JPH0417725A - Supercharged pressure control device of two stage supercharged internal combustion engine - Google Patents

Abstract

PURPOSE:To regulate the torque down in the high engine speed area by controlling an waste gate valve by the pressure of the down stream of an inter cooler. CONSTITUTION:A high pressure stage turbocharger 18 and low pressure stage turbocharger 17 are arranged in series in the gas flow direction, and an exhaust change over valve 38 is provided in an exhaust air by-path 36, which makes detour around the high pressure stage turbocharger 18, and a waste gate valve 32 is provided in an exhaust by-path 30, which makes detour around the low pressure stage turbocharger 17. The waste gate valve 32 is controlled by the pressure of the down stream of an intercooler 29 after completely releasing the exhaust change over valve 38. Since owing to this constitution, the down stream pressure of the intercooler 29 is substantially lowered based on a passage resistance on the high engine speed area, the manifold pressure on the high engine speed area can be raised resulting in the rise of torque the higher.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boost pressure control device for a two-stage supercharged internal combustion engine.

[Prior art]

A two-stage supercharged internal combustion engine in which a large turbocharger and a small turbocharger are arranged in series in the gas flow direction is known (see Japanese Patent Application No. 63-250928).

An exhaust gas switching valve is provided in a bypass passage that bypasses a small turbocharger, and a wastegate valve is provided in a bypass passage that bypasses a large turbocharger. The exhaust switching valve is controlled by the compressor outlet pressure of the small turbocharger, and the wastegate valve is controlled by the compressor outlet pressure of the large turbocharger. When the engine is running at low speeds before the large turbocharger has finished starting up, the exhaust switching valve is closed and supercharging is performed by the small turbocharger. Upon completion of startup of the large turbocharger, the exhaust switching valve is opened and the operation of the small turbocharger is stopped.

[Problem to be solved by the invention]

When the exhaust switching valve is closed, supercharging is carried out by the shared use of the small turbocharger and the large turbocharger (two-stage supercharging region), and after the exhaust switching valve is opened, only the large turbocharger is involved in supercharging (1 stage supercharging area). When the supercharging pressure reaches the target value in the second-stage supercharging region, the exhaust switching valve gradually starts to open, and at the switching point, the exhaust switching valve opens all at once. Thereafter, the opening of the wastegate valve is controlled by the compressor outlet pressure of the large turbocharger.

The supercharging pressure is maintained at an almost constant value throughout the second-stage supercharging and the first-stage supercharging.

In the case of this conventional system, there is a problem in that torque decreases at high speeds when supercharging is controlled by the wastegate valve. In other words, the wastegate valve is controlled by the pressure downstream of the large turbocharger, but since an intercooler is placed downstream of the large turbocharger, there is a pressure drop due to the intercooler, and the intake pipe pressure when entering the engine is reduced by that amount. (pressure at the intake manifold) drops,
It is unavoidable that the engine torque decreases in response to the drop in intake pipe pressure.

The object of the present invention is to suppress a reduction in torque in a high engine speed range where boost pressure is controlled by a wastegate valve.

[Means to solve the problem]

According to this invention, a large turbocharger and a small turbocharger are arranged in series in the gas flow direction, an exhaust switching valve is provided in a bypass passage that bypasses the small turbocharger, and a waste gate is provided in the bypass passage that bypasses the large turbocharger. In a two-stage supercharged internal combustion engine with a valve and an intercooler located downstream of the compressor of a small turbocharger, the exhaust switching valve is controlled by the compressor outlet pressure of the small turbocharger, and the wastegate valve is controlled by the pressure downstream of the intercooler. A supercharging pressure control device for a two-stage supercharged internal combustion engine is provided.

[Effect]

The exhaust switching valve is controlled according to the compressor outlet pressure of the small turbocharger. The outlet pressure of a small turbocharger is large when the engine speed is low and small when the engine speed is high. Therefore, by controlling the exhaust switching valve using the compressor outlet pressure, it is possible to obtain intake manifold pressure that increases as the engine speed increases, and the torque generated by the exhaust pressure decrease when the exhaust switching valve switches from closed to open. Even if there is an increase, it can be balanced with this increase and smooth torque changes can be obtained.

Further, after the exhaust gas switching valve is completely opened, the wastegate valve is controlled by the downstream pressure of the intercooler, and the downstream pressure of the intercooler is greatly reduced based on the high-speed side passage resistance of the engine. Therefore, by controlling the wastegate' valve using the intercooler downstream pressure, it is possible to increase the intake manifold pressure on the high engine speed side, which increases the torque accordingly, eliminating the torque reduction on the high speed side in the conventional technology. I can do it.

〔Example〕

FIG. 1 shows the entire high-density supercharged gasoline internal combustion engine of the present invention, where 10 is the engine body, the intake pipe 12
and the exhaust pipe 14 are connected. large turbo charge 17
and a small turbocharger 18 are arranged in series. The large-sized turbo charger 17 is composed of a compressor 20, a turbine 22, and a rotating shaft 24. The small turbocharger 18 includes a compressor 26, a turbine 28,
It is composed of a rotating shaft 25. In the intake pipe 12, the compressor 20 of the large turbocharger 17 and the compressor 26 of the small turbocharger I8 are arranged in this order in the flow direction of intake air, and an intercooler 29 is arranged downstream thereof. In the exhaust pipe, the turbine 28 of the small turbocharger 18 and the turbine 22 of the large turbocharger 18 are arranged in this order in the flow direction of exhaust gas.

A first exhaust bypass passage 30 is connected to the exhaust pipe, bypassing the turbine of the large turbocharger 17, and a wastegate valve 32, which is a swing door type valve, is arranged in the first exhaust bypass passage 3o.

Wastegate valve 32 is connected to a diaphragm actuator 34 whose diaphragm 34g is connected to bypass valve 32. Bypass valve 32 has spring 34b
Normally, the wastegate valve 32 is urged to close by the pressure applied to the diaphragm 34a, but the wastegate valve 32 is opened against the force of the spring 34b.

A second exhaust bypass passage 36 is provided to bypass the turbine 28 of the small turbocharger 17, and an exhaust switching valve 38 as a butterfly valve is provided in this second bypass passage 36. The exhaust switching valve 38 is connected to its actuator 40, and the actuator 40 is configured as a one-stage diaphragm mechanism.

As will be described later, this actuator 40 closes the exhaust switching valve 38 until the large turbocharger 17 exerts its full supercharging capacity, and switches the exhaust switching valve 38 when the large turbocharger 17 reaches its full supercharging capacity. It operates to cause valve 38 to open rapidly. The exhaust switching valve 40 includes a diaphragm 40a and a spring 40b. spring 4
A first diaphragm chamber 40c is formed on the side surface of the diaphragm 40a facing the spring 40b, and a second diaphragm chamber 40d is formed on the spring 40b side of the diaphragm 40a.

An intake bypass passage 44 that bypasses the compressor 26 of the small turbocharger 18 is provided, and an intake bypass valve 46 is disposed in the intake bypass passage 44. Switching valve 4
6 is connected to a diaphragm actuator 48, and the operation of the intake bypass valve 46 is controlled by the pressure applied to the diaphragm 48a. This intake bypass valve 46 is connected to the intake bypass passage 4 in the operating range of the small turbocharger 18 where the startup of the large turbocharger 17 is not completed.
4 is closed, but after that is completed, supercharging pressure acts on the diaphragm 48H from below, and the intake bypass valve 46 is opened.

As a mechanism for gradually opening the exhaust switching valve during second-stage supercharging and opening it all at once when transitioning to first-stage supercharging, a solenoid valve 50 (VSVI) and a pressure regulator 52 are installed in the second diaphragm chamber. 40d and the supercharging pressure extraction port 54 of the intake pipe 12. The solenoid valve 50 (vSvl) is switched between a position where reduced supercharging pressure is introduced into the second diaphragm chamber (50d) and a position where atmospheric pressure is introduced. The pressure regulator 52 has a diaphragm 52a and a spring 52b, the spring 52b side of the diaphragm 52a is open to the atmosphere, and the diaphragm chamber 52c formed on the opposite side of the diaphragm 52a from the spring 52b is connected to the actuator with the solenoid valve 50 in between. 40 and is connected to conduit 56 on the opposite side. A valve body 52d is provided on the diaphragm 52a, and the atmosphere introduction port 52e is opened and closed by the valve body 52d. That is, when the pressure in the diaphragm chamber 52c becomes larger than the set force of the spring 52b, the valve element 52d opens against the spring 52b, and as a result, when the pressure in the diaphragm chamber 52c decreases, the spring 52b causes the diaphragm 52a to close. It will be done. By repeating such valve opening and closing, the pressure in the diaphragm chamber 52a is controlled to a constant pressure according to the set force of the spring 52b. Therefore, the pressure in the second diaphragm chamber 40d of the actuator 40 connected to the pressure regulator 52 is controlled to a constant pressure that is lower than the pressure in the port 54.

The first diaphragm chamber 40c is constantly connected to the supercharging pressure outlet port 54 via a conduit 56. On the other hand, the solenoid valve 60 (
VSV2) is the actuator 48 of the intake bypass valve 46
This solenoid valve 60 (VSV2) is provided below the diaphragm 48a for pressure control, and this solenoid valve 60 (VSV2) is located at a position where atmospheric pressure is introduced below the diaphragm 48a, and at a position where the supercharging pressure at the compressor outlet 61 of the small turbocharger 18 is controlled. It changes depending on the position where it is introduced.

The control circuit 72 generates drive signals for the vignetting and the solenoid valves 50 (VSVI) and 60 (VSV2) for supercharging control in the present invention. The control circuit 72 is connected to a sensor necessary for supercharging pressure control. First, a first pressure sensor 78 is provided to detect the outlet pressure P of the compressor 20 of the large turbocharger 17, and a second pressure sensor 80 is provided to detect the outlet pressure P2 of the compressor 26 of the small turbocharger 18. provided.

The operation of the control circuit 72 is explained in FIG. 2 at step 10.
If it is 0, it is determined whether or not it is in the 1st stage supercharging region. 1 from 2nd stage supercharging area
Switching to the stage supercharging region occurs at the point NE=NE2 in FIG. Compressor outlet pressure P
This can be determined based on R and the compressor outlet pressure P of the large turbocharger 17. Step 1 in the 2-stage supercharging region where the large turbocharger has not yet completed startup.
02, the solenoid valve 50 (VS
VI) is turned off. Therefore, the actuator 40
The reduced supercharging pressure is introduced into the second diaphragm chamber 40d. On the other hand, the supercharging pressure is directly introduced into the first diaphragm chamber 40c. Therefore, the force that urges the exhaust switching valve 38 in the closing direction is based on the spring force + the reduced pressure in the second diaphragm chamber 40d.
This is the force applied in the right direction in the figure a. When the supercharging pressure applied to the first diaphragm chamber 40c overcomes this setting force, the exhaust switching valve is gradually opened. That is, the exhaust switching valve 38 remains fully closed until the rotation speed at which the supercharging pressure P2 reaches the predetermined value P5LIT (NEI in FIG. 5), and P2=predetermined value P3□
When the exhaust switching valve 38 reaches the spring 40b
The valve will gradually start opening against the Step 1
At 04, the solenoid valve 60 (VSV2) is closed. Therefore, atmospheric pressure acts on the lower side of the diaphragm 48a, and the intake bypass valve 46 is kept closed by the spring.

In the acceleration state, the engine rotation speed NE is NE.

When it is determined that the transition to the first stage supercharging region has occurred, the process proceeds from step 100 to step 106, and the solenoid valve 50 (V
When SVI) is turned on, atmospheric pressure is introduced into the first diaphragm chamber 40d, and the biasing force applied to the exhaust switching valve 38 in the closing direction suddenly decreases, causing the exhaust switching valve 38 to open all at once. In step 108, the solenoid valve 60 (VS
V2) is turned on, supercharging pressure acts on the lower side of the diaphragm 48a, and the diaphragm 48a is pressed upward.
The intake bypass valve 46 is opened all at once.

FIG. 4 shows the respective pressures at the compressor outlet position (2) of the large turbocharger, the position (2) downstream of the compressor of the small turbocharger, and the position (3) downstream of the intercooler. In the low speed range, the pressure at the compressor outlet (2) of the small turbocharger is the maximum pressure point, as shown by the broken line (1). In other words, in the low speed range (I), the large turbocharger 1
Since the rotation of 7 is not increasing, the pressure of ■ is low, and the small turbocharger is performing supercharging operation, so downstream ■
The pressure is high, and downstream of the intercooler 2, the pressure decreases by the pressure loss of the intercooler 29 (although the loss itself is small). On the other hand, in the high speed range (m), the large turbocharger is supercharging, so the pressure downstream of it is at its maximum, and with the small turbocharger, the pressure decreases by the pressure loss, and the pressure loss of the ink cooler 29 is large. The pressure in (①) further decreases.

By controlling the exhaust switching valve by the pressure at the compressor outlet of the small turbocharger, the exhaust switching valve 38
The pressure P8 of the intake manifold after the valve is opened can be set to the characteristic n in FIG. 3(a).

That is, as shown in FIG. 4, the pressure at the position (■) is large at low engine speeds and small at high engine speeds. Therefore, by controlling the pressure at the position (2) downstream of the small turbocharger, it is possible to obtain the intake manifold pressure n that increases as the engine rotation increases. That is, the set pressure of the spring 40d of the drive actuator 40 of the exhaust switching valve 38 is determined so that the valve opens in a low speed range, and the valve does not open unless the pressure is increased at high speeds.As a result, the pressure in the downstream intake manifold is The pressure increases by this increased pressure.

At the time of transition from second-stage supercharging to first-stage supercharging, the exhaust switching valve 38 is suddenly opened, so that the supercharging pressure suddenly drops to NE=NE1, and the torque decreases. However, at the same time, the exhaust pressure decreases, which causes an increase in torque. As a result, the torque decreasing factor and the torque increasing factor are canceled, and there is no risk of a large torque change occurring when the exhaust switching valve is suddenly opened.

After opening the exhaust switching valve, the downstream part of the ink cooler 29
The wastegate valve 34 is controlled by the pressure at point . As shown in FIG. 4, the pressure downstream of the ink cooler 29 is large in the low speed range and small in the high speed range. This is because the influence of the pressure loss of the intercooler 29 is stronger at high speeds when the flow rate is large.

Therefore, by controlling the waste gate valve by the pressure downstream of the ink cooler 29, the pressure in the intake manifold can be increased on the high rotation side, as shown by m in FIG. 3(a). That is, since the setting of the spring 34b of the wastegate valve 34 is set based on the pressure on the low rotation side, the valve cannot be opened on the high rotation side unless the supercharging pressure is increased, and as a result, the intake manifold The pressure P increases on the high rotation side. Therefore, it is possible to improve the torque characteristic to m'. The broken line p is the boost pressure characteristic when the wastegate valve is controlled by the pressure upstream of the intercooler (for example, the pressure downstream of a large turbocharger) during high rotation, and as the intake manifold pressure decreases, p' This invention solves the problem of large torque down as shown in the figure.

〔effect〕

According to this invention, the exhaust switching valve is controlled by the outlet pressure of the small turbocharger, and the waste gate valve is controlled by the intercooler downstream pressure, thereby changing the torque in the transition region from 2-stage supercharging to 1-stage supercharging. It is possible to make this smooth and prevent a decrease in torque at high rotation speeds in the first-stage supercharging region.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a flowchart explaining the operation. FIG. 3 is a graph schematically showing the relationship between rotation speed, boost pressure, and torque. FIG. 4 is a graph showing the relationship between each position of the intake pipe and pressure. 10...Engine body, 12...Intake pipe, 14...
・Exhaust pipe, 17...Large turbocharger, 18...
- Small turbocharger, 30... First exhaust bypass passage, 32... Waste gate valve, 36... Second exhaust bypass passage, 38... Exhaust switching valve, 44... Intake bypass valve, 7
8, 80...pressure sensor.

Claims (1)

[Claims] A large turbocharger, a small turbocharger, and an intercooler are arranged in series in the gas flow direction, an exhaust switching valve is provided in the bypass passage that bypasses the small turbocharger, and a waste gate valve is provided in the bypass passage that bypasses the large turbocharger. In a two-stage supercharged internal combustion engine with an intercooler located downstream of the compressor of a small turbocharger, the exhaust switching valve is controlled by the compressor outlet pressure of the small turbocharger, and the wastegate valve is controlled by the pressure downstream of the intercooler. A supercharging pressure control device for a two-stage supercharging internal combustion engine, characterized in that: