JPS6056254B2 - Cylinder with laser hardened inner surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder provided with a laser-hardened layer on its circumferential inner surface, particularly a cylinder used in an internal combustion engine, a cylinder liner, and a cylinder sleeper (hereinafter simply referred to as a cylinder). This relates to the improvement of laser-hardened layer patterns.

In recent years, with the progress in the development of high-output carbon dioxide lasers, the application of lasers to surface hardening processing has rapidly increased.

It's progressing. As is well known, since laser beams are single-wavelength lights, the beam has good focusing properties and can increase the energy density per unit area, making it possible to partially harden only the necessary areas. Due to its excellent features such as the ability to reduce distortion, its range of applications is rapidly expanding.

Naturally, hardening the inner peripheral surface of the cylinder is also considered, and various attempts are currently being made. However, an appropriate hardening pattern for cylinders that takes advantage of the characteristics of the laser has not yet been established, and the reality is that the effects of laser hardening cannot be sufficiently increased. In view of the above-mentioned circumstances, the present invention aims to provide an appropriate hardening pattern for cylinders by taking advantage of the characteristics of laser.

Conventionally, as a hardening process for a cylinder using a laser, attempts have been made to take advantage of the characteristics of the laser to perform partial hardening in a spiral, dot, or annular shape, and these efforts are achieving some degree of success.

These patterns have a coexistence of hardened parts and untreated parts, and conventional methods of imparting wear resistance such as sub-hardening, induction hardening, or hard chrome plating have been applied. This is where it differs the most. In other words, conventional methods have no choice but to treat the entire inner circumference due to limitations in the manufacturing method, but in the case of laser,
Since local hardening treatment is possible, treated areas and untreated areas can coexist. This pattern is characterized in that its effects are particularly noticeable from the middle of the engine's life onwards, and the wear resistance and scuffing resistance are significantly improved, greatly contributing to extending the life of the internal combustion engine. In other words, after the middle of the engine life in a normal cylinder, the sliding surfaces of the cylinder become shiny and the number of places that should become oil pools becomes extremely small, which increases the risk of scuffing and shortens the engine life. This was one of the reasons for the lack of growth.

Conventional methods such as sub-hardening and induction hardening are no exception to this, and although they have a remarkable effect on wear resistance up to the mid-term, they are not effective in suppressing the occurrence of scuffing after the mid-term, and the engine life is shortened. was unable to contribute to the extension of the period. On the other hand, in the case of laser hardening treatment in which a hardened layer and an untreated layer coexist, there is a difference in wear between the hardened layer 1 and the untreated layer 2 after the middle of the engine life, as shown in Figure 1. The hardened layer 1 comes to form a primary sliding surface, and the untreated layer 2 forms a secondary sliding surface, and the untreated layer, which is the secondary sliding surface, becomes a so-called oil reservoir. Since it helps supply lubricating oil, wear resistance and scuffing resistance are significantly improved, and engine life can be greatly extended. In this way, laser hardening treatment in which a hardened layer and a non-treated layer coexist has a remarkable effect on wear resistance and scuffing resistance, but in terms of internal combustion engine performance,
It has become clear that other drawbacks arise.

In other words, in the case of spiral and dotted patterns, since the untreated layer is connected in the axial direction of the cylinder, oil consumption and blow-by gas increase as the wear step shown in Figure 1 increases, especially after the middle of the engine life. It became clear that the engine life could not be extended from this point of view. In addition, in the case of an annular pattern, since the hardened layer is parallel to the piston ring in the circumferential direction, there is an excessive wear step, and the piston-ring contact with the edge of the hardened layer is strong, causing wear on the outer circumference of the piston ring. is promoted, which in turn leads to increased oil consumption and probicus.

Additionally, as the piston ring overcomes the wear step, the movement of the piston ring in the radial direction becomes large, inducing fatigue failure of the piston ring. Particularly, as shown in FIG. 2, when the width L of the untreated layer exceeds the width W of the piston ring 3, this tendency is further exacerbated and becomes a fatal defect in practice. The present invention was invented in order to eliminate the above-mentioned drawbacks and provide a cylinder that can greatly extend the life of an internal combustion engine.It has a hardened layer and a non-treated layer coexisting to improve wear resistance and scuffing resistance. While taking advantage of the improved characteristics, it is also designed to reduce oil consumption and blow-by gas at the same time.

The reasons for limiting the scope of claims will be described below.

As shown in Fig. 3, the hardened layer is provided in a band shape in the circumferential direction, and the hardened layer is formed into two or more mutually intersecting spirals 1, 1a... As a result, the hardened layer always surrounds the untreated layer, making it possible to separate the untreated layer into islands, which prevents simple spiral or dotted defects from occurring after the middle of the engine's life. This is because oil consumption and increase in blow-by gas can be significantly suppressed.

In addition, since the hardened layer always has a certain angle with respect to the sliding surface of the piston ring, the piston ring slides smoothly and the contact with the hardened layer edge is alleviated, making the piston ring shaped like an annular pattern. This is because accelerated wear and fatigue fracture can be significantly suppressed, and furthermore, by shifting the intersection positions of multiple spiral hardened layers in the cylinder axis direction in the circumferential direction, the sliding of the piston ring can be significantly suppressed. This is to prevent uneven wear on the surface and (1) to be able to supply lubricating oil evenly over the entire sliding surface of the piston ring. As described above, the cylinder according to the present invention has a characteristic hardened layer pattern, and if the pitches of the spiral band hardened layers that intersect with each other are the same, the crossing positions will be aligned in the axial direction, but the helical pitch of one side will be By changing the position, the intersection position is sequentially shifted, so the piston ring can slide more smoothly.

Forming a plurality of spiral hardened layers in the same direction also helps to finely disperse the island-like untreated layer, which helps to further improve the performance of the cylinder of the present invention. It is also an effective method to adapt to the wear condition of the cylinder by narrowing the helical pitch near the top dead center of the top ring, which is exposed to the most severe frictional conditions, and making the pitch coarser toward the lower end of the cylinder. It is also an economical method to perform the laser hardening treatment of the present invention only in the vicinity of the top dead center of the piston, where the amount of wear increases. In this case, the method of changing the pitch is effective in reducing step wear at the boundary between the hardened layer and the untreated layer. Next, we decided to laser harden the band-shaped hardened layer because the energy density is high enough to allow partial hardening, the hardening depth and width can be easily controlled, and there is no other method other than laser that can process the hardened layer in the atmosphere. This is because there is no

In addition, the reason why the band-shaped hardened layer is made into a chilled structure without graphite precipitation is as revealed by a previous application (Japanese Patent Application No. 150825-1982), in which a chilled structure without graphite precipitation and a non-chilled structure coexisted by laser. wear resistance under harsh friction conditions,
This is because it has a remarkable effect on scuffing resistance, and when applied to the cylinder according to the present invention, the effect is also remarkable.

Next, an experimental comparison example between the present invention and a conventional product will be described. [
Experimental Comparative Example 1] T-C3. l8%, Sl2. O9%, MnO. 75%,
P.O. l8%, SO. O3%, CrO. 3l% balance Fe
A CO2 gas laser device is used on the inner peripheral surface of a cylinder made of flaky graphite cast iron, with an output of 1000W and a beam feed rate of 10%.
As shown in Figure 4, pitch P1 is 57rr at 00wrm1min! n1 pitch P2 in 10 order, quenching width H 3Tm
! Cylinder A laser-hardened in a spiral shape that intersects each other, output 1000W, beam feed speed 150h
A cylinder B was produced in which a chill structure was provided by a laser in a mutually intersecting spiral shape with a pitch P1 of 5 times, a pitch P2 of 1-, and a hardened layer width H of 2 times at Imin.

In the first test, two cylinders A were installed in a 116wnφ, water-cooled 6-cylinder 7860cc 1185 horsepower diesel engine, and two cylinders were tested: an induction-hardened cylinder C made of flake graphite cast iron with the same composition as above, and an untreated cylinder. D was installed with two cylinders each and tested under a full load of 20C.

In the second test, cylinder B and the cylinders C and D were installed in the same engine, and the test was conducted under the same conditions. At this time, the opponent's top ring is
A chrome-plated ring with W=3 colors was used. For all the cylinders used in this test, the surface roughness of the inner periphery honing was set to 1μRZ or less so that the mirror-like state that appears after the middle of the engine life appears at an early stage.

Table 1 shows the results of the above two tests.

In the table, the mark O indicates that no scuffing occurred at all, the mark Δ indicates that there were many scratches although no obvious scuffing occurred, and the mark X indicates that clear scuffing occurred. The inner circumferential surfaces of the cylinders tested all had a mirror-like appearance, and it was clear that they had reached the state after the middle of the engine's life.

Under such conditions, both the untreated material and the induction hardened material have scuffing, but the cylinder of the present invention, which has both a hardened layer and an untreated layer, has no abnormalities and has no scuffing resistance. It turns out that he has excellent sex.

[Experimental Comparative Example 2] T-C 3.22%, Sl2. l5%, MnO. 79%,
P.O. 3l%, CrO. Using a CO2 gas laser device, the following four types of conventional cylinders E and F and cylinders K and M of the present invention were fabricated on the inner peripheral surface of cylinders made of flaky graphite cast iron with a balance of 28% Fe.

The cylinder E has an inner peripheral surface having a spiral laser hardening pattern, and the hardening conditions are as follows, and a schematic diagram of the hardened state is shown in FIG.

Laser hardening conditions Output: 1000W Beam feed rate: 1000wnImin Helical pitch: P5TIn Quenching width: H37m Cylinder F has an inner peripheral surface with an annular laser hardening pattern, and the hardening conditions are as follows.

A schematic diagram of the quenched state is shown in FIG. Laser hardening conditions: Output: 1000W Beam feed rate: 1000ml/min Annular spacing: L3Tn Quenching width: H379! Cylinder K has two spiral laser hardening zones 1, 1 in one direction.
The inner circumferential surface of the cylinder of the present invention has two spiral laser hardening zones 1a and 1a'' intersecting with each other, and the hardening conditions are as follows.

A schematic diagram of the quenched state is shown in FIG. Laser hardening conditions: Output: 1000W Beam feed speed: 1000TsnImin Quenching width: H3T! r! n Spiral pitch PllO7m Quenching zone interval Li5 Throat spiral pitch P22OTn Quenching zone interval L, lOm Cylinder M has two spiral laser chill zones 1 and 1'' in one direction, and two spiral laser chill zones that intersect with it. 1
The cylinder has an inner circumferential surface of the present invention provided with a and 1a'', and the laser chill conditions are as follows.

A schematic diagram of the laser chill state is shown in FIG. Laser chill conditions: Output 1000W Beam feed speed 1500m'Min Chill width H2TIr! Ft Spiral pitch PllOm Chill band interval Ll5 Ugly spiral pitch P22Om! Chill band interval! 10m or more 4 types of cylinders 98Trnφ, water cooled 4 cylinders, 2
It was installed in a 956cc 185 horsepower diesel engine and a bench test was conducted at full load of 80C with the contents shown in Table 2.

The top ring at this time was a chrome-plated ring, and the width W of the ring was 2.5 mm.

The test results are shown in FIGS. 9 and 10.

That is, FIG. 9 is a graph showing changes in oil consumption and blow-by gas over time, and is a graph showing changes in oil consumption and blow-by gas over time. l and NO.
Test No. 2, which incorporates the liner of the present invention, shows a significant increase in oil consumption and blow-by gas when the temperature exceeds 50C. 3 maintains stable oil consumption and blow-by gas emissions for up to 800 hours, demonstrating the excellent characteristics of the cylinder of the present invention. proves gender.

FIG. 10 is a graph showing the amount of wear on the cylinder and the mating top ring after the test.

The amount of wear on the cylinder is the average of the hardened layer portions at four locations near the top dead center of the top ring, and the amount of wear on the top ring is the average value of measurements at five locations in the circumferential direction of the ring thickness T. The wear amount of cylinders E, F, and K is not much different, but the wear amount of cylinder M (7) is 70 to 80% of that of E, F, and K, and its excellent wear characteristics can be applied to higher-load engines. It becomes possible.

There is not much difference in the wear of the top ring installed in the E, K, and M cylinders, but the wear of the top ring installed in the cylinder F is abnormally high, showing about three times the amount of wear.

After the test, the difference in wear between the hardened layer and the untreated layer near the top dead center of the top ring was 2 to 5 μ for cylinder E, 1 to 3 μ for cylinders K and M, and 10 to 15 μ for cylinder F.
It has an abnormally large number of μ, and is a major cause of large wear on the mating top ring.

As described in the above experimental comparative example, in the present invention, the intersection positions of the spiral laser hardened layers are arranged in a staggered manner at adjacent positions in the cylinder axis direction so as to be shifted from each other in the circumferential direction. No uneven wear on piston ring sliding surface,
Since the untreated layers surrounded by the spiral hardened layers that intersect at the same time are arranged in a staggered manner, the untreated layers act as oil reservoirs and lubricating oil is evenly supplied to all sliding surfaces of the piston ring. This allows the piston rings to slide extremely smoothly and has excellent friction and wear characteristics.It is also extremely effective in suppressing increases in oil consumption and blow-by gas even after the middle of the internal combustion engine's life, extending the life of the engine. It is a great contribution.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a cross section of a cylinder in which a hardened layer and an untreated layer are present after the middle of the engine life, and Fig. 2 shows that the width L of the untreated layer is larger than the width W of the top ring 3. FIG. 3 is a diagram showing the condition of the hardened layer of the cylinder of the present invention, and FIG.
Figures 5 to 8 are partially enlarged schematic diagrams of the cylinder A of the present invention used in [Experimental Comparative Example 2] and the inner peripheral sliding surfaces of the cylinder used in the present invention. Fig. 5 and Fig. 6 show the conventional product, Fig. 7 and Fig. 8 show the embodiment of the present invention, and Fig. 9 is the same as Fig. 7 and Fig. 8. 10 shows the amount of wear on the top rings of the cylinder and piston shown in FIGS. 7 and 8. This is a graph representing

Claims (1)

[Scope of Claims] 1. A laser-hardened layer is provided in the shape of two or more spiral bands intersecting each other in the circumferential direction on the inner peripheral surface of a cast iron or steel cylinder of an internal combustion engine, and the spiral hardened layer of the band-shaped hardened layer is A cylinder having a circumferential surface subjected to laser hardening treatment, characterized in that the respective pitches are different from each other, and adjacent spiral intersection positions in the cylinder axis direction are staggered from each other in the circumferential direction. . 2. The cylinder according to claim 1, wherein the hardened layer is laser hardened. 3. The cylinder according to claim 1, wherein the hardened layer is melted by a laser beam and has a chilled structure free of graphite precipitation.