JPH06257418A - Blow-by gas reducing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a blow-by gas reducing device for internal combustion engine capable of maintaining the inside of a crankcase under negative pressure at all times over all operating ranges. CONSTITUTION:A blow-by gas reducing device for internal combustion engine is provided with an air introducing passage 13 connecting the upstream side part of a throttle valve 11 of an intake passage to the inside of a cylinder-head cover 4 of an engine, a blow-by gas exhaust passage 14 connecting the inside of the cylinder-head cover 14 to the downstream side part of the throttle valve 11 of the intake passage 6, and a PCV valve 15 provided in the exhaust passage 14 to control the flow rate of blow-by gas in response to the pressure difference between the inside of the cylinder-head cover 4 and the downstream side of the throttle valve. In this case, a part 16 situated on the downstream side of the connection of the air introducing passage with the intake passage 6 and on the upstream side just near the idle position of the throttle valve, and the air introducing passage 13 are connected to each other by a thining-out by-pass- passage 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow-by gas for an internal combustion engine, in which blow-by gas that has entered the crankcase from a combustion chamber or the like is recirculated to the combustion chamber to re-combust and prevent emission to the atmosphere. More particularly, the present invention relates to an improvement of a passage structure capable of maintaining a negative pressure inside a crankcase in a wide operating range of an engine.

[0002]

2. Description of the Related Art Conventionally, an example of an engine blow-by gas returning apparatus using a PCV valve has a structure shown in FIG. The reducing device 20 includes an air cleaner 21.
A portion of the intake passage 22 upstream of the throttle valve 23 and the head cover 26 of the engine 25 are connected by an air introduction passage 29, and are connected to the head cover 26 and the intake passage 22 downstream of the throttle valve 23. The surge tank 30 is connected to a blow-by gas discharge passage 31, and a PCV valve 32 is provided in the discharge passage 31.

The engine 25 has a structure in which a cylinder head 27 and a head cover 26 are laminated and fastened to an upper mating surface of a cylinder block 28 having a crankcase. The inside of the crankcase is a cylinder head via a communication passage 28a. 27 communicates with the inside of the head cover 26.
Although not shown, the surge tank 30 is connected to the cylinder head 27 via an intake manifold and an intake port.
Communicates with the combustion chamber.

As a blow-by gas reducing apparatus of this type, as disclosed in Japanese Patent Laid-Open No. 59-39914, the crankcase and the throttle valve downstream side of the intake passage are directly connected via a PCV valve. Some are in communication.

In the blow-by gas returning apparatus 20, the opening of the PCV valve 32 is large because the negative pressure in the surge tank 30 is large in an operating range where the opening of the throttle valve is small, such as during idling and low speed rotation and low load. As a result, fresh air is introduced into the head cover 26 from the air introduction passage 29 (arrow a), and together with blow-by gas (arrow b) in the crankcase, passes through the discharge passage 31 from the surge tank 30 to the intake manifold. It is sucked into the combustion chamber and burned. Further, at the time of high load, that is, in the operating range in which the opening of the throttle valve 23 is large, the opening of the PCV valve 32 becomes small because the pressures on the upstream side and the downstream side of the throttle valve of the intake passage 22 become substantially the same, which reduces the opening. The blow-by gas in the crankcase mainly flows backward through the air introduction passage 29 (arrow c), is sucked into the intake passage 22, and is burned in the engine.

As described above, the blow-by gas reduction device 2 is used.
No. 0 is designed to ventilate the blow-by gas in the crankcase. However, in order to reliably prevent the blow-by gas from being released into the atmosphere, the crankcase inside the crankcase must be negative in all operating ranges. It is necessary to keep it under pressure. As a means therefor, conventionally, a method is used in which the inner diameter d of the air introduction passage 29, the PCV valve 32, and the like are set to a size and a flow rate characteristic that can obtain the negative pressure state.

[0007]

In the conventional blow-by gas returning apparatus 20 described above, in order to make the inside of the crankcase negative, for example, in the operation range where the PCV valve 32 is wide open such as low speed rotation and low load, air introduction is performed. It is effective to reduce the diameter d of the passage 29 to suppress the introduction of fresh air. On the other hand, in the high load region, it is effective to increase the inner diameter d of the air introduction passage 29 in order to promote ventilation in the crankcase. Since the requirements for the inner diameter d of the air introduction passage 29 are in conflict with each other in this way, an operating region in which the inside of the crankcase cannot be maintained at a negative pressure is likely to occur.

Here, the inner diameter d of the air introduction passage 29 is set to a large diameter according to the high speed rotation and high load operation range, and the PCV valve 3
It is conceivable to set the flow rate of 2 to a large value so that the fresh air and blow-by gas introduced through the large-diameter air introduction passage 29 can be sufficiently discharged. However, if the flow rate is increased in this way, the amount of air from the exhaust passage 31 at the time of idling increases, that is, the amount of air that substantially bypasses the throttle valve 23 increases, and thus the throttle valve is closed. There is a problem that the idling rotation becomes high.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a blow-by gas reducing apparatus for an internal combustion engine, which is capable of keeping a negative pressure in the crankcase at all times in all operating regions.

[0010]

SUMMARY OF THE INVENTION Therefore, according to the present invention, there is provided an air introduction passage communicating between a portion of an intake passage upstream of a throttle valve and the crankcase of an engine, and a throttle valve in the crankcase and the intake passage. Internal combustion equipped with a blow-by gas discharge passage communicating with a downstream side portion, and a PCV valve interposed in the discharge passage and controlling the flow rate of the blow-by gas according to the pressure difference between the inside of the crankcase and the throttle valve downstream side. In a blow-by gas returning apparatus for an engine, a part of the intake passage downstream of the air introduction passage connecting portion and immediately upstream of the throttle valve idle position and the air introduction passage are communicated with each other by an intermediate bypass passage.

Here, in the present invention, the air introduction passage is set to have an inner diameter capable of sufficiently discharging the blow-by gas generated in the crankcase in the high load operation range. The bypass passage is set so that fresh air to the crankcase does not become excessive by bypassing part of the fresh air in the low, medium speed, low, and medium load operating ranges.

In the present invention, communicating the intake passage with the crankcase means connecting the crankcase directly to the intake passage, or connecting the crankcase to the intake passage via a cylinder block, a cylinder head and a head cover. Both are included.

[0013]

According to the blow-by gas reduction device of the present invention,
At low / medium speed / low / medium load, that is, when the throttle valve opening is small, the inter-reference bypass passage opens at the high negative pressure position on the downstream side of the throttle valve. A part of the fresh air will be bypassed into the intake passage through the bypass passage. Therefore, even if the air introduction passage is not set to have a small diameter, the amount of air flowing into the crankcase does not become excessive, and as a result, the inside of the crankcase can be maintained at a negative pressure.

Further, when the load is high, that is, when the throttle valve opening is large, the PCV valve opening becomes small, so the blow-by gas generated in the crankcase flows back through the air introduction passage into the intake passage. Flowing. in this case,
According to the present invention, the blow-by gas flows into the intake passage not only from the air introduction passage but also from the inter-reference bypass passage, so that the blow-by gas can be sufficiently sucked in, and as a result, the inside of the crank case can be reliably maintained even when the throttle valve opening is high. It can be negative pressure.

Furthermore, in the present invention, since it is not necessary to set the flow rate of the PCV valve to a large value, the amount of air that substantially bypasses the throttle valve does not become excessive during idling, and an increase in idling rotation is prevented. it can.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are views for explaining an engine blow-by gas returning apparatus according to an embodiment of the present invention,
1 is a schematic view of the reducing device, FIGS. 2, 3 and 4 are front, side and rear views of the throttle body, FIG. 5 is a sectional view taken along line VV of FIG. 2, and FIG. 6 is FIG. 6 is a sectional view taken along line VI-VI of FIG.

In FIG. 1, reference numeral 1 denotes an engine equipped with a blow-by gas returning apparatus 2 of the present embodiment, which is a cylinder block 5 having a crankcase at a lower portion thereof and a layered fastening on an upper surface of the block 5. The cylinder head 3 and the head cover 4 are provided, and the inner portion of the crankcase communicates with the inside of the cylinder head 3 and the head cover 4 through a communication passage 5a.

Reference numeral 6 denotes an intake device for introducing air into the engine 1, which includes an air cleaner 7, an air cleaner hose 7a, a throttle body 8, an intake pipe 9, a surge tank 10, and an intake air (not shown), which are sequentially arranged from the upstream side. It consists of a manifold. The surge tank 10 is connected to the combustion chamber of each cylinder via an intake manifold and an intake port in the cylinder head 3.

The blow-by gas returning device 2 has an air introduction passage 13 which connects the throttle valve upstream side portion of the throttle body 8 and one end portion of the head cover 4,
A reference bypass passage 17 that communicates the air introduction passage 13 with a portion of the throttle body 8 immediately upstream of the throttle valve idle position, and a blow-by gas discharge passage 14 that communicates the other end of the head cover 4 with the surge tank 10.
And the PCV valve 1 installed in the middle of the discharge passage 14.
It is composed of 5 and.

As shown in FIGS. 2 to 4, the throttle body 8 has the air cleaner hose 7a at the upstream end of the body 8a having a circular intake passage 8d formed therethrough.
, A cylindrical flange 8b connected to the intake pipe 9 is formed at a downstream end, and a throttle valve 11 is rotatably disposed in the intake passage 8d. It is a thing. The throttle valve 11 is a drive shaft 11 arranged in the body main body 8a in a direction perpendicular to the axis.
It is bolted to a. This drive shaft 11
One end of a projects to the outside of the body 8a,
A coil spring 11b for urging the throttle valve 11 in the closing direction and a pulley 11c for driving the throttle valve 11 to open and close are attached to the protruding portion.

Further, a throttle inlet 12a having an inner diameter of about 6 mm and an air inlet 12b having an inner diameter of about 14 mm following the throttle inlet 12a are formed in a portion of the body body 8a upstream of the throttle valve 11. 12b has an inner diameter of 1
The introduction pipe 12c of about 2 mm is press-fitted. The introduction passage 13 is formed by the introduction port 12b, the introduction pipe 12c, and an introduction hose (not shown) connecting the introduction pipe 12c and the head cover 4.

Then, the inner diameter 4 of the body body 8a is opened so as to open in the upstream portion of the body valve 8a immediately near the fully closed position of the throttle valve 11.
A bypass opening 16 having a size of about mm is formed, and the bypass opening 16 is formed in the introduction port 12b of the air introduction passage 13.
Are connected to each other by a bypass passage 17. During this time, the reference bypass passage 17 extends axially downstream from the air introduction port 12b and opens to the end face of the flange portion 8b (see FIG. 5), and the passage portion 17a is followed by the end face of the flange portion 8b. A second groove-shaped second passage 17b (see FIG. 4) extending above the bypass opening 16 and a third passage 17c extending axially from the passage 17b toward the bypass opening 16 in the upstream direction (see FIG. 4). 6)). The second passage 17b is covered by the flange portion of the intake pipe 9 described above. Reference numeral 18 is a plug for closing the outer end opening of the bypass opening 16.

Next, the function and effect of this embodiment will be described. According to the blow-by gas returning apparatus 2 of this embodiment, when the load is high, that is, when the opening of the throttle valve 11 is large, there is almost no pressure difference between the upstream side and the downstream side of the throttle valve 11, so the PCV valve 15 The opening of is almost fully closed. Therefore, the blow-by gas generated in the crankcase passes through the air introduction passage 13 and the throttle body 8
Flows in. In this case, in this embodiment, the blow-by gas flows not only through the air introduction passage 13 but also through the bypass passage 17, so that the blow-by gas is sucked into the throttle body 8 without resistance, and as a result, the high throttle The inside of the crankcase can be reliably maintained in a negative pressure state when the valve is opened. Although the throttle inlet 12a is provided at the inlet of the air introduction passage 13 in the present embodiment, a part of the blow-by gas flows into the throttle body 8 through the inter-reference bypass passage 17, so that it is not seen as a whole. Therefore, the flow path resistance does not become large.

Further, at low speed, medium speed / low speed, medium load, that is, when the throttle valve opening is small (shown by the broken line in FIG. 1).
Means that the inter-reference bypass passage 17 opens to the high negative pressure portion downstream of the throttle valve 11, so that a part of the fresh air flowing into the air introduction passage 13 passes through the inter-reference bypass passage 17 and throttles. It will be bypassed into the body 8. Therefore, it is possible to prevent the amount of air flowing into the head cover 4 from becoming excessive without setting the air introducing passage 13 to a small diameter, and as a result, the negative pressure in the crankcase is achieved while adopting the PCV flow rate characteristic similar to the conventional one. Can be held in a state. Further, in this embodiment, since the throttle portion 12a is provided at the inlet portion of the air introduction passage 13, the amount of fresh air to the air introduction passage 13 can be suppressed also from this point, which is advantageous in securing the above-mentioned negative pressure state.

Furthermore, in this embodiment, the PCV valve 1
Since it is not necessary to set the flow rate of 5 to a large value, the amount of air that substantially bypasses the throttle valve does not become excessively large during idling, and the increase in idling rotation can be prevented.

As described above, according to the present embodiment, in the operating range in which the throttle valve opening is large, the blow-by gas flows into the intake passage through both the air introduction passage 13 and the inter-reference bypass passage 17, so that The blow-by gas generated in the case can be efficiently sucked into the intake passage 8d, and the inside of the crank case can be maintained at a negative pressure. Further, in the operating range where the throttle valve opening is small, the air flowing into the air introduction passage 13 can be thinned out, so that the amount of fresh air flowing into the head cover 4 can be made appropriate and the inside of the crankcase can be maintained at a negative pressure. You can avoid rising.

Here, the engine 1 is provided with an air flow meter for detecting the intake air amount in order to control the A / F. As the air flow meter, a so-called D for detecting the flow rate from the pressure in the intake passage 6 is used.
When the J type is used, since there is no resistance in the intake passage 6, the pressure at the connecting portion of the air introduction passage 13 tends to be close to the atmospheric pressure, so that the air introduction passage 13 is It becomes difficult for the blow-by gas to be sucked into the intake passage. Therefore, when such a D / J type air flow meter is used, it is particularly effective to adopt the passage structure of this embodiment.

Further, in this embodiment, the throttle body 8
Since the bypass opening 16 and the thinning passage 17 are formed integrally with each other, the number of parts is not increased and the cost can be realized.

Although the upstream end of the air introduction passage 13 is connected to the throttle body 8 in the above embodiment, it may be connected to the air cleaner hose 7a. In this case, the same effect as in the above embodiment can be obtained. To be Although the downstream end is connected to the head cover, it may be directly connected to the crankcase 5.

[0030]

As described above, according to the blow-by gas returning apparatus for an internal combustion engine according to the present invention, the upstream portion of the intake passage immediately adjacent to the throttle valve idle position and the air introduction passage are communicated by the bypass bypass passage. Without decreasing the inner diameter of the introduction passage or increasing the flow rate of the PCV valve, it is possible to maintain the negative pressure inside the crankcase in a wide operating region of the engine, and to prevent the blow-by gas from being released into the atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a blow-by gas returning apparatus for an engine according to an embodiment of the present invention.

FIG. 2 is a front view of a throttle body in which a thinning passage is formed in the above embodiment.

FIG. 3 is a side view of the throttle body of the above embodiment.

FIG. 4 is a rear view of the throttle body of the above embodiment.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along the line IV-IV in FIG.

FIG. 7 is a schematic view of a conventional blow-by gas reduction device.

[Explanation of symbols]

 1 Engine (Internal Combustion Engine) 2 Blow-by Gas Return Device 5 Crank Case 6 Intake Passage 11 Throttle Valve 13 Air Intake Passage 14 Blow-by Gas Discharge Passage 15 PCV Valve 17 Inter-reference Bypass Passage

Claims (1)

[Claims] 1. An air introducing passage communicating between an upstream side of a throttle valve of an intake passage and an inside of a crankcase of an engine, and a blow-by gas discharging passage communicating between the inside of the crankcase and a downstream side of the intake passage through a throttle valve. P is provided in the discharge passage and controls the flow rate of blow-by gas according to the pressure difference between the inside of the crankcase and the downstream side of the throttle valve.
In a blow-by gas returning apparatus for an internal combustion engine equipped with a CV valve, a portion of the intake passage downstream of an air introduction passage connecting portion and a portion immediately upstream of a throttle valve idle position and the air introduction passage communicate with each other through an intermediary bypass passage. A blow-by gas reducing apparatus for an internal combustion engine, which is characterized in that: