JP3783527B2 - Two-stage turbocharging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-stage supercharging system.
[0002]
[Prior art]
The two-stage turbocharging system includes a high-pressure turbine and a low-pressure turbine arranged in series in the exhaust path of the diesel engine, and a high-pressure compressor and a low-pressure stage arranged in series in the intake path of the diesel engine and driven by each turbine, respectively. The thing provided with the compressor is known. In such a two-stage supercharging system, the final supercharging pressure is determined by two compressors. In particular, it is important to accurately grasp and control the work amount of the high-pressure stage compressor.
[0003]
Therefore, a device for controlling the work of the high-pressure compressor has been developed by connecting a bypass passage to the exhaust passage so as to bypass the high-pressure turbine and adjusting the opening of the exhaust bypass valve provided in the bypass passage. (Japanese Utility Model Publication No. 59-1833, etc.). However, this device detects the final supercharging pressure by a pressure sensor provided on the downstream side of the high-pressure compressor, and it is impossible to accurately grasp the work amount (pressure ratio) of only the high-pressure compressor. Can not.
[0004]
That is, the final supercharging pressure obtained from the pressure sensor provided downstream of the high-pressure stage compressor is affected not only by the work amount of the high-pressure stage compressor but also by the work amount of the low-pressure stage compressor. It is not possible to accurately grasp the work amount (pressure ratio) of only the high-pressure compressor based on the final supercharging pressure. That is, the above apparatus does not have a technical idea of accurately grasping the work amount (pressure ratio) of the high-pressure stage compressor and accurately controlling the work amount (pressure ratio) of the high-pressure stage compressor.
[0005]
In addition, as a normal one-stage turbocharging system, a turbocharger is provided in the intake and exhaust passages of a diesel engine, a bypass passage is connected to bypass the turbine in the exhaust passage, and an exhaust bypass valve is provided in the bypass passage. In this system, the upstream and downstream pressures of the compressor are detected, the intake pressure ratio of the compressor is calculated from the detected values, and the bypass valve is opened when the intake pressure ratio breaks the surge line of the compressor. Controls have been developed (Japanese Utility Model Publication No. 61-95938).
[0006]
However, in this system, when the vehicle travels over a 4000m class super high altitude, the compressor exhaust line becomes a surge line due to the turbine exhaust pressure becoming relatively low and the turbine speed increasing. The purpose is to avoid the approach, and it is not intended to accurately grasp and control the work amount of the high-pressure compressor of the two-stage supercharging system. That is, the above system realizes high-pressure supercharging by two-stage supercharging, accurately grasps the work amount of the high-pressure compressor, accurately controls the maximum efficiency, and avoids deterioration of fuel consumption. It has nothing to do with it.
[0007]
[Problems to be solved by the invention]
In short, a conventional two-stage turbocharging system has not been developed that accurately grasps the work amount (pressure ratio) of a high-pressure compressor and accurately controls the two-stage turbocharging system.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a high-pressure stage turbine and a low-pressure stage turbine arranged in series in an exhaust path of a diesel engine, and a high-pressure stage arranged in series in the intake path of the engine and driven by each turbine. A compressor, a low-pressure compressor, a bypass passage connected to the exhaust passage so as to bypass the high-pressure turbine, an exhaust bypass valve provided in the bypass passage, and a control for controlling an opening degree of the exhaust bypass valve A basic opening degree setting means for setting a basic opening degree of the exhaust bypass valve based on at least the engine speed, and based on the operating state of the engine. Based on the target pressure ratio setting means for setting the target pressure ratio of the high-pressure stage compressor and the pressure upstream and downstream of the high-pressure stage compressor It has a measurement pressure ratio detection means for detecting an actual measurement pressure ratio, and a correction means for comparing the measurement pressure ratio with the target pressure ratio and correcting the basic opening of the exhaust bypass valve so that they match. is there.
[0009]
The basic opening degree setting means sets the basic opening degree of the exhaust bypass valve so that the high-pressure compressor is operated along a desired operating line based on the engine speed and the load state. Also good.
[0010]
The target pressure ratio setting means may set the target pressure ratio of the high-pressure compressor based on the engine speed and the load state.
[0011]
In addition, the control unit includes a measurement correction flow rate detection unit that detects an actual measurement correction flow rate of the high-pressure stage compressor, a target correction flow rate setting unit that sets a target correction flow rate of the high-pressure stage compressor based on the engine operating state, and a measurement An abnormality determining unit that determines an abnormality when the corrected flow rate does not match the target corrected flow rate may be further provided.
[0012]
The measurement correction flow rate detecting means includes an air flow sensor provided in the intake path, a pressure sensor and a temperature sensor provided on the upstream side of the high-pressure compressor, and a measurement correction flow rate based on detection values of these sensors. It may be provided with a calculation means for calculating.
[0013]
In addition, the control unit includes an operation state determination unit that determines an operation state of the high-pressure stage compressor based on the measured pressure ratio and the measured corrected flow rate of the high-pressure stage compressor, and the high-pressure stage compressor is operated in the surge region or the overrev region. It may further comprise emergency means for opening the exhaust bypass valve when it is determined that.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is a diagram showing an outline of a two-stage supercharging system 1 according to the present embodiment.
[0016]
As shown in the drawing, a high-pressure turbine 4 and a low-pressure turbine 5 are provided in series in the exhaust passage 3 of the diesel engine 2 at intervals in the flow direction of the exhaust gas. 6, a high-pressure compressor 7 and a low-pressure compressor 8 are connected in series with an interval in the flow direction of the intake air. The high-pressure stage compressor 7 and the high-pressure stage turbine 4 are connected by a rotating shaft 10 to constitute a high-pressure stage turbo 11, and the low-pressure stage compressor 8 and the low-pressure stage turbine 5 are connected by a rotating shaft 12 to constitute a low-pressure stage turbo 13. To do.
[0017]
An intercooler 14 is interposed in the intake passage 6 between the low-pressure compressor 8 and the high-pressure compressor 7, and an aftercooler 15 is provided in the intake passage 6 between the high-pressure compressor 7 and the engine 2. It is installed. The intercooler 14 and the aftercooler 15 are for cooling the intake air whose temperature has been increased by compression, but are not necessarily required for the configuration of the invention, and either one or both may be omitted.
[0018]
The exhaust path 3 is provided with a bypass passage 16 connected to the upstream side and the downstream side of the high-pressure turbine 4 so as to bypass the high-pressure turbine 4. An exhaust bypass valve 17 is interposed in the bypass passage 16. The opening degree of the exhaust bypass valve 17 is adjusted by an actuator 18, and the flow rate of exhaust gas flowing in the bypass passage 16 is adjusted (0 to 100%). The operation of the actuator 18 is controlled by the control unit 19.
[0019]
An air flow sensor 20 that detects an intake air flow rate M is provided in the intake path 6 on the upstream side of the low-pressure compressor 8. The intake path 6 between the intercooler 14 and the high pressure compressor 7 is provided with a first pressure sensor 21 that detects the intake pressure P1 of the high pressure compressor 7 and a temperature sensor 22 that detects the intake air temperature T1. It has been. In addition, a second pressure sensor 23 that detects a discharge pressure P <b> 2 of the high-pressure compressor 7 is provided in the intake path 6 between the high-pressure compressor 7 and the aftercooler 15.
[0020]
Further, the engine 2 is provided with a rotation sensor 24 for detecting the rotation speed RPM of the engine 2 and a load sensor 25 for detecting the load LD. The air flow sensor 20, the first pressure sensor 21, the second pressure sensor 23, the temperature sensor 22, the rotation sensor 24, and the load sensor 25 are connected to the control unit 19, and outputs of the sensors 20 to 25 are controlled by the control unit 19. To be sent to. The control unit 19 controls the actuator 18 according to the output values sent from the sensors 20 to 25, and controls the opening degree of the exhaust bypass valve 17 as described later.
[0021]
A control flow of the control unit 19 will be described with reference to FIGS.
[0022]
After the start, in step 1, the current engine speed RPM is detected by the rotation sensor 24, and the current engine load LD is detected by the load sensor 25. The detected current engine speed RPM and current load LD are sent to the control unit 19.
[0023]
Next, at step 2, the current engine speed RPM and load LD detected at step 1 are input to the bypass valve opening degree map M1 shown in FIG. Is determined. That is, the control unit 19 includes basic opening setting means for setting the basic opening of the exhaust bypass valve 17 based on at least the engine speed RPM.
[0024]
The basic opening degree setting means includes a bypass valve opening degree map M1 for setting the basic opening degree of the exhaust bypass valve 17 on the basis of the rotational speed RPM of the engine 2 and the state of the load LD. By controlling the basic opening degree of the exhaust bypass valve 17 by this bypass valve opening degree map M1, the amount of exhaust gas passing through the high pressure turbine 4 is controlled, and the high pressure stage compressor 7 is operated in the operating state of the engine 2 (rpm RPM, It is possible to operate along a desired operation line (for example, an operation line set in a high efficiency region where fuel efficiency is good) determined in advance according to the load LD).
[0025]
In the present embodiment, as shown in the bypass valve opening map M1 in FIG. 4, the basic opening of the bypass valve 17 increases as the rotation speed RPM increases and the load LD increases, and the rotation speed RPM decreases and the load LD decreases. The basic characteristics are set so as to decrease as the value decreases. Thereby, while avoiding excessive supercharging at the time of high rotation and high load, the supercharging pressure at the time of low rotation and low load is ensured.
[0026]
Next, at step 3, the current engine speed RPM and load LD detected at step 1 are input to the target pressure ratio / target corrected flow map M2 shown in FIG. A target pressure ratio PR _TARGET and a target correction flow rate Mc _TARGET for the high-pressure compressor 7 are determined. That is, the control unit 19 includes target pressure ratio setting means for setting the target pressure ratio PR _TARGET of the high pressure compressor 7 based on the operating state of the engine 2 (engine speed RPM, load LD), and the high pressure compressor 7. And target correction flow rate setting means for setting the target correction flow rate Mc _TARGET .
[0027]
The target pressure ratio setting means and the target correction flow rate setting means include a target pressure ratio / target correction flow rate map M2. The target pressure ratio PR _TARGET and the target correction flow rate Mc _TARGET written in this map M2 are set to a predetermined desired value for the high-pressure compressor 7 in accordance with changes in the operating state of the engine 2 (rotation speed RPM, load LD). It is set to a value that is traced along an operation line (for example, an operation line set in a high efficiency region where fuel efficiency is good).
[0028]
In the present embodiment, as shown in FIG. 5, the target pressure ratio / target corrected flow rate map M2 increases when the target pressure ratio PR _TARGET increases as the engine speed RPM increases up to about 1000 RPM and becomes about 1000 RPM or more. The basic characteristics are set so as to lower the target pressure ratio PR _TARGET . Thereby, the supercharging at the time of high rotation is avoided, ensuring the supercharging pressure in a low and medium speed rotation area.
[0029]
Next, at step 4, the first and second pressure sensors 21, 23 detect the upstream pressure P1 and the downstream pressure P2 of the high-pressure compressor 7, and the control unit 19 detects the current measured pressure ratio. Calculate PR = P2 / P1. That is, the control unit 19 has a measurement pressure ratio detection unit that detects the actual measurement pressure ratio PR based on the pressures P1 and P2 upstream and downstream of the high-pressure compressor 7. The measurement pressure ratio detection means includes first and second pressure sensors 21 and 23.
[0030]
Next, in step 5, the measured pressure ratio PR and the target pressure ratio PR _TARGET are compared in the control unit 19. Then, if the measured pressure ratio PR> the target pressure ratio PR _TARGET , the control unit 19 sends a command for increasing the opening degree of the exhaust bypass valve 17 to the actuator 18 in step 6, and if the measured pressure ratio PR <the target pressure ratio PR _TARGET. In step 7, a command to reduce the opening degree of the exhaust bypass valve 17 is sent to the actuator 18. After passing through step 6 or step 7, it returns to step 4 again.
[0031]
Then, the pressures P1 and P2 are detected again at step 4, and the measured pressure ratio PR = P2 / P1 is calculated. At step 5, the measured pressure ratio PR and the target pressure ratio PR _TARGET are compared. This circulation is performed in step 5 until the measured pressure ratio PR matches the target pressure ratio PR _TARGET . By this feedback control, the basic opening degree of the exhaust bypass valve 17 determined in step 2 is corrected so that the measured pressure ratio PR and the target pressure ratio PR _TARGET coincide. That is, the control unit 19 has a correcting unit that compares the measured pressure ratio PR and the target pressure ratio PR _TARGET and corrects the basic opening of the exhaust bypass valve 17 so that they match.
[0032]
The correcting means is composed of steps 4-7. By controlling the opening degree of the exhaust bypass valve 17 by this correcting means, the pressure ratio (measured pressure ratio PR) of the high-pressure compressor 7 matches the operating state of the engine 2 (rotation speed RPM, load LD) at that time. (Target pressure ratio PR _TARGET ). As a result, the high-pressure stage compressor 7 has a desired operating line (for example, an operating line set in a high-efficiency range where fuel efficiency is good) determined in advance according to the operating state of the engine 2 (rotation speed RPM, load LD). Will be driven along.
[0033]
Next, when the measured pressure ratio PR = target pressure ratio PR _TARGET in step 5, the process proceeds to step 8. In step 8, the intake air flow rate M is detected by the air flow sensor 20, and the air temperature T 1 is detected by the temperature sensor 22. Then, the control unit 19 calculates the current measured correction flow rate Mc by Mc = (M × (T1 / Tr) ^0.5 ) / (P1 / Pr).
[0034]
Here, Tr is a reference temperature for correction and 20 ° C. (293 K) is used, and Pr is a reference pressure for correction and atmospheric pressure (1.013 BAR) is used. That is, the control unit 19 includes measurement correction flow rate setting means (step 8) for detecting the actual measurement correction flow rate Mc of the high-pressure compressor 7. The measurement correction flow rate setting means includes an air flow sensor 20, a first pressure sensor 21, and a temperature sensor 22. Then, go to Step 9.
[0035]
In step 9, the measured corrected flow rate Mc calculated in step 8 and the target corrected flow rate Mc _TARGET obtained from the map M <_b> 2 in step 3 are compared in the control unit 19. Then, if the measurement correction flow rate Mc = target correction flow rate Mc _TARGET , the process returns to step 10 and returns to the start. If the measurement correction flow rate Mc = target correction flow rate Mc _TARGET does not _{exist, the process} proceeds to step 11 and a warning light (warning buzzer or the like) is activated.
[0036]
That is, when the measured pressure ratio PR matches the target pressure ratio PR _TARGET in step 5, it is confirmed in step 9 whether or not the measured corrected flow rate Mc matches the target corrected flow rate Mc _TARGET. If it does not coincide with the target correction flow rate Mc _TARGET , it is considered that there is some abnormality, so that a warning light (warning buzzer or the like) is activated in step 11. That is, the control unit 19 includes abnormality determining means (steps 9 and 11) that determines that an abnormality occurs when the measured corrected flow rate Mc does not match the target corrected flow rate Mc _TARGET .
[0037]
The reason why the measurement correction flow rate Mc does not reach the target correction flow rate Mc _TARGET even when the measurement pressure ratio PR reaches the target pressure ratio PR _TARGET is, for example, when the low-pressure compressor 8 is not operating properly due to an abnormality. In addition, there may be a case where the intake path 6 is clogged or a pipe is broken (gas is lost). Here, if feedback control is performed with the pressure ratio PR as shown in steps 4 to 7 of the present embodiment, only the pressure ratio PR is obtained by the opening degree control of the exhaust bypass valve 17 even if there is an abnormality as described above. There may be a case where it becomes a normal value, and there is a possibility that an abnormality cannot be determined. Therefore, it is extremely useful to determine an abnormality based on the corrected flow rate Mc.
[0038]
The basic opening degree of the exhaust bypass valve 17 may be corrected based on the comparison result between the calculated measured corrected flow rate Mc and the target corrected flow rate Mc _TARGET obtained from the map M2, but in the present embodiment, the step is corrected. The comparison result between the measured pressure ratio PR calculated as shown in FIG. 5 and the target pressure ratio PR _TARGET obtained from the map M2 is prioritized. That is, although step 5 and step 9 may be interchanged, in this embodiment, the pressure ratio PR is prioritized over the corrected flow rate Mc.
[0039]
This is because (1) the calculation of the corrected flow rate Mc is complicated and requires many sensors (air flow sensor 20, first pressure sensor 21, temperature sensor 22) as shown in step 8, whereas The calculation of the pressure ratio PR is because the calculation is simple and the number of sensors is small as shown in Step 4 (first and second pressure sensors 21, 23). In addition, (2) with the corrected flow rate Mc, it is difficult to specify the operating point of the high-pressure stage compressor 7 and the direction of the control cannot be easily determined. This is because the point can be specified and the direction of the control can be clearly defined. This difference occurs because the pressure ratio PR = P2 / P1 is the pressure ratio itself of the high-pressure compressor 7 whereas the corrected flow rate Mc is strongly influenced by the operation of the low-pressure compressor 8.
[0040]
After step 11, the process proceeds to step 12. In step 12, the measured corrected flow rate Mc and the measured pressure ratio PR are input to the operating region restriction map M3 shown in FIG. 6 written in the control unit 19, and the current operating state of the high pressure compressor 7 is read. Then, it is determined whether the region is in the surge region, the appropriate region, or the overrev region. If it is the appropriate region, the process returns to the start in step 14, and if it is the surge region or the overrev region, the opening degree of the exhaust bypass valve 17 is fully opened in step 15, and the process returns to start in step 16.
[0041]
Thus, when the pressure ratio PR reaches the target value PR _TARGET in step 5, if the flow rate Mc does not reach the target value Mc _TARGET in step 9, it is considered that there is some abnormality as described above, and the warning light (Warning buzzer or the like) is then activated, but when it is determined in step 13 that the abnormal state is that the high-pressure compressor 7 is in the surge region or the overrev region, the exhaust bypass valve 17 is fully opened, The high-pressure compressor 7 operated in the above is returned to an appropriate region, and the high-pressure compressor 7 is protected.
[0042]
That is, the control unit 19 includes an operating state determination unit that determines the operating state of the high pressure compressor 7 based on the measured pressure ratio PR and the measured corrected flow rate Mc of the high pressure compressor 7, and the high pressure compressor 7 has a surge region or an overrev region. Emergency means for opening the exhaust bypass valve 17 when it is determined that the engine is operating. The operating state judging means has an operation region restriction map M3 shown in FIG. 6, and the emergency means has steps 13 and 15.
[0043]
As described above, in the present embodiment, in the two-stage turbocharging system 1, the target pressure ratio PR _TARGET of the high-pressure compressor 7 is set from the rotational speed RPM of the engine 2 and the load LD, and this pressure ratio PR _The exhaust bypass valve 17 is always controlled so as to be _TARGET . As a result, the high-pressure compressor 7 can be accurately operated along a desired operating line. For example, the high-pressure compressor 8 can be accurately operated along an operating line with good fuel efficiency.
[0044]
【The invention's effect】
As described above, according to the present invention, the following effects can be exhibited.
[0045]
(1) Since the pressure ratio of the high-pressure stage compressor can be accurately grasped and controlled, the high-pressure stage compressor can be accurately operated along a desired operating line. Therefore, for example, the high-pressure compressor can be operated along an operating line with good fuel efficiency.
[0046]
(2) Diagnose abnormalities in the intake and exhaust systems of turbo and engine.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a two-stage supercharging system according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a control flow of the two-stage supercharging system.
FIG. 3 is a flowchart showing the continuation of the control flow.
FIG. 4 is a bypass valve opening degree map used in the control flow.
FIG. 5 is a target pressure ratio / target corrected flow rate map used in the control flow.
FIG. 6 is an operation region restriction map used in the control flow.
[Explanation of symbols]
1 Two-stage turbocharging system 2 Diesel engine 3 Exhaust path 4 High-pressure stage turbine 5 Low-pressure stage turbine 6 Intake path 7 High-pressure stage compressor 8 Low-pressure stage compressor 16 Bypass path 17 Exhaust bypass valve 19 Control unit PR Measurement pressure ratio PR _TARGET Target pressure ratio Mc Measurement correction flow rate Mc _TARGET target correction flow rate P1 Pressure P2 Pressure

Claims (6)

A high-pressure turbine and a low-pressure turbine arranged in series in the exhaust path of the diesel engine; a high-pressure compressor and a low-pressure compressor arranged in series in the intake path of the engine and driven by each turbine; and the exhaust pathway A two-stage turbocharging system comprising: a bypass passage connected to bypass the high-pressure turbine; an exhaust bypass valve provided in the bypass passage; and a control unit for controlling the opening degree of the exhaust bypass valve The control unit sets basic opening setting means for setting a basic opening of the exhaust bypass valve based on at least the engine speed, and sets a target pressure ratio of the high-pressure compressor based on the operating state of the engine. Target pressure ratio setting means and a measurement that detects the actual measured pressure ratio based on the pressure upstream and downstream of the high-pressure stage compressor. A two-stage excess characterized by comprising pressure ratio detection means and correction means for comparing the measured pressure ratio with the target pressure ratio and correcting the basic opening of the exhaust bypass valve so that they match. Supply system. 2. The basic opening degree setting means sets the basic opening degree of the exhaust bypass valve so that the high-pressure compressor is operated along a desired operating line based on the engine speed and the load state. The two-stage turbocharging system described. 3. The two-stage turbocharging system according to claim 1, wherein the target pressure ratio setting means sets the target pressure ratio of the high-pressure compressor based on the engine speed and the load state. The control unit includes measurement correction flow rate detection means for detecting an actual measurement correction flow rate of the high pressure compressor, target correction flow setting means for setting the target correction flow rate of the high pressure compressor based on the engine operating state, and measurement correction flow rate The two-stage supercharging system according to any one of claims 1 to 3, further comprising abnormality determining means for determining that an abnormality occurs when the value does not match the target correction flow rate. The measurement correction flow rate detection means calculates the measurement correction flow rate based on the air flow sensor provided in the intake path, the pressure sensor and the temperature sensor provided on the upstream side of the high-pressure stage compressor, and the detection values of these sensors, respectively. The two-stage supercharging system according to claim 4, further comprising an arithmetic means for performing the operation. The control unit determines an operation state determination unit that determines an operation state of the high-pressure stage compressor based on the measured pressure ratio and the measured corrected flow rate of the high-pressure stage compressor, and determines that the high-pressure stage compressor is operated in the surge region or the overrev region. 6. The two-stage supercharging system according to claim 1, further comprising emergency means for opening the exhaust bypass valve when the operation is performed.

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