JPH04214928A - Intake device for engine - Google Patents

Abstract

PURPOSE:To prevent breakage of a supercharger by an excessive supercharge caused by a closure fixture of a switching valve provided at one of two lines of intake passages on the downstream side of the supercharger. CONSTITUTION:Two lines of intake passages 21, 22 are provided on the downstream side of superchargers 11, 12, one intake passage 22 of them have a switching valve 27 to open and close the passage corresponding to an operating condition. If the switching valve 27 is fixed at a closing position or not is detected by a fixture detecting means, and when a fixture is detected, a supercharge pressure by actuation of the superchargers 11, 12 is reduced by a control means 60.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an engine having two intake passages downstream of a supercharger.

0002

[Prior Art] A conventional engine intake system includes an intake passage for low-load, low-speed rotation (hereinafter referred to as primary intake passage) and an intake passage for high-load, high-speed rotation on the downstream side of a turbocharger. (hereinafter referred to as the secondary intake passage)
Some engines are equipped with a system intake passage and are provided with an on-off valve for opening and closing this passage in the high-load, high-speed intake passage (for example, see Japanese Patent Laid-Open No. 60-216031). In such a device, in a relatively low-load or low-speed operating range, the on-off valve is closed and intake is performed only through the primary intake passage, thereby increasing the intake flow velocity, and in a relatively high-load or high-speed operating range. In this case, a sufficient amount of intake air can be ensured by opening the on-off valve and inhaling air through both intake passages.

By the way, there are two types of valves used as the above-mentioned on-off valves: a normally open type that is held in an open position under normal conditions and driven in the closing direction as appropriate using intake negative pressure, and one that is closed under normal conditions. A normally closed type is considered, which is held in position and driven in the opening direction as appropriate. Among these, when using a normally open type, the intake negative pressure is not sufficiently raised when the engine starts, so the on-off valve cannot be closed at this time, and the fuel cannot be sufficiently vaporized and atomized. Normally closed valves are more likely to malfunction, whereas normally closed valves can be used to ensure that the on-off valve is kept in the closed position from the time the engine is started, so normally closed valves are commonly used. It is considered desirable to use .

0004

[Problem to be solved by the invention] In the above-mentioned intake system, if the on-off valve is stuck in the closed position for some reason, intake is performed only through the primary intake passage even during high supercharging. It turns out. In such a state, the intake pressure increases due to, for example, a wastegate valve being closed under intake pressure feedback control, which places an excessive load on the supercharger, which may result in damage to the supercharger. In particular, normally closed type valves, which are suitable as the above-mentioned on-off valves, are kept in the closed position under normal conditions, so they are more likely to cause the above-mentioned sticking than normally open types, and there are no countermeasures to prevent this. This will be a big challenge.

The present invention has been made in view of the above, and its object is to provide an engine intake system that can prevent damage to a supercharger due to excessive supercharging when the on-off valve is stuck closed. This is what we intend to provide.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the invention according to claim 1 has two systems of intake passages on the downstream side of a supercharger, and one intake passage has this passage in an operating state. In an engine intake system provided with an on-off valve that opens and closes according to the timing, the on-off valve is fixed in the closed position. The configuration includes a control means for reducing supercharging pressure due to operation of the supercharger.

The invention set forth in claim 2 is dependent on the invention set forth in claim 1, and is characterized in that the on-off valve is kept in a closed position in a normal state and is driven in the opening direction by intake negative pressure. Must be closed type.

[0008]

[Operation] With the above configuration, in the present invention, when the on-off valve is stuck in the closed position, the sticking detection means detects this,
Based on this detection, the control means appropriately reduces the supercharging pressure by operating the supercharger, thereby preventing excessive supercharging.

In particular, in the invention as claimed in claim 2, a normally closed type is used as the on-off valve, and by keeping the on-off valve in the closed position from the time of starting the engine, the intake flow velocity at the time of starting the engine is increased. It will be done.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall structure of an intake system A for a supercharged engine according to a first embodiment of the present invention. This intake device A has two supercharging systems: a turbo supercharger for low flow range (hereinafter referred to as primary supercharger) 11 and a turbo supercharger for high flow range (hereinafter referred to as secondary supercharger) 12. Each supercharger 11, 12 has a compressor impeller 11a, 12a and a turbine impeller 11b, 12b that interlock with each other.
have.

Reference numeral 1 denotes an intake passage 1 of an engine, and the intake passage 1 is divided into an upstream intake passage 2 and a downstream intake passage 3. The upstream intake passage 2 consists of a single main intake passage 14 and two branch passages 15 and 16 that branch from the main intake passage 14, and each of the branch passages 15 and 16 includes the compressor impeller. 11a and 12a are respectively arranged, and both branch passages 15,
16 are merging. An air flow meter 17 is provided in the main intake passage 14, and an air cleaner 18 is provided downstream of the confluence of the two branch passages 15 and 16.

The downstream intake passage 3 is a two-system intake passage consisting of a primary intake passage 21 and a secondary intake passage 22, and these intake passages 21 and 22 are independently connected to each cylinder of the engine body 20. It is communicated. Throttle valves 23 and 24 are respectively disposed in the upstream portions of the intake passages 21 and 22, and downstream of these throttle valves 23 and 24, both intake passages 21 and 22 are connected to the communication passage 2.
6.

Further, in the secondary intake passage 22, a P-only (p-only) is provided at a position directly downstream of the communication passage 26 as an on-off valve for opening and closing the secondary intake passage 22.
a primary-only) valve 27 is provided. This P-only valve 27 is of a normally closed type that is held in a closed position in a normal state, and is appropriately driven in the opening direction by a drive mechanism 4 that utilizes intake negative pressure. However, in the present invention, a normally open type may be used regardless of the specific type of on-off valve.

The drive mechanism 4 includes a check valve 30, a negative pressure tank 32, a P-only valve control solenoid 34, and a diaphragm actuator 36. The P-only valve control solenoid 34 opens and closes a communication passage 35 between the primary intake passage 21 and the diaphragm actuator 36 as appropriate by its operation. The diaphragm actuator 36 is actuated by the intake negative pressure in the passage 21, and the P-only valve 27 is opened.

Further, 5 is an exhaust passage of the engine,
The exhaust passage 5 is branched on its upstream side (engine side) into a primary exhaust passage 41 and a secondary exhaust passage 42, and both exhaust passages 41 and 42 are merged and connected to the main exhaust passage 40. . In the primary exhaust passage 41 and the secondary exhaust passage 42, the supercharger 11,
Twelve turbine impellers 11b and 12b are arranged. Each of the turbine impellers 11b, 12b is bypassed by a common waste gate passage 43, and a waste gate valve 44 for opening and closing the passage 43 is provided in this waste gate passage 43. The drive mechanism for the waste gate valve 44 is composed of a boost pressure control solenoid 46 and an actuator 48, and the boost pressure control solenoid 46 opens and closes a communication path between the main intake passage 14 and the actuator 48 as appropriate. , actuator 48 operates in synchronization with this, and the waste gate valve 44 is driven to open and close by this operation.

Further, at a position immediately upstream of the turbine impeller 11b in the secondary intake passage 42,
An exhaust switching valve 50 that opens and closes this secondary intake passage 42 is provided. This exhaust switching valve 50 is also driven to open and close by a drive mechanism consisting of an exhaust switching solenoid 51 similar to the boost pressure control solenoid 46 and an actuator 52 similar to the actuator 48. By closing the valve 50, the state is switched to a supercharging state using only the primary supercharger 11.

Furthermore, the passage immediately upstream of the turbine impeller 11b in the primary supercharger 11 communicates with the waste gate passage 43 through a bypass passage 53, and a safety valve 54 is provided in the bypass passage 53. 54 is activated to open the bypass passage 53 when the exhaust pressure immediately upstream of the turbine impeller 11b becomes higher than a certain value.

Further, the intake system A includes various sensors such as a throttle sensor 56 that detects the opening of the throttle valves 23 and 24, and a P-only valve position sensor (fixed) that detects the opening of the P-only valve 27. (constituting a detection means) 57, a pressure sensor 58 that detects the pressure within the primary intake passage 21, and a crank angle sensor 59
Detection signals from these sensors 56 to 59 are input to the ECU 60. This EC
U60 outputs control signals to various solenoids 34, 46, 51 based on the various detection signals described above, thereby controlling each valve 27, 44, 50 according to the operation state of each actuator 36, 48, 52. control opening and closing.

Furthermore, as a feature of this embodiment device,
As shown in FIG. 2, the ECU 60 includes an operating range determining means 61, a P-only valve sticking determining circuit 62, and a supercharging pressure control circuit 63. The above driving range determination circuit 6
1 as an internal switch, P1 as shown in FIG.
It is equipped with a switch (pressure switch), RO switch (rotation switch), R1 switch (rotation switch), and TVO switch (throttle switch), and by turning on and off these switches, the current operating state is determined in which of the regions shown in Figure 4. This is to determine whether it belongs.

The P1 switch is turned on when the intake pressure detected by the pressure sensor 58 is equal to or higher than a preset pressure value P1, and the TVO switch is turned on when the throttle valve 23 is turned on by the throttle sensor 56.
, 24 are detected to be open. Further, the R1 switch is turned on when the engine speed detected by the crank angle sensor 59 is equal to or higher than a preset value R1, and the R0 switch is turned on when the engine speed detected by the crank angle sensor 59 is higher than the value R1. It is switched on when the low R0 or higher. Strictly speaking, hysteresis is given to the on/off state of each internal switch as shown in FIG. 5, and when each switch is currently in the off state,
It is switched on when the first threshold value V1 or more is reached, and conversely, if it is currently in the on state, when the threshold value V2 or less, which is lower than the first threshold V1, is turned on. is switched off for the first time.

To explain the operating region shown in FIG. 4, first, the P-only region is a low rotation and low load region where the engine speed is R0 or less and the throttle valves 23 and 24 are closed. 27 should be closed and intake should be performed only through the primary intake passage 21. Also,
The wastegate valve forced opening region is a high-speed, high-load region where the engine speed is R1 or more and the intake pressure is P1 or more, and if the p-only valve 27 is closed in this region, the supercharging pressure will be excessive. This is an area where there is a possibility that the temperature may rise and adversely affect the superchargers 11 and 12.

The P-only valve sticking determination circuit 62 also operates a PonP switch (P-only valve) that is turned on when it receives a detection signal from the P-only valve position sensor 57 indicating that the P-only valve 27 is open. o
P-only valve position switch) is provided as an internal switch, and constitutes a sticking determination means for determining whether or not the P-only valve 27 is stuck in the closed position. Specifically, this sticking determination is performed by the driving range determining circuit 6.
If it is detected that the P-only valve 27 is open even though the region determined in step 1 is a P-only region, it is determined that the P-only valve 27 is stuck.

Further, the boost pressure control circuit 63 outputs a control signal to the boost pressure control solenoid 46 as appropriate based on the determination results of the operating range determination circuit 61 and the P-only valve sticking determination circuit 62, It constitutes a control means for controlling the opening and closing of the gate valve 44. Specifically, this opening/closing control is performed in such a manner that the P-only valve 27 is determined to be stuck by the P-only valve sticking determination circuit 62, and the region determined by the operating region determining circuit 61 is the wastegate valve forced opening region. The waste gate valve 44 is configured to open when this occurs.

Next, the control operations actually performed by the ECU 60 will be explained with reference to the flowcharts shown in FIGS. 6 and 7. FIG. 6 is a flowchart of feedback control of supercharging pressure, and FIG. 7 is a flowchart of fail control against sticking of the P-only valve 27.

In feedback control of boost pressure,
First, the ECU 60 reads the reference value Dbase of the duty ratio of the waste gate valve 44 and the target supercharging pressure Tp from another control system that controls the opening/closing operation of the waste gate valve 44 (step S1), and also reads the reference value Dbase of the duty ratio of the waste gate valve 44 and the target supercharging pressure Tp using the pressure sensor 58. The detected actual supercharging pressure Map is read (step S2). Then, it is determined whether the actual boost pressure Map is smaller or larger than the target boost pressure Tp (
Step S3), and as a result, if the actual boost pressure Map is smaller than the target boost pressure Tp, ΔDFB is added to the duty ratio correction value DFB (Step S4), so that the actual boost pressure Map is lower than the target boost pressure Tp. If it is larger than the supply pressure Tp, subtract ΔDFB from the duty ratio correction value DFB (
Step S5). Next, the correction value DFB obtained by adding or adding the above ΔDFB and the above reference value Dbase are added to obtain the total value Dtotal of the duty ratio (step S
6) The operation of the supercharging pressure control solenoid 46 is controlled so that the waste gate valve 44 opens and closes in accordance with the duty ratio of this value.

[0026] Also, in the fail control for the sticking of the P-only valve 27, the ECU 60 first detects the detected values of various sensors such as the throttle sensor 56, the P-only valve position sensor 57, the pressure sensor 58, and the crank angle sensor 59. Read (step S1). and,
Based on these detected values, if both the TVO switch and the P0 switch are turned off (step S
2, YES in S3), that is, P-onl only when the current operating state is in the P-only region shown in FIG.
y valve 27 is closed, and in other cases, that is, when at least one switch is turned on (NO in at least one of steps S2 and S3), P-o
P-o to open the nly valve 27 (step S5)
Controls the operation of the nly valve control solenoid valve 34.

Here, if the control to open the P-only valve 27 is executed and the P-only valve 27 is actually opened, that is, if the PonP switch is turned on (YES in step S6), ) There is no problem and the basic control from Steps S1 to S5 above continues, but if the PonP switch remains off even though the control operation to open the P-only valve 27 is executed, (Step NO in S6), P-only valve 2
7 is fixed (step S7), and emergency control is executed based on this. Specifically, when the current operating state is outside the wastegate valve forced opening region shown in FIG. 4, that is, when the R1 switch is off and the P1
If the switch is off (NO in steps S8 and S9)
), the same operation as the normal control operation is performed, but when the operating state is within the wastegate valve forced opening region, that is, when at least one of the R1 switch and the P1 switch is on (step S8, If at least one of S9 is YES), a forced valve opening signal is output to the supercharging pressure control solenoid 46 (step S10), and the waste gate valve 44 is forcibly opened, thereby reducing the supercharging pressure.

As described above, according to the intake system A of this embodiment, the P-only valve 2 is normally operated in the P-only region.
By closing P-only valve 7 and performing intake only through the primary intake passage 21, the intake flow rate can be increased.In addition, in an emergency when the P-only valve 27 is stuck in the closed position, the wastegate valve is forced to open in the wastegate valve forced opening region. By opening the waste gate valve 44 and lowering the supercharging pressure, it is possible to prevent the intake pressure from increasing under feedback control of the supercharging pressure and placing an excessive load on the supercharger.

In particular, as shown in this example, the above P-o
If a normally closed type is used as the nly valve 27, the P-only valve will remain closed even when the engine is started.
While this has the advantage of reliably holding the valve 27 in the closed position to improve fuel vaporization performance, the above fail control can compensate for the disadvantage that it is more likely to get stuck in the closed position than the normally open type. Therefore, the present invention becomes more effective.

8 to 11 relate to a second embodiment of the present invention, and in the case of this second embodiment, the hardware configuration of the intake device is the same as that of the first embodiment shown in FIG. However, in terms of control, instead of forcibly opening the waste gate valve 44, the supercharging pressure is lowered by adjusting the exhaust switching timing by opening and closing the exhaust switching valve 50.

Specifically, the ECU 60 controls the supercharging pressure by using an exhaust switching map 64 shown in FIG. 8 and an exhaust switching control circuit 65 as a control means instead of the supercharging pressure control circuit 63 shown in the first embodiment. It is configured to be lowered.

The region for exhaust switching set in the exhaust switching MAP 64 is as shown in FIG. The other high rotational speed regions are defined as supercharging regions by both the primary supercharger 11 and the secondary supercharger 12. This region is set with the aim of improving supercharging efficiency as much as possible.

The exhaust switching control circuit 65 has a P-onl
In normal times when the y-valve sticking determination circuit 62 does not determine that the valve is stuck, exhaust switching is performed by opening and closing the exhaust switching valve 50 based on the current operating state and the exhaust switching MAP 64. However, the P-only valve sticking determination circuit 62 In an emergency when it is determined that the fuel is stuck, the control operation is opposite to the contents of the exhaust switching MAP 64, that is, supercharging is performed by both the primary supercharger 21 and the secondary supercharger 22, and the system is moved to the (primary + secondary) supercharging region. At certain times, the exhaust switching valve 5 is configured to perform supercharging only by the primary supercharger 21.
Executes the operation of opening and closing 0.

The specific control operation will be explained with reference to the time chart of FIG. 10 and the flow chart of FIG. 11.

In FIG. 11, the operations from steps S1 to S7 are the same as in FIG. 7, except that the P-only valve 27
If it is determined that the exhaust switching valve 50 is stuck (step S7), and the operating state is in the primary supercharging region set in the exhaust switching MAP 64 (YES in step S11), the exhaust switching valve 50 is opened to switch the primary supercharger 21 and the secondary supercharging Supercharging is performed by both feeders 21 (step S12).
If the operating state is in the (primary+secondary) supercharging region (NO in step S11), the exhaust switching valve 50 is closed to perform supercharging only by the primary supercharger 21 (step S13). In this way, by executing the operation opposite to the content of the exhaust switching MAP 64, which originally aims to improve supercharging efficiency, a substantial reduction in supercharging pressure is realized.

Furthermore, by closing the exhaust switching valve 50 in the above (primary + secondary) supercharging region,
When the exhaust pressure on the primary turbocharger 11 side increases beyond a certain value, the safety valve 54 is activated and the exhaust gas is released from the bypass passage 53 to the waste gate passage 43, thereby preventing the primary overflow due to an excessive increase in exhaust pressure. Damage to the feeder 11 is prevented.

The present invention is not limited to the first and second embodiments described above, but includes various other modifications. For example, in each of the above embodiments, two superchargers 21
. By lowering the supply pressure, the same effect as above can be obtained.

Furthermore, in the present invention, the setting method of the area where air is taken only through one intake passage (the P-only area in the above embodiment) is not limited; for example, the area may be set based only on the level of the load. good. This also applies to the region where the supercharging pressure is forcibly lowered (the waste gate valve forced opening region in the first embodiment).

[0039]

As described above, according to the engine intake system of the present invention, it is possible to detect whether or not the on-off valve that opens and closes one of the two intake passages is stuck in the closed position. Since the supercharging pressure is lowered when the on-off valve is stuck closed, it is possible to prevent damage to the supercharger due to an increase in intake pressure caused by the on-off valve being stuck closed, and it is possible to take effective measures against failures. .

In particular, when a normally closed type of on-off valve is used as the invention as claimed in claim 2, the on-off valve is held in the closed position even when the engine is started to improve the vaporization and atomization performance of the fuel. While having the advantage of improving the structure, the disadvantage of being more likely to get stuck in the closed position than the normally open type can be eliminated, so the effect is significant.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an engine intake system in a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an ECU in the intake device.

FIG. 3 is a time chart showing the relationship between on/off of an internal switch provided in the ECU and an output control signal.

FIG. 4 is a graph for explaining operating ranges set in the ECU.

FIG. 5 is an explanatory diagram for explaining on/off switching of the internal switch.

FIG. 6 is a flowchart of feedback control of boost pressure by the ECU.

FIG. 7 is a flowchart of fail control performed by the same ECU against sticking of the P-only valve.

FIG. 8 is a diagram corresponding to FIG. 2 showing a second embodiment of the present invention.

FIG. 9 is a diagram corresponding to FIG. 4;

FIG. 10 is a time chart showing the relationship between on/off of an internal switch provided in the ECU, an exhaust switching map, and an output control signal.

FIG. 11 is a diagram corresponding to FIG. 7;

[Explanation of symbols]

11 Primary supercharger 12 Secondary supercharger 21 Primary intake passage 22 Secondary intake passage 27 P-only valve (on-off valve) 60
ECU 62 P-only valve sticking determination circuit (sticking detection means)

Claims (2)

[Claims] Claim 1. An intake system for an engine having two intake passages downstream of a supercharger, one of which is provided with an on-off valve that opens and closes the passage depending on operating conditions,
a sticking detection means for detecting that the on-off valve is stuck in the closed position; and a control means for reducing supercharging pressure caused by the operation of the supercharger when the on-off valve is detected to be stuck by the sticking detection means. An engine intake device characterized by comprising: 2. The engine intake system according to claim 1, wherein the on-off valve is kept in a closed position in a normal state and is driven in the opening direction by intake negative pressure.