JPS624663Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an exhaust gas recirculation device for a diesel engine.

As one measure against air pollution in automobile engines, there is an exhaust recirculation device that suppresses the generation of nitrogen oxides (NOx) by recirculating a portion of the exhaust gas to the intake side and lowering the combustion temperature.
This device is being adopted not only for gasoline engines but also for diesel engines.

Conventionally, exhaust recirculation devices for diesel engines have included an exhaust recirculation passage that communicates the intake passage with the exhaust passage, and a throttle valve upstream of the opening of the exhaust recirculation passage in the intake passage to facilitate the recirculation of exhaust gas. It is generally known that a throttle valve is provided and the throttle valve is closed by a certain opening degree during exhaust gas recirculation. However, with this structure, it is difficult to control exhaust gas recirculation, and there are often problems in which the intake air is throttled too much, which hinders engine rotation, or conversely, the exhaust gas recirculation effect is reduced due to insufficient throttling. Furthermore, as seen in Japanese Utility Model Publication No. 53-19299, a fixed throttle is provided in the exhaust gas recirculation passage, and a throttle valve provided upstream of the exhaust gas recirculation passage opening in the intake passage is operated in synchronization with the fuel pump lever. There is something like this. However, even with this structure, there is a risk that the intake air will be throttled too much at low loads, causing problems with engine rotation.Also, even in the operating range where exhaust gas recirculation should be performed, the amount of exhaust gas recirculation decreases as the load increases. However, there were drawbacks such as the inability to sufficiently reduce nitrogen oxides (NOx).

Note that some exhaust gas recirculation devices used in gasoline engines are designed to control the amount of exhaust gas recirculation with high precision according to various operating conditions.
Such a device has a very complicated structure and is expensive, and it is difficult to use a device with such a complicated structure in a diesel engine, which does not require the same level of precision control as in the case of a gasoline engine, from an economical point of view. Undesirable.

In view of this situation, the present invention has a simple structure, yet sufficiently reduces nitrogen oxides (NOx).
Further, the present invention provides an exhaust gas recirculation device for a diesel engine that can appropriately control the amount of exhaust gas recirculation so as to maintain good engine performance.

That is, the exhaust gas recirculation device for a diesel engine of the present invention includes an exhaust gas recirculation valve that opens and closes an exhaust gas recirculation passage, and an actuator that drives a throttle valve provided upstream of the exhaust gas recirculation passage opening in the intake passage to a predetermined opening direction. , a control circuit that outputs an operating signal to the exhaust recirculation valve and the actuator, and a correction device that corrects the throttle opening degree of the actuator according to the intake passage pressure downstream of the throttle valve, and the correction device causes the throttle valve to open when the actuator is operated. The structure is such that the pressure in the downstream intake passage is maintained approximately constant.

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

In FIG. 1, 1 is a diesel engine main body, 2 is an intake passage, 3 is an exhaust passage, and 4 is an exhaust gas recirculation passage that communicates the exhaust passage 3 and the intake passage 2. The exhaust gas recirculation passage 4 is opened and closed by an exhaust gas recirculation valve 5 comprising a valve body 5a provided in the passage 4 and a diaphragm type valve body actuating portion 5b. Further, a throttle valve 6 is provided in the intake passage 2 upstream of the opening of the exhaust gas recirculation passage 4 . This throttle valve 6
is an actuator 8 and a correction device 9, which will be described in detail later.
Rod 1 is added to the throttle valve operation correction device 7 which is a combination of
Connected via 0.

The valve body actuating portion 5b of the exhaust gas recirculation valve 5 and the actuator 8 for actuating the throttle valve are connected to a vacuum pump 11 serving as a driving source thereof, and a vacuum introduction passage 12 and a branch passage 12 from the passage 12.
They are connected via a and 12b. A three-way solenoid valve 13 is interposed in the vacuum introduction passage 12 to switch the passage 12 between a state in which it is open to the atmosphere and a state in which it is communicated with the vacuum pump 11. Further, an orifice 14 is provided in a branch passage 12b of the passage 12 to the accumulator 8.

Reference numeral 15 denotes a control circuit that outputs an operating signal for the exhaust gas recirculation valve 5 and the actuator 8, and the operating signal is sent to the three-way solenoid valve 13, whereby the vacuum introduction passage 12 communicates with the vacuum pump 11. The three-way solenoid valve 13 is switched to the state. The control circuit 15 generates an activation signal when operating conditions are appropriate for exhaust gas recirculation. For example, based on the signals from the load sensor 16 and the engine speed sensor 17, which detect the load based on the position of the accelerator or fuel pump lever, etc., the driving range corresponds to city driving where the load and engine speed are below a predetermined value. In this case, an activation signal is generated to cause exhaust gas recirculation, and exhaust gas recirculation is not performed in a high load range and a high speed rotation range above a predetermined value.

As shown in detail in FIG.
partitioning the atmospheric chamber 82 and the first negative pressure chamber 83, and
The first negative pressure chamber 83 is connected to the vacuum introduction passage 12.
The actuator 8 connected to the branch passage 12b and the second diaphragm 91 create a second negative pressure chamber 92.
and a second atmospheric chamber 93, and the second negative pressure chamber 92 is connected to the intake passage 2 downstream of the throttle valve 6 through a communication passage 9.
A correction device 9 communicated with each other via 4 is collectively equipped. The first negative pressure chamber 83 and the second negative pressure chamber 92 are adjacent to each other with the fixed partition wall 71 in between. In addition, the first and second diaphragms 81 and 91
are connected to each other by a rod 72 passing through a fixed partition wall 71, and a rod 1 is connected to the throttle valve 6.
Connected via 0. In this manner, in the actuator 8, when the negative pressure from the vacuum pump 11 is introduced into the first negative pressure chamber 83, the first diaphragm 81 is actuated by a certain amount in the direction of closing the throttle valve 6 as shown by arrow A. let on the other hand,
In the correction device 9, the throttle valve 6 is opened as shown by the arrow B as the intake negative pressure increases, which is introduced into the second negative pressure chamber 92 from the intake passage 2 downstream of the throttle valve 6. the second diaphragm 9 in the direction
1 is configured to operate. Further, in the second atmospheric chamber 93, a filter spring 9 for adjusting the intake negative pressure set value is provided.
5 is equipped.

In FIG. 1, 20 is a supercharger, which has a turbine 21 provided in the exhaust passage 3, a blower 22 provided in the intake passage 2, and a shaft 23 connecting these. The turbine 21 rotates, and the blower 22 rotates in conjunction with the turbine 21, thereby supercharging the intake air. Further, 24 is a passage provided in the exhaust passage 3 that bypasses the turbine 21, 25 is a bypass valve that opens and closes the bypass passage 24, and 26 is a diaphragm device that opens the bypass valve 25 when the boost pressure exceeds a predetermined value. , these constitute a supercharging pressure control device that controls the supercharging pressure so that it does not exceed a predetermined value.

Next, the operation of the exhaust gas recirculation device will be explained.

When an actuation signal is output from the control circuit 15 based on the detection signals from the load sensor 16 and the rotation speed sensor 17, the three-way solenoid valve 13 is switched in response, and the negative pressure caused by the vacuum pump 11 is exhausted. It is applied to the valve body operating portion 5b of the reflux valve 5 and the first negative pressure chamber 83 of the actuator 8. As a result, the exhaust gas recirculation passage 4 is opened, and the throttle valve 6 is closed to a predetermined opening degree. In this way, during exhaust gas recirculation, the intake passage 2 is throttled to some extent by the throttle valve 6, the intake passage pressure downstream of the throttle valve 6 is lowered, and the exhaust gas recirculation is assisted.

In this case, if the throttle valve 6 is throttled too much and the negative pressure in the intake passage 2 downstream thereof increases, this negative pressure acts on the second diaphragm 91 in the second negative pressure chamber 92 of the correction device 9, 2 diaphragm 91
is pulled toward the second negative pressure chamber 92, thereby operating the throttle valve 6 in the valve opening direction. Further, as the throttle valve 6 is opened, the negative pressure introduced from the intake passage 2 downstream thereof into the second negative pressure chamber 92 becomes smaller, and the first negative pressure chamber 83 of the actuator 8 is opened.
Due to the suction force acting on the diaphragm 81,
The throttle valve 6 is operated in the valve closing direction. In this way, the constant negative pressure applied to the first negative pressure chamber 83 by the vacuum pump 11, the elastic force of the spring 95, and the flow from the intake passage 2 downstream of the throttle valve 6 to the second negative pressure chamber The opening degree of the throttle valve 6 is corrected so that it is balanced with the intake negative pressure introduced into the throttle valve 92, and the intake negative pressure downstream of the throttle valve 6 is kept substantially constant. Therefore, by setting the elastic force of the spring 95 to an appropriate value in advance, when the actuator 8 is operated, the amount of exhaust gas recirculation that is preferable for reducing nitrogen oxides (NOx) can be achieved without hindering engine rotation. The intake negative pressure downstream of the throttle valve 6 can be maintained in the state obtained.

The specific structure of the device of the present invention is not limited to the above embodiments, and can be modified in various ways.

For example, the actuator 8 for operating the throttle valve and the correction device 9 can be constructed as shown in FIG. That is, in the figure, the diaphragm 81' of the actuator 8 is connected to the throttle valve 6 via the rod 10, its negative pressure chamber 83' is connected to the vacuum introduction passage 12', and the vacuum introduction passage 12' is connected to the vacuum introduction passage 12' as a correction device. A leak passage 96 that branches from the air passage 12' and opens to the atmosphere, a valve body 97 disposed in the leak passage 96, and a correction valve that operates the valve body 97 in accordance with the intake negative pressure downstream of the throttle valve 6. A diaphragm device 98 is provided. The amount of leak from the leak passage 96 is controlled in accordance with the intake negative pressure introduced into the negative pressure chamber 98a of the correction diaphragm device 98 via the communication passage 99. With this structure as well, when the actuator is operated, the opening degree of the throttle valve 6, which controls the pressure in the negative pressure chamber 83' of the actuator 8, is corrected, so that the intake negative pressure downstream of the throttle valve 6 is almost reduced. a spring 8 which is kept constant and which is provided on the actuator 8 and the compensating diaphragm device 98;
4,98b allows the intake negative pressure to be set appropriately.

Further, the structure of the exhaust recirculation valve 5 is not limited to the above-mentioned embodiment. For example, although not shown in the drawings, the valve body actuating portion is communicated with the exhaust passage so that it can respond to exhaust pressure, and the communication passage is A solenoid valve is provided, and when an actuation signal is received from the control circuit 15, the solenoid valve opens and introduces exhaust pressure into the valve body actuating section;
This may open the exhaust gas recirculation passage.

As explained above, in the exhaust recirculation device for a diesel engine of the present invention, when the exhaust recirculation passage is opened, the throttle valve provided upstream of the exhaust recirculation passage opening of the exhaust passage is closed to a predetermined opening by the actuator. At the same time, a correction device corrects the throttle valve opening according to the intake passage pressure downstream of the throttle valve.
Since the intake passage pressure downstream of the throttle valve is maintained almost constant when the actuator is activated,
Although the structure is simple, it is possible to always maintain an appropriate pressure in the intake passage downstream of the throttle valve in the operating range where exhaust gas recirculation is performed, and effective exhaust gas recirculation can be performed.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the device of the present invention, Fig. 2 is an enlarged view of an actuator and correction device for actuating the throttle valve, and Fig. 3 is an enlarged view showing another embodiment of the actuator and correction device. be. 1... Diesel engine body, 2... Intake passage, 3... Exhaust passage, 4... Exhaust recirculation passage, 5...
...Exhaust recirculation valve, 6... Throttle valve, 8... Actuator, 9... Correction device, 15... Control circuit.

Claims (1)

[Scope of utility model registration request] In addition to providing an exhaust gas recirculation passage that communicates the exhaust passage and the intake passage of the engine, a throttle valve is disposed upstream of the opening of the exhaust gas recirculation passage in the intake passage, and the throttle valve is closed to a predetermined opening during exhaust gas recirculation. In the diesel engine exhaust recirculation system,
an exhaust recirculation valve that opens and closes the exhaust gas recirculation passage; an actuator that drives the throttle valve in a direction that closes it to a predetermined opening; a control circuit that outputs an operating signal to the exhaust gas recirculation valve and the actuator; and an intake passage pressure downstream of the throttle valve. and a correction device for correcting the opening degree of the throttle valve by the actuator according to the above, and the correction device maintains the intake passage pressure downstream of the throttle valve at a substantially constant level when the actuator is operated. Exhaust recirculation device.