JPS6030449Y2 - Boost pressure control device for diesel engine with supercharger - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a boost pressure control device for taking measures against emissions in a supercharged diesel engine.

BACKGROUND ART Conventionally, a diesel engine with a supercharger is well known, which is equipped with a supercharger that supercharges intake air, and is capable of improving fuel efficiency, output performance, etc. by increasing the filling efficiency of the intake air.

In such turbocharged diesel engines, the supercharger is normally operated at all times while the engine is running, and uniformly provides intake supercharging regardless of changes in engine load or rotational speed. Therefore, the combustion pressure tends to increase in the low-load operating range of the engine.

By the way, in order to improve the emission performance of such a diesel engine with a supercharger, when the engine is operated at a low load below a predetermined level, the fuel in the fuel chamber of the fuel injection pump is released through the relief passage, and the fuel in the fuel chamber is If an injection timing control device is installed that lowers the pressure and retards the fuel injection timing, it is regrettable that the emission performance improvement function of the injection timing control device will not be fully demonstrated due to the increase in combustion pressure during low-load operation of the engine. was there.

Therefore, in order to reduce the supercharging pressure of the intake air by the supercharger during low-load operation of the engine, a load sensor is provided to detect the engine load, and the supercharging pressure control mechanism is activated based on the load sensor detection signal. It is conceivable to reduce the supercharging pressure by

However, in this case, an expensive load sensor is required, resulting in high costs, and problems arise in that the number of parts increases and the control mechanism becomes complex.

Furthermore, a method has been proposed in which a throttle valve is provided in the intake passage and the throttle valve is controlled according to the load (Utility Model Application Publication No. 77214/1989), but such a structure would result in a complicated configuration. In addition, it becomes necessary to skillfully adjust the timing of delaying the fuel injection timing and the timing of opening and closing the throttle valve.

The present invention has been made in view of these points, and by driving the boost pressure control mechanism using the fuel pressure generated in the relief passage of the injection timing control device of the fuel injection pump described above, Provided is a supercharging pressure control device for a diesel engine with a supercharger that is capable of reducing intake supercharging pressure during low load operation of the engine at low cost and with a simple structure without using an expensive load sensor. It is something that is recommended.

That is, the present invention controls the fuel injection timing according to the pressure in the fuel chamber of the fuel injection pump, and also releases the fuel in the fuel chamber through the relief passage when the engine is under a predetermined light load. In a supercharged diesel engine having an injection timing control device that reduces pressure and delays fuel injection timing, there is provided a supercharging pressure control mechanism that controls the supercharging pressure of intake air, and an IJ-F passage of the fuel injection pump. The present invention is characterized in that it is connected to a pressure-responsive member that operates based on pressure changes, and is configured to reduce the supercharging pressure of intake air when the pressure in the relief passage is higher than a predetermined value.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In Figure 1, 1 is a diesel engine (not shown)
2 is an exhaust passage, and a blower 3 is disposed in the intake passage 1, and a turbine 5 integrally connected to the blower 3 via a shaft 4 is disposed in the exhaust passage 2. A turbo supercharger 6 is constructed in which a turbine 5 is rotated by the exhaust gas flow of the engine, and the blower 3 is rotated by the rotation of the turbine 5 to supercharge intake air.

Further, the exhaust passage 2 is provided with a bypass passage 7 for the turbine 5 of the supercharger 6, and a control valve 8 for controlling the opening and closing of the bypass passage 7 is disposed in the middle of the bypass passage 7.
A two-stage pressure response device 11 is connected to the valve shaft 8a of the control valve 8 via a rotary lever 9 and a rod 10.

The pressure-responsive device 11 includes, within the housing 12, first and second pressure-responsive members 13.1 each consisting of a diaphragm.
4, an atmospheric pressure chamber 15, an intake pressure chamber 16, and a fuel pressure chamber 17, and a spring 15a provided in the atmospheric pressure chamber 15, the atmospheric pressure chamber 15 being open to the atmosphere, Further, the central intake pressure chamber 16 is communicated with the intake passage 1 downstream of the blower 3 of the supercharger 6 via a communication passage 18.

Further, the rod 10 is connected to the first pressure responsive member 13 (the one on the left side in the figure) that defines the atmospheric pressure chamber 15 and the intake pressure chamber 16, so that the supercharging pressure of the intake air is below a predetermined value. , the first pressure responsive member 13 is biased to the left in the figure against the biasing force of the spring 15a, the control valve 8 is opened, the bypass passage 7 is opened, and the exhaust gas flow is directed to the supercharger 6. The turbine 5 is bypassed and flowed down to weaken the rotational force of the blower 3. On the other hand, if the supercharging pressure of the intake air is lower than a predetermined value, the first pressure responsive member 13 is biased to the right in the figure to control the flow. By closing the valve 8 to close the bypass passage 7 and letting the exhaust gas flow to the turbine 5 to increase the rotational force of the blower 3, the supercharging pressure of the intake air by the supercharger 6 can be adjusted according to the operating state of the engine. Boost pressure control mechanism 19 that controls
is configured.

On the other hand, 20 is a fuel injection pump that injects fuel to the engine, and as is well known, the fuel injection pump 20 controls the fuel injection timing according to the engine rotational speed, and controls the fuel injection timing when the engine is running at a predetermined level or less. An injection timing control device 21 is provided that delays the fuel injection timing during load.

That is, the injection timing control device 21 includes a feed pump 22 driven by the engine;
A timer piston (not shown) is moved by the pressure in the fuel chamber 24 generated by the regulating valve 23 that corrects the generated pressure, and the movement of the timer piston causes the reciprocation of the fuel pumping plunger (not shown). The governor sleeve of the governor mechanism 25 controls the fuel injection timing according to the engine speed by changing the movement timing, and also corrects the fuel injection amount according to the engine speed when the engine is under a light load below a predetermined level. 25a, and a relief passage 27 that is formed from the inside of the governor shaft 25b of the governor mechanism 25 to the wall of the housing 20a of the fuel injection pump 20, and whose downstream end opens to the suction side of the feed pump 22. The upstream end opening of the fuel chamber 24 is communicated with the upstream end opening of the
By releasing the fuel through the fuel chamber 24 and lowering the pressure inside the fuel chamber 24, the fuel injection timing is delayed.

Note that 28 is a throttle provided near the downstream end of the relief passage 27 to increase the pressure within the relief passage 27.

Further, I on the upstream side of the throttle 28 of the fuel injection pump 20
The JIJ-fu passage 27 and the fuel pressure chamber 17 of the pressure response device 11 are communicated via a communication passage 29, and due to pressure changes in the relief passage 27, the fuel pressure chamber 17 of the pressure response device 11 and the intake pressure are communicated with each other. a second pressure-responsive member 1 defining a chamber 16;
4 (the one on the right in the figure) is biased.

Further, a pressing member 30 is attached to the surface of the second pressure-responsive member 14 on the side of the intake pressure chamber 16, and
When the fuel pressure in the J-fu passage 27 is above a predetermined level, that is, when the engine is under a light load below a predetermined level, the pressure increase in the fuel pressure 17 biases the second pressure-responsive member 14, and this operation causes the pressing member to Supercharging control mechanism 1 via 30
The control valve 8 is opened by pressing the first pressure responsive member 13 of 9 to the left in the drawing, thereby reducing the supercharging pressure of intake air.

Note that 31 is a stopper member that is attached to the surface of the second pressure responsive member 14 on the fuel pressure chamber 17 side and restricts the amount of deviation of the second pressure responsive member 14 on the right side in the drawing.

Next, to explain the operation of the above embodiment, when the engine is in a light load operating region below a predetermined level, the relief passage 27 of the fuel injection timing control device 21 of the fuel injection pump 20 is connected to the governor mechanism 25. 25a first
As it moves to the left in the figure, it communicates with the fuel chamber 24, and the fuel in the fuel chamber 24 flows out through the IJ-F passage 27, reducing the pressure in the fuel chamber 24, thereby reducing the fuel injection timing. is corrected to the lag side as shown in the left half of FIG. 2, and the emission performance is improved by lowering the combustion temperature of the engine.

At that time, the fuel pressure in the relief passage 27 is reduced to the communication passage 2.
9 into the fuel pressure chamber 17 of the pressure response device 11,
When the pressure exceeds a predetermined value, the second
The pressure responsive member 14 biases and biases the first pressure responsive device 13 of the boost pressure control mechanism 19 to the left in the figure via the pressing member 30, thereby opening the control valve 8 and opening the bypass passage. 7 is opened, and the supercharging pressure of the intake air is reduced as shown in the left half of FIG.

As a result, an increase in the combustion pressure of the engine is suppressed, so that the emission performance improvement function of the injection timing control device 21 is fully exhibited.

On the other hand, when the engine shifts to a medium-high load operating region, the fuel chamber 24 of the fuel injection pump 20 and the IJ-F passage 27 of the injection timing control device 21 are communicated with each other. The movement to the right in Figure 1 blocks the flow, and prevents the fuel pressure in the fuel chamber 24 from decreasing, so the fuel injection timing advances normally as shown in the right-hand side of Figure 2, and the output performance of the engine is improved. is ensured.

Further, since fuel does not flow through the relief passage 27 and the pressure within the relief passage 27 decreases, the pressure response device 1
The pressure within the fuel chamber 17 of No. 1 also decreases, and the pressure response device 11
The pressure within the fuel pressure chamber 17 also decreases, and the second pressure responsive member 14 of the pressure responsive device 11 returns to its inoperative position.

As a result, the supercharging pressure control mechanism 19 operates normally to control the supercharging pressure of the intake air, thereby improving the output performance of the engine.

Therefore, since the pressure in the relief passage 27 of the fuel injection pump 20 is used to drive the boost pressure control mechanism 19, the intake boost pressure can be reduced in the low load operating region of the engine with a simple structure. It can be done easily and inexpensively.

In the above embodiment, as shown in FIG. 3, supercharging is not performed when the pressure in the relief passage 27 is above a predetermined value, but by controlling the amount of exhaust gas passing through the bypass passage 7, , a configuration may be adopted in which the supercharging pressure is reduced.

Further, in the above embodiment, a diesel engine is described which is equipped with a turbo supercharger 6 that drives a blower 3 using the exhaust gas flow of the engine to perform intake supercharging. Of course, the present invention can also be applied to a diesel engine equipped with a supercharger that drives the supercharger to perform intake supercharging.

As explained above, according to the present invention, the fuel injection timing device of the fuel injection pump includes a pressure-responsive member that operates based on the pressure in the IJ-F passage, and a supercharger that controls the supercharging pressure of intake air by the supercharger. The system is connected to a boost pressure control mechanism to reduce intake boost pressure when the pressure in the relief passage is above a predetermined level, thereby suppressing intake boost pressure during low-load operation of the engine. This can be done with a simple structure and at low cost, and is therefore practical in terms of emission countermeasures for supercharged diesel engines.

[Brief explanation of drawings]

The drawings illustrate an embodiment of the present invention, in which FIG. 1 is an overall vertical sectional view, FIG. 2 is an operational characteristic diagram of an injection timing control device, and FIG. 3 is an operational characteristic diagram of the present invention device. 1...Intake passage, 2...Exhaust passage, 6
...Turbocharger, 7...Bypass passage, 8...Control valve, 11...Pressure response device, 14......No. 2 pressure responsive member, 15.
...Atmospheric pressure chamber, 16...Intake pressure chamber, 17
...Fuel pressure chamber, 19...Supercharging pressure control mechanism, 20...Fuel injection pump, 21...
・Injection timing control device, 24...Fuel chamber, 27.
...IJ IJ-F passage, 29...Communication passage.

Claims (1)

[Scope of utility model registration request] The fuel injection timing is controlled according to the pressure in the fuel chamber of the fuel injection pump, and when the engine is under a light load below a specified level,
In a supercharged diesel engine having an injection timing control device that releases fuel in the fuel chamber through a relief passage to reduce the pressure in the fuel chamber and retard the fuel injection timing, in an intake supercharged diesel engine, A boost pressure control mechanism that controls the boost pressure of intake air is connected to a pressure responsive member that is activated by pressure changes in the relief passage of the fuel injection pump, and when the pressure in the relief passage is above a predetermined level, the intake air A boost pressure control device for a diesel engine with a supercharger, characterized in that it is configured to reduce boost pressure.