JP2012031780A - Cam lifter for opening and closings valve of ohv engine, and the ohv engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make up a valve gear mechanism of an OHV engine from a cam lifter with which noise reduction effects can be recognized or an OHV engine employing the cam lifter, wherein wear can be suppressed even if the cam lifter suffers from insufficient lubricating action.SOLUTION: Cam lifters 3 and 4 are brought into slide contact with a timing cam 2 of the valve gear mechanism 1 of the OHV engine A to cause them to swing. A push rod 5 is axially advanced/retreated while linking with the swing. The cam lifter of the OHV engine transmits the advance/retreat action to rocker arms 7 and 8 to open/close an engine valve. A slide contact surface with the timing cam 2 is formed of a smooth slide contact surface made of a heat resistant synthetic resin mold 10.

Description

  The present invention relates to a cam lifter that is used in an Over Head Valve (OHV) engine and is in sliding contact with a timing cam, and further relates to an OHV engine using the cam lifter.

  In general, general-purpose engines such as a generator, a pump, and a brush cutter have a simple structure and are easy to maintain, and a lightweight and compact OHV engine is used. In particular, in a small OHV engine such as a brush cutter, an OHV engine provided with a rocking and rotating cam lifter that can be further reduced in weight and size is used.

  The above OHV engine includes an intake / exhaust valve located above the combustion chamber, a timing cam that is located near the crankshaft and that is rotated by transmission of rotational power from the crankshaft, and a rocker that is in sliding contact with the timing cam. A dynamic rotation type cam lifter and a push rod connecting the cam lifter and intake / exhaust valves are provided.

  In this configuration, by the rotation of the timing cam, the oscillating rotation type cam lifter slidingly contacting the oscillating rotation is oscillated, and the opening / closing power accompanying the oscillating rotation of the cam lifter is transmitted to the intake / exhaust valves via the push rod. Open and close the valve.

  Conventionally, as an OHV engine equipped with the above-described oscillating rotation type cam lifter, the valve of the engine in which the intake / exhaust valve can be operated by the cam lifter and the single cam and the backlash of the connecting portion of the constituent members is eliminated. Device (see Patent Document 1), or a valve drive device for a portable work machine that uses a cam lifter and a single cam to make the valve opening speeds of intake and exhaust valves different in purpose (see Patent Document 2) ) Etc. 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 swing-rotating cam lifter (including the corresponding one) is made of metal and is in sliding contact with the metal timing cam.

  As a lubrication method for the sliding contact part etc. in the OHV engine, the oil stored in the oil pan is scraped up by a scraper provided on the rotating shaft of the crankshaft, and the inside of the crank and the valve rocker chamber are filled with mist oil. There are a system and a forced lubrication system that supplies oil to the sliding contact portion by an oil pump. Further, by having an intake passage from the carburetor to the intake valve of the cylinder head and a passage provided with a check valve branched from the bottom surface of the intake passage, mixed fuel (oil and gasoline) and air There is a type in which a mixed gas 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 or the like and is lubricated (see Patent Document 4).

JP 51-123416 A Japanese Patent Laid-Open No. 4-209905 Japanese translation of PCT publication No. 2003-522891 JP-A-11-223117

  However, in the above-described conventional OHV engine using the swing-rotating cam lifter, wear of the sliding portion may occur in a state where the lubrication action is not sufficient when oil is not sufficiently supplied, such as when the engine is first started. There is a problem that there is. In particular, the wear of the sliding contact portion between the metal cam lifter and the timing cam may be significant.

  Further, there is a problem that noise may be generated due to contact between the metal cam lifter and the timing cam.

  Accordingly, an object of the present invention is to solve the above-described problems, and the cam lifter in the valve mechanism of the OHV engine can suppress wear even when the lubrication action is insufficient. Or it is to make it an OHV engine using this.

  In order to solve the above-described problems, in the present invention, the cam lifter is slidably contacted with the timing cam in the valve mechanism of the OHV engine, and the push rod is interlocked with the swing to advance and retract in the axial direction. In an OHV engine cam lifter that transmits and retreats the advancing and retreating operation to the rocker arm to open and close the engine valve, the sliding contact surface with the timing cam is a smooth sliding contact surface made of a heat-resistant synthetic resin molding. This is a cam lifter for opening and closing the valve of the OHV engine.

  The cam lifter for valve opening / closing of the OHV engine of the present invention configured as described above is a composite in which a molded body of heat-resistant synthetic resin that can withstand the high temperature of the engine is joined to the timing cam sliding surface of the cam lifter body, Due to the lubrication characteristics of the smooth sliding contact surface made of a synthetic resin molding, the friction torque between the cam lifter and the timing cam does not increase even when the engine does not have enough lubricating oil at the initial operation, and the cam lifter wears due to friction. Can be suppressed. In addition, there is also a silencing effect in sound caused by contact with the timing cam.

When a synthetic resin molded body is an injection molded body, the sliding contact surface is smooth, low cost, and easy to manufacture.
The cam lifter is composed of a composite body in which the cam lifter body and a heat-resistant synthetic resin molded body are integrated. For example, the cam lifter is integrated by inserting the cam lifter body into a molding die and molding it. The synthetic resin molded body is excellent in bondability, adhesion, and bondability with the cam lifter body.

  In the cam lifter, the contact area between the cam lifter main body and the heat-resistant synthetic resin molded body is increased by providing a concave portion or a convex portion. For this reason, the heat-resistant synthetic resin molded body constituting the sliding contact surface with the timing cam is not peeled off from the cam lifter main body even in a change in atmospheric temperature or in use in contact with engine oil, and the durability is good.

  If the cam lifter body is made of metal or ceramics, particularly excellent strength can be secured. In addition, if the cam lifter body is a sintered body, it can be molded with a mold, so that it can be manufactured easily and has excellent bonding properties, adhesion, and bonding properties with a synthetic resin molded body. If the sintered body is an Al-based sintered metal or an Fe-based sintered metal, it is advantageous for cost reduction.

  If the above heat-resistant synthetic resin molding is made of engineering plastics, it will be excellent in heat resistance, suitable for use in engines with a high temperature atmosphere, and excellent in low friction characteristics and oil resistance. It becomes a thing.

  When the heat-resistant synthetic resin molding contains a solid lubricant and has lubricity, the low friction characteristics are further improved. In particular, by using a calcined powder of PTFE resin, the molded article of the synthetic resin is excellent in self-lubricity, heat resistance, and wear resistance.

If the said heat resistant synthetic resin molded object contains a fibrous reinforcement, the abrasion resistance and mechanical strength of a synthetic resin molded object will improve. In this way, since the compressive strength is particularly increased, no dent is generated on the timing cam sliding contact surface. When the fibrous reinforcing material is carbon fiber, friction characteristics are improved in addition to improvement of wear resistance and mechanical strength.
If the synthetic resin is a polyetheretherketone resin (hereinafter abbreviated as PEEK), it becomes a cam lifter for opening and closing a valve of an OHV engine particularly preferable for various required characteristics as described above.

  Further, in order to solve the above-mentioned problems, the cam lifter is slidably brought into contact with the timing cam in the valve mechanism of the OHV engine, and the push rod is interlocked with the swing to advance and retract in the axial direction. In the OHV engine in which the cam lifter is opened / closed by transmitting to the rocker arm, the cam lifter can be any one of the cam lifters described above.

  The OHV engine according to the present invention configured as described above includes a swing-rotating cam lifter that is slidably contacted with a timing cam and swings on an axis parallel to the camshaft. By using the cam lifter according to the present invention described above, the timing cam and the cam lifter are prevented from seizing even in a poor lubrication condition such as at the time of initial movement, thereby extending the life.

  In the case where the timing cam is a synthetic resin molded body, the sliding contact with the oscillating and rotating cam lifter is reduced in friction and further reduced in weight. In particular, by integrally molding this timing cam with the timing gear, the weight can be further reduced. If the synthetic resin forming the timing cam contains carbon fiber or aramid fiber, wear resistance, It becomes an OHV engine having a longer life due to an improvement in mechanical strength.

  The cam lifter for valve opening / closing of the OHV engine according to the present invention is such that the sliding surface with the timing cam is a smooth sliding surface made of a heat-resistant synthetic resin molding, so that the cam lifter is in a state of insufficient lubrication. As a result, the wear can be suppressed, and further, there is an advantage that the cam lifter has a silencing effect.

  In addition, the cam lifter for opening and closing the valve of the OHV engine in which the contact area between the cam lifter body and the heat-resistant synthetic resin molded body is provided with a concave or convex portion to increase the contact area, in addition to the above-described advantages, Even when in use in contact with engine oil, the heat-resistant synthetic resin molding constituting the sliding contact surface with the timing cam is advantageous in that it does not peel off from the cam lifter body and has good durability.

  Further, in the OHV engine according to the present invention, since the cam lifter is the cam lifter according to the present invention described above, the timing cam and the cam lifter are not worn even when the lubrication conditions are poor such as at the time of initial movement, and are seized. This also has the advantage that the service life is prolonged and the sound deadening effect is recognized.

Sectional drawing of OHV engine of embodiment Explanatory drawing of the operating state of the valve mechanism of the OHV engine of embodiment Sectional view taken along line III-III in FIG. The front view which expands and shows the cam lifter of an embodiment The front view which expands and shows the principal part of the cam lifter main body of embodiment

An embodiment of an OHV engine valve opening / closing cam lifter and an OHV engine having the same according to the present invention will be described below with reference to the accompanying drawings.
As shown in FIGS. 1 to 4, the valve open / close cam lifter of the OHV engine is swung by sliding the cam lifters 3 and 4 against the timing cam 2 in the well-known valve operating mechanism 1 of the OHV engine A. This is a cam lifter for an OHV engine that interlocks the push rods 5 and 6 to advance and retract in the axial direction and transmits the advance and retreat operation to the rocker arms 7 and 8 to open and close the engine valve 9 (other engine valves are not shown). The sliding contact surface with the timing cam 2 is formed by a smooth sliding contact surface made of the heat-resistant synthetic resin molded body 10.

  The OHV engine A shown in the figure has the same mechanism and shape as the OHV engine, which is a well-known four-cycle engine, except for the structure of the main parts of the cam lifters 3 and 4 to be described later. The operating mechanism of the engine, such as a valve operating mechanism for opening and closing the piston, the intake valve and the exhaust valve, is not different from that of a conventionally known OHV engine.

  As shown in FIGS. 2 to 4, the valve open / close cam lifters 3 and 4 of the OHV engine having the features of the present invention are supported by a frame 11 in which ends of arcuate swing arms 3a are combined in an L shape. One of the end portions can be superposed on and supported by a pair of cam lifter shaft portions 3b parallel to the cam shaft 2a of the timing cam 2, and a sliding bearing portion 3c is integrally provided.

  The main body of the cam lifter 3 is formed of a hard member having a required strength such as metal or ceramics, and a heat resistant synthetic resin molded body 10 is joined to a sliding contact surface with the timing cam 2. So as to be integrated.

The heat-resistant synthetic resin molded body 10 only needs to be formed on at least the sliding surface of the cam lifter 3, but can be molded to form the entire or the entire surface of the cam lifter 3 if necessary.
The heat-resistant synthetic resin that is a material forming at least the sliding contact surface of the cam lifter 3 is, for example, polyphenylene sulfide resin (hereinafter abbreviated as PPS), PEEK, polyimide resin, polyamide resin, wholly aromatic polyester resin, polyamideimide resin. An epoxy resin, a phenol resin, and the like can be mentioned. These have heat resistance with a low friction coefficient with the timing cam 2 even under non-lubricated conditions to be heated by the engine drive, and can have a smooth sliding contact surface. adopt.

  The cam lifter 3 is used under high-temperature conditions inside the engine and is used in an environment where it comes into contact with a lubricating oil containing additives. Therefore, the cam lifter 3 has particularly heat resistance and oil resistance to the lubricating oil among the above synthetic resins. It is preferable to form with engineering plastic. In addition, it is particularly preferable to employ an injection-moldable engineering plastic that is excellent in manufacturability.

  Furthermore, among engineering plastics that can be injection-molded, heat resistance, oil resistance, low friction characteristics, wear resistance, and high bondability that allows the cam lifter body made of hard material to be inserted into a molding die and integrated by insert molding PEEK is particularly preferred.

  It is preferable to blend a solid lubricant into the synthetic resin molded body in order to sufficiently reduce the frictional characteristics. Known solid lubricants can be used, such as molybdenum disulfide, graphite, and PTFE.

  The PTFE is preferably a PTFE fired powder obtained by heating and firing PTFE at a melting point or higher than unsintered PTFE. The PTFE fired powder is excellent in uniform dispersibility and wear resistance as compared with PTFE (molding powder, fine powder) that has not been fired and fired.

  Such a PTFE fired powder may be obtained by heating and firing the PTFE powder. Alternatively, PTFE that has not been fired and fired is formed into a molded body, which is heated and fired at a melting point or higher to obtain a sintered body, which is then pulverized. Any of the powders may be used. However, the latter is preferable because it is excellent in dispersibility in the resin composition and the wear resistance and self-lubricating property of the synthetic resin molding is excellent.

  The PTFE fired powder is preferably a powder having an aspect ratio of 3 or less. When the aspect ratio exceeds 3, the dispersibility in the resin composition is inferior, and the wear resistance and the like of the synthetic resin molding may be reduced.

  The PTFE fired powder preferably employs fine particles having a particle size of 150 μm or less. When the particle diameter exceeds 150 μm, the wear resistance of the synthetic resin molded product may be reduced. The 50% particle size is preferably fine particles having a size of 50 μm or less. If the 50% particle diameter exceeds 50 μm, the wear resistance of the synthetic resin molded article may be reduced as described above.

  50% particle diameter (median diameter) is a particle whose accumulated solid particle amount is 50% of the total solid particle amount when a particle size distribution curve of particle size and solid particle amount is obtained by a laser analysis particle size distribution measuring device. Is the diameter. In addition, as a laser analysis particle size distribution measuring apparatus, there is Microtrac HRA manufactured by Leeds & Northrup.

  The PTFE fired powder may be a powder obtained by further irradiating a heat-fired powder with γ rays or electron beams. This treatment further improves the uniform dispersibility.

  Examples of commercially available PTFE calcined powders preferably used in the present invention include Kitamura, Inc .: KT300M, KT400M, KTL610, KTL450, KTL8N, KTL10N, Asahi Glass: Fullon L169J, L170J, L172J, L173J, Sumitomo 3M Manufactured by: Hostaflon TF9205, TF9207, and the like. Examples of the powder irradiated with γ-rays or electron beams after heating and baking include KTL 610, KTL450, KTL8N, KTL10N, and the like.

  It is preferable to blend a fibrous reinforcing material in the synthetic resin molded body in order to increase mechanical strength, particularly compressive strength. A well-known thing can be used as a fibrous reinforcement, For example, various whiskers, such as glass fiber, carbon fiber, an aramid fiber, a titanium oxide whisker, a calcium sulfate whisker, a potassium titanate whisker, a calcium carbonate whisker, are mentioned. Among these, carbon fibers and aramid fibers are preferable because they do not deteriorate the low friction characteristics and are excellent in wear characteristics with respect to the counterpart material. Carbon fiber is more preferable because the cost can be kept low.

  The main body of the cam lifter 3 is preferably made of a sintered body of metal or ceramics. This is because it is easy to manufacture a cam lifter body having a complicated shape as long as it is a sintered body, and it becomes excellent in bonding properties with a synthetic resin molded body.

As shown in FIG. 5, it is preferable to form a concave or convex portion on the joint surface of the main body of the cam lifter 3 with the heat resistant synthetic resin molded body 10 to increase the adhesion strength.
For example, as shown in FIG. 5A, the main body of the cam lifter 3 has a predetermined length extending in the axial direction of the swing arm 3a at the contact portion with the heat-resistant synthetic resin molded body 10, and is axially centered from the surface. A notch having a certain depth (kamaboko-shaped) is formed toward the surface, and a trapezoidal convex portion 12 that is long in the axial direction is formed on the bottom surface of the notched portion.

In addition, the cam lifter 13 shown in FIG. 5B is formed with a plurality of cubic convex portions 14 discontinuously arranged in the axial direction, instead of the long trapezoidal convex portions 12 in FIG. Is.
The cam lifter 15 shown in FIG. 5C is formed by discontinuous cubic concave portions 16 instead of the discontinuous convex portions 14 in FIG.
Further, the cam lifter 17 shown in FIG. 5 (d) is provided with a sawtooth-shaped uneven portion 18 in a wave shape that is continuous with the bottom surface of the notched portion in FIG. 5 (a).

An embodiment of the OHV engine provided with the swing rotation type cam lifter of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the OHV engine includes a valve drive device that includes a timing cam 2 and a pair of swing-rotating cam lifters 3 and 4 that are in contact with the timing cam 2.

  The pair of swing-rotating cam lifters 3 and 4 are used in combination in a state in which the lifter shaft portion 3b is overlapped so as to swing and rotate about the lifter shaft portion 3b. The timing cam 2 and the timing gear 19 are supported coaxially and rotatably by the cam shaft 2a.

  The camshaft 2a and the shaft of the cam lifter shaft portion 3b are arranged in parallel. The timing gear 19 of the timing cam 2 is disposed so as to mesh with a crank gear 20 in a crank (not shown). One swing-rotating cam lifter 3 is connected to an exhaust valve push rod 5, and the other swing-rotating cam lifter 4 is connected to an intake valve push rod 6.

  The usage state of the valve drive device for the OHV engine will be described. By rotating the crankshaft of the crank in the cylinder (not shown), the timing gear 19 that meshes with the crank gear is rotated.

  As a result, the timing cam 2 is rotated, and one of the pair of swing-rotating cam lifters 3 and 4 that are in contact with the timing cam 2 is rotated about the cam lifter shaft portion 3b, via the push rod 5 for the exhaust valve. Then, the engine valve 9 for exhaust is opened. Next, when the timing cam 2 is further rotated, the other oscillating and rotating cam lifter 4 that contacts the timing cam 2 rotates about the lifter shaft portion 3b, via the push rod 6 for the intake valve. Open the intake valve.

  In this way, the operation of the valve is completed by closing the exhaust engine valve 9 at a predetermined time and further closing the intake valve. In this configuration, the pair of swing-rotating cam lifters 3 and 4 are rotated by a single timing cam 2, so that the axial length of the timing cam 2 can be reduced and the single timing cam can be operated. Therefore, the weights of the valve operating mechanism 1 and the OHV engine are also reduced.

  As a lubrication method in the OHV engine of the present invention, any conventional type can be adopted. In the present invention, since the synthetic resin molding 10 is joined to the sliding contact surface of the timing cam 2 of the cam lifter main body made of a hard material to the swing-rotating cam lifters 3 and 4, various lubrication types are available. Even if it employ | adopts, the abrasion in the said sliding contact surface can be prevented.

  In the OHV engine of the present invention, the timing cam 2 can be a synthetic resin molded body. If the timing cam 2 is made of a synthetic resin, it is particularly suitable for an OHV engine that is portablely used, such as a brush cutter, for further weight reduction.

  Examples of the synthetic resin forming the timing cam 2 include PPS, PEEK, polyimide resin, polyamide resin, wholly aromatic polyester resin, and the like. Further, when the timing cam 2 is made of the above 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.

  When the timing cam or the like is made of a synthetic resin, a fibrous reinforcing material such as carbon fiber or aramid fiber is preferably added to the synthetic resin in order to improve mechanical strength. The use of glass fiber as the fibrous reinforcing material is preferably avoided when there is a risk of attacking the synthetic resin molding of the cam lifter.

  The fibrous reinforcing material blended in the synthetic resin forming the timing cam is preferably 5 to 40 parts by mass with respect to 100 parts by mass of the synthetic resin. Because, if the fibrous reinforcing material is less than 5 parts by mass, the effect of improving the strength of the timing cam is small. On the other hand, if the fibrous reinforcing material exceeds 40 parts by mass, the surface smoothness decreases, This is because the synthetic resin molded body is attacked against the sliding contact and there is a risk of wear or the like.

  The oscillating rotary cam lifter of the present invention does not increase the friction torque between the cam lifter and the timing cam even in a state of insufficient lubrication, and can suppress wear due to the friction of the cam lifter. It is preferably used, and can be suitably used as a rocking and rotating cam lifter of a lightweight and compact OHV engine.

DESCRIPTION OF SYMBOLS 1 Valve mechanism 2 Timing cam 3, 4, 13, 15, 17 Cam lifter 2a Cam shaft 3a Swing arm 3b Cam lifter shaft part 3c Sliding bearing part 5, 6 Push rod 7, 8 Rocker arm 9 Engine valve 10 Heat resistant synthetic resin Molded body 11 Frame 12, 14 Convex part 16 Concave part 18 Concave part 19 Timing gear 20 Crank gear A OHV engine

Claims (12)

The cam lifter is slid in contact with the timing cam in the valve mechanism of the OHV engine, and the push rod is linked to this swing to advance and retract in the axial direction, and this advance / retreat operation is transmitted to the rocker arm to open and close the engine valve. In the OHV engine cam lifter
The valve open / close cam lifter for an OHV engine, wherein the sliding contact surface with the timing cam is a smooth sliding contact surface made of a heat-resistant synthetic resin molding.   The cam lifter is composed of a composite body in which a cam lifter body and a heat-resistant synthetic resin molded body are integrated, and a contact surface between the cam lifter body and the heat-resistant synthetic resin molded body is provided with a concave or convex portion to increase the contact area. The cam lifter for opening and closing the valve of the OHV engine according to claim 1.   3. The OHV engine valve opening / closing cam lifter according to claim 1 or 2, wherein the heat-resistant synthetic resin molding is integrated by inserting a cam lifter body into a molding die and insert molding.   The cam lifter for opening and closing the valve of the OHV engine according to claim 2 or 3, wherein the cam lifter body is made of metal or ceramics.   The cam lifter for valve opening / closing of an OHV engine according to any one of claims 2 to 4, wherein the cam lifter body is made of a sintered body.   The cam lifter for opening and closing a valve of an OHV engine according to any one of claims 1 to 5, wherein the heat-resistant synthetic resin molded article contains a solid lubricant and has lubricity.   The valve lift cam lifter according to claim 6, wherein the solid lubricant is a calcined powder of PTFE.   The valve open / close cam lifter for an OHV engine according to any one of claims 1 to 7, wherein the heat-resistant synthetic resin molded body contains a fibrous reinforcing material. The cam lifter is slid in contact with the timing cam in the valve mechanism of the OHV engine, and the push rod is linked to this swing to advance and retract in the axial direction, and this advance / retreat operation is transmitted to the rocker arm to open and close the engine valve. In the OHV engine that performs
An OHV engine comprising the cam lifter according to any one of claims 1 to 8.   The OHV engine according to claim 9, wherein the timing cam is a synthetic resin molded body.   The OHV engine according to claim 10, wherein the synthetic resin forming the timing cam contains carbon fiber or aramid fiber.   The OHV engine according to claim 10 or 11, wherein the timing cam is formed integrally with a timing gear.

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