EP0519494B1 - Valve operating mechanism for internal combustion engine - Google Patents
Valve operating mechanism for internal combustion engine Download PDFInfo
- Publication number
- EP0519494B1 EP0519494B1 EP92110385A EP92110385A EP0519494B1 EP 0519494 B1 EP0519494 B1 EP 0519494B1 EP 92110385 A EP92110385 A EP 92110385A EP 92110385 A EP92110385 A EP 92110385A EP 0519494 B1 EP0519494 B1 EP 0519494B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- valve
- speed
- low
- rocker arm
- engine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/26—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder
- F01L1/267—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder with means for varying the timing or the lift of the valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/26—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F1/00—Cylinders; Cylinder heads
- F02F1/24—Cylinder heads
- F02F1/42—Shape or arrangement of intake or exhaust channels in cylinder heads
- F02F1/4214—Shape or arrangement of intake or exhaust channels in cylinder heads specially adapted for four or more valves per cylinder
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F1/00—Cylinders; Cylinder heads
- F02F1/24—Cylinder heads
- F02F2001/244—Arrangement of valve stems in cylinder heads
- F02F2001/247—Arrangement of valve stems in cylinder heads the valve stems being orientated in parallel with the cylinder axis
Definitions
- the present invention relates to a valve operating mechanism for an internal combustion engine, including a camshaft rotatable in synchronism with the rotation of the internal combustion engine and having integral cams for operating a pair of intake or exhaust valves, and rocker arms angularly movably supported on a rocker shaft for opening and closing the intake or exhaust valves in response to rotation of the cams.
- Valve operating mechanisms used in internal combustion engines are generally designed to meet requirements for high-speed operation of the engines. More specifically, the valve diameter and valve lift are selected not to exert substantial resistance to the flow of an air-fuel mixture which is introduced through a valve into a combustion chamber at a rate for maximum engine power.
- those intake valves which are not operated in the low-speed range may remain at rest for a long period of time under a certain operating condition. If an intake valve remains at rest for a long time, carbon produced by fuel combustion tends to be deposited between the intake valve and its valve seat, causing the intake valve to stick to the valve seat. When the engine starts to operated in the high-speed range, the intake valve which has been at rest is forcibly separated from the valve seat. This causes the problem of a reduced sealing capability between the intake valve and the valve seat. Furthermore, fuel tends to be accumulated on the intake valve while it is held at rest, with the result that when the intake valve is opened, the air-fuel mixture introduced thereby is excessively enriched by the accumulated fuel.
- a valve operating mechanism for operating a valve of an internal combustion engine comprising:
- the present invention is characterised over this prior art in that said biasing means comprises lifter means urged by a compression spring into abutment with the second rocker arm.
- valve operating mechanisms of figures 1-8 are included for explanatory purposes only.
- FIGS. 1 and 2 show a valve operating mechanism.
- the valve operating mechanism is incorporated in an internal combustion engine including a pair of intake valves 1a, 1b in each engine cylinder for introducing an air-fuel mixture into a combustion chamber defined in an engine body.
- the valve operating mechanism comprises a camshaft 2 rotatable in synchronism with rotation of the engine at a speed ratio of 1/2 with respect to the speed of rotation of the engine crankshaft.
- the camshaft 2 has a low-speed cam 3 and a high-speed cam 5 which are integrally disposed on the circumference of the camshaft 2.
- the valve operating mechanism also has a rocker shaft 6 extending parallel to the camshaft 2, and first and second rocker arms 7, 8 angularly movably supported on the rocker shaft 6 and held against the low-speed cam 3 and the high-speed cam 5, respectively, on the camshaft 2.
- the intake valves 1a, 1b are selectively operated by the first and second rocker arms 7, 8 actuated by the low- and high-speed cams 3, 5.
- the camshaft 2 is rotatably disposed above the engine body.
- the high-speed cam 5 is disposed in a position corresponding to an intermediate position between the intake valves 1a, 1b, as viewed in FIG. 2.
- the low-speed cam 3 is disposed in alignment with the intake valve 1a.
- the low-speed cam 3 has a cam lobe 3a projecting radially outwardly to a relatively small extent to meet low-speed operation of the engine
- the high-speed cam 5 has a cam lobe 5a projecting radially outwardly a greater extent than the cam lobe 3a to meet high-speed operation of the engine, with the cam lobe 5a also having a larger angular extent than the cam lobe 3a.
- the rocker shaft 6 is fixed below the camshaft 2.
- the first rocker arm 7 pivotally supported on the rocker shaft 6 is aligned with the low-speed cam 3, and the second rocker arm 8 pivotally supported on the rocker arm 6 is aligned with the high-speed cam 5.
- the rocker arms 7, 8 have on their upper surfaces cam slippers 10, 11 respectively, held in sliding contact with the cams 3, 5, respectively.
- the first and second rocker arms 7, 8 have arms 7a, 8a extending above the intake valves 1a, 1b, respectively.
- Tappet screws 12, 13 are adjustably threaded through the distal ends of the arms 7a, 8a and have tips engagable respectively with the upper ends of the valve stems of the intake valves 1a, 1b.
- Flanges 14, 15 are attached to the upper ends of the valve stems of the intake valves 1a, 1b.
- the intake valves 1a, 1b are normally urged to close the intake ports by compression coil springs 16, 17 disposed under compression around the valve stems between the flanges 14, 15 and the engine body.
- first and second rocker arms 7, 8 have confronting side walls held in sliding contact with each other.
- a selective coupling 21 is operatively disposed in and between the first and second rocker arms 7, 8 for selectively disconnecting the rocker arms 7, 8 from each other for relative displacement and also for interconnecting the rocker arms 7, 8 for their movement in unison.
- the selective coupling 21 comprises a piston 23 movable between a position in which it interconnects the first and second rocker arms 7, 8 and a position in which it disconnects the first and second rocker arms 7, 8 from each other, a circular stopper 24 for limiting the movement of the piston 23, and a coil spring 25 for urging the stopper 24 to move the piston 23 toward the position to disconnect the first and second rocker arms 7, 8 from each other.
- the first rocker arm 7 has a first guide hole 26 opening toward the second rocker arm 8 and extending parallel to the rocker shaft 6.
- the first rocker arm 7 also has a smaller-diameter hole 28 near the closed end of the first guide hole 26, with a step or shoulder 27 being defined between the smaller-diameter hole 28 and the first guide hole 26.
- the piston 23 is slidably fitted in the first guide hole 26.
- the piston 23 and the closed end of the smaller-diameter hole 28 define therebetween a hydraulic pressure chamber 29.
- the first rocker arm 7 has a hydraulic passage 30 defined therein in communication with the hydraulic pressure chamber 29.
- the rocker shaft 6 has a hydraulic passage 31 defined axially therein and coupled to a source (not shown) of hydraulic pressure through a suitable hydraulic pressure control mechanism.
- the hydraulic passages 30, 31 are held in communication with each other through a hole 32 defined in a side wall of the rocker shaft 6, irrespective of how the first rocker arm 7 is angularly moved about the rocker shaft 6.
- the second rocker arm 8 has a second guide hole 35 opening toward the first rocker arm 7 in registration with the first guide hole 26 in the first rocker arm 7.
- the circular stopper 24 is slidably fitted in the second guide hole 35.
- the second rocker arm 8 also has a smaller-diameter hole 37 near the closed end of the second guide hole 35, with a step or shoulder 36 defined between the second guide hole 35 and the smaller-diameter hole 37 for limiting movement of the circular stopper 24.
- the second rocker arm 8 also has a through hole 38 defined coaxially with the smaller-diameter hole 37.
- a guide rod 39 joined integrally and coaxially to the circular stopper 24 extends through the hole 38.
- the coil spring 25 is disposed around the guide rod 39 between the stopper 24 and the closed end of the smaller-diameter hole 37.
- the piston 23 has an axial length selected such that when one end of the piston 23 abuts against the step 27, the other end thereof is positioned just between and hence lies flush with the sliding side walls of the first and second rocker arms 7, 8, and when the piston 23 is moved into the second guide hole 35 until it displaces the stopper 24 into abutment against the step 36, said one end of the piston 23 remains in the first guide hole 26 and hence the piston 23 extends between the first and second rocker arms 7, 8.
- the piston 23 is normally urged toward the second rocker arm 8 under the resiliency of a coil spring 33 disposed in the hydraulic pressure chamber 29 and acting between the piston 23 and the closed bottom of the smaller-diameter hole 28.
- the resilient force of the spring 33 set under compression in the hydraulic pressure chamber 29 is selected to be smaller than that of the spring 25 set in place under compression.
- the selective coupling 21 is actuated to disconect the first and second rocker arm 7, 8 from each other as illustrated in FIG. 4. More specifically, the hydraulic pressure is released by the hydraulic pressure control mechanism from the hydraulic pressusre chamber 29, thus allowing the stopper 24 to move toward the first rocker arm 7 under the resiliency of the spring 25 until the piston 23 abuts against the step 27.
- the piston 23 engages the step 27 the mutually contacting ends of the piston 23 and the stopper 24 lie flush with the sliding side walls of the first and second rocker arms 7, 8. Therefore, the first and second rocker arms 7, 8 are held in mutually sliding contact for relative angular movement.
- the intake valve 1a alternately opens and closes the intake port at the valve timing and valve lift according to the profile of the low-speed cam 3
- the intake valve 1b alternately opens and closes the intake port at the valve timing and valve lift according to the profile of the high-speed cam 5.
- the intake valves 1a, 1b are operated at different valve timings and lifts, the turbulence of the air-fuel mixture in the combustion chamber is increased for greater resistance against a reduction in the density of the air-fuel mixture. This also helps improve fuel economy.
- the first and second rocker arms 7, 8 are interconnected by the selective coupling 21, as shown in FIG. 3. More specifically, the hydraulic pressure chamber 29 of the selective coupling 21 is supplied with hydraulic pressure to cause the piston 23 to push the stopper 24 into the second guide hole 35 against the resiliency of the spring 25 until the stopper 24 engages the step 36.
- the first and second rocker arms 7, 8 are now connected to each other for angular movement in unison.
- the intake valves 1a, 1b alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the high-speed cam 5. The intake efficiency is now increased for higher engine output power and torque.
- the intake valves 1a, 1b are operated at all times. Therefore, no carbon will be deposited between the intake valves 1a, 1b and their valve seats, and no fuel will be accumulated on the intake valves 1a, 1b.
- FIGS. 5 and 6 are illustrative of a valve operating mechanism.
- the valve operating mechanism shown in FIGS. 5 and 6 differs from the valve operating mechanism of FIGS. 1 and 2 in that the first rocker arm 7 has a pair of arms 7a, 7b jointly shaped in a V, and the tappet screws 12, 13 are adjustably threaded through the distal ends of the arms 7a, 7b for engagement with the upper ends of the valve stems of the intake valves 1a, 1b.
- the second rocker arm 8 has no arm for directly acting on the intake valves 1a, 1b.
- a bottomed cylindrical lifter 19 is disposed in abutment against a lower surface of the second rocker arm 8.
- the lifter 19 is normally urged upwardly by a compression spring 20 of relatively weak resiliency interposed between the lifter 19 and the engine body for resiliently biasing the cam slipper 11 of the second rocker arm 8 slidably against the high-speed cam 5.
- valve operating mechanism shown in FIGS. 5 and 6 has a selective coupling 21 which, as shown in FIG. 7, is structurally identical to the selective coupling 21 shown in FIG. 3.
- valve operating mechanism of FIGS. 5 and 6 When the engine is to operate in a low-speed range, the selective coupling 21 is actuated to disconnect the first and second rocker arm 7, 8 from each other as illustrated in FIG. 8. The first and second rocker arms 7, 8 are now held in mutually sliding contact for relative angular movement.
- the first rocker arm 7 is angularly moved in sliding contact with the low-speed cam 3, whereas the second rocker arm 8 is angularly moved in sliding contact with the high-speed cam 5. Therefore, the intake valves 1a, 1b are actuated by the respective arms 7a, 7b of the first rocker arm 7 to alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the low-speed cam 3. Since the second rocker arm 8 is disconnected from the first rocker arm 7, the angular movement of the second rocker arm 8 does not affect operation of the intake valves 1a, 1b. Any frictional loss of the valve operating mechanism is relatively low because the second rocker arm 8 is held in sliding contact with the high-speed cam 5 under the relatively small resilient force of the spring 20.
- the intake valves 1a, 1b alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the low-speed cam 3. Accordingly, the air-fuel mixture flows into the combustion chamber at a rate suitable for the low-speed operation of the engine, resulting in improved fuel economy and prevention of knocking.
- first and second rocker arms 7, 8 are interconnected by the selective coupling 21, as shown in FIG. 7.
- the first rocker arm 7 is now caused to swing in unison with the second rocker arm 8 which is held in sliding contact with the high-speed cam 5.
- the intake valves 1a, 1b are operated by the arms 7a, 7b of the first rocker arm 7 to alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the high-speed cam 5.
- the intake efficiency is now increased for higher engine output power and torque.
- FIG. 9 shows a valve operating mechanism according to an embodiment of the present invention.
- the valve operating mechanism of FIG. 9 is essentially the same as those shown in FIGS. 5 to 8 except that it operates only one intake valve 1 per engine cylinder.
- the first rocker arm 7 has an arm 7c for operating the intake valve 1.
- exhaust valves may also be operated by the valve operating mechanisms according to the present invention.
- unburned components due to exhaust gas turbulence can be reduced in low-speed operation of the engine, whereas high engine output power and torque can be generated by reducing resistance to the flow of an exhaust gas from the combustion chamber in high-speed operation of the engine.
- the present invention provides valve operating mechanism for an internal combustion engine, which increases the turbulence of an air-fuel mixture in the combustion chamber during low-speed operation of the engine for improving fuel economy and increasing resistance against a reduction in the density of the air-fuel mixture, and which is designed to meet the problems which would otherwise occur due to an intake valve being continuously closed.
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- Valve-Gear Or Valve Arrangements (AREA)
Description
- The present invention relates to a valve operating mechanism for an internal combustion engine, including a camshaft rotatable in synchronism with the rotation of the internal combustion engine and having integral cams for operating a pair of intake or exhaust valves, and rocker arms angularly movably supported on a rocker shaft for opening and closing the intake or exhaust valves in response to rotation of the cams.
- Valve operating mechanisms used in internal combustion engines are generally designed to meet requirements for high-speed operation of the engines. More specifically, the valve diameter and valve lift are selected not to exert substantial resistance to the flow of an air-fuel mixture which is introduced through a valve into a combustion chamber at a rate for maximum engine power.
- If an intake valve is actuated at constant valve timing and valve lift throughout a full engine speed range from low to high speeds, then the speed of flow of an air-fuel mixture into the combustion chamber varies from engine speed to engine speed since the amount of air-fuel mixture varies from engine speed to engine speed. At low engine speeds, the speed of flow of the air-fuel mixture is lowered and the air-fuel mixture is subject to less turbulence in the combusion chamber, resulting in slow combustion therein. Therefore, the combustion efficiency is reduced and so is the fuel economy, and the knocking margin is lowered due to the slow combustion.
- One solution to the above problems is disclosed in Japanese Laid-Open Patent Publication No. 59(1984)-226216. According to the disclosed arrangement, some of the intake or exhaust valves remain closed when the engine operates at a low speed, whereas all of the intake or exhaust valves are operated, i.e., alternately opened and closed, during high-speed operation of the engine. Therefore, the valves are controlled differently in low- and high-speed ranges.
- In the prior valve operating mechanism described above, those intake valves which are not operated in the low-speed range may remain at rest for a long period of time under a certain operating condition. If an intake valve remains at rest for a long time, carbon produced by fuel combustion tends to be deposited between the intake valve and its valve seat, causing the intake valve to stick to the valve seat. When the engine starts to operated in the high-speed range, the intake valve which has been at rest is forcibly separated from the valve seat. This causes the problem of a reduced sealing capability between the intake valve and the valve seat. Furthermore, fuel tends to be accumulated on the intake valve while it is held at rest, with the result that when the intake valve is opened, the air-fuel mixture introduced thereby is excessively enriched by the accumulated fuel.
- According to FR-A-2 510 182 there is provided a valve operating mechanism for operating a valve of an internal combustion engine comprising:
- a camshaft rotatable in synchronism with rotation of the internal combustion engine and having a pair of low- and high-speed cams of different cam profile;
- a pair of first and second rocker arms operable selectively by said low- and high-speed cams for operating the valve according to the cam profiles of the cams; and
- coupling means operatively disposed between said first and second rocker arms and arranged to interconnect said first and second rocker arms in high-speed operation of the engine to effect operation of the valve by the high-speed cam, the coupling means being further arranged to disconnect said first and second rocker arms from each other for independent movement in low-speed operation of the engine, the second rocker arm being urged resiliently into sliding contact with said high-speed cam by biasing means and being operated by the high-speed cam during both high- and low-speed operation of the engine;
- wherein during said low-speed operation of the engine the first rocker arm is operated by the low-speed cam to effect operation of the valve according to the cam profile of said low-speed cam whereby the valve is not continuously closed; and
- wherein said valve operating mechanism has only two cams, only two rocker arms and only one valve.
- The present invention is characterised over this prior art in that said biasing means comprises lifter means urged by a compression spring into abutment with the second rocker arm.
- Some valve operating mechanisms will now be described by way of example and with reference to the accompanying drawings, in which:-
- FIG. 1 is a vertical cross-sectional view of a valve operating mechanism, the view being taken along line I - I of FIG. 2;
- FIG. 2 is a plan view of the valve operating mechanism shown in FIG. 1;
- FIG. 3 is a cross-sectional view taken along line III - III of FIG. 1, showing the first and second rocker arms interconnected;
- FIG. 4 is a cross-sectional view similar to FIG. 3, showing the first and second rocker arms disconnected from each other;
- FIG. 5 is a vertical cross-sectional view of a valve operating mechanism, the view being taken along line V - V of FIG. 6;
- FIG. 6 is a plan view of the valve operating mechanism shown in FIG. 5;
- FIG. 7 is a cross-sectional view taken along line VII - VII of FIG. 5, showing the first and second rocker arms interconnected;
- FIG. 8 is a cross-sectional view similar to FIG. 7, showing the first and second rocker arms disconnected from each other; and
- FIG. 9 is a plan view of a valve operating mechanism according to an embodiment of the present invention.
- The valve operating mechanisms of figures 1-8 are included for explanatory purposes only.
- Like or corresponding parts are denoted by like or corresponding reference characters throughout the views.
- FIGS. 1 and 2 show a valve operating mechanism. The valve operating mechanism is incorporated in an internal combustion engine including a pair of
intake valves - The valve operating mechanism comprises a
camshaft 2 rotatable in synchronism with rotation of the engine at a speed ratio of 1/2 with respect to the speed of rotation of the engine crankshaft. Thecamshaft 2 has a low-speed cam 3 and a high-speed cam 5 which are integrally disposed on the circumference of thecamshaft 2. The valve operating mechanism also has arocker shaft 6 extending parallel to thecamshaft 2, and first andsecond rocker arms rocker shaft 6 and held against the low-speed cam 3 and the high-speed cam 5, respectively, on thecamshaft 2. Theintake valves second rocker arms speed cams - The
camshaft 2 is rotatably disposed above the engine body. The high-speed cam 5 is disposed in a position corresponding to an intermediate position between theintake valves speed cam 3 is disposed in alignment with theintake valve 1a. The low-speed cam 3 has a cam lobe 3a projecting radially outwardly to a relatively small extent to meet low-speed operation of the engine, and the high-speed cam 5 has acam lobe 5a projecting radially outwardly a greater extent than the cam lobe 3a to meet high-speed operation of the engine, with thecam lobe 5a also having a larger angular extent than the cam lobe 3a. - The
rocker shaft 6 is fixed below thecamshaft 2. Thefirst rocker arm 7 pivotally supported on therocker shaft 6 is aligned with the low-speed cam 3, and thesecond rocker arm 8 pivotally supported on therocker arm 6 is aligned with the high-speed cam 5. Therocker arms surfaces cam slippers cams second rocker arms arms intake valves Tappet screws arms intake valves -
Flanges intake valves intake valves compression coil springs flanges - As shown in FIG. 4, the first and
second rocker arms selective coupling 21 is operatively disposed in and between the first andsecond rocker arms rocker arms rocker arms - The
selective coupling 21 comprises a piston 23 movable between a position in which it interconnects the first andsecond rocker arms second rocker arms second rocker arms - The
first rocker arm 7 has afirst guide hole 26 opening toward thesecond rocker arm 8 and extending parallel to therocker shaft 6. Thefirst rocker arm 7 also has a smaller-diameter hole 28 near the closed end of thefirst guide hole 26, with a step orshoulder 27 being defined between the smaller-diameter hole 28 and thefirst guide hole 26. The piston 23 is slidably fitted in thefirst guide hole 26. The piston 23 and the closed end of the smaller-diameter hole 28 define therebetween ahydraulic pressure chamber 29. - The
first rocker arm 7 has ahydraulic passage 30 defined therein in communication with thehydraulic pressure chamber 29. Therocker shaft 6 has ahydraulic passage 31 defined axially therein and coupled to a source (not shown) of hydraulic pressure through a suitable hydraulic pressure control mechanism. Thehydraulic passages hole 32 defined in a side wall of therocker shaft 6, irrespective of how thefirst rocker arm 7 is angularly moved about therocker shaft 6. - The
second rocker arm 8 has asecond guide hole 35 opening toward thefirst rocker arm 7 in registration with thefirst guide hole 26 in thefirst rocker arm 7. The circular stopper 24 is slidably fitted in thesecond guide hole 35. Thesecond rocker arm 8 also has a smaller-diameter hole 37 near the closed end of thesecond guide hole 35, with a step orshoulder 36 defined between thesecond guide hole 35 and the smaller-diameter hole 37 for limiting movement of the circular stopper 24. Thesecond rocker arm 8 also has a throughhole 38 defined coaxially with the smaller-diameter hole 37. Aguide rod 39 joined integrally and coaxially to the circular stopper 24 extends through thehole 38. The coil spring 25 is disposed around theguide rod 39 between the stopper 24 and the closed end of the smaller-diameter hole 37. - The piston 23 has an axial length selected such that when one end of the piston 23 abuts against the
step 27, the other end thereof is positioned just between and hence lies flush with the sliding side walls of the first andsecond rocker arms second guide hole 35 until it displaces the stopper 24 into abutment against thestep 36, said one end of the piston 23 remains in thefirst guide hole 26 and hence the piston 23 extends between the first andsecond rocker arms second rocker arm 8 under the resiliency of acoil spring 33 disposed in thehydraulic pressure chamber 29 and acting between the piston 23 and the closed bottom of the smaller-diameter hole 28. The resilient force of thespring 33 set under compression in thehydraulic pressure chamber 29 is selected to be smaller than that of the spring 25 set in place under compression. - Operation of the valve operating mechanism will be described with reference to FIGS. 3 and 4. When the engine is to operate in a low-speed range, the
selective coupling 21 is actuated to disconect the first andsecond rocker arm hydraulic pressusre chamber 29, thus allowing the stopper 24 to move toward thefirst rocker arm 7 under the resiliency of the spring 25 until the piston 23 abuts against thestep 27. When the piston 23 engages thestep 27, the mutually contacting ends of the piston 23 and the stopper 24 lie flush with the sliding side walls of the first andsecond rocker arms second rocker arms - With the first and
second rocker arms first rocker arm 7 is angularly moved in sliding contact with the low-speed cam 3, whereas thesecond rocker arm 8 is angularly moved in sliding contact with the high-speed cam 5. Therefore, theintake valve 1a alternately opens and closes the intake port at the valve timing and valve lift according to the profile of the low-speed cam 3, and theintake valve 1b alternately opens and closes the intake port at the valve timing and valve lift according to the profile of the high-speed cam 5. - Since the
intake valves - For high-speed operation of the engine, the first and
second rocker arms selective coupling 21, as shown in FIG. 3. More specifically, thehydraulic pressure chamber 29 of theselective coupling 21 is supplied with hydraulic pressure to cause the piston 23 to push the stopper 24 into thesecond guide hole 35 against the resiliency of the spring 25 until the stopper 24 engages thestep 36. The first andsecond rocker arms - Inasmuch as the
second rocker arm 8 held in sliding contact with the high-speed cam 5 swings to a greater extent than thefirst rocker arm 7, thefirst rocker arm 7 is caused to swing with thesecond rocker arm 8. Therefore, theintake valves speed cam 5. The intake efficiency is now increased for higher engine output power and torque. - In the low- and high-speed ranges of engine operation, the
intake valves intake valves intake valves - FIGS. 5 and 6 are illustrative of a valve operating mechanism. The valve operating mechanism shown in FIGS. 5 and 6 differs from the valve operating mechanism of FIGS. 1 and 2 in that the
first rocker arm 7 has a pair ofarms arms intake valves second rocker arm 8 has no arm for directly acting on theintake valves cylindrical lifter 19 is disposed in abutment against a lower surface of thesecond rocker arm 8. Thelifter 19 is normally urged upwardly by acompression spring 20 of relatively weak resiliency interposed between thelifter 19 and the engine body for resiliently biasing thecam slipper 11 of thesecond rocker arm 8 slidably against the high-speed cam 5. - The valve operating mechanism shown in FIGS. 5 and 6 has a
selective coupling 21 which, as shown in FIG. 7, is structurally identical to theselective coupling 21 shown in FIG. 3. - Operation of the valve operating mechanism of FIGS. 5 and 6 will be described with reference to FIGS. 7 and 8. When the engine is to operate in a low-speed range, the
selective coupling 21 is actuated to disconnect the first andsecond rocker arm second rocker arms - With the first and
second rocker arms first rocker arm 7 is angularly moved in sliding contact with the low-speed cam 3, whereas thesecond rocker arm 8 is angularly moved in sliding contact with the high-speed cam 5. Therefore, theintake valves respective arms first rocker arm 7 to alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the low-speed cam 3. Since thesecond rocker arm 8 is disconnected from thefirst rocker arm 7, the angular movement of thesecond rocker arm 8 does not affect operation of theintake valves second rocker arm 8 is held in sliding contact with the high-speed cam 5 under the relatively small resilient force of thespring 20. - During low-speed operation of the engine, therefore, the
intake valves speed cam 3. Accordingly, the air-fuel mixture flows into the combustion chamber at a rate suitable for the low-speed operation of the engine, resulting in improved fuel economy and prevention of knocking. - For high-speed operation of the engine, the first and
second rocker arms selective coupling 21, as shown in FIG. 7. Thefirst rocker arm 7 is now caused to swing in unison with thesecond rocker arm 8 which is held in sliding contact with the high-speed cam 5. - The
intake valves arms first rocker arm 7 to alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the high-speed cam 5. The intake efficiency is now increased for higher engine output power and torque. - FIG. 9 shows a valve operating mechanism according to an embodiment of the present invention. The valve operating mechanism of FIG. 9 is essentially the same as those shown in FIGS. 5 to 8 except that it operates only one
intake valve 1 per engine cylinder. Thefirst rocker arm 7 has anarm 7c for operating theintake valve 1. - While the
intake valves - It will thus be seen that the present invention, at least in its preferred forms, provides valve operating mechanism for an internal combustion engine, which increases the turbulence of an air-fuel mixture in the combustion chamber during low-speed operation of the engine for improving fuel economy and increasing resistance against a reduction in the density of the air-fuel mixture, and which is designed to meet the problems which would otherwise occur due to an intake valve being continuously closed.
Claims (5)
- A valve operating mechanism for operating a valve (1) of an internal combustion engine comprising:a camshaft (2) rotatable in synchronism with rotation of the internal combustion engine and having a pair of low- and high-speed cams (3,5) of different cam profile;a pair of first and second rocker arms (7,8) operable selectively by said low- and high-speed cams for operating the valve according to the cam profiles of said cams; andcoupling means (21) operatively disposed between said first and second rocker arms and arranged to interconnect said first and second rocker arms in high-speed operation of the engine to effect operation of the valve by the high-speed cam, the coupling means being further arranged to disconnect said first and second rocker arms from each other for independent movement in low-speed operation of the engine, the second rocker arm being urged resiliently into sliding contact with said high-speed cam by biasing means (19) and being operated by the high-speed cam during both high- and low-speed operation of the engine;wherein during said low-speed operation of the engine the first rocker arm (7) is operated by the low-speed cam (3) to effect operation of the valve (1) according to the cam profile of said low-speed cam (3), whereby the valve is not continuously closed; andwherein said valve operating mechanism has only two cams (3,5), only two rocker arms (7,8) and only one valve (1);characterised in that said biasing means comprises lifter means (19) urged by a compression spring (20) into abutment with the second rocker arm (8).
- A valve operating mechanism as claimed in claim 1, wherein said lifter means (19) is cylindrical with a closed end in abutment with said second rocker arm (8), said compression spring (20) acting against said closed end.
- A valve operating mechanism as claimed in claim 1 or 2, wherein said first rocker arm (7) is held in sliding contact with said low-speed cam (3) and said first rocker arm has an arm for operating said valve (1).
- A valve operating mechanism as claimed in any preceding claim, wherein during said low-speed operation of said engine, said first and second rocker arms (7,8) are held in mutually sliding contact for relative angular movement.
- A valve operating mechanism as claimed in any preceding claim, wherein said coupling means comprises a selective coupling (21) composed of a first guide hole (26) defined in said first rocker arm (7), a second guide hole (35) defined in said second rocker arm (8) in registration with said first guide hole, a piston (23) slidably fitted in said first guide hole (26), a spring (25) disposed in said second guide hole (35) for normally urging said piston (23) into said first guide hole (26), and means (29,30,31,32) for applying hydraulic pressure to said piston (23) to move the same to a position between said first and second guide holes (26,35) against the resiliency of said spring (25).
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP92110385A EP0519494B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP86307548A EP0262269B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
EP92110385A EP0519494B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
Related Parent Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86307548A Division-Into EP0262269B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
EP86307548A Division EP0262269B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
EP86307548.7 Division | 1986-10-01 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0519494A1 EP0519494A1 (en) | 1992-12-23 |
EP0519494B1 true EP0519494B1 (en) | 1997-06-11 |
Family
ID=8196165
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86307548A Expired - Lifetime EP0262269B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
EP92110385A Expired - Lifetime EP0519494B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86307548A Expired - Lifetime EP0262269B1 (en) | 1986-10-01 | 1986-10-01 | Valve operating mechanism for internal combustion engine |
Country Status (3)
Country | Link |
---|---|
EP (2) | EP0262269B1 (en) |
DE (2) | DE3687661T2 (en) |
ES (2) | ES2037007T3 (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB9003603D0 (en) * | 1990-02-16 | 1990-04-11 | Lotus Group Plc | Cam mechanisms |
ES2068571T5 (en) * | 1990-02-16 | 1998-09-16 | Lotus Group Ltd | VALVE CONTROL MEANS. |
US5253621A (en) * | 1992-08-14 | 1993-10-19 | Group Lotus Plc | Valve control means |
AU657040B2 (en) * | 1992-02-28 | 1995-02-23 | Mitsubishi Jidosha Kogyo Kabushiki Kaisha | Valve-moving apparatus for internal combustion engine |
JP4752949B2 (en) * | 2009-05-28 | 2011-08-17 | トヨタ自動車株式会社 | Variable valve operating device for internal combustion engine |
WO2011064852A1 (en) | 2009-11-25 | 2011-06-03 | トヨタ自動車株式会社 | Variable valve device for internal combustion engine |
WO2015097709A1 (en) * | 2013-12-27 | 2015-07-02 | DONGA, Rajendrabhai Vallabhbhai | Improved valve mechanism for internal combustion engines |
WO2015097710A1 (en) * | 2013-12-27 | 2015-07-02 | DONGA, Rajendrabhai Vallabhbhai | Gear mechanism for transmission of engine valve |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0213759A1 (en) * | 1985-07-31 | 1987-03-11 | Honda Giken Kogyo Kabushiki Kaisha | Valve operating mechanism |
EP0213758A1 (en) * | 1985-07-31 | 1987-03-11 | Honda Giken Kogyo Kabushiki Kaisha | Valve operating mechanism |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3119133A1 (en) * | 1981-05-14 | 1982-12-02 | Anton Ing.(grad.) 8492 Furth Pfeifer | Valve control device for four-stroke internal combustion engines |
FR2510182A1 (en) * | 1981-07-27 | 1983-01-28 | Renault | Adjustable engine rocker gear - has auxiliary rockers giving higher lift sliding into engagement with main rockers |
AU551310B2 (en) * | 1983-06-06 | 1986-04-24 | Honda Giken Kogyo Kabushiki Kaisha | Valve actuating mechanism |
JPS6131613A (en) * | 1984-07-24 | 1986-02-14 | Honda Motor Co Ltd | Valve operation pause device for internal-combustion engine |
US4726332A (en) * | 1985-04-26 | 1988-02-23 | Mazda Motor Corporation | Variable valve mechanism for internal combustion engines |
-
1986
- 1986-10-01 DE DE19863687661 patent/DE3687661T2/en not_active Expired - Lifetime
- 1986-10-01 DE DE19863650636 patent/DE3650636T2/en not_active Expired - Lifetime
- 1986-10-01 EP EP86307548A patent/EP0262269B1/en not_active Expired - Lifetime
- 1986-10-01 EP EP92110385A patent/EP0519494B1/en not_active Expired - Lifetime
- 1986-10-01 ES ES86307548T patent/ES2037007T3/en not_active Expired - Lifetime
-
1992
- 1992-06-19 ES ES92110385T patent/ES2102427T3/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0213759A1 (en) * | 1985-07-31 | 1987-03-11 | Honda Giken Kogyo Kabushiki Kaisha | Valve operating mechanism |
EP0213758A1 (en) * | 1985-07-31 | 1987-03-11 | Honda Giken Kogyo Kabushiki Kaisha | Valve operating mechanism |
Also Published As
Publication number | Publication date |
---|---|
EP0262269B1 (en) | 1993-01-27 |
EP0262269A1 (en) | 1988-04-06 |
ES2102427T3 (en) | 1997-08-01 |
ES2037007T3 (en) | 1993-06-16 |
EP0519494A1 (en) | 1992-12-23 |
DE3650636T2 (en) | 1997-09-25 |
DE3650636D1 (en) | 1997-07-17 |
DE3687661D1 (en) | 1993-03-11 |
DE3687661T2 (en) | 1993-05-27 |
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