US2063817A - Two-cycle engine - Google Patents

Description

Dec. 8, 1936. M MALLQRY 2,063,817

TWO-CYCLE ENGINE Filed July 3, 1935 5 Sheets-Sheet 1 Dec. 8, 1936. M. MALLORY TWO-CYCLE ENGINE Filed July 5, 1935 5 Sheets-Sheet 2 Dec. 8, 1936. M. MALLORY TWO-CYCLE ENGINE Filed July 3, 1935 5 Sheets-Sheet 3 ill Dec. 8, 1936. MALL 2,063,817

TWO-CYCLE ENGINE Filed July 5, 1935 5 Sheets-Sheet 4 amen tom Dec. 8, 1936. MALLORY 2,063,817

TWO-CYCLE ENGINE Filed July 5, 1955 5 Sheets-Sheet s Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to a two-cycle engine of the type having a pair of cylinders arranged side by side and connected at the top by a common combustion chamber. In the present embodiment, I have shown six pairs of such cylinders ,in line, operating as a six-cylinder engine.

One of the principal objects of the invention is to provide a two-cycle engine in which all exhaust gases will be completely swept from the combustion chamber, and especially from the region of the spark plug, before the time of the next ignition, so that the ignition will always take place in a fresh charge of fuel. Special provision has been made for insuring this result when the engine is idling or operating under a light load, as well as when the throttle is open.

Another object of the invention is to charge the cylinders at idle and low speed at the extreme lower end of the stroke in order to lessen the mixing of the fresh and residual gases.

The above and other objects and advantages of the invention will be specifically explained in the following detailed description and particularly pointed out in the appended claims.

In the accompanying drawings,-

Fig. 1 is a sectional plan view of an engine embodying the invention.

Fig. 2 is a vertical section taken through one cylinder unit and the intake manifold.

Fig. 3 is a-view partly in elevation and partly in section of the air compressor.

Fig. 4 is a side elevation of the air compressor.

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 3.

Fig. 6 is an elevation of the gilled valve on the air compressor.

Fig. 7 is a section taken on the line 'I-I of Fig. 6.

Fig. 8 is a view similar to Fig. 2. illustrating a modified form of the invention.

Fig. 9 ,is a side elevation of the throttle and relief valve control illustrated in Fig. 8.

Fig. 10 is a view similar to the upper part of Fig. 2, illustrating another modification.

Fig. 11 is a detail sectional view through one of the crank shaft bearings.

Fig. 12 is a section taken on the line l2l2 of Fig. 11.

As shown in Figs. 1 and 2, the engine comprises a base or crank case I to which the cylinder block 2 is suitably secured by bolts 3 or the like. Each expansion chamber comprises a comparatively large main cylinder 4, which may be termed the power cylinder, and a comparatively small cylinder 5, which may be termed the intake cylinder.

The two cylinders 4 and 5 are connected at the top through a port 6. The block 2 may be designed for any desired number of cylinders. For smooth operation, it is desirable to have six sets of cylinders in line, as shown in the drawings. This may properly be termed a six-cylinder engine, since there are six combustion chambers.

The cylinder 5 has, arranged about its periphery, intake ports I from a chamber 8 to which fuel mixture is supplied from a manifold 9. The cylinder 4 has exhaust ports l0 arranged about its circumference and opening into a chamber H, which is in communication with the usual exhaust manifold.

The large piston l3 in the cylinder 4 has a connecting rod I4 formed with a large bearing l5 on the crank shaft 16. This bearing has a cap ll connected by a hinge pin l8 and bolt IS. The connecting rod 20 for the small piston 2| in the cylinder 5 is connected to the hinge'pin Hi.

It will be understood that toward the end of the power stroke, the piston I3 uncovers the exhaust ports l0 and shortly thereafter the piston 2| uncovers the intake ports 1 to permit the fresh fuel charge to follow and drive out the exhaust gases. The wall of the combustion chamber is shown as having two spark plug holes 22 and 23, the spark from the first plug being mainly effective at idling, when the volume of the charge is small, and the spark from the second plug being mainly effective when the engine is operating under a considerable load. I

It will be noted that the crank shaft I6 is offset considerably from the center line of the large cylinder 4. This would' cause a side.

thrust on the outer side of the large piston I3, which would cause considerable wear and short piston life, were it not for the fact. that the hearing for the small piston connecting rod 20 is mounted on an extension of the bearing l5. By this arrangement, the downward pressure of the small piston 2| causes a clockwise turning efiort on the master connecting rod H, as .viewed in Fig. 3, which neutralizes the thrust on the left for the main fuel passageway and a small valve 41 for the idling passageway. The valves 46 and 41 are in planes approximately at right angles to each other, so that when the main valve 46 is closed the valve is open and vice versa.

Air under pressure is supplied to the main air inlet 48 through a pipe 49 leading from a manifold 50 attached to an air compressor or charger 5I (Figs. 1, 3, 4, and 5), which is mounted at one end of the engine. The air compressor, in the present instance, has four cylinders 52, in which pistons 53 reciprocate. One of the piston rods, as 54, has a bearing 55 on a crank pin 56 which is an extension of the crank shaft IS. The cap 51, which is a part of the bearing 55, has bearing pins 58 for the inner ends of the other three piston rods 59. The head of each cylinder 52 is provided with an intake port 60 and an outlet BI. The flow of air is controlled by a valve 62, which preferably comprises series of gills. As shown in Figs. 6 and 7,,the first or largest gill 63 is slightly larger than the hole 64 that it covers, and this gill has a hole 65 that is covered by another gill 66 and so on, each successive gill being smaller than the preceding gill but larger than the hole in the latter. Under some conditions, a backing plate 61 is provided to limit the movement of the valve at high speeds. With this gilled type of construction, the whole valve assembly opens only slightly and its action is more like breathing than the usual valve operation. Since the amplitude of the valve movement is considerably less, it will operate at a much higher speed and has better volumetric efliciency than a conventional reed valve.

Oil is supplied for crank shaft lubrication through an oil manifold or passageway I0 (Figs. 11 and 12) to a continuous groove II extending circumferentially about the outside of the main bearing I2 in which the crank cheek I3 is mounted. A feed hole I4 is drilled on the power side of the bearing about 45 from bottom center. This feed hole delivers oil into a groove I5 in the bearing surface, which extends from a point midway of the power side of the bearing to about 20 past bottom dead center. Holes I6 and 11 are drilled diagonally through the crank shaft to supply oil to the connecting rod bearings, each of the latter being provided with a circumferential groove I8.

In the modification illustrated in Figs. 8 and 9, air under pressure is supplied through the main air inlet chamber I9 to the main venturi 80, which has a fuel inlet 8|. The mixture flows from the venturi past the main throttle valve 82, carried by the throttle shaft 83, to the mixture inlet chamber 84, whence it passes into the cylinder 5 through the intake port 85. Air is also supplied to the cylinder 5 through a passageway 86 and port 81, the air flow through this passageway being controlled by a valve 88 which is mounted on the throttle shaft 83 in the same plane as the valve 82. In the normal operation of the engine, the port 81 is uncovered before and closed after the port 85, so that the cylinder is supplied with a stratified charge; that is, the fuel mixture is sandwiched in between two layers of pure air. The first layer of air serves as a scavenger and also prevents the loss of unburned fuel.

At idling or low speeds, air enters the small venturi 89, which is provided with a fuel inlet 90 and which also leads into the mixture inlet chamber 84. The outlet from the small venturi is shown as provided with a valve 9| disposed in a plane approximately at right angles to the plane of the main throttle valve 82, but the valve 9| may be omitted, if desired. As speed and load are increased, the flowfrom the large ven-- turi 80 is progressively increased and at the same time the air passageway 86 is progressively opened.

Connected with the air inlet chamber I9, there is a valve chamber 92 containing a relief valve 93 which has an arm 94 connected by a tension spring 95 to the throttle valve arm 96. As the throttle valve 82 is opened, the tension on the spring 95 is increased, which increases the charging pressure. Thus, at light loads, the charger or compressor is operating under lower pressure and, therefore, does not consume as much power as if the relief valve spring were set at a fixed tension for maximum pressure.

The combustion chamber Ii has a very small space immediately above the piston 2| and is designed to have very little turbulence preceding the time of ignition, so that the ignition will always take place in a fresh charge of fuel mixture. Therefore, the engine fires evenly, even at the lightest loads, and has no tendency to four-cycle as is the case with a conventional two-cycle engine.

It is to be noted that the intake cylinder 5 is considerably smaller than the main power cylinder 4. In fact, the cross-sectional area of the cylinder 5 is approximately equal to the intake port area and intake manifold area. Thus, the small cylinder 5 may be considered a continuation of the intake manifold 9 and the small piston 2I assumes the role of a valve in the intake passageway. Since the intake cylinder bore is relatively small in cross section, this small cylinder is swept clear of all exhaust gases.

In Fig. 10, another modification of the induction system is disclosed. Here, the fuel charge for power is supplied to the intake port I00 from the main venturi ml, which is provided with the fuel inlet I02. For idling, the fuel charge is supplied to the intake port I03 from the small venturi I04, which is provided with the fuel inlet I05. The throttle shaft I06 carries a main throttle valve I01 and a small valve I08, in planes approximately at right angles to each other.

With this arrangement, a good quality of idling is obtained, because when the throttle valve I0I is closed, the incoming mixture is not admitted to the cylinder until the lower port I03 is opened. By the time the piston 2| has traveled this far down, the exhaust pressure is much lower than it would be at the time the piston uncovers the upper port I00. In two-cycle engines, the cylinder pressure resists the incoming mixture and this disturbs the idling operation, but with this construction, the cylinder pressures are not exposed to the fresh mixture until the piston has practically reached the extreme end of its down stroke. The throttle valve I08 may be eliminated, if desired. Then, when the throttle valve I0'I is closed, the idling mixture will still be formed inthe venturi I04. The only difference will be that when the throttle valve I01 is open, the engine will run on both venturis for power. It is believed very desirable to have as constant a flow as posible through the small venturi at low speed. In a four-cylinder engine, that is, an engine with four suction strokes per revolution, this is difficult to accomplish. However, in a six-cylinder engine having six suction strokes per revolution, uniform flow can be accomplished for all practical purposes.

While I have shown and described in detail various embodiments of the invention, it will be understood that these are merely illustrative and that the invention embraces all variations which fall within the scope of the appended claims.

I claim:

1. In a two-cycle engine, a cylinder, a fuel mixture chamber leading thereto, a large venturi and a small venturi arranged side by side and leading to said chamber, a common compressed air supply for said venturis, fuel supply jets opening into the respective venturis, and throttling means to close the large venturi and open the small one for idling, or to close the small venturi and open the large one for power.

2. In a two-cycle engine, a cylinder, a fuel mixture chamber leading thereto, a large venturi and a small venturi arranged side by side and leading to said chamber, a common compressed airsupply for said venturis, fuel supply jets opening into the respective venturis, and throttle valves disposed in planes substantially at right angles to each other and controlling the flow through the respective venturis.

3. In a two-cycle engine, a cylinder having two intake ports located one above the other, an air passageway leading to the upper port, a fuel mixture passageway leading to the lower port, a throttle valve shaft, and valves secured to said shaft in the same plane and controlling flow through the air passageway and the fuel mixture passageway respectively.

4. In a two-cycle engine, a cylinder having two intake ports located one above the other, an air passageway leading to the upper port, a fuel mixture passageway leading to the lower port, a large venturi and a small venturi arranged side by side and both leading into said passageway, a common compressed air supply for the air passageway and the two venturis, and valves operable to increase or diminish the flow through the air passageway and the large venturi simultaneously.

5. In a two-cycle engine, a cylinder having two intake ports located one above the other, an air passageway leading to the upper port, a large venturi and a small venturi arranged side by side and leading to the lower port, a common compressed air supply for the air passageway and the two venturis, fuel jets opening into the respective venturis, valves operable to increase or diminish the flow through the air passageway and the large venturi simultaneously, and a third valve controlling the flow through the small venturi and adapted to close as the other valves open and to open as the other valves close.

6. In a two-cycle engine, a cylinder, a large venturi supplying fuel mixture to said cylinder for power, a small venturi supplying mixture to said cylinder for idling, compressed air supply means for the venturis, a throttle valve controlling flow through the large venturi, a relief valve limiting the air pressure, and means to lower the pressure limit as the throttle valve is moved toward closed position.

'7. In a two-cycle engine, a cylinder, a large venturi supplying fuel mixture to said cylinder for power, a small venturi supplying mixture to said cylinder for idling, compressed air supply means for the venturis, throttle valves controlling fiow through the respective venturis, one of said valves being adapted to open as the other closes and vice versa, a relief valve limiting the air pressure, and means to lower the pressure limit as the throttle valve for the large venturi is moved toward closed position,

8. In a two-cycle engine, a cylinder having two intake ports located one above the other, a large venturi leading to the upper port, a small venturi leading to the lower port, a common compressed air supply for the two venturis, said venturis being arranged side by side, fuel supply jets opening into the respective venturis, and a throttle valve controlling flow through the large venturi.

9. In a two-cycle engine, a cylinder having two intake ports located one above the other, a large venturi leading to the upper port, a small venturi leading to the lower port, said venturis being arranged side by side, a common compressed air supply for the two venturis, fuel supply jets opening into the respective venturis, and throttle valves controlling flow through the respective venturis, one of said valves being adapted to open as the other closes and vice versa.

MARION MALLORY.

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