JPH0267409A - Decompressor of engine - Google Patents

Abstract

PURPOSE:To simplify the construction of a decompressor by forming an insert hole which extends in parallel with the axis of a cam shaft, inside this cam shaft and inserting a cam shaft of the decompressor into this insert hole as that the shaft is able to be turned about the axis of the cam shaft. CONSTITUTION:A recess 49 is formed on the bottom face of the base part of an input gear 29 and an insert hole 51 is formed as it extends toward the inside of a cam shaft 28 in the direction at right angle with large diameter holes 44b and 45b. The decompressor cam shaft 52 is turnably inserted into this insert hole 51. Cam parts 53 are formed on the decompressor cam shaft 52 for projecting into the large diameter holes 44b and 45b, respectively. According to the turning speed of the cam shaft 28, the decompressor cam shaft 52 is turned at the specified angle via an eccentric pin 54 by a turning means 55 until a cam projection 47 is engaged with a circular face 53a of the cam shaft 52, whereby projecting the cam projection 47. So each of exhaust valves is opened via related tappets 39 to release the pressure in a combustion chamber.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an engine decompression device.

(Prior art) The decompression device mentioned above is for releasing the pressure inside the cylinder.This device, for example, releases the pressure at the beginning of the compression stroke to lighten cranking, thereby making it easier to start the engine. It is also used to stop the engine by releasing pressure and making it impossible to ignite inside the cylinder.

Conventionally, such a decompression device is disclosed in U.S. Pat. No. 338
There is one shown in Publication No. 1676.

According to this, a cam protrusion that can move outwardly from the outer surface of the camshaft is provided, and the cam protrusion is provided adjacent to a cam portion formed on the camshaft. On the other hand, a weight plate is pivotally supported on the side surface of the input gear of the camshaft, and a decompression camshaft that cam engages with the cam protrusion is provided on this weight plate, and the weight is attached in one direction by a spring. Forced.

When the camshaft rotates in conjunction with the crankshaft at a low speed, the decompression camshaft is biased by the spring to push the cam projection and cause it to protrude. In this case, as the camshaft rotates, the cam projection engages with the exhaust valve side to open the exhaust valve, and the pressure inside the cylinder is released.

Also, when the rotation of the camshaft reaches a certain level, the weight plate rotates against the spring due to the centrifugal force, and the decompression camshaft linked to this rotates to release the above-mentioned push against the cam protrusion. It has become. In this case, the cam protrusion does not open the exhaust valve, and one normal operation is performed thereafter.

(Problems to be Solved by the Invention) Incidentally, in the above conventional configuration, the cam protrusion is provided between the cam portion and the input gear, but due to the convenience of other configurations, the cam protrusion is provided between the cam portion and the input gear. You may want to provide this cam protrusion on the opposite side of the input gear.

However, since the cam part engages with the exhaust valve side, the space on the input gear side and the space on the opposite side are separated by this engagement part as a boundary. Therefore, it is extremely difficult to connect the weight plate pivotally supported on the side surface of the input gear and the cam projection beyond the cam portion. That is, in the above-mentioned conventional configuration, large restrictions are imposed on the arrangement of the cam projections.

Furthermore, for example, in the case where a plurality of cam parts are provided along the axial direction of the camshaft on one side of the input gear, if a decompression device is provided for each of these cam parts, the one farthest from the input gear The cam protrusion provided corresponding to the cam part of the above and the weight plate pivotally supported on the side of the manual gear are connected by the decompression cam shaft beyond the cam part near the input gear. This is extremely difficult for the reasons mentioned above. Therefore, it becomes necessary to provide each cam portion with an independent decompression device. However, this complicates the configuration of the decompression device, which is not preferable.

(Object of the Invention) This invention was made in view of the above-mentioned circumstances, and it is possible to increase the degree of freedom in the arrangement of cam protrusions.
Another object of the present invention is to make the configuration of a decompression device as simple as possible even when a plurality of cam protrusions are provided along the axial direction of a camshaft.

(Structure of the Invention) A feature of the present invention for achieving the above object is that a fitting hole is formed inside the camshaft and extends along the axis of the camshaft, and the decompression camshaft is inserted into the fitting hole. It is fitted in such a way that it can rotate freely around its axis.

Note that the above configuration may be applied to a camshaft in which a plurality of cam protrusions are provided along the axial direction of the camshaft.

(for production) The effects of the above configuration are as follows.

Since the decompression camshaft 52 is provided inside the camshaft 28 and extends along the axis of the camshaft 28, no matter where the cam projection 47 is placed in the axial direction of the camshaft 28,
The decompression camshaft 52 can be extended to a desired length without being influenced by the cam portion formed on the outer circumference of the camshaft 28 or other components, and can be cam-engaged with the cam projection 47.

Furthermore, when a plurality of cam projections 47 are provided along the camshaft 28, the decompression camshaft 52 may be extended so as to cam engage with each of these cam projections 47.
That is, one decompression camshaft 52 can be cam-engaged with each of the plurality of cam projections 47 .

(Example) Embodiments of the present invention will be described below with reference to the drawings.

(First example) 1 to 6 show a first embodiment.

In FIG. 2, l is a 4-cycle V-type engine, which is used to drive a lawnmower, and arrow Fr in the figure indicates the front of the vehicle body.

Reference numeral 2 denotes a crankcase, and a crankshaft 3 whose axis is vertically oriented is supported on the crankcase 2. A pair of left and right cylinders 4.4 are protruded from the front surface of the crankshaft 3, and each of these cylinders 4. The cylinder 4 consists of a cylinder block 6 integrally molded with the crankcase 2 and a cylinder head 7 attached to the protruding end of each cylinder block 6.
will be accomplished. The piston 8 fitted into each cylinder 4 and the crankshaft 3 are connected by a connecting rod 9.

A space surrounded by the inner surfaces of the cylinder block 6 and cylinder head 7 and the end surface of the piston 8 is a combustion chamber 11, and each cylinder head 7 is formed with an intake boat 12 and an exhaust port 13. ing. Further, an intake valve (not shown) that opens and closes each intake port 12 and an exhaust valve 14 that opens and closes each exhaust port 13 are provided, and each of these valves is attached by a spring 15 in the direction of closing each corresponding boat. Forced. A valve operating mechanism 17 is provided that opens and closes each of the above-mentioned valves in synchronization with the rotation of the crankshaft 3.

An intake pipe 18 extends from each intake port 12,
A carburetor 19 and an air cleaner 20 are connected to the junction of both intake pipes 18 . On the other hand, although not shown in the drawings, each exhaust port 13 is connected with an exhaust pipe or a silencer. Additionally, 21 is a spark plug.

A power transmission device 23 is connected to the rear of the engine 1, and power is applied to an output shaft 24 of the power transmission device 23 from the crankshaft 3 via a gear reduction device (not shown). .

Further, the power of the output shaft 24 is transmitted to the driving wheels of the lawnmower via the universal joint shaft 25.

The valve mechanism 17 will be explained with reference to FIGS. 1 and 2. A camshaft 28 whose axis is vertically oriented is supported in the crankcase 2 between the left and right cylinders 4.4.
An input gear 29 is integrally molded at the lower part of the input gear 8. The power of the crankshaft 3 is transmitted through a driving gear 30, an intermediate large gear 31 supported by the crankcase 2, an intermediate small gear 32,
and is sequentially transmitted to the camshaft 28 via the input gear 29. This camshaft 28 then rotates in the direction of arrow R in FIG.

Further, the camshaft 28 is above the manual gear 29,
Further, in order from the input gear 29, a first exhaust cam part 34, a second exhaust cam part 35, a first intake cam part 36, and a second intake cam part 37 are provided. The first exhaust cam part 34 is connected to the exhaust valve 14 of the left cylinder 4, the second exhaust cam part 35 is connected to the exhaust valve 14 of the right cylinder 4, and the first intake cam part 36 is connected to the intake valve of the left cylinder 4. Also,
The second intake cam portion 37 is connected to the intake valve of the right cylinder 4 via a tappet 39, a bushing rod 40, and a rocker arm 41, respectively.

When the camshaft 28 rotates with the crankshaft 3, each of the cam parts 34 to 37 opens the valve corresponding to this cam part via the tappet 39, bushing rod 40, etc., and this causes the engine l to open. The exhaust stroke, intake stroke, etc. can be obtained.

In the above configuration, a decompression device 43 is provided. This decompression device 43 will be explained below with reference to FIGS. 1, 3, and 4.

A first through hole 44 and a second through hole 45 are formed in the camshaft 28 at positions corresponding to the first exhaust cam portion 34 and the second exhaust cam portion 35, respectively. Each through hole 44.45
pass through the camshaft 28 in a substantially radial direction, and each end thereof has a small diameter hole 44a.

45a and opens toward the corresponding tappet 39,
The other end has large diameter holes 44b and 45b.

A bottle-shaped cam protrusion 47 is fitted into each of the through holes 44 and 45 so as to be slidable in the axial direction, and by this sliding, one end of each protrusion can move in and out from the outer surface of the camshaft 28 toward the tappet 39 side. has been done. Further, each of the cam projections 47 has a head 47a that is fitted into the large diameter holes 44b and 45b, and a small diameter hole 44a.

A spring 48 is provided between the head 47a and the step surfaces 44c and 45c formed between the large diameter holes 44b and 45b.
will be provided. This spring 48 is connected to each cam protrusion 47.
is urged in the direction of retreating into each through hole 44,45.

On the other hand, a recess 49 is provided on the lower surface side of the base of the input gear 29.
A fitting hole 51 extends linearly from this recess 49 toward the inside of the camshaft 28 and along the axis of the camshaft 28, and this fitting hole 51 is connected to each of the large diameter holes 44b. ,
45b at a right angle. And this insertion hole 51
A decompression camshaft 52 is fitted into the decompression camshaft 52 so as to be rotatable about its axis. A cam portion 53 is formed on each of the decompression cam shafts 52 corresponding to the large diameter holes 44b and 45b, and the cam portion 53 has a semicircular cross section, and its outer surface includes an arcuate surface 53a and a flat surface 53b. It is configured. Further, an eccentric pin 54 is attached to the protruding end of the decompression camshaft 52 corresponding to the recess 49.

A rotating means 55 is provided for rotating the decompression camshaft 52 according to the rotational speed of the camshaft 28. This rotation means 55 has an arc-shaped weight plate 57 that is supported by a pivot shaft 56 on the lower surface of the input gear 29.
7 is rotatable along the lower surface of the input gear 29 in the direction toward or away from the camshaft 28 .

An arcuate long hole 59 centered around the pivot shaft 56 is formed at the rotating end of the weight plate 57, and this long hole 59 fits into a stopper pin 60 protruding from the lower surface of the input gear 29. ing. Since each end of the elongated hole 59 comes into contact with the stopper bin 60, the weight plate 57 is prevented from rotating more than a predetermined amount in any direction. Further, a spring 61 is provided that biases the weight plate 57 in a direction toward the camshaft 28. Furthermore, an engagement notch 62 is provided on the rotating end side of the weight plate 57, and the eccentric bin 54 is engaged with this engagement notch 62.

As shown in FIGS. 1, 3, and 4, when the engine 1 is started, the crankshaft 3 is rotating at a low speed, that is, the camshaft 28 that is interlocked therewith is rotating at a low speed. In this case, the weight plate 57 is urged by the spring 61 and rotates toward the camshaft 28 side. -The decompression camshaft 52 is rotated to a predetermined angle as shown in the figure by the eccentric pin 54 that engages with the engagement notch 62 and accompanies the rotation of the weight plate 57. At this time, the cam protrusion 4 is attached to the arcuate surface 53a of the decompression camshaft 52.
7 engages with the cam, this cam protrusion 47 is pushed and one end thereof is made to protrude from the outer surface of the cam shaft 28.

Therefore, in addition to causing the first exhaust cam part 34 and the second exhaust cam part 35 to open each exhaust valve 14 by the rotation of the camshaft 28,
Each cam projection 47 further cams into engagement with the corresponding tappet 39 to open each exhaust valve 14, ie, the pressure in the combustion chamber 11 is released.

Next, when the engine 1 enters a normal operating state and reaches a certain high speed rotation, the camshaft 28 also rotates at a high speed, and the weight plate 57 The force causes it to rotate in a direction away from the camshaft 28 against the force of the spring 61. Then, the decompression camshaft 52 is rotated to the angle shown in the figure by the eccentric pin 54 engaged with the engagement notch 62 of the weight plate 57, and at this time, the cam is attached to the flat surface 53b of the decompression camshaft 52. When the protrusion 47 engages with the cam, the pressing force on the cam protrusion 47 is released. That is, the cam projection 47 is biased by the spring 48 and one end thereof is retracted into each through hole 44,45.

Therefore, in this case, each cam protrusion 47 is connected to each exhaust valve 1.
No. 4 is opened, and a normal operating state is obtained.

Furthermore, if the camshaft 28 rotates at a low speed from the above state,
The state returns to the state shown in FIGS. 1, 3, right, and 4.

In addition, in the case of the above configuration, each through hole 44.45 is connected to the camshaft 2.
In other words, they are formed so as not to pass through the cam surfaces of the first exhaust cam part 34 and the second exhaust cam part 35. Further, in this case, the fitting hole 51 is required to intersect each of the through holes 44, 45 at a right angle as much as possible, so that the fitting hole 5I is also slightly inclined with respect to the axis of the camshaft 28.

In the above embodiment, two cylinders 4.4 are controlled, but the number of cylinders 4 may be one or three or more.

(Second example) FIGS. 7 to 10 show a second embodiment.

The basic structure and operation of this embodiment are the same as those of the previous embodiment. Therefore, the common configurations will be designated by reference numerals in the drawings and their explanations will be omitted, and only the different configurations will be explained.

Each through hole 44 , 45 extends along the radial direction of the camshaft 28 , and the fitting hole 51 extends parallel to the axis of the camshaft 28 . Furthermore, due to the machining of the camshaft 28, the recess 49- extends to the lower end of the camshaft 28.

The weight plate 57 is provided on the upper surface of the input gear 29, and has elongated holes 64 and 64 parallel to each other formed at each end of the weight plate. The input gear 29 is supported on the input gear 29 by being fitted with a pair of support shafts 65 and 65. And this weight plate 57
is slidable along the upper surface of the input gear 29 in the direction toward or away from the camshaft 28, and the spring 61
biases the weight plate 57 in a direction toward the camshaft 28.

As shown by solid lines in each figure, when the camshaft 28 is rotating at a low speed, the weight plate 57 is urged by the spring 61 and moves toward the camshaft 28, and at this time, each cam Protrusion 47
．． 47 is cam-engaged with the decompression camshaft 52, and one end thereof is made to protrude from the outer surface of the camshaft 28.

Next, when the camshaft 28 rotates at a certain high speed, the single-weight plate 57 resists the spring 61 due to its centrifugal force and moves as indicated by the arrow in FIG.
The cam projections 47 are moved substantially in parallel in the direction shown by , and the cam projections 47 are accordingly retracted into the respective through holes 44 and 45.

(Effects of the Invention) According to the present invention, since the decompression camshaft is provided inside the camshaft and extends along the axis of the camshaft, the cam protrusion can be placed anywhere in the axial direction of the camshaft. However, the decompression camshaft can be extended to a desired length without being affected by the cam part formed on the outer circumference of the camshaft or other components, and can be cam-engaged with the cam projection.

Therefore, firstly, the degree of freedom in arranging the cam projections is increased.

Second, when a plurality of cam protrusions are provided along the camshaft, the decompression camshaft may be extended so as to engage each of these cam protrusions. One decompression camshaft can be cam-engaged with each of the cam projections. Therefore, the configuration can be simplified compared to the conventional method in which it was necessary to provide an independent decompression device corresponding to each cam protrusion.

[Brief explanation of the drawing]

1 to 6 show the first embodiment; FIG. 1 is a developed cross-sectional plan view, FIG. 2 is a partial cross-sectional plan view of the entire engine, and FIG. 3 is a view taken along the line III-III in FIG. 1. , FIG. 4 is an enlarged view taken along the line IV--IV in FIG. , FIGS. 7 to 10 are the second embodiment, and the seventh
The figure is a plan developed cross-sectional view, FIG. 8 is a cross-sectional view taken along the line ■-■ in FIG. 7, and FIG. 9 is an enlarged cross-sectional view taken along the line IX-IX in FIG.
FIG. 10 is an enlarged sectional view taken along the line X-X1il in FIG. 7. l...Engine, 3...Crankshaft, 14.Exhaust valve, 1
7. Valve mechanism, 28- Camshaft, 29 Input gear, 34 First exhaust cam section, 35 Second exhaust cam section,
43... Decompression device, 47... Cam protrusion, 51... Fitting hole, 52... Cam shaft for decompression, 57... Weight plate.

Claims (1)

[Claims] 1. A cam protrusion is provided which rotates together with the camshaft of the valve mechanism and can move outwardly from the outer surface of the camshaft, and when the camshaft rotates at a low speed, A decompression camshaft is provided which cam engages with the cam protrusion and projects the cam protrusion, and the protruding cam protrusion cam engages with the exhaust valve side as the camshaft rotates, opening the exhaust valve. In the engine decompression device, a fitting hole extending along the axis of the camshaft is formed inside the camshaft, and a decompression camshaft is fitted into the fitting hole so as to be rotatable about the axis. Engine decompression device. 2. The engine decompression device according to claim 1, wherein cam projections are provided at a plurality of locations along the axial direction of the camshaft.