Internal combustion engine with decompressor

Abstract: A decompressor disposed to start an engine by a recoil starter and at this time compression pressure within a cylinder is adapted to escape therefrom, in which a decompression valve of the decompressor is disposed vertically with respect to a crank shaft or within a crank casing, so that a decompression valve does not laterally project from the cylinder and does not interfere with a cowling, whereby a compact engine is laid out, and also an interlocking mechanism of the decompression valve with the recoil starter becomes simple. Furthermore, a cam at the recoil reel is made variable correspondingly to the kind of engine so that the decompression timing during the starting is made variable so as to obtain the most suitable starting mechanism.

Description: FIELD OF THE INVENTION The present invention relates to an internal combustion engine according to the preamble portion of Claim 1 started by a recoil starter, in which, when the recoil starter is actuated, a decompression valve is automatically opened. BACKGROUND OF THE INVENTION Conventionally, when a diesel engine is to be started, in order to rotate a crank shaft with ease, it has been well-known that a decompressor is provided so that the crank shaft is rotated in the incompressible state and, when a flywheel increases its torque, a decompression valve is open to start the engine, and that a recoil starter for the internal combustion engine is adapted to start the engine and, when a recoil reel of the recoil starter is rotated, the decompression valve is open. For example, the former is disclosed in the Japanese Utility Model Publication No. Hei 6-49900 and the USP No. 5116287 and the latter in the Japanese Patent Laid-Open No. Hei 2-176159. As the conventional technique, in order that the decompressor is mounted to a cylinder head at the engine and connected with the recoil starter so as to automatically open the decompression valve when a starting cord is pulled, a coupling mechanism, such as a link; is required to be interposed between the decompression valve and the recoil starter, and the link mechanism interposed between the cylinder head and the recoil starter becomes larger and a space for housing the link mechanism therein becomes larger, resulting in that the engine as a whole becomes larger. As shown in Fig. 10, when the decompression valve 1 is disposed at the lateral side of a cylinder 3 in leration of extending in parallel to a crank shaft 2, the decompressor largely projects from the cylinder 3, whereby a cowling 4 must largely be changed in design. When a lever or the like for transmitting the motion of recoil starter to the decompressor is provided at the recoil casing, a cutout must be provided thereon. Dust or the like i's liable to enter into the recoil casing from the cutout and inconvenience is caused in the rotation or sliding motion of the recoil. Also, if such transmitting device is provided, the entire recoil starter should be large-sized and the entire engine should be large-sized by these accessories. A prior art internal combustion engine with the features of the preamble portion of claim 1 is described in US-A-5 116 287. This engine is provided with a decompressor valve which is attached to the engine cylinder so as to be perpendicular to the axis of the cylinder. The decompressor valve is switched by an operating rod which is extended from a recoil reel in perpendicular to a crankshaft. The operating rod is laterally moved in parallel to the crankshaft via a mechanical link structure connected to the movable recoil reel. This solution requires a considerable space for the lateral movement of the operating rod and a comparatively complicated structure. In JP-A-07 011 923 there is disclosed another internal combustion engine with a decompressor valve which is operated by the movement of an operating rod in perpendicular to a crankshaft. The operating rod is moved by means of cam arrangement that is interposed between the recoil reel and the operating rod. The cam arrangement comprises a pair of balls arranged in a slant hole of a balance weight such that they push a disc due to centrifugal forces which in return rotates a cam member engaged with the rod. This structure, too, is comparatively complicated and requires a large number of parts. SUMMARY OF THE INVENTION The object of the present invention is to, provide an internal combustion engine with a simplified structure of the means for operating a decompression valve. According to the present invention there is provided an internal combustion engine as defined in claim 1. The present invention has been designed that a recoil starter can start the engine and that a decompression valve is disposed in a cylinder head with an operating rod thereof projecting downward towards the crank casing. When the engine starts, the decompression valve is opened following the rotation of the recoil reel so that a crank shaft can be rotated with ease after the compression pressure in the cylinder is released. Accordingly, when the starting cord is pulled and the recoil reel is rotated to start the engine, an operating rod is pressed to push open the decompression valve and-the crank shaft easily rotates to start the engine. The operating rod for operating the decompression valve and the decompression valve do not extend in parallel to the crank shaft, but are disposed vertically, whereby an operating portion of the decompression valve does not laterally project from the cylinder to thereby obtain an engine of compact type. Also, the operating rod for connecting the recoil starter and decompression valve is disposed within a cowling to prevent dust from entering into the operating portion, thereby enabling the starting operation to be stabilized. In order to push the operating rod to open the decompression valve, a cam provided at the lateral side of the recoil reel is variable corresponding to the kind of the engine, thereby enabling a suitable recoil starter to be constructed. The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially sectional front view of an engine of a first embodiment in which a decompressor of the present invention is disposed. Fig. 2 is a partially side view of the same, Fig. 3 is a partially sectional view looking in the direction of the arrows A-A in Fig. 2, Fig. 4 is a side view of a recoil reel, Fig. 5 is a sectional view looking in the direction of the arrows B-B in Fig. 4, Fig. 6 is a partially sectional front view of an engine of a second embodiment in which a decompressor of the present invention is disposed, Fig. 7 is a partially sectional front view of an engine of a third embodiment of the same, Fig. 8 is an enlarged view of a decompression valve and a transmitting lever in Fig. 7, Fig. 9 is a partially sectional front view of an engine in which a decompressor is disposed differently, and Fig. 10 is a partially sectional side view of the engine disposing the conventional decompressor. DESCRIPTION OF THE PREFERRED EMBODIMENT In Figs. 1 through 5, explanation will be given on the first embodiment of the present invention. An engine E is so constructed that a cylinder 11 is fixedly loaded on a crank casing 10, a crank shaft 12 is rotatably horizontally supported through bearings in the crank casing 10, a piston 13 is inserted into the cylinder 11 vertically with respect to the crank shaft 12, and the piston 13 and crank shaft 12 are rotatably connected with each other through a connecting rod 14. The crank shaft 12 fixes at one axial end thereof a pulley and a flywheel( not shown) for taking out power and at the other axial end a starter.pulley 15. Meanwhile, the spaces above and at the lateral side of the cylinder 11 are covered by a cowling 16, are coil casing 17 is fixed to the lower portion thereof, the recoil casing 17 houses therein a recoil starter S, a support shaft 17a projects inwardly from the inner surface of the recoil casing 17 in relation of coinciding with the axis of the crank shaft 12, a recoil reel 20 is rotatably pivoted onto the support shaft 17a, and a starting cord 21 is wound around the recoil reel 20 and one end of the cord 21 is fixed to the recoil reel 20 and the other end is taken out from the recoil casing 17 to fix a handle ( not shown). A spring 22 is interposed between the outside surface of the recoil reel 20 and the inner surface of the recoil casing 17 so as to bias the recoil reel 20 in the direction of winding up the starting cord 21. At the axial center of the inner surface of the recoil reel 20 is disposed a slidable member 23 having a cam, so that, when the recoil reel 20 is rotated by pulling the starting cord 21, the slidable member 23 is adapted to slide toward the crank shaft 12 by means of the cam. Furthermore, between the inner surface of the slidable member 23 and the side surface of the starter pulley 15 is formed a one-way clutch, such as teeth or ratchets, whereby the recoil starter S of a pending type. In the recoil starter S of such construction, when the starting cord 21 is pulled, the recoil reel 20 is rotated to push the cam and the slidable member 23 slides toward the starter pulley 15, whereby the slidable member 23 engages with the starter pulley 15 to enable the crank shaft 12 to rotate. After the engine starts, the starter pulley 15 idles with respect to the recoil reel 20 through the one-way clutch, the recoil reel 20 being reversely rotated by the spring 22 so that the starting cord 21 is wound and the slidable member 23 slides toward the recoil reel 20. The decompressor of the present invention is interposed between the cylinder 11 and the recoil starter S, and, as shown in Figs. 1 through 3, is so constructed that a decompression port 11a is open at the side surface of the cylinder, the outside thereof is closed by a plug 24, at the cylinder 11 is formed a valve insertion bore llb slantwise inwardly upwardly extending toward the decompression port 11a, the valve insertion bore 11b communicates with a crank housing room 25 through a communicating bore 11c, a decompression valve 26 is inserted into the valve insertion bore 11b, and a valve operating rod 26a projects downwardly from the decompression valve 26, which is permanently closed and is open by pressing the operating rod 26a, so that, when the decompression valve 26 is opened by pressing the operating rod 26a, the decompression port 11a communicates with the communicating bore 11c to escape pressure from the cylinder into the crank casing 10. In addition, the operating rod 26a is pointed at the lower end thereof corresponding to an abutting surface. The operating rod 26a is so disposed that the lower end thereof can abut against cams 20a formed at the inner surface of the recoil reel 20 (at a side of crank shaft). The cams 20a, as shown in Figs. 4 and 5, project from the side surface of recoil reel 20 and are regularly spaced apart on the same circumference, (four cams 20a being disposed at every angle of 90° in this embodiment, where the number and disposing positions of the projections are not limited. As shown in the second embodiment in Fig.6, the cams 20a are changed in formation so as to be slanted cams 20a' and the recoil reel 20 is exchanged to change the cams 20a in formation or arrangement, whereby the movement of the operating rod 26a and the open-close timing thereof can be changed easily by mounting the recoil reel 20 easy to start to the engine E corresponding to the kind thereof. In addition, in Fig. 6, like elements corresponding to those in Fig. 1 are indicated by like reference numerals and explanation thereof will be omitted. In such construction, in the case that the engine E is started, when the starting cord 21 is pulled, the recoil reel 20 is rotated to slide toward the crank shaft 12 so as to rotate the crank shaft 12,and simultaneously the cam 20a abuts against the lower end of the operating rod 26a to push up the rod 26a and the decompression valve 26 is opened, so that, when the piston 13 lifts, the inner volume of the cylinder 11 is compressed,but the resulting pressure can escape into the crank casing 10 through the decompression port 11a, decompression valve 26 and communicating bore 11c, and the crank shaft 12 is easy to rotate so as to obtain a torque when the starting cord 21 is fully pulled, whereby the crank shaft 12 can obtain the torque and the slidable member 23 moves toward the recoil casing 17. Hence, the decompression valve 26 closes, and the interior of the cylinder 11 is compressed to be heated to a high temperature and the engine is ignited to start. Next, explanation will be given on a third embodiment disposing the decompression valve 26 in accordance with Fig. 7, where like elements corresponding to those in the first embodiment are indicated by like reference numerals and explanation thereof is omitted. In the third embodiment, a decompression valve 26 is vertically disposed so that a decompression port 11a and a communicating bore 11c are closed or communicated therebetween in the same manner as the above-mentioned. An operating rod 26a abuts at the lower end thereof against a transmitting lever 27. In brief, as shown in Figs. 7 and 8, the transmitting lever 27 is inserted into the crank casing 10 from the lateral side thereof so that the transmitting lever 27 abuts at one axial end thereof against the side surface of the recoil reel 20, is slantwise cut at the other axial end to form a slanted portion 27a and inserted into the crank casing 10 in the relation that the lower end of the operating rod 26a abuts against the slanted portion 27a. Furthermore, the transmitting lever 27 is provided at the lower surface with a recess 27b and a check pin 29 is inserted therein from the lower surface of the crank casing 10 so as to prevent the transmitting lever 27 from escaping from the crank casing 10 and also to restrain the same from rotating. A return spring 28 is interposed between the crank casing 10 and a smaller diameter portion of the transmitting lever 27 and fitted thereon so as to bias the transmitting lever 27 to slide toward the recoil reel 20. In the above-mentioned structure, in the case that the engine starts, when the starting cord 21 is pulled, the recoil reel 20 rotates to slide toward the crank shaft 12 so as to abut at the side surface against the transmitting lever 27, and the slanted portion 27 a moves, whereby operating rod 21a is raised to open the decompression valve 26 and the decompression facilitates the rotation of crank shaft 12. Thereafter, the engine starts as the same as the above-mentioned. Next, explanation will be given of an arrangement which is not in accordance with the invention as claimed and which disposes the decompression valve in accordance with Fig. 9, where like elements corresponding to those in Fig.1 are indicated by like reference numerals and explanation thereof is omitted. In this example, a decompression valve 26 is disposed at the side surface of the crank casing 10 horizontally and in parallel to the crank shaft 12 so that an operating rod 26a is disposed to directly abut against the side surface of the recoil reel 20. The decompression valve 26 communicates at a secondary portion thereof with the interior of the crank casing 10 ( or the atmosphere) through a communicating bore 10a and at a primary portion with the piping through a communicating bore 10b. On the other hand, the decompression port 11a is not provided with the plug 24 and communicating bore 11c, but a check valve and a joint 31 are inserted into the depression port 11a so that the cylinder 11 and crank casing 10 communicate with each other through joints 30 and 31 and a pope 32. In such structure, in the case that the engine E starts, when the starting cord 21 is pulled, the recoil reel 20 rotates and slides toward the crank shaft 12 and abuts at the side surface against the operating rod 26a, so that the decompression valve 26 is opened. On the other hand, the check valve 33 can be opened by the compression pressure caused by lifting the piston 13 and the rotation of crank shaft 21, so that the compression pressure is released through the joint 31, pipe 32, joint 30 and decompression valve 26, so as to facilitate the rotation of crank shaft 12, and thereafter, the engine E starts to begin explosion, whereby the recoil reel 20 slides to close the decompression valve 26 and the pressure within the cylinder 11 enters into the piping between the check valve 33 and the decompression valve 26, and is restrained from entering into the cylinder by means of the check valve 33, whereby the pressure in the piping is kept high, in brief, a compression ratio does not lower. As the above-mentioned, the present invention is so designed that the decompression valve is disposed vertically with respect to the crank shaft or within the crank casing, thereby not projecting laterally of the cylinder. As the result, there is no need for changing the cowling in part to prevent interference with the valve, and also an interlocking mechanism of the decompression valve with the recoil starter is simple to construct, thereby enabling a compact engine to be laid out. Since the recoil starter is of a size in the direction of the crank shaft only for mounting parts required to the recoil starter,the engine can be kept in at least necessary thickness, and since the recoil casing requires no cutout, dust causing failure in the recoil starter is prevented from entering therein. Since the cam at the recoil reel is made variable correspondingly to the kind of engine, the timing of decompression during the starting is variable so as to enable the most suitable cam to be obtained and variation of the specification is easy.

Claims: An internal combustion engine (E) comprising: a cylinder (11) and a crank casing (10), wherein said crank casing (10) is provided with a crank shaft (12) which is disposed with its rotational axis perpendicular to a longitudinal axis of said cylinder (11) and with a recoil starter (S) which is disposed coaxial to said crank shaft (12), said recoil starter (S) including a recoil reel (20) which is disposed so as to be axially slidable towards said crank shaft (12) upon operation of the recoil starter (S), characterized in that said cylinder (11) is in communication with said crank casing (10) via a decompression port (11a), a valve insertion bore (llb) and a communication bore (11c) provided in a side wall of said cylinder (11), said valve insertion bore (llb) being interposed between said decompression port (11a) and said communication bore (11c) and receiving a decompression valve (26) having an operating rod (26a) coaxial with said decompression valve (26) and operable for selectively communicating said decompression port (11a) and said communication bore (11c) to let escape pressure from said cylinder (11) to said crank casing (10), said operating rod (26a) being disposed so as to project downward from said decompression valve (26) towards said crank casing (10), wherein a lower end of said operating rod (26a) is adapted to abut against a slanted surface or cam portion (20a;20a';27a) which is moved axially towards said crank shaft (12) together with said recoil reel (20) upon operation of the recoil starter (S), thereby pushing said operating rod (26a) to operate said decompression valve (26). The internal combustion engine of claim 1, wherein said slanted surface is formed on a cam portion (20a;20a') provided on an axial side surface of said recoil reel (20). The internal combustion engine of claim 1, wherein said slanted surface (27a) is formed on an axial end of a transmitting lever (27) slidably disposed in said crank casing (10) so as to abut against an axial side surface of said recoil reel (20) with its other axial end portion. The internal combustion engine as set forth in claim 2, wherein said cam portion (20a;20a') can be exchanged against a cam portion of a different arrangement and formation corresponding to the kind of said engine.

Inventors: HORIUCHI HIROSHI, MOMOSE YUICHI, USHIKOSHI TAKESHI, HORIUCHI, HIROSHI, MOMOSE, YUICHI, USHIKOSHI,TAKESHI
Applicants: ISHIKAWAJIMA SHIBAURA MACH, ISHIKAWAJIMA SHIBAURA MACHINERY CO., LTD.
Application year: 1997
Main classification: F02N3
IPC codes: F02N3, F02D13, F02F1, F01L13, F02D15, F02N99