JP3414100B2 - Tappet roller bearing - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention A tappet roller bearing according to the present invention is incorporated in a valve train of an engine to reduce the friction of the valve train so that the tappet roller can be used during engine operation. To reduce the fuel consumption rate. [0002] aims to friction reduction in the BACKGROUND ART Engine internal, with the aim of reducing fuel <br/> consumption rate, the rotation of the camshaft in synchronism with the crankshaft of the air supply and exhaust valves It is common practice to incorporate a tappet roller bearing into the portion that converts to reciprocating motion. Figs.
10 shows a tappet roller bearing described in Japanese Patent Publication No. 108806. A rocker arm 3 is provided opposite to a cam 2 fixed (generally, integrally formed) to a camshaft 1 which rotates in synchronization with the crankshaft of the engine and which receives the movement of the cam 2. Have been. A pair of support walls 4, 4 are provided at an end of the rocker arm 3 (left end in FIGS. 1 and 2) at intervals. A hollow or solid shaft 5 made of steel is bridged between the pair of support walls 4. Both ends of the shaft 5 are not quenched, but are left raw. When fixing the shaft 5,
The unquenched portion is caulked toward the inner peripheral surfaces of the through holes 7 formed in the pair of support walls 4. As described above, the roller 6 is rotatably supported around the shaft 5 spanned between the pair of support walls 4, 4.
The outer peripheral surface of the roller 6 is in contact with the outer peripheral surface of the cam 2. According to the tappet roller bearing configured as described above, the frictional force acting between the rocker arm 3 and the cam 2 can be reduced, and the fuel consumption rate during engine operation can be reduced. Engine oil is supplied to the installation portion of such a tappet roller bearing during operation of the engine. The engine oil lubricates between the outer peripheral surface of the cam 2 and the outer peripheral surface of the roller 6, and between the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6. It is necessary that the camshaft 1 including the cam 2 be made of cast iron or bearing steel, and the roller 6 and the shaft 5 be made of high carbon chromium bearing steel. It is generally used from the viewpoint of reducing material costs and processing costs while ensuring high strength. And, by devising the surface roughness of the peripheral surface of each member, lubrication of a sliding contact portion between the members during operation of the engine is ensured. In order to ensure such lubrication, the shaft 5 is made of phosphor bronze and the roller 6 is made of high carbon chromium bearing steel. In addition, it is also possible to open an oil supply hole for supplying engine oil to the rocker arm 3 and the shaft 5, for example.
As described in -32210, it has been conventionally proposed. Further, the roller 6 may be made of a ceramic such as silicon nitride, for example, as disclosed in JP-A-4-15296, JP-A-62-203911, and JP-A-3-10.
As described in, for example, Japanese Patent Publication No. 8806, it has been conventionally proposed. [0006] However, in the case of the above-described tappet roller bearing known in the related art, there are the following points to be solved. When the shaft 5 and the roller 6 are made of high carbon chromium bearing steel, surface damage called smear occurs on both the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 depending on operating conditions. . Such surface damage occurs due to the fact that the contact portions between the peripheral surfaces 5a and 6a of the two members 5 and 6 become non-lubricated during the assembly operation. That is, a processing oil such as a cutting oil that adheres at the time of bearing processing, and a rust-preventive oil for preventing corrosion during transportation are attached to the surfaces of the two members 5 and 6. If these oils remain, lubrication between the two peripheral surfaces 5a and 6a can be achieved to some extent immediately after the start of operation of the engine. However, in the engine assembly process in recent years, these oils are supplied to the bearing and the rocker arm 3.
In order to prevent chips and the like generated during the assembling process from adhering and adversely affecting as foreign matter during operation, a minimum amount of necessary oil is left by a washing operation to wash away. For this reason, in the engine immediately after assembly, the contact portion between the two peripheral surfaces 5a and 6a is in a state close to non-lubrication. When the engine is started from this state, the two peripheral surfaces 5a and 6a rub strongly against each other in a temporary non-lubricated state for a short time until the engine oil is supplied. As a result, the above-mentioned surface damage occurs on both of the peripheral surfaces 5a and 6a. If the surface damage generated in this way is remarkable, there is a possibility that the contact portion between the outer peripheral surface of the cam 2 and the outer peripheral surface of the roller 6 is seized. Even when the surface damage is slight, minute projections are formed on both of the peripheral surfaces 5a and 6a, and even after the engine oil is supplied by the projections, these peripheral surfaces 5a , 6a are not completely lubricated in the lubricating state of the sliding portion. As a result, when the surface fatigue of each of the peripheral surfaces 5a and 6a increases with time, or when the oil film formation cannot follow a rapid speed fluctuation such as when the engine is rapidly accelerated or decelerated, significant surface damage locally occurs. Can occur. In addition, devising the surface roughness of each of the peripheral surfaces 5a, 6a of both members 5, 6 is intended for effective use of the supplied engine oil, and does not contribute to preventing surface damage in a non-lubricated state. . Further, if the outer peripheral surface 5a of the phosphor bronze shaft 5 and the inner peripheral surface 6a of the roller 6 made of high carbon chromium bearing steel are brought into contact with each other, dissimilar metals come into contact with each other. However, the effect of preventing surface damage in an unlubricated state is insufficient. Further, if the roller 6 is made of a ceramic such as silicon nitride, the material cost and processing cost of the roller 6 increase.
Further, the ceramic roller 6 is not only easily broken than a metal roller, but also has a strong aggressiveness to the metal cam 2 and easily wears the outer peripheral surface of the cam 2 significantly. Furthermore,
Since the amount of thermal expansion of the ceramic roller 6 is smaller than that of the metal shaft 5, a change in the gap size between the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 due to the operation and stop of the engine. Becomes larger. Therefore, when the engine temperature is low,
Problems such as generation of vibration at the support portion of the roller 6 are likely to occur. The outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6
If a needle is provided between the tappet roller bearing and the tappet roller bearing, it is possible to prevent the occurrence of damage such as seizure in a short time from the start of the assembled engine to the supply of engine oil. It is possible. However, in the case of a rolling bearing incorporating a needle, if the sludge increases due to a decrease in detergent due to the deterioration of the engine oil over time, the wear of the metal surface constituting the needle progresses, and the durability of the tappet roller bearing portion increases. Be impaired. For this reason, the structure in which the roller 6 is rotatably supported without using a rolling bearing around the shaft 5 (by means of a sliding bearing) can prevent the occurrence of damage such as seizure in the short time. The realization of is desired. The tappet roller bearing of the present invention has been made in view of such circumstances. The tappet roller bearing of the present invention rotates in synchronization with the crankshaft of the engine, for example, as shown in FIGS. Cam 2 fixed to camshaft 1
And a pair of support walls 4, 4 provided opposite to the cam 2 and formed at intervals on a member (rocker arm 3) which receives the movement of the cam 2, and a pair of support wall portions 4,
4 comprises a steel shaft 5 suspended between them and a steel roller 6 rotatably supported around the shaft 5. In particular, in the tappet roller bearing of the present invention, the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6 of the roller 6 are provided.
a with respect to the outer diameter of the shaft 5 is 0.04 to
By interposing a gap 8 of 1.0%, the roller 6 is rotatably supported around the shaft 5 based on sliding contact between the outer peripheral surface 5a and the inner peripheral surface 6a.
The reason for limiting the size of the gap 8 as described above is as follows.
When the shaft 5 and the roller 6 each made of steel such as SUJ2 are combined , in order to prevent the surface damage of the both peripheral surfaces 5a, 6a, a surface treatment layer as described below is formed, and an oil is formed. This is to maintain a contact state in which smear does not easily occur on both of the peripheral surfaces 5a and 6a even when starved (lubricating oil depleted state). Further, a surface treatment layer for reducing friction is formed on at least one of the inner peripheral surface 6a of the roller 6 and the outer peripheral surface 5a of the shaft 5 (or 6a). Then, the thickness of the surface treatment layer is set to 5 to 95% of the gap 8.
And In addition, as a surface treatment layer that reduces such friction
Uses any of the following . Reaction layer of compound of sulfur and iron. A reaction layer of a compound of sulfur and iron containing nitrogen. Reaction layer of phosphate compound of phosphorus and iron. A treatment layer obtained by baking a simple substance or a mixture of molybdenum disulfide (MoS ₂ ) and polytetrafluoroethylene (PTFE) together with a thermosetting synthetic resin. MoS ₂ and PTFE are formed on the surface of any one of the above reaction layers.
And a treatment layer obtained by firing a simple substance or a mixture thereof with a thermosetting synthetic resin. In the case of the tappet roller bearing of the present invention configured as described above, by regulating the gap 8 between the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6, The surface pressure applied to the contact portion between these two peripheral surfaces 5a and 6a can be set to an appropriate value. For this reason, even if the engine is operated in an almost non-lubricated state for a short period of time immediately after the start of the operation of the engine until the engine oil spreads to the tappet roller bearing portion, even if the both peripheral surfaces 5 are not lubricated.
a and 6a are not seriously damaged, and seizure resistance and durability are improved. Further, since a surface treatment layer for reducing friction is formed on one or both of the peripheral surfaces 5a and 6a, lubrication between the peripheral surfaces 5a and 6a is prevented by this surface treatment layer. Can be secured. Therefore, it is possible to more effectively prevent the surface damage on both of the peripheral surfaces 5a and 6a. As a result, no harmful irregularities are formed on both the peripheral surfaces 5a and 6a, and the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 can be lubricated well. The durability of the roller 6 can be improved. EXAMPLES Experiments performed to confirm the effects of the present invention will be described. The experiment was performed using a surface damage testing machine as shown in FIG. 3 as a bench surface surface damage reproduction test assuming actual use conditions. A ring 11 is pressed into an intermediate portion of a shaft 10 driven to rotate by a pulley 9. This ring 11 corresponds to the cam 2 (FIGS. 1 and 2).
A roller 6 that presses against the outer peripheral surface of the ring 11 is rotatably supported around the shaft 5. Six types of rollers 6 having an inner diameter in the range of 8.000 to 8.160 mm are used.
Six types of 004 to 20.400 mm were prepared, for a total of 12 types. As the shaft 5 corresponding to the roller 6 having an inner diameter of 8.000 to 8.160 mm, the shaft 5 having an outer diameter of 8.000 mm is used as the shaft 5 corresponding to the roller 6 having an inner diameter of 20.004 to 20.400 mm. , Each having an outer diameter of 20.000 mm. By combining such a shaft 5 and the roller 6, the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 are combined.
The ratio of the gap 8 (FIGS. 1-2) to the outer diameter of the shaft 5 is 0.02%, 0.04%, 0.5%, and 1.
It was changed in six steps of 0%, 1.2% and 2.0%. These dimensions and ratios (%) are values at room temperature.
The roller 6 is made of SUJ2 and has a surface hardness of HRc61.
The material of the shaft 5 is SUJ2 and the surface hardness is HR
Two types, c61 and phosphor bronze, were used. At the time of the test, the roller 6 was set at 2750 rpm.
The roller 6 is rotated on the outer peripheral surface of the ring 11 by a load lever 12 through a steel ball 13 while rotating at 1 m.
It was pressed with a load of 25 kgf. Also, the inner peripheral surface 6a of the roller 6
Lubricating oil (engine oil) between the shaft and the outer peripheral surface 5a of the shaft 5
Is supplied, lubricating oil is dropped on the outer peripheral surface 5a of the roller 6, the shaft 10 is started, and when the rotation reaches a steady state, the supply of lubricating oil is stopped.
Operation was continued. Then, the time until the current value of the electric motor for driving the shaft 10 became an overcurrent value was determined as the endurance time. The results are shown in the following Tables 1 and 2 and FIG. The circles in Table 1 and FIG. 4 indicate the experimental results when both the shaft 5 and the roller 6 were made of SUJ2.
4 indicate the experimental results when the roller 6 was made of SUJ2 and the shaft 5 was made of phosphor bronze. [Table 1] [Table 2] As is clear from Tables 1 and 2 and FIG. 4, the size of the gap 8 between the inner peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 is constituted by these two peripheral surfaces 5a, 6a. Greatly affects the durability of the sliding bearing portion. That is, a film of lubricating oil is formed on the sliding contact surface between the two peripheral surfaces 5a and 6a to prevent metal contact at the contact portion between the two peripheral surfaces 5a and 6a. When the oil is extremely short, the size of the gap 8 has a great influence on the durability. First, when the size of the gap 8 is less than 0.04% of the outer diameter of the shaft 5, the contact area between the two peripheral surfaces 5a and 6a becomes too large, and these two peripheral surfaces 5a, 6
The oil film of the lubricating oil is less likely to be held at the contact portion a, and metal contact is more likely to occur at this contact portion, and the durability is reduced. Conversely, if the size of the gap 8 exceeds 1.0% of the outer diameter of the shaft 5, the contact area becomes too small, the surface pressure of the contact portion becomes excessive, and the durability is also lowered. descend. Further, when the material of the shaft 5 and the material of the roller 6 are different, the size of the gap 8 changes due to a temperature rise during operation. It is thought that it will affect. On the other hand, as is clear from the comparison between Tables 1 and 2 and the comparison between the circles and the triangles in FIG.
Even if the material is the same or different,
Almost the same tendency was observed in the relationship between the size of the steel and the durability. That is, the size of the gap 8 between the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 is set to be equal to 0.
If it is restricted to the range of 04 to 1.0%, the durability of the sliding support portion of the roller 6 by the shaft 5 can be ensured. A similar experiment was conducted by changing the inner diameter of the roller 6 in the range of 5 to 30 mm, but this tendency was the same. Next, in order to further improve the durability of the sliding support portion, the effect of forming a surface treatment layer for reducing friction on the outer peripheral surface 5a or the inner peripheral surface 6a was confirmed. I will explain about the experiment. That is, as described above, at the beginning of the operation start of the engine, the outer peripheral surface 5a and the inner peripheral surface 6a are in sliding contact with almost no lubricating oil.
Therefore, in order to prevent the peripheral surfaces 5a, 6a from being damaged at the beginning of the operation, the peripheral surfaces 5a, 6a are required.
It is effective to form the surface treatment layer on one or both of a and 6a. The experiments described below were performed to confirm the effectiveness of the surface treatment layer. This experiment is similar to the experiment conducted to confirm the effectiveness of restricting the size of the gap 8 described above.
This was performed using a surface damage tester as shown in FIG. The material of the roller 6 and the shaft 5 is SUJ2, and the surface hardness is H.
Rc62. Further, a surface treatment layer for reducing friction was formed on the inner peripheral surface 6 a of the roller 6. The roller 6 has an inner diameter of 8.82 mm, an outer diameter of 20 mm, and a width of 8 mm. Also, shaft 5
The dimension of the gap 8 between the outer peripheral surface 5a and the inner peripheral surface 6a of the roller 6 was 0.020 mm (20 μm). The size of the gap 8 corresponds to 0.23% of the outer diameter of the shaft 5 of 8.80 mm. The same experiment was conducted using the phosphor bronze shaft 5 and the dimension of the gap 8 was adjusted to 0.050 mm (50 μm) or 0.160 mm.
(160 μm), and this dimension is 0.58 of the outer diameter of the shaft 5.
%. The above-mentioned surface treatment layer was formed corresponding to the above. That is, first, a base was formed on the inner peripheral surface 6a of the roller 6 by zinc phosphate treatment, and then a low friction material layer was formed on the surface of the base. In order to form this low friction material layer, MoS ₂ , PTFE, and a thermosetting synthetic resin were dispersed in an organic solvent to prepare a coating solution. Then, after applying the coating liquid to the inner peripheral surface 6a, the roller 6 was heated in a heating furnace at 180 ° C. for 60 minutes to fire the low friction material layer. The thickness control of the surface treatment layer was performed on both the base and the low friction material layer. The thickness of the underlayer was adjusted in the range of 0.3 to 5 μm by adjusting the concentrations of phosphoric acid and zinc. The thickness of the low friction material layer was adjusted by adjusting the viscosity of the coating liquid. The coating liquid is applied to the inner peripheral surface 6a by (1) a spray method using a spray, (2) a dipping method in which the roller 6 is dipped in the coating liquid, and (3) a roller 6 A so-called glass coating method or the like, in which coating is performed while moving, is selected and adopted according to the shape and size of the roller 6, the thickness of the surface treatment layer to be formed, and the like. For example, when the outer diameter of the shaft 5 is small and the dimension of the gap 8 between the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 is small, the thickness of the surface treatment layer is set to a necessary minimum. Need to be kept to a minimum. In such a case, the method (3) is effective. On the other hand, axis 5
Since the outer diameter is as large as 10 mm or more and the size of the gap 8 is large, when the thickness of the surface treatment layer can be increased,
The method (1) is effective. In any case, the thickness of the surface treatment layer is controlled by performing a lapping process using # 1200 emery paper on the surface of the surface treatment film formed in advance and performing ultrasonic cleaning in hexane. The film thickness was adjusted to have the ratio shown in Table 3 described below. In a test for measuring the durability of a plurality of samples obtained as described above, the roller 6 is rotated by the load lever 12 on the outer peripheral surface of the ring 11 while rotating the roller 6 at 3000 rpm. , 100 through the steel ball 13
It was pressed with a load of kgf. Further, the inner peripheral surface 6a of the roller 6 and the outer peripheral surface 5a of the shaft 5 are not lubricated, and the outer peripheral surface of the roller 6 and the outer peripheral surface of the ring 11 are such that these two outer peripheral surfaces are not seized. (0.1 cc / min) of lubricating oil (deteriorated engine oil) was dropped. Then, the time until the current value of the electric motor for driving the shaft 10 became an overcurrent value was determined as the endurance time. The same test was partially performed for the case where the gap was 8 μm and the case where the gap was 160 μm. The results are shown in the following Tables 3, 4 and FIG. In addition, in the columns with “-” in Tables 3 and 4, the experiments using the corresponding combinations were not performed. [Table 3] [Table 4] As is clear from Tables 3 and 4 and FIG. 5, when the thickness ratio of the surface treatment layer to the gap 8 is less than 5%, the lubricating action of the surface treatment layer cannot be sufficiently obtained. Sufficient durability cannot be obtained. On the other hand, if the film thickness ratio exceeds 95%, the surface treatment layer and the outer peripheral surface 5a of the shaft 5 are formed.
And lubricating oil hardly enters between them, so that sufficient durability cannot be obtained. Even when the surface treatment layer is formed on the outer peripheral surface 5a of the shaft 5 instead of the inner peripheral surface 6a of the roller 6,
Naturally, similar results can be obtained. Thus, a surface treatment layer for reducing friction is provided on one or both of the outer peripheral surface 5a of the shaft 5 and the inner peripheral surface 6a of the roller 6 by 5 to 9
It can be seen that if the film is formed at a film thickness ratio of 5%, the lubricating property between the two peripheral surfaces 5a and 6a can be ensured. In particular, when the film thickness ratio is regulated in the range of 10 to 50%, the lubricity becomes more favorable. A similar experiment was conducted by changing the inner diameter of the roller 6 in the range of 5 to 30 mm, but this tendency was the same. Since the tappet roller bearing of the present invention is constructed and operates as described above, the tappet roller bearing not only prevents surface damage in the initial state of engine operation but also prevents seizure. The lubricating state thereafter is improved, and sufficient durability can be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut plan view of a tappet roller bearing. FIG. 2 is a sectional view taken along line AA of FIG. FIG. 3 is a vertical side view of the surface damage tester. FIG. 4 is a diagram showing the effect of the size of a gap on durability. FIG. 5 is a diagram showing the effect of the thickness ratio of the surface treatment layer to the gap on the durability. [Description of Signs] 1 camshaft 2 cam 3 rocker arm 4 support wall 5 shaft 5a outer peripheral surface 6 roller 6a inner peripheral surface 7 through hole 8 gap 9 pulley 10 shaft 11 ring 12 load lever 13 steel ball

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-183007 (JP, A) JP-A-59-180115 (JP, A) JP-A-59-180114 (JP, A) 19805 (JP, U) Munemune Soda and four others, “Mechanical Design Series, Design of Bearings”, Japan, Ohm Publishing Co., Ltd., January 20, 1969, 1st edition, 3rd edition, p80 −82 (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 1/18 F01L 1/14

Claims (1)

(57) [Claim 1] A cam fixed to a camshaft rotating in synchronization with a crankshaft of an engine, and a member provided opposite to the cam and receiving the movement of the cam. A pair of support walls formed at intervals, a steel shaft spanned between the pair of support walls, and a steel roller rotatably supported around the shaft. In the tappet roller bearing, the ratio between the outer peripheral surface of the shaft and the inner peripheral surface of the roller is 0.04-1.
A gap of 0% is interposed, and at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the roller is
The surface treatment layer for reducing friction, which is selected from the following, has a film thickness ratio of 5 to the thickness of the gap.
A tappet roller bearing, wherein the roller is rotatably supported around the shaft by a sliding contact between the outer peripheral surface and the inner peripheral surface by forming the roller at about 50% . Reaction layer of compound of sulfur and iron. A reaction layer of a compound of sulfur and iron containing nitrogen. Reaction layer of phosphate compound of phosphorus and iron. Molybdenum disulfide (MoS ₂ ) and polytetrafluoroethylene
Thermosetting synthesis of simple substance or mixture with PTFE
A treated layer obtained by baking with resin. On the surface of any of the reaction layer of the ~, and MoS ₂
A simple substance or mixture of PTFE and thermosetting synthetic resin
A stack of treatment layers obtained by firing together.