JPH04358721A - Supercharged pressure control device of turbo charger - Google Patents

Abstract

PURPOSE:To improve purifying action of a catalyst converter by increasing the temperature of exhaust gas when it is low and reduce the amount of hydrogen sulfide compound generated by the catalyst converter by reducing the temperature of the exhaust gas at the time of a high temperature, in case of controlling the supercharged pressure control device of a turbo charger. CONSTITUTION:The supercharged pressure control device of a turbo charger is provided with a first communicating passage 11 having a first control valve 9, wherein the upper steam side and the lower steam side of the turbine 6a of a turbo charger 6 are communicated to each other, and a second communicating passage 12 having a second control valve 10, wherein the lower stream side of a compressor 6b is communicated with the lower stream side of the turbine 6a. Supercharged pressure is controlled by the first control valve 9 when an exhaust temperature is low, and it is controlled by the second control valve 10 when the temperature is high.

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 in an internal combustion engine.

0002

[Prior Art] In order to improve the output of an internal combustion engine, a turbocharger is known in which the exhaust gas is used to rotate a turbine, and a compressor connected to the turbine supercharges intake air. .

[0003] In such a turbocharger, a higher supercharging pressure is preferable because a higher output can be obtained, but if the supercharging pressure is too high, the output generated at that time can cause severe problems for the internal combustion engine. arise.

[0004] Therefore, the turbocharger requires a boost pressure control device to prevent the boost pressure from exceeding a predetermined value. As such a device, a passage is provided that bypasses the turbine in the exhaust passage, and by opening and closing a control valve in that passage, the amount of exhaust gas passing through the turbine is adjusted, the rotation speed of the compressor is controlled, and the boost pressure is maintained at a predetermined level. There are known methods to suppress the
(See Publication No. 17).

[0005]

An internal combustion engine is usually provided with a catalytic converter near the outlet of an exhaust passage, which purifies hydrocarbons and the like in exhaust gas by the action of a catalyst. This type of catalytic converter is an extremely excellent exhaust treatment device in that it does not place a significant burden on the internal combustion engine itself, so it does not reduce fuel efficiency or operating conditions. However, it is not effective due to the characteristics of the catalyst used. There is a temperature of the exhaust gas that does not work.

Oxidation catalysts commonly used as catalysts have a lower exhaust purification rate as the exhaust temperature decreases.
When the exhaust gas temperature drops below a certain temperature, the catalyst becomes inactive.
Almost no exhaust gas can be purified. Further, such a catalyst generates a small amount of hydrogen sulfide compounds, which are harmful substances, due to the sulfur content in the fuel, but the amount of hydrogen sulfide compounds generated increases rapidly when the exhaust gas temperature exceeds a certain temperature.

Depending on the operating conditions of the internal combustion engine, the supercharging pressure of the turbocharger may exceed a predetermined value regardless of the exhaust temperature. In the conventional technology described above, when the exhaust temperature immediately before the catalytic converter is below the temperature that makes the catalyst inactive, a portion of the exhaust gas bypasses the turbine in order to lower the boost pressure. Since the gas does not perform any work on the turbine, it maintains almost the same temperature as when it was discharged from the cylinder, and the temperature of the entire exhaust immediately before the catalytic converter increases, which activates the catalyst and produces a purifying effect. will improve.

However, even when the exhaust gas temperature immediately before the catalytic converter is above the temperature at which the amount of hydrogen sulfide compounds generated rapidly, the exhaust temperature is similarly increased and the amount of hydrogen sulfide compounds generated is further increased. It turns out.

Therefore, an object of the present invention is to increase the boost pressure when the exhaust temperature is low to improve the purifying action of the catalytic converter, and to lower it when the exhaust temperature is high to reduce hydrogen sulfide compounds. It is an object of the present invention to provide a boost pressure control device for a turbocharger that reduces generation amount.

0010

[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 communicates the upstream side and the downstream side of the turbine of the turbocharger in the exhaust passage. A first communication passage provided with a first control valve communicates with an intake passage downstream of the compressor of the turbocharger and an exhaust passage downstream of the turbine, and a second communication passage provided with a second control valve. When controlling boost pressure, the exhaust temperature immediately before the catalytic converter is
When the temperature is below a first predetermined temperature, only the first control valve is opened, and when the temperature is above a second predetermined temperature, which is higher than the first predetermined temperature, only the second control valve is opened. It is characterized by

[0011]

[Operation] According to the turbocharger boost pressure control device described above, when the boost pressure exceeds a predetermined value and when controlling it, if the exhaust temperature immediately before the catalytic converter is low, a part of the exhaust gas is By reducing the amount of exhaust gas that passes through the turbine through the first communication passage, the boost pressure is lowered, and in order to maintain the temperature at which the exhaust gas that passes through the first communication passage is discharged from the cylinder, the entire exhaust gas immediately before the catalytic converter is The temperature of
The exhaust purification effect of the catalyst can be improved.

Furthermore, when the exhaust temperature immediately before the catalytic converter is high, part of the intake air supplied by the compressor is discharged through the second communication passage to lower the supercharging pressure.
Along with this, since the second communication passage communicates with the downstream side of the turbine in the exhaust passage, the relatively low temperature of the intake air causes
The exhaust gas temperature immediately before the catalytic converter is lowered, and the amount of hydrogen sulfide compounds generated can be reduced.

[0013]

Embodiment FIG. 1 shows an embodiment of a turbocharger boost pressure control device. In the figure, 1 is a diesel engine, 2 is an exhaust manifold, 3 is an intake manifold, and 4 is a catalytic converter for exhaust treatment. A turbine 6a of a turbocharger 6 is provided in an exhaust passage 5 communicating with the exhaust manifold 2 and the catalytic converter 4, and a compressor 6b connected to the turbine 6a is provided in an intake passage 7 communicating with the intake manifold 3.

Further, a thermometer 8 is installed immediately before the catalytic converter 4 to measure the temperature of the exhaust gas at that part, and a first control valve 9 is controlled to open and close based on the measured temperature.
and a first communication passage 11 each having a second control valve 10.
A second communication passage 12 communicates the downstream side of the turbine 6a in the exhaust passage 5 with the upstream side of the turbine 6a in the exhaust passage 5 and the downstream side of the compressor 6b in the intake passage 7, respectively.

FIG. 2 shows the purification rate of the oxidation catalyst used in the catalytic converter 4 with respect to exhaust temperature, and FIG. 3 shows the amount of hydrogen sulfide compounds generated. As shown in Figure 2, the purification rate is
It decreases as the exhaust gas temperature decreases, and becomes very low below temperature T1 in the figure because the catalyst becomes inactive. Further, as shown in FIG. 3, the amount of hydrogen sulfide compounds generated gradually increases as the exhaust gas temperature rises, and rapidly increases at temperature T2 in the figure.

Depending on the operating condition of the diesel engine 1, the supercharging pressure of the turbocharger 6 may exceed a predetermined value regardless of the exhaust temperature. Check exhaust temperature with thermometer 8
When the temperature is equal to or lower than the temperature T1 shown in FIG. By lowering the rotational speed of the compressor 6b connected thereto, the supercharging pressure is lowered to a predetermined value or less, and accordingly, the exhaust temperature immediately before the catalytic converter 4 is lowered by lowering the rotation speed of the compressor 6b connected thereto.
Since the temperature inside the exhaust manifold 2 is increased by a portion of the almost maintained exhaust gas without passing through the exhaust gas, the exhaust gas purification rate by the catalyst can be improved.

[0017] Furthermore, the measured temperature is the temperature T2 shown in FIG.
In such a case, by opening the second control valve 10 and letting a part of the intake air pass through the second communication path, the supercharging pressure generated by the compressor 6b is lowered to a predetermined value or less, and accordingly, the supercharging pressure generated by the compressor 6b is lowered to a predetermined value or less. Intake air is discharged into the exhaust passage 5 immediately before the catalytic converter 4, thereby lowering the exhaust temperature, thereby making it possible to reduce hydrogen sulfide compounds generated by the catalyst.

When the exhaust gas temperature immediately before the catalytic converter 4 is between the above-mentioned temperatures T1 and T2, and the measured temperature is a certain distance from T1 and T2, either one of the control valves 9 and 10 is opened. However, when the exhaust temperature is around T1, if the second control valve 10 is opened to lower the exhaust temperature, T1 will be achieved.
Since the following may occur, the first control valve 9 is opened to lower the supercharging pressure. Conversely, when the exhaust gas temperature is around T2, the second control valve 10 is opened to lower the supercharging pressure.

In this embodiment, since supercharging pressure control can be performed using either the first or second communication path,
Even if one of the first and second control valves provided therein malfunctions, the other one can take care of it, improving the reliability of boost pressure control of the turbocharger.

[0020]

As described above, according to the boost pressure control device for a turbocharger according to the present invention, when controlling the boost pressure in a cold period when the exhaust temperature is low, the exhaust temperature is simultaneously raised to control the exhaust gas by the catalytic converter. The purification effect is improved, and when the supercharging pressure is controlled during high-speed loads where the exhaust temperature is high, the exhaust temperature can be simultaneously lowered and the amount of hydrogen sulfide compounds generated by the catalytic converter can be reduced.

[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 graph showing the exhaust gas purification rate with respect to the exhaust temperature of the oxidation catalyst.

FIG. 3 is a graph showing the amount of hydrogen sulfide compounds generated versus the exhaust temperature of the oxidation catalyst.

[Explanation of symbols]

1...Diesel engine 4...Catalytic converter 6a...Turbine 6b...Compressor 8...Thermometer 9...First control valve 10...Second control valve 11...First communication path 12...Second communication path

Claims (1)

[Claims] 1. A first communication passage that communicates the upstream side and the downstream side of the turbine of the turbocharger in the exhaust passage and is provided with a first control valve; and the downstream side of the compressor of the turbocharger in the intake passage; a second communication passage in which the exhaust passage communicates with the downstream side of the turbine and is provided with a second control valve, and when controlling the boost pressure, the exhaust temperature immediately before the catalytic converter is set to a first predetermined temperature. The turbo is configured such that only the first control valve is opened at the following times, and only the second control valve is opened when the temperature is higher than a second predetermined temperature higher than the first predetermined temperature. Charger boost pressure control device.