CN1079899C - Overhead cam engine - Google Patents

Abstract

An overhead cam engine capable of integrally casting a cylinder part, a head part, and a head cover part, including an engine body 1, an inlet cover 2 and a cam chain guard 3. A water jacket 45, a connection part to an intake port 18, and an oil feeding part to a cam shaft 6 are formed between the engine body 1 and the inlet cover 2. A chain chamber 32 is formed between the engine body 1 and a cam chain cover 3 to support a water pump 40 to be driven by a cam chain 35. The engine body 1 is provided with a cylinder part 5 and a cam chamber 7. Valve lifter holes are formed in the engine body 1 and the cam chain guard 3 so that they are situated along the valve axes C1, C2 tilted relative to the cylinder axis C to intersect the cam shaft 6. Inspection holes 36, 37 are provided on an extensions of the respective valve axes C1, C2, in head cover parts 9, and caps 38, 39 are installed.

Description

Overhead camshaft type engine

The present invention relates to overhead camshaft type engine with casting formation.

General motor, its cylinder seat, cylinder head and cylinder cover constitute by casting the ground of split respectively, again with its overlapping assembling respectively.In addition, it also is known (spy opens flat 4-17759 number) that the part of cylinder seat, cylinder head and cylinder cover is cast integratedly, this situation, and cylinder cover is not all to be that a part is shaped integratedly.

And, adopting overhead-cam valve gearing, when supporting camshaft, must cut apart bearing portion up and down, and form cam chamber and valve tappet bore with core with metal bearing.Water jacket in same suction and exhaust ports and the water-cooled engine also must be shaped with core.

Yet the cylinder seat of the example of above-mentioned prior art, cylinder head and cylinder cover are separated to constitute, and because of number of spare parts is many, sealing surface is many and increase the machining period number.In addition, the part that must add the packing ring class on sealing surface improves the reliability of sealing.And in order to ensure the sealing surface of packing ring, wall thickness and aperture between cylinder and the water jacket just are restricted.

Even under the situation of a part of integrally casting of cylinder seat, cylinder head and cylinder cover, because the shaping of cam chamber, valve tappet hole, suction and exhaust ports and water jacket uses the making and the sand removal of core, core also to need a lot of man-hours.And cylinder cover is in the camshaft part, the pact that must cut apart, comprise the cylinder cover that covers the camshaft upper section up and down all can not with cylinder head integrally casting continuously.And because divided metal bearing up and down, cam chair also is essential, because cam chair and cylinder head must coaxial processing, therefore, the bearing construction of camshaft complexity and its processing are also taken time and energy very much.So purpose of the present invention is exactly to solve above-mentioned relevant problem.

In order to address the above problem, the overhead camshaft type engine of the 1st invention of the application's overhead camshaft type engine has: cylinder part, cylinder head and cylinder cover portion, this cylinder part is accommodated piston with being used for free sliding, this cylinder head has the firing chamber, the suction and discharge valve reaches the cam chamber of accommodating camshaft revolvably, the cam that drives the suction and discharge valve is being set on this camshaft, described cylinder cover portion covers cam chamber, it is characterized in that, cast at least a portion that forms above-mentioned cam chamber and head-shield portion along the axial withdrawing pattern of camshaft and cover under the state above the camshaft using, be integrally cast into shape said cylinder portion, cylinder head and cylinder cover portion.

The 2nd invention is on the basis of above-mentioned the 1st invention, it is characterized in that, the mould of formation cam chamber is shaped integratedly and along same direction withdrawing pattern with the mould of a side that forms the motor profile.

The 3rd invention is on the basis of above-mentioned the 1st invention, it is characterized in that, the valve tappet hole of accommodating valve tappet in cylinder head intersects with camshaft line and forms by casting.

The 4th invention is on the basis of above-mentioned the 3rd invention, it is characterized in that, in said cylinder head-shield portion, along on the axis elongation line in above-mentioned valve tappet hole, be provided with the cam peep hole that connects cam chamber, loading and unloading freely are installed with the cover component of inaccessible cam chamber on this cam peep hole.

According to the 1st invention, owing to form cam chamber, so cylinder part, cylinder head and comprise the cylinder cover portion that covers the camshaft upper section and can be integrally cast into shape by axial withdrawing pattern casting along camshaft.Therefore, can reduce the quantity of part, owing to there not being sealing surface essential on these connecting parts to reduce man-hour, the sealing of sealing surface has not needed yet.Do not had for guaranteeing to seal the countercylinder followed and the restriction in wall thickness between the water jacket and aperture yet.

Owing in the forming process of cam chamber, do not use core, therefore manufacture core and sand removal has not just needed desired a lot of man-hours, and, be connected with cylinder head and casting integratedly because cylinder cover is whole, therefore the bearing that needn't cut apart the camshaft part up and down, because can abolish cam chair and needn't coaxial machining cam seat and cylinder head, therefore, bearing construction is simple and processing is also not too bothersome.

According to the 2nd invention, casting is a die casting, in this mould, the mould that forms cam chamber is an one with the mould that forms the motor profile, and along same direction withdrawing pattern, therefore when forming the motor profile, cam chamber also also can form along camshaft direction withdrawing pattern, easily the builder cam chamber.

According to the 3rd invention, because the valve tappet hole of accommodating valve tappet intersects with camshaft line and formed by casting, therefore, and when the cam chamber of formation cylinder head, the valve tappet hole that also can be shaped simultaneously, owing to abolishing core, can significantly reduce man-hour.

According to the 4th invention, owing to be provided with the cam peep hole that connects cam chamber on the axis elongation line in the valve tappet hole in head-shield portion, this peep hole can form simultaneously with the casting in valve tappet hole.And owing to load and unload the cover component that inaccessible cam chamber freely is installed on this cam peep hole, this peep hole can also be as the hole of maintenance usefulness.

Fig. 1 is the whole sectional view of the motor of present embodiment.

Fig. 2 is the right side view that removes breathing mask.

Fig. 3 is the left side view that removes the cam chain guard.

Fig. 4 is the 4-4 line sectional view of Fig. 1.

Fig. 5 is the 5-5 line sectional view of Fig. 1.

Fig. 6 is the sectional view of main body portion.

Fig. 7 is the figure of the mating face side of expression breathing mask.

Fig. 8 is the figure of the mating face side of expression cam chain guard.

Fig. 9 is the sectional view of the casting mould of expression main body portion.

Figure 10 is the sectional view of mould of the mould-forming method of expression cam chamber and valve tappet bore.

Figure 11 is the die cut view of the mould-forming method of expression water jacket.

Figure 12 is the 2nd embodiment's the figure that is equivalent to Fig. 1.

Figure 13 is the 3rd embodiment's the figure that is equivalent to Fig. 1.

Below, explanation is applicable to an embodiment of the water-cooled 4 circulation float tolerance motors that equipment of small motor bicycle is used with reference to the accompanying drawings.Fig. 1 is the whole sectional view of the motor relevant with present embodiment.Fig. 2 is the right side view that removes breathing mask, and Fig. 3 is the left side view that removes the cam chain guard.Fig. 4 is the 4-4 line sectional view of Fig. 1.Fig. 5 is the 5-5 line sectional view of Fig. 1, and Fig. 6 is the sectional view of main body portion.Fig. 7 is the figure of the mating face side of expression breathing mask, Fig. 8 is the figure of the mating face side of expression cam chain guard, Fig. 9 is the sectional view of the casting mould of main body portion, Figure 10 is the die cut view of the mould-forming method in expression cam chamber and valve skewer bar hole, and Figure 11 is the die cut view of the mould-forming method of expression water jacket.

The motor of present embodiment is breathing mask 2 and cam chain guard 3 are installed on the two opposite side surfaces that is formed on the almost parallel on its length direction of body 1 of about cuboid shape and are assembled into together, body 1 usefulness of above-mentioned about cuboid shape is shaped casting methods such as suitable metal casting forming such as aluminum alloy, and this motor is installed on the crank housings (diagram is omitted).

Body 1 is by cylinder head 5 and head 8 integrally formed making.The piston 4 that is attached to crankshaft (diagram is omitted) by connecting rod 4a is being accommodated by said cylinder portion 5, and said cylinder head 8 has the cam chamber 7 that camshaft 6 is freely accommodated in rotation.

In this application, the part that covers the cam chamber 7 in the cylinder head 8 is called cylinder head 9 especially, for convenience, each face address for body 1 is as follows: the face that breathing mask 2 is installed is called right flank 10, the face that the cam chain guard is installed is called left surface 11 (Fig. 6), the face of the installation aftermentioned radiator in the relative two sides of being clamped by this two sides is called front 12, and another side is called the back side 13 (Fig. 5).In addition, the outer surface of cupular part of cylinder cover portion 9 is called end face 14, and the face that is installed on the crank housings is called bottom surface 15 (Fig. 1).

In cylinder part 5,15 sides form cylinder 16 to the about intermediate portion of the length direction of body 1 from the bottom surface, the the inside that is formed on this cylinder 16 is that the firing chamber 17 on cylinder head 8 sides is communicated with intakeport 18 and relief opening 19, the opening portion of firing chamber 17 sides of each mouthful is opened and closed by air-breathing valve 20 and exhaust valve 21, and the relative cylinder axis C of axis C1, the C2 of each valve constitutes the valve angle of regulation.Symbol 20a and 21a are the bar covers.

Intakeport 18 is communicated with the air suction way 22 that forms on breathing mask 2, and this air suction way 22 stretches out on the elongation line of intakeport 18 sideling, receives on the vaporizer (diagram is omitted) by supplying tube 23.Relief opening 19 is to extending perpendicular to the direction of intakeport 18 approximately, joining with outlet pipe 24 on 13 overleaf.Symbol 29 among Fig. 2 and Fig. 3 is ignition spark plugs.

The driving of each valve, adopt direct-acting type, the valve lifter 25,26 of the shaft end by being arranged on each valve is directly driven by cam 27,28.Form the camshaft 6 of cam 27,28, connect between right flank 10 and left surface 11, at two open ends of the cam chamber 7 that forms taper by bearing 30,31 supportings.Each slip surface of cam 27,28 is corresponding with the slip surface of valve tappet 25,26 respectively and become the plane of inclination.In addition, form the oil supply 6a of portion between an end of camshaft 6 and the breathing mask 2.

The other end of camshaft 6, outstanding in the chain chamber 32 that is formed between cam chain guard 3 and the left surface 11, on this outstanding end, cam sprocket wheel 33 is installed with bolt 34.This cam sprocket wheel 33 by cam chain 35 around linking on the driving sprocket wheel that is arranged on the crankshaft that figure do not show.

On each valve axis C1 in head-shield portion 9 and the elongation line of C2, forming with each valve axis C1 and C2 is coaxial and with the cam peep hole 36,37 of each valve tappet 25,26 roughly the same diameter, the lid 38,39 of make and break cam chamber 7 is fixed by the seal ring sealing and with screw thread respectively.

Firing chamber 17 at body 1 is nearby located, be provided with water pump 40, as shown in Figure 5, on the side wall portion of cam chain guard 3, forming the recess 41 that pulsator is installed at main body portion 1, accommodating flange 42 in this pump installation recess 41, this flange 42 forms the part of the resinous cover of the profile that is water pump 40.This flange 42 also is the almost same circle of recess 41 to be installed and to be fitted to the surrounding wall portion that pump is installed recess 41 by O RunddichtringO 44 liquid seals ground with pump, so, sealed among the pump installation recess 41.

The pump housing 43 is entrenched in the pump of the inboard of flange plate 42 and installs in the recess 41, is covered with the opening portion of water jacket 45.Impeller 46 is provided in the central part of the pump housing 43 and rotates integratedly with pump shaft 47 and freely is being supported, and the opening portion that is communicated with impeller 46 and water jacket 45 is formed on the suitable position of central part of the impeller 46 in the pump housing 43, and constitutes water passage 43a.

The one end rotation of pump shaft 47 freely is bearing on the lug boss 48, this lug boss 48 is given prominence on the periphery wall that is formed on cylinder 16 and is outstanding in water passage 43a, the distolateral cam chain 35 of crossing of another of pump shaft 47 protrudes in the chain chamber 32, around it, be provided with magnet ring 49, around it, form and use and the minor diameter part 50 of flange plate 42 for the part covering of the resinous cover of one, this minor diameter part 50 is done circular, and it is on the chimeric chimeric recess 51 that is bearing in the circle that is formed on the cam chain guard 3 in the side-prominent end of cam chain guard 3.

As shown in Figure 3, the decentraction of the center of minor diameter part 50 and flange 42, that each center of recess 41 is installed is also inequality with the concentric chimeric recess 51 of minor diameter part 50 with the concentric pump of flange 42.Be fitted at minor diameter part 50 under the state of chimeric recess 51, flange 42 is fitted to pump and installs on the recess 41, and by cam chain guard 3 usefulness bolts etc. are fixed on the left surface 11, water pump 40 is fixed on pump and installs on the recess 41.

As shown in Figure 5, be provided with the integrated water pump in interior all sides of magnet ring 52 with sprocket wheels 53 at the peripheral part of minor diameter part 50, and with cam chain 35 drivings.Water pump freely is housed in the water pump accommodation section 55 of the circle that is formed on the cam chain guard by bearing 54 rotations with the lug boss periphery of sprocket wheel 53.

When magnet ring 52 and water pump rotated integratedly with sprocket wheel 53, the magnet ring 49 in the minor diameter part 50 was by magnetically combinations, and rotation integratedly, thus, by with pump shaft 47 rotary blades 46 of magnet ring 49 one, water pump 40 becomes drive condition.

On the front surface 12 of main body portion 1, give prominence to respectively horizontally-arranged row and forming water out 56 and water inlet 57, water out 56 be formed on cam chain guard 3 near, be communicated with discharge road 58 on being arranged on the pump housing 43.Discharge road 58 and be connected with slightly circular-arc path 59, this slightly circular-arc path 59 communicates on every side with the impeller 46 of the pump housing 43 inside.Water inlet 57 be positioned at breathing mask 2 near and be communicated with water jacket 45.

Direct respectively chimeric backwater mouth 61 and the water delivery nozzle 62 that is connecting radiator 60 of this water out 56 and water inlet 57, backwater mouth 61 is connected on the upper water box 64 by backwater path 63, and this backwater path 63 extends in the radiator 60 point-blank along the extending direction of discharging road 58.

As shown in Figure 6, the bar trepanning 86,87 of valve tappet hole 84,85 and path is formed on the cylinder head 8 of body 1, each valve tappet 25,26 is accommodated in above-mentioned valve tappet hole 84,85, above-mentioned bar trepanning 86,87 extends to intakeport 18 and relief opening 19 continuously from the top in above-mentioned valve tappet hole 84,85, extend along valve axis C1 or C2 in each hole, the elongation line of each valve axis C1 or C2 intersects with the axis of camshaft 6 (central axis of cam chamber) and extends, and cam peep hole 36,37 is formed in the cylinder cover portion 9 on the elongation line of above-mentioned C1, C2.

As shown in Figure 7, the coolant seal 65 of rectangle, oval-shaped suction seal circle 66, the oily portion seal ring 67 that is about P font is formed on the mating face side of the breathing mask 2 on the right flank 10 that is installed in main body portion 1, because breathing mask 2 covers on the right flank 10 of main body portion 1, make between right flank 10 and breathing mask 2 that water, mixed gas and oil content are liftoff to be sealed.

Symbol 67 among Fig. 7 is the recesses that are connected with the oil circuit 67a (Fig. 5) that leads to main vertically lubricated ditch, the 68th, on the axle head that is formed on camshaft 6, send oily 6a (Fig. 1 of portion, Fig. 4) the oily path of fuel feeding, the symbol 69 among Fig. 4 are installation boss of ignition spark plug 29.

Fig. 9 is the be shaped facial mold structure that cuts open of body 1 shown in Figure 1 of expression, and it is made of the right mould 70 of the right flank 10 that forms body 1, the left mould 71 that forms left surface, the cylinder mould 72 that forms cylinder 16 parts, the patrix 73 that forms end face 14.As shown in figure 11, face mould 92 and back side mould 97 before the formation at the front 12 and the back side 13 is also used respectively.

Following hole 18a, the teat 76 that the step bearing portion that teat 74, teat 75, teat 76 are formed on the right mould 70, this teat 74 is equivalent to camshaft, teat 75 form a part that is equivalent to intakeport 18 is equivalent to the water jacket 45 of breathing mask 2 sides.

Teat 77, pin 79, teat 80 are formed on the left mould 71, this teat 77 usefulness casting withdrawing pattern method forms cam chamber 7, this cam chamber 7 is front end thin cone-shaped, pin 79 and is used to form vent 78, teat 80 and is equivalent to pump recess 41 is installed, and forms the forming section 81 that is equivalent to jut 48 in the central authorities of this teat 80.

Forming teat 82 and teat 83 on cylinder mould 72, this teat 82 is equivalent to form the following hole 18b of the part of air suction way 18, and teat 83 is equivalent to the following hole 19a of relief opening 19.

On patrix 73, sliding pin is being set, this sliding pin is used to use casting withdrawing pattern method to form following hole 86a, 87a and the cam peep hole 36,37 of the bar trepanning 86,87 of valve tappet hole 84,85, path simultaneously, above-mentioned valve tappet hole 84,85 is used to accommodate valve tappet 25,26, and the bar trepanning 86,87 of above-mentioned path is connected with the front end in valve tappet hole 84,85 and extends to intakeport 18 and relief opening 19.

As shown in figure 10, sliding pin 88,89 along valve axis C1, the C2 freedom of advancing and retreat obliquely, intersects with teat 77 during shaping respectively, at this moment the front end of each sliding pin 88,89 lay respectively at teat 75,82 and 83 near.

After the shaping, each sliding pin 88,89 slides to the top of figure along valve axis C1, C2 respectively, when opening each mould, by opening left mould 71 left, form the left surface 11 of main body portion 1, simultaneously owing to extract teat 77, thereby cast out cam chamber 7 to same direction, in addition, by each sliding pin 88,89, casting simultaneously forms valve tappet hole 84,85, following hole 86a, the 87a of bar trepanning 86,87 and cam peep hole 36,37.

Then, only carry out each time hole (18a, 19a, 86a, 87a) etc. the machining of boring and the cutting of hole portion inner peripheral surface and the screw thread processing of peep hole 36,37 etc. 9 threes of head-shield portion that just can finish cylinder part 5, head 8 and cover the top of cam chamber 7 are the body 1 of one.

Figure 11 represents to form the mold structure of water jacket 45 parts, and the teat 76 of right mould 70 and the teat 80 of left mould 71 have the forming face 90,91 of semicircle arcuation, so that have the gap of the wall thickness degree of cylinder 16 respectively around cylinder mould 72, and surrounds ring-type.Mould 92 is provided with the teat 96 that is used to cast out the casting pin 93,94 of water outlet 50 and water inlet 51 and is used to form medial concavity 95 in front.Symbol 97 is a back side mould.

As shown in Figure 5, each forming face 90,91 has formed the space of on four jiaos of the cylinder part 5 of surrounding cylinder 16 chimeric guide portion 101,102,103 and 104, and these guide portions 101,102,103 and 104 are all opposed with the guide surface of the arc-shaped surface of the periphery that slightly is parallel to cylinder 16.From the pump housing 43 outstanding and formation guide portions 101 and 102, guide portion 103 and 104 is formed on water jacket 45 sides of breathing mask 2.

The pump housing 43 in the face of the face of water jacket 45 constitutes the guide surface of the concave shape of surrounding cylinder 16, wherein the intermediate portion in guide portion 101 and 102 forms towards the opening portion of water jacket 45 and constitutes water passage 43a.In addition, form continuous curved surface between the guide portion 103 and 104, water jacket 45 sides of breathing mask 2 form the guide surface 105 of an integral body.But the water inlet 57 in this guide surface 105 nearby part forms sluicing face 106 partly.Shell surface side at breathing mask 2 is forming air cooling fan 107.

The effect of present embodiment then, is described.Because the axial withdrawing pattern to camshaft 6 forms cam chamber 7, so can be integrally cast into shape cylinder part 5, therefore cylinder head 8 and cylinder cover portion 9 can reduce number of spare parts, because of there not being sealing surface essential on these connecting parts to reduce machining period, the sealing of sealing surface has not needed yet.The countercylinder of following in order to ensure sealing surface and the restriction in wall thickness between the water jacket and aperture have not had yet.The motor integral intensity has also improved in addition.

And, as the post-production of the body 1 after the casting is only carried out a small amount of machining, just can easily form by cylinder part 5, cylinder head 8 and 9 threes of cylinder cover portion of covering the top of cam chamber 7 is the body 1 of one, so the manufacturing efficiency of body 1 has improved.And because with casting forming, forming face better appearance and the densification of using mould, because it is it is many not need to rebuild the place of handling with machining, more favourable in the manufacturing.

In addition, owing in the forming process of cam chamber 7, do not use sand core, so, the making of core and sand removal just do not need needed a large amount of man-hour, and, the approximately whole of cylinder cover portion 9 except peep hole 36,37 is connected with cylinder head 8 also and can casts integratedly, so the two ends of camshaft 6 are supported just passable with the bearing 30,31 that does not need to cut apart of ball bearing etc.Therefore, do not use the metal bearing that separates up and down just can do.Owing to can abolish cam chair and needn't coaxial machining cam seat and cylinder head, can simplify bearing construction.

And, the model of formation cam chamber 7 just teat 77 is arranged to one with the left mould 71 of the left surface 11 that forms body 1, and the direction withdrawing pattern identical with the die sinking direction of left mould 71, in the profile that forms body 1, cam chamber 7 also can be to camshaft direction casting withdrawing pattern and integrally formed, so the shaping of cam chamber 7 is easy to.

By be located at sliding pin 88,89 on the patrix 73 and teat 77 combinations, with camshaft line cast form valve tappet hole 84,85 across, so when forming the cam chamber 7 of cylinder head 8, valve tappet hole 84,85 can be shaped simultaneously, and owing to can abolish core, man-hour, number can reduce significantly.

And, in head-shield portion 9, on the elongation line of valve axis C1, C2 by valve tappet hole 84,85, be provided with the cam peep hole 36,37 that penetrates cam chamber 7, therefore, this peep hole 36,37 can form simultaneously with the casting in valve tappet hole 84,85, and, therefore can be used as maintenance and use the hole owing to loading and unloading on this cam peep hole 36,37 freely are installed with lid 38,39.

Figure 12 is the 2nd embodiment, in this embodiment, is giving prominence to the roof 110 and the sidewall 111 of chain chamber 32 integratedly to the side around the left surface 11 of body 1, and the connecting part 112 of chain guard 3 is arranged on the outside of cam chain 35.

So, chain chamber 32 also can cast formation integratedly with body 1.And become simple because of combining with single with the structure of the connecting part 112 of chain guard 3.The same embodiment is identical for other structure, and common part is used common symbol (as follows).

Figure 13 is the 3rd embodiment of the present invention who is applicable to air-cooled engine.In this embodiment, abolish water pump, water jacket and breathing mask, simultaneously, on cylinder part 5, formed air cooling radiating fin 120.This air cooling radiating fin 120 can be formed by casting simultaneously with the shaping of right flank 10.So, the cooling function with air cooling radiating fin 120 can obtain sufficient cooling capacity.

But, though the cam chamber 7 of present embodiment does not penetrate right flank 10,, constant with the same part that forms of aforementioned each embodiment.The structure of chain chamber 32 is identical with the 2nd embodiment, and the sprocket wheel rotation freely is bearing in chain guard 3 sides at a slow speed, and in addition, the hole of passing through of chain is formed on the side protuberance of cylinder part 5 by casting.

The application's invention is not limited to the various embodiments described above, and it can do all distortion, and for example, the casting method of not necessarily non-employing casting forming in the 1st invention at least can adopt and use other known casting method such as sand mo(u)ld.In addition, though cylinder cover portion at least its part to cover the camshaft top just passable,, cover part on this camshaft and must form part with other body and be shaped integratedly.

Claims (4)

1. overhead camshaft type engine, it has: cylinder part, cylinder head and cylinder cover portion, accommodating piston this cylinder part free sliding, head has the firing chamber, suction and discharge valve and cam chamber, this cam chamber is rotatably accommodated camshaft, this camshaft is provided with the cam that drives the suction and discharge valve, cylinder cover portion is used to cover cam chamber, it is characterized in that, above-mentioned cam chamber is used along the casting process of the axial withdrawing pattern of camshaft and is shaped, and, under the state above at least a portion covering camshaft of cylinder cover portion, cylinder part, cylinder head and cylinder cover portion are integrally cast into shape.

2. overhead camshaft type engine as claimed in claim 1 is characterized in that, is formed integratedly and to same direction withdrawing pattern by the mould of the mould that forms cam chamber with a side of the profile that forms motor.

3. overhead camshaft type engine as claimed in claim 1 is characterized in that, the valve tappet hole of accommodating valve tappet intersect with camshaft line and by cast form at the said cylinder head.

4. overhead camshaft type engine as claimed in claim 2, it is characterized in that, the cam peep hole that connects cam chamber is located on the axis elongation line in the above-mentioned valve tappet hole in the said cylinder head-shield portion, and the loading and unloading of the cover component of inaccessible cam chamber are mounted freely on this peep hole.

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