably 5-60%.

The dimples of the member provided with the dimples preferably have an equivalent circular diameter of φ5 to 100 μm and a depth of 0.3 to 5.0 μm.

The coating of the sliding member coated with the above coating may be a titanium nitride (TiN) film, a chromium nitride (CrN) film or a diamond-like carbon (DLC) film formed by an ion plating method.

Further, the surface roughness of the sliding member provided with the dimples after sliding for a short time is set to Ra0.15 μm or less, and the surface roughness of the sliding member coated with the coating is Ra0.10 μm.
The following is preferable.

Further, the method of manufacturing the sliding member provided with the dimples may be a method of forming the dimples by a shot peening method in which a steel ball of φ10 to 100 μm or a ceramic ball is irradiated on the surface.

The sliding device may be a valve mechanism for an internal combustion engine, the sliding member provided with the dimples may be a cam of a cam shaft, and the sliding member coated with the coating may be an adjusting shim or a lifter. .

[0018]

According to the present invention, by using the above-mentioned means, the sliding surface other than the recessed portion of the sliding surface provided with the dimples by sliding has a high hardness. The surface is smoothed after initial sliding and is smoothed at the same time, and at the same time, the swelling around the dimples generated during the process of providing the dimples is removed to form a surface having dimples on a smooth plane. As a result, in addition to being smoothed, the presence of dimples reduces the contact between the surface roughness protrusions, and the presence of the dimples reduces the shear resistance of the oil, resulting in a relatively large oil film thickness. In some situations, sliding resistance can be significantly reduced over simple smooth surfaces. In addition, even when the oil film thickness is small, the recessed portion becomes an oil puddle, low friction can be realized, and wear resistance is also improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a cross-sectional view of a direct drive valve operating system for an automobile internal combustion engine having an adjusting shim 3 and a cam 1 to which a sliding device according to an embodiment of the present invention is applied.

The valve 6 is inserted through the valve guide 9, and the valve lifter 4 is installed above the shaft end 6a of the valve 6. A valve spring 5 is fixed to the valve 6 between the cylinder head 7 and the valve lifter 4 by a retainer 10 and a cotter 11, and a load is applied in a direction of closing the valve 6.

As shown in the figure, an adjusting shim 3 is fitted over the valve lifter 4, and the thickness of the adjusting shim 3 is adjusted so that the clearance with the cam 1 is about 0.3 mm. There is.

The camshaft shaft 2 is driven via a timing belt by driving a crankshaft (not shown). By driving the camshaft shaft 2,
The cam 1 rotates to make sliding contact with the adjusting shim 3 to reciprocate the valve 6.

First, the adjusting shim 3 made of chrome molybdenum steel is coated with titanium nitride (TiN) or the like by the ion plating method.
The surface roughness is Ra 0.10 μm or less. The surface roughness of the adjusting shim 3 is preferably Ra0.10 μm or less. If it exceeds Ra0.10 μm, the surface of the mating cam 1 may be attacked and smoothing of the sliding surface may not proceed sufficiently. The surface hardness is Hv10 in order to polish the mating and promote smoothing.
00 or more is required, and other chromium nitride (CrN), diamond-like carbon coating (DLC), and other high hardness surface treatment may be used instead of titanium nitride coating.

The cam 1 is made of chilled cast iron, and after the surface of the cam 1 is ground and superfinished to Ra 0.01 to 0.08 μm,
By shot blasting, steel ball particles of about φ100μm were sprayed on the sliding surface, and the surface roughness of the sliding surface of cam 1 was Ra0.
It was processed to have a thickness of 20 μm. In addition to steel balls, the treatment involves spraying high hardness particles using the pressure of air or fluid,
Etching treatment or laser processing may be used, and another method may be used as long as it is a treatment capable of providing dimples on the sliding surface. When such a treatment is performed, dimples are formed on the surface of the cam 1 and the surface roughness shape is obtained as shown in the enlarged cross-sectional view of the cam 1 and adjusting shim 3 in FIG.

If the surface roughness after the dimple forming treatment such as shot blasting exceeds Ra 0.20 μm, the fitting does not proceed sufficiently, the sliding surface of the cam 1 is not smoothed, and the sliding friction resistance cannot be reduced. The area ratio of dimples is 1 to 60%.
Is preferable, and an area ratio of 15% to 50% is more preferable. If the area ratio is 1% or less, there is no effect, and if the dimples are not provided, it is almost the same, and if it exceeds 60%, the actual contact surface pressure increases, wear progresses and smoothing does not proceed, and sliding friction resistance increases. On the contrary, it grows.

The average diameter of the dimples is φ1 μm to φ100.
Perform processing so that the depth is 0.5 μm to 5.0 μm. If the average diameter is 5 μm or less, the effect is small, and if it exceeds 100 μm, the diameter becomes too large with respect to the contact area of the cam 1 and the adjusting shim 3, and the effect is small. Φ5 to φ50 μm
It is preferable to set to. The dimple depth is 0.5 μm
Below, the effect is small, and even if the dimple depth exceeds 5.0 μm, the effect does not increase further.

Next, the cam 1 and the adjusting shim 3 as described above are incorporated into a direct-acting valve operating system of an internal combustion engine for automobiles, and the cam 1 and the adjusting shim 3 are initially slid. In general, the blasted surface often rises around the dimples, as shown in FIG.
This effect also occurs when dimples are formed by a treatment other than the blast treatment. Therefore, this swelling is removed along with smoothing by the initial sliding, and dimples are formed on the smoothed surface without swelling in the periphery. The hardness of the adjusting shim 3 is cam 1
Since it is made larger than the surface, the surface of the cam 1 other than the dimples is smoothed as shown in FIG. 1 (b), and when the opponent of the adjusting shim 3 is ground, fine projections on the surface are formed. Remove and smooth.

The surface roughness of the cam 1 and the adjusting shim 3 after the initial sliding is Ra0.15 μm or less, Ra0.10 μm.
The following is desirable.

Therefore, in the above embodiment, the hardness of the adjusting shim 3 is set to be larger than that of the cam 1 surface by providing the dimples on the surface of the cam 1 and coating the surface of the adjusting shim 3 with titanium nitride. If you slide the adjusting shim 1 and the initial shim 3,
Since both sliding surfaces are smoothed and swelling around the dimples can be removed, smoothing and reduction of the oil film shearing force can be achieved at the same time, whereby sliding frictional resistance can be significantly reduced.

Further, in the embodiment, the cam 1 and the adjusting shim 3 of the direct-acting valve operating system of the internal combustion engine for automobile are slidable, but in the case of the rocker arm type operating system, the rocker is used. The arm is equivalent to an adjusting shim, and the present invention can be applied as a member that comes into sliding contact with the cam. Further, the present invention can be applied to a sliding device in which other sliding members are combined, instead of a member for slidingly contacting the cams of the valve operating system of the automobile internal combustion engine.

(Embodiment) Next, a concrete embodiment will be described. First, an adjusting shim manufactured by using chrome-molybdenum steel coated with titanium nitride similar to that in the above-mentioned embodiment was manufactured. The surface roughness before initial sliding is Ra 0.02 to 0.05 μm and the hardness is Hv 1200 to 2500.
Met.

Next, after grinding the cam surface made of chilled cast iron and superfinishing to Ra 0.01 to 0.08 μm, the particle spraying conditions of shot blasting for spraying steel ball particles of about φ100 μm on the sliding surface are changed. A cam having the surface roughness of the sliding surface, the diameter of the dimples, the depth, and the area ratio as shown in Table 1 was manufactured (Examples 1 to 6 and Comparative Example 1).
~ 8).

[Table 1] In Examples 1 to 5, a titanium nitride coating was applied to the adjusting shim, and in Example 6, DL having higher hardness was used.
C coating is applied, and the surface hardness of the adjusting shim is Hv1000 or more. The cam is given a predetermined profile by grinding and then superfinishing, and then blasting is used to provide dimples on the surface and the surface roughness is Ra 0.2 μm.
It processed so that it might become the following.

In Examples 1 to 3, the air pressure for the blast treatment was
The area rate was changed by changing the rotation speed of the irradiation surface of the cam and the number of times of irradiation, while keeping 0.2 MPa and the weight of the particle nozzle charged at 0.2 kg / min.

In Examples 4 and 5, the irradiation pressure was changed to change the depth of the dimples.

Comparative Example 1 is a combination applied to an adjusting shim and a cam of a valve train of a conventional engine for an internal combustion engine. The adjusting shim is polished and finished, and the cam is superfinished after grinding. It is a combination.

Comparative Example 2 is a comparative example in which an adjusting shim having a titanium nitride coating and a cam having no dimple are combined.

Comparative Example 3 was combined with an unadjusted adjusting shim. The hardness of the adjusting shim at this time is Hv700.

In Comparative Example 4, coating was performed after grinding so that the roughness of the adjusting shim was increased, and the surface roughness Ra was 0.15 μm.

In Comparative Examples 5 to 8, the surface roughness, the area ratio, and the dimple depth were changed by changing the blasting conditions as in the above-mentioned Examples. Under the processing conditions such that the surface roughness was large, the dimples were connected and the area ratio could not be measured in Comparative Examples 7 and 8.

Next, 1.8 liters of the above Examples and Comparative Examples 4
It was installed in a gasoline engine with 16 cylinders and the camshaft torque was measured by motoring to measure the magnitude of friction loss. 5W-30SJ was used as the lubricating oil, and the oil temperature was 80 ° C and the cam rotation speed was 300 rpm. In order to evaluate seizure and wear at the same time, the spring load used was about twice as high as that used conventionally.

The results of the above measurements and the surface roughness after sliding are shown in FIG. 2 and Table 2.

[Table 2] As a result, it can be seen that the surface roughness of the cams and adjusting shims of Examples 1 to 6 is lower than that of Comparative Examples 1, 3, 4, 5, 7, and 8, and is smoothed. At this time, the swelling around the dimples is caused by the initial sliding, as shown in FIG.
As shown in (b), it is removed together with the smoothing.

FIG. 2 is a graph plotting the relationship between the camshaft torque and the combined roughness obtained by combining the cam and shim roughness.
Here, the synthetic roughness will be described. Synthetic roughness is 2
It is a value calculated by the root mean square roughness Rq of two planes. Here, the root mean square roughness Rq is extracted from the extraction curve extracted to represent the cross-sectional shape of a surface by the reference length L in the direction of the average line, and the average line of this extracted portion is X.
The extraction curve is y = f (x) with the axis and the vertical magnification direction as the Y axis.
When expressed by, it can be obtained by the following formula.

[Formula 2] That is, Rq represents a root mean square deviation obtained by dividing a curve obtained by squaring the distance between the extraction curve and the average line and the area sandwiched by the average lines by the measurement length and then obtaining the square root. This corresponds to the standard deviation σ in statistics. If the roughness of one plane is Rq1 and the other is Rq2,

[Formula 3] And the combined roughness can be expressed. When considering the combined roughness of two planes, it is known that the arithmetic sum of the surface roughness Ra as explained in the means for solving the problem cannot be arranged well, and in the field of friction and wear, the combined roughness of two planes is known. Since it is common to organize the values using the standard deviation, the values are arranged according to the above formula.

As shown in FIG. 2, when the combined surface roughness obtained by combining the roughness of the cam and the shim becomes smaller, the cam shaft torque tends to become smaller, which is different from Comparative Example 1 which is generally used in the conventional gasoline engine. Therefore, the sliding resistance can be suppressed to a considerably low level.

Comparative examples 3, 4, 7 and 8 in which the surface roughness of cams and shims are too large, and comparative example 5 in which the area ratio of dimples is large
Has a higher sliding resistance than Comparative Example 2 in which a cam without dimples is combined.

In Examples of the present invention, Comparative Example 2 in which dimples are not provided on the cam sliding surface and Comparative Example 6 in which the area ratio is too small have synthetic roughness smaller than that of this example. However, since the dimple effect cannot be obtained, the camshaft torque is larger than that of each embodiment of the present invention. From this, it is understood that there is a limit only by further recommending smoothing, and it is effective to reduce the shearing force of the oil film by providing dimples.

Further, from Table 2, if the composite surface roughness after the initial sliding is Rq 0.2 μm or less, that is, the adjusting shim is Ra 0.1 μm or less and the cam is Ra 0.15 μm or less [calculated based on Equation 3 0.2> (0.1 ² +0.15 ² ) ^1/2 ], the sliding resistance can be made lower than that of Comparative Example 2 having no dimple. Regarding wear, almost no problematic level of wear occurred.

As described above, a dimple is provided on at least one member surface of the sliding member, and the hardness of the sliding surface of the mating member is set to be higher than the hardness of the above member, so that the sliding member having a high hardness can be obtained. The surface is polished and smoothed after the initial sliding, and at the same time, the swelling around the dimples generated during the process of providing the dimples is removed to form a surface having dimple-shaped depressions on a smooth plane.
As a result, the smoothness and the presence of dimples reduce the contact between the surface roughness protrusions, and the presence of the dimples reduces the shear resistance of the oil. Makes it possible to significantly reduce the sliding resistance over a simple smooth surface.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a cam and an adjusting shim according to an embodiment.

FIG. 2 is a diagram showing a relationship between cam / adjusting shim combined roughness and camshaft torque after initial sliding in the embodiment.

FIG. 3 is a cross-sectional view showing a valve train for an internal combustion engine according to an embodiment.

FIG. 4 is a diagram showing a concept for calculating surface roughness.

[Explanation of symbols] 1 cam 2 Camshaft axis 3 Adjusting Sim 4 valve lifter 5 valve spring 6 valves 6a shaft end 7 cylinder head 9 Valve guide 10 retainer 11 cotta

Front page continued (51) Int.Cl. ⁷ Identification code FI theme code (reference) G12B 3/06 G12B 3/06 (72) Inventor Yutaka Mabuchi 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. ( 72) Inventor Shinji Asano 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Makoto Kano 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa 2F078 BA17 3G016 AA05 AA06 AA19 BA19 BB05 BB06 CA04 EA02 FA19 FA20 FA21 GA00 GA02 3J011 CA05 KA07 PA02 QA03 SB12 SB13 SE02 4K029 AA02 BA34 BA58 BA60 BD04 CA03

Claims (9)

[Claims] 1. In a sliding device in which metal members slide with each other, dimples are provided on the surface of at least one sliding member, and the surface hardness of the other sliding member is greater than the surface hardness of the sliding member provided with the dimples. A sliding device characterized by being set larger. 2. The sliding device according to claim 1, wherein at least one sliding member surface is provided with dimples, and the other sliding member surface is coated with a coating having a hardness of Hv1000 or more. Sliding device characterized by 3. The sliding device according to claim 1, wherein the dimple-provided sliding member has a surface roughness Ra of 0.20 μm.
A sliding device characterized in that the sliding member coated with the coating has a surface roughness Ra of 0.10 μm or less. 4. The sliding device according to claim 1, wherein the sliding member provided with the dimples has an area ratio of dimples of 5 to 60%. 5. The sliding device according to claim 4, wherein the dimples of the member provided with the dimples have an equivalent circular diameter of φ5 to 100 μm and a depth of 0.3 to 5.0 μm. Sliding device. 6. The sliding device according to claim 1, wherein the coating of the sliding member coated with the coating is titanium nitride (TiN) formed by an ion plating method.
A sliding device characterized by being a film, a chromium nitride (CrN) film, or a diamond-like carbon (DLC) film. 7. The sliding device according to claim 3, wherein the surface roughness of the sliding member provided with the dimples after a short time sliding is Ra 0.15 μm or less, and the coating is coated. A sliding device characterized in that the surface roughness of the member is Ra 0.10 μm or less. 8. The sliding device according to claim 1, wherein a method for manufacturing a sliding member provided with the dimples comprises:
A sliding device characterized in that a dimple is formed by a shot peening method in which a surface of a 100 μm steel ball or a ceramic ball is irradiated. 9. The sliding device according to claim 1, wherein the sliding device is a valve operating mechanism for an internal combustion engine, the sliding member provided with the dimples is a cam of a cam shaft, and the coating is coated. A valve mechanism for an internal combustion engine, wherein the sliding member is an adjusting shim or a lifter.