JP2013036449A - Auxiliary brake device of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auxiliary brake device of a diesel engine capable of easily increasing a braking force.SOLUTION: This compression-open brake includes a multilink 11 to which a crank pin 12 and a connecting rod 10 are turnably connected, and a rocking joint 13 whose one end is turnably connected to the multilink 11 and whose other end is turnably fixed to a vertically movable rocking joint supporting point 14. The stroke length of a piston 2 is increased by moving the rocking joint supporting point 14 interlockingly with the operation of a valve operating means 8.

Description

  The present invention relates to an auxiliary brake device for a diesel engine, and more particularly to an auxiliary brake device for a diesel engine that can easily enhance the braking force.

  In general, large vehicles such as trucks and buses equipped with diesel engines are equipped with an auxiliary brake in addition to a normal friction brake in order to obtain a sufficient braking force. Examples of the auxiliary brake include a compression release brake, an exhaust brake, and a retarder.

  On the other hand, with the recent increase in traffic safety awareness and the increase in size and speed of vehicles, it is required to enhance the braking force of large vehicles (see, for example, Patent Document 1). This is also true for the compression release brake, which is one of the auxiliary brakes.

  The compression release brake opens the exhaust valve near the top dead center during the compression stroke to discharge the air in the cylinder, and closes the exhaust valve after passing through the top dead center to perform the expansion stroke with a small amount of air in the cylinder. In this way, absorption torque is generated and braking force is obtained. In such a compression release brake, in order to increase the braking force by generating a larger absorption torque, the pressure at the compression end is increased by improving the supercharging pressure and the compression ratio, etc., and negative work during the expansion stroke is performed. Need to increase.

  However, in order to improve the supercharging pressure, it is necessary to increase the work of the turbo. However, when fuel is not injected during braking, sufficient exhaust energy cannot be ensured. Therefore, it is difficult to improve the supercharging pressure during braking.

  The compression ratio can be improved by changing the piston, but it is difficult to change it during operation. Further, the optimum compression ratio is selected for various conditions, and it is not realistic to select a high compression ratio only during braking.

  Under the circumstances as described above, there is a demand for a measure that can easily enhance the braking force of the compression release brake.

JP-A-9-324658

  An object of the present invention is to provide an auxiliary brake device for a diesel engine that can easily enhance the braking force.

  An auxiliary brake device for a diesel engine according to the present invention that achieves the above object includes a cylinder having a piston connected to a crank pin of a diesel engine via a connecting rod, and an exhaust that opens and closes an exhaust port that opens in a combustion chamber of the cylinder. And a valve operating means for opening the exhaust valve when the piston reaches near the top dead center of the compression stroke and closing the exhaust valve when the piston is in the expansion stroke after passing through the top dead center. In an auxiliary brake device for a diesel engine, a multilink in which the crank pin and the connecting rod are rotatably connected, one end of the multilink is rotatably connected, and the other end is movable up and down A swinging node pivotally fixed to the swinging node fulcrum, and moving the swinging node fulcrum in conjunction with the operation of the valve operating means to move the piston stroke. It is characterized in that to increase.

  In the above-described diesel engine auxiliary brake device, the multi-link is constituted by a three-bar link, and the crankpin, the connecting rod, and the swinging node are connected to the respective tops of the three-bar link.

  According to the auxiliary brake device for a diesel engine of the present invention, a conventional diesel engine is provided with a multi-link, a swing node and a swing node fulcrum, and the swing node fulcrum is moved in conjunction with the operation of the auxiliary brake. By increasing the stroke length of the piston and increasing the compression end pressure as the compression ratio increases, the negative work during the expansion stroke can be increased, so the braking force can be easily strengthened. it can.

It is a block diagram in case the piston is located at the bottom dead center in the auxiliary brake device for a diesel engine according to the embodiment of the present invention. In the auxiliary brake device of the diesel engine of FIG. 1, it is a block diagram in case a piston is located in a top dead center. It is a block diagram explaining operation | movement of the auxiliary brake device of a diesel engine. It is a graph showing the relationship between the crank angle when changing the stroke length of a piston, and the volume in a cylinder. It is a graph showing the relationship between the volume in a cylinder when the stroke length of a piston is changed, and the pressure in a cylinder.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an auxiliary brake device for a diesel engine according to an embodiment of the present invention.

  The auxiliary brake device of the diesel engine (hereinafter referred to as “auxiliary brake device”) is a compression release brake, and FIG. 1 shows a case where the piston 2 reciprocating up and down in the cylinder 1 is located at the bottom dead center. Yes.

  An intake valve 6 and an exhaust valve 7 that open and close the intake port 4 and the exhaust port 5 that open to the combustion chamber 3 in the cylinder 1 are attached to the upper part of the cylinder 1 of the diesel engine. When the compression release brake is used, the valve operating means 8 is activated, the exhaust valve 6 is opened when the piston 2 reaches near the top dead center of the compression stroke, and the exhaust valve 6 is exhausted when it is in the expansion stroke after passing through the top dead center. The valve 6 is closed.

  The piston 2 in the cylinder 1 is connected to the multilink through a connecting rod 10 that is connected to the piston pin 9. The multi-link is composed of a three-joint link 11 made of a substantially triangular metal plate, and an end of the connecting rod 10 is rotatably connected to one of the tops of the three-joint link 11.

  The remaining two tops of the three-bar link 11 are connected to a crank pin 12 and one end of a swinging node 13 made of a rod-like body so as to be freely rotatable. The other end of the swinging node 13 is fixed to a swinging node fulcrum 14 that can move continuously in the vertical and horizontal directions.

  In this way, since the connecting rod 10, the crankpin 12 and the swinging node 13 are pivotally connected to the three-bar link 11, as shown in FIG. 2, even when the piston 2 is located at the top dead center, Respectively, the three-way link 11 is interposed to change the position to an appropriate position, so that the reciprocation of the piston 2 is not hindered.

  In order to enhance the braking force of a vehicle equipped with a diesel engine using the above auxiliary brake device, the swinging fulcrum 14 is moved in an appropriate direction in conjunction with the operation of the valve operating means 8, Hold in that position.

  In the example shown in FIG. 3, when the swinging node fulcrum 14 is moved upward, the three-bar link 11 rotates around the crank journal 15 which is the center of the crankshaft (clockwise in FIG. 3). When the member is displaced from the position indicated by the solid line to the position indicated by the alternate long and short dash line, the position of the piston 2 at the bottom dead center is shifted downward, so that the stroke length of the piston 2 increases. In FIG. 3, the increment of the stroke length of the piston 2 is indicated by W.

  In the example of FIG. 3, the swinging fulcrum 14 is moved upward. However, the swinging fulcrum 14 is moved in the left-right direction and the circumferential direction depending on the dimensions of each part, and the stroke of the piston 2. Sometimes the length is increased.

  4 and 5 show changes in the volume in the cylinder 1 and the pressure in the cylinder 1 when the stroke length of the piston 2 is changed.

  From FIG. 4, it can be seen that as the stroke length of the piston 2 increases, the volume in the cylinder 1 increases during the expansion stroke. Further, FIG. 5 shows that as the stroke length of the piston 2 becomes longer, the compression end pressure increases with an increase in the compression ratio, and the negative work amount during the expansion stroke increases.

  Thus, it turns out that braking force can be strengthened by lengthening the stroke length of piston 2 using the auxiliary brake device of the present invention. Further, since the conventional diesel engine is provided with the multi-link, the swing node 13 and the swing node fulcrum 14 and only needs to move the swing node fulcrum 14, the present invention can be easily implemented.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Combustion chamber 4 Intake port 5 Exhaust port 6 Intake valve 7 Exhaust valve 8 Valve operating means 9 Piston pin 10 Connecting rod 11 Three-bar link 12 Crank pin 13 Oscillating node 14 Oscillating node fulcrum 15 Crank journal

Claims (2)

A cylinder having a piston connected to a crank pin of a diesel engine via a connecting rod, an exhaust valve that opens and closes an exhaust port that opens to the combustion chamber of the cylinder, and when the piston reaches near the top dead center of a compression stroke In an auxiliary brake device for a diesel engine comprising: a valve operating means for opening the exhaust valve and closing the exhaust valve when the exhaust valve is in an expansion stroke after passing through top dead center;
A multi-link in which the crank pin and the connecting rod are rotatably connected, and a swinging fulcrum whose one end is pivotally connected to the multi-link and the other end is vertically movable. And a swinging node fixed to
An auxiliary brake device for a diesel engine, wherein the stroke length of the piston is increased by moving the swinging fulcrum in conjunction with the operation of the valve operating means. The auxiliary brake device for a diesel engine according to claim 1, wherein the multi-link is a three-bar link, and the crank pin, the connecting rod, and the swinging node are connected to respective top portions of the three-bar link.

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