JPS6115255B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an exhaust recirculation control device that controls the amount of recirculation of exhaust gas in response to the load of a diesel engine and reduces NOx in the exhaust gas. be.

[Conventional technology]

As an exhaust recirculation control device for diesel engines,
For example, Utility Model Application Publication No. 49-11113 and Japanese Patent Application Publication No. 53-
As disclosed in Publication No. 141825, etc., a throttle valve is provided in the intake pipe of the engine, the exhaust pipe and intake pipe of the engine are connected by a reflux pipe, and the intake pipe opening of the reflux pipe is connected to the downstream side of the throttle valve. The exhaust gas recirculation amount is controlled by adjusting the opening and closing states of the throttle valve using an electromagnetic actuator. However, electromagnetic actuators have the disadvantage that the structure of the actuator itself is complicated. It is also possible to control the throttle valve with a pneumatic actuator, but a pneumatic actuator uses air pressure (positive pressure or negative pressure).
A separate source is required, making the configuration complicated.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide an exhaust gas recirculation control device for a diesel engine that has a simple configuration and can control the amount of exhaust gas recirculation with high precision depending on the engine load.

[Means for solving problems]

In order to achieve the above object, the present invention has a configuration including a reflux pipe that connects an exhaust pipe and an intake pipe of an engine, an intake valve provided in a portion of the intake pipe upstream of a connection part with the reflux pipe, and a hydraulic actuator for adjusting the opening degree of the intake valve; a means for connecting the hydraulic actuator and a discharge port side of a feed pump of a fuel injection device to guide fuel discharged from the feed pump to the hydraulic actuator; a solenoid valve for regulating fuel pressure;
and an electric control device for opening and closing the electromagnetic valve, and the electric control device receives electric signals corresponding to the rotation speed and fuel injection amount of the fuel injection device, respectively, and controls the exhaust gas return according to the load of the engine. It controls the flow rate.

[Effect]

The electromagnetic valves 8 and 9 are opened and closed in response to increases and decreases in the engine load, thereby operating the hydraulic actuator 24 and controlling the opening degree of the intake valve 20. Corresponding to this change in the opening degree of the intake valve 20, the pressure at the connection part of the intake pipe 18 with the outlet 22a of the recirculation pipe 22 changes, and the amount of exhaust gas recirculated from the exhaust pipe 23 via the recirculation pipe 22 is adjusted. be done. The amount of exhaust gas recirculation is optimally controlled by an electric control device 10 that opens and closes the solenoid valves 8 and 9.

[Embodiments of the invention]

The present invention will be explained based on examples. As shown in FIG. 2, an intake valve 20 is connected to the intake pipe 18 of the engine 21.
A reflux pipe 22 is branched from the exhaust pipe 23 and connected to the intake pipe 18 adjacent to the intake valve 20 and downstream. In order to adjust the opening degree of the intake valve 20, a lever 17 fixed to a support shaft of the intake valve 20 is connected to a hydraulic actuator 24. The hydraulic actuator 24 has a piston 15 fitted into the cylinder 12 to partition the chambers 14 and 16, and a spring 11 housed in the chamber 16.
The piston 15 is configured to be biased to the left.

Fuel pressure is applied to the chamber 14 from the fuel reservoir configured inside the fuel injection device 26 via passages 28 and 29, while pressure is reduced from the fuel reservoir to the chamber 16 via passages 28 and 30, the throttle 40, and the passage 31. fuel pressure is applied. Connect passage 28 to fuel tank 1
A solenoid valve 8 is inserted and connected in the middle of a passage 33 that connects the passage 31 to the fuel tank 13, and a solenoid valve 9 is inserted and connected in the middle of a passage 32 that connects the passage 31 to the fuel tank 13.

The fuel injection device 26 is connected to the fuel tank 1 as is known in the art.
A feed pump 2 is provided for supplying fuel from 3 to the fuel reservoir chamber, and a discharge port of the feed pump 2 is connected to the fuel reservoir chamber. The end of the fuel injector 26 is provided with a hydraulic head 5 having a distribution barrel and a plunger fitted inside the distribution barrel. The plunger is connected to the pump shaft by an Oldham joint housed inside the fuel reservoir chamber and a cam mechanism, so that the plunger reciprocates while rotating.

The fuel pressurized by the plunger passes through a discharge valve 4 disposed along the circumferential direction at the end of the hydraulic head 5, and is sequentially pumped to each cylinder of the engine. In order to control the fuel injection amount, a fuel control sleeve 3 fitted onto the plunger is displaced in the axial direction of the plunger in relation to the operation amount of the acceleration lever and the speed governor,
The pumping stroke of the plunger is adjusted. Furthermore, an injection timing adjustment device 7 is incorporated which changes the synchronous rotational phase of the camshaft 1 and the plunger driven by the engine by rotationally displacing the cam mechanism.

An electric control device 10 is provided to control the pair of electromagnetic valves 8 and 9, to which electric signals corresponding to the engine speed, fuel injection amount, and intake air amount are applied. A known rotation speed detector 25 is provided opposite the feed pump 2 to detect the engine rotation speed. In order to detect the fuel injection amount, an injection amount detector 6 is provided which detects displacement of the fuel control sleeve 3 as, for example, a change in coil inductance. Furthermore, an air amount detector 19 for detecting the amount of air taken into the engine 21 is provided at the entrance of the intake pipe 18.

Next, the operation of the exhaust gas recirculation control device for a diesel engine according to the present invention will be explained. The engine load is detected in the electric control device 10 based on signals from the rotation speed detector 25 and the injection amount detector 6, and the electromagnetic valves 8 and 9 are opened and closed, respectively, according to the engine load.
On the other hand, the pressure in the fuel reservoir chamber of the fuel injection device 26 increases approximately in proportion to the engine speed, and this pressure increases in the passage 2.
The piston 15 is applied to the chambers 14 and 16 of the hydraulic actuator 24 through the passages 8 and 29 and the passages 30 and 31, and the piston 15 is stopped at a position where the pressure difference between the two chambers and the force of the spring 11 are balanced.

Now, when the load on the engine increases, only the solenoid valve 9 is opened by the output of the electric control device 10. Room 1
6 is released to the fuel tank 13 through the passage 31, the solenoid valve 9 and the passage 32, and the piston 15 moves to the right against the force of the spring 11. Therefore, the intake valve 20 is rotated clockwise via the lever 17, and the opening degree becomes smaller. The static pressure of the intake pipe 18 at the outlet 22a of the reflux pipe 22 decreases, and the amount of recirculation of the exhaust gas flowing into the intake pipe 18 via the reflux pipe 22 increases. At this time, the flow rate of fresh air taken in from the intake pipe 18 decreases, and this change is fed back to the electric control device 10 by the air amount detector 19. Then, the solenoid valve 9 closes when a ratio of fresh air and recirculated exhaust gas suitable for the load is obtained.

When the pressure in the chamber 16 becomes high again and the piston 15 moves to the left to increase the opening degree of the intake valve 20 again, the change in the opening degree of the intake valve 20 is electrically controlled as a feedback signal to the air amount detector 19. is applied to the device 10, compared with the engine load and opens the solenoid valve 9 again. In this way, the electromagnetic valve 9 is intermittently opened and closed in response to changes in load and its magnitude, and the pressure in the chamber 16 is adjusted. As the electromagnetic valve, a proportional control type one, that is, one in which the degree of opening of the passage changes depending on the strength of the current applied to the electromagnetic coil, may be used.

Conversely, when the engine load decreases, the solenoid valve 9 closes and only the solenoid valve 8 opens, the pressure applied to the chamber 14 through the passages 28, 29 decreases, and the force of the spring 11 causes the piston 15 to move to the left. The fuel in the chamber 14 flows through the passages 29, 28 and the solenoid valve 8 in the passage 33.
The fuel is returned to the fuel tank 13 through piston 15
The opening degree of the intake valve 20 increases with the leftward movement of
The static pressure at the outlet 22a of the recirculation pipe 22 increases accordingly, and the amount of exhaust gas recirculated from the recirculation pipe 22 to the intake pipe 18 decreases. At this time, the flow rate of fresh air taken in from the intake pipe 18 increases, and this change is fed back to the electric control device 10 by the air amount detector 19. Then, the solenoid valve 8 is intermittently opened and closed, the hydraulic actuator 24 is controlled, the opening degree of the intake valve 20 is adjusted, and the exhaust recirculation rate is adjusted so that the flow rate of fresh air becomes a value commensurate with the reduction in load. controlled in relation to engine load.

As shown in FIG. 1, this exhaust gas recirculation rate is set in advance in the electric control device 10 so that it becomes maximum at the 3/4 load where the NOx concentration is highest. In reality, the electromagnetic valves 8 and 9 are not driven alternately, but are both opened and closed intermittently, and the ratio of the opening and closing times is controlled by the electric control device 10. That is, the opening/closing time ratio of the solenoid valve 9 is controlled mainly in response to changes in the engine speed, and the ratio of the opening/closing time of the solenoid valve 8 becomes smaller than that of the solenoid valve 9 in response to changes in the load. , conversely, the percentage of open time increases as the load decreases. Therefore,
The pressure in the fuel reservoir chamber of the fuel injection device 26 is intermittently released from the passage 33 or the passage 32 to the fuel tank 13, and the pressure in the fuel reservoir chamber is intermittently released to the fuel tank 13 from the passage 33 or 32. Pressure changes are suppressed and maintained almost constant. This prevents the injection timing adjustment device 7, which operates in response to the increase in engine speed, from advancing the injection timing, which helps to suppress the amount of NOx generated in the exhaust gas.

The electric control device 10 constitutes an electronic central processing unit, and when a supercharger is installed in the engine, it adjusts the recirculation amount commensurate with the air supercharging based on the signal from the air amount detector 19. The signals sent from the electric control device 10 to the solenoid valves 8 and 9 are corrected so as to obtain the following. In the case of an engine without a supercharger, the desired effect can be obtained without providing the air amount detector 19.

〔Effect of the invention〕

As described above, the present invention is an exhaust gas recirculation control device for a diesel engine, in which a hydraulic actuator 24 that controls the opening degree of an intake valve 20 drives the hydraulic pressure of fuel discharged from the feed pump 2 of a fuel injection device 26 attached to the diesel engine. Since it is operated as a hydraulic power source, there is no need to provide a special hydraulic power source.
Helps reduce costs. Furthermore, the hydraulic actuator 24 is opened and closed by the electric control device 10 which receives input signals such as the intake air amount and the engine load to control the pair of solenoid valves 8 and 9, so that the optimal ratio between the fresh air amount and the exhaust gas recirculation amount is determined. Controlled only by the opening of the intake valve 20, the operation is reliable and highly accurate, and the exhaust recirculation rate can be maximized when operating at close to 3/4 of the maximum load of the engine that generates the most NOx. This makes it possible to effectively reduce the concentration of NOx in exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the load and exhaust gas recirculation amount of a diesel engine controlled by the exhaust gas recirculation control device of the present invention, and FIG. 2 is a configuration diagram of the exhaust gas recirculation control device of the engine according to the present invention. be. 1: Camshaft, 2: Feed pump, 3: Fuel control sleeve, 6: Injection amount detector, 7: Injection timing adjustment device, 8, 9: Solenoid valve, 10: Electric control device,
13: fuel tank, 18: intake pipe, 19: air amount detector, 20: intake valve, 22: recirculation pipe, 23: exhaust pipe, 24: hydraulic actuator, 25: rotation speed detector, 26: fuel injection device, 40: Aperture.

Claims (1)

[Claims] 1. A recirculation pipe that connects the exhaust pipe and intake pipe of the engine, an intake valve provided in a portion of the intake pipe upstream of the connection part with the recirculation pipe, and a hydraulic actuator for adjusting the opening degree of the intake valve. a means for connecting the hydraulic actuator and the discharge port side of the feed pump of the fuel injection device and guiding the discharged fuel of the feed pump to the hydraulic actuator; a solenoid valve for adjusting the fuel pressure applied to the hydraulic actuator; It consists of an electric control device for opening and closing the solenoid valve, and the electric control device receives electric signals corresponding to the rotational speed of the fuel injection device and the fuel injection amount, respectively, and controls the exhaust recirculation amount according to the engine load. An exhaust recirculation control device for a diesel engine, characterized in that: