US2374411A - Means for controlling the fuel supply in two-stroke internal-combustion engines - Google Patents

Description

v April 24, 1945. H. G. cAMNr-:R

M H H H H l 52 29/K//A A O /75 ,ll/25 85 MNHN "7 W 55 afm /E n es J3 www l 7 l 28 2 9. I 55 pnl 24, 1945. H. G. cAMNx-:R 2,374,411

MEANS FOR CONTROLLING THE FUEL SUPPLY IN Two-STROKE INTERNAL-COMBUSTION ENGINES Filed Nov.r '7, 1939 3 Sheets-Sheet 2 INVENTOR /f/LD//vq gamme CAMA/5R BY 2,374,411 -STROKE 3 Sheets-Sheet 3 H. G. CAMNER April 24, 1945.l

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INVE N TOR lmp/Mq 6am/HR CAMA/5R BY M www Patented Apr.. 24, 1945 MEANS FOR CONTROLLING THE FUEL SUP- PLY 1N TWO-STROKE INTERNAL-COM- BUSTION ENGINES Hilding Gunnar Caniner, Ektorp, Sweden, assignor to 'Aktlebolaget Atlas Diesel, Stockholm 1,

Sweden Application November 7, 1939, Serial No. 303,221

In Sweden February 18, 1938 (ci. 12s-'140) 7 Claims.

The present invention relates to two-stroke internal combustion engines having a servo-motor controlling the fuel injecting mechanism of the engine and acted on by the scavenging air to control the fuel supply.

The invention has for its object to eliminate that part of the speed diilerence which is related to and may be said to be represented by the change of the scavenging air pressure at varying torques of the engine and comprises essentially means for controlling the'pressure-in the servolmotor with relation to variations of the torque of the engine.

The annexed drawings illustrate diagrammatically some embodiments of a control device according to the invention. Fig. 1 is a side view showing the outlines of an engine having a control device according to one embodiment applied thereto. Fig. 2 is a detail view on an enlarged scale of the control device according to Fig. 1. Fig. 3 is a similar view of a somewhat modiiied control device. Fig. 4 is a side view showing the outlines of an engine having a control device according to a further modication applied thereto. Fig. 5 is a detail view on an enlarged scale of the control device according to Fig. 4. Figs. 6 and 7 show two embodiments of manually operable control devices.

Referring rst to Figs. l and 2, M designates the engine proper and P the scavenging'air pump thereof driven by the engine in any ordinary convenient manner. The fuel injecting mechanism, which is assumed t be of any known construction and vfor'such reason need not be particularlyI described, is denoted by I and its control member by 2. Joined to the said control member is the one arm of a double-armed lever 3, the stationary fulcrumof which comprises an interior oi the housing of which communicates with the cylinder chamber 8 through a pipe I4 and which is adapted to control an outlet i5 in the housing for the scavenging air in order to change the pressure in the said chamber 8, as will be described more particularly below. The piston valve I3 is connected to a damping piston I6 moving. in a bore I1 in thevalve housing and iitting either tightly in the said boreV and havinga small diameter channel vI8 communicating with an outlet I9 in the valve housing, as shown, or having a certain clearance in the bore, in which case the channel I8 and the outlet I9 can be dispense'd with. J y

Displacement of the control member 2 in the direction from the right towards the left in Figs.

1 and 2 is assumed to increase the fuel supply Y to the engine, whereas displacement'of the said adjustable eccentric 4, and the other arm of which is pivotally connected to the piston rod 5 of a servo-motor comprising a cylinder 6 and a piston 1 movable therein. The space 8 within the cylinder at'the right side of the piston 1, as viewed in Fig. 2, communicates through a pipe 9 with the scavenging air receiver of the engine or with any part of the scavenging air conduit, while the chamber I0 at the opposite side of the piston may communicate through a pipe Il with the exhaust pipe of the engine at a place located between the engine and a throttling member in said pipe. The piston 1 is also acted on by a spring I2 counter-acting the pressure in the cyliner chamber 8. Y

Connected to the control member 2 of the fuel injecting mechanism is a piston-slide valve I 3, the

member in the opposite direction decreases the supply.

Based on the above assumption, the arrangement operates in the following manner.

If the engine be set for a certain speedl and the torque of the engine decreases, the speed will increase, whereby the scavenging air pressure rises and the piston 1 moves the control member 2 towards the right, to thereby decrease the fuel supply, until said supply corresponds to the decreased torque. At an increased torque the speed of the engine and thus also the scavenging air pressure decreases, whereby the piston 1 under the action of the spring I2 moves the control member 2 to the left to thus increase the fuel supply, until an equilibrium occurs between the fuel supply and the torque.

By adjusting the eccentric I or by altering the initial tension of the spring I2, the speed of the engine can be altered.

However, it is characteristic of the operation of engines of the kind under consideration that the scavenging air pressure increases and decreases with increase and decrease, respectively, of torque even if the speed ,remains constant, due to the increase of exhaust .back pressure with increase in charge needed to produce the same speed with increased torque.

Thus, it is not possible by the servo-motor alone vto obtain a suiilciently accurate control under all conditions.

As a matter of fact, the speed difference at full load and in idling will be relatively great.

If, for instance, the engine runs at full load at a certain speed and the torque is then decreased to zero, the speed of the engine must increase to such an extent that the scavenging air pressure obtains the saine value as at full torque, and, besides, a further increase in speed must occur in order to raise the scavenging air pressure suiliciently to move the piston 1 to the idling position.

That part of the speed difference, which is related to the variation of the scavenging pressure at varying t'rques, is unavoidable in the arrangement with the servo-motor only. The second part or the speed diierence is defined by the dimension of the spring I2,

In order to eliminate that part of the speed diilerence, which is related to the variation of the scavending air pressure at variations of the torque, or in other words to keep the speed constant independent of such variations, the pistonslide valve I3 is provided. The said valve is so adjusted as to be more or less open, when the enthe scavenging air receiver. When the torque increas, the piston I will move towards the left, and the porti is uncovered more and more and will be wholly opened, for-'instance at the maximum torque, which results in a decrease of pressure in the cylinder chamber 8* in accordance with the action of the piston-slide valve I3 according to Figs. 1 and 2.

In order to prevent oscillations a damping piston 22 is connected directly to the servo-motor piston 1, said damping piston having either a certain clearance in a cylinder 23 at the outer end of the servo-motor cylinder l* or tting tightly in said cylinder 23 and being provided with a .small channel 2l, as shown, which forms a communication between the damping cylinder 23 and gine runs for instance at full torque. By the discharge of the air through the outlet I in the valve housing a lower pressure exists in the cylinder chamber B than in the scavenging air receiv- 'er or conduit proper, since a certain resistance,

which restricts the air supply from the receiver to the chamber 8, occurs in the pipe 9 leading from the receiver. If desired, any throttling means may be provided in the pipe 9 to increase the resistance. At a decrease of the torque, for instance to zero, the piston valve I3 will move towards its closed position, whereby the air discharge will decrease or wholly cease.

Then, the pressure in the cylinder chamber 3 will approach or be equal to the pressure in the scavenging air receiver. From the above it is apparent that it is rendered possible, by suitably dimensioning the piston-slide valve I3 and the cross-sectional area of the pipe 9 between the scavenging air receiver and the cylinder chamber 8, to maintain the same or even a lower pressure in the said cylinder chamber under conditions of large torque than under conditions of small torque, in spite of the pressure in the receiver being higher at the larger torque than at the smaller one.

As mentioned, in order to change the speed of the engine the initial tension of the spring I2 can be altered. In variable speed engines it is suitable to have the spring I2 actuate the piston I or the control member 2 from theA outside,

whereby the spring tension can be altered by means of a manually operated lever or the like. In order to prevent oscillations, particularly in idling and at low loads, the damping piston I6 -moving in the bore II is used, whereby either the channel I3 or, if such channel is not provided, the clearance between the piston and the bore preferably is so chosen that the air in the bore will check quick control'movements only,

from the one according to Figs. 1 and 2 in that the piston rod 5a of the servo-motor is connected directly to the control member 2 of the fuel injecting mechanism I, necessitating a reversed 1ocation of the cylinder chambers 8 and I0, lBesides, the separate control valve I3 according to Figs. 1 and 2 is replaced by an arrangement in the servo-motor proper. The cylinder wall is provided Wtih a port 20, controlled by the servo-motorpiston la, .in which a channel 2| is made, which communicates with the cylinder chamber 8a and the port 20 in certain positions.

At small torques or in' idling the piston 1a covers the port 20 substantially or wholly, in which the cylinder chamber III in the servo-motor.

Otherwise, the action of the device according to Fig. 3 is the same as that one described above in connection with the embodiment according to Figs. 1 and 2.

The'damping means shown also can be located at any other place of the control device than shown, for instance at the free end of the control member 2.

According to the embodiments above described, their action is based on the principle that the full load scavenging air pressure is lowered towards. or lower than, the idling pressure.

However, in order to eliminate the speed difference as above described it is also possible to increase the idling pressure towards the full load pressure.

An embodiment having such an action is shown in Figs. 4 and 5, in which similar parts are indicated by the same reference numerals as in Figs. l and 2, but with the sufllx b".

According to Figs. 4 and 5 the pipe] communicates with the scavenging air conduit 2i leading from the pump P at a place between the pump and a butterily valve 28 in said conduit. Further, the said pipe 9 has two'branches 21 and 2l, the branch 21 of which leads to the cylinder chamber 8b of the servomotor,'which operates the control member 2 of the fuel injecting mechanism I, as described above, whereas the branch 2l leads to a valve housing 29 having a piston-slide valve 8l movable therein, which controls an outlet 2|, from which leads a pipe 32 to the working chamber I3 of a second servo-motor comprising a cylinder 2l and a piston 35 movable therein. The piston 3i is acted on by a spring which counter-acts the pressure in the chamber 33 and the piston rod Il of which is connected to and operates the valve 26 in the scavenging air conduit 2l, as seen in Fig, 4. The piston-slide valve 3l abuts against the end of the control member 2 and is operated together with said member, the contact between the valve and the control member being maintained by the aid of a spring 33, which also serves to move the valve 30 to the position in which it closes the outlet 3 I.

In the above embodiment a displacement of the control member 2 in the direction from the left towards the right is assumed to increase the fuel supply, whereas a, displacement in the opposite direction decreases the fuel supply.

Now, if the engine is set for a certain speed and the torque of the engine tends to decrease, the speed of the engine will increase, whereby the scavenging air pressure also increases. As a consequence, the pressure in the cylinder chamber lb of the servo-motor 6b, 'Ib increases, and the piston 'Ib will be moved towards the right causing a displacement of the control member 2 towards the left. so as to decrease the fuel supply, until an equilibrium is obtained between the pressure in the chamber 3b and the pressure of the spring |21.

Now, in order to eliminatethat part of tin` cylinder chamber 33 of the servo- motor 34, 35.

The piston 35 is moved towards the right and causes the valve 26 to close more or less. As a consequence, the pressure in the conduit 25, at a place between the air pump and thexilap valve will increase correspondingly and, thus, also the pressure in the cylinder chamber 8V of the servomotor 5R11, so that the piston l'I will be further moved towards the right causing a, further decrease in the fuel supply and thus a reduction in speed, which will now correspond substantially or wholly to the initial speed at the greater torque.

If contrary to the above, the engine is set for a certain speed and the torque of the engine tends to increase, the action of the device described will be reversed causing an increased fuel supply, first by the servo-motor Bb, 'Ib and second by the servomotor 34, 35, the tension of the springs I2b and 36, respectively, now overcoming the decreasing scavengingair pressure.

` The embodiment according to Fig. 6 differs from that one shown in Figs. 1 and 2 only in that the automatic valve device I6 is replaced by a manually operated outlet valve 39, by which the pressure in the servo-motor chamber 8 can be controlled. Thus, at a decreasing torque the valve 39 has to be moved towards its closing position and vice versa.

movement of said element, means connecting said element to said control member, and valve means shiftable in response to movement of said element for modifying the pressure of the air acting on said element sufficiently to compensate for the variation of scavenging air pressure resulting from variations in the torque developed by said engine. 1 Y

2. In a`two-stroke internal combustion engine,

a scavenging air pump driven by the engine, fuel.

injector mechanism including acontrol member, a servo-member including an element movable in response to fluid pressure changes, means for subjecting said element to air supplied by said pump and varying in pressure with variations in scavenging air pressure, resilient means. resisting the movement of said element, meansl connecting said element to said controlmember,

said servo-motor having a passage for bleeding air to the atmosphere to thereby reduce the air pressure to which said element is subjected, and

valve means shiftable in response to movement of said element for varying iiow'through said bleed passage sufficiently to compensate for the variations of scavengingair pressure resulting from variations in the torque developed by said engine.

3. In a two-stroke internal combustion engine,

a scavenging air pump driven by the engine, fuel injector mechanism including a control member,

a servo-motor including a pressure chamber, a

movable element acted on by the pressure of air in said chamber and resilient means resisting movement of said element caused by increased pressure in. said chamber, conduit means for connecting said chamber with said air pump, means connecting said element to said control member, said servo-motor having a passage for bleeding air from said chamber to the atmosphere to 4.0. thereby reduce the air pressure acting on said Similarly, the embodiment according to Fig. 7

differs from that one according to Figs. 4 and 5 only in that the automatic valve 29, 30 and the servo-motor 34, controlled thereby is replaced by a manually operated lever 49 connected to the valve 26 by a linkage 4I. torque the lever 49 has to be swung towards the right to more cr less close the valve 28 and vice versa.

.according to the above described embodiments the control devices have been shown in combination with a fuel injecting mechanism, wherein the fuel quantity supplied to the engine is varied by displacement of the control member 2. It is evident that the invention is applicable also to a fuel injecting pump, wherein the controlling of the fuel quantity is effected by means of an eccentric device er by changing the stroke of the pump plunger or the like. Besides, the motion transmitting means between the servo-motor and the control member of the fuel injecting mechanism may be of any type. This is true also to the servo-motor, which may work with a membrane or the like instead of with a piston.

What I claim is:

ljIn a two-stroke internal combustion engine, a scavenging air pump driven by the engine, fuel injector mechanism including a control member, a servo-motor including an element movable in response to fluid pressure changes, means for subjecting said element to air supplied by said pump and varying in pressure with variations in scavenging air pressure, resilient means resisting the Thus, at a decreasing element, and valve means shiftable in response to movement of said element for varying flow through said bleed passage sumciently to compensate for the variations of scavenging air pressure resulting from yvariations in 4the torque developed b'y said engine.

4. In a two-stroke internalcombustion engine, a scavenging air pump driven by the engine, fuel injector mechanism including a control member,

a servo-motor inclu ing a pressure chamber, a

movable element act d on by the pressure of air in said chamber and resilient' means resisting I movement of said element caused by increased pressure in said chamber, conduit means for connecting said chamber with said air pump, means connecting said element to said control member, and valve means shiftable in response to'movement of said element for modifying the pressure of the air in said chamber sufliciently to compensate for the variations of scavenging air pressure resulting from variations in the torque developed by said engine.

5. In a two-stroke internal combustion engine, a scavenging air pump driven by the engine, fuel injection mechanism including a control member, a servo-motor including a cylinder and a piston movable in said cylinder, resilient means resisting the movement of said piston, conduit means ,for connecting said cylinder with said air pump, means connecting said piston with said control member, and valve means including a port in the wall of said cylinder in communication with the atmosphere and controlled by movement of said piston for modifying the pressure of the air acting on said pistonl suiciently to compen- 6. In a two-stroke internal combustion engine, Y a scavenging air pump driven by the engine. fuel injector mechanism including a control member, a servo-motor including an element movable in response to fluid pressure changes, means for subjecting said element to air supplied by said pump and varying in pressure with variations in scavenging air pressure, resilient means resisting movement of said element, means connecting said element to said control member, Yvalve means shiitable in response to movement of7 said element for modifying the pressure of the air acting on said element suiliciently to compensate for the variations of scavenging air pressure resulting from variations in the torque developed by said engine. and damping means for preventing lation oi said control member.

-'1. In a two-stroke internal combustion engine..

able element acted on-by time pressure o! air in said chamber and resilient means resisting movement of said element caused by increased pressure in said chamber, conduit means for connecting said chamber with said air pump, means connecting said element to said control member, said servo-motor having a'passage for bleeding air from said chamber to the atmosphere to thereby reduce the air pressure acting on said element, a

- valve member for controlling iiow through said sure resulting from variations in torque developed by said engine. f.

. HILDING GUNNAR. CAMNER.

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