GB2115871A

GB2115871A - I C engine valve gear with an hydraulic

Info

Publication number: GB2115871A
Application number: GB08301339A
Authority: GB
Inventors: Kazuharu Yamada; Katsujiro Sato; Hisashi Kodama
Original assignee: Aisin Seiki Co Ltd; Toyota Motor Corp
Current assignee: Toyota Motor Corp; Aisin Corp
Priority date: 1982-01-23
Filing date: 1983-01-18
Publication date: 1983-09-14
Also published as: DE3301982A1; GB2115871B; JPS58126408A; GB8301339D0

Abstract

An adjusting screw 19 is provided between a push rod 4 and a valve rocker arm 6. When the valve gear is assembled the dimensional tolerances of the engine parts can be taken up by adjustment of the screw 19 and the stroke of the hydraulic tappet thus minimized, enabling a more compact, lighter tappet to be used. <IMAGE>

Description

SPECIFICATION Valve system of an internal combustion engine The present invention relates to a valve system of an internal combustion engine, more particularly to a mechanism for adjusting the clearances among the valve, hydraulic valve lifter, and cam in a valve system with a hydraulic valve lifter.

Generally, in an internal combustion engine, it is necessary to provide valve clearances as a countermeasure against the difference between the thermal expansion of the cylinder heads and that of the valve system.

The clearances must be accurate or noise and power loss caused by escape of non-combusted gas will occur during engine running.

It is well known to provide a hydraulic valve lifter in the valve system of an internal combustion engine to constantly maintain the proper valve clearance during the valve system operation. Such a hydraulic valve lifter prevents noise and absorbs additional clearances caused by wear of the parts of the valve system over time, thereby enabling the valve system to operate stably.

A hydraulic valve lifter is fitted slidably in a through hole of a cylinder block. The upper end of the lifter is movably connected with the lower end of a push rod. The lower end of the lifter contacts a cam. The cam, which rotates by a crankshaft; therefore moves the hydraulic valve lifter up and down. This vertical motion of the hydraulic valve lifter is transmitted via the upper end of the push rod, to a valve rocker arm rotatably supported on a cylinder head and opens and shuts an engine valve according to the swing motion of the valve rocker arm.

The hydraulic valve lifter mainly consists of a body and a plunger slidably fitted inside the body. A ball check valve is provided on the lower end of the plunger. A spring is mounted between the lower surface of the plunger and the bottom of the body to push up the plunger. A reservoir in the plunger and a pressure chamber on the bottom of the body are filled with oil. Thus, if undesired clearance is created in the valve system, the plunger is pushed up against the body by the spring force to eliminate it. On the other hand, if the valve system becomes longer, the lifting distance of the plunger is shortened by exactly that amount. This enables smooth operation of the valve system.

One type of known hydraulic valve lifter is the so-called self-contained hydraulic valve lifter. The self-contained hydraulic valve lifter comprises a body, a plunger, and an elastic bag attached on the upper end of the plunger.

The vertical motion of the plunger causes the oil within the pressure chamber to pass in and out of the reservoir in the plunger. That oil motion in turn causes the elastic bag to expand and contract, i.e., to undergo a kind of "breathing" action.

Now then, the cylinder block, cylinder heads, cylinder head gaskets, and parts of the valve system unavoidably have dimensional tolerances due to their production processes.

Conventional hydraulic valve lifters do not comprise any mechanisms which can absorb those dimensional tolerances. Therefore, in addition to the adjusting clearance (usually + 0.5 to 1.0 mm) between the cam and the hydrqulic valve lifter, originally necessary to maintain the valve system in a constant condition, it is necessay to provide as the stroke of the hydraulic valve lifter an adjusting clearance (usually 3.0 to 4.0 mm) to absorb those dimensional tolerances. In the above-mentioned seal type hydraulic valve lifter, since the elastic bag "breathes" in order to absorb the inflow and outflow of oil to and from the reservoir along with the relative motion between the plunger and the body, the hydraulic valve lifter, must unavoidably be enlarged.

The resultant greater weight of this portion of the valve system acts as a restriction on the engine speed and obstructs the achievement of higher speed engines.

The present invention is presented to solve the above-mentioned problem in valve systems with hydraulic valve lifters.

The object of the present invention is to provide a valve system with a hydraulic valve lifter which can absorb the dimensional tolerances of the parts of the engine during engine assembly so as to keep the stroke of the hydraulic valve lifter at just the adjusting clearance originally necessary and which can be made compact and light.

According to the present invention, there is provided a valve system of an internal combustion engine comprising a hydraulic valve lifter fitted slidably in a through hole of a cylinder block and moving up and down due to contact at the lower end thereof with a cam rotated by a crankshaft; a push rod, the lower end of which is connected with the upper end of the hydraulic valve lifter; and a valve rocker arm supported rotatably on a cylinder head, an end of which is connected with the upper end of the push rod and another end of which is connected with the upper end of a valve rod. The characterizing feature is that there is provided an adjusting screw between the upper end of the push rod and the end of the valve rocker arm.

In the drawings: Figure 1 is a cross-section of a principal part of an internal combustion engine comprising a known valve system; Figure 2 is a schematic view of a known valve system; Figure 3 is a cross-section of a known selfcontained hydraulic valve lifter; and Figure 4 is a schematic view of an embodi ment of a valve system according to the present invention.

A known valve system and a hydraulic valve lifter used in the valve system will first be described so as to clarify the difference between the preferred embodiment of the present invention and the conventional technique.

The known valve system is used to control a suction valve and an exhaust valve of an internal combustion engine. The structure of the valve system is shown in Fig. 1.

A hydaulic valve lifter 1 is fitted slidably in a through hole 3 of a cylinder block 2. The upper end of the lifter is movably connected with the lower end 4a of a push rod 4. The lower end of the lifter contacts a cam 5. The cam 5, which rotates by a crankshaft, therefore moves the hydraulic valve lifter 1 up and down. This vertical motion of the hydraulic valve lifter 1 is transmitted via an upper end 4b of the push rod 4, to a valve rocker arm 6 rotatably supported on a cylinder head, opens and shuts an engine valve 7.

A known hydraulic valve lifter 1 is shown in Fig. 2. It mainly consists of a body 10 and a plunger 11 slidably fitted inside the body 10.

A ball check valve 1 3 is provided on the lower end of the plunger 11. A spring 14 is mounted between the lower end surface of the plunger 11 and the bottom of the body 10 to push up the plunger 11. A reservoir 1 5 in the plunger 11 and a pressure chamber 1 6 on the bottom of the body 10 are filled with oil.

The push rod 4 of the hydraulic valve lifter 1 is directly connected with the valve rocker arm 6. The vertical motion of the hydraulic valve lifter 1 due to the rotation of the cam 5 is thus transmitted to the engine valve 7 to open and shut the valve 7. In such a valve system, the stroke length a' and b' necessary to adjust the clearance of the hydraulic valve lifter 1, to absorb the dimensional tolerances of the cylinder head, the cylinder block, the cylinder head gasket (all not shown), the push rod 4, and so on during the assembly of those parts is greater than the length of the stroke originally necessary for adjusting the clearance of the hydraulic valve lifter 1. Consequently, the total length I' of the hydraulic valve lifter becomes longer and the weight becomes greater.

In Fig. 2, reference a' indicates the stroke necessary between a snap ring 1 7 and a push rod seat 1 8, the length of which is equal to the adjusting clearance for absorbing the dimensional tolerances of the cylinder part and the parts of the valve system plus the adjusting clearance originally necessary to compensate for wear of the cam. Reference b' indicates the stroke necessary between the lower end 1 a of the plunger 11 and the shoulder part 1 0a of the bottom of the body 10, the length of which is equal to the adjusting clearance for absorbing the dimensional tolerances of the cylinder part and the parts of the valve system plus the adjusting clearance originally necessary to compensate for the wear of the engine valve 7 and the valve seat.

A known self-contained hydraulic valve lifter 21 is shown in Fig. 3, this type of hydraulic valve lifter comprises a body 10, a plunger 11, and an elastic bag 1 2 attached on the upper end of the plunger 11. A reservoir 1 5 in the plunger 11 and a pressure chamber 1 6 on the bottom of the body 10 are filled up with oil. Other parts are the same as in Fig. 2 and are represented by the same reference numerals.

Fig. 4 shows the preferred embodiment of the present invention in reference to Fig. 2.

Parts the same as in Fig. 2 are represented by the same reference numerals. The valve system shown in Fig. 4 is characterized in that an adjusting screw 1 9 is attached in the connecting part of the push rod 4 and the valve rocker arm 6 by a lock nut 20.

According to the embodiment, the dimensional tolerances of the cylinder block, cylinder head, cylinder head gasket, and parts of the valve system can be absorbed. By turning the lock nut 20, the length of the adjusting screw 1 9 between the connecting part of the push rod 4 and the valve rocker arm 6 can be properly set during assembly of the valve system.The adjusting stroke necessary when assembling the hydraulic valve lifter in the valve system thus need not include the adjusting clearance for absorbing the dimensional tolerances of the parts and need only be the originally necessary adjusting clearance, i.e., the stroke a between the snap ring 1 7 and the push rod seat 18, for compensating for the wear of the cam, and the stroke b between the lower end 11 a of the plunger and the shoulder part 1 Oa of the bottom of the body, for compensating for the wear of the valve 7 and valve seat.

In contrast to the known valve system, the relations among a, a', b, bo' are as follows; a < a', b < b' and a + b < a' + b' Therefore, the total length I of this hydraulic valve lifter 1 is shorter than the total length I' of the known hydraulic valve lifter. The weight of the hydraulic valve lifter thus can be reduced from that of the known hydraulic valve lifter, even with the additional weight of the adjusting screw 1 9 and the lock nut 20. This eases the conventional limitation of the engine speed.

While the above explanation was made in reference to Fig. 2, it will be easily understood that the principle of the present invention can be also applied to the self-contained hydraulic valve lifter shown in Fig. 3, which would be even more advantageous. Further, it can be applied to the so-called overhead cam shaft type valve system in which the cam is mounted above the valve and the hydraulic valve lifter.

According to the present invention, the addition of a simple mechanism, i.e., an adjusting screw in the connecting part between the push rod of the hydraulic valve lifter and the valve rocker arm connected with the valve, makes it possible to keep the stroke of the hydraulic valve lifter to just the adjusting clearance originally necessary to keep the valve system in a constant condition and makes it possible to make the hydraulic valve lifter more compact and lighter in weight. This in turn enables higher speed engines.

Claims

1. A valve system of an internal combustion engine comprising: a hydraulic valve lifter fitted slidably in a through hole of a cylinder block and moving up and down due to contact at the lower end thereof with a cam rotated by a crankshaft; a push rod, the lower end of which is connected with the upper end of said hydraulic valve lifter; and a valve rocker arm supported rotatably on a cylinder head, an end of which is connected with the upper end of said push rod and another end of which is connected with the upper end of a valve rod; wherein there is provided an adjusting screw between the upper end of said push rod and the end of said valve rocker arm.

2. A valve system of an internal combustion engine according to claim 1, wherein said hydraulic valve lifter comprises: a body a plunger slidably fitted inside said body, an elastic bag attached on the upper end of said plunger, a ball check valve provided on the lower end of said plunger, a spring mounted between the lower surface of said plunger and the bottom of said body to push up said plunger, a reservoir between said elastic bag and the bottom of said plunger filled up with oil, and a pressure chamber between the lower end of said plunger and the bottom of said body filled up with oil.

3. A valve system of an internal combustion engine according to claim 1, wherein said hydraulic valve lifter comprises: a body, a plunger slidably fitted inside said body, a ball check valve provided on the lower end of said plunger, a spring mounted between the lower surface of said plunger and the bottom of said body to push up said plunger, and a pressure chamber on the bottom of said body filled with oil.

4. A valve system substantially as hereinbefore described with reference to, and as illustrated in, Fig. 4 of the accompanying drawings.