WO2013021456A1

WO2013021456A1 - Blow-by gas return device for supercharged engine

Info

Publication number: WO2013021456A1
Application number: PCT/JP2011/068121
Authority: WO
Inventors: 有希天本; 輝小川
Original assignee: トヨタ自動車株式会社
Priority date: 2011-08-09
Filing date: 2011-08-09
Publication date: 2013-02-14

Abstract

A compressor (4) rotated by means of an exhaust turbine (13), and an intercooler (6) that cools the intake air discharged from that compressor (4), are provided in the intake passage of a supercharged engine. A blow-by gas return device returns the blow-by gas generated by this supercharged engine to the supercharged engine by means of the intake air. This return device is equipped with a bypass passage (21), which connects a region downstream from the intercooler (6) in the intake passage and a region upstream from the compressor (4) in the intake passage, and an ejector pump (22), which sucks in the blow-by gas by means of the negative pressure generated by the force of the flow of the intake air flowing in the bypass passage (21). By means of this configuration durability can be ensured easily and the deposition of deposits can be controlled easily while enabling a suitable return of blow-by gas during supercharging.

Description

Blow-by gas reduction device for supercharged engine

The present invention is applied to a supercharged engine in which a compressor rotated by an exhaust turbine and an intercooler that cools intake air discharged from the compressor are provided in an intake passage, and blowby gas generated in the supercharged engine is reduced. The present invention relates to a blow-by gas reduction device that returns to the supercharged engine through intake air.

A blow-by gas reduction device that reduces blow-by gas generated in an engine to the engine through intake air is known as a device that is applied to a vehicle-mounted engine. In a naturally aspirated engine, blow-by gas is sucked from a crankcase or the like using intake negative pressure and introduced into the intake air. However, in a supercharged engine, when the engine is supercharged, the pressure in the intake passage becomes positive, and the opportunity for forming a negative pressure during intake is limited. Therefore, using only the intake negative pressure reduces the blowby gas sufficiently. It becomes difficult to do.

Therefore, conventionally, a blow-by gas reduction device that sucks blow-by gas using an ejector pump (jet pump) as proposed in Patent Document 1 has been proposed. In the blow-by gas reduction device described in Patent Document 1, a bypass passage is provided to connect a downstream portion of the compressor of the turbocharger in the intake passage and a upstream portion of the compressor, and an ejector pump is provided in the bypass passage. is doing. Then, by connecting the blow-by gas reduction passage extended from the crankcase of the engine to the ejector pump, the negative pressure generated by the ejector pump due to the flow of intake air flowing in the bypass passage from the downstream side of the compressor to the upstream side thereof Thus, the blow-by gas in the crankcase is sucked.

Conventionally, a blow-by gas reduction device as shown in Patent Document 2 has also been proposed. The blow-by gas reduction device described in the same document provides a bypass passage that connects a portion of the intake passage downstream of the intercooler and a portion near the intake port, and an ejector pump is disposed on the bypass passage to The blow-by gas is sucked by the negative pressure generated by the ejector pump.

JP 2009-299645 A JP 2009-133292 A

According to such a conventional blow-by gas reduction device, it is possible to satisfactorily reduce the blow-by gas even in a supercharged engine with a low chance of generating negative intake pressure. However, in the blow-by gas reduction device of Patent Document 1, the upstream end of the bypass passage is connected to the intake passage on the downstream side of the compressor, and intake air that has become hot due to compression by the compressor is introduced into the bypass passage. . Therefore, the ejector pump is exposed to high-temperature intake air, and it is difficult to ensure the durability unless a material excellent in heat resistance and corrosion resistance is used for the ejector pump or the like. Further, the downstream end of the bypass passage that introduces the blow-by gas into the intake passage on the upstream side of the compressor is relatively close to the upstream end of the bypass passage that takes in the intake air from the intake passage on the downstream side of the compressor. Therefore, the oil component introduced into the intake passage along with the blow-by gas from the bypass passage is easily introduced into the bypass passage from the intake passage, and the oil component forms a deposit in the bypass passage and the ejector pump, thereby clogging the passage. May occur.

On the other hand, in the blow-by gas reduction device of Patent Document 2, since both the upstream end and the downstream end of the bypass passage are positive pressure during supercharging, a differential pressure is formed between the upstream end and the downstream end of the bypass passage. In addition, it is necessary to install a valve for adjusting the air flow rate downstream of the intercooler, making it difficult to ensure the differential pressure.

The object of the present invention has been made in view of such circumstances, and the problem to be solved is to ensure durability and suppress deposit accumulation while allowing blowby gas to be reduced appropriately even during supercharging. An object of the present invention is to provide a blow-by gas reduction device for a supercharged engine that can easily perform the above.

In order to solve the above problems, a blow-by gas reduction device for a supercharged engine according to the present invention is a supercharger in which a compressor rotated by an exhaust turbine and an intercooler for cooling intake air discharged from the compressor are provided in an intake passage. A blow-by gas reduction device that is applied to an engine and that reduces blow-by gas generated in the supercharged engine to the supercharged engine through intake air, and is provided on the downstream side of the intercooler in the intake passage and the compressor in the intake passage. A bypass passage connecting the upstream portion and a negative pressure generator that generates a negative pressure by the flow of intake air flowing through the bypass passage and sucks blow-by gas by the negative pressure.

At the time of supercharging, the positive pressure is weaker at the downstream side of the intercooler in the intake passage than at the downstream side of the compressor, but at the upstream side of the compressor, negative pressure is generated by suction of the intake air by the compressor. It is getting bigger. Therefore, at the time of supercharging, a large differential pressure is generated between the upstream portion of the compressor in the intake passage and the downstream portion of the intercooler in the intake passage. Begins to flow. The blow-by gas generated in the supercharged engine is sucked by the negative pressure generated by the negative pressure generator disposed in the bypass passage using the flow of the intake air. Such sucked blow-by gas is introduced into a portion of the intake passage upstream of the compressor along with the intake air flowing through the bypass passage.

At this time, since the intake air is introduced into the bypass passage from the downstream of the intercooler that cools the intake air that has become hot due to the compression of the compressor, low-temperature intake air is introduced into the negative pressure generator. In addition, oil mist derived from blow-by gas, turbocharger bearings, etc. is mixed in the intake air, but most of such oil mist passes from the intake air while passing through the intercooler having a complicated labyrinth structure. It will be removed. Therefore, by introducing the intake air from the downstream of the intercooler, the inflow of oil into the bypass passage is also limited. Therefore, according to the above configuration, it is possible to easily ensure durability and suppress deposit accumulation while enabling the reduction of a suitable blow-by gas during supercharging.

By the way, in such a blowby gas reduction device of the present invention, the magnitude of the negative pressure formed by the negative pressure generator is to increase the differential pressure between the upstream portion of the compressor and the downstream portion of the intercooler in the intake passage. The pressure difference increases, and the differential pressure increases according to the supercharging rate of the intake air. For this reason, if the negative pressure generator is designed so that sufficient blow-by gas can be recirculated even when the supercharging rate is small, the negative pressure generated by the negative pressure generator becomes excessive when the supercharging rate is high. As a result, the flow rate of the blow-by gas to be reduced becomes too large, and a large amount of oil mist is introduced into the intake air together with the blow-by gas. Even in such a case, if a valve that adjusts the amount of blow-by gas sucked by the negative pressure generator is provided, the flow rate of the blow-by gas returned to the supercharged engine is appropriately adjusted so as to be suitable for ventilation. can do.

For example, an ejector pump can be used as the negative pressure generator applied to the blow-by gas reduction apparatus of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the whole structure of the blow-by gas reduction apparatus of the supercharged engine which concerns on one embodiment of this invention. Sectional drawing which shows the cross-section of the ejector pump employ | adopted as the embodiment. The graph which shows the relationship between the blow-by gas flow rate and the intake pipe pressure in each case with and without the second PCV valve.

Hereinafter, an embodiment of a blow-by gas reduction device for a supercharged engine according to the present invention will be described with reference to FIGS.

First, the configuration of the blow-by gas reduction device for a supercharged engine according to the present embodiment will be described with reference to FIG.

As shown in the figure, an intake pipe 1 of a supercharged engine includes an air cleaner 2 for purifying intake air, a compressor 4 for a turbocharger 3 that pressurizes and discharges intake air in accordance with rotation, and intake air. A throttle valve 5 for adjusting the amount and an intercooler 6 for cooling intake air that has become hot due to compression by the compressor 4 are installed. The intake pipe 1 is connected to an intake port 9 of each cylinder formed in a cylinder head 8 of a supercharged engine via an intake manifold 7 that distributes intake air to each cylinder. In this supercharged engine, an intake passage is constituted by the intake pipe 1, the intake manifold 7 and the intake port 9.

On the other hand, the cylinder head 8 is formed with an exhaust port 12 for each cylinder. The exhaust port 12 is connected to the exhaust pipe 10 via an exhaust manifold 11 that joins the exhaust gases of the cylinders. The exhaust pipe 10 is provided with an exhaust turbine 13 of a turbocharger 3 for rotating the compressor 4 by the flow of exhaust gas to be blown, and a catalytic converter 14 for purifying exhaust gas is disposed downstream thereof. In this supercharged engine, an exhaust passage is constituted by the exhaust port 12, the exhaust manifold 11 and the exhaust pipe 10.

A blow-by gas passage 18 for communicating the crankcase 16 and the head cover 17 is formed in the cylinder head 8 and the cylinder block 15 of the supercharged engine. A first PCV hose 20 is connected to the head cover 17 via a first PCV (Positive Crankcase Ventilation) valve 19. The first PCV hose 20 communicates the inside of the head cover 17 with the intake manifold 7.

Furthermore, in the blow-by gas reduction device of the present embodiment, a bypass passage 21 that connects a portion of the intake pipe 1 downstream of the intercooler 6 and a portion of the intake pipe 1 upstream of the compressor 4 is provided. An ejector pump 22 as a negative pressure generator is installed on the bypass passage 21. A second PCV hose 24 is further connected to the ejector pump 22. The tip of the second PCV hose 24 is connected to the head cover 17 via the second PCV valve 23.

Next, the configuration of the ejector pump 22 will be described with reference to FIG. As shown in the figure, the ejector pump 22 includes a substantially cylindrical nozzle portion 25 that is connected to a downstream portion of the intercooler 6 in the intake pipe 1 via a bypass passage 21. A nozzle 26 is formed at the tip of the nozzle portion 25, and the tip is opened in the decompression chamber 27. The decompression chamber 27 is connected to a portion of the intake pipe 1 upstream of the compressor 4 via the bypass passage 21. A suction port 28 is opened at the side of the decompression chamber 27. The suction port 28 is connected to the inside of the head cover 17 through the second PCV hose 24, and thus to the crankcase 16 through the blow-by gas passage 18.

Subsequently, the operation of the present embodiment configured as described above will be described.

When the turbocharger 3 is not supercharged, a negative pressure is formed at the downstream side of the throttle valve 5 in the intake passage. At this time, the blow-by gas is sucked by the negative pressure and introduced from the crankcase 16 into the intake manifold 7 through the blow-by gas passage 18, the inside of the head cover 17, and the first PCV hose 20.

On the other hand, at the time of supercharging by the turbocharger 3, the pressure in the downstream portion of the compressor 4 increases in the intake passage, and the negative pressure is generated in the upstream portion of the compressor 4. Then, due to the differential pressure between the upstream side of the compressor 4 and the downstream side of the intercooler 6, intake air (fresh) passes from the portion of the intake pipe 1 downstream of the intercooler 6 through the bypass passage 21 to the portion of the intake pipe 1 upstream of the compressor 4. Air) starts to flow.

Thus, when the intake air flows through the bypass passage 21, the intake air flowing from the downstream of the intercooler 6 is ejected from the nozzle 26 of the ejector pump 22. Then, the inside of the decompression chamber 27 is decompressed by the flow of the intake air ejected from the nozzle 26. Thus, when a negative pressure is formed in the decompression chamber 27, suction by the negative pressure causes the crankcase 16 to pass through the blow-by gas passage 18, the inside of the head cover 17, the second PCV hose 24, and the suction port 28 to the decompression chamber 27. Blow-by gas is introduced. The blow-by gas introduced into the decompression chamber 27 flows along with the intake air flowing through the bypass passage 21 to the portion of the intake pipe 1 on the upstream side of the compressor 4.

Since the intake air is introduced into the bypass passage 21 at this time from the downstream of the intercooler 6 that cools the intake air, low-temperature intake air is introduced into the ejector pump 22. In addition, intake air is introduced into the bypass passage 21 through the intercooler 6 having a complicated labyrinth structure, and most of the oil mist mixed in the intake air is collected in the intercooler 6, so that the bypass passage Inflow of oil into 21 is limited.

In this embodiment, as the supercharging rate increases, the differential pressure across the bypass passage 21 increases, and the flow of intake air flowing through the bypass passage 21 increases. As a result, the flow rate of blow-by gas sucked by the ejector pump 22 increases. Therefore, for example, if the ejector pump 22 is designed so that a blow-by gas having a required flow rate is secured when the differential pressure between the intake pressure of the intake manifold 7 and the atmospheric pressure is “0”, the following problem occurs. That is, if blow-by gas is introduced in this case, the negative pressure formed by the ejector pump 22 is excessively reduced when the supercharging rate becomes high, as shown by the dotted line in FIG. The flow rate of blow-by gas becomes excessive. As a result, a large amount of oil mist is introduced into the intake air together with blow-by gas, so that proper ventilation cannot be performed.

In that respect, in the present embodiment, the flow rate of blow-by gas sucked into the decompression chamber 27 of the ejector pump 22 through the second PCV hose 24 can be adjusted by the second PCV valve 23. Therefore, when the supercharging rate is high, the second PCV valve 23 is throttled, and the flow rate of blow-by gas sucked into the decompression chamber 27 of the ejector pump 22 through the second PCV hose 24 is limited, so that it is suitable for ventilation. The flow rate of blow-by gas returned to the feed engine can be appropriately adjusted.

According to the present embodiment described above, the following effects can be achieved.

(1) In the present embodiment, the bypass passage 21 connecting the downstream portion of the intercooler 6 in the intake passage and the upstream portion of the compressor 4 in the intake passage, and the flow rate of the intake air flowing through the bypass passage 21 And an ejector pump 22 that sucks blow-by gas by the generated negative pressure. In this embodiment, since the intake air cooled by the intercooler 6 is introduced into the bypass passage 21, the ejector pump 22 is not required to have high heat resistance. In addition, since the temperature of the flowing intake air is low and the second PCV hose 24 does not reach a high temperature, it is not necessary to take measures against heat shielding to a wire harness or the like disposed in the vicinity thereof. Further, intake air is introduced into the bypass passage 21 from the downstream side of the intercooler 6 having a complicated labyrinth structure, and the oil content contained in the intake air is collected by the intercooler 6, so that the oil content introduced together with the blow-by gas Inflow to the bypass passage 21 is also limited. Therefore, according to the present embodiment, it is possible to easily ensure durability and suppress deposit deposition while enabling reduction of the preferred blow-by gas during supercharging.

(2) In the present embodiment, the second PCV valve 23 for adjusting the amount of blow-by gas sucked by the ejector pump 22 is provided. Therefore, even when the supercharging rate is high, the flow rate of blow-by gas returned to the supercharged engine can be appropriately adjusted so as to be suitable for ventilation.

Note that the above embodiment can be implemented with the following modifications.

In the above embodiment, the second PCV valve 23 that adjusts the amount of blow-by gas sucked by the ejector pump 22 is provided. However, when it is not necessary to control the amount of blow-by gas sucked by the ejector pump 22 The second PCV valve 23 may be omitted.

In the above-described embodiment, the ejector pump 22 is used. However, any negative pressure generator of the ejector pump 22 may be used as long as it is a negative pressure generator that generates negative pressure by the flow of intake air flowing through the bypass passage. Can be adopted instead. For example, a device that swirls the intake air in a spiral shape and sucks blow-by gas using the negative pressure formed at the center of the vortex can be used as the negative pressure generator.

DESCRIPTION OF SYMBOLS 1 ... Intake pipe, 2 ... Air cleaner, 3 ... Turbocharger, 4 ... Compressor, 5 ... Throttle valve, 6 ... Intercooler, 7 ... Intake manifold, 8 ... Cylinder head, 9 ... Intake port, 10 ... Exhaust pipe, 11 ... Exhaust manifold, 12 ... exhaust port, 13 ... exhaust turbine, 14 ... catalytic converter, 15 ... cylinder block, 16 ... crankcase, 17 ... head cover, 18 ... blow-by gas passage, 19 ... first PCV valve, 20 ... first PCV hose, DESCRIPTION OF SYMBOLS 21 ... Bypass passage, 22 ... Ejector pump, 23 ... 2nd PCV valve, 24 ... 2nd PCV hose, 25 ... Nozzle part, 26 ... Nozzle, 27 ... Decompression chamber, 28 ... Suction port.

Claims

A compressor rotated by an exhaust turbine and an intercooler for cooling intake air discharged from the compressor are applied to a supercharged engine provided in the intake passage, and blow-by gas generated in the supercharged engine is shared through the intake air. A blow-by gas reduction device that returns to a supercharged engine,
A bypass passage connecting a portion of the intake passage downstream of the intercooler and a portion of the intake passage upstream of the compressor;
A negative pressure generator that generates a negative pressure by a flow of intake air flowing through the bypass passage, and sucks the blow-by gas by the negative pressure;
A blow-by gas reduction device for a supercharged engine.
The blow-by gas reduction device for a supercharged engine according to claim 1, further comprising a valve that adjusts an amount of the blow-by gas sucked by the negative pressure generator.
The blow-by gas reduction device for a supercharged engine according to claim 1, wherein the negative pressure generator is an ejector pump.