JP6939464B2 - Blow-by gas reduction system - Google Patents

Description

The present disclosure relates to a blow-by gas reduction system.

Conventionally, a blow-by gas reduction device for reducing blow-by gas discharged from an engine to an intake system of an engine is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-246801

By the way, as a blow-by gas reduction device, an oil separator into which the blow-by gas discharged from the engine is introduced, a reduction gas passage for reducing the blow-by gas after passing through the oil separator to the intake system of the engine, and an oil separator from the blow-by gas. A type of blow-by gas reduction device having an oil return passage for introducing the separated oil into the crankcase of the engine may be used. A check valve is arranged in this oil return passage, and in this check valve, the pressure on the crankcase side (crank case side pressure) of the check valve in the oil return passage is the check valve in the oil return passage. When the pressure on the oil separator side (oil separator side pressure) is greater than that, the valve is closed.

In the case of an engine to which such a blow-by gas reduction device is applied, the pressure on the crankcase side becomes lower than the pressure on the oil separator side due to the pressure fluctuation in the crankcase during the idling operation of the engine, and the check valve is opened. There is a risk of becoming. When the check valve is opened during idling operation in this way, the gas in the crankcase may flow back into the oil return passage for some reason. In this case, the phenomenon in which the backflowing gas flows back through the oil return passage together with the oil existing in the oil return passage and is blown up to the side of the oil separator (hereinafter, this is referred to as "backflow phenomenon in the oil return passage"). ) May occur.

The present disclosure has been made in view of the above, and an object of the present invention is to provide a blow-by gas reduction system capable of suppressing a backflow phenomenon in an oil return passage during idling operation of an engine.

In order to achieve the above object, the blow-by gas reduction system according to the aspect of the present invention uses an oil separator into which the blow-by gas discharged from the engine is introduced and the blow-by gas after passing through the oil separator into the intake system of the engine. A blow-by gas reduction device having a reduction gas passage for reducing the amount of oil to the engine and an oil return passage for introducing the oil separated from the blow-by gas by the oil separator into the crank case of the engine, and a control device for controlling the engine. A check valve is arranged in the oil return passage, and the check valve has a crank case side pressure which is a pressure on the crank case side of the check valve in the oil return passage. The valve is closed when the pressure on the oil separator side is larger than the check valve in the oil return passage, and the control device is set to be in the closed state when the engine is idling. When the condition that the pressure on the crank case side is equal to or less than the pressure on the oil separator side is satisfied, the engine speed is increased to be higher than the engine speed when the condition is not satisfied during the idling operation. Starts execution of control processing.

According to the above blow-by gas reduction system, it is possible to prevent the check valve from being closed during the idling operation of the engine and causing a backflow phenomenon in the oil return passage.

It is a block diagram which shows typically the structure of the blow-by gas reduction system which concerns on embodiment. This is an example of a flowchart of control processing executed by the control device.

FIG. 1 is a configuration diagram schematically showing the configuration of the blow-by gas reduction system 1 according to the present embodiment. This blow-by gas reduction system 1 is applied to the engine 100 mounted on the vehicle. The specific type of this vehicle is not particularly limited, but in the present embodiment, a commercial vehicle such as a bus or a truck is used as an example. The specific type of the engine 100 is not particularly limited, but in the present embodiment, a diesel engine is used as an example.

Further, the engine 100 includes an engine main body 101 and a crankcase 102. The engine body 101 includes a cylinder block, a cylinder head arranged above the cylinder block, a piston arranged in a cylinder (cylinder) formed in the cylinder block, a crank shaft connected to the piston via a conrod, and a cylinder. It is equipped with a fuel injection device that injects fuel into the combustion chamber of the cylinder. The crankcase 102 is a case in which the crankshaft is housed. The crankcase 102 is arranged at the bottom of the cylinder block.

The structure of the engine 100 itself is general. In such an engine 100, the pressure inside the crankcase 102 (that is, the internal pressure of the crankcase 102) tends to increase as the engine speed increases.

The blow-by gas reduction system 1 includes a blow-by gas reduction device 10, sensors, and a control device 30 that controls the engine 100. In FIG. 1, the rotation speed sensor 20 and the pressure sensors 21a and 21b are exemplified as an example of these sensors.

The blow-by gas reduction device 10 includes an oil separator 11, a check valve 12, a blow-by gas passage 13, a reduction gas passage 14, and an oil return passage 15. The blow-by gas passage 13 communicates with the blow-by gas discharge port provided in the engine 100 and the blow-by gas inlet of the oil separator 11, and is a pipe for introducing the blow-by gas discharged from the engine 100 into the oil separator 11. be.

The blow-by gas discharge port of the engine 100 may be formed as long as it can discharge blow-by gas, and the specific formation location is not limited, but the blow-by gas discharge port according to the present embodiment is not limited. As an example, it is formed on the cylinder head portion of the engine 100. Further, the blow-by gas according to the present embodiment is specifically a gas in which the gas in the combustion chamber of the engine 100 leaks into the crankcase 102 from the gap between the piston and the cylinder. The blow-by gas discharge port communicates with the inside of the crankcase 102 inside the engine 100. The blow-by gas discharge port may be provided, for example, in the portion of the crankcase 102.

The oil separator 11 is a device for separating oil contained in blow-by gas. The specific configuration of the oil separator 11 is not particularly limited as long as it has such a function, and a known oil separator capable of separating oil in gas is used as the oil separator 11. Can be done. Therefore, further detailed description of the oil separator 11 will be omitted.

The reduction gas passage 14 communicates the blow-by gas discharge port of the oil separator 11 with the intake system 103 of the engine 100, and blow-by gas after passing through the oil separator 11 (that is, blow-by gas after the oil is separated). ) Is introduced into the intake system 103. In the present embodiment, the intake passage of the engine 100 is used as a specific example of the intake system 103.

The oil return passage 15 communicates the oil discharge port of the oil separator 11 with the oil return port provided in the crankcase 102 of the engine 100, and the oil separated from the blow-by gas by the oil separator 11 is transferred to the crankcase 102. It is a pipe to be introduced in.

The oil return passage 15 according to the present embodiment is set so that its above-ground height becomes lower in general (that is, as a whole) from the side of the oil separator 11 toward the side of the crankcase 102. There is. Therefore, the oil separated by the oil separator 11 is mainly subjected to the action of gravity, flows through the oil return passage 15, and is introduced into the crankcase 102.

The check valve 12 is arranged in the oil return passage 15. In this check valve 12, the pressure on the crankcase 102 side of the check valve 12 in the oil return passage 15 (hereinafter, referred to as “crankcase side pressure”) is higher than that of the check valve 12 in the oil return passage 15. The valve is closed when the pressure is higher than the pressure on the oil separator 11 side (hereinafter referred to as "oil separator pressure"). Conversely, the check valve 12 is in the valve open state when the pressure on the crankcase side is equal to or lower than the pressure on the oil separator side.

The check valve 12 is in a closed state while the vehicle is traveling. Specifically, while the vehicle is running, the engine speed is higher than the speed during idling operation. In this case, since the pressure inside the crankcase 102 is sufficiently high, the pressure on the crankcase side becomes larger than the pressure on the oil separator side. As a result, the check valve 12 is closed. When the check valve 12 is closed in this way, the gas flowing back from the crankcase 102 flows back through the oil return passage 15 together with the oil existing in the oil return passage 15 to the side of the oil separator 11. It is suppressed that the "backflow phenomenon in the oil return passage" that is blown up occurs. Further, when the check valve 12 is closed in this way, the oil separated by the oil separator 11 cannot flow to the crankcase 102 side of the check valve 12 in the oil return passage 15. Therefore, it stays inside the oil separator 11 or in a portion on the oil separator 11 side of the check valve 12 in the oil return passage 15.

On the other hand, when the operation of the engine 100 is stopped (when the engine speed becomes zero), the pressure inside the crankcase 102 decreases, and the pressure on the crankcase side becomes equal to or lower than the pressure on the oil separator side. As a result, the check valve 12 is opened. In this case, the oil passes through the oil return passage 15 and is introduced into the crankcase 102.

The rotation speed sensor 20 detects the engine rotation speed (specifically, the rotation speed of the crankshaft of the engine 100; rpm) and transmits the detection result to the control device 30.

The pressure sensor 21a detects the pressure on the crankcase 102 side of the check valve 12 in the oil return passage 15 (that is, the crankcase side pressure; Pa), and transmits this detection result to the control device 30. The pressure sensor 21b detects the pressure on the oil separator 11 side of the check valve 12 in the oil return passage 15 (that is, the oil separator side pressure; Pa), and transmits this detection result to the control device 30.

The control device 30 is a control device that integrally controls the operation of the engine 100. As such a control device 30, an electronic control device is used in this embodiment. This electronic control device includes a CPU (Central Processing Unit) that functions as a control unit, and a storage unit that stores data, programs, and the like used in the operation of the CPU. As this storage unit, a ROM (Read Only Memory), a RAM (Random Access Memory), or the like is used.

FIG. 2 is an example of a flowchart of the control process executed by the control device 30. The control device 30 repeatedly executes the flowchart of FIG. 2 at a predetermined cycle at the same time as the start of the engine 100 is started. Further, each step in FIG. 2 is specifically executed by the CPU of the control device 30.

In step S10, the control device 30 determines whether or not the engine 100 is idling. The idling operation means that the engine 100 is operating with no load. Specifically, in the present embodiment, the engine 100 is operating with the accelerator pedal depression amount being zero. To say. Normally, the control device 30 injects fuel from the engine 100 so that the engine speed (rpm) becomes a preset predetermined idling speed (referred to as "reference idling speed") during this idling operation. The amount etc. is controlled. If NO is determined in step S10, the control device 30 re-executes the flowchart from the start (return).

On the other hand, if YES is determined in step S10 (that is, when the engine 100 is idling), the control device 30 determines whether or not a predetermined predetermined start condition set in advance is satisfied (step S20). .. In this embodiment, the condition that the pressure on the crankcase side is equal to or less than the pressure on the oil separator side is used as the start condition according to step S20.

In this case, in step S20, the control device 30 determines whether or not the crank case side pressure acquired based on the detection result of the pressure sensor 21a is equal to or less than the oil separator side pressure acquired based on the detection result of the pressure sensor 21b. As a result, when it is determined that the pressure on the crankcase side is equal to or less than the pressure on the oil separator side, it is determined that the start condition is satisfied (YES).

When NO is determined in step S20 (that is, when the pressure on the crankcase side is larger than the pressure on the oil separator side), the control device 30 maintains control of the engine speed to the reference idling speed (step S30). ). That is, in this case, the engine speed does not increase and remains at the reference idling speed. Next, the control device 30 executes the flowchart again from the start (return).

On the other hand, if YES is determined in step S20 (that is, when the pressure on the crankcase side is equal to or less than the pressure on the oil separator side), the control device 30 starts executing the rotation speed increase control process (step S40). In this rotation speed increase control process, the control device 30 increases the engine speed from the engine speed (that is, the reference idling speed) when the start condition is not satisfied during idling operation.

As described above, in the engine 100, the higher the engine speed, the higher the pressure in the crankcase 102. Therefore, the pressure in the crankcase 102 can be increased by increasing the engine speed in step S40. As a result, the pressure on the crankcase side can be increased to close the check valve 12.

The target engine speed (that is, the target engine speed) of the speed increase control process according to step S40 may be a value higher than the reference idling speed, and the specific value thereof is particularly limited. However, it may be set based on, for example, the following viewpoints.

Specifically, the higher the target engine speed in step S40, the higher the pressure in the crankcase 102 can be. On the other hand, the lower the target engine speed in step S40, the more the deterioration of fuel consumption due to the execution of step S40 can be suppressed. Therefore, as an example of the target engine speed in step S40, the engine speed should be as low as possible within the range of the engine speed such that the pressure in the crankcase 102 is such that the check valve 12 can be maintained in the closed state. It may be used. As a result, the check valve 12 can be closed while suppressing the deterioration of fuel consumption due to the execution of step S40 as much as possible. The target engine speed is obtained in advance by an experiment, a simulation, or the like, and is stored in a storage unit (for example, ROM or the like) of the control device 30. The control device 30 controls the engine 100 so that the engine speed detected by the speed sensor 20 becomes the target engine speed of the storage unit.

After step S40, the control device 30 determines whether or not a predetermined preset end condition is satisfied (step S50). As an example of this end condition, in this embodiment, the condition that the pressure on the crankcase side is larger than the pressure on the oil separator side is used. Specifically, the control device 30 determines whether or not the crank case side pressure acquired based on the detection result of the pressure sensor 21a is larger than the oil separator side pressure acquired based on the detection result of the pressure sensor 21b. As a result, when it is determined that the pressure on the crankcase side is larger than the pressure on the oil separator side, it is determined that the end condition is satisfied (YES). This step S50 is repeatedly executed until it is determined to be YES.

If YES is determined in step S50, the control device 30 ends the execution of the rotation speed increase control process (step S60). That is, the rotation speed increase control process according to the present embodiment is executed until the pressure on the crankcase side becomes larger than the pressure on the oil separator side.

Specifically, in step S60, the control device 30 returns the engine speed to the reference idling speed. After the execution of step S60, the control device 30 re-executes the flowchart from the start (return).

According to the present embodiment as described above, the following effects can be obtained. First, according to the present embodiment, when the start condition that the crankcase side pressure is equal to or lower than the oil separator side pressure is satisfied during the idling operation of the engine 100 (when YES in step S20), step S40 is performed. By starting the execution of the rotation speed increase control process, the engine speed can be increased more than the engine speed (reference idling speed) when the start condition is not satisfied during the idling operation. As a result, the pressure inside the crankcase 102 can be increased, so that the check valve 12 can be closed, and thus the backflow phenomenon in the oil return passage can be suppressed. can.

Further, according to the present embodiment, since the rotation speed increase control process according to step S40 is executed until the crankcase side pressure becomes larger than the oil separator side pressure (step S60), the rotation speed increase control process is useless. The check valve 12 can be closed while suppressing the operation for a long time. As a result, it is possible to suppress the deterioration of fuel consumption due to the wastefully executing the rotation speed increase control process for a long time, and to suppress the occurrence of the backflow phenomenon in the oil return passage.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. Is possible.

1 Blow-by gas reduction system 10 Blow-by gas reduction device 11 Oil separator 12 Check valve 13 Blow-by gas passage 14 Reduction gas passage 15 Oil return passage 20 Speed sensor 21a, 21b Pressure sensor 30 Control device 100 Engine 102 Crankcase 103 Intake system

Claims (2)

The blow-by gas was separated from the blow-by gas by an oil separator into which the blow-by gas discharged from the engine was introduced, a reducing gas passage for reducing the blow-by gas after passing through the oil separator to the intake system of the engine, and the oil separator. A blow-by gas reduction device having an oil return passage for introducing oil into the crankcase of the engine, and a blow-by gas reduction device.
A control device for controlling the engine is provided.
A check valve is arranged in the oil return passage.
In the check valve, the crankcase side pressure, which is the pressure on the crankcase side of the check valve in the oil return passage, is the pressure on the oil separator side of the check valve in the oil return passage. It is set to close when the pressure is higher than a certain oil separator side pressure.
When the condition that the pressure on the crankcase side is equal to or lower than the pressure on the oil separator side is satisfied during the idling operation of the engine, the control device satisfies the engine rotation speed and the condition is satisfied during the idling operation. A blow-by gas reduction system that initiates execution of a speed increase control process that increases the engine speed above the engine speed if not. The blow-by gas reduction system according to claim 1, wherein the control device executes the rotation speed increase control process until the pressure on the crankcase side becomes larger than the pressure on the oil separator side.

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