Engine system

Abstract

To provide an engine system that suppresses a backflow of oil from an engine to an oil tank with the engine stopped.SOLUTION: An engine system includes: an engine; an oil tank that stores oil for lubricating the engine; oil piping for causing the oil to flow from the oil tank to the engine and causing blow-by gas to flow from the engine to the oil tank; blow-by gas piping for causing the blow-by gas to flow from the oil tank to an intake pipe of the engine; a check valve provided in the blow-by gas piping and allowing circulation of the blow-by gas from the oil tank to the intake pipe but restricts circulation of the blow-by gas in a reverse direction; an atmosphere release pipe for releasing atmospheric air in the oil tank; an on-off valve for opening / closing the atmosphere release pipe; and a control device for opening the on-off valve when pressure in the oil tank is lower than a predetermined negative pressure value with the engine stopped.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an engine system. [Background technology]

[0002] An oil tank that stores oil for lubricating the engine is connected to the engine via an oil pipe, and is connected to a portion of the intake pipe downstream of the throttle valve via a blow-by gas pipe (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-038839 Summary of the Invention [Problem to be solved by the invention]

[0004] If there is negative pressure inside the oil tank when the engine is stopped, oil may flow back from the engine into the oil tank, causing abnormal noise.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine system that suppresses backflow of oil from the engine to the oil tank when the engine is stopped. [Means for solving the problem]

[0006] The above object can be achieved by an engine system comprising: an engine; an oil tank storing oil for lubricating the engine; an oil piping for flowing the oil from the oil tank to the engine and for flowing blow-by gas from the engine to the oil tank; a blow-by gas piping for flowing the blow-by gas from the oil tank to an intake pipe of the engine; a check valve provided in the blow-by gas piping for allowing the flow of the blow-by gas from the oil tank to the intake pipe but regulating the flow of the blow-by gas in the opposite direction; an atmosphere release pipe for opening the inside of the oil tank to the atmosphere; an opening / closing valve for opening and closing the atmosphere release pipe; and a control device for opening the opening / closing valve when the pressure in the oil tank is lower than a predetermined negative pressure value while the engine is stopped.

[0007] The control device may be provided with a battery that charges with electricity generated by the operation of the engine, and the opening / closing valve may be driven by electricity from the battery, and when the voltage of the battery is equal to or higher than a predetermined value and the pressure is lower than the predetermined negative pressure value while the engine is stopped, the control device may open the opening / closing valve.

[0008] The control device may open the on-off valve when the pressure is higher than a predetermined positive pressure value while the engine is running.

[0009] The control device may periodically open the on-off valve while the engine is operating.

[0010] The control device may maintain the on-off valve in a half-open state while the engine is operating. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an engine system that suppresses backflow of oil from the engine to the oil tank when the engine is stopped. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of an engine system. [Figure 2] 4 is a flowchart illustrating an example of pressure control of an oil tank executed by an ECU. [Figure 3] 10 is a flowchart of a modified example of oil tank pressure control executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a schematic diagram of an engine system. The engine system is mounted on, for example, a vehicle. The engine system includes an engine 1, an oil tank 10, and an ECU (Electronic Control Unit) 20. The engine 1 includes banks 2L and 2R and a cylinder block 3. That is, the engine 1 is a so-called V-engine, but it may also be an in-line engine. Furthermore, the engine 1 is a gasoline engine, but it may also be a diesel engine. A crankshaft 3a is rotatably provided in the cylinder block 3.

[0014] Banks 2L and 2R each have a plurality of cylinders. Intake pipes 4L and 4R are connected to banks 2L and 2R, respectively. From upstream to downstream, intake pipes 4L and 4R are provided with compressors 5L and 5R, throttle valves 6L and 6R, and surge tanks 7L and 7R, respectively. An exhaust passage is connected to banks 2L and 2R, respectively.

[0015] The ECU 20 is mainly composed of a computer including a CPU (Central Processing Unit), volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 20 is an example of a control device for an engine system. The ECU 20 controls the on-off valve 18, which will be described later.

[0016] The ECU 20 is connected to an ignition switch 21, a pressure sensor 22, and a voltage sensor 23. The ignition switch 21 detects the on / off state of the ignition. The pressure sensor 22, which will be described in detail later, detects the pressure in the gas-filled space in the oil tank 10. The voltage sensor 23 detects the voltage of the battery 30. The ECU 20 also adjusts the opening of the throttle valves 6L and 6R depending on the operating state of the engine 1. The battery 30 is charged with regenerative electric power generated by the operation of the engine 1. The regenerative electric power is charged to the battery 30 from an alternator that operates in conjunction with the operation of the engine 1.

[0017] The oil tank 10 is a dry sump tank that stores oil for lubricating the engine 1. The oil tank 10 is connected to the cylinder block 3 of the engine 1 via an oil pipe 10a. When the scavenging pump P is driven, the oil used by the engine 1 flows into the oil tank 10 via the oil pipe 10a. Blow-by gas generated within the engine 1 also flows into the oil tank 10 via the oil pipe 10a. The scavenging pump P is a mechanical oil pump that is driven in conjunction with the rotation of the crankshaft 3a of the engine 1. The oil stored in the oil tank 10 is pressure-fed to the lubrication parts of the engine 1 by a feed pump (not shown).

[0018] An oil separator 11 is provided on top of the oil tank 10. The oil separator 11 separates oil from the blow-by gas introduced into the oil tank 10. The oil separated from the blow-by gas is stored in the oil tank 10. The oil separator 11 is provided with two check valves 12L and 12R. A blow-by gas pipe 13L connects the oil separator 11 to bank 2L via the check valve 12L. A blow-by gas pipe 13R connects the oil separator 11 to bank 2R via the check valve 12R. The check valve 12L allows gas to flow from the oil separator 11 to bank 2L but restricts gas to flow from bank 2L to the oil separator 11. The check valve 12R allows gas to flow from the oil separator 11 to bank 2R but restricts gas to flow from bank 2R to the oil separator 11.

[0019] Furthermore, blow-by gas pipes 15L and 15R are connected to the oil separator 11. The blow-by gas pipes 15L and 15R are connected to surge tanks 7L and 7R, respectively. Check valves 14L and 14R are provided on the blow-by gas pipes 15L and 15R, respectively. The check valve 14L allows gas to flow from the oil separator 11 to the surge tank 7L, but restricts gas from flowing from the surge tank 7L to the oil separator 11. The check valve 14R allows gas to flow from the oil separator 11 to the surge tank 7R, but restricts gas from flowing from the surge tank 7R to the oil separator 11.

[0020] The atmosphere release pipe 17 communicates with the oil separator 11 side of the check valve 14R of the blow-by gas pipe 15R and with the intake pipe 4R on the upstream side of the compressor 5R. An on-off valve 18 is provided on the atmosphere release pipe 17. The on-off valve 18 is electromagnetic and controlled by the ECU 20. The on-off valve 18 is a normally closed type that closes when no current is applied. The on-off valve 18 is driven by power supplied from the battery 30. The atmosphere release pipe 17 may also communicate with the oil separator 11 side of the check valve 14L of the blow-by gas pipe 15L and with the intake pipe 4L on the upstream side of the compressor 5L. Furthermore, since one end of the atmosphere release pipe 17 only needs to be open to the atmosphere, it does not have to be connected to either the intake pipe 4L or 4R.

[0021] During natural aspiration, the pressure in the oil tank 10 and oil separator 11 becomes higher than the pressure in the surge tanks 7L and 7R. This opens the check valves 14L and 14R, and the blow-by gas in the oil separator 11 is supplied to combustion in the engine 1 via blow-by gas pipes 15L and 15R. During supercharging, the pressure in the oil tank 10 and oil separator 11 becomes higher than the pressure upstream of the compressors 5L and 5R. This opens the check valves 12L and 12R, and the blow-by gas in the oil separator 11 is supplied to combustion in the engine 1 via blow-by gas pipes 13L and 13R.

[0022] In this way, the scavenging pump P, the oil pipe 10a, and the oil tank 10 recover oil used in the engine 1. In addition, the scavenging pump P, the oil pipe 10a, the oil tank 10, the oil separator 11, and the blow-by gas pipes 13L, 13R, 15L, and 15R return blow-by gas generated within the engine 1 to the engine 1. Therefore, these mechanisms are mechanisms for achieving the recovery of oil and the return of blow-by gas.

[0023] When a request to stop the engine 1 is made, the throttle valves 6L and 6R are relatively small, and the pressure in the surge tanks 7L and 7R is negative. This causes the pressure in the oil tank 10, which is connected to the surge tanks 7L and 7R via the blow-by gas pipes 15L and 15R, to also become negative. The engine 1 may stop in this state. In this case, the pressure in the surge tanks 7L and 7R returns to atmospheric pressure. However, the check valves 12L, 12R, 14L, and 14R may maintain the pressure in the oil tank 10 at negative pressure. This negative pressure in the oil tank 10 may cause oil to flow back from the cylinder block 3 to the oil tank 10 via the oil pipe 10a, potentially resulting in abnormal noise. Furthermore, there is a risk of a shortage of oil in the engine 1 when the engine 1 is subsequently restarted. Therefore, the ECU 20 executes the following control.

[0024] [Oil tank pressure control] FIG. 2 is a flowchart illustrating the pressure control of the oil tank 10 executed by the ECU 20. The ECU 20 determines whether the engine 1 is stopped (step S1). If the answer is Yes in step S1, the ECU 20 determines whether the voltage of the battery 30 is equal to or higher than a predetermined value (step S2). If the answer is No in step S2, the ECU 20 maintains the on-off valve 18 in a closed state (step S10). The battery 30 is not charged while the engine 1 is stopped. Therefore, by limiting the actuation of the on-off valve 18 when the voltage of the battery 30 is equal to or lower than a predetermined value, further decrease in the voltage of the battery 30 is suppressed. If the answer is Yes in step S2, the ECU 20 determines whether a predetermined time has elapsed since the on-off valve 18 was last actuated (step S3). If the answer is No in step S3, the ECU 20 maintains the on-off valve 18 in a closed state (step S10). The on-off valve 18 generates heat when it is actuated. Therefore, by restricting the actuation of the on-off valve 18 when a predetermined time has not elapsed since the on-off valve 18 was last actuated, the on-off valve 18 is prevented from excessively increasing in temperature.

[0025] If the answer is Yes in step S3, the ECU 20 determines whether the pressure in the oil tank 10 is lower than a predetermined negative pressure value (step S4). The predetermined negative pressure value is set to a negative pressure value at which oil flows into the oil tank 10 through the oil pipe 10a when the engine 1 is stopped. That is, the ECU 20 determines whether oil flows into the oil tank 10 when the engine 1 is stopped. If the answer is No in step S4, the ECU 20 maintains the on-off valve 18 in a closed state (step S10).

[0026] If the answer is Yes in step S4, the ECU 20 opens the on-off valve 18 (step S5). As a result, the oil tank 10 and the oil separator 11 communicate with the atmosphere via the atmosphere release pipe 17 and the intake pipe 4R. As a result, the pressure in the oil tank 10 increases. Next, the ECU 20 executes step S4 again. If the answer is No in step S4, the ECU 20 closes the on-off valve 18 (step S10). This prevents the backflow of oil from the engine 1 to the oil tank 10 as described above.

[0027] If the answer to step S1 is No, i.e., if the engine 1 is running, the ECU 20 determines whether the pressure in the oil tank 10 is higher than a predetermined positive pressure value (step S6). If the answer to step S6 is Yes, the ECU 20 opens the on-off valve 18 (step S7). This allows the oil tank 10 and the oil separator 11 to communicate with the atmosphere via the atmosphere release pipe 17 and the intake pipe 4R. As a result, the pressure in the oil tank 10 decreases. This allows the pressure in the oil tank 10 to decrease even if, for example, at least one of the check valves 12L, 12R, 14L, and 14R becomes unable to open, causing the pressure in the oil tank 10 to become high. As a result, excessive load on the oil tank 10 is suppressed. Next, the ECU 20 executes step S6 again.

[0028] If the answer is No in step S6, the ECU 20 determines whether it is time to open the on-off valve 18 (step S8). Whether it is time to open the on-off valve 18 is determined based on, for example, the time measured by an internal counter of the ECU 20 from the start of the engine 1. If the answer is No in step S8, the ECU 20 closes the on-off valve 18 (step S10). If the answer is Yes in step S8, the ECU 20 opens the on-off valve 18 for a predetermined time (step S9). Thereafter, the ECU 20 closes the on-off valve 18 (step S10). In this way, the ECU 20 opens and closes the on-off valve 18 at a predetermined cycle. This prevents the pressure in the oil tank 10 from becoming excessively positive or negative during operation of the engine 1, for example. It is desirable that the on-off valve 18 be opened and closed at a cycle that does not interfere with the flow of blow-by gas from the oil separator 11 to the intake pipes 4L and 4R.

[0029] [Variations] 3 is a flowchart of a modified example of pressure control of the oil tank 10 executed by the ECU 20. In this modified example of pressure control, the opening of the on-off valve 18 is controlled in accordance with the duty ratio of the applied voltage. For example, when the duty ratio is 100%, the on-off valve 18 is fully open with an opening of 100%. When the duty ratio is 0%, the on-off valve 18 is fully closed with an opening of 0%. Furthermore, heat generation from the on-off valve 18 is suppressed even when it is always open.

[0030] If the answer is Yes in step S4 or S6, the ECU 20 controls the duty ratio of the voltage applied to the on-off valve 18 to 100%, thereby setting the opening degree of the on-off valve 18 to 100% (steps S5a and S7a).

[0031] If the answer is No in step S6, the ECU 20 controls the duty ratio of the voltage applied to the on-off valve 18 to a predetermined value less than 100% and greater than 0%, thereby controlling the opening degree of the on-off valve 18 to A% (step S8a). Here, A% is a value less than 100% and greater than 0%. In other words, the on-off valve 18 is maintained in a half-open state. That is, the on-off valve 18 is always maintained in a half-open state while the engine 1 is operating. This prevents the pressure in the oil tank 10 from becoming excessively positive or negative while the engine 1 is operating. Note that the opening degree A% of the on-off valve 18 is preferably set to a value that does not interfere with the flow of blow-by gas from the oil separator 11 to the intake pipes 4L and 4R. For example, the opening degree A% is 10%.

[0032] In the above embodiment, the pressure sensor 22 detects the pressure inside the oil tank 10, but this is not limiting. For example, the ECU 20 may estimate the pressure inside the oil tank 10 depending on the operating state of the engine 1.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0034] 1 engine 4L, 4R intake pipe 10 Oil Tank 11 Oil separator 12L, 12R, 14L, and 14R check valves 13L, 13R, 15L, 15R Blow-by gas piping 17 Atmospheric release pipe 18 On-off valve 20 ECU (control unit) 30 Battery

Claims

1. The engine and an oil tank that stores oil for lubricating the engine; an oil pipe for allowing the oil to flow from the oil tank to the engine and for allowing blow-by gas to flow from the engine to the oil tank; a blow-by gas pipe for allowing the blow-by gas to flow from the oil tank to an intake pipe of the engine; a check valve that is provided in the blow-by gas piping and allows the blow-by gas to flow from the oil tank to the intake pipe but restricts the flow of the blow-by gas in the reverse direction; an atmosphere release pipe that opens the inside of the oil tank to the atmosphere; an on-off valve that opens and closes the atmosphere release pipe; a control device that opens the on-off valve when the pressure in the oil tank is lower than a predetermined negative pressure value while the engine is stopped; An engine system with.

2. a battery that is charged with power generated by driving the engine; the on-off valve is driven by power from the battery, 2. The engine system according to claim 1, wherein the control device opens the on-off valve when the voltage of the battery is equal to or higher than a predetermined value and the pressure is lower than the predetermined negative pressure value while the engine is stopped.

3. 3. The engine system according to claim 1, wherein the control device opens the on-off valve when the pressure is higher than a predetermined positive pressure value during operation of the engine.

4. 3. The engine system according to claim 1, wherein the control device periodically opens the on-off valve while the engine is operating.

5. 3. The engine system according to claim 1, wherein the control device maintains the on-off valve in a half-open state while the engine is operating.

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