JPH04362262A - Superchargeing pressure controller for turbocharger - Google Patents

Abstract

PURPOSE:To obtain superior NOx reducing effect by the recirculation of the exhaust gas having a low temperature, added with the common control for the upper limit of supercharging pressure. CONSTITUTION:A superecharge pressure controller is equipped with the first communication passage 8 for the communication between the upstream and downstream of the turbine 6a of a turbocharger 6 in an exhaust passage 5, the second communication passage 10 for the communication between the downstream of a compressor 6b in an intake passage 9 and the downstream of the turbine 6a in the exhaust passage 5, and a control valve 7 for closing the first communication passage 8 only during the time between the first supercharge pressure and the second supercharge pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boost pressure control system for a turbocharger used to improve the torque of an internal combustion engine.

0002

[Prior Art] A typical boost pressure control device for a turbocharger has a communication passage that bypasses the turbine on the exhaust side of the turbocharger, and opens and closes a control valve provided in this communication passage to control the turbine. This system adjusts the amount of exhaust gas passing through the turbine and controls the boost pressure generated by the compressor connected to the turbine.

Normally, the purpose of such boost pressure control is to prevent mechanical damage to the internal combustion engine due to the output generated at that time when the boost pressure becomes too high. It is only opened when the boost pressure exceeds a predetermined value.

Purification of exhaust gas is an important issue in internal combustion engines, and exhaust gas recirculation is well known as one of the methods for reducing NOx in exhaust gas.

[0005] This is H2, which accounts for most of the exhaust gas.
By introducing inert gases such as O, N2, and CO2 into the combustion mixture, the heat capacity of these inert gases lowers the maximum combustion temperature and reduces the amount of NOx generated.

[0006] This exhaust gas recirculation is a very efficient method in terms of reusing unnecessary exhaust gas, but it is normally This exhaust gas recirculation only takes place in low load ranges where the internal combustion engine does not require high torques.

[0007] An internal combustion engine with a turbocharger incorporating this exhaust gas recirculation mechanism was published in Japanese Patent Laid-Open No. 61
It is described in JP-A-55358. This is because the intake passage and exhaust passage are connected to each other by an exhaust gas recirculation passage equipped with a control valve that opens in the low load range, and particulates such as lead compounds contained in the exhaust gas are The intake side of this exhaust gas recirculation passage is connected to the intake passage downstream of the compressor to avoid fouling of the charger compressor, while the exhaust side is connected to the exhaust gas recirculation side against the boost pressure provided by this compressor. In order to achieve circulation, it is connected to the exhaust passage upstream of the turbine, in which a relatively high pressure exhaust gas is obtained.

[0008]

In the prior art described above, the exhaust gas recirculated into the cylinder is supplied from the upstream side of the turbine of the turbocharger because it requires a certain degree of pressure. The exhaust gas is at a high temperature immediately after being discharged from the cylinder.

[0009] The purpose of exhaust gas recirculation is to reduce NOx by lowering the combustion temperature, as mentioned above, and it is clear that this effect is reduced if the exhaust gas supplied is at a high temperature. .

Therefore, an object of the present invention is to provide a turbocharger boost pressure control device that not only controls the normal upper limit of boost pressure but also recirculates low-temperature exhaust gas to achieve a good NOx reduction effect. It is to be.

[0011]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a boost pressure control device for a turbocharger according to the present invention provides a boost pressure control device for a turbocharger in accordance with the present invention. a second communication passage that communicates the downstream side of the turbine in the exhaust passage with the downstream side of the compressor of the turbocharger in the intake passage; It is characterized by comprising a control valve that closes only between the supply pressure and a second supercharging pressure higher than the supply pressure.

0012

[Operation] The turbocharger boost pressure control device described above is
In the low load range of an internal combustion engine that does not require high torque, the first communication passage is opened to reduce the amount of exhaust gas passing through the turbocharger turbine, thereby lowering the supercharging pressure of the intake air by the compressor connected to the turbine. . Accordingly, the pressure of the exhaust gas on the downstream side of the turbine becomes higher than when all of the exhaust gas passes through the turbine and works because part of the exhaust gas bypasses the turbine.

The pressure of this exhaust gas becomes higher than the supercharging pressure of the supply air that has been lowered as described above, and the exhaust gas passes through the second communication passage that communicates the downstream side of the turbine in the exhaust passage with the downstream side of the compressor in the intake passage. A portion of the exhaust gas is fed into the cylinder.

[0014] The exhaust gas used for this recirculation is different from the exhaust gas immediately discharged from the cylinder, and is sufficiently cooled before reaching the downstream side of the turbine.
A good NOx reduction effect can be obtained as the combustion temperature is lowered by the inert gas in the exhaust gas.

[0015] When the load on the internal combustion engine increases, the exhaust gas pressure and the boost pressure of the air supply rise accordingly, and when the load reaches the first boost pressure when the load becomes a medium load, the first communication passage opens. Closed by control valve. As a result, the supercharging pressure of the intake air increases rapidly, preventing recirculation of exhaust gas, and increasing the filling efficiency in the cylinder, making it possible to improve torque.

When the boost pressure further increases and reaches a second boost pressure that causes serious problems to the internal combustion engine due to the generated torque, the control valve is opened again to reduce the boost pressure of the charge air. is controlled so that it does not rise any higher.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a boost pressure control system for a turbocharger according to the present invention. In the figure, 1 is a diesel engine, 2 is an exhaust manifold, and 3 is an intake manifold. The exhaust manifold 2 and the catalytic converter 4 for purifying exhaust gas are communicated through an exhaust passage 5, and the exhaust passage 5 is provided with a turbine 6a of a turbocharger 6. Further, the upstream and downstream sides of the turbine 6a of the exhaust passage 5 are communicated by a first communication passage 8 having a control valve 7.

On the other hand, an intake passage 9 communicating with the intake manifold 3 is provided with a compressor 6b connected to a turbine 6a of the turbocharger 6. Immediately before the catalytic converter 4 on the downstream side, the second communication passage 10 communicates with the catalytic converter 4 .

FIG. 2 is a cross-sectional view of the actuating device 11 of the control valve 7 provided in the first communication path 8. As shown in FIG. In FIG. 2(A), the control valve 7 includes an L-shaped arm 1 whose corner portion is pivotally connected to a wall portion 8a that divides the upstream side and the downstream side of the first communication path 8.
It is fixed to one end of 2. In addition, the first diaphragm 1 of the actuating device 11 is inserted into the elongated hole at the other end of the L-shaped arm 12.
The tip of the connecting rod 13 fixed to 1a is connected with a pin. As a result, the actuating device 11 moves the connecting rod 13 in the right direction in the figure, so that the control valve 7 is activated in the wall portion 8a.
The first communicating path 8 is closed by blocking the opening 8b of the opening 8b, and the first communicating path 8 is opened by moving it leftward from that position, as shown in the figure.

The actuating device 11 has a first pressure chamber 11c and a second pressure chamber 11d, both of which are supplied with supercharging pressure of intake air through a communication passage 11b, on the connecting rod 13 side and the opposite side thereof.
The first diaphragm 11a is in the first pressure chamber 11c.
However, there is also a first diaphragm 11a in the second pressure chamber 11d.
A second diaphragm 11e having a larger diameter is supported by the first spring 11f and the second spring 11g so as to face each other. As mentioned above, the first diaphragm 11a
The connecting rod 13 is fixed to extend outward, and a gap corresponding to the stroke of the connecting rod 13 is formed between the second diaphragm 11e and the end of the connecting rod 13 on the first diaphragm 11a side. pin 1 extending inwardly so that
1h is fixed.

The first spring 11f supporting the first diaphragm 11a starts to be compressed when the pressure in the first pressure chamber 11c reaches the first supercharging pressure, and the second spring 11f supporting the second diaphragm 11e The spring 11g is the second pressure chamber 11
Compression begins when the pressure within d reaches a second supercharging pressure that is higher than the first supercharging pressure.

FIG. 3(A) is a graph showing the boost pressure and the exhaust pressure downstream of the turbine with respect to the load when the turbocharger boost pressure control device of this embodiment is used. ) is a similar graph when a conventional turbocharger boost pressure control device is used.

In the turbocharger supercharging pressure control system of this embodiment, in a low load range where high torque is not required, the actuating device 11 is in the state shown in FIG. , a part of the exhaust gas passes through the first communication path 8, and the amount of exhaust gas passing through the turbine 6a is reduced. Accordingly, as shown in FIG. 3, the supercharging pressure of the intake air by the compressor 6b becomes lower than in the past, and at the same time, since a part of the exhaust gas does not perform work on the turbine 6a, The side exhaust pressure is higher than before, and this pressure exceeds the intake boost pressure.

Therefore, part of the exhaust gas is supplied into the cylinder through the second communicating passage 10 that communicates the downstream side of the turbine 6a in the exhaust passage 5 with the downstream side of the compressor 6b in the intake passage 9. Since the exhaust gas comes from just before the catalytic converter 4 on the downstream side of the turbine 6a, it has been sufficiently cooled by the time it reaches this part, and the combustion temperature in the cylinder due to the inert gas that makes up the majority of the exhaust gas is low. The NOx reduction effect associated with the reduction becomes better.

When the load increases further and reaches a medium load range where torque is required, the intake supercharging pressure gradually increases as the exhaust pressure from the cylinder increases due to the increase in load, as shown in FIG.
P1 in A) is reached. At this time, in the actuating device 11 of the control valve 7 to which supercharging pressure is constantly supplied, only the first spring 11f supporting the first diaphragm 11a starts to be compressed, as shown in FIG. 2(B).

As a result, the connecting rod 13 fixed to the first diaphragm 11a moves rightward in the figure until it comes into contact with the pin h of the second diaphragm 11e, and at this time,
Since the control valve 7 closes the first communication passage 8 and all of the exhaust gas passes through the turbine 6a, the supercharging pressure of the intake air increases rapidly as shown in FIG. 3(A), and the filling effect in the cylinder increases. increases, making it possible to obtain the required higher torque. On the other hand, this supercharging pressure exceeds the exhaust pressure on the downstream side of the turbine 6a, as shown in FIG. No circulation takes place.

Further, when the load becomes high and the intake supercharging pressure reaches P2 in FIG. 3(A), the actuating device 11 of the control valve 7 operates the second diaphragm as shown in FIG. 2(C). The second spring 11g supporting spring 11e also begins to be compressed. At this time, the first diaphragm 11a is deformed into a convex shape inward, and the end of the connecting rod 13 fixed thereto is in contact with the pin 11h of the second diaphragm 11e, and the pressure between the first diaphragm 11a and the second diaphragm 11e is received. Although the pressures in both pressure chambers 11c and 11d are the same due to the difference in area, the connecting rod 13 and the pin 11h move to the left in the figure while being in contact with each other.

As a result, the control valve 7 is again connected to the first communication passage 8.
is opened and the supercharging pressure is maintained at P2 as in the past, so that the supercharging pressure does not become too high and the generated torque does not cause any serious problems to the diesel engine 1. Also at this time, as shown in FIG. 3(A), the supply pressure exceeds the exhaust pressure, and as in the medium load range, the exhaust gas is not recirculated with a reduction in torque.

Furthermore, in the medium to high load range of an internal combustion engine, the intake boost pressure is higher than the exhaust pressure, so not only is the exhaust gas not recirculated with a reduction in torque, but also the exhaust gas is not recirculated at a relatively low temperature. Intake air flows into the exhaust passage, making it possible to further lower the temperature of the exhaust gas, which has the effect of reducing the amount of harmful hydrogen sulfide compounds generated from the catalytic converter as the exhaust temperature increases.

[0030]

As described above, according to the turbocharger boost pressure control device according to the present invention, in addition to controlling the upper limit of the normal boost pressure, it is also possible to control the upper limit of the normal boost pressure. In this region, a good NOx reduction effect can be achieved using low-temperature exhaust gas. In addition, because only low-temperature exhaust gas passes through the piping that connects the exhaust passage downstream of the turbine and the intake passage downstream of the compressor, the expensive heat-resistant piping that was previously required is no longer necessary, and supercharging By controlling the pressure appropriately, the exhaust gas recirculation control valve conventionally provided in this piping can be omitted.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a boost pressure control device for a turbocharger according to the present invention.

FIG. 2 is a sectional view of a control valve actuating device used in the boost pressure control device for a turbocharger according to the present invention;
) is a state in which the boost pressure is below the first pressure, (B) is a state in which the boost pressure is between the first pressure and the second pressure, and (C) is a state in which the boost pressure is above the second pressure. Indicates the status of

FIG. 3 is a graph showing the intake boost pressure and the downstream exhaust pressure of the turbocharger turbine with respect to the load of the internal combustion engine; (A) is a graph when the turbocharger boost pressure control device according to the present invention is used; , (B) shows the case where a conventional turbocharger boost pressure control device is used.

[Explanation of symbols]

1...Diesel engine 2...Exhaust passage 6a...Turbine 6b...Compressor 7...Control valve 8...First communication path 9...Intake passage 10...Second communication path 11... Actuation device

Claims (1)

[Claims] 1. A first communication passage that communicates an exhaust passage upstream and downstream of a turbine of a turbocharger, and an exhaust passage downstream of the turbine and an intake passage downstream of a compressor of the turbocharger. and a control valve that closes the first communication passage only between a first supercharging pressure of intake air by the compressor and a second supercharging pressure higher than the first supercharging pressure of intake air by the compressor. Characteristic turbocharger boost pressure control device.