JPH04132831A - Intake cooling device of engine with supercharger - Google Patents

Abstract

PURPOSE:To improve transient responsiveness in a low load range and also prevent deterioration of fuel consumption by providing an intercooler changeover valve which opens and closes through interlocking with intake and exhaust changeover valves in an intercooler passage which has a plurality of cores. CONSTITUTION:Only a main turbocharger 7 is operated by closing both intake and exhaust changeover valves 17, 18 in a low speed range, and both intake and exhaust changeover valves 17, 18 are opened in a high speed range so as to operate both main and auxiliary turbochargers 7, 8. Intake air pressure-fed from the respective turbochargers 7, 8 is introduced in a combustion chamber via intercoolers 6a, 6b which have different numbers of cores. An intercooler changeover valve 51 which opens and closes by interlocking with the intake and exhaust changeover valves 17, 18 provided in a flow passage of the intercooler 6b which has a number of the cores. When only the main turbocharger 7 is operated, since the intercooler changeover valve 51 is closed, transient responsiveness in the low load range is improved, and also deterioration of fuel consumption is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a supercharged engine that has a main turbocharger and a sub-turbocharger, and changes the number of activated turbochargers depending on operating conditions, and particularly relates to a supercharged engine that uses an intercooler. The present invention relates to a supercharged engine having an intake air cooling device.

[Prior art] Two turbochargers, a main turbocharger and a sub-turbocharger, are arranged in parallel to the engine body. In the low-speed range, the supercharging operation of the sub-turbocharger is stopped and supercharging is performed only by the main turbocharger, and in the high-speed range, both turbochargers are supercharged. 2. Description of the Related Art A supercharged engine with a so-called two-stage twin-turbo system in which a turbocharger is operated is known.

The configuration of this type of supercharged engine is shown in FIG. 6, for example. A main turbocharger (T/C-1>, 92 and a sub-turbocharger (T/C-2>93) are provided in parallel to the engine body 91. Intake and exhaust systems connected to the sub-turbocharger 93 are provided with an intake switching valve 94 and an exhaust switching valve 95, respectively, and by fully opening both the intake switching valve 94 and the exhaust switching valve 95, only the main turbocharger 92 is supercharged and both are fully opened. Accordingly, the sub-turbocharger 93 is also caused to perform supercharging operation, and two turbochargers can be operated.

In this supercharged engine, each turbocharger 92.
The intake air pressure-fed from 93 is supplied to the engine body 91 via an intercooler 97 that lowers the intake air temperature. Therefore, even if the temperature of the intake air pumped from each turbocharger 92, 93 rises, the forced cooling of the intake air by the intercooler 97 increases the filling efficiency of the intake air, suppresses the occurrence of knocking, and reduces the engine output. The increase is measured.

As an example of the prior art related to the present invention, there is known a two-stage twin-turbo engine in which an intercooler is disposed between the downstream side of the compressor of the sub-turbocharger and the intake confluence section that operates in a high-speed range (Japanese Patent Application Laid-Open No. 1983-1999). 1539
Publication No. 18). Further, a two-stage twin-turbo engine in which a single intercooler is disposed downstream of the main and sub-turbochargers is disclosed in Japanese Patent Laid-Open No. 2-49925.

[Problems to be Solved by the Invention] However, in the conventional two-stage twin interhotor engine, the following problems existed regarding cooling of intake air. The volume of the intercooler is calculated and designed based on the maximum flow rate of intake air, so it is
In a case like the one disclosed in Japanese Patent No. 9925, the volume of the intercooler becomes large for the low load range, and the transient response in the low load range deteriorates. Note that in a low load range, the intake air temperature does not rise much, so there is no need to sufficiently cool the intake air, and overcooling of the intake air actually worsens fuel efficiency.

In addition, in the case of the above-mentioned Japanese Patent Application Laid-Open No. 59-153918, since the intake air does not flow through the intercooler when one turbocharger is used, the intake air is not supplied to the combustion chamber especially in the mid-speed range immediately before switching to the two-turbocharger. There is a problem in that the temperature of the intake air increases and the filling efficiency decreases.

In view of the above problems, the present invention improves transient response in low load ranges, prevents deterioration of fuel efficiency due to overcooling of intake air, and sufficiently cools intake air in medium and high speed ranges to improve charging efficiency. It is an object of the present invention to provide an intake air cooling device for a supercharged engine that can improve the temperature of the engine.

[Means for Solving the Problems] The intake air cooling device for a supercharged engine according to the present invention in accordance with this object has a main turbocharger and a sub-turbocharger, and in a low speed range, an intake switching valve provided in the intake system Both the intake switching valve and the exhaust switching valve installed in the exhaust system are closed to operate only the main turbocharger, and at high speeds, both the intake switching valve and the exhaust switching valve are opened to operate the main turbocharger and the auxiliary turbocharger. In a supercharged engine in which both of the turbochargers are operated and the intake air pressure-fed from each turbocharger is guided to the combustion chamber via the intercooler, the intercooler is composed of two intercoolers with different numbers of cores, and An intercooler switching valve is provided in the flow path of the multiple intercoolers in conjunction with the intake switching valve and exhaust switching valve, and is closed when only the main turbocharger operates and opens when both turbochargers are operated.

[Function] In the intake air cooling system for a supercharged engine configured as described above, in the case of a single turbocharger in which only the main turbocharger operates, the intercooler switching valve closes and air is cooled only through the intercooler with a small number of cores. Since the intake air flows, overcooling of the intake air is eliminated and deterioration of fuel efficiency is prevented. In addition, the intercooler is divided into two parts, and when one turbocharger is used, intake air does not flow into the other intercooler, so the volume of the intercooler available in the low load range can be smaller than with conventional intercoolers, and the transient The response can be improved.

When a two-turbocharger is used, in which both the main and auxiliary turbochargers operate, the intercooler switching valve opens and intake air flows through both intercoolers, making it possible to sufficiently lower the intake air temperature and increasing charging efficiency.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a supercharged engine according to an embodiment of the present invention, and show the case of a six-cylinder engine.

1 and 2, 1 is an engine, 2 is a surge tank, and 3 is an exhaust manifold.

The exhaust manifold 3 is assembled into two groups, a #1 to #3 cylinder group and a #4 to #6 cylinder group, which do not cause exhaust interference, and the assembled portions are communicated with each other by a communication path 3a. 7.8 is a main turbocharger and a sub-turbocharger arranged in parallel with each other. A respective turbine 7a of a turbocharger 7.8.

8a is connected to a joint part of the exhaust manifold 3, and each compressor 7b, 8b is connected to the surge tank 2 via an intercooler 6 and a throttle valve 4.

The main turbocharger 7 is operated from a low engine speed range to a high engine speed range, and the auxiliary turbocharger 8 is stopped in a low engine speed range.

In order to enable operation and stop of both turbochargers 7.8, an exhaust switching valve 17 is provided downstream of the turbine 8a of the auxiliary turbocharger 8, and an intake switching valve 18 is provided downstream of the compressor 8b. Suction/exhaust switching valve 18.17
When both turbochargers are fully open, both turbochargers 7.
8 is activated.

The exhaust passage of the exhaust switching valve 17 section is provided with an exhaust bypass passage 40 that bypasses the exhaust switching valve 17, and the exhaust bypass passage 40 is provided with an exhaust bypass valve 41 that opens and closes the exhaust bypass passage 40. It is being

The exhaust bypass valve 41 is opened and closed by a diaphragm actuator 42, and the exhaust bypass valve 41 is opened by introducing supercharging pressure downstream of the compressor into the diaphragm chamber 42a of the actuator 42. Note that in this embodiment, the exhaust bypass passage 40
connects the upstream part of the exhaust switching valve 17 in the exhaust flow direction and the downstream part of the main turbocharger 7 in the exhaust flow direction; Good too.

In order to smoothly switch from one turbocharger to two turbochargers, the intake passage of the auxiliary turbocharger 8 that is stopped in a low speed range is provided with an intake bypass passage 13 that communicates between the upstream and downstream of the compressor 8b. , an intake bypass valve 33 disposed in the middle of the intake bypass passage 13 is provided. The intake bypass valve 33 is opened and closed by the actuator 10.

The air flow downstream side of the intake bypass passage may be communicated with the intake passage upstream of the compressor of the main turbocharger 7.

In addition, a check valve 12 is provided in the bypass passage that communicates the upstream and downstream sides of the intake switching valve 18, so that even when the intake switching valve 18 is closed, the compressor outlet pressure on the auxiliary turbocharger 8 side is lower than that on the main turbocharger 7 side. This allows air to flow from the upstream side to the downstream side when it becomes large. In the figure, 14 indicates an intake passage on the compressor outlet side, and 15 indicates an intake passage on the compressor inlet side.

The intake passage 15 is connected to an air cleaner 23 via an air flow meter 24. A front pipe 20 forming an exhaust passage is connected to an exhaust muffler 2 via an exhaust gas catalyst 21.
Connected to 2.

The intake switching valve 18 is opened and closed by the actuator 11, and the exhaust switching valve 17 is opened and closed by the diaphragm type actuator 16.
It is designed to be opened and closed by. Note that 9 indicates an actuator that opens and closes the waste gate valve 31. In order to turn off the supercharging pressure or negative pressure that operates the actuators 1o, ii, 16 (selectively switching between supercharging pressure or negative pressure and atmospheric pressure) Four three-way solenoid valves 25, 26, 27, 28 are provided. Switching of the three-way solenoid valves 25, 26, 27, and 28 is performed according to commands from the engine control computer 29. When the three-way solenoid valve 25 is turned ON, the actuator 11 is operated to fully open the intake switching valve 18, and the OF
F operates the actuator 11 to fully open the intake switching valve 18. When the fourth three-way solenoid valve 28 is turned ON, the actuator 16 is operated to fully open the exhaust switching valve 17, and when it is OFF, the actuator 16 is operated so as to fully close the exhaust switching valve 17. When the third three-way solenoid valve 27 is ON, the actuator 10 is actuated to fully close the intake bypass valve 33, and when it is OFF, the actuator 10 is actuated to fully open the intake bypass valve 33. Fifth
When the three-way solenoid valve 32 is ON, the actuator 42 is actuated to open the exhaust bypass valve 41, and when it is OFF, the actuator 42 is actuated to close the exhaust bypass valve 41. Note that 16a indicates a diaphragm chamber of the actuator 16, 10a indicates a diaphragm chamber of the actuator 10, and 11a111b indicates a diaphragm chamber of the actuator 11, respectively.

The intercooler 6 includes a first intercooler 6a and a second intercooler 6b.

The first intercooler 6a has a relatively small number of cores (number of intake air passages) in order to reduce the cooling capacity of intake air. The second intercooler 6b has a larger number of cores than the first intercooler 6a so as to have a large intake air cooling capacity. Note that the smaller the number of cores, the smaller the contact area with the intake air and the lower the cooling capacity, but conversely, the flow resistance of the intake air is small and the flow of the intake air is improved. Furthermore, as the number of cores increases, the contact area with intake air increases and the cooling capacity increases, but conversely, the flow path resistance of intake air increases.

Intercooler switching valves 51 are provided on the upstream and downstream sides of the second intercooler 6b.

Both intercooler switching valves 51 are operated by actuators 52
is connected to. The actuator 52 is connected to the fourth three-way solenoid valve 28 and is configured to operate in conjunction with the actuator 11 that operates the intake switching valve 18 and the actuator 16 that operates the exhaust switching valve 17. The intercooler switching valve 51 is closed when only the main turbocharger 7 operates, and the intake air from the main turbocharger passes only through the first intercooler 6a and is supplied to the combustion chamber of the engine body 1. There is. Further, the intercooler switching valve 51 is opened when both the main turbocharger 7 and the auxiliary turbocharger 8 operate, and the intake air from both turbochargers 7.8 is transferred to the first intercooler 6a and the second intercooler 6b. The fuel is supplied to the combustion chamber of the engine body 1 through the fuel.

The engine control computer 29 is electrically connected to sensors for detecting various operating conditions of the engine, and receives signals from the various sensors. Engine operating condition detection sensors include an intake pipe pressure sensor 30, a throttle opening sensor 5, and an air flow meter 2 as an intake air amount measurement sensor.
4, and an oxygen sensor 19.

The engine control computer 29 includes a central processor unit (CPU) for performing calculations, and a read-only memory (ROM) that is a read-only memory.
, -Random access memory (RAM) for time storage
, input/output interface (I/D interface)
, is equipped with an A/D converter that converts analog signals from various sensors into digital quantities.

Next, the operation of the above-mentioned intake air cooling system for the supercharged engine will be explained with reference to the flowchart shown in FIG.

In FIG. 3, the first to fifth three-way solenoid valves are represented by VSVNo, 'l to VSVNo, 5 and 7, respectively, and the turbocharger is represented by T/C.

In FIG. 3, a valve control routine is entered at step 100, and an intake air amount Q of the engine is read at step 101. The intake air amount is a signal from the air flow meter 24. Next, in step 102, it is determined whether it is a high speed range or a low speed range, that is, a two-turbocharger operating range or a one-turbocharger operating range.

In the illustrated example, for example, if Q is greater than 55001/min, it is determined that two turbocharger operation should be performed, and if Q is less than 5500 Q/min, it is determined that the one turbocharger operation is in the range. However, there is a time delay before the two turbochargers actually operate, so the switch will occur at around 6000Q/min.

If it is determined in step 102 that it is necessary to switch to two-turbocharger operation, the process proceeds to step 103, in which the intake switching valve 18 is opened during the one-turbocharger operation (
(partial loading), the second three-way solenoid valve 26 is turned OFF and the intake switching valve 18 is closed. Next, in step 104, the third three-way solenoid valve 27 is turned on,
The intake pipe pressure (supercharging pressure) downstream of the compressor is introduced into the diaphragm chamber 10a of the actuator 10, and the intake bypass valve 33 is closed.

Next, after the third three-way solenoid valve 27 is turned on, a predetermined time delay, for example, 1 second, necessary to increase the run-up rotation speed of the turbocharger on the inactive side, that is, the auxiliary turbocharger 8, is provided; After one second has elapsed, in step 105, the fourth three-way solenoid valve 28 is turned on, the supercharging pressure downstream of the compressor is introduced into the diaphragm chamber 16a of the actuator 16, and the exhaust switching valve 17 is fully opened. If the compressor pressure of the auxiliary turbocharger 8 becomes higher than the compressor pressure of the main turbocharger 7, the supercharged air of the auxiliary turbocharger 8 is supplied to the engine via the check valve 12. Subsequently, after turning on the fourth three-way solenoid valve 28, after a predetermined period of time, for example, 0.5 seconds, the first
The three-way solenoid valve 25 is turned ON, and the intake pipe pressure downstream of the compressor (
(supercharging pressure) and fully open the intake switching valve 18. In this state, two turbochargers operate (note that when switching to two turbochargers after the above-mentioned predetermined time has passed, the intake air amount is approximately 6000, Q/min, which is the target for good turbine efficiency). ). The process then proceeds to step 117 and returns.

In step 105 described above, the fourth three-way solenoid valve 28
When turned on, the actuator 52 is operated and the intercooler switching valve 51 is fully opened. Therefore, the supercharged air from the main turbocharger 7 and the sub-turbocharger 8 is transferred to the first intercooler 6a and the second intercooler 6b.
It flows to the engine main body 1 side through both. Since the second intercooler 6b has a large number of cores, the amount of heat exchanged with the intake air is large, and the intake air supplied to the engine body 1 side is sufficiently cooled, and the filling efficiency of the intake air is increased. In addition, the second
Since the intercooler 6b has a large number of cores, the flow path resistance increases, but since the intake air also flows through the first intercooler 6a, there is almost no deterioration of the intake air flow as a body of the intercooler 6. .

If it is determined in step 102 that one turbocharger is in the operating range, the process proceeds to step 107, and the first three-way solenoid valve 2
5 is turned OFF to fully open the intake switching valve 18, in step 108 the fourth three-way solenoid valve 28 is turned OFF to close the exhaust switching valve 17, and in step 109 the third three-way solenoid valve 21 is turned OFF to open the intake bypass valve. 33 is fully opened.

Even when the sub-turbocharger 8 rotates, the air sent out by the compressor 8b passes through the intake bypass passage 13 and is transferred to the sub-turbocharger 8 or the main turbocharger 7.
is returned to the compressor inlet side. Next step 1
10 reads the intake pipe pressure PM. In step 111, it is determined whether the intake pipe pressure is greater or less than a predetermined value.

If the intake pipe pressure PM is smaller than, for example, +500a*H9, the process proceeds to step 112, where the fifth three-way solenoid valve 32 is turned OFF, and the diaphragm chamber 42 of the actuator 42 is turned off.
Atmospheric pressure is introduced into a, and the exhaust bypass valve 42 is closed. In this state, the process proceeds to step 113, where it is determined whether the load is light or high. Although the figure shows a case where the intake pipe pressure is used as an example of the load signal, the intake pipe pressure may be replaced by the throttle opening degree or the intake air amount/engine speed.

For example, if the intake pipe pressure PM is less than -1100 #lllHg, it is determined that the load is light, and if it is -100AIIIHg or more, it is determined that the load is high.

In step 108 described above, the fourth three-way solenoid valve 28
When OFF, the actuator 52 operates and the intercooler switching valve 51 is closed. Therefore, the supercharged air from the main turbocharger 7 is transferred to the first intercooler 6.
It flows to the engine main body 1 side only via a. Since the first intercooler 6a has a smaller number of cores than the second intercooler 6b, the amount of heat exchanged with the intake air is also smaller, and overcooling of the intake air supplied to the engine body 1 side is avoided. Deterioration of fuel efficiency is prevented. Note that when the air-fuel ratio is kept constant, increasing the intake air temperature reduces the air density, so the amount of fuel injection can be reduced, and fuel efficiency in a low load range can be improved.

Furthermore, since the first intercooler 6a has a smaller number of cores, the flow path resistance is reduced, so that the flow of intake air is improved.

Furthermore, in this embodiment, since intercooler switching valves 51 are provided on the upstream and downstream sides of the second intercooler 6b, it is possible to reliably prevent intake air from flowing into the second intercooler 6b during low load. The volume of the entire intercooler 6 at low load is reduced by the volume valve of the second intercooler 6b, and the transient response is improved accordingly.

If it is determined that the load is high in step 113, step 1
The process proceeds to step 16, where the second three-way solenoid valve 26 is turned off and the intake switching valve 18 is fully closed, and the process proceeds to step 117, where the process returns. In this state, the intake switching valve 18 is fully open, the exhaust switching valve 17 is fully closed, and the intake bypass valve 33 is fully open, so one turbocharger is activated when the amount of intake air is small, resulting in good boost pressure and torque response. becomes.

If it is determined in step 113 that the load is light, the process proceeds to step 114, where the second three-way solenoid valve 26 is turned on, the negative pressure within the surge tank 2 is guided to the diaphragm 11b of the actuator 11, and the intake switching valve 18 is opened. In this state,
Since the exhaust switching valve 17 is closed, the auxiliary turbocharger 8 does not operate, and only the main turbocharger 7 operates. However, since the intake switching valve 18 in the intake passage 14 is open, the intake passages for two turbochargers are open. In other words, compressor 7b of both turbochargers
, 8b. As a result, a large amount of supercharging air can be supplied to the main body of the engine 1, and acceleration characteristics from low loads are improved. Subsequently, the process advances to step 117 and returns.

If it is determined in step 111 that the intake pipe pressure PM is +500 mHg or more, in step 115 the fifth three-way solenoid valve 32 is turned on and the exhaust bypass valve 41 is opened. The process then proceeds to step 116. In this way, when the supercharging pressure reaches the set pressure (for example, 500aHg) before switching from one turbocharger to two turbocharger operation, the exhaust bypass valve 41 is first opened and the auxiliary turbocharger 8 starts running. The rotation speed is increased, and the transition between turbocharger switching becomes smoother.

As described above, in the high speed range of this supercharged engine, both the intake switching valve 18 and the exhaust switching valve 17 are opened, and the intake bypass valve 33 is closed. As a result, the two turbochargers 7.8 operate for supercharging, a sufficient amount of supercharging air is obtained, and the output is improved. At this time, the boost pressure is +500a
It is controlled by a waste gate valve 31 so as not to exceed mHg.

In a low speed range and under high load, both the intake switching valve 18 and the exhaust switching valve 17 are closed, and the intake bypass valve 33 is opened. As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low speed range is that the supercharging characteristics of a single turbocharger are superior to the supercharging characteristics of a two turbocharger in the low speed range. 1
By using individual turbochargers, boost pressure and torque build up quickly, resulting in a quick response.

In a low speed range and under light load, the intake switching valve 18 is opened while the exhaust switching valve 17 is closed. As a result, the intake passages for two turbochargers are opened while one turbocharger remains driven, and an increase in intake resistance caused by one turbocharger can be eliminated. This makes it possible to further improve the boost pressure rise characteristics and response at the beginning of acceleration from a low load.

When transitioning from a low speed range to a high speed range, that is, when switching from one turbocharger operation to two turbocharger operation, the auxiliary turbocharger 8 is activated by opening the exhaust bypass valve 41 while the exhaust switching valve 17 is closed. It becomes possible to increase the rotational speed and switch the turbocharger more smoothly (with less shock during switching).

In this embodiment, the switching operation of the intercooler switching valve 51 is linked with the operation of the exhaust switching valve 17.
Since the operation of the intake switching valve 18 is performed almost simultaneously with the operation of the exhaust switching valve 17, there is no substantial problem even if the intake switching valve 18 is operated in conjunction with only the exhaust switching valve 17.

Furthermore, by varying the opening amount of the intercooler switching valve 51, fine control of the intake air temperature becomes possible, and engine performance can be roughly improved.

[Effects of the Invention] As explained above, in the intake air cooling device for a supercharged engine according to the present invention, the intercooler is composed of two intercoolers with different numbers of cores, and the flow path of the intercooler with a large number of cores is We installed an intercooler switching valve that works in conjunction with the intake switching valve and exhaust switching valve, and closes when only the main turbocharger operates and opens when both turbochargers operate, thereby reducing transient response in the low load range. In addition to improving fuel efficiency, it is also possible to prevent deterioration in fuel efficiency due to supercooling of intake air.

In addition, in the medium speed range just before switching to the dual turbocharger, one intercooler cools the intake air appropriately, and in the high speed range, both intercoolers can sufficiently cool the intake air, increasing the intake air filling efficiency. be able to.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a supercharged engine according to an embodiment of the present invention, Fig. 2 is a more specific system diagram of the supercharged engine shown in Fig. 1, and Fig. 3 is a system diagram of the supercharged engine shown in Fig. 1. A flowchart showing the control procedure of the device, FIG. 4 is a relationship diagram showing the relationship between the number of cores and the amount of cooling in the intercoolers shown in FIGS. 1 and 2, and FIG. FIG. 6 is a relationship diagram showing the relationship between air volume and cooling amount, and is a schematic system diagram of a conventional supercharged engine. 1... Engine 2... Surge tank 3... Exhaust manifold 4... Throttle valve 5... Throttle opening sensor 6... ...Intercooler 6a...First intercooler 6b...Second intercooler 7...Main turbocharger 8...Sub-turbocharger 13... ... Intake bypass passage 17 ... Exhaust switching valve 18 ... Intake switching valve 51 ... Intercooler switching valve

Claims (1)

[Claims] 1. It has a main turbocharger and a sub-turbocharger, and in the low speed range, both the intake switching valve installed in the intake system and the exhaust switching valve installed in the exhaust system are closed and only the main turbocharger is operated, and in the high speed range In this case, both the intake switching valve and the exhaust switching valve are opened to operate both the main turbocharger and the auxiliary turbocharger, and the intake air that is pressure-fed from each turbocharger is guided to the combustion chamber via the intercooler. In a supercharged engine, the intercooler is composed of two intercoolers with different numbers of cores, and when only the main turbocharger operates in conjunction with the intake switching valve and the exhaust switching valve, the intercooler has a flow path of the intercooler with a large number of cores. An intake air cooling device for a supercharged engine, characterized in that it is provided with an intercooler switching valve that is closed and opened when both turbochargers operate.