US2787987A

US2787987A - Braking device for two-stroke cycle internal combustion engines

Info

Publication number: US2787987A
Application number: US396555A
Authority: US
Inventors: Portmann August
Original assignee: Adolph Saurer AG
Current assignee: Saurer AG
Priority date: 1952-12-18
Filing date: 1953-12-07
Publication date: 1957-04-09
Anticipated expiration: 1974-04-09

Description

Apnl 9, 19517v A. PoRTMA'NN EEAKINC DEVICE EOE Two-STROKE CYCLE INTERNAL coMBusIIoN ENCINEs Enea nec. 1, 195s United States Patent O BRAKING DEVICE FOR TWO-STROKE CYCLE INTERNAL COMBUSTIGN ENGINES August Portmann, Arhon, Switzerland, assignor to Societe Anonyme Adolphe Saurer, Arbon, Switzerland, a jointstock company of Swiss law Application December 7, 1953, Serial No. 396,555

Claims priority, application Switzerland December 18, 1952 s Claims. (ci. 12s-ss) This invention relates to internal combustion engines and more especially to means for braking two-stroke cycle engines.

In the operation of internal combustion engines of the two-stroke and the four-stroke cycle types an additional braking effect has been obtained by so adjusting the control of the intake and the exhaust ports during brake operation that the compressed cylinder charge is exhausted at the end of the compression stroke into the exhaust pipe. The compression and pumping work raises the driving turning moment of the motor used for braking, but a device of this kind involves the drawback of developing great noise.

It is for this reason that one has tried in four-stroke cycle engines, when braking, to throttle the exhaust and to obtain in this manner an increase of the driving turning moment of the engine by an increase of the exhaust work. Such a device is more favorable as far as noise is concerned, and it offers, in addition, the advantage of being able to regulate the braking effect by varying the throttling effect in the exhaust pipe.

I have now found that in the operation of two-stroke cycle engines provided with positively controlled exhaust organs at the end of the cylinder facing the combustion chamber, it is possible to obtain a similarly favorable braking effect, if in the operation of the brake the conx trol of the exhaust organs is adjusted in such a manner that they are open at least during a considerable part of the compression stroke, while the exhaust conduit is throttled simultaneously by a Valve or the like.

In the drawings afiixed to this specification and forming part thereof two embodiments of a device according to this invention are illustrated diagrammatically by Way of example.

In the drawings:

Fig. 1 is a vertical section of an internal combustion engine containing a braking device.

Fig. 2 is an axial section of a device according to this invention for the adjustment of the cam shaft 11 appearing in Fig. 1.

Fig. 3 is a similar view of another embodiment of a device according to this invention for adjusting the cam shaft.

Fig. 4 is a cross-section on the line IV--lV in Fig. 3.

Figs. 5 and 6 are diagrams illustrating the system of braking an engine in accordance with this invention, and

Fig. 7 is the distribution diagram of the engine shown in Fig. l.

Referring to the drawings and first to Fig. 1, the cylinder 1 embedded in the engine casing 2 contains the working piston 3 which is driving the crank shaft 5 with the aid of the connecting rod 4. The upper edge 6 of the piston controls the intake ports 7 of the cylinder. The crank shaft 5 also drives the cam shaft 11 by means of gears 8, 9 and 1i). The cam 12 of the shaft 11 opens by means of the tappet 13 and lever 14 the exhaust valve 15 against the action of the spring 16. The gear ice 9 drives by way of a pinion 17 the scavenging and charging blower 18 which feeds air into the receiver 19 and into the cylinder 1 when the ports 7 are uncovered by the edge 6 of the piston 3. The valve 15 opens into the

exhaust conduits

20 and 21 which are separated by the valve 22. The exhaust ports of all the cylinders of the engine open into the port 20 of the exhaust conduit in front of the shut-olf valve 22. The branch tube 24, opened and closed by the throttling valve 23, connects the pressure side of the scavenging blower 18 with the exhaust conduit 21 located behind the cut-off valve 22. The operating lever 25 is connected by means of the rod 26 with the throttle valve 23 so that while the exhaust valve 22 is closed, the throttle valve 23 is opened approximately in proportion to the total time-crosssection of the engine. While this engine operates as a motor, the throttling valve 23 is closed. This valve might also be designed to act as a safety valve and in that case the rod 26 would be dispensedwith.

The oil pump 35 of the engine communicates by way of the pipe 31 with the reversing valve 32, from which

pipes

33 and 34 lead to one and the other pressure chamber of the piston sleeve of the stationary cylinder switch 36. The reversing valve 32 is connected by means of the rod 37' with the lever 25 controlling the valve 22 in such a manner that immediately the lever 25 has been moved, reversal is eected so that from then on until the lever has gone through his full stroke, merely the spring 3S is compressed.

As shown in Fig. 2, one end (42) of the cam shaft 11 is coarsely threaded and is connected by means of the piston sleeve 35 with the shaft 41 which is also formed with a coarse thread. In consequence of this, the shaft 11 can be turned through an angle a relative to the shaft 45 by displacing the sleeve piston 35. The gear 10 is keyed onto the shaft 40.

The hollow piston 35 is held in one or the other position by oil pressure. Of course, oil pressure might also be used to hold the piston in one position only against the presssure of a spring.

Another way of angular adjustment of the cam shaft 11 relative to the driving gear 50 is illustrated in Figs. 3 and 4. Here the cam shaft 11 carries at its left-hand end an angularly adjustable piston 51 with two vanes 52 and 53 which can be turned one way or the other within the hollow gear 5t). The piston 51 thus subdivides the interior of the gear 50 into four compartments 54-57. The hub portion of the piston is perforated in such manner that the

compartments

55, 57 communicate via the annular compartment 58 with the pipe 34, the

compartments

54, 56 via the annular compartment 59 with the pipe 33. Corresponding to the pressure in the

pipes

33, 34 the piston 51 and with it the cam shaft are turned through a predetermined angle a relative to the driving gear 55. instead of this, a planet gear might be used, in which the stationary part could be turned angularly.

in the diagram of Fig. 5 the full line shows the progress of the pressure p in a cylinder of the engine in dependence on the crank angle fp which results when the engine is driven from the outside without a supply of fuel.

In the diagram of Fig. 6 the full lines denote the coordinate times of opening of the intake ports 7 and exhaust control 15.

The cycle of operation begins with the inward stroke of the piston. At the beginning of the stroke the intake ports 7 and the exhaust control 15 are open, the cylinder is scavenged. Shortly before the closing of the intake ports the exhaust control has been closed so that the cylinder is charged up to the pressure in the receiver. As the piston then proceeds inwardly, the air is compressed according to curve a. During the now follownimmer a. di ing outward stroke of the piston the air in the cylinder expands according to curve b. Since the surfaces below the curves a and b are of equal or approximately equal size, the braking effector the l engine merely consists of the frictional work and the Work required by the scavengingrand charging blower.

If the engine is intended to be used for braking, the exhaust conduit 20 is throttled by turning the lever 2S, the fuel supply being shut off, and the reversing valve 32 is so adjusted by means of the rod 37 that the oil pressure supplied by the oil pump 30 displaces the sleeve piston 3S, thereby so `adjusting the cam shaft 11 that the exhaust valve 15 is opened after the working piston, as line A1 (Fig. 6) shows, has covered the intake ports 7. The air now flows along line c from the hrottled exhaust conduit 20 into the cylinder 1, so that the piston 3 is forced to expel the air along line d against the pressure in the exhaust conduit 20. At the end of the stroke the exhaust control 1S is closed. When the piston 3 now moves outwardly, the air in the cylinder t expands according to curve e Vconsiderably below the pressure in the receiver. .Shortly before the end of the stroke the piston 3 uncovers the intake ports 7 and the cylinder 1 is now charged up to the pressure in the receiver,

In the distribution diagram of Fig. 7 the exhaust control15 is opened during operation as a motor over the angle ,B and over the angle 'y the piston 3 uncovers the intake ports 7. During braking the opening period of the exhaust control 15 is displaced by the angle a..

I wish it to be understood that l do not desire to he limited to the details described in the foregoing specifi cation and shown in the drawings for obvious modifications will occur to a person skilled in the art.

I claim:

1. Braking system for two-stroke cycle internal rcombustion engines comprising in combination, a cylinder, a piston arranged for reciprocation in said cylinder, an exhaust conduit connected with said cylinder, an exhaust valve connected with said conduit, means for controlling said valve, means for so adjusting the exhaust valve control that the valve s kept open during a considerable part of the compression stroke of the piston and means for simultaneously throttling the exhaust conduit.

2. Braking system for two-stroke cycle internal combustion engines comprising in combination, a cylinder,

a piston arranged for reciprocation in said cylinder, an exhaust conduit connected with said cylinder, an exhaust valve connected with said conduit, a cam shaft controlling said valve, means for so adjusting the angular position of said cam shaft that said valve is kept open during a considerable part of the compression stroke of the piston and means for simultaneously throttling said exhaust conduit.

3. Braking system for two-stroke cycle internal combustion engines comprising in combination, a cylinder, piston arranged for reciprocation in said cylinder, an exhaust conduit connected with said cylinder, an exhaust valve connected with said conduit, a cam shaft controlling said valve, a hollow driving gear operatively connected with said cam shaft, a rotary distributing valve in said gear and means for so adjusting the position of said valve relative to said gear that said valve is kept open during a considerable part of the compression stroke of the piston and means for simultaneously throttling .said exhaust conduit.

4. The braking system of claim 1 in combination with a blower, a pipe leading from the pressure side of Vsaid blower to the exhaust conduit, a throttling device inserted in said pipe and a connection between the exhaust conduit throttling means and said throttling device ar ranged for opening said device when said throttling means close.

5. The braking system of claim l in combination with a blower, means for connecting the pressure side of said blower with the exhaustconduit and a safety valve in said connecting means, whereby to pass air from said side of the blower to the exhaust conduit when due to throttling of said conduit, the pressure on said side of the blower exceeds a predetermined value.

References Cited in the tile of this patent UNITED STATES PATENTS 876,020 Salter Jan. 7, 1908 1,518,799 Krutina u Dec. 9, 1924 1,624,525 Beach Apr. 12, 1927 1,829,780 Beytes et al. Nov. 3, 1,931 2,037,051 Smiley Apr. 14, 1936 2,148,854 Bokemuller Feb. 28, 1939 2,178,152 Walker Oct. 3l, 1939