JP2004278322A - Cam-follower device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability by reducing sliding resistance between an outer peripheral surface of an inner diameter side roller 8 and an inner peripheral surface of an outer diameter side roller 9, and restraining abrasion of these respective peripheral surfaces. <P>SOLUTION: Surface treatment layers 10 and 10a for reducing friction are formed on a surface of both rollers 8 and 9. Among both these surface treatment layers 10 and 10a, surface roughness of a part positioned on the outer peripheral surface of the inner diameter side roller 8 and the inner peripheral surface of the outer diameter side roller 9 is set to 0.02 to 0.20 Ra. The problem is solved by forming a lubricating oil film having sufficient strength over the whole periphery between both mutual peripheral surfaces by adopting this constitution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The cam follower device according to the present invention is used as a driven component such as a fuel injection device of an engine or a drive device for an intake / exhaust valve, and is used, for example, to convert the rotation of a camshaft into a reciprocating rocking motion of a rocker arm.
[0002]
[Prior art]
In order to reduce the friction inside the engine and reduce the fuel consumption rate, a tappet roller is incorporated in the part that converts the rotation of the camshaft synchronized with the crankshaft into the reciprocating motion of the intake and exhaust valves. It is common practice to use a cam follower device. FIGS. 1 and 2 show an example of a cam follower device incorporating a tappet roller, which is described in, for example, Patent Literature 1 and has been widely known.
[0003]
A rocker arm 3 that receives the movement of the cam 2 is provided opposite to a cam 2 fixed to a cam shaft 1 that rotates in synchronization with a crankshaft of the engine. At the end of the rocker arm 3, a pair of support walls 4, 4 are provided at an interval from each other. A hollow or solid support shaft 5 made of steel is bridged between the pair of support walls 4 and 4. Both ends of the support shaft 5 are not quenched, but are raw. When the support shaft 5 is fixed, the unhardened portion is formed on the pair of support wall portions 4, 4. It is caulked toward the inner peripheral surfaces of the holes 7 and 7. As described above, the roller 6 is rotatably supported around the support shaft 5 spanned between the pair of support walls 4, 4, and the outer peripheral surface of the roller 6 is fixed to the cam 2 is in contact with the outer peripheral surface.
[0004]
According to the cam follower device 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 cam follower device when the engine is operating. 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 of the support shaft 5 and the inner peripheral surface of the roller 6.
[0005]
In order to reduce the rotational resistance of the roller, it has been conventionally known that the roller has a double structure, as described in Patent Document 1 and the like. 3 and 4 show a conventional structure described in Patent Document 1. FIG. A steel inner roller 8 is rotatably supported around a support shaft 5 supported by the rocker arm 3 (see FIGS. 1 and 2), and a steel outer roller 8 is further provided around the inner roller 8. The radial roller 9 is rotatably supported with respect to the inner roller 8. In this way, the roller has a double structure and the sliding surface is formed at two places, so that the rotation of the outer diameter side roller 9 engaging with the cam 2 is performed smoothly.
[0006]
In addition, the inner surface side roller 8 and the outer surface side roller 9 (both inner and outer peripheral surfaces and both end surfaces in the axial direction) are subjected to a surface treatment for improving lubricity with a mating surface, and the inner surface side roller 8 is subjected to surface treatment. Surface treatment layers 10 and 10 a are formed on the surface of the outer diameter side roller 9 and the outer diameter side roller 9. Such surface treatment layers 10 and 10a are formed on the mating surfaces, that is, the outer peripheral surface of the support shaft 5, the inner peripheral surface of the outer diameter roller 9, the outer peripheral surface of the inner roller 8, and the outer peripheral surface of the cam 2. It has a function of reducing the coefficient of friction of the frictional engagement portion to smoothly rotate these rollers 8 and 9.
[0007]
As described above, as a surface treatment method for forming the surface treatment layers 10 and 10a on the surfaces of the inner and outer rollers 8 and 9, a solid lubricating film treatment and a nitrocarburizing treatment can be adopted. . As the surface treatment layers 10, 10a formed by the solid lubricating film treatment, the following (1) to (5) can be used.
{Circle around (1)} A reaction layer of a compound of sulfur and iron.
{Circle around (2)} A reaction layer containing nitrogen in the above [1].
(3) Reaction layer of a phosphate compound of phosphorus and iron.
{Circle around (4)} 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.
(5) A single or mixture of molybdenum disulfide and polytetrafluoroethylene is fired together with a thermosetting synthetic resin on the surface of any one of the reaction layers (1) to (3) above. Of processed layers to be overlapped.
As the soft nitriding treatment, the following treatments (6) to (8), which have a surface hardness of Hv 650 or more and a treatment layer thickness of 15 μm or more, can be used.
(6) Salt bath nitriding treatment (tufftriding treatment).
(7) Gas nitrocarburizing treatment.
(8) Ion nitrocarburizing treatment.
[0008]
According to the conventional structure configured as described above, even in the case of poor lubrication, it is possible to effectively prevent the occurrence of damage such as remarkable wear and seizure. That is, when the outer diameter roller 9 rotates with respect to the support shaft 5, the outer peripheral surface of the support shaft 5 and the inner peripheral surface of the inner roller 8 are aligned with the outer peripheral surface of the inner roller 8. And the inner peripheral surface of the outer diameter side roller 9 respectively slide. At this time, the inner and outer peripheral surfaces of the inner and outer rollers 8 and 9 are provided with the above-described surface treatment layers 10 and 10a, respectively, so that the sliding between the peripheral surfaces can be smoothly performed. Can be done. Therefore, even after the engine incorporating the cam follower device is assembled, immediately after the first startup, and before the engine oil is fed into the roller installation portion of the cam follower device, damage to the above-mentioned peripheral surfaces such as remarkable wear and seizure is caused. Can be effectively prevented.
[0009]
The surface roughness of the portion of each of the surface treatment layers 10 and 10a that is in sliding contact with the mating surface is not particularly described in Patent Document 1. However, when the invention described in Patent Document 1 is practiced, the surface roughness of the above-mentioned portion is not particularly considered, and in fact, a value considerably larger than 0.2 Ra (0.3 to 0). .4Ra or more).
[0010]
[Patent Document 1]
JP 2000-34907 A
[Problems to be solved by the invention]
If the surface treatment layers 10, 10a are formed on the surfaces of both rollers 8, 9 with a cam follower device of a double structure provided with both inner and outer diameter rollers 8, 9, the friction coefficient of each sliding contact portion can be reduced. It is possible to reduce the damage that occurs immediately after the first startup. However, when lubrication after the engine oil is fed into the roller installation portion after a lapse of time after the orbit is considered, improvement is desired. That is, if the surface roughness of the portion of the surface treatment layers 10 and 10a that comes into sliding contact with the mating surface has a large value, it is difficult to form a good oil film on the portion, as conventionally performed. .
[0012]
Specifically, the projections existing in a part of the surface treatment layers 10 and 10a easily come into direct contact with the mating surface (without an oil film), and the parts are easily damaged. In particular, the gap existing between the inner peripheral surface of the outer-diameter roller 9 and the outer peripheral surface of the inner-diameter roller 8 is small, and the supply of the lubricating oil into this gap is not always sufficient. Therefore, regarding the sliding portion between the two peripheral surfaces, consideration must be given to effectively utilizing a small amount of lubricating oil and forming a strong lubricating oil film on the sliding portion.
The cam follower device of the present invention has been made in view of such circumstances.
[0013]
[Means for Solving the Problems]
The cam fore device of the present invention includes a rocking member such as a rocker arm, a support shaft, an inner diameter roller, and an outer diameter roller, as in the case of the conventional structure shown in FIGS.
The swinging member is provided opposite to a cam fixed to a camshaft that rotates in synchronization with the crankshaft of the engine, and swings by receiving the movement of the cam.
The end of the support shaft is supported by the swing member.
The inner diameter side roller is rotatably supported around the support shaft.
The outer-diameter roller is rotatably supported around the inner-diameter roller so as to be rotatable with respect to the inner-diameter roller, and the outer peripheral surface thereof is brought into contact with the outer peripheral surface of the cam during use.
A surface treatment layer is formed on at least the inner peripheral surface of the outer-diameter roller and the outer peripheral surface of the inner-diameter roller to improve the lubricity with the mating surface.
In particular, in the cam follower device of the present invention, the surface roughness of each of these surface treatment layers is set to 0.02 to 0.20 Ra (center line average roughness, unit: μm).
[0014]
[Action]
As described above, in the case of the cam follower device of the present invention, a surface treatment layer is formed on the inner peripheral surface of the outer diameter side roller and the outer peripheral surface of the inner diameter side roller to improve lubricity with a mating surface, Further, since the surface roughness of each surface treatment layer is set to 0.02 to 0.20 Ra, a good oil film can be formed on the sliding portion between the two peripheral surfaces. For this reason, even in the case of insufficient lubrication, in which sufficient lubricating oil cannot be sent between these two peripheral surfaces, the lubricating oil is efficiently utilized to prevent the above-mentioned surface treatment layers from being strongly rubbed against each other. However, it is possible to effectively prevent the occurrence of damages such as remarkable wear and seizure on each of these surface treatment layers.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. In the case of this example, the surface (both inner and outer peripheral surfaces and both end surfaces in the axial direction) of the inner diameter side roller 8 and the outer diameter side roller 9 is subjected to a surface treatment for improving lubricity with a mating surface. Surface treatment layers 10, 10 a are formed on the surface of the roller 8 and the outer diameter side roller 9. Such surface treatment layers 10 and 10a are formed by the solid lubricating film treatment described in the above (1) to (5) or the soft nitriding treatment shown in the (6) to (8).
[0016]
When the present invention is applied to such a structure shown in FIGS. 3 and 4, at least the outer peripheral surface portion of the inner diameter side roller 8 and the outer diameter side The surface roughness of the inner peripheral surface portion of the roller 9 is set to 0.02 to 0.20 Ra. More preferably, the inner surface of the inner roller 8 and the outer surface of the outer roller 9 also have a surface roughness of 0.02 to 0.20 Ra. As described above, in order to reduce (smoothly) the value of the surface roughness of each peripheral surface portion to 0.02 to 0.20 Ra, after forming the surface treatment layers 10 and 10a, the peripheral surface The parts are subjected to finishing such as super finishing, lap finishing, and honing finishing. Also, the surface roughness of the outer peripheral surface of the support shaft 5 and the outer peripheral surface of the cam 2 (see FIGS. 1 and 2) is preferably set to 0.02 to 0.20 Ra.
[0017]
As described above, the surface treatment layers 10 and 10a for improving the lubricity of the mating surface are formed on the outer peripheral surface of the inner diameter side roller 8 and the inner peripheral surface of the outer diameter side roller 9. Since the surface roughness of the surface treatment layers 10 and 10a is set to 0.02 to 0.20 Ra, a good oil film can be formed on the sliding portion between the two peripheral surfaces. For this reason, even in the case of insufficient lubrication, in which sufficient lubricating oil cannot be sent between these two peripheral surfaces, the respective surface treatment layers 10, 10a strongly rub against each other by efficiently using a small amount of lubricating oil. It is possible to effectively prevent the surface treatment layers 10 and 10a from being significantly damaged or burned out. If the inner surface of the inner roller 8 and the outer surface of the outer roller 9 also have a surface roughness of 0.02 to 0.20 Ra, each of these surfaces and the support shaft 5 or Can form a good oil film on the sliding contact portion or the rolling contact portion with the outer peripheral surface of the cam 2.
[0018]
In order to sufficiently obtain the effects of the present invention, as described above, it is preferable to form the surface treatment layers 10 and 10a on the inner and outer diameter sides and on the surfaces of the rollers 8 and 9. However, as shown in FIGS. 5 and 6, the surface treatment layer 10 can be formed only on the surface of the inner roller 8. In this case, the surface roughness of the surface (at least the outer peripheral surface) of the surface treatment layer 10 is set to 0.02 to 0.20 Ra, and the outer diameter of the outer The surface roughness of the material (steel material such as bearing steel) constituting the side roller 9 is set to 0.02 to 0.20 Ra. Conversely, a surface treatment layer may be formed only on the surface of the outer diameter side roller 9 and the surface roughness of each peripheral surface may be set to 0.02 to 0.20 Ra.
[0019]
When the surface treatment layer is formed only on the surface of one of the rollers as described above, as shown in FIGS. 3 and 4, compared to the case where the surface treatment layers 10 and 10 a are formed on the surfaces of both rollers, After assembling the engine incorporating the cam follower device, the effect of preventing damage in a state immediately after the first start-up and before engine oil is fed into the roller installation portion of the cam follower device is still slightly inferior. However, as compared with the case where the surface treatment layer is not formed on any of the rollers, the effect of preventing the damage is remarkably excellent. For this reason, if the engine has a short time until the engine oil is fed into the roller installation portion after the initial startup, the engine can sufficiently be put to practical use.
[0020]
【Example】
Next, an experiment will be described in which the effect of the present invention is confirmed at the same time as performing the present invention. In this experiment, the surface roughness of the surface treatment layer 10 formed on the outer peripheral surface of the inner diameter side roller 8 and the surface roughness of the inner peripheral surface of the outer diameter side roller 9 in the structure shown in FIGS. The test was performed in order to know the effect of the sliding portion between the two peripheral surfaces on the durability. First, in the first experiment, the surface roughness of the surface treatment layer 10 formed on the outer peripheral surface of the inner diameter side roller 8 was maintained while the surface roughness of the inner peripheral surface of the outer diameter side roller 9 was kept at a constant value of 0.04 Ra. Was changed. In the second experiment, the surface roughness of the inner peripheral surface of the outer diameter roller 9 was maintained while the surface roughness of the surface treatment layer 10 formed on the outer peripheral surface of the inner diameter roller 8 was kept at a constant value of 0.04 Ra. Was changed. In the first and second experiments, the outer diameter side roller 9 was made of bearing steel (SUJ2), and the inner diameter side roller 8 was made of chrome steel (SCR440). Further, the surface treatment layer was not formed on the outer diameter side roller 9, and the surface treatment layer 10 was formed on the inner diameter side roller 8 by gas nitrocarburizing treatment. The outer diameter roller 9 had an outer diameter of 24 mm, and the inner diameter roller 8 had an inner diameter of 12 mm and a width of 14 mm.
[0021]
Under the following conditions, a durability test was performed in which the outer diameter side roller 9 was rotated at a high speed while applying a radial load under a slight amount of lubrication. The conditions of this endurance test are much more severe than those of actual use.
Test conditions Outer diameter side roller rotation speed: 1000 min ^-1
Test time: 500 hours Radial load: 5000N
Lubricating oil: Genuine diesel engine oil Lubricating method: Splashing lubricating oil temperature: 90 ° C
[0022]
FIG. 7 shows the results of such an endurance test. In FIG. 7, the mark “O” indicates that the sliding portion between the inner and outer rollers 8 and 9 did not suffer damage even after the lapse of a predetermined time, and no abnormal vibration occurred during operation. The symbol “x” indicates that the sliding portion was damaged before the lapse of a predetermined time and abnormal vibration occurred during operation. As is clear from FIG. 7 showing the results of such an experiment, the surface roughness of the surface treatment layer 10 formed on the inner peripheral surface of the outer diameter side roller 9 and the outer peripheral surface of the inner diameter side roller 8 is set to 0.02 to 0.02. If it is 0.20 Ra, sufficient durability can be obtained. Particularly, when the surface roughness of the inner peripheral surface of the outer diameter side roller 9 is set to 0.02 to 0.16 Ra, more excellent durability can be obtained. The effect is saturated even if the surface roughness of the surface treatment layer 10 formed on the inner peripheral surface of the outer diameter side roller 9 and the outer peripheral surface of the inner diameter side roller 8 is smaller than 0.02 Ra (more than that). In addition, the effect of improving the durability cannot be expected), and the cost required for smoothing the surface is unnecessarily increased. Therefore, the lower limit of the surface roughness of the surface treatment layer 10 or the material formed on the inner peripheral surface of the outer diameter side roller 9 and the outer peripheral surface of the inner diameter side roller 8 is set to 0.02 Ra.
[0023]
【The invention's effect】
Since the cam follower device of the present invention is configured and operates as described above, the sliding resistance between the outer peripheral surface of the inner roller and the inner peripheral surface of the outer roller is reduced even under poor lubrication. At the same time, it is possible to improve the durability by suppressing the wear of these two peripheral surfaces.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an example of a conventionally known cam follower device in a used state.
FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a partial cross-sectional view showing a first example of a conventional structure to which the present invention is applied.
FIG. 4 is a sectional view taken along line BB of FIG. 3;
FIG. 5 is a partial sectional view showing a second example of the conventional structure to which the present invention is applied.
FIG. 6 is a sectional view taken along line CC of FIG. 5;
FIG. 7 is a graph showing the results of a durability test performed to confirm the effects of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cam shaft 2 Cam 3 Rocker arm 4 Support wall part 5 Support shaft 6 Roller 7 Through hole 8 Inner diameter side roller 9 Outer diameter side roller 10, 10a Surface treatment layer

Claims (6)

A swing member that is provided opposite to a cam fixed to a cam shaft that rotates in synchronization with the crankshaft of the engine, and that swings and displaces in response to the movement of the cam, and supports the end portion of the swing member. A support shaft, an inner-diameter roller rotatably supported around the support shaft, and a rotatable support for the inner-diameter roller around the inner-diameter roller. An outer diameter roller to be in contact with the outer peripheral surface of the roller, and a surface treatment layer for improving lubricity with at least the inner peripheral surface of the outer diameter roller and the outer peripheral surface of the inner diameter roller. The surface roughness of each of these surface treatment layers is set to 0.02 to 0.20 Ra in the cam follower device. Omitting the surface treatment layer on one of the inner peripheral surface of the outer diameter side roller and the outer peripheral surface of the inner diameter side roller, the surface roughness of the material surface constituting the roller exposed on the peripheral surface of the roller The cam follower device according to claim 1, wherein is set to 0.02 to 0.20 Ra. 2. The cam follower device according to claim 1, wherein a surface treatment layer having a surface roughness of 0.02 to 0.20 Ra is also formed on the inner peripheral surface of the inner diameter side roller and the outer peripheral surface of the outer diameter side roller. The surface roughness of the surface treatment layer formed on the inner peripheral surface of the outer diameter side roller or the outer peripheral surface of the inner diameter side roller or the surface roughness of the material exposed on the inner peripheral surface of the outer diameter side roller was set to 0.02 to 0.16 Ra, The cam follower device according to claim 1 or 3. The cam follower device according to any one of claims 1 to 4, wherein the surface treatment layer is any one selected from the following (1) to (5).
{Circle around (1)} A reaction layer of a compound of sulfur and iron.
{Circle around (2)} A reaction layer containing nitrogen in the above [1].
(3) Reaction layer of a phosphate compound of phosphorus and iron.
{Circle around (4)} 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.
(5) A single or mixture of molybdenum disulfide and polytetrafluoroethylene is fired together with a thermosetting synthetic resin on the surface of any one of the reaction layers (1) to (3) above. Of processed layers to be overlapped. The surface treatment layer is one which has been subjected to any one of the following treatments selected from the following (6) to (8) to have a surface hardness of Hv650 or more and a thickness of the treatment layer of 15 μm or more. A cam follower device according to any one of claims 1 to 4.
(6) Salt bath nitriding treatment.
(7) Gas nitrocarburizing treatment.
(8) Ion nitrocarburizing treatment.

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