CA1316419C - Valve operating mechanism for internal combustion engine - Google Patents
Valve operating mechanism for internal combustion engineInfo
- Publication number
- CA1316419C CA1316419C CA000528462A CA528462A CA1316419C CA 1316419 C CA1316419 C CA 1316419C CA 000528462 A CA000528462 A CA 000528462A CA 528462 A CA528462 A CA 528462A CA 1316419 C CA1316419 C CA 1316419C
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- cam
- valves
- speed
- raised portion
- low
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- Valve Device For Special Equipments (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam.
The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.
A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam.
The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.
Description
~3164~
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VALVE OPERATING MECHANISM
-- ~OR I~TERNAL COMB~STIO~ ENGINE
BACKGRO~ND OF THE INVENTION
The present invention relates to a valve~--operating mechanism for an inter~na] 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 or cam followers angularly movable supported on a rocker shaft for opening and closing the intake or exhaust valves in response to rotation of the cams. ' -Japanese I.aid-Open Patent Publication No.
59(1984)-22621~, for exampler discloses a valve operating mechanism for use in an internal combustion engine having a plurality of intake or exhaust valves per engine cylinder.
, Some of the intake or exhaust valves remai'n cl-bsed when the engine operates at a low speed. If the intake or exhaust valves of a particular engine cylinder of a multicylinder internal combustion engine could be kept inoperative in order to cut off the operation of the particular engine cylinder, fuel consumption would be reduced by stopping the operation of the intake or exhaust valves of the particular engine cylinder while the engine operates in a low-speed range. ~owever, no satisfactory devices have been available in the past to achieve such a task.
- 1 - ~, G0/24 171~
SU~M~RY OF THE INVENTION 1316 ~19 It is an ob~ect Qf the present invention to provide a valve operating mechanism for in in~ernal combustion engine, which is of a relatively simple structure, for making the intake or exhaust valves of a particular engine cylincler inoperative for better fuel economy.
According to the present invention, there is provided a valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine, comprising a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam, a plurality of cam followers at ~east one of which slidably engages the cam for selectively operating the valves acccording to a cam profile of the cam, and means for selectively interconnecting and disconnecting the cam followers to operate . the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inope:rative by at least one of said cam followers engaging an annular raised portion on said camshaft.
The camshaft has one or two annular raised portions : in addition to the cam, and the cam followers include one or ~ two cam followers which slidably engage the raised portion or ~ portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed cams.
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Acool-d~ ,o .-ltl(,tJler aspect of the present 1n~enti.i, there `LS provlcled a valve c!peratir!g mechanism for operat1ng a pl~lrdlil y o:F valves of a particular cylinder of an internal combustiun enyirle~ compririlncJ: a camshaft carrying an -Innular ralsed portion for maintaining sa:id valves in a closed condition and cam means having a cam Profile for sequentia:Lly open~ g and closlng said valves, first cam follower means sli.clably engaging said raised por-tion and operati.vely connec-ting said valves thereto, second cam follower means slidably engaging said cam means, and means for selectively interconnecting and disconnecting said first and second cam followers a-t a predetermined conclition of engine operation whereby sai.d raised portion is effective to close said valves : during one range of engine operation ancl said cam means is effective to operàte said valves during another range of eng1ne operation.
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1 3 1 6 ~ ~ 9 6c~ 8 T~ne ahove and other ob~ects, features and advantages of the piesent invention wi3.1 ~ecome more apparent from the following description when takerl in con~unction wlth the accompanylng drawings in whlch preferred embodlments of the present lnvention are shown by way of 11 lu5t rative example.
BRI~F DFSCRIPTION_OF THE DRAWINGS
FIG. 1 is a vertlcal cross-sectiotlal vlew of a valve operatlng mechanlsm accordlng to an embodlment o~ the present inventlon, the view belng taken along llne I - I of FIG. Z;
FIG. 2 ls a plan view of the valve operatlng mechanism shown ln FIG. l;
FIG. 3 ls a cross-sectlonal vlew taken along line III
- III of FIG. 1, showlng first and second cam followers connected to each other;
FIG. 4 is a cross-sectional view simllar to FIG. 3, showlng the first and second cam followers disconnected from each other;
FIG. 5 ls a vertlcal cross-sectional vlew of a valve operating mechanlsm accordlng to another embodiment of the present inventlon, the vlew belng taken along line V - V of FIG. 6;
FIG. 6 is a plan view of the valve operatlng mechanlsm shown ln FIG. ~;
FIG. 7 ls a cross~sectlonal vlew taken along llne VII - VII of FIG. 6;
, 131~419 - G~7-0002 FIG. 8 is a cross-sectional view taken along line VIII - VIII of FIG. 5, showing first through third cam followers disconnected from each other;
FIG. 9 is a cross-sectional view similar to FIG.
8, showing the first through third cam followers interconnected;
FIG. 10 is a plan view of a valve operating mechanism according to still another embodiment of the present invention; and FIG. 11 is a plan view of a valve operating mechanism according to a still further embodiment of the present invention;
FIG. 12 is a cross-sectional view taken along llne XII - XII of FIG. 11;
FIG. 13 is a cross-sectional view taken along llne XIII - XIII of FIG. 12, showing a mechanism for actuating the valve operating mechanism of FIG. 11;
- FIG. 14 is a plan view of a valve operating mechanism according to a yet still further embodiment of the present invention; and ; FIG. 15 is a cross-sectional view similar to ; Figs. 8,9 and 13r showing a mechanism for actuating the valve operating mechanism of FIG.14-DESCRIPTION OF THE PREFERRED EMBODIMENTS
Like or corresponding parts are denoted by like or corresponding re~erence characters throughout several , views . -' . ' ' ~ `
~3~1g ~07~4-171 F~IGS. 1 and 2 show a valve operatlng mechanlsm according to an embodiment of the present invention. The valve operating mechanlsm ls lncorporated in an internal combustion engine for use with a particular engine cyllnder having a pair of intake valves la, lb ~or introducing an air-fuel mixture into a combustion chamber defined in an engine body.
The valve operating mechanlsm comprises a camshaft 2 rotatable in synchronism with rotation of the englne at a speed ratlo o~ 1/2 with respect to the speed of rotatlon of the engine. The camshaft 2 has an annular raised portion 3 and a cam 5 which are lntegrally disposed on the circumference of the camshaft 2. The valve operatlng mechanlsm also has a rocker shaft 6 e~tending parallel to the camshaft 2, and flrst and second rocker arms or cam followers 7, 8 angularly movably supported on the rocker shaft 6 and held against the cam 5 and the ralsed portion 3, respectlvely, on the camshaft 2. The intake valves laJ lb remain closed or inoperatlve by the ralsed portion 3 in a low-speed range of the engine.
The camshaft 2 ls rotatably dlsposed above the engine body. The ralsed portlon 3 ls dlsposed ln a posltion correspondlng to an intermedlate positlon between the intake valves la, lb, a.s viewed i.n FIG. 2. The cam 5 is pos1tloned substantially ln l~ne wlth the lntake valve lb. The raised portion 3 has a circumferentlal proflle ln the shape of a circle correspondlng to the base clrcle 5b o~ the cam 5. The cam 5 has a cam lobe 5a proJectlng radlally outwardly from the base clrcle 5b.
The rocker shaft 6 ls flxed below the camshaft ~.
The flrst cam follower 7 plvotally supported on the rocker shaft 6 ls aligned with the cam 5, and the second cam follower 8 pivotally supported on the rocker shaft 6 ls aligned with the ralse~ portlon 3. The cam followers 7, 8 have on their upper surfaces cam sllppers 7a, 8a, respectively, held in sllding contact wlth the cam 5 and the raised portlon 3, respectlvely.
The second cam follower 8 lncludes a palr of arms 8b, 8c having distal ends positicned above the lnt~ke valves la, lb, respectlvely. Tappet screws 12, 13 are threaded through the dlstal ends of the arms 8b, 8c and have tips engageable respectlvely wlth the upper ends of the valve stems of the lntake valves la, ~b.
Flanges 14, 15 are attached to the upper ends of the valve stems of the intake valves la, lb. The intake valves la, lb are normally urged to close the lntake ports by compresslon coll sprlngs 16, 17 dlsposed under compresslon around the valve stems between the flanges 14, 15 and the englne body.
A bottomed cyllndrlcal lifter 19 ls dlsposed ln abutment against a lower surface of the flrst cam follower 7.
; The llfter l9 ls normall~ urged upwardly by a compresslon sprlng 20 of relatlvely weak reslllency lnterposed between the lifter 19 and the engine body for reslliently biaslng the cam sllpper 7a of the flrst cam follower 7 slldably agalnst the cam 5.
As illustrated ln FIG. 3, the flrst and second cam followers 7, 8 have confrontlng slde walls held ln slldlng contact wlth each other. A selectlve coupllng 21 ls operatlvely dlsposed ln and between the flrst and second cam followers 7, 8 for selectlvely disconnectlng the cam followers 7, 8 from each other for relatlve dlsplacement and also for interconnectlng the cam followers 7, 8 for their movement in unison.
~ he selectlve coupling 21 comprlses a plston 23 movable between a posltlon in whlch lt interconnects the flrst and second cam followers 7, 8 and a positlon ln which lt dlsconnects the flrst and second cam followers 7, 8 from each ..
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~316~19 507~4-171~
other, a circular stopper 24 for limlting the movement of the plston 23, and a coil sprlng 25 for urging the stopper 24 to move the plston 23 toward the posltlon to dlsconnect the flrst and second cam followers 7, 8 from each other.
The second cam follower 8 has a flrst gulde hole 26 opening toward the first cam follower 7 and e~tendlng parallel to the rocker shaft 6. The second cam follower 8 also has a smaller-dlameter hole 28 near the closed end of the flrst gulde hole 26, wlth a step or shoulder 27 belng defi.ned betwe~n the smaller-dlarneter hole 28 and the flrst guide hole 26. The plston 23 ls slldably fltted in the first gulde hole 26. The piston 23, and the closed end of the smaller-dlameter hole 28 define therebetween a hydraullc pressure chamber 29.
: The second cam follower 8 has a hydraullc passage 30 deflned thereln ln communlcatlon with the hydraulic pressure chamber 29. The rocker shaft 6 has a hydraulic passage 31 defined axlally thereln and coupled to a source (not shown) of hydraullc pressure through a sultable hydraullc pressure . control mechanlsm. The hydraullc passages 30, 31 are held in communlcatlon wlth each other through a hole 32 deflned in a side wall of the rocker shaft 6, lrrespectlve of how the second cam follower 8 ls angularly moved about the rocker shaft 6.
The flrst cam follower 7 has a second guide hole 35 openlng toward the second cam follower 8 ln registratlon wlth the flrst gulde hole 26 ln the second cam follower 8. The clrcular stopper Z4 ls slidably fitted ln the second guide hole 35. The flrst cam follower 7 also has a smaller-dlameter hole 37 near the closed end of the second gulde hole 35, wlth a step : or shoulder 36 defined between the second gulde hole 35 and the smaller-dlameter hole 37 for llmiting movement of the circular stopper 24. The flrst cam follower 7 also has a through hole 38 defined coaxlally wlth the smaller-dlameter hole 37. A
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~316419 guide rod 39 ~olned lntegrall.y and coaxlally to the circular stopper 24 exten~s through the hole 38. The coll spring 25 ls disposed around the gulde rod 39 between the stopper 24 and the closed end of the smaller-dlameter hole 37.
The pis~on 23 has an axial length selected such that when one end of the plston 23 abuts agalnst the step 27, the other end thereof ls positloned ~ust between and hence lles flush wlth the slidlng side walls of the flrst and second cam followers 7, 8, and when the piston 23 ls moved lnto the second gulde hole 35 untll it dlsplaces the stopper 24 into abutment agalnst the step 36, sald one end of the plston 23 remalns in the flrst gulde hole 26 and hence the piston 23 extends between the flrst and second cam followers 7, 8. The piston 23 ls normally urged toward the first cam follower 7 under the reslllency of a coil spring 33 disposed in the hydraullc pressure chamber 29 and actlng between the plston 23 and the closed bottom of the smaller-diameter hole 28. The reslllent force of the spri.ng 33 set under compresslon ln the hydraullc pressure chamber 29 ls selected to be smaller than that of the sprlng 25 set ln place under compresslon.
Operat:Lon of the valve operating mechanlsm will be described wlth reference to FIGS. 3 and 4. When the englne ls to operate ln a low-speed range, the selectlve coupllng 21 ls actuated to dlsconnect the flrst and second cam followers 7, 8 from each other as lllustrated ln FIG. 4. More speclflcally, the hydraullc pressure is released by the hydraulic pressure ; control mechanlsm from the hydraullc pressure chamber ~9, thus allowlng the stopper 24 to move toward the second cam follower 8 under the resiliency of the sprlng 25 untll the plston 23 abuts agalnst the step 27. When the plston 23 engages the step ;~ 27, the mutually contactlng ends of the piston 23 and the stopper 2g lle fiush with the sllding side walls of the flrst 1316~1~ 60724-1718 an~ second cam ~ollowers 7, 8~ erefore, the flrst and second cam followers 7, 8 a.re held ln mutually slidlng contact for relatlve angular movement.
With the flrst and second cam followers 7, 8 belng thus disconnected, the flrst cam ~ollower 7 ls angularly moved in sliding contact wlth the cam 5, whereas the second cam follower 8 ls held ln slidlng contact wlth the ralsed portlon 3. Since the raised portlon 3 does not lmpose any camming actlon on the second cam follower 8, the intake valYes la, lb remaln closed. The swlnglng movement of the flrst cam follower 7 whlch ls caused by the cam 5 does not affect the lntake valves la, lb as the first cam follower 7 ls dlsconnected from the second cam follower 8 at this tlme. Any frlctlonal loss of the valve operatlng mechanism is relatlvely low because the flrst cam follower 7 ls held ln slldlng contact with the cam 5 under the rel~tlvely small rerlllent force of the sprln~ 20.
' ';' 13~6419 607Z4-1718 Duri.ng low-speed operation of the englne, therefore, the lntake valves la, lb remain closed or lnoperative for reduclng fuel consumptlon.
For high-speed operation of the englne, the flrst and second cam followers 7, 8 are lnterconnected by the selectlve coupling 21, as shown in FIG. 3. More speclfically, the hydraullc pressure chamber 2g of the .` 10 ` '' ' , ~3~6~9 .
_ G87-0002 selective coupling 21 is suppli-ed 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 cam followers 7, 8 are now connected to each other for angular movement in unison.
At this time, the second cam follower 8 is caused to swing with the first cam follower 7. Therefore, the intake valves la, lb alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the cam 5.
FIGS. 5 through 9 show a valve operating mechanism according to another embodiment of the present invention.
The valve operating mechanism comprises a cam- ~
shaft 2 rotatable in synchronism with rotation of the ~j engine at a speed ratio of 1/2 with respect to the speed of rotation of the engine. The.camshaft 2 has a.pair of annular raised portions 3 an* a~cam 5 which are integrally disposed on the circumference of t.he camshaft 2, the cam 5 being disposed between the raised portions 3. The valve operating mechanism also has a rocker shaft 6 extending parallel to the camshaft 2, and first through third cam followers 7, 8, 9 angularly movably supported on the rocker shaft 6 and held against the cam 5 and the raised portions 3, respectively, on the camshaft 2. A pair of intake valves la, lb remains inoperati.ve by the raised portions 3 131~419 G87-bP02 i in a low-speed range of the engine.
The camshaft 2 is rotatably disposed above the engine body. The cam 5 is disposed in a position corresponding to an intermediate position between the intake valves la, lb, as viewed in FIG. 6. The raised portions 3 are positioned substantially in line with the intake valves~la, lb, respectively. The raised portions 3 have a circumferential profile in the shape of a circle corresponding to the base circle 5b of the cam 5. The cam S has a cam lobe 5a projecting radially outwardly from the base circle 5b.
The rocker shaft 6 is fixed below the camshaft 2.
The first cam follower 7 pivotally supported on the rocker shaft 6 is aligned with the cam S, and the second and third cam followers 8, 9 pivotally supported on the rocker shaft 6 are aligned respectively with the raised portions 3. The cam followers 7, 8, 9 have on their upper surfaces cam slippers 7a, 8a, 9a, respectively, held in sliding contact with the cam S and the raised portions 3, respectively.
- The second and third cam followers 8, 9 have distal ends positioned above the intake valves la, lb, respectively.
; Tappet screws 12, 13 are threaded through the distal ends of the cam followers 8, 9 and have tips engagable respectively with the upper ends of the valve stems of the intake valves la, lb.
Flanges 14, 15 are attached to the upper ends of ~ the valve stems of the intake valves la, lb. The intake ~3~6 ~1 9`
- _ - G87-0002 valves la, lb 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.
A bottomed cylindrical lifter 19 is disposed in abutment agains~ a lower surface of the first cam follower 7. The lifter l9--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 7a of the first cam follower 7 slidably against the cam 5.
As illustrated in FIG. 8, the first and second cam followers 7, 8 have confronting side walls held in sliding contact with each other. A first selective coupling 21 is operatively disposed in and between the `
first and second cam followers 7, 8 for selectively dis-connecting the cam followers 7, 8 from each other for relative displacement and also for interconnecting the cam followers 7, 8 for their movement in unison. Likewi-se, the first and-third cam followers 7, 9 have confronting side walls held in sliding contact with each-other. A second selective coupling 22 is operatively disposed in and :
between the first and third cam followers 7, 9 for selec-tively disconnecting the cam followers 7, 9 from each other for relative displacement and also for interconnecting the cam followers 7, 9 for their movement in unison.
The first.and second selective couplings 21, 22 ' ~16 ~ 9 are of an identical construction, and hence only the first -selecti~ve coupling 21 will hereinafter be described in ~~
detail.
The first selective coupling 21 comprises a piston 23 movable between a position in which it ~ interconnects the first and second cam followers 7, 8 and a . positi-on in which it disconnects-the first and second cam followers 7, 8 from each other, a circular stopper 2~ 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 cam followers 7, 8 from each other.
The first cam follower 7 has a first guide hole 26 opening toward the second cam follower 8 and extending parallel to the rocker shaft 6. The first cam follower 7 ;,;
:~ àlso has a smaller-diameter hole 28 near the closed end of the first guide hole 25, 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 cam follower 7 has a hydraulic passage :~ 3~ 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 hydrau]ic pressure through a suitable 1316~9 -.
- G87-00~2 hydraulic pressure control mechanism. The hydraulic passages 30, 31 are held ïn communication with each other through a hole 32 defined in a side wall of the rocker shaft 6, irrespective of how the first cam follower 7 is _ angularly moved about the rocker shaft 6.
- ~ The second cam follower 8 has a second guide hole 35 opening towa-Ed the first cam follower--7-in registration with the first guide hoie 26 in the first cam follower 7.
The circular stopper 24 is slidably Eitted in the second guide hole 35. The second cam follower 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 cam follower 8 also has a through hole 38 defined ~
coaxially with the smaller-diameter hole 37. A guide rod ., 39 joined integrall.~ and coaxially to the circular stopper 24 extends through the hole 38. The coil spring 25 is ~ ~ disposed a~ound 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 cam followers 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 ~3~6~19 of the piston 23 remains in the first guide hole 26 and hence the piston 23 extends between the first and second cam followers 7, 8. The hydraulic passage 31 is shared by the first and second selective couplings 21, 22, which are therefore actuated simultaneously under fluid pressure supplied via the hydraulic passage 31.
Op-eration of the valve operating mechanism wil-l ~
be described with reference to FIGS. 8 and 9. When the engine is to operate in a low-speed range, the first and second selective couplings 21, 22 are actuated to discon-nect the first through third cam followers 7, 8, 9 from each other as illustrated in FIG. 8. More specifically, the hydraulic pressure is released by the hydraulic pressure control mechanism from the hydraulic pressure chamber 29, thus allowing the stopper 24 to move toward the first cam follower 7 under the resiliency of the spring 25 until the piston 23 abuts against the step 27. When the - piston 23 engages.the step 27, the mutually contacting ends of the piston 23 and the stopper 24 of the first selective ~ coupling 21 lie flush with the sliding side walls of the first and second cam followers 7, 8. Likewise, the mutually contacting ends of the piston 23 and the stopper 24 of the second selective coupling 22 lie flush with the sliding side walls of the first and third cam followers 7, ; 9. Thus, the first, second, and third cam followers 7, 8, 9 are held in mutually sliding contact for relative angular . movement.
, :
:, 1~16~19 _ G87-0002 ' With the first through third cam followers 7, 8, 9 being thus disconnected, the second and third cam followers 8, 9, which slidingly contact the raised portions 3, are not angularly moved, keeping the intake valves la, lb closed. The second and third cam followers ~ 8, 9 are not affected by the angular movement of the first cam~follower 7 in sliding contact with the cam ~. Any frictional loss of the valve operating mechainsm is relatively low because the first cam follower 7 is held in sliding contact with the cam 5 under the relatively small . resilient force of the spring 20.
; During low-speed operation of the engine, ` therefore, fuel consumption is reduced inasmuch as the intake valves la, lb remain closed or inoperative.
When the engine is to operate at a high speed, the first through third cam followers 7, 8, 9 are ., .
` interconnected by the first and second selective couplings ~ - 21, 22j-as shown in FIG. 9, by supplying hydraulic pressure . into the hydraulic-pressure chambers 29 of the first and second-selective couplings 21, 22- More specifically, the , pistons 23 are forced by the supplied hydraulic pressure into the second guide holes 35 while pressing the stoppers .~. 24 against the resilient-forces of the springs 25 until the ` stoypers 24 are pressed against the steps 36. The first through third cam followers 7, 8, 9 are interconnected by . the first and second selective couplings 21, 22 so that they are caused to swing in unison by the cam 5. As a :'`
~' 6 ~
_ - G87--0002 ;
consequence, the intake valves la, lb alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the cam 5.
FIG. 10 shows a valve operating mechanism according to still another embodiment of the present-invention. The camshaft 2 has a cam 5 and a pair of adjacent annular raised portions 3 disposed on-one side of the cam 5. The first and third cam followers 7, 9 are held in sliding contact with the raised portions 3, respectively, and engage the intake valves la, lb, respectively. The second cam follower 8 is held in sliding contact with the cam 5. The intake valves la, lb are controlled in different speed ranges by the mechanism shown in FIGS. 8 and 9. In the low-speed range, the intake valves la, lb remain closed or inoperative since the first and third cam followers 7, 9 are not angularly moved. In the high-speed range, the intake valves la, lb are caused to alternately open and close their intake ports according to the cam profile of the cam 5. - - -According to a still further embodlment shown inFIGS. 11 and 12, the camshaft 2 has an annular raised portion 3, a low-speed cam 4, and a high-speed cam 5 which are integrally disposed on the camshaft 2, the annular raised portion 3 being positioned between the low- and high-speed cams 4, 5. The raised portion 3 has a circumferential profile in the shape of a circle corresponding to the base circles 4b, 5b of the lo~- and :
- 1~ -~3~6~1~
high-speed cams 4, 5. The low-speed cam 4 has a cam lobe 4a projecting radially outwardly from the base circle 4b, and the high-speed cam 5 has a cam lobe 5a projecting radially outwardly from the base circle 5b to a greater extent than the cam lobe 4a, the cam lobe 5a also having a larger angular extent than the cam lobe 4a.
The first cam follower 7 is-held in sliding contact with the raised portion 3, whereas the second and third cam followers 8, 9 are held in sliding contact with the low- and high-speed cams 4, 5, respectively. The first cam follower 7 has a pair of arm ends engageable with the upper ends of the valve stems of a pair of intake valves la, lb.
The first through third cam followers 7, 8, 9 shown in FIG~ 11 are operated by a mechanism as shown in FIG. 13. The structure of FIG. 13 is substantially similar to that of FIGS. 8 and 9, except that a steel ball 33 is - forcibly fitted in the hydraulic passage 31 to divide it into two-independent passages~for separately operating the -first and second selective couplings 21, 22. In the low-speed range, the first through second cam followers 7, 8, 9 are disconnected from each other as shown in FIG. 8, and hence the intake valves` la, lb remain closed as the first cam follower 7 is not caused to swing. In the medium-speed range, the first and second cam followers 7, 8 are interconnected, while the first and third cam followers 7, 9 are disconnected from each other, as shown in FIG. 13.
~ 3 ~
Thus, the intake valves~la, lb are operated by the .
low-speed cam 4. In the high-speed range,-the first through third cam followers 7, 8, 9 are interconnected as shown ln FIG. 9 to enable the intake valves la, lb to be operated by the high-speed cam 5.
F~G. 14 shows a valve operating--mechanism according to a yet--still-further embodiment of the--present invention. In FIG. ]4, the low-speed cam 4 is positioned between the high-speed cam 5 and the annular raised portion 3. The first and second cam followers 7, 8 are held in sliding contact with the low- and high-speed cams 4, 5, and the third cam follower 9 engaging the intake valves la, lb is held in sliding contact with the raised portion 3. The mechanism shown in FIG. 15, which is similar to FIGS. 8 and 9 and identical to that of FIG. 13, is employed to control the intake valves la, lb. In the low-speed range, the first through second--cam followers 7, 8, 9 are disconnected from each other as shown in FIG. 8, and hence the intake valves la,.lb~remain closed. In the medium-speed range, -: the first and third cam followers 7, 9 are interconnected, while the first and second cam followers 7, 8 are isconnected from each other, as shown in FIG. 15. Thus, the intake valves la, lb are operated bv the low--speed cam 4. In the high-speed range, the first through third cam followers 7, 8, 9 are interconnected as shown in FIG. 9 to operate the intake valves la, lb according to the cam profile of the high-speed cam 5.
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:
~3164~9 ; ~hile the intake valves la, lb-are shown as being operated by each of the valve operating mechanisms, exhaust valves may also be operated by the valve operating mechanisms according to the present invention. In such a case, unburned components due to exhaust-gas turbulence can be-reduced in low-speed oper-ation of the enginé, whereas high engine output power and torque--ean b~e generated by --reducing resistance to the flow of an exhaust gas from the combustion chamber in high-speed operation of the engine.
Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims.
l!
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VALVE OPERATING MECHANISM
-- ~OR I~TERNAL COMB~STIO~ ENGINE
BACKGRO~ND OF THE INVENTION
The present invention relates to a valve~--operating mechanism for an inter~na] 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 or cam followers angularly movable supported on a rocker shaft for opening and closing the intake or exhaust valves in response to rotation of the cams. ' -Japanese I.aid-Open Patent Publication No.
59(1984)-22621~, for exampler discloses a valve operating mechanism for use in an internal combustion engine having a plurality of intake or exhaust valves per engine cylinder.
, Some of the intake or exhaust valves remai'n cl-bsed when the engine operates at a low speed. If the intake or exhaust valves of a particular engine cylinder of a multicylinder internal combustion engine could be kept inoperative in order to cut off the operation of the particular engine cylinder, fuel consumption would be reduced by stopping the operation of the intake or exhaust valves of the particular engine cylinder while the engine operates in a low-speed range. ~owever, no satisfactory devices have been available in the past to achieve such a task.
- 1 - ~, G0/24 171~
SU~M~RY OF THE INVENTION 1316 ~19 It is an ob~ect Qf the present invention to provide a valve operating mechanism for in in~ernal combustion engine, which is of a relatively simple structure, for making the intake or exhaust valves of a particular engine cylincler inoperative for better fuel economy.
According to the present invention, there is provided a valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine, comprising a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam, a plurality of cam followers at ~east one of which slidably engages the cam for selectively operating the valves acccording to a cam profile of the cam, and means for selectively interconnecting and disconnecting the cam followers to operate . the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inope:rative by at least one of said cam followers engaging an annular raised portion on said camshaft.
The camshaft has one or two annular raised portions : in addition to the cam, and the cam followers include one or ~ two cam followers which slidably engage the raised portion or ~ portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed cams.
:`~
,~.
1 316 ~19 . "; 1~
Acool-d~ ,o .-ltl(,tJler aspect of the present 1n~enti.i, there `LS provlcled a valve c!peratir!g mechanism for operat1ng a pl~lrdlil y o:F valves of a particular cylinder of an internal combustiun enyirle~ compririlncJ: a camshaft carrying an -Innular ralsed portion for maintaining sa:id valves in a closed condition and cam means having a cam Profile for sequentia:Lly open~ g and closlng said valves, first cam follower means sli.clably engaging said raised por-tion and operati.vely connec-ting said valves thereto, second cam follower means slidably engaging said cam means, and means for selectively interconnecting and disconnecting said first and second cam followers a-t a predetermined conclition of engine operation whereby sai.d raised portion is effective to close said valves : during one range of engine operation ancl said cam means is effective to operàte said valves during another range of eng1ne operation.
-- a -'~
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1 3 1 6 ~ ~ 9 6c~ 8 T~ne ahove and other ob~ects, features and advantages of the piesent invention wi3.1 ~ecome more apparent from the following description when takerl in con~unction wlth the accompanylng drawings in whlch preferred embodlments of the present lnvention are shown by way of 11 lu5t rative example.
BRI~F DFSCRIPTION_OF THE DRAWINGS
FIG. 1 is a vertlcal cross-sectiotlal vlew of a valve operatlng mechanlsm accordlng to an embodlment o~ the present inventlon, the view belng taken along llne I - I of FIG. Z;
FIG. 2 ls a plan view of the valve operatlng mechanism shown ln FIG. l;
FIG. 3 ls a cross-sectlonal vlew taken along line III
- III of FIG. 1, showlng first and second cam followers connected to each other;
FIG. 4 is a cross-sectional view simllar to FIG. 3, showlng the first and second cam followers disconnected from each other;
FIG. 5 ls a vertlcal cross-sectional vlew of a valve operating mechanlsm accordlng to another embodiment of the present inventlon, the vlew belng taken along line V - V of FIG. 6;
FIG. 6 is a plan view of the valve operatlng mechanlsm shown ln FIG. ~;
FIG. 7 ls a cross~sectlonal vlew taken along llne VII - VII of FIG. 6;
, 131~419 - G~7-0002 FIG. 8 is a cross-sectional view taken along line VIII - VIII of FIG. 5, showing first through third cam followers disconnected from each other;
FIG. 9 is a cross-sectional view similar to FIG.
8, showing the first through third cam followers interconnected;
FIG. 10 is a plan view of a valve operating mechanism according to still another embodiment of the present invention; and FIG. 11 is a plan view of a valve operating mechanism according to a still further embodiment of the present invention;
FIG. 12 is a cross-sectional view taken along llne XII - XII of FIG. 11;
FIG. 13 is a cross-sectional view taken along llne XIII - XIII of FIG. 12, showing a mechanism for actuating the valve operating mechanism of FIG. 11;
- FIG. 14 is a plan view of a valve operating mechanism according to a yet still further embodiment of the present invention; and ; FIG. 15 is a cross-sectional view similar to ; Figs. 8,9 and 13r showing a mechanism for actuating the valve operating mechanism of FIG.14-DESCRIPTION OF THE PREFERRED EMBODIMENTS
Like or corresponding parts are denoted by like or corresponding re~erence characters throughout several , views . -' . ' ' ~ `
~3~1g ~07~4-171 F~IGS. 1 and 2 show a valve operatlng mechanlsm according to an embodiment of the present invention. The valve operating mechanlsm ls lncorporated in an internal combustion engine for use with a particular engine cyllnder having a pair of intake valves la, lb ~or introducing an air-fuel mixture into a combustion chamber defined in an engine body.
The valve operating mechanlsm comprises a camshaft 2 rotatable in synchronism with rotation of the englne at a speed ratlo o~ 1/2 with respect to the speed of rotatlon of the engine. The camshaft 2 has an annular raised portion 3 and a cam 5 which are lntegrally disposed on the circumference of the camshaft 2. The valve operatlng mechanlsm also has a rocker shaft 6 e~tending parallel to the camshaft 2, and flrst and second rocker arms or cam followers 7, 8 angularly movably supported on the rocker shaft 6 and held against the cam 5 and the ralsed portion 3, respectlvely, on the camshaft 2. The intake valves laJ lb remain closed or inoperatlve by the ralsed portion 3 in a low-speed range of the engine.
The camshaft 2 ls rotatably dlsposed above the engine body. The ralsed portlon 3 ls dlsposed ln a posltion correspondlng to an intermedlate positlon between the intake valves la, lb, a.s viewed i.n FIG. 2. The cam 5 is pos1tloned substantially ln l~ne wlth the lntake valve lb. The raised portion 3 has a circumferentlal proflle ln the shape of a circle correspondlng to the base clrcle 5b o~ the cam 5. The cam 5 has a cam lobe 5a proJectlng radlally outwardly from the base clrcle 5b.
The rocker shaft 6 ls flxed below the camshaft ~.
The flrst cam follower 7 plvotally supported on the rocker shaft 6 ls aligned with the cam 5, and the second cam follower 8 pivotally supported on the rocker shaft 6 ls aligned with the ralse~ portlon 3. The cam followers 7, 8 have on their upper surfaces cam sllppers 7a, 8a, respectively, held in sllding contact wlth the cam 5 and the raised portlon 3, respectlvely.
The second cam follower 8 lncludes a palr of arms 8b, 8c having distal ends positicned above the lnt~ke valves la, lb, respectlvely. Tappet screws 12, 13 are threaded through the dlstal ends of the arms 8b, 8c and have tips engageable respectlvely wlth the upper ends of the valve stems of the lntake valves la, ~b.
Flanges 14, 15 are attached to the upper ends of the valve stems of the intake valves la, lb. The intake valves la, lb are normally urged to close the lntake ports by compresslon coll sprlngs 16, 17 dlsposed under compresslon around the valve stems between the flanges 14, 15 and the englne body.
A bottomed cyllndrlcal lifter 19 ls dlsposed ln abutment against a lower surface of the flrst cam follower 7.
; The llfter l9 ls normall~ urged upwardly by a compresslon sprlng 20 of relatlvely weak reslllency lnterposed between the lifter 19 and the engine body for reslliently biaslng the cam sllpper 7a of the flrst cam follower 7 slldably agalnst the cam 5.
As illustrated ln FIG. 3, the flrst and second cam followers 7, 8 have confrontlng slde walls held ln slldlng contact wlth each other. A selectlve coupllng 21 ls operatlvely dlsposed ln and between the flrst and second cam followers 7, 8 for selectlvely disconnectlng the cam followers 7, 8 from each other for relatlve dlsplacement and also for interconnectlng the cam followers 7, 8 for their movement in unison.
~ he selectlve coupling 21 comprlses a plston 23 movable between a posltlon in whlch lt interconnects the flrst and second cam followers 7, 8 and a positlon ln which lt dlsconnects the flrst and second cam followers 7, 8 from each ..
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~316~19 507~4-171~
other, a circular stopper 24 for limlting the movement of the plston 23, and a coil sprlng 25 for urging the stopper 24 to move the plston 23 toward the posltlon to dlsconnect the flrst and second cam followers 7, 8 from each other.
The second cam follower 8 has a flrst gulde hole 26 opening toward the first cam follower 7 and e~tendlng parallel to the rocker shaft 6. The second cam follower 8 also has a smaller-dlameter hole 28 near the closed end of the flrst gulde hole 26, wlth a step or shoulder 27 belng defi.ned betwe~n the smaller-dlarneter hole 28 and the flrst guide hole 26. The plston 23 ls slldably fltted in the first gulde hole 26. The piston 23, and the closed end of the smaller-dlameter hole 28 define therebetween a hydraullc pressure chamber 29.
: The second cam follower 8 has a hydraullc passage 30 deflned thereln ln communlcatlon with the hydraulic pressure chamber 29. The rocker shaft 6 has a hydraulic passage 31 defined axlally thereln and coupled to a source (not shown) of hydraullc pressure through a sultable hydraullc pressure . control mechanlsm. The hydraullc passages 30, 31 are held in communlcatlon wlth each other through a hole 32 deflned in a side wall of the rocker shaft 6, lrrespectlve of how the second cam follower 8 ls angularly moved about the rocker shaft 6.
The flrst cam follower 7 has a second guide hole 35 openlng toward the second cam follower 8 ln registratlon wlth the flrst gulde hole 26 ln the second cam follower 8. The clrcular stopper Z4 ls slidably fitted ln the second guide hole 35. The flrst cam follower 7 also has a smaller-dlameter hole 37 near the closed end of the second gulde hole 35, wlth a step : or shoulder 36 defined between the second gulde hole 35 and the smaller-dlameter hole 37 for llmiting movement of the circular stopper 24. The flrst cam follower 7 also has a through hole 38 defined coaxlally wlth the smaller-dlameter hole 37. A
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~316419 guide rod 39 ~olned lntegrall.y and coaxlally to the circular stopper 24 exten~s through the hole 38. The coll spring 25 ls disposed around the gulde rod 39 between the stopper 24 and the closed end of the smaller-dlameter hole 37.
The pis~on 23 has an axial length selected such that when one end of the plston 23 abuts agalnst the step 27, the other end thereof ls positloned ~ust between and hence lles flush wlth the slidlng side walls of the flrst and second cam followers 7, 8, and when the piston 23 ls moved lnto the second gulde hole 35 untll it dlsplaces the stopper 24 into abutment agalnst the step 36, sald one end of the plston 23 remalns in the flrst gulde hole 26 and hence the piston 23 extends between the flrst and second cam followers 7, 8. The piston 23 ls normally urged toward the first cam follower 7 under the reslllency of a coil spring 33 disposed in the hydraullc pressure chamber 29 and actlng between the plston 23 and the closed bottom of the smaller-diameter hole 28. The reslllent force of the spri.ng 33 set under compresslon ln the hydraullc pressure chamber 29 ls selected to be smaller than that of the sprlng 25 set ln place under compresslon.
Operat:Lon of the valve operating mechanlsm will be described wlth reference to FIGS. 3 and 4. When the englne ls to operate ln a low-speed range, the selectlve coupllng 21 ls actuated to dlsconnect the flrst and second cam followers 7, 8 from each other as lllustrated ln FIG. 4. More speclflcally, the hydraullc pressure is released by the hydraulic pressure ; control mechanlsm from the hydraullc pressure chamber ~9, thus allowlng the stopper 24 to move toward the second cam follower 8 under the resiliency of the sprlng 25 untll the plston 23 abuts agalnst the step 27. When the plston 23 engages the step ;~ 27, the mutually contactlng ends of the piston 23 and the stopper 2g lle fiush with the sllding side walls of the flrst 1316~1~ 60724-1718 an~ second cam ~ollowers 7, 8~ erefore, the flrst and second cam followers 7, 8 a.re held ln mutually slidlng contact for relatlve angular movement.
With the flrst and second cam followers 7, 8 belng thus disconnected, the flrst cam ~ollower 7 ls angularly moved in sliding contact wlth the cam 5, whereas the second cam follower 8 ls held ln slidlng contact wlth the ralsed portlon 3. Since the raised portlon 3 does not lmpose any camming actlon on the second cam follower 8, the intake valYes la, lb remaln closed. The swlnglng movement of the flrst cam follower 7 whlch ls caused by the cam 5 does not affect the lntake valves la, lb as the first cam follower 7 ls dlsconnected from the second cam follower 8 at this tlme. Any frlctlonal loss of the valve operatlng mechanism is relatlvely low because the flrst cam follower 7 ls held ln slldlng contact with the cam 5 under the rel~tlvely small rerlllent force of the sprln~ 20.
' ';' 13~6419 607Z4-1718 Duri.ng low-speed operation of the englne, therefore, the lntake valves la, lb remain closed or lnoperative for reduclng fuel consumptlon.
For high-speed operation of the englne, the flrst and second cam followers 7, 8 are lnterconnected by the selectlve coupling 21, as shown in FIG. 3. More speclfically, the hydraullc pressure chamber 2g of the .` 10 ` '' ' , ~3~6~9 .
_ G87-0002 selective coupling 21 is suppli-ed 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 cam followers 7, 8 are now connected to each other for angular movement in unison.
At this time, the second cam follower 8 is caused to swing with the first cam follower 7. Therefore, the intake valves la, lb alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the cam 5.
FIGS. 5 through 9 show a valve operating mechanism according to another embodiment of the present invention.
The valve operating mechanism comprises a cam- ~
shaft 2 rotatable in synchronism with rotation of the ~j engine at a speed ratio of 1/2 with respect to the speed of rotation of the engine. The.camshaft 2 has a.pair of annular raised portions 3 an* a~cam 5 which are integrally disposed on the circumference of t.he camshaft 2, the cam 5 being disposed between the raised portions 3. The valve operating mechanism also has a rocker shaft 6 extending parallel to the camshaft 2, and first through third cam followers 7, 8, 9 angularly movably supported on the rocker shaft 6 and held against the cam 5 and the raised portions 3, respectively, on the camshaft 2. A pair of intake valves la, lb remains inoperati.ve by the raised portions 3 131~419 G87-bP02 i in a low-speed range of the engine.
The camshaft 2 is rotatably disposed above the engine body. The cam 5 is disposed in a position corresponding to an intermediate position between the intake valves la, lb, as viewed in FIG. 6. The raised portions 3 are positioned substantially in line with the intake valves~la, lb, respectively. The raised portions 3 have a circumferential profile in the shape of a circle corresponding to the base circle 5b of the cam 5. The cam S has a cam lobe 5a projecting radially outwardly from the base circle 5b.
The rocker shaft 6 is fixed below the camshaft 2.
The first cam follower 7 pivotally supported on the rocker shaft 6 is aligned with the cam S, and the second and third cam followers 8, 9 pivotally supported on the rocker shaft 6 are aligned respectively with the raised portions 3. The cam followers 7, 8, 9 have on their upper surfaces cam slippers 7a, 8a, 9a, respectively, held in sliding contact with the cam S and the raised portions 3, respectively.
- The second and third cam followers 8, 9 have distal ends positioned above the intake valves la, lb, respectively.
; Tappet screws 12, 13 are threaded through the distal ends of the cam followers 8, 9 and have tips engagable respectively with the upper ends of the valve stems of the intake valves la, lb.
Flanges 14, 15 are attached to the upper ends of ~ the valve stems of the intake valves la, lb. The intake ~3~6 ~1 9`
- _ - G87-0002 valves la, lb 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.
A bottomed cylindrical lifter 19 is disposed in abutment agains~ a lower surface of the first cam follower 7. The lifter l9--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 7a of the first cam follower 7 slidably against the cam 5.
As illustrated in FIG. 8, the first and second cam followers 7, 8 have confronting side walls held in sliding contact with each other. A first selective coupling 21 is operatively disposed in and between the `
first and second cam followers 7, 8 for selectively dis-connecting the cam followers 7, 8 from each other for relative displacement and also for interconnecting the cam followers 7, 8 for their movement in unison. Likewi-se, the first and-third cam followers 7, 9 have confronting side walls held in sliding contact with each-other. A second selective coupling 22 is operatively disposed in and :
between the first and third cam followers 7, 9 for selec-tively disconnecting the cam followers 7, 9 from each other for relative displacement and also for interconnecting the cam followers 7, 9 for their movement in unison.
The first.and second selective couplings 21, 22 ' ~16 ~ 9 are of an identical construction, and hence only the first -selecti~ve coupling 21 will hereinafter be described in ~~
detail.
The first selective coupling 21 comprises a piston 23 movable between a position in which it ~ interconnects the first and second cam followers 7, 8 and a . positi-on in which it disconnects-the first and second cam followers 7, 8 from each other, a circular stopper 2~ 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 cam followers 7, 8 from each other.
The first cam follower 7 has a first guide hole 26 opening toward the second cam follower 8 and extending parallel to the rocker shaft 6. The first cam follower 7 ;,;
:~ àlso has a smaller-diameter hole 28 near the closed end of the first guide hole 25, 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 cam follower 7 has a hydraulic passage :~ 3~ 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 hydrau]ic pressure through a suitable 1316~9 -.
- G87-00~2 hydraulic pressure control mechanism. The hydraulic passages 30, 31 are held ïn communication with each other through a hole 32 defined in a side wall of the rocker shaft 6, irrespective of how the first cam follower 7 is _ angularly moved about the rocker shaft 6.
- ~ The second cam follower 8 has a second guide hole 35 opening towa-Ed the first cam follower--7-in registration with the first guide hoie 26 in the first cam follower 7.
The circular stopper 24 is slidably Eitted in the second guide hole 35. The second cam follower 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 cam follower 8 also has a through hole 38 defined ~
coaxially with the smaller-diameter hole 37. A guide rod ., 39 joined integrall.~ and coaxially to the circular stopper 24 extends through the hole 38. The coil spring 25 is ~ ~ disposed a~ound 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 cam followers 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 ~3~6~19 of the piston 23 remains in the first guide hole 26 and hence the piston 23 extends between the first and second cam followers 7, 8. The hydraulic passage 31 is shared by the first and second selective couplings 21, 22, which are therefore actuated simultaneously under fluid pressure supplied via the hydraulic passage 31.
Op-eration of the valve operating mechanism wil-l ~
be described with reference to FIGS. 8 and 9. When the engine is to operate in a low-speed range, the first and second selective couplings 21, 22 are actuated to discon-nect the first through third cam followers 7, 8, 9 from each other as illustrated in FIG. 8. More specifically, the hydraulic pressure is released by the hydraulic pressure control mechanism from the hydraulic pressure chamber 29, thus allowing the stopper 24 to move toward the first cam follower 7 under the resiliency of the spring 25 until the piston 23 abuts against the step 27. When the - piston 23 engages.the step 27, the mutually contacting ends of the piston 23 and the stopper 24 of the first selective ~ coupling 21 lie flush with the sliding side walls of the first and second cam followers 7, 8. Likewise, the mutually contacting ends of the piston 23 and the stopper 24 of the second selective coupling 22 lie flush with the sliding side walls of the first and third cam followers 7, ; 9. Thus, the first, second, and third cam followers 7, 8, 9 are held in mutually sliding contact for relative angular . movement.
, :
:, 1~16~19 _ G87-0002 ' With the first through third cam followers 7, 8, 9 being thus disconnected, the second and third cam followers 8, 9, which slidingly contact the raised portions 3, are not angularly moved, keeping the intake valves la, lb closed. The second and third cam followers ~ 8, 9 are not affected by the angular movement of the first cam~follower 7 in sliding contact with the cam ~. Any frictional loss of the valve operating mechainsm is relatively low because the first cam follower 7 is held in sliding contact with the cam 5 under the relatively small . resilient force of the spring 20.
; During low-speed operation of the engine, ` therefore, fuel consumption is reduced inasmuch as the intake valves la, lb remain closed or inoperative.
When the engine is to operate at a high speed, the first through third cam followers 7, 8, 9 are ., .
` interconnected by the first and second selective couplings ~ - 21, 22j-as shown in FIG. 9, by supplying hydraulic pressure . into the hydraulic-pressure chambers 29 of the first and second-selective couplings 21, 22- More specifically, the , pistons 23 are forced by the supplied hydraulic pressure into the second guide holes 35 while pressing the stoppers .~. 24 against the resilient-forces of the springs 25 until the ` stoypers 24 are pressed against the steps 36. The first through third cam followers 7, 8, 9 are interconnected by . the first and second selective couplings 21, 22 so that they are caused to swing in unison by the cam 5. As a :'`
~' 6 ~
_ - G87--0002 ;
consequence, the intake valves la, lb alternately open and close the respective intake ports at the valve timing and valve lift according to the profile of the cam 5.
FIG. 10 shows a valve operating mechanism according to still another embodiment of the present-invention. The camshaft 2 has a cam 5 and a pair of adjacent annular raised portions 3 disposed on-one side of the cam 5. The first and third cam followers 7, 9 are held in sliding contact with the raised portions 3, respectively, and engage the intake valves la, lb, respectively. The second cam follower 8 is held in sliding contact with the cam 5. The intake valves la, lb are controlled in different speed ranges by the mechanism shown in FIGS. 8 and 9. In the low-speed range, the intake valves la, lb remain closed or inoperative since the first and third cam followers 7, 9 are not angularly moved. In the high-speed range, the intake valves la, lb are caused to alternately open and close their intake ports according to the cam profile of the cam 5. - - -According to a still further embodlment shown inFIGS. 11 and 12, the camshaft 2 has an annular raised portion 3, a low-speed cam 4, and a high-speed cam 5 which are integrally disposed on the camshaft 2, the annular raised portion 3 being positioned between the low- and high-speed cams 4, 5. The raised portion 3 has a circumferential profile in the shape of a circle corresponding to the base circles 4b, 5b of the lo~- and :
- 1~ -~3~6~1~
high-speed cams 4, 5. The low-speed cam 4 has a cam lobe 4a projecting radially outwardly from the base circle 4b, and the high-speed cam 5 has a cam lobe 5a projecting radially outwardly from the base circle 5b to a greater extent than the cam lobe 4a, the cam lobe 5a also having a larger angular extent than the cam lobe 4a.
The first cam follower 7 is-held in sliding contact with the raised portion 3, whereas the second and third cam followers 8, 9 are held in sliding contact with the low- and high-speed cams 4, 5, respectively. The first cam follower 7 has a pair of arm ends engageable with the upper ends of the valve stems of a pair of intake valves la, lb.
The first through third cam followers 7, 8, 9 shown in FIG~ 11 are operated by a mechanism as shown in FIG. 13. The structure of FIG. 13 is substantially similar to that of FIGS. 8 and 9, except that a steel ball 33 is - forcibly fitted in the hydraulic passage 31 to divide it into two-independent passages~for separately operating the -first and second selective couplings 21, 22. In the low-speed range, the first through second cam followers 7, 8, 9 are disconnected from each other as shown in FIG. 8, and hence the intake valves` la, lb remain closed as the first cam follower 7 is not caused to swing. In the medium-speed range, the first and second cam followers 7, 8 are interconnected, while the first and third cam followers 7, 9 are disconnected from each other, as shown in FIG. 13.
~ 3 ~
Thus, the intake valves~la, lb are operated by the .
low-speed cam 4. In the high-speed range,-the first through third cam followers 7, 8, 9 are interconnected as shown ln FIG. 9 to enable the intake valves la, lb to be operated by the high-speed cam 5.
F~G. 14 shows a valve operating--mechanism according to a yet--still-further embodiment of the--present invention. In FIG. ]4, the low-speed cam 4 is positioned between the high-speed cam 5 and the annular raised portion 3. The first and second cam followers 7, 8 are held in sliding contact with the low- and high-speed cams 4, 5, and the third cam follower 9 engaging the intake valves la, lb is held in sliding contact with the raised portion 3. The mechanism shown in FIG. 15, which is similar to FIGS. 8 and 9 and identical to that of FIG. 13, is employed to control the intake valves la, lb. In the low-speed range, the first through second--cam followers 7, 8, 9 are disconnected from each other as shown in FIG. 8, and hence the intake valves la,.lb~remain closed. In the medium-speed range, -: the first and third cam followers 7, 9 are interconnected, while the first and second cam followers 7, 8 are isconnected from each other, as shown in FIG. 15. Thus, the intake valves la, lb are operated bv the low--speed cam 4. In the high-speed range, the first through third cam followers 7, 8, 9 are interconnected as shown in FIG. 9 to operate the intake valves la, lb according to the cam profile of the high-speed cam 5.
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~3164~9 ; ~hile the intake valves la, lb-are shown as being operated by each of the valve operating mechanisms, exhaust valves may also be operated by the valve operating mechanisms according to the present invention. In such a case, unburned components due to exhaust-gas turbulence can be-reduced in low-speed oper-ation of the enginé, whereas high engine output power and torque--ean b~e generated by --reducing resistance to the flow of an exhaust gas from the combustion chamber in high-speed operation of the engine.
Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims.
l!
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Claims (12)
1. A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine, comprising:
a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam;
a plurality of cam followers, one of which slidably engages said cam for selectively operating the valves according to a cam profile of said cam; and means for selectively interconnecting and disconnecting said cam followers to operate the valves differently in different speed ranges of the internal combustion engine, said speed ranges including a range in which all of the valves remain inoperative by at least one of said cam followers engaging an annular raised portion on said camshaft.
a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam;
a plurality of cam followers, one of which slidably engages said cam for selectively operating the valves according to a cam profile of said cam; and means for selectively interconnecting and disconnecting said cam followers to operate the valves differently in different speed ranges of the internal combustion engine, said speed ranges including a range in which all of the valves remain inoperative by at least one of said cam followers engaging an annular raised portion on said camshaft.
2. A valve operating mechanism according to claim 1, wherein said camshaft has two said annular raised portions with one positioned on each side of said cam, said cam followers including cam followers which slidably engage said raised portions, respectively, for controlling said valves, said means including means for selectively keeping said valves inoperative in said range with said raised portions and operating said valves in a high-speed range with said cam.
3. A valve operating mechanism according to claim 1, wherein said camshaft has said annular raised portion positioned adjacent to said cam, said cam followers including a cam follower which slidably engages said raised portion for controlling said valves, said means including means for selectively keeping said valves inoperative in said range with said raised portion and operating said valves in a high-speed range with said cam.
4. A valve operating mechanism according to claim 1, wherein said camshaft has two adjacent annular raised portions positioned on one side of said cam, said cam followers including cam followers which slidably engage said raised portions, respectively, for controlling said valves, said means including means for selectively keeping said valves inoperative in said range with said raised portions and operating said valves in a high-speed range with said cam.
5. A valve operating mechanism according to claim 1, wherein said camshaft has said annular raised portion, a low-speed cam, and a high-speed cam, said raised portion being positioned between said low- and high-speed cams, said cam followers including cam followers which slidably engage said low- and high-speed cams, respectively, and a cam follower which slidably engages said raised portion for controlling said valves, said means including means for selectively keeping said valves inoperative in said range with said raised portion and operating said valves in a low-speed range with said low-speed cam and in a high-speed range with said high - speed cam.
6. A valve operating mechanism according to claim 1, wherein said camshaft has said annular raised portion, a low-speed cam, and a high-speed cam, said low-speed cam being positioned between said raised portion and said high-speed cams, said cam followers including cam followers which slidably engage said low- and high-speed cams, respectively, and a cam follower which slidably engages said raised portion for controlling said valves, said means including means for selectively keeping said valves inoperative in said range with said raised portion and operating said valves in a low-speed range with said low-speed cam and in a high-speed range with said cam.
7. A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine, comprising: a camshaft carrying an annular raised portion for maintaining said valves in a closed condition and cam means having a cam profile for sequentially opening and closing said valves, first cam follower means slidably engaging said raised portion and operatively connecting said valves thereto, second cam follower means slidably engaging said cam means, and means for selectively interconnecting and disconnecting said first and second cam followers at a predetermined condition of engine operation whereby said raised portion is effective to close said valves during one range of engine operation and said cam means is effective to operate said valves during another range of engine operation.
8. A valve operating mechanism as recited in claim 7 in which said cam means includes a cam profile comprising a base circle and a cam lobe extending radially therefrom and said annular raised portion has a diameter corresponding substantially to that of said base circle.
9. A valve operating mechanism as recited in claim 8 in which said first cam follower means is a bifurcate member effective to operatively connect said valves to said raised portion.
10. A valve operating mechanism as recited in claim 9 in which said cam means includes a low-speed and a high-speed cam and said interconnecting and disconnecting means including means for connecting and disconnecting said second cam follower means to said first cam follower means for operation of said first cam follower means in response to either said raised portion, said low-speed cam or said high-speed cam.
11. A valve operating mechanism as recited in claim 10 in which said interconnecting and disconnecting means are effective to selectively connect said first cam follower means with the adjacent second cam follower means.
12. A valve operating mechanism as recited in claim 11 in which said first, cam follower means is positioned intermediate the respective of said second cam follower means and said interconnecting and disconnecting means are effective to selectively connect said first cam follower means with either or both of said respective second cam follower means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000528462A CA1316419C (en) | 1987-01-29 | 1987-01-29 | Valve operating mechanism for internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000528462A CA1316419C (en) | 1987-01-29 | 1987-01-29 | Valve operating mechanism for internal combustion engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1316419C true CA1316419C (en) | 1993-04-20 |
Family
ID=4134852
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000528462A Expired - Fee Related CA1316419C (en) | 1987-01-29 | 1987-01-29 | Valve operating mechanism for internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1316419C (en) |
-
1987
- 1987-01-29 CA CA000528462A patent/CA1316419C/en not_active Expired - Fee Related
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