COMPRESSOR BYPASS DURING START-UP

Abstract

An internal combustion engine comprising at least one turbo charger, which comprises a compressor, at least one bypass valve, through which the compressor can be bypassed by at least a partial stream of air or an air-fuel mixture, and a control unit is provided. The control unit is configured to open or closed loop control the bypass valve. As such, the control unit is configured to at least partially open the at least one bypass valve and keep the at least one bypass valve open during a start of the internal combustion engine. The control unit is also configured to keep the at least one bypass valve open until an engine parameter of the internal combustion engine satisfies a predetermined startup criterion.

Claims

1. An internal combustion engine comprising: at least one turbo charger, which comprises a compressor; at least one bypass valve, through which the compressor can be bypassed by at least a partial stream of air or an air-fuel mixture; and a control unit configured to open or closed loop control the bypass valve; wherein the control unit is configured to at least partially open the at least one bypass valve and keep it open during a start of the internal combustion engine, and wherein the control unit is configured to keep the at least one bypass valve open until an engine parameter of the internal combustion engine satisfies a predetermined startup criterion.

2. The internal combustion engine as set forth in claim 1, wherein the engine parameter is a pressure difference before and after the compressor in flow direction, and wherein the predetermined startup criterion is a predetermined pressure difference.

3. The internal combustion engine as set forth in claim 1, wherein the engine parameter is a rotational speed of the turbo charger or the internal combustion engine, wherein the predetermined startup criterion is a lower threshold, and wherein the control unit keeps the at least one bypass valve open until the rotational speed attains or exceeds the predetermined lower threshold.

4. The internal combustion engine as set forth in claim 1, wherein the engine parameter is a time since a beginning of a start procedure, wherein the predetermined startup criterion is a lower threshold, and wherein the control unit keeps the at least one bypass valve open until the time since the start attains or exceeds the predetermined lower threshold.

5. The internal combustion engine as set forth in claim 1, wherein the predetermined startup criterion is chosen such that it is fulfilled at such a point in time, when the internal combustion engine is running without the action of an auxiliary drive.

6. The internal combustion engine as set forth in claim 1, wherein at least one upstream sensor is provided in flow upstream of the compressor, and wherein the at least one upstream sensor (6) is configured to provide the control unit with a characteristic signal for an upstream pressure.

7. The internal combustion engine as set forth in claim 1, wherein at least one downstream sensor is provided in flow direction downstream of the compressor, and wherein the at least one downstream sensor is configured to provide the control unit with a characteristic signal for a downstream pressure.

8. The internal combustion engine as set forth in claim 6, wherein the control unit is configured to determine a pressure difference, from measurement of the at least one downstream sensor and the measurements of the at least one upstream sensor.

9. The internal combustion engine as set forth in claim 1, wherein at least one rotational speed sensor is provided to determine a characteristic signal for the rotational speed of the internal combustion engine or the turbo charger, and wherein the control unit can be provided with the characteristic signal of the at least one rotational speed sensor.

10. The internal combustion engine as set forth in claim 1, wherein the control unit is configured to open or closed loop control the opening degree of the bypass valve.

11. The internal combustion engine as set forth in claim 1, wherein the control unit is a mechanical and/or electronic control unit.

12. The internal combustion engine as set forth in claim 1, wherein at least one further component of the internal combustion engine can be bypassed by the at least one bypass valve.

13. A method for operating an internal combustion engine with at least one turbo charger as set forth in claim 1, the method comprising: providing a bypass valve for bypassing a compressor of the at least one turbo charger; and keeping the bypass valve at least partially open during a start of the internal combustion engine until an engine parameter of the internal combustion engine satisfies a predetermined startup criterion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further details of the present disclosure will be described with reference to the specific description hereinafter. In the drawing:

[0028] FIG. 1 shows a first embodiment of an international combustion engine,

[0029] FIG. 2 shows second embodiment of an international combustion engine, and

[0030] FIG. 3 shows third embodiment of an international combustion engine.

DETAILED DESCRIPTION

[0031] FIG. 1 shows a first embodiment of an international combustion engine 1, wherein the internal combustion engine 1 comprises a turbo charger 2. By means of the turbo charger 2 air or an air-fuel mixture can be charged for the combustion in the internal combustion engine 1. This air or air-fuel mixture is charged by the compressor 3 of the turbo charger 2. The turbo charger 2 further comprises an exhaust gas turbine 9, which is connected to the compressor 3 by a shaft. The exhaust gas turbine 9 is driven by exhaust gas coming from the internal combustion engine 1, where the exhaust gas is produced combusting of the air fuel mixture. This combustion normally takes place in the combustion chambers of the internal combustion engine 1 (not shown by the figures). For combustion in mixed charged internal combustion engines a charged air-fuel mixture is fed to the internal combustion engine 1. For combustion in charged internal combustion engines having a fuel port injection a charged air is fed to the internal combustion engine 1, a fuel is separately fed to the internal combustion engine 1 by means of port injection nozzles. When charging air or an air-fuel mixture the air or the air-fuel mixture also is heated by the compression operation. For reducing the temperature of the air or the air-fuel mixture an intercooler 10 is provided.

[0032] The compressor 3 and the intercooler 10 can be bypassed by means of a bypass conduct and a bypass valve 4. This bypass valve 4 is connected by a signal line (presented by the dotted line) with a control unit 5, which is configured to open or closed loop control the bypass valve 4. Furthermore an upstream sensor 6 is provided, which is connected with the control unit 5 by usage of a signal line. The upstream sensor 6 is configured to provide the control unit 5 with a characteristic signal for an upstream pressure (downstream of the compressor 3). Also a downstream sensor 7 is provided which is also connected to the control unit 5 by a signal line. The downstream sensor 7 is configured to provide the control unit 5 with a characteristic signal for a downstream pressure (upstream of the compressor 3). The control unit 5 is configured to determine a pressure difference, from measurement of the downstream sensor 7 and the upstream sensor 6. This pressure difference can be used by the control unit 5 for control an opening degree of the bypass valve 5.

[0033] During a startup of the internal combustion engine 1 the control unit is configured (according to the disclosure) to keep the bypass valve 4 partially open till an engine parameter of the internal combustion engine 1 satisfies a predetermined startup criterion. This startup criterion can be characteristic for a state were the internal combustion engine runs on its own, for example without the help of an auxiliary drive (not shown in the figures). Such a startup criterion couldfor examplebe a threshold value for the above mentioned pressure difference. If the pressure measured by the downstream sensor 7 exceeds the measured pressure of the upstream sensor 6 (taking into account measurement inaccuracy) this can be characteristic for a start of the internal combustion engine (i.e. threshold value 0). It is not absolutely necessary to determine a pressure upstream of the compressor 3 by an upstream sensor 6. It can also be provided that an ambient pressure is stored at the control unit 5, which approximates the upstream pressure of the compressor 3.

[0034] Other examples for a startup criterion would be a predetermined threshold for a rotary speed of the internal combustion engine 1 or the turbo charger 2. For checking if this criterion is fulfilled already provided rotary speed sensors 8 can be used. Another possibility for a startup criterion is that if the time since the start of the operation attains or exceeds a predetermined lower threshold the control unit 5 does not longer keep the bypass valve 4 open (i.e. closes it).

[0035] FIG. 2 shows a second embodiment of an international combustion engine 1, wherein the bypass valve 4 is provided with a check valve 11. The internal combustion engine 1 the turbo charger 2 and the intercooler 10 correspond to the embodiment of FIG. 1. The check valve 11 of FIG. 2 is configured with a spring preloading to be kept open during starting of the internal combustion engine 1, i.e. when the pressure downstream of the compressor 3 is be lower than the upstream pressure because the internal combustion engine 1 sucks air or an air-fuel mixture.

[0036] The third embodiment of an internal combustion engine 1 of FIG. 3 shows an example, wherein further components of the internal combustion engine are bypassed by the bypass valve 4. This embodiment teaches the use of two turbo chargers 2, wherein each turbo charger comprises a compressor, an exhaust gas turbine 9, a connection between the compressor 3 and the exhaust gas turbine 9 by a shaft, a rotational speed sensor 8 for determine a characteristic signal for each turbo charger 2 and an intercooler 10 downstream of each turbo charger 2. The rotational speed sensors 8 are configured to provide the control unit 5 with a signal, which can be used by the control unit 5 for open or closed loop control of the bypass valve 4. This control scheme is similar to the control scheme of FIG. 1. However, in contrast to FIG. 1, FIG. 3 teaches to bypass two turbo chargers 2 and two intercoolers 10 by means of the bypass valve 4 during a starting procedure of the internal combustion engine 1.