JP3217369B2 - engine - Google Patents

Description

The present invention relates to engines, and more particularly to a large two-stroke crosshead engine for propelling a ship, the engine having a plurality of cylinders, each cylinder comprising:
It has a piston connected to an associated throw on the crankshaft common to the cylinders ("slow" herein means a connecting rod pin with a crank arm or a crank pin with a crank arm). The throws are connected via main bearing journals mounted on the main bearings in a predetermined relative angular relationship, this relative angle being different for at least some of the adjacent throws, during the engine cycle. The amount of fuel oil injected into the cylinder during it can be adjusted by a control device.

Japanese Patent Publication No. 62-113844 discloses a control device for adjusting the amount of fuel supplied by a fuel pump to a combustion chamber of a diesel engine during an engine cycle. In the engine according to the invention of the above-mentioned patent publication, the start timing of fuel injection is controlled by a fixed cam on a camshaft, and the amount of injected fuel is controlled by opening a puncture valve provided on the supply side of the pump. It is controlled by changing the valve time according to the engine load. Although the fuel injection initiated by the camshaft was optimal at full load operation of the engine, the timing at partial load operation was delayed with respect to the engine cycle and only a limited amount of fuel was injected. Thus, in partial load operation, the engine cannot generate power to provide full load to various engine components. Therefore,
In the above patent publication, a computer is used as a control device for controlling the start time of fuel injection, and when a partial load is operated, an excessive amount of fuel is injected early in an engine cycle to increase engine power at the partial load. Like that. The computer receives information about the engine speed and signals from thermal sensors on the main bearings to prevent the bearings from being overloaded due to increased engine power at partial loads.

Normally, all main bearings for the engine are identical, so that spare parts do not need to be stocked for several different main bearings and the engine does not have to be fitted with the wrong type of main bearing. It is desirable to use a model.

It is an object of the present invention to increase engine power at both full and partial loads without exceeding the maximum allowable load of the main bearing.

In view of the above objects, it is a feature of the engine of the present invention that the control device causes the control unit to deliver a greater amount of fuel oil to the adjacent throw than the dose to the cylinder having the slowest angle to the adjacent throw. To a cylinder having a throw that forms a greater angle with respect to the cylinder.

The main bearing between the throws, which forms a small relative angle when viewed along the circumferential direction of the crankshaft, is due to the mass force from two adjacent throws projecting radially on the same side of the crankshaft and to two adjacent throws. A large load is applied by the compressive force from the two connecting rods mounted on the connecting rod pins of the throw. This is because the combustion process in two related cylinders in an engine having a certain number of cylinders is phase shifted by an angle corresponding to the angle between two adjacent throws. Therefore, the main bearing receives the compressive load from both cylinders at the same time. As mentioned above, it is desirable that all main bearings have the same structure, which means that
For the heaviest loaded bearings in known engines, this means setting an upper limit on the average pressure and thus on the power of all cylinders. By dispensing large amounts of fuel oil to cylinders having throws that form a large angle to adjacent throws, the excess load capacity of the main bearing between these throws is used to provide more power to the engine. This excess power is obtained at all engine loads. Thus, in the engine according to the invention, the main bearing is more evenly loaded than in known engines.

In a preferred embodiment in which the engine has eight cylinders, the controller will dispense the largest amount of fuel oil to the first, second, seventh and eighth cylinders. In an eight cylinder engine, the angle between the throws for the third and fourth cylinders is 45 ° and the angle between the throws for the fifth and sixth cylinders is the same, but the other The relative angle between the throws for the cylinders is 135 ° or 225 °. The aforementioned angle corresponds to the phase difference between the start of the compression stroke of the relevant cylinder. Since the above-mentioned angle difference is large, the first,
The second, seventh and eighth cylinders are a main bearing between the first and second cylinders, a main bearing between the second and third cylinders, Increasing the amount of power without overloading the main bearing between the sixth and seventh cylinders and the main bearing between the seventh and eighth cylinders Can be.

In another preferred embodiment in which the engine has twelve cylinders, the controller dispenses a minimal amount of fuel oil to the ninth and tenth cylinders. For a 12 cylinder engine, the angle between adjacent throws and the phase difference between the start of the compression stroke of adjacent cylinders is 120 °, 210 ° or 300 °.
゜, with one exception: the angle between the ninth and tenth cylinders is 30 °. Since the angle between the ninth and tenth cylinders is significantly smaller than the angle between the other engine cylinders, for a 12-cylinder engine, the performance of the engine can be reduced without overloading the bearings. Can be increased significantly.

Preferably, the control device doses the fuel oil such that the main bearings between throws are loaded substantially uniformly and provides maximum engine performance with respect to the load capacity of the main bearings when all bearings are of the same construction. I do. "Main bearing between throws" means not including the main bearings at both ends of the crankshaft (the main bearings at these ends receive loads from only one cylinder). If two main bearings are located between the two throws because the shaft is made up of two separate shaft segments, it is considered that these two bearings are substantially loaded by only one cylinder.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a perspective view showing the principle of a crankshaft of an eight-cylinder engine, and FIGS. 2 and 3 are ignition sequences and throws of an eight-cylinder engine and a twelve-cylinder engine (with a connecting rod pin or a crank arm having a crank arm). (Refer to reference numerals 2 and 3 in Fig. 1, for example.)
It is a figure which shows the angle difference between each.

The invention is particularly useful for large two-stroke crosshead engines used as engines for propelling ships or as stationary power generating engines. The reason for this is that such engines generate very high power per cylinder at low speeds, which places a large load on the main bearings. In order to reduce the length of the engine, it is desirable not to make the length of the main bearing very large, but this will limit the area of the main bearing.

The firing sequence of the cylinders is determined based on the torsional vibration conditions and the free mass force moments in the first and second firing sequences caused by the installation of the engine or the free mass moment by the hull of the ship during engine operation. The relative angle between throws for two consecutively ignited cylinders is 360 ° divided by the number of cylinders in a two-stroke engine, or 720 ° divided by the number of cylinders in a four-stroke engine. Should. For example, in a two-stroke eight-cylinder engine, the relative angle is 45 °, and in a two-stroke, twelve-cylinder engine, the relative angle is 30 °.

FIG. 1 shows a crankshaft 1 of an eight-cylinder two-stroke engine. The main bearing journal of the shaft is the main bearing MB
Is supported in ₁ -MB _9, bearing MB _1, MB ₉ is located at both ends of the shaft, the bearing MB _5a, MB _5b is located in the middle of the shaft on either side of the joint portion of the crank shaft consists of two segments . When the fuel pump and the valve of the engine are controlled by a camshaft, a chain wheel that drives the camshaft via a chain driver can be mounted on a jar joint. Each cylinder C ₁ -C ₈
In contrast, the crankshaft 1 has a throw consisting of two crank arms 2 connected to the associated main bearing journal, and a connecting rod pin 3 carried on the crank arm, which is connected to a connecting rod (shown in the drawing). Zu) is installed. The connecting rod is connected to the piston in the associated cylinder via a crosshead and a piston rod.

A typical ignition sequence for an eight cylinder engine is shown in Table 1 below.

The first column of Table 1 shows the number of the relevant cylinder pair, and the second column shows the angle α between two adjacent throws belonging to the cylinder pair shown in the first column. Each angle α corresponds to a phase difference between the start of the combustion stroke of the associated cylinder pair. Therefore, whether or not the main bearing located between the pair of cylinders receives the compressive force simultaneously from the cylinders on both sides can be directly known from the indication of the angle. The third column of Table 1 shows the ignition order of the first cylinder of the cylinder pair shown in the first column.

The contents of Table 1 are shown graphically in FIG.
One engine cycle corresponding to 360 ° rotation of the crankshaft is indicated by a solid circle. Since the engine is eight cylinders, circles are formed at 45 ° angular intervals corresponding to the rotation of the shaft during the start of the combustion stroke for two consecutive pistons.
Divide into pieces. During each rotation interval, n cylinders C _n performing the combustion stroke are shown. The relative angle of two adjacent throws can be read directly from the drawing as the angle between the radii belonging to the two cylinders. It can be seen that the angle between cylinder 1 and cylinder 2 is α _1-2 = 225 °. The same applies to other cylinders. For example, between cylinders 5 and 6, the angle is α _5-6 = 45 °, indicating that cylinder 6 is ignited following cylinder 5. This means that the main bearing between these two cylinders receives a compressive force from both connecting rods simultaneously. The same situation occurs for cylinders 3 and 4. Therefore,
The control unit dispenses the maximum amount of fuel oil to cylinders 1 and 2, the minimum amount of fuel oil to cylinders 3-6, and the cylinders 7 and 8 provide between the maximum and minimum amount of fuel oil. Is supplied.

The situation for a 12 cylinder engine is shown in FIG. 3 and the conditions are shown in Table 2.

The control unit supplies the maximum amount of fuel oil to cylinders 6, 7, 12
To the cylinders 3 and 4, and a small amount of fuel oil to the cylinders 1 and 2.
It can be seen that dosing to 2, 4, 5, 7, 8, 11 and the minimum amount of fuel oil to dosing cylinders 9, 10.

If the engine is a conventional engine having a fuel pump controlled by a camshaft, the control device can be an index rod that adjusts the index of the pump according to the engine load. The pump can be connected to the control index rod so that it is permanently set to supply mutually different amounts of fuel oil at all engine loads.

If the engine is of the more modern type and is controlled by a computer, the control device may comprise a computer and a fuel pump operating unit which is, for example, electromechanically controlled and hydraulically operated. From the predetermined information about the relative ratio between the bearing loads, the computer can easily determine the individual oil dose to the cylinder so that the main bearing of the crankshaft is loaded as evenly as possible.

If a problem occurs with the main bearing (for example, when the bearing temperature rises due to the seizure between the bearing and its associated bearing journal), the computer will transfer less fuel oil to the cylinder adjacent to that bearing. It can be administered temporarily. This makes it possible to temporarily reduce the load on the selected bearing, which is particularly advantageous for the engine according to the invention. The reason is that when fully utilizing the capabilities provided by the present invention to increase engine power, all the main bearings of this engine are fully loaded. In known engines where only one or two main bearings are fully loaded, there is less need to temporarily reduce the load on the bearings.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-12864 (JP, A) JP-A-62-113844 (JP, A) JP-A-55-123332 (JP, A) JP-A-2- 55857 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 395

Claims (5)

(57) [Claims] 1. A large two-stroke crosshead engine for propelling an engine, in particular a ship, comprising a plurality of cylinders (Cn), each cylinder having an associated crankshaft (1) common to these cylinders. Having a piston connected to each of the throws (2, 3) such that adjacent throws have a predetermined relative angle (α), wherein the relative angle is different for at least some of the adjacent throws. The throw is connected via a main bearing journal supported on a main bearing (MBn), so that the amount of fuel oil injected into the cylinder during an engine cycle can be adjusted by a control device. In the engine, the control device has the throw that forms the minimum relative angle with respect to one of the two adjacent throws. A greater amount of fuel oil is dispensed to the cylinder (Cn) with the throw forming a greater relative angle (α) to both adjacent throws than the oil dose to the cylinder. An engine characterized by: 2. The engine according to claim 1, wherein said first, second, third, fourth, fifth, sixth, seventh and eighth parts are arranged from one end to the other end of the engine. In an engine having eight cylinders arranged in a serial number as described above, wherein the control device administers a maximum amount of fuel oil to the first, second, seventh and eighth cylinders. Features engine. 3. The engine according to claim 1, wherein the first, second, third, fourth, fifth, sixth, seventh, eighth, eighth, and seventh, from one end to the other end of the engine. 9th, 10th, 1st
1, an engine having 12 cylinders arranged in a serial number as in the twelfth aspect, wherein the control device administers a minimum amount of fuel oil to the ninth and tenth cylinders. And engine. 4. The engine according to claim 1, wherein the control device controls the main bearing (MBn) between the throws (2, 3) to load the load substantially uniformly. An engine characterized by dispensing an amount of fuel oil to receive. 5. In the engine according to any one of claims 1 to 4, when a problem of a temperature rise of a bearing occurs in any of the main bearings (MBn), the control device is provided with the control device. An engine for temporarily dispensing a smaller amount of fuel oil to the cylinder (Cn) adjacent to the main bearing.