JPH0521139U - Rotational braking system for 2-cycle large diesel engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To achieve a significantly large braking effect by adding a simple hydraulic device in a diesel engine having a hydraulically driven exhaust valve. The two-cycle large-scale diesel engine rotary braking device of the present invention uses a conventional starting air control injection device to perform engine braking, and further, a crank angle detecting device 10
The actuator 4 of the exhaust valve is controlled via the valve to open the exhaust valve 3 during the expansion stroke of the engine so that the positive expansion work becomes almost zero, so that a remarkable braking effect can be obtained. ..

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotary braking device for a two-cycle large diesel engine.

[0002]

[Prior Art]

 The conventional engine rotary braking device shown in FIG. 1 utilizes starting air control injection devices 13, 14, 15 which are known systems, and by introducing compressed air into the cylinder during the compression stroke of the engine, negative air is injected. The rotation control is measured by increasing the compression work from the positive air expansion work. That is, in the compression stroke in which the piston 2 rises and compresses the air in the cylinder, the starting air control valve 14 is controlled, and the starting air accumulated in the starting air tank 13 is introduced into the cylinder 1 from the starting valve 15. The negative compression work is increased to rotationally brake the engine.

However, after the air pressure in the cylinder exceeds the pressure in the starting air tank 13, the air in the cylinder starts to flow back into the starting air tank 13. Further, since the starting valve 15 is closed shortly after passing through the top dead center, the communication between the air in the cylinder and the starting air tank 13 is cut off, and a simple air expansion stroke is performed. Therefore, the amount of air in the cylinder in the air expansion stroke is less than the amount of air in the compression stroke, and the positive expansion work is smaller than the negative compression work. The difference between the positive expansion work and the negative compression work applies rotational braking to the engine.

[0004]

[Problems to be solved by the device]

 However, in the conventional technology, since a considerable amount of air still remains in the cylinder during expansion, (the only discharge of air is the backflow from the start valve after the compressed air pressure becomes higher than the starting air tank. Moreover, the period is a short time up to the top dead center.) The positive expansion work is inevitable according to the residual air amount, and there is a drawback that a sufficiently large rotational braking effect cannot be obtained.

The object of the present invention is to solve the above problems of the conventional device, and in a diesel engine having a hydraulically driven exhaust valve, by adding a simple hydraulic device, a two-cycle large-scale diesel engine having a significantly large braking effect can be obtained. To provide a rotary braking device for an engine.

[0006]

[Means for Solving the Problems]

 A rotary braking device for a two-cycle large diesel engine of the present invention is a two-cycle large diesel engine having a hydraulically driven exhaust valve, in which a hydraulic system capable of opening the exhaust valve at any timing and a crank system for the hydraulic system. It is characterized by having a control means for interlocking with the angle and improving the braking effect on the mechanism.

[0007]

[Action]

 When the engine is braking, high-pressure air is injected into the cylinder from the starting air tank during the compression stroke as before, and in the present invention, the exhaust valve is opened during the expansion stroke so that the cylinder communicates with the outside air. Since it becomes zero, the positive expansion work is not canceled by the negative compression work, and it becomes possible to obtain a large rotational braking as compared with the conventional case.

An embodiment of the present invention will be described below with reference to FIG. In the exhaust valve driving oil tank 9, a sufficient hydraulic pressure for driving the exhaust valve 3 is accumulated via the oil pump 11. The exhaust valve driving oil tank 9 communicates with the actuator 4 of the exhaust valve 3 via a control valve 8 controlled by a crank angle detecting device. The engine body shown in FIG. 1 has a well-known hydraulically driven exhaust valve 3, and the hydraulic pressure generator 5 driven by the engine is driven through the high pressure driven oil pipes 6 to 7 so as to maintain a constant level during normal operation. It communicates with the exhaust valve actuator 4, which opens and closes at the timing. The braking device of the present invention has a conventional braking device utilizing the known starting air control injection devices 13, 14, and 15.

Next, the operation of the above embodiment will be described. When the engine is rotationally braked, the control valve 8 is opened during the expansion stroke in accordance with a control signal from the crankshaft rotation angle detection device 10 to exhaust the exhaust valve actuator 4 independently of the exhaust valve opening / closing timing during the normal operation described above. The hydraulic pressure of the valve-driving oil tank 9 is introduced to open the exhaust valve 3 so that the positive work during the expansion stroke is almost zero, so that the rotary braking effect on the engine can be remarkably increased as compared with the conventional case. In this embodiment, the crank angle detecting device 10, the oil tank 9, and the control valve 8 are newly provided so as to detect the timing of the expansion stroke. However, the exhaust valve drive for controlling the exhaust valve 3 is required. The same effect can be obtained by partially modifying the crank angle detecting device in the hydraulic pressure generator 5 so that the exhaust valve opens during the expansion stroke of the engine during engine braking.

[0010]

[Effect of the device]

 Since the two-cycle large-scale diesel engine rotary braking device of the present invention is configured as described above, the quick braking property of the diesel ship is improved, and the safety in navigation of the ship is improved. Further, in the diesel power generation, it is possible to quickly pass through the torsional vibration resonance rotation speed range when the rotation speed is lowered, and it is possible to improve the strength reliability of the engine.

[Brief description of drawings]

FIG. 1 is a diagram of a rotary braking device for a two-cycle large diesel engine according to a first embodiment of the present invention.

[Explanation of symbols]

1 ... Cylinder, 2 ... Piston, 3 ... Exhaust valve, 4 ... Actuator, 5 ... Exhaust valve driving hydraulic pressure generating device, 8 ... Control valve,
9 ... Exhaust valve drive oil tank, 10 ... Crank angle detection device.

Claims (1)

[Scope of utility model registration request] 1. A two-cycle large-scale diesel engine having a hydraulically driven exhaust valve, a hydraulic system capable of opening the exhaust valve at an arbitrary timing, and a braking effect on the engine by controlling the hydraulic system in conjunction with a crank angle. A rotary braking device for a two-cycle large diesel engine, which has a control means for improving