US3401572A - Compact speed sensitive timing device for internal combustion engines - Google Patents

Description

Sept. 17, 1968 .1. M. BAILEY 3, 0

COMPACT SPEED SENSITIVE TIMING DEVICE FOR INTERNAL COMBUSTION ENGINES Filed Sept. 12, 1966 R r" 8 I7 I W El .1 5 44 Z7\ 39 4 5z\ 43 20 24 i: 48 A INVENTOR. JOHN M. BAILEY ATTORNEYS 3,401,572 Patented Sept. 17, 1968 United States Patent Office 3,401,572 COMPACT SPEED SENSITIVE TIMING DEVICE FOR INTERNAL COMBUSTION ENGINES John M. Bailey, East Peoria, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill., a corporation of California Filed Sept. 12, 1966, Ser. No. 578,783 6 Claims. (Cl. 74395) ABSTRACT OF THE DISCLOSURE Compact mechanism for adjusting engine timing has a fluid filled vortex chamber contained within a cam shaft drive gear and centrifugally generating a force proportional to engine speed. Means translate the force into axial movement at a helical spline coupling between the gear and one of the rotating members engaged therewith to vary the annular phase relationship therebetween in accordance with engine speed.

This invention relates to internal combustion engines and more particularly to mechanisms for automatically adjusting the timing of fuel injection or ignition in response to changes in engine speed.

In a typical internal combustion engine, the fuel injection or ignition mechanism is coupled to the engine crankshaft through a system of gears and cams or equivalent means. Thus, in the absence of suitable adjustment means, the timing of fuel combustion relative to piston position is fixed by the design parameters of the engine. However such engines operate much more efficiently if timing is varied with changes in engine speed. Timing should be advanced as engine speed increases and retarded with decreases in speed and it is preferable that the means for making this adjustment operate automatically.

A form of automatic timing adjustment mechanism which is extensively used on diesel engines for example, senses changes in engine speed by means of a roating shaft coupled to the engine crankshaft and carrying flyweights which move radially in response to changes in the speed thereof. The flyweights control the axial position of a rotating element of the fuel injection pump drive. The drive element has helical gear teeth or a helical spline mounting so that the axial movements of the element advance or retard timing according to the direction of the movement.

Flyweight controlled systems of the type discussed above are somewhat bulky and complex and are subject to rapid wear, particularly around the flyweight pivots, which interferes with eflicient operation and aggravates maintenance. To avoid these problems a second class of timing device is sometimes used in which engine speed is sensed through the pressure of the engine lubricating oil or the engine fuel oil. As the pumps which generate such pressure are also operated by the engine crank shaft, the oil pressure is a function of engine speed. Typically, the oil pressure is caused to control the axial position of a helical component of the fuel injection drive and thereby adjust timing as discussed above with reference to fly weight controlled mechanisms.

As heretofore constructed, oil pressure controlled timing devices have still been more bulky and complex than is desirable and have been subject to certain operational difficulties peculiar to such mechanisms. Such timing devices have been very dependent, for example, on precise functioning of the oil circulating pumps and can be strongly influenced by pump wear, changes in oil viscosity and other factors. Further, many timing devices of this class are limited to use with either distributor fuel injection systems or in line fuel pumps but are not adaptable to both. 1

The present invention provides a timing mechanism which is oil controlled in a unique manner that removes the disadvantages of prior oil pressure operated devices and obtains the advantages of flyweight systems in a very compact and low maintenance mechanism. In particular, the timing is not controlled by the engine oil pressure per se as in prior devices but is determined by a volume of oil which rotates within means coupled to the engine crankshaft. Thus an oil pressure proportional to engine speed is self generated within the timing mechanism itself by centrifugal force and is not severly affected by the condition of the remote oil circulating pump or other extraneous factors. The mechanism requires only a small number of parts which can be largely contained within the drive gear and drive shaft of the fuel injection system so that extreme compactness results. 1

Accordingly it is an object of this invention to provide an automatic timing adjustment mechanism for internal combustion engines which has relatively few parts, is extremely compact and requires little maintenance.

It is another object of this invention to provide an engine timing device operated by an oil pressure proportional to engine speed which is less dependent on the condition of remote oil pumps, oil viscosity, or other extraneous factors.

It is still another object of the invention to provide automatic timing adjustment means for an engine which may be largely contained within the fuel injection system drive gear and drive shaft.

It is a further object of the invention to provide a compact speed sensitive timing adjustment mechanism for engines that is adaptable for use with both distributor type and in line type fuel injection systems.

It is still a further object of the invention to provide an engine timing adjustment mechanism which is relatively free from wear prone mechanical parts and which is inherently damped to avoid hunting about an optimum timing adjustment.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following specification together with the accompanying drawing, of which:

FIGURE 1 is a section view showing a fuel injection pump and drive shaft and drive gear of the fuel injection system of a diesel engine with the present invention embodied therein; and

, FIGURE 2 is a section view of portions of the drive train of a diesel fuel injection system utilizing a second embodiment of the invention.

Referring now to the drawing and more particularly to FIGURE 1 thereof, a diesel fuel injection pump 11 is usually operated by a rotating cam shaft 12 having integral cams 13g thereon which translate a cam follower 14 associated with each injection pump, the detailed construction and operation of such pumps being well understood within the art. Camshaft 12 has a drive gear 16 at one end which is engaged by another gear 17. Gear 17 is a component of the engine drive train, coupled directly or indirectly to the engine crankshaft, so that the timing of operation of the fuel injection pump 11 is thereby related to the movement of the associated engine pistons.

Drive gear 16 and gear 17 are enclosed by a housing 18 having an adapter section 19 with a bore 20 through which the end of camshaft 12 extends to receive the drive gear.

As hereinbefore discussed, optimum engine performance requires that the timing of fuel injection relative to piston movement be advanced as engine speed increases and retarded as speed decreases. Automatic mechanism for this purpose is contained within the drive gear 16 and adjacent end of camshaft 12. One component of such mechanism is a spline connection 21 coupling the end of camshaft 12 to an annular axial projection 22 of drive gear 16. Axial movement of camshaft 12 is prevented by a thrust washer 23 in bore 20 so that one effect of the spline connection 21 is to provide for axial movement of the drive gear 16 relative to the camshaft and relative to gear 17.

The splines of connection 21 are helical so that any such axial movement of the drive gear 16 results in rotation of the camshaft 12 relative to the drive gear. Thus if the axial position of the drive gear 16 is varied in response to changes in engine speed, the desired advanc ing and retarding of timing can be effected.

Considering now the means for automatically varying the axial position of drive gear 16 in response to changes in engine speed, a circular concavity 24 in the side of drive gear 16 which faces away from camshaft 12 is closed by a disc 26 secured to the rim of the concavity by an annular flexible diaphragm 27, the concavity, disc and diaphragm being centered on the rotary axis of the drive gear to define a vortex chamber therein as will hereinafter be discussed in more detail.

A rod 28 has a first end secured to the center of disc 26 by a nut 29 and extends through an axial bore 31 in the drive gear 16 and into an axial bore 32 in the adjacent end of the camshaft 12. Bore 31 of the drive gear 16 has a diameter conforming to that of rod 28 while bore 32 in the camshaft is of substantially greater diameter except for terminal portion 33 which is of reduced diameter to receive and pilot the end of rod 28.

A compression spring 34 is disposed coaxially around rod 28 within the camshaft bore 32 and bears against a flange 36 on the rod, with the fixed end of the spring being abutted against a lip 37 on a sleeve 38 which is held in bore 32 by a snap ring 39. Spring 34 thus exerts a force which tends to move the rod 28, and thus drive gear 16, towards camshaft 12.

A similarly directed axial force on the drive gear 16 is generated, when the gear is being turned by gear 17, by the torque at the helical splines of connection 21. Inward movement of the drive gear 16 in response to these combined forces acts to shift camshaft 12 angularly in such a manner as to retard the engine timing as hereinbefore described.

To create a normally counterbalancing axial force on the drive gear 16, rod 28 functions as a spool valve controlling a fluid pressure exerted against the drive gear. For this purpose, a section of the rod 28 adjacent the inner end of drive gear bore 31 is of reduced diam ter forming a flow passage 41 which coacts with control edge 42 of bore 31. Radially directed passages 43 in the drive gear 16 communicate bore 31 with the vortex chamber 24 therein. Engine lubricating oil is admitted to camshaft bore 32 through a fitting 44 on housing section 19 and passage 46 and apertures 47 in flange 36 of rod 28 transmit such oil to the chamber 48 between drive gear 16 and the end of camshaft 12. The pressure of such oil in chamber 48 acts against the adjacent surface 49 of the drive gear 16 and tends to move the gear away from camshaft 12 thereby tending to advance engine timing through the action of the helical spline connection 21.

The amount of pressure which the oil in chamber 48 exerts against drive gear 16 is varied in response to engine speed changes through the spool valve action of the rod 28. In particular, oil continually flows into chamber 48, through passage 46 which has a flow restriction 51 and flows out of the chamber past the control edge 42. From control edge 42 such oil passes through bores.31 and 43 of the drive gear 16 into the vortex chamber 24 thereof and subsequently passes out of the vortex chamber into housing 18 through apertures 52 in disc 26, the oil then being returned to the lubricating oil circulation system of the engine. The oil flow past control edge 42,

and thus the oil pressure within chamber 48, varies in response to axial movement of the control rod 28.

The axial position of rod 28 is turn responsive to engine speed inasmuch as the oil volume 53 within the vortex chamber 24 rotates with the drive gear 16 and is subjected to centrifugal force which generates pressure tending to force disc 26 and rod 28 outwardly away from camshaft 12 against the action of spring 34.

Rod 28 is not affected by oil pressure other than that within vortex chamber 24 inasmuch as bores 31 and 33 are of equal diameter. In order to avoid an accumulation of oil within bore 33 which would react against the rod 28, a drain passage 54 connects bore 33 with a fitting 56 on housing section 19 to return any oil within bore 33 to the engine circulation system. For similar reasons, a drain passage 57 connects fitting 56 with the region of bore 20 adjacent the end of projection 22 of drive gear 16.

In operation, drive gear 16 is urged inwardly towards camshaft 12 by the action of spring 34 combined with the torque generated axial force of helical spline connection 21. Such forces are opposed by the oil pressure exerted against surface 49 of the drive gear 16. At constant engine speeds these opposed forces are balanced to maintain the drive gear 16 at a fixed axial position at which optimum engine timing is obtained. If engine speed increases, drive gear 16 turns more rapidly increasing the centrifugal force on the oil volume 53 within vortex chamber 24. Oil 53 then exerts a greater pressure against disc 26 thereby unbalancing the forces acting on rod 28 and causing the rod to move outwardly from camshaft 12. Such movement of rod 28 reduces the flow aperture past control edge 42 and therefore raises the oil pressure within chamber 48. The increased pressure within chamber 48 reacts against surface 49 moving the drive gear 16 outwardly and thus, through the action of the helical spline connection 21, advancing timing.

Upon a decrease in engine speed a reverse action occurs. Drive gear 16 turns more slowly decreasing the centrifugally generated oil pressure against disc 26. Rod 28 is therefore drawn inwardly by spring 34 and the torque produced axial force at connection 21, which increases the flow passage past control edge 42 and lowers oil pressure Within chamber 48. Less outward pressure is then exerted against drive gear 16 with the result that the gear also moves inwardly and retards the engine timing.

The angular adjustment of camshaft 12 by axial movement of drive gear 16 does not require helical splines in connection 21 if the drive gear itself has helical teeth rather than being a spur gear as in the embodiment of FIGURE 1. Such adjustment is also accomplished if both the splines of connection 21 and the teeth of gears 16 and 17 are helical.

Many modifications of the invention are possible. In the embodiment of FIGURE 1, for example, the timing adjustment is determined by the centrifugally generated oil pressure in vortex chamber 24. However the axial movement of drive gear 16 to make the adjustment is effected by the oil pressure in chamber 48 which in conjunction with the spool valve action of rod 28 functions as a. form of hydraulic booster. By making the vortex chamber relatively larger, and making certain further modifications, it is possible to dispense with the hydraulic booster and to utilize the centrifugally generated oil pressure directly to move an element to make the timing adjustment. The moving element need not necessarily be the camshaft drive gear. The drive gear may be fixed against axial movement, for example, while arranging for a section of the camshaft itself to move axially in response to the oil pressure changes. An embodiment of the invention employing both of these modifications is shown in FIGURE 2.

Referring now to FIGURE 2, there is shown one end of a camshaft 58 which operates a fuel injection system as in the embodiment of FIGURE 1. A helical spline connector 59 couples camshaft 58 to a camshaft extension 61 which is coaxial therewith and journalled in an adapter member 62. At the side of adapter 62 opposite from camshaft 58 a drive gear 63 is disposed coaxially on the camshaft extension 61 and engaged therewith by a second helical spline connection 64. Axial movement of the drive gear 63 is prevented by a thrust washer 66 secured to adapter 62. Thus, through the action of the two helical spline connections 59 and 64, longitudinal movement of the cam shaft extension 61 will turn camshaft 53 and effect timing adjustments in a manner analogous to that of the mechanism of FIGURE 1.

The gear 63 is engaged with a gear 67 which forms part of the engine gear train and thus is coupled directly or indirectly, to the engine crankshaft. Gears 63 and 67 are enclosed by a cover 68 secured to adapter 62 to form a closed gear housing in conjunction therewith.

Considering now the means by which axial movements of the camshaft extension 61 are effected to adjust timing, a vortex chamber is provided in drive gear 63 by a concavity 69 in the side of the gear which faces away from adapter 62. Chamber 69 is closed by a circular plate 71 secured at the side of the drive gear 63 and which supports a cylindrical housing 72 that is coaxial with the gear and into which the outer end of camshaft extension 61 extends. A compression spring 73 is disposed wihtin housing 72 between the end of camshaft extension 61 and threaded spring tension adjustment 74 which projects from the end of the housing. Spring 73 thus urges the camshaft extension 61 towards camshaft 58 tending to retard timing through the action of the helical spline connections 59 and 64.

To provide a counterbalancing axial force on the camshaft extension 61 under steady operating conditions, a disc 76 is secured to the camshaft extension within vortex chamber 69 in coaxial relationship thereto. Disc 76 has a diameter similar to that of the vortex chamber 69 and is slidable therein with the camshaft extension 61. Engine lubricating oil 75 is admitted to the vortex chamber through a passage 77 in adapter 62 which communicates with a groove 78 on camshaft extension 61. Groove 78 in turn is communicated with the region between disc 76 and drive gear 63 by a passage 79 extending Within the camshaft extension 61. Apertures 81 in disc 76 and apertures 82 adjacent plate 71 provide for the escape of such oil into the housing formed by adapter 62 and cover 68 from which it may be returned to the engine lubricating system.

In operation, with the engine at a constant speed, the force exerted on camshaft extension 61 by spring 73 is counterbalanced by the force exerted against disc 76 by the centrifugally generated oil pressure in the vortex chamber 69 and the timing remains fixed. Upon an increase in engine speed, the oil pressure against disc 76 increases moving camshaft extension 61 outwardly and advancing timing. Upon a decrease in engine speed such oil pressure also decreases allowing spring 73 to force the camshaft extension 61 inwardly and thereby retard timing.

Inasmuch as the centrifugally generated oil pressure in vortex chamber 69 acts directly to move to the timing adjustment means in the embodiment of FIGURE 2, the vortex chamber is of greater diameter than in the embodiment of FIGURE 1 in order to produce suflicient force.

What is claimed is:

1. An automatic timing adjustment mechanism for an engine of the class having a timing camshaft and a drive gear therefor as operative elements of the engine timing system said camshaft and drive gear being coupled through axially movable means to vary the angular phase relationship therebetween and wherein said drive gear has an annular concavity therein, comprising, in combination, means defining a vortex chamber within said concavity of said drive gear, a volume of liquid contained within said vortex chamber for centrifugally generating a fluid pressure therein which is proportional to the speed of said engine, a resiliently mounted element Within said drive gear exposed to said fluid pressure for said movement in response to changes thereof, and means transferring motion of said resiliently mounted element to said axially movable means for adjusting said angular phase relationship in response to changes in said engine speed.

2. An automatic timing adjustment mechanism as defined in claim 1 wherein said liquid within said vortex chamber is oil derived from said engine, and comprising the further combination of means forming passages for continually circulating said oil through said vortex chamber.

3. An automatic timing adjustment mechanism as defined in claim 1 wherein said means transferring motion of said resiliently mounted element to said axially movable means is a hydraulically operated force amplifying means operated from the lubricating oil system of said engine and controlled by said resiliently mounted element.

4. An automatic timing adjustment mechanism as defined in claim 3 wherein said drive gear is operativeiy engaged with an end of said camshaft and is movable axially relative there to to vary said angular phase relationship therebetween, said hydraulic force amplifying means being situated between said drive gear and said end of said camshaft to exert said force therebetween.

5. An automatic timing adjustment mechanism for an engine of the class having first and second rotatable members as operative elements of the engine timing system, said first rotatable member being a drive gear coupled to said second rotatable member and being movable in an axial direction relative thereto to vary the angular phase relationship therebetween, means defining a vortex chamber which rotates with said first and second members, said vortex chamber being situated within said drive gear, a volume of liquid contained within said vortex chamber for centrifugally generating a fluid pressure therein which is proportional to the speed of said engine, a resiliently mounted element exposed to said fluid pressure for movement in response to changes thereof, said resiliently mounted element being a movable disc disposed within said drive gear and forming a wall of said chamber whereby said disc moves axially in said gear in response to said changes of fiuid pressure therein, means transferring motion of said resiliently mounted element to said first rotatable member for adjusting said angular phase relationship in response to changes in said engine speed, said motion transferring means having a spool valve rod secured to said disc and extending into an enclosed region between said gear and said second rotatable member and defining a fluid outlet for said region which varies in accordance with the axial position of said spool valve rod, and means for admitting fluid under pressure into said region whereby said fluid exerts an axial force on said drive gear which varies in accordance with the axial position of said spool valve rod.

6. An automatic timing adjustment mechanism as defined in claim 1 wherein at least a portion of said camshaft is movable in an axial direction relative to said gear to vary said angular phase relationship therebetween, and wherein said resiliently mounted element comprises a disc disposed in said vortex chamber in said gear and forming a wall of said chamber, said disc being coupled to said shaft whereby said shaft is shifted axially in response to said changes of fluid pressure in said chamber.

References Cited UNITED STATES PATENTS LAURENCE M. GOODRIDGE, Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,401 ,572 September 17 1968 John M. Bailey It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 41, "roating" should read rotating Column 5, line 24, "wihtin" should read within Column 6, line 4, cancel "said", second occurrence; line 24, "there to" should read thereto Signed and sealed this 17th day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

I Commissioner of Patents Attesting Officer

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