JP2020051258A - Oscillating rotary cam lifter, and ohv engine - Google Patents

Abstract

To provide an oscillating rotary cam lifter preventing abrasion even if lubricating action is insufficient, and an OHV engine comprising the oscillating rotary cam lifter.SOLUTION: An oscillating rotary cam lifter 1 is a type of an oscillating rotary cam lifter slidably contacting with the timing cam of the overhead valve engine, and includes, on the sliding surface 1a with the timing cam, a sliding layer 2 formed on a metal base. The sliding layer 2 includes a fluorine resin layer having a fluorine resin on its surface. The fluorine resin layer is a crosslinked fluorine resin layer in which at least vicinity of the surface is crosslinked, and an average crosslink rate is 9 to 25% in a range from the outermost surface to a depth of 5 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oscillating rotary cam lifter slidably contacting a timing cam in an overhead valve (OHV) engine. The present invention also relates to an OHV engine using the cam lifter.

  For general-purpose engines such as generators, pumps, and brush cutters, lightweight, compact OHV engines having a simple structure and easy maintenance are used. In particular, in a small-sized OHV engine such as a brush cutter, an OHV engine provided with an oscillating rotary cam lifter that can be further reduced in weight and size is used.

  The above-mentioned OHV engine has an intake / exhaust valve located above the combustion chamber, a timing cam located near the crankshaft and rotated by the transmission of rotational power from the crankshaft, and a swing cam that slides on the timing cam. It includes a dynamic rotary cam lifter, and a push rod connecting the cam lifter and each of the intake and exhaust valves. In this configuration, the rotation of the timing cam causes the swinging rotary cam lifter slidingly in contact with the timing cam to swing and rotate, and the opening / closing power accompanying the swinging rotation of the cam lifter is transmitted to the intake / exhaust valves via the push rod, and the respective timings are changed. Open / close the valve.

  Conventionally, as an OHV engine provided with the above-mentioned swinging rotary cam lifter, an intake / exhaust valve can be operated by a cam lifter and a single cam, and furthermore, a valve train of an engine in which play of an articulated portion of a component is eliminated. Device (see Patent Document 1), or a valve drive device for a portable work machine that can use a cam lifter and a single cam to make the opening speeds of the intake and exhaust valves different for the purpose (see Patent Document 2). ) Are disclosed. In addition, a direct lever type overhead valve device having a similar configuration is disclosed (see Patent Document 3). In these conventional OHV engine valve drive devices, the oscillating rotary cam lifter (including its equivalent) is made of metal and is in sliding contact with a metal timing cam.

  As a lubrication method for the above-mentioned sliding contact portion in the OHV engine, a droplet lubrication that scrapes up oil stored in an oil pan with a scraper provided on a rotating shaft of a crankshaft and fills the inside of a crank and a valve rocker chamber with mist-like oil. And a forced lubrication method in which oil is supplied by pressure to the sliding portion by an oil pump. Further, by having an intake passage extending from the carburetor to the intake valve of the cylinder head and a passage having a check valve branched from the bottom of the intake passage, a mixed gas of mixed fuel (oil and gasoline) and air is provided. There is a type in which oil flows into a valve operating mechanism, and oil contained in the mixed gas adheres to a cylinder, a piston, a timing cam, a cam lifter, and the like to lubricate (see Patent Document 4).

JP-A-51-123416 JP-A-4-209905 Japanese Patent Publication No. 2003-522891 JP-A-11-223117

  However, in the conventional OHV engine using the oscillating rotary cam lifter, abrasion of the sliding portion may occur in a state where the oil is not sufficiently supplied and the lubrication action is insufficient, such as at the time of the initial operation of the engine. In particular, the sliding portion between the metal cam lifter and the timing cam is significantly worn.

  The present invention has been made in view of such circumstances, and provides an oscillating rotary cam lifter capable of suppressing wear even when lubrication is insufficient, and an OHV engine provided with the oscillating rotary cam lifter. The purpose is to:

  An oscillating rotary cam lifter according to the present invention is an oscillating rotary cam lifter that is slidably contacted with a timing cam of an OHV engine, and the cam lifter is formed on a metal base on a sliding contact surface with the timing cam. The sliding layer has a fluororesin layer containing a fluororesin on the surface, and the fluororesin layer is a crosslinked fluororesin layer in which at least the surface vicinity is crosslinked, from the outermost surface. The average cross-linking rate up to a depth of 5 μm is 9 to 25%.

  The sliding layer has a base layer including a heat-resistant resin and a first fluororesin formed on the surface of the metal base, and a second fluorine including a second fluororesin formed on the base layer surface. A resin layer, wherein the heat-resistant resin is a resin containing at least one atom of an oxygen atom, a nitrogen atom, and a sulfur atom in at least a main chain of a polymer structure together with a carbon atom; Is the crosslinked fluororesin layer.

  The heat-resistant resin is a polyamideimide (PAI) resin or a polyethersulfone (PES) resin.

  The thickness of the crosslinked fluororesin layer is 5 to 20 μm.

  The fluorine resin contained in the crosslinked fluorine resin layer is a polytetrafluoroethylene (PTFE) resin.

  An OHV engine according to the present invention includes an oscillating rotary cam lifter slidably contacting a timing cam and oscillating on an axis parallel to a camshaft, wherein the oscillating rotary cam lifter according to the present invention is used. It is characterized by being.

  The swing rotary cam lifter of the present invention has a sliding layer on the sliding contact surface with the timing cam, and since the sliding layer has a cross-linked fluororesin layer in which at least the surface is cross-linked at least on its surface, Even in a state of insufficient lubrication, the friction torque between the cam lifter and the timing cam does not increase, and wear due to friction of the cam lifter can be suppressed. In particular, the cross-linked fluororesin layer has an average cross-linking rate of 9 to 25% from the outermost surface to a depth of 5 μm, so that the abrasion resistance effect by cross-linking can be suitably exerted while suppressing peeling of the coating due to excessive cross-linking. be able to. As a result, long-term low friction characteristics can be maintained.

  The sliding layer is composed of an underlayer containing a heat-resistant resin and a first fluororesin formed on the surface of the metal substrate and a crosslinked fluororesin layer formed on the surface of the underlayer. Excellent adhesion to substrate. In particular, since a PAI resin or a PES resin is used as the heat-resistant resin, it is more excellent in heat resistance and adhesion to a metal substrate, and can be used for an engine which is subjected to a high-temperature atmosphere.

  The OHV engine of the present invention includes a swing rotary cam lifter that slides on a timing cam and swings on an axis parallel to the camshaft. Since the swing rotary cam lifter is the cam lifter of the present invention, The timing cam and the cam lifter can be prevented from seizing even in a state of poor lubrication conditions such as at the time of initial movement, which can contribute to a longer life.

FIG. 2 is a perspective view of the swing rotary cam lifter of the present invention. It is sectional drawing of the sliding contact surface of a cam lifter. It is sectional drawing (one side) of the valve drive part part of the OHV engine of this invention. It is sectional drawing (other side surface) of the valve drive device part of the OHV engine of this invention. It is an enlarged view of an NMR chart of a crosslinked PTFE resin or the like.

  A swing rotary cam lifter according to the present invention will be described with reference to FIG. FIG. 1 is a perspective view of an oscillating rotary cam lifter. As shown in FIG. 1, the swing rotary cam lifter 1 of the present invention has a sliding layer 2 on a sliding contact surface 1a with a timing cam 6 (see FIG. 3). The sliding layer 2 may be formed on at least the sliding contact surface 1 a of the cam lifter 1, and may be formed on the entire surface of the cam lifter 1. Further, the cam lifter main body is made of a metal base material, and may be made of a molten metal or a sintered metal. Sintered metal is more preferred because it is easy to manufacture and advantageous in binding to the sliding layer. Examples of the sintered metal that can be used include an iron-based sintered metal, a copper-based sintered metal, and an iron-copper-based sintered alloy.

  FIG. 2 shows a cross-sectional view of the sliding surface of the cam lifter. In FIG. 2, the sliding layer 2 includes an underlayer 3 formed on the surface of a metal substrate 5 and a crosslinked fluororesin layer 4 formed on the surface of the underlayer 3. At least the vicinity of the surface of the fluororesin contained in the crosslinked fluororesin layer 4 is crosslinked, and the average crosslink rate from the outermost surface to a depth of 5 μm is 9 to 25%. In this case, the crosslinked fluororesin layer can be an inclined layer in which the crosslink rate of the fluororesin decreases from the surface toward the interface with the underlayer.

  The surface of the metal substrate 5 shown in FIG. 2 on the side of the underlayer 3 is roughened by the surface roughening treatment. As the surface roughening treatment, a mechanical surface roughening method such as a shot blast method, an electric surface roughening method such as a glow discharge or a plasma discharge treatment, and a chemical surface roughening method such as an alkali treatment can be employed. By roughening the surface of the metal substrate, the sliding layer can be firmly adhered to the metal substrate by the anchor effect.

  The underlayer 3 is a mixture layer containing a heat-resistant resin and a first fluororesin, and improves the adhesion between the metal substrate 5 and the crosslinked fluororesin layer 4. The crosslinking of the first fluororesin contained in the base layer 3 is not particularly limited. For example, a structure in which only the first fluororesin present near the boundary surface may be crosslinked.

The heat-resistant resin is a resin containing at least one atom of an oxygen atom, a nitrogen atom and a sulfur atom together with a carbon atom in at least a main chain of a polymer structure. In addition, it is a resin that does not thermally decompose when firing the underlayer and the upper layer film. Here, “not thermally decomposed” means a resin that does not start thermal decomposition within the temperature and time for baking the underlayer and the upper layer film. Further, the heat-resistant resin is preferably a resin having a functional group having excellent adhesion to a metal substrate and a functional group which also reacts with the first fluororesin, in the molecular main chain or at the molecular end.
Examples of the heat-resistant resin include an epoxy resin, a polyester resin, a PAI resin, a polyimide (PI) resin, a polyetherimide resin, a polyimidazole resin, a PES resin, a polysulfone resin, a polyetheretherketone (PEEK) resin, and a silicone resin. Can be In addition, a urethane resin or an acrylic resin that prevents shrinkage of the fluororesin during the formation of the coating film can be used in combination.

Cam lifters are used under high temperature conditions inside the engine. For this reason, as the above-mentioned heat-resistant resin, any heat-resistant resin can be used as long as it has heat resistance that does not cause thermal deterioration during use and can be firmly adhered to the metal substrate. Further, since the cam lifter is used in an environment in which it comes into contact with a lubricant containing an additive, it is preferable that the cam lifter be a resin having oil resistance to these lubricants. Among the above-mentioned heat-resistant resins, it is preferable to use a PAI resin or a PES resin because they are excellent in heat resistance, abrasion resistance and binding property with a metal base material as a base. These are also excellent in oil resistance and are not easily swelled and dissolved by lubricating oil during use.
Among the PAI resins, an aromatic PAI resin in which an imide bond and an amide bond are bonded via an aromatic group is preferable. When the resin is an aromatic PAI resin, it has excellent binding properties to the underlying metal substrate, and the obtained coating film has particularly excellent heat resistance.

  The first fluororesin can be used as long as it is a resin that can be dispersed in a particle form in an aqueous coating solution for forming an underlayer. Examples of the first fluororesin include PTFE particles, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (hereinafter, referred to as PFA) particles, tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter, referred to as FEP) particles, Alternatively, two or more of these can be preferably used.

  In addition to the heat-resistant resin and the first fluororesin, non-ionic surfactants such as polyoxyethylene alkyl ether, inorganic pigments such as carbon black, and N-methyl-2-pyrrolidone Aprotic polar solvent arbitrarily mixed with water, and water as a main solvent. Further, an antifoaming agent, a desiccant, a thickener, a leveling agent, an anti-cissing agent and the like can be added. Examples of the water-based coating liquid for forming the undercoat layer include primer paints EK series and ED series manufactured by Daikin Industries, Ltd.

  The crosslinked fluororesin layer is a layer of the crosslinked fluororesin formed on the surface of the underlayer, in which the molecular chains of the fluororesin undergo a crosslink reaction by radiation. The first fluororesin and the second fluororesin may be the same or different, but it is preferable to use the same fluororesin. Examples of the second fluororesin include PTFE, PFA, FEP, ethylene / tetrafluoroethylene copolymer (ETFE) and the like. These resins can be used alone or as a mixture. Among these, PTFE having excellent heat resistance and slidability is preferable.

  The crosslinked fluororesin layer is obtained by applying and drying an aqueous dispersion in which PTFE resin particles are dispersed. As the aqueous dispersion in which the PTFE resin particles are dispersed, for example, polyflon = PTFE enamel manufactured by Daikin Industries, Ltd. can be mentioned.

  The layer thickness of the crosslinked fluororesin layer is in the range of 2.5 to 20 μm, preferably 5 to 20 μm, more preferably 5 to 15 μm. If the thickness is less than 2.5 μm, the underlying layer may be exposed due to peeling or initial wear due to poor adhesion of the coating. In particular, when the layer thickness is in the range of 5 to 20 μm, exposure of the underlayer due to initial wear can be suitably prevented.

  The layer thickness of the underlayer is in the range of 2.5 to 20 μm, preferably 5 to 20 μm, more preferably 5 to 15 μm. If it is less than 2.5 μm, the metal substrate may be exposed due to peeling or initial wear due to poor adhesion of the coating. If it exceeds 20 μm, cracks may occur during the formation of the coating, or the coating may peel off during operation to deteriorate the lubrication state. When the layer thickness is in the range of 2.5 to 20 μm, exposure of the metal substrate due to initial wear can be prevented, and peeling during operation can be prevented for a long period of time.

  As described above, the thickness of the sliding layer is 5 μm or more and less than 40 μm, and preferably 15 to 30 μm. If the layer thickness is less than 5 μm, the metal substrate may be exposed due to peeling or initial abrasion due to poor adhesion of the coating. When the thickness is 40 μm or more, cracks may occur during the formation of the coating, or the coating may peel off during operation to deteriorate the lubrication state. By setting the thickness of the sliding layer in the range of 5 μm or more and less than 40 μm, exposure of the metal base material due to initial wear can be prevented, and peeling during operation can be prevented for a long time.

The method for forming the sliding layer on the surface of the metal substrate will be described below.
(1) Surface treatment of metal base material The metal base material is adjusted in advance to have a surface roughness (Ra) of 1.0 to 2.0 μm using a shot blast or the like before forming a sliding layer, Then, it is preferable to immerse in an organic solvent such as petroleum benzine and perform ultrasonic degreasing for about 5 minutes to 1 hour.
(2) Coating of an aqueous coating solution for forming an underlayer Before application of an aqueous coating solution for forming an underlayer, in order to improve the dispersibility of the aqueous dispersion, it is rotated at, for example, 40 rpm for 1 hour using a ball mill mount. And redisperse. The redispersed aqueous coating solution is filtered using a 100-mesh wire net and applied by a spray method.
(3) Drying of the aqueous coating liquid for forming the underlayer The aqueous coating liquid is dried after being applied. As the drying condition, for example, drying in a constant temperature bath at 90 ° C. for about 30 minutes is preferable.

(4) Coating of aqueous coating liquid for forming the second fluororesin layer Before the aqueous coating liquid for forming the second fluororesin layer, in order to improve the dispersibility of the aqueous dispersion, using a ball mill mount, For example, it is rotated at 40 rpm for 1 hour and redispersed. The redispersed aqueous coating liquid is filtered using a 100-mesh wire net, and coated using a spray method.
(5) Drying of aqueous coating liquid for forming second fluororesin layer The aqueous coating liquid is applied and dried. As the drying condition, for example, drying in a constant temperature bath at 90 ° C. for about 30 minutes is preferable.
As a method for coating the undercoat layer and the second fluororesin layer, any method can be used as long as a film can be formed, such as a dipping method or a brush coating method, in addition to the spray method. The spraying method is preferred in view of making the surface roughness and coating shape of the coating as small as possible and considering the uniformity of the layer thickness.

(6) Firing After the second fluororesin layer is dried, it is fired in a heating furnace in air in the range of (melting point (Tm) + 30 ° C.) to (melting point (Tm) + 100 ° C.) for 5 to 40 minutes. When the first and second fluororesins are PTFE, firing is preferably performed in a heating furnace at 380 ° C. for 30 minutes.

(7) Irradiation of electron beam on the second fluororesin layer The irradiated film is irradiated with radiation to crosslink the second fluororesin layer. The radiation includes α-rays (particle beams of helium-4 nuclei emitted from radionuclides that perform α-decay), β-rays (negative electrons and positrons emitted from nuclei), and electron beams (almost constant kinetic energy. Particle beam such as electron beam having; generally, thermal electrons are accelerated in vacuum); gamma rays (emission and absorption due to transition between energy levels of nuclei and elementary particles, pair annihilation and pair generation of elementary particles) Ionizing radiation such as a short wavelength electromagnetic wave). Among these radiations, from the viewpoint of crosslinking efficiency and operability, an electron beam and a γ-ray are preferable, and an electron beam is more preferable. In particular, an electron beam has advantages such as easy availability of an electron beam irradiation apparatus, simple irradiation operation, and a continuous irradiation step.

  The crosslinked fluororesin layer only needs to be crosslinked at least in the vicinity of the surface. Preferably, the average crosslinking ratio from the outermost surface of the crosslinked fluororesin layer to a depth of 5 μm is 9 to 25%. When the average crosslinking rate is 9% or more, the wear resistance effect by crosslinking is easily obtained, and the exposure of the underlayer can be further prevented. Further, by setting the average crosslinking rate to 25% or less, damage such as peeling of the coating film due to excessive crosslinking can be suppressed. In addition, the time required for electron beam irradiation does not become too long, and mass productivity can be maintained. Regarding the irradiation conditions, it is preferable to irradiate radiation at an irradiation temperature, an irradiation dose, and an accelerating voltage such that the average cross-linking ratio is in the range of 9 to 25%.

  FIG. 2 illustrates a two-layer structure in which the sliding layer includes an underlayer and a crosslinked fluororesin layer. However, the present invention is not limited to this. For example, the sliding layer may have a single-layer structure including only a crosslinked fluororesin layer. Good. Even in this case, it is preferable that the average crosslink rate from the outermost surface of the crosslinked fluororesin layer to a depth of 5 μm is 9 to 25%.

  An example of an OHV engine provided with the swing rotary cam lifter of the present invention will be described with reference to FIGS. As shown in FIGS. 3 and 4, the valve driving device of the OHV engine includes one timing cam 6 and a pair of swing rotary cam lifters 1 abutting on the timing cam 6. The pair of swing rotary cam lifters 1 are both configured to rotate around the cam lifter shaft 1b. The timing cam 6 and the timing gear 7 are rotatably supported coaxially by a camshaft. This camshaft and the shaft of the cam lifter shaft 1b are parallel. The timing gear 7 of the timing cam 6 is formed so as to mesh with the crank gear 8b of the crank 8. One swing rotary cam lifter 1 is connected to a push rod 9 for an exhaust valve, and the other swing rotary cam lifter 1 is connected to a push rod 9 for an intake valve. Reference numeral 10 denotes an intake passage.

  The use state of the valve drive device of the OHV engine will be described. By rotating the crankshaft 8a of the crank 8, the timing gear 7 meshing with the crank gear 8b is rotated. Thereby, the timing cam 6 is rotated, and one of the pair of swinging rotary cam lifters 1 abutting on the timing cam 6 is rotated about the lifter shaft 1b, and the exhaust valve is pushed through the push rod 9 for the exhaust valve. Open. Next, when the timing cam 6 is further rotated, the other swingable rotary cam lifter 1 that comes into contact with the timing cam 6 rotates about the lifter shaft 1b, via the push rod 9 for the intake valve. Open the intake valve. The operation of the valve is completed by closing the exhaust valve at a predetermined time and closing the intake valve. In this configuration, the pair of swing rotary cam lifters 1 is rotated by one timing cam 6, so that the length of the timing cam 6 in the axial direction is reduced. Lightweight.

  Any conventional lubrication system can be used as the lubrication system in the OHV engine of the present invention. In the present invention, in the swing rotary type cam lifter 1, the above-mentioned sliding layer 2 is formed on the sliding contact portion 1a with the timing cam 6, so that no matter which type of lubrication is employed, the wear in the sliding contact portion is reduced. Can be prevented.

  In the OHV engine of the present invention, the timing cam 6 may be a molded body of a synthetic resin. If the timing cam 6 is made of a synthetic resin, the wear of the sliding layer can be further suppressed, and the weight can be further reduced, so that the timing cam 6 is suitable for a portable OHV engine such as a brush cutter.

  Examples of the synthetic resin forming the timing cam 6 include polyphenylene sulfide resin, PEEK resin, PI resin, polyamide resin, wholly aromatic polyester resin, and the like. When the timing cam 6 is made of the synthetic resin, it is preferable that the timing cam and the timing gear are integrally formed. In this case, the weight can be further reduced.

(1) Preparation of test piece Test piece: A sliding layer was formed on the sliding surface of a cam lifter made of an iron-based sintered alloy. The surface roughness of the base material on the sliding surface was adjusted to 1.5 μmRa using shot blast, and then immersed in petroleum benzine and subjected to ultrasonic degreasing for about 5 minutes. For the base layer and the second fluororesin layer, a primer paint (model number: EK-1909S21R) manufactured by Daikin Co., Ltd. and a top paint (model number: EK-3700C21R) manufactured by Daikin Co., Ltd. are used for the second fluororesin layer. Films were formed so that the thickness of each layer was 10 μm. Each paint was applied by the spray method described above. The drying time was 30 minutes in a thermostat at 90 ° C., and baked in a heating furnace at 380 ° C. for 30 minutes.
The test piece on which the sliding layer was formed was placed on a heating plate of an electron beam irradiation device, and electron beam irradiation was performed from the sliding layer side under the following conditions. A plurality of test pieces were obtained by changing the irradiation dose of the irradiation conditions.
Apparatus used: Hamamatsu Photonics EB engine Irradiation conditions: Acceleration voltage 70 kV
Temperature 340 ° C
Atmosphere in chamber during irradiation Heated nitrogen (oxygen concentration 1000ppm or less)

(2) Calculation of Crosslinking Rate The second fluororesin layer of each test piece was scraped from the outermost surface to a depth of 5 μm, and the cut sample was used as a measurement sample. From the results of NMR measurement of each measurement sample, the average crosslinking ratio from the outermost surface (depth 0 μm) to the depth 5 μm was calculated as the crosslinking ratio.
The crosslink rate was measured and calculated by ¹⁹ F Magic angle Spinning (MAS) nuclear magnetic resonance (NMR) method (High speed magic angle nuclear magnetic resonance). References (Beat Fuchs and Ulrich Scheller., Branching and Cross-Linking in Radiation-Modified Poly (tetrafluoroethylene)): A. Solid-State NMR, 1989. The underlined F atoms described below can be assigned.
A: -70ppm: = CF-C F 3
_{B: -82ppm: -CF 2 -C F} 3
C: -186ppm: ≡C F

Here, FIG. 5 (a) shows the NMR spectrum of uncrosslinked PTFE which has not been irradiated with an electron beam, and FIG. 5 (b) shows the NMR spectrum of crosslinked PTFE which has been irradiated with 1000 kGy. As shown in FIG. 5, it can be seen that the intensity of the signal B increases by irradiating the electron beam, and the signals A and C appear.
Assuming that the area ratios of the signals A to C are S _A , S _B , and S _C , respectively, the crosslinking ratio can be calculated by the following equation.

The above formula is of the three molecular chains extending from each of the carbon atoms of the structure of all ≡CF, not in cross-linked structure = CF-CF ₃ and = CF- (CF ₂₎ the molecular chains of the m-CF ₃ subtracted, a _{= CF- (CF 2) n-} CF = proportion of a crosslinked chain is calculated as a cross-linking rate. Note that m and n are arbitrary integers. By comparing FIG. 5 and the above equation, it can be seen that irradiation with an electron beam increases the crosslinking ratio.

(3) Abrasion test The test piece obtained in the above (1) (Examples 1 to 3 and Comparative Examples 2 to 3), the test piece in which the second fluororesin layer is not crosslinked (Comparative Example 1), and shot blast A cam (metal) having a diameter of 35 mm, an eccentricity of 3.5 mm, and a thickness of 6.5 mm was brought into contact with a test piece (Comparative Example 4) on which the treatment and the formation of the sliding layer were not performed at a load of 3 kgf and 3000 rpm And rotated for 120 minutes under non-lubricated conditions. After 120 minutes, the sliding surface between the cam lifter and the cam was visually observed. The results are also shown in Table 1.

  As shown in Table 1, in Examples 1 to 3 in which a crosslinked fluororesin layer having an average crosslinkage of 9 to 25% was formed on the sliding surface of the cam lifter with the cam, the cam lifter was rotated and slid for 120 minutes under non-lubricated conditions. And the wear of the sliding surface of the cam was slight. On the other hand, in Comparative Example 2 in which the average crosslinking ratio was less than 9%, the effect of crosslinking was not exhibited, and the amount of wear was large. In Comparative Example 1, which was not crosslinked, the amount of wear was large. On the other hand, when the average crosslinking ratio exceeded 25%, the coating became brittle due to crosslinking, and peeling occurred. Comparative Example 4 resulted in large wear because of metal contact.

  INDUSTRIAL APPLICABILITY The swing rotary cam lifter of the present invention can be used for a generator, a pump, a brush cutter, and the like because frictional torque between the cam lifter and the timing cam does not increase and wear due to friction of the cam lifter can be suppressed even when lubrication is insufficient. It can be suitably used as a swinging rotary cam lifter of a lightweight and compact OHV engine.

DESCRIPTION OF SYMBOLS 1 Oscillating rotary cam lifter 2 Sliding layer 3 Underlayer 4 Crosslinked fluororesin layer 5 Metal substrate 6 Timing cam 7 Timing gear 8 Crank 9 Push rod 10 Intake passage

Claims (6)

An oscillating rotary cam lifter slidably contacted with a timing cam of an overhead valve engine, the cam lifter having a sliding layer formed on a metal base material on a sliding contact surface with the timing cam,
The sliding layer has a fluororesin layer containing a fluororesin on the surface,
An oscillating rotary cam lifter, wherein the fluororesin layer is a crosslinked fluororesin layer in which at least the vicinity of the surface is crosslinked, and the average crosslink rate from the outermost surface to a depth of 5 μm is 9 to 25%. The sliding layer includes a base layer including a heat-resistant resin and a first fluororesin formed on the surface of the metal base, and a second fluorine including a second fluororesin formed on the base layer surface. Consisting of a resin layer,
The heat-resistant resin is a resin containing at least one atom of an oxygen atom, a nitrogen atom, and a sulfur atom in at least a main chain of a polymer structure, together with a carbon atom,
The swing rotary cam lifter according to claim 1, wherein the second fluororesin layer is the crosslinked fluororesin layer.   3. The swing rotary cam lifter according to claim 2, wherein the heat-resistant resin is a polyamideimide resin or a polyether sulfone resin.   The swing rotary cam lifter according to any one of claims 1 to 3, wherein a thickness of the crosslinked fluororesin layer is 5 to 20 m.   The swing rotary cam lifter according to any one of claims 1 to 4, wherein the fluororesin contained in the crosslinked fluororesin layer is a polytetrafluoroethylene resin. An overhead valve engine including a swing rotary cam lifter that slides on a timing cam and swings on an axis parallel to a cam shaft,
6. An overhead valve engine, wherein the swing rotary cam lifter is the swing rotary cam lifter according to any one of claims 1 to 5.

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