JPH03275936A - Compression ratio variable two-stage supercharge internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress knocking and improve an efficiency of an engine by lowering a compression ratio in an operation range of a miniture turbocharger, and increasing the compression ratio in the operation range of a large turbocharger. CONSTITUTION:At the time of closing an exhaust switching valve 38, supercharge is performed by a small turbocharger 18. At the opening of the valve 38, the supercharge is performed by a large turbocharger 17. At the time of operating of the small turbocharger 18, the compression ratio of an internal combustion engine is decreased in a compression control mechanism. The compression ratio is increased in the compression control mechanism at the time of operating the large turbocharger 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internal combustion engine that performs two-stage supercharging and has a compression ratio that is variable depending on the state of supercharging.

[Prior art]

Japanese Patent Application No. 45-9084 discloses a system in which a large turbocharger and a small turbocharger are arranged in series, an exhaust switching valve is provided in the exhaust bypass passage that bypasses the small turbocharger, and the exhaust switching valve is installed in the operating range of the small turbocharger. The exhaust switching valve is closed and the exhaust switching valve is opened in the operating range of the large turbocharger. By performing two-stage supercharging, the supercharging effect can be obtained over a wide range from a low engine speed range to a high engine speed range.

[Problem to be solved by the invention]

The conventional two-stage supercharging system has a problem in that knocking tends to occur in the low speed range of the engine when a small turbocharger operates. This is because in the range of use of small turbochargers, the small diameter creates a large flow resistance for exhaust gas, resulting in a large exhaust pressure and a large amount of residual gas in the combustion chamber.

An object of the present invention is to suppress the occurrence of knocking in a two-stage supercharged internal combustion engine at low engine speeds.

[Problem to be solved by the invention]

According to this invention, a large turbocharger and a small turbocharger are connected in series in the gas flow direction.

An exhaust switching valve is installed in the air bypass passage that connects the small turbocharger and small turbocharger, and by opening and closing the exhaust switching valve, the operating range can be switched between the small turbocharger, the large turbocharger, and the large turbocharger. The present invention is further characterized in that it has a compression ratio control mechanism that makes the compression ratio variable, and the compression ratio is reduced by 4 in the operating range of a small turbocharger, and is increased in the operating range of a large turbocharger. A bypass compression ratio capable Ffc' two-stage supercharged internal combustion engine is provided.

[Effect]

When the exhaust switching valve is closed, supercharging is performed by a small turbo charger, and when the exhaust switching valve is open, supercharging is performed by a large turbocharger.

When the small turbocharger is operating, the compression ratio control mechanism reduces the compression ratio of the internal combustion engine, and when the large turbocharger is operating, the compression ratio control mechanism+J compression ratio is increased.

〔Example〕

1st [J indicates an embodiment of this invention (2, 10,
1':/shi:/main body, including the intake pipe 12 and exhaust pipe 14 (
! - is connected. Intake pipe j4 is fuel indigo lid 15
and a throttle valve 16. The popular turbocharger 17 and the small body holder 18 are arranged in series. The large turbocharger t7 is composed of a compressor 1120, a turbine 22, and a rotating shaft 24. The small turbocharger 18 is a compressor 26 and a turbine? 8 and a rotating shaft 25. At the intake pipe 12), in the direction of the flow of intake air, insert a large valve into the intake pipe 12. The compressor 26 of the small turbo charger 18 is arranged in this order, the intercooler 29 is arranged downstream of the compressor 26, and the throttle valve 1G is arranged downstream of the intercooler 29. A small turbo is installed in the exhaust pipe in the direction of exhaust gas flow.
- Turbine 28 of engine 18, large turbocharger 17
The turbines 22 are arranged in this order.

A first exhaust bypass passage 30 is connected to the exhaust pipe by bypassing the turbine of the large turbocharger 17, and a butterfly valve, ie, a butterfly valve, is connected to the first exhaust bypass passage 30.
A valve 32 is arranged. The diaphragm 34a is connected to the bypass valve 3.
2. Although the bypass valve 32 is normally urged to close by the spring 34b, the wastegate valve 32 is opened by the negative pressure generated in the diaphragm 34a against the spring 34b.

A second exhaust bypass passage 36 is provided to bypass the turbine 28 of the small-sized battery charger 18, and an exhaust switching valve 38 as a butterfly valve is provided in the second bypass passage 36. The exhaust switching valve 38 is connected to its actuator 40, and the actuator 40 is configured as a two-stage diaphragm mechanism.

As will be described later, this actuator 4Q closes the exhaust switching valve 38 until the large turbocharger 17 exerts its full supercharging capacity, and closes the exhaust switching valve 38 until the large turbocharger 17 exerts its full supercharging capacity. It has the property of rapidly opening up. The actuator 40 includes diaphragms 40a, 40b and springs 40c, 40d.
and one diaphragm 40a is 11 to 4. Oe
The other diaphragm 40b is connected to the exhaust switching valve 40 through the lot 40.
A step-like opening characteristic of the exhaust switching valve 38 can be obtained by applying supercharging pressure to b. That is, the diaphragm 40b
When supercharging pressure is applied to , the force of spring 40c and
In order to open the exhaust switching valve 38 against the resultant force of the spring 40d, the valve is opened slowly. diaphragm 40
When supercharging pressure is applied to a, the exhaust switching valve 38 is opened against only the force of the spring 40c, so that the valve operation is quick during that time.

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 acticoator 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 I8 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 48a from below, and the intake bypass valve 46 is opened.

In this embodiment, the internal combustion engine is provided with an exhaust gas recirculation (EGR) device, the EGR device comprising an exhaust gas recirculation passage (EGR).
R passage) 50, and an exhaust gas recirculation control valve (EGR valve) 52 on the EGR passage 50.The EGR valve 52 is provided with a diaphragm 52a, and opens and closes depending on the pressure applied to the diaphragm 52a. controlled.

A three-way solenoid valve (VSVI) 54 is provided for pressure control to the actuator 34 of the wastegate valve 34,
This solenoid valve 54 is located at a position where atmospheric pressure is introduced into the diaphragm 34a and at the compressor 2 of the small turbocharger 18.
6 and a position 56 upstream of the intercooler 29 where supercharging pressure is introduced. When atmospheric pressure is introduced, the wastegate valve 32 is driven to close by the spring 34b, and when the supercharging pressure is introduced, the wastegate valve 32 is opened against the spring 34b.

A three-way solenoid valve (VSV2) 5B is provided to control the pressure on the diaphragm 40a of the actuator 40 of the exhaust switching valve 38. It changes depending on the position of the outlet 60 where the supercharging pressure is introduced. Moreover, the pressure of the compressor outlet 60 of the small turbocharger 18 is constantly introduced into the diaphragm 40b.

Two three-way solenoid valves 64, 66 are provided for pressure control to the actuator 48 of the intake bypass valve 47. A three-way solenoid valve (VSV3) 64 is provided above the diaphragm 48a of the actuator actuator 48 of the intake bypass valve 46 for pressure control. It changes depending on the position at which the supercharging pressure is introduced at the compressor outlet 60 of the charger 18. In addition, a 3-way solenoid valve (V
SV4) 66 is provided to control the pressure below the diaphragm 48a of the actuator actuator 48 of the intake bypass valve 46, and this solenoid valve 66 controls the negative pressure at a position 68 downstream of the throttle valve 16 below the diaphragm 48a. It is switched between the position where the pressure is introduced and the position where the supercharging pressure of the compressor outlet 60 of the small turbocharger 26 is introduced.

Three-way solenoid valve (VSV5) 70 is provided to control the operation of the EGR valve 52, and this solenoid valve 70 is connected to the diaphragm 5.
The position is switched between a position where atmospheric pressure is introduced into 2a and a position where negative pressure is introduced at a position 68 downstream of the throttle valve 16.

A control circuit 72 is provided for supercharging control in this invention, and each solenoid valve 54 (VSVI), 58 (VSV
2), 64 (VSV3), 66 (VSV4),
70 (VSV5), the fuel injector 15 is driven. Incidentally, the ignition plug is also controlled via the igniter 74 and the distributor 76, but since these controls are not directly related to the present invention, detailed explanation will be omitted. The control circuit 72 is connected to various sensors in order to execute control according to the present invention. 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. is provided. An air-fuel ratio sensor 8 is installed downstream of the turbine 22 of the large turbocharger 17.
2 can be provided. In addition, an air flow meter (not shown) that measures the amount of intake air Q, a sensor that detects the gear position of the transmission (not shown), and a pulse pulse every 30° and 720° of the crank angle for timing control are provided. A signal is input.

Further, according to the present invention, a mechanism for making the compression ratio variable is provided, and this mechanism may be of any known type; It can be a mechanism.

This mechanism is schematically shown in FIGS. 2 and 3. The eccentric ring 85 is disposed between the upper end of the connecting rod 86 and the piston pin 87, and the eccentric ring 85 can be freely engaged and disengaged by a hydraulically driven lock bin 89. That is, the maximum eccentric portion of the eccentric ring 85 is located at the farthest side l.
When the piston pin 87 is positioned at the highest position σI, the compression ratio is at its maximum. The LE reduction ratio becomes minimum. In that state, the eccentric ring 8b is rotated according to the position of the piston 92 (7, the eccentric ICx ring 85 is set free).
Q) ,,1r.

At the dead center, the maximum eccentric part of the eccentric ring 85 is located at the lowest position (2, at the bottom dead center of the piston 92, the maximum eccentric part of the eccentric ring 85 is located at the lowest position. If the position is maintained at the lowest position, the position of the screw (-1/97) at the top dead center can be set to the lowest position, and the maximum compression ratio can be obtained. In order to lock the eccentric ring 85 to the position where the maximum compression ratio is obtained, a cock groove 91 is formed in the eccentric ring 85, and a lock pin 89 is provided in the neck groove land 86.

A first hydraulic chamber 90 is formed in the lower part of the mortar/ink pin 2/89, and in this state, when the piston 92 descends to the bottom dead center, the lock bin 89 closes the eccentric ring 85. Fitted into the lock groove 91 17, the maximum eccentric part of the eccentric ring 85 is placed at the lowest position [7]:::
, l lock, \re, the piston position at top dead center Y' is highest, so the maximum compression ratio can be obtained. In order to obtain a small compression ratio, each time hydraulic pressure is applied from the hydraulic chamber 93 on the opposite side, the +1 knob 89 is lowered and removed from the 1 knot groove 91. In this case, the eccentric ring 85 becomes free,
At the top dead center position, the maximum eccentric part of the ring 85 is at the top, so the position of the piston pin 87 is proportionally F lowered to L7, and the minimum B6 compression ratio is obtained.

The hydraulic passages 95.96 of the hydraulic chambers 90.93-\ are formed in the Nifnecting "jrad 86" and are
As described in No. 37, an external ω oil pressure source 98 is connected via a lubricating oil passage in the crankshaft 97, an oil passage in the crank journal, and an oil passage in the engine body. A switching device a100 is provided for switching between flow directions of the control hydraulic pressure, and this switching device 1(]O is equipped with switching valves 102 and 104. That is, when introducing hydraulic pressure into the hydraulic chamber 90, a switching device a100 is provided. (High compression ratio), turn on the switching valve 102
, 104 is turned ON, and when introducing hydraulic pressure into the oil B chamber 93 (low compression ratio), the switching valve 102 is turned ON, and 104 is turned OFF.
Let it be F. As shown in FIG. 1, the switching device 100 is driven by a control signal from the control circuit 72.

The operation of the control circuit 72 will be explained below with reference to the diagram in FIG. FIG. 4 shows a routine for controlling boost pressure. In step 120, the compressor outlet pressure P of the small turbocharger 18 is determined.

) It is determined whether or not the pressure FJ1 of the large turbocharger 17 is satisfied. Figure 5 shows the relationship between engine speed NE and supercharging pressure (turbocharger outlet pressure) when the opening degree of throttle valve 16 is fixed constant, and shows the relationship between small turbocharger outlet pressure P
2 rises earlier than the rise of large turbocharger outlet pressure P. Therefore, in a state where the engine speed has not yet increased, P2 >r' holds true, and in step 122, the solenoid valve 54 (VSVI input is turned off).
FF is applied, atmospheric pressure is introduced into the diaphragm 34a, and the wastegate valve 32 is closed by the spring 34b. In step 126, the solenoid valve 58 (VSV2> that controls the actuator 40 is turned off. Therefore, the diaphragm 40a of the actuator 40 is exposed to the atmosphere L]
- is effective. On the other hand, since the compressor output L1 pressure of the small turbocharger 18 is always introduced into the diaphragm 40b, the small turbocharger 1 resists the spring force corresponding to the resultant force of the springs 40e and 40d.
The operation of the exhaust switching valve 38 is controlled by the compressor output pressure of 8. That is, the spring force is the supercharging Ef, P
2, the exhaust switching valve 38 remains fully closed, but the exhaust switching valve 38 remains closed until the number of revolutions (NE in FIG. 5) at which the supercharging pressure)) 2 reaches the predetermined value The exhaust switching valve 38 is maintained fully closed, and when it reaches P2-predetermined value PSε, the exhaust switching valve 38 gradually starts to open against the closing urging force which is the resultant force of the springs 40e and 40d. Regarding the operation of the intake bypass valve 46 at low rotation speeds, the solenoid valve 64 (VSν3) is turned on in step 126, and the compressor outlet pressure P2 of the turbocharger 18 acts on the upper side of the diaphragm 48a, so that the intake bypass valve 46 is activated.
will be closed. Further, in step 128, the solenoid valve 66 (
V5V4) is turned off, the intake pipe pressure (negative pressure at this time) downstream of the throttle valve 16 is reduced to 4.8
a, the diaphragm 48a is pulled downward, increasing the closing force of the intake bypass valve 46 and ensuring its reliable closing. Step 129 shows control to lower the compression ratio. Therefore, the solenoid valves 102 and 104 are turned off, hydraulic pressure is introduced into the hydraulic chamber 93, and hydraulic pressure is removed from the hydraulic chamber 95. Therefore, the lock pin 89 comes out of the lock groove 91, the eccentric ring 85 becomes freely rotatable, and the maximum eccentric part of the eccentric ring 85 can be at the top at the top dead center position of the piston 92 as described above. A minimum compression ratio is obtained.

In the acceleration state, the engine speed NE increases to NH3, the rise of the compressor outlet pressure P of the large turbocharger 17 catches up with the compressor outlet pressure P2 of the small turbocharger 18, and when P2=P, the step starts from step 120. Proceed at 130 and proceed with solenoid valve 54
(VSVI) is turned on, and the diaphragm 34a is placed at position 5.
6 is introduced, and the wastegate valve 32 is urged in the opening direction against the spring 34b. In step 132, the solenoid valve 58 (VS
V2) is turned on. Therefore, since supercharging pressure acts on the diaphragm 40a, the exhaust switching valve 3 counteracts the supercharging pressure.
The spring 40b is no longer involved in the force that closes 8, and only the weak biasing force of the spring 40c is involved in the closing force. Therefore, the actuator 40 opens the exhaust switching valve 38 all at once. In step 134, the solenoid valve 66
(VSV4) is turned off, atmospheric pressure acts on the upper side of the diaphragm 48a, and in step 136, the solenoid valve 66 (
VSV4) is turned on and supercharging pressure acts on the lower side of the diaphragm 48b, so the diaphragm 48a is pushed upward and the intake bypass valve 46 is opened all at once.

Step 138 shows control to increase the compression ratio.

That is, the solenoid valves 102 and 104 are turned on, and the hydraulic chamber 90 is turned on.
The hydraulic pressure is introduced into the hydraulic chamber 93, and the hydraulic pressure is removed from the hydraulic chamber 93. Therefore, the eccentric ring 85 comes to the bottom dead center first, and the eccentric ring 85 reaches the bottom dead center first.
When the maximum eccentric portion of the compressor 5 is directed downward, the lock pin 89 is fitted into the lock groove 91 and the eccentric ring 85 is locked in this position, resulting in a high compression ratio.

FIG. 6 shows the outlet pressure P3 and the turbine outlet pressure P4 of the large turbocharger, respectively. Point A is exhaust switching valve 3
The point B corresponds to the point where the exhaust switching valve 38 opens all at once (the point where P2=P is obtained). Before the point B where the exhaust switching valve 38 suddenly opens, the pressure in the front and back of the turbine of the small turbocharger is high, and the amount of supercharging work of the small turbocharger increases, so the exhaust pressure rises and the residual gas increases, causing knocking. is likely to occur. In the present invention, this problem can be solved by lowering the compression ratio. On the other hand, since the exhaust pressure does not increase after the exhaust gas switching valve is completely opened, performance can be improved by increasing the compression ratio.

In the embodiment described above, in order to simplify control, the compression ratio is switched and controlled in conjunction with the operation of the exhaust switching valve 38. That is, before the exhaust switching valve 38 suddenly opens when P2=P, the compression ratio is set low (and after p2=p and the exhaust switching valve 38 suddenly opens, the compression ratio is set high. The compression ratio can be switched by detecting the supply pressure.

In FIG. 6, line l indicates the differential pressure across the compressor 26 of the small turbocharger 18 (=P2-P,'),
This indicates the amount of supercharging work to be shared by the small turbocharger 18. When the small turbocharger 18 is supercharging, the exhaust pressure increases, making knocking more likely to occur. Therefore, the compression ratio is reduced in the differential pressure region across the small turbocharger on the left side of line m in the diagram, which includes the region where the differential pressure across the small turbocharger is largest, and the compression ratio is reduced in the differential pressure region across the small turbocharger on the right side. Control may be performed to increase the compression ratio. Alternatively, similar control can be performed using the compressor outlet pressure P2 of the large turbocharger.

That is, in the region of the compressor outlet pressure P2 of the large turbocharger 17 on the left side of line m in FIG. 5, the work of the small turbocharger 18 is large and there is a risk of knocking, so the compression ratio is lowered and In the area of large-wall turbocharger 17's Tj unit output, the proportion of supercharging work that small turbo charger 18 accumulates decreases (2, the exhaust pressure decreases, and 4- Since the compression ratio is reduced, control is performed to increase the compression ratio.

[Ekio]

By lowering the compression ratio in the operating range of a small turbocharger, and by increasing the compression ratio in the operating range of a large turbocharger,
The conflicting demands of suppressing knocking and improving engine efficiency can be reconciled.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a diagram showing a variable compression ratio mechanism in an embodiment. FIG. 3 is a sectional view taken along line I-III in FIG. 2. FIG. 4 shows flowcharts 1 and 6 for explaining the operation of the control circuit of the embodiment, and FIG. 5 is a private supply pressure characteristic diagram with respect to the rotation speed by this inventive supercharging device. Figure 6 is an exhaust pressure characteristic diagram with respect to rotational speed. IO/engine body, 12...intake pipe, 14...exhaust pipe, 17...large turbocharger, i8...small turbocharger. 30...first exhaust bypass passage. 32... Waste gate valve, 36... Second exhaust bypass passage, 38... Exhaust switching valve, 44... Intake bypass valve, 5
0-4GR passage, 54.58, 64.66-Solenoid valve (V
SV), 78, 80...Pressure force, 85...Eccentric ring, 89...[1 Tsukbin, 81...Lock full,
9093...Hydraulic chamber, 98...Hydraulic pump, 100
... Hydraulic switching device, 102, 104 ... Solenoid valve. 100...Hydraulic switching device diagram diagram diagram

Claims (1)

[Claims] A large turbocharger and a small turbocharger are arranged in series in the gas flow direction, an exhaust switching valve is provided in the exhaust bypass passage that bypasses the small turbocharger, and the small turbocharger and large turbocharger can be connected by opening and closing the exhaust switching valve. and a compression ratio control mechanism that makes the compression ratio variable, reducing the compression ratio in the operating range of a small turbocharger and increasing the compression ratio in the operating range of a large turbocharger. A two-stage supercharged internal combustion engine with variable compression ratio.