JP2000204951A - Miller cycle engine and method for cooling supplied air therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely suppress the temperature rise of supplied air by spitting by providing a bypass for connecting an air inlet port to the diffuser part of a supercharger bypassing a cooler, and providing a valve for arresting the passing from the diffuser side to the air inlet port side on this passage. SOLUTION: In the compression stroke of a Miller cycle engine 100, a piston 4 is moved to the top dead center in the state where an intake valve 1 is opened, and an exhaust valve 2 is closed, whereby the air supplied once into a cylinder 3 is spitted to an air inlet port 7. At this time, since one check valve 8 is opened, and the other check valve 9 is closed, the spitted air is sent in the direction of a bypass passage 10. The air guided to the bypass passage 10 is circulated to the upstream side of the cooler 6 through the diffuser part 12 of a supercharger 5. Thus, the supplied air within the air inlet port 7 is regularly cooled, the temperature rise in the air inlet port 7 by the high- temperature spitted air can be prevented, and the operation of the engine 100 can be properly maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air supply valve pressurized by a supercharger and cooled by a cooler and supplied to a cylinder through an air supply port. Closed behind the bottom dead center, and a part of the supply air in the cylinder is blown back into the supply port to lower the compression ratio than the expansion ratio.

[0002]

2. Description of the Related Art Conventionally, a Miller cycle engine has been known as a means for improving fuel efficiency in an internal combustion engine.
Normally, a four-stroke engine has the same piston stroke in each of the intake, compression, combustion / expansion, and exhaust strokes.
The Miller cycle engine, which is mechanically correct, also limits the amount of intake air to make it seem as if the air supply stroke is shortened, and does not increase the actual compression ratio. The reason for making the compression ratio smaller than the expansion ratio is that by making the expansion ratio larger than the compression ratio, the combustion energy can be more effectively used as torque. As means for making the compression ratio smaller than such an expansion ratio, there are a method of closing the air supply valve in the middle of the air supply stroke and a method of keeping the air supply valve open for a while in the compression stroke. That is, by closing the air supply valve earlier or later than the bottom dead center, the compression ratio can be made smaller than the expansion ratio. However, the latter slow closing method has a larger flow area of the air supply valve than the former early closing method, so that the air supply pressure can be reduced. For this reason, the intake valve late closing method can suppress the rise of the engine back pressure, reduce the pumping loss of the engine, and realize high thermal efficiency.

[0003]

In the Miller cycle engine of the intake valve late closing type, since the intake valve is opened for a while during the compression stroke, the supply air once supplied to the cylinder is supplied to the supply port. It is blown back to. Further, since the inside of the cylinder is high in temperature, the supply air blown back is relatively high, and the temperature of the air supply port rises due to the supply air blown back, and the supply air temperature actually rises. . As a result, there arises a problem that the air supply efficiency is reduced due to the expansion of the air supply and knocking occurs, and it is not possible to realize the high efficiency which is the concept of the Miller cycle engine.

As means for solving such a problem, for example, Japanese Patent Application Laid-Open Nos.
There is a means described in 291715. In these configurations, a water-cooled air supply cooler is added to the air supply port side to cool the air supply blown back from the cylinder separately from the conventional air supply cooler. Since the vessel uses cooling water, it is necessary to add a flow path for the cooling water and the like, which results in a considerably complicated structure. Accordingly, it is an object of the present invention to provide a Miller cycle engine that has a simple structure and can suppress a rise in supply air temperature due to blowback supply in view of such circumstances.

[0005]

Such a Miller cycle engine is preferably constructed as follows, as described in claim 1. That is, the supply air after the supply air pressurized by the supercharger is cooled by the cooler is supplied into the cylinder through the supply port and the supply air provided on the supply port side of the cylinder. To configure a Miller cycle engine in which the valve is closed later than the bottom dead center and a part of the air supply in the cylinder is blown back into the air supply port to lower the compression ratio than the expansion ratio, the air supply port And a diffuser portion of the supercharger, which is provided with a bypass flow path that can bypass the cooler, and a valve that prevents flow of air from the diffuser portion side to the air supply port side is provided with the bypass passage. Prepare for the channel. Since the temperature inside the cylinder is high during operation, the supply air supplied to the cylinder becomes high temperature, and in the Miller cycle engine, the high temperature supply air is blown back from the inside of the cylinder to the supply port during the compression stroke. It is important to cool the blowback supply air in the high temperature state. The Miller cycle engine includes a bypass passage that allows the air supply port and the diffuser of the supercharger to flow around the cooler. In the diffuser part of the turbocharger, the air supply is flowing at high speed inside, and by connecting a bypass flow passage to this diffuser part, the diffuser part serves as a venturi tube,
As a result, the supply air in the bypass passage can be sucked and sent to the cooler side. Further, a valve is provided in the bypass flow passage for preventing the supply of air from the diffuser portion side to the air supply port side, thereby preventing the air supply from bypassing the cooler in the air supply stroke. Can be. With these configurations,
The high-temperature supply air blown back to the supply port in the compression stroke is sucked into the diffuser portion of the supercharger through the bypass passage, cooled again by the cooler, and sent to the supply port. It is possible to suppress a rise in the temperature of the supply air in the inside. In such a Miller cycle engine, as described in claim 2, the flow path between the branch of the bypass flow path in the air supply port and the cooler is provided from the side of the branch of the air supply. It is preferable to provide a valve that blocks flow to the cooler side. The high-temperature supply air blown back to the supply port in the compression stroke can be reliably sent to the bypass flow path side at the branch point, and the temperature increase of the supply port can be further suppressed. As for the valve for preventing the supply of air in a predetermined direction described above, it is possible to use a check valve, but the on-off valve is opened and closed based on the operation cycle of the engine, and the predetermined direction is controlled. When the supply air flows, it can be closed. Furthermore, in order to make the temperature of the air supply port suitable while suppressing the temperature rise of the air supply port, the following configuration can be adopted. That is, as set forth in claim 3, a flow rate setting means for setting a flow rate of the supply air flowing through the bypass flow path or the cooler downstream flow path is provided. This Miller cycle engine is provided with a flow control valve or the like as flow setting means for setting the flow rate of the supply air flowing through the bypass flow path or the cooler downstream flow path. It is possible to set a ratio of the supply air that is blown back and to be sent to the bypass flow path side in the branch portion, and thereby it is possible to set an amount of the supply air that is sent to the upstream side of the cooler. Therefore, it is possible to change the temperature of the air supply port by adjusting the flow rate setting means, which is preferable. Also,
The flow rate setting means can be also adjusted by adjusting the opening degree of the valve in the open state by using the above-described valve for blocking the flow.

[0006] In these Miller cycle engines, it is desired to suppress knocking that causes enormous damage to the engine and maintain a good operating state of the engine. Knocking occurs when the supply air temperature rises and the supply air preignites. Therefore, in order to suppress knocking, it is necessary to cool the supply air temperature to bring it into a normal ignition state, and it is preferable to configure as described in claim 4. That is, a knocking sensor for detecting knocking of the engine is provided, and a control means for adjusting the flow rate of the supply air by operating the flow rate setting means based on the detection result of the knocking sensor is provided. That is, the occurrence of knocking is detected by a knocking sensor, and when knocking occurs, the flow rate setting means is operated, and the high-temperature supply air blown back to the supply port is located upstream of the cooler through the bypass flow path. By increasing the ratio of air supply circulating to the air supply and lowering the air supply temperature in the air supply port, premature firing of the air supply can be suppressed and knocking can be avoided. That is, the control unit controls the temperature of the air supply in the air supply port to the low temperature side by controlling the flow rate of the bypass flow passage to the increasing side when knocking occurs, thereby suppressing the premature ignition of the air supply. And knocking can be avoided.

[0007] The condition of the supply air temperature that suppresses engine knocking varies depending on the engine load. Therefore, as set forth in the present application, if the supply air temperature is appropriately set to maintain the operating state of the engine in a good state, it is necessary to cope with such a change in the engine load. The following is a proposal for appropriately adjusting the flow rate setting means in response to such a change in the engine load to obtain a preferable operation state. That is, as described in claim 5, a load detection means for detecting the load of the engine is provided, and the supply air temperature setting means for setting the supply air temperature in the supply port by operating the flow rate setting means. And control means for operating the supply air temperature setting means based on the engine load detected by the load detection means to control the operating state of the engine. In this configuration, the load detecting means detects an engine load that is considered to affect the operating state of the engine. On the other hand, as in the example described so far, by operating the flow rate setting means, the temperature of the air supply in the air supply port can be arbitrarily changed, and further, the cooler is measured while measuring the air supply temperature. Supply air temperature setting means that can set the temperature in the air supply port by adjusting the flow rate of the air supply circulating upstream of the air supply port. The control means controls the supply air temperature in the supply port to a suitable temperature by operating the supply air temperature setting means based on the engine load detected by the load detection means. As a result, the operating state of the engine can be maintained in a good state. For example, information for setting the supply air temperature in the air supply port or setting the change tendency thereof is stored in advance in accordance with the engine load or in response to such a change tendency of the engine load. The temperature in the air supply port is changed in accordance with such previously obtained reference information. For example, when the engine load increases, the air supply temperature in the air supply port is controlled to a low temperature side, and when the engine load decreases, the air supply temperature in the air supply port is controlled to a high temperature side, The operating state of the engine can be maintained in a good state so that knocking is always avoided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Miller cycle engine 1 of the present application
00 will be described with reference to FIG. Engine 100
Is provided with a cylinder 3 having an air supply valve 1 and an exhaust valve 2 and a piston 4 housed in the cylinder 3. The supercharger 5 includes a blower section 5a and a turbine section 5b which are connected to each other, and is capable of pressurizing supply air, which is a mixture of fuel and air, by exhaust gas discharged from the cylinder 3. . The supply air pressurized by the blower section 5 a passes through the supply passage 11, is cooled by the cooler 6, and is supplied into the cylinder 3 through the supply port 7. The above configuration is the same as that of the conventional Miller cycle engine. The air supply valve 1 is closed later than the bottom dead center and the compression ratio is expanded by blowing back the air once supplied to the air supply port 7. A lower mirror cycle can be realized. Further, the Miller cycle engine according to the present invention is provided with a bypass flow passage 10 connecting the air supply port 7 and the diffuser portion 12 of the blower portion 5a, and a check valve 8 is provided on the air supply port 7 side of the bypass flow passage 10. To the bypass passage 1 of the air supply port 7.
A check valve 9 is provided on the side of the cooler at the branch of the zero. The check valve 8 can prevent the flow of the air supply from the diffuser part side to the air supply port 7 side, and the check valve 9 can prevent the air supply from the air supply port 7 side to the cooler 6 side. It is possible to prevent distribution.

The diffuser section 12 is a section through which supply air accelerated by a turbine (not shown) provided in the blower section 5a flows. By connecting the bypass flow passage 10 to the diffuser portion 12 so that, for example, the opening of the bypass flow passage 10 comes in the flow direction of the air supply, the diffuser portion 12 allows the air supply to flow therein at a high speed. Therefore, it serves as a venturi tube, and the supply air of the bypass passage 10 can be sucked. In addition, an arbitrary structure can be adopted as long as the air supply from the bypass flow passage 10 is sucked into the diffuser unit 12.

The characteristic configuration of the Miller cycle engine 100 according to the present invention has been described above. FIG.
Description will be made based on (b). FIG. 1A shows the state of the engine 100 in the air supply stroke, in which the air supply valve 1 is open,
By closing the exhaust valve 2 and moving the piston 4 from the top dead center to the bottom dead center, the air in the air supply port 7 can be supplied to the cylinder 3. In this case, the check valve 8 is closed from the installation direction, and the check valve 9 is opened. Thereby, the air supplied to the cylinder 3 is sent from the cooler 6 side. Next, FIG. 1 (b) shows a state in which the air supply valve 1 is open during the compression stroke. The air supply valve 1 is open, the exhaust valve 2 is closed, and the piston 4 is dead. By moving to the top dead center side from the point, the air supplied to the cylinder 3 once, which is peculiar to the Miller cycle, is blown back to the air supply port 7. In this case, the check valve 8 is opened from the installation direction, and the check valve 9 is closed.
Thereby, the supply air blown back to the supply port 7 is sent in the direction of the bypass flow path 10. By repeating the states (a) and (b), the air supply blown back to the air supply port 7 in the compression stroke is guided to the bypass flow passage 10 and is passed through the diffuser section 12 of the supercharger 5 to the cooler. 6, the air supply in the air supply port 7 is always cooled, and the temperature rise in the air supply port 7 due to the high-temperature blow-back air supply in the Miller cycle engine is suppressed. Can be made suitable.

Further, as shown in FIG. 2, in the Miller cycle engine 200 according to the present invention, knocking can be suppressed and a good operating state of the engine can be maintained. That is, the Miller cycle engine 200 includes the check valve 8 and the flow control valve 17 that can set the flow rate of the supply air in the bypass flow passage 10. In the Miller cycle engine 200, the air supply in the cylinder is blown back to the air supply port 7 in the compression stroke. As for the supply air, only the flow rate set by the flow control valve 17 flows to the bypass flow passage 10 side, and the other supply air flows to the cooler 6 downstream side. The supply air flowing into the bypass flow path 10 flows upstream of the cooler 6 via the diffuser section 12, is cooled again by the cooler 6, and flows to the air supply port 7. Therefore,
By adjusting the opening degree of the flow control valve 17 by the control device 18, the supply air circulating to the upstream side of the cooler 6 via the bypass passage 10 out of the supply air blown back into the air supply port 7. Can be adjusted, and the temperature can be adjusted by adjusting the cooling amount of the air supply in the air supply port 7. For example, when the amount of air supply circulating upstream of the cooler 6 is increased, the temperature of the air supply in the air supply port 7 is decreased. The temperature of the air supply rises. The means for adjusting the flow control valve 17 based on the output signal of the control device 18 in this manner is referred to as flow setting means A.

The engine 200 has a knocking sensor 15 for detecting knocking of the engine.
Knocking occurs due to premature firing of the air supply, and it is necessary to reduce the ignitability of the air supply in order to avoid knocking. Therefore, when knocking occurs, knocking can be avoided by controlling the air supply to a low temperature side, and the engine 200 according to the present invention activates the flow rate setting means A based on the detection result of the knocking sensor, Knocking can be avoided by adjusting the supply temperature of the supply port 7. That is, when knocking occurs, the flow rate setting means A is controlled to increase, the amount of supply air flowing through the bypass passage 10 is increased, and the supply air temperature in the supply port 7 is controlled to low temperature, Knocking can be avoided by reducing the ignitability of the air supply.

Further, in the engine 200 according to the present invention, the temperature sensor 16 is provided in the air supply port 7, and the control device 18 makes the flow control valve 17
Can be adjusted to set the supply air temperature in the supply port 7 to a predetermined temperature. As described above, the flow control valve 17 is controlled based on the output signal of the control device 18 and the air supply port 7 is controlled.
The setting of the supply air temperature inside is referred to as supply air temperature setting means B.

A system is configured in the control device 18 so that load information relating to the engine is input, and based on the input information, the supply air temperature setting means B
The control of the operating state of the engine can also be performed by controlling the air supply temperature in the air supply port 7 by operating. This configuration will be described below.

As for the engine load, an engine load detecting sensor 19 for monitoring the required number of revolutions of the engine and the like.
(Example of means) is adopted, and the control device 18 activates the supply air temperature setting means B to store the supply air temperature in the supply port 7 in advance in response to a detected change in load. A suitable temperature for the engine load stored in the device 180 can be obtained. For example, when the engine load detected by the engine load detecting means 19 increases, the supply air temperature in the supply port 7 is controlled to a low temperature side, and when the engine load decreases, the supply port 7 is controlled.
By controlling the supply air temperature in the inside to the high temperature side, the operating state of the engine can be maintained in a good state, for example, so as to always avoid knocking. Here, means for detecting the engine load, such as a load sensor, is referred to as load detecting means C.

[Other Embodiments] (A) In the above-described embodiment shown in FIG. 1, the valves for preventing the air supply from flowing in a predetermined direction are configured as check valves. The valve may be configured to be an on-off valve and opened and closed based on the operation cycle of the engine. For example, the on-off valve provided in the bypass passage is opened when the supply air is blown back in the compression stroke, and the other is closed in order to supply the supply air in the bypass passage in the supply stroke. The air supply port can be prevented from flowing to the air port, and the on-off valve provided between the cooler and the branch portion is opened when the air supply is supplied to the cylinder in the air supply stroke, so that the air supply stroke In this case, the air supplied into the cylinder is only air supplied from the cooler side. (B) As a fuel that can be used for the Miller cycle engine of the present application, any fuel such as city gas, gasoline, propane, methanol, and hydrogen can be used. (C) In producing the supply air, the fuel and the gas containing oxygen for combustion of the fuel may be mixed. For example, air is generally used as the oxygen-containing gas for combustion. is there. However, as such a gas, it is possible to use, for example, an oxygen-enriched gas having an oxygen component content higher than that of air. (D) In the above embodiment, knocking was detected by attaching a knocking sensor to the cylinder. However, premature ignition was detected by detecting the cylinder internal pressure and comparing it with the crankshaft angle. Premature firing can also be detected as knocking. Further, the cylinder is provided with a photo sensor, and the pre-ignition of the air supply can be detected by comparing with the crankshaft angle. (E) In the above-described embodiment, the structure in which the supply air, which is a mixture of fuel and air, is sucked into the cylinder is shown. However, the fuel and the air are separately supplied, for example, in the embodiment. The invention of the present application is also applicable to an engine having a fuel injector that injects fuel into a cylinder using only air as air. (F) In the above-described embodiment, the check valve 9 is installed on the downstream side of the cooler in the engine 100 shown in FIG.
Even when the check valve 9 is not installed, the blowback air supply can be guided to the bypass flow path 10 side. That is, since the bypass flow passage 10 is connected to the diffuser portion 12 of the supercharger 5, the supply air in the bypass flow passage 10 is sucked to the diffuser portion 12 side. Therefore, the supply air blown back into the supply port 7 is guided to the bypass passage 10 side. (G) In the Miller cycle engine 200 shown in FIG. 2 according to the above-described embodiment, the flow passage adjusting means A for adjusting the amount of the supply air blown back in the compression stroke flowing to the bypass passage 10 side includes a bypass passage. Although the flow control valve 17 provided in the above was used, it is also possible to use a flow control valve 21 provided on the downstream side of the cooler 6 instead of the flow control valve 17, and in this case, the blow-back is performed. By adjusting the amount of air supply flowing to the cooler 6 side, the bypass flow path 1
The amount flowing to the zero side can be adjusted.

[0017]

As described above, the above-mentioned method can suppress a rise in the temperature of the supply air due to the blow-back air supply with a simple structure and improve the operation state of the engine.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a supply air cooling system of a Miller cycle engine of the present application.

FIG. 2 is a diagram showing a configuration of a supply air cooling system for a Miller cycle engine according to the present application.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 supply valve 2 exhaust valve 3 cylinder 4 piston 5 supercharger 6 cooler 7 supply port 8, 9 check valve 10 bypass flow path 15 knocking sensor 16 temperature sensor 17 flow control valve 18 control device 100 mirror cycle engine A Flow setting means B Supply air temperature setting means C Load detection means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tadashi Katayama 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka Gas Co., Ltd. (reference) 3G084 AA00 BA00 BA23 DA38 FA02 FA18 FA25 FA33 3G092 AA11 AA12 DA12 DB03 DC00 DF01 DF10 FA02 FA16 HA04Z HA11Z HC05Z HE01Z

Claims (5)

[Claims] 1. A supply air pressurized by a supercharger is cooled by a cooler, and then supplied to a cylinder via an air supply port, and an air supply valve provided on the air supply port side of the cylinder. A Miller cycle engine that closes later than BDC to blow a part of the air supply in the cylinder back to the air supply port to lower the compression ratio than the expansion ratio. A diffuser section of the feeder is provided with a bypass flow path that allows the bypass device to flow around the cooler,
A Miller cycle engine including a valve in the bypass passage for preventing a flow of air from flowing from the diffuser section to the air supply port. 2. A valve for preventing a supply air from flowing from the branch portion side to the cooler side in a cooler downstream flow passage between the branch portion of the bypass flow passage and the cooler in the air supply port. The Miller cycle engine according to claim 1, further comprising: 3. The Miller cycle engine according to claim 1, further comprising a flow rate setting means for setting a flow rate of supply air flowing through the bypass flow path or the cooler downstream flow path. 4. The engine according to claim 3, further comprising: a knocking sensor for detecting knocking of the engine; and control means for operating the flow rate setting means based on a detection result of the knocking sensor to adjust a flow rate of the supply air. Miller cycle engine. 5. A load detecting means for detecting a load of an engine, and an air supply temperature setting means for operating the flow rate setting means to set an air supply temperature in an air supply port. 4. The Miller cycle engine according to claim 3, further comprising control means for operating the supply air temperature setting means based on the engine load and controlling an operation state of the engine.