JPH04314925A - Operation method for two/four-cycle engine - Google Patents

Abstract

PURPOSE:To drastically improve the efficiency of an engine by generating a high torque in the low speed operation and carrying out the operation with high fuel consumption in the high speed operation by selectively switching three operation conditions of turbocharger operation, two and four cycle operations according to the operation state of the engine. CONSTITUTION:In the low speed high load state, a controller 8 operates an engine in two-cycle operation, and suspends the operation of an intake valve driving device 51 and holds an intake valve 5 in closed state. further, the controller 8 controls a exhaust valve driving device 61 and opens an exhaust valve 6 in each revolution. When a slide valve 3 stops, an intake port 12 and a window part 31 coincide, and the intake air compressed by a turbocharger 7 is supplied into a combustion chamber from the intake port 12. Accordingly, this engine operates as uniflow type two-cycle engine. Then, in the high speed operation, the ordinary four-cycle operation is performed by the intake valve driving device 51 and the exhaust valve driving device 61.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention improves engine efficiency by sequentially selecting and switching between turbocharger, 2-cycle operation, and 4-cycle operation according to engine operating conditions such as changes in engine speed and load. The present invention relates to an improved method of operating a 2-4 cycle engine.

0002

[Prior Art] Conventional piston reciprocating engines include two-cycle engines, which perform the suction, compression, explosion, and exhaust processes with one reciprocation of the piston, or one rotation of the crankshaft, and two-stroke engines, in which the piston reciprocates twice, or two rotations of the crankshaft. It is roughly divided into 4-cycle engines, which perform the above four steps during the engine.

In a two-stroke engine, the intake port is located below the cylinder sleeve, and air is pumped in when the piston descends to simultaneously perform intake and exhaust in parallel. Because the explosion occurs, there is little rotational fluctuation of the output shaft, and it has the characteristics of being able to generate high torque. On the other hand, a two-stroke engine performs intake and exhaust simultaneously, so when the engine load is low and the engine speed is low, such as when idling, the exhaust gas pressure is low and sufficient scavenging cannot be performed. At this stage, 2
It has the characteristic that it is difficult to operate as a cycle engine.

On the other hand, in a four-stroke engine, intake and exhaust are performed in independent steps, so that the air and gas in the cylinder are sufficiently replaced. For that reason 4
A cycle engine has better suction efficiency than a two-stroke engine during low-load, low-speed operation, but has the characteristic of not being able to obtain high torque during engine operation. However, a 4-stroke engine can ensure a sufficient amount of intake air, especially when the engine speed is high.
It has the characteristic of low fuel consumption.

Next, the turbocharger uses the exhaust gas from the engine to rotate a turbine, which rotates a compressor installed coaxially with the turbine to supercharge the air, thereby increasing the efficiency of the engine. I'm trying to improve. Therefore, in order to drive this turbocharger, the exhaust gas pressure and temperature of the engine need to be high, so when the exhaust gas pressure is low, that is, the engine load is low, the turbocharger The reality is that supercharging is not possible. In order to avoid this situation, the turbocharger is equipped with a rotating machine that can generate electric power coaxially with the turbine, and when the engine load is high, the exhaust gas with sufficient energy is used to rotate the turbine. The electric power obtained by operating the motor-generator as a generator using the rotational force is stored in the power storage means. When the engine load is low, the electric power stored in the storage means is used to operate the motor-generator to drive the compressor, making it possible to supercharge the intake air even when the engine load is low. .

[0006]

[Problems to be Solved by the Invention] By the way, the above-mentioned 2-cycle engine can only be operated in a 2-cycle operation mode regardless of the load, and the 4-cycle engine can also be operated only in a 4-cycle operation mode. Can not. In view of this situation, the applicant has developed a 2-4 cycle engine that can be operated by switching between 2-stroke and 4-cycle operations with one engine, for example, as disclosed in Japanese Patent Application No. 1-11250.
It has already been filed as No. 7. Although these series of 2-4 cycle engines can achieve switching operation that takes advantage of the advantages of 2-stroke and 4-cycle operating systems, the reality is that the advantages of these operating systems have not yet been fully utilized. The operating efficiency at low speed and high load cannot be dramatically improved.

[0007] In a 2-4 cycle engine, the present invention selects the characteristics of the 2-stroke engine and 4-stroke engine and the characteristics of the turbocharger according to the operating conditions of the engine, and operates by switching these three elements. The present invention provides a method of operating a 2-4 cycle engine.

[0008]

[Means for Solving the Problems] Means according to the present invention for solving the above-mentioned problems is a turbocharger that energizes an electric motor.
In a 2-4 cycle engine equipped with a turbocharger, the turbocharger or
It is characterized by successively selecting and switching three operating elements of 2-cycle and 4-cycle for operation.

[0009]

[Operation] Since the present invention is constructed as described above, when the engine is started, the turbocharger is driven by the electric motor-generator rotated using the electric power stored in the electric storage means to supercharge the engine. While efficiently replacing air and exhaust gas in a cycle engine, the characteristics of a two-stroke engine at low rotational speeds are utilized to output high torque, allowing the vehicle to start smoothly. After the vehicle starts, this operating state is maintained until the engine reaches a certain rotational speed, thereby outputting high torque while avoiding the scavenging problem of 2-cycle engines at low speeds using a turbocharger. It takes advantage of the characteristics of a 2-stroke engine to operate at low speeds. Next, when the engine speed reaches a certain speed or higher, the turbocharger is stopped and the two-stroke engine continues to operate. Furthermore, when the load is light and the engine rotates at high speed, the engine is switched to the 4-cycle engine, and the characteristics of the 4-cycle engine are utilized for high-speed operation to achieve high-speed operation with good fuel efficiency.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. First, a device for carrying out the method of operating a 2-4 cycle engine according to the present invention will be described. FIG. 1 is a sectional view showing an example of an engine for carrying out the method of the present invention. Also, Figure 2 shows 2-2 in Figure 1.
FIG. Note that FIG. 1 corresponds to the 1-1 sectional view in FIG.

Reference numeral 1 denotes an engine body, and a cylinder sleeve 11 is fitted inside the engine body 1. At the bottom of the cylinder sleeve 11 is an intake port 1 that introduces intake air into the combustion chamber when the engine operates for two cycles.
2 is installed through it. An intake pipe 13 is provided at a position corresponding to the intake port 12 of the engine body 1 to guide intake air to the intake port 12. The engine body 1 further includes an intake pipe 14 in the cylinder head that guides intake air to the combustion chamber, and an exhaust pipe 1 that guides exhaust gas from the combustion chamber to the outside.
5 is provided.

Reference numeral 2 denotes a piston that reciprocates inside the cylinder sleeve 11. FIG. 1 shows a state in which the piston 2 is near the top dead center, and the suction port 12 is closed by the side surface of the piston 2. However, when the piston 2 moves to the bottom dead center, the suction port 12 is closed. 12 is exposed and opened on the combustion chamber side.

Reference numeral 3 denotes a band-shaped slide valve curved along the outer circumferential surface of the cylinder sleeve 11, and two slide valves are disposed on the outer circumference of the cylinder sleeve 11 so as to be freely slidable. The slide valve 3 is made of a material that has excellent heat resistance, does not deform, and is lightweight, such as a ceramic sintered body such as silicon nitride, and has window portions 31 extending through it at the same pitch as the suction port 12. has been done. The two slide valves 3 form an air chamber 32 and an air chamber 33 between them, and the air chamber 33
A spring 34 is disposed in the spring 34 for biasing the slide valve 3 in the direction of expanding the air chamber 33, that is, in the direction of contracting the air chamber 32. Then, the engine body 1
An air pipe 35 communicating with the air chamber 32 and an air pipe 36 communicating with the air chamber 33 are provided.

A pressure tank 41 is connected to the air supply pipe 35 for supplying compressed air to the air chamber 32 in response to a signal from the outside, and for opening the air chamber 32 to the outside. Further, the air supply pipe 36 is provided with a solenoid valve 4 that opens the air chamber 33 to the outside in response to an external signal.
2 are connected.

Reference numeral 5 denotes an intake valve disposed between the intake pipe line 14 and the combustion chamber, and the intake valve 5 is driven by an intake valve drive mechanism that freely opens and closes the intake valve 5 in response to an external signal. The device 51 is connected to the device 51 .

Reference numeral 6 denotes an exhaust valve disposed between the exhaust pipe line 15 and the combustion chamber, and the exhaust valve 6 is driven by an exhaust valve drive system that freely opens and closes the exhaust valve 6 in response to an external signal. It is connected to device 61.

Both the intake valve driving device 51 and the exhaust valve driving device 61 drive the respective valves by attracting or repelling magnetic bodies connected to the intake valves 5 and exhaust valves 6 using fixed electromagnets. It has a structure similar to that described in, for example, Japanese Patent Application No. 63-334960.

Reference numeral 7 denotes a turbocharger, which includes a turbine 72 driven by exhaust gas from the exhaust pipe 15.
and a compressor 71 which compresses intake air using the rotational force of the turbine 72 and supplies it to the intake pipe 13 and intake pipe line 14.
and a rotating electrical machine 73 disposed on a rotating shaft that connects the compressor 71 and the turbine 72. Further, the rotating electrical machine 73 is connected to an inverter/converter 74, and operates as a motor or a generator depending on an external signal.

A controller 8 is connected to the pressure tank 41, electromagnetic valve 42, intake valve drive device 51, exhaust valve drive device 61, and inverter/converter 74, and outputs control signals to these. The controller 8 is composed of a microcomputer, and includes a central control unit for performing arithmetic processing, various memories for storing arithmetic processing procedures, control procedures, etc., input/output ports, and the like.

Next, the operation of the engine with the above configuration will be explained. FIG. 3 is a perspective view showing the operation of the slide valve. When the rotational speed of the engine is below a predetermined speed and the load on the engine is above a predetermined value, that is, when the engine is in a low speed and high load state, the controller 8 operates the engine for two cycles, so the intake valve drive device 51
The operation of the exhaust valve 5 is stopped to hold the intake valve 5 in a closed state, and the exhaust valve driving device 61 is controlled to open the exhaust valve every rotation.

Furthermore, the controller 8 supplies compressed air from the pressure tank 41 shown at A in FIG. 3 to the air chamber 32. Further, the electromagnetic valve 42 is opened to open the air chamber 33 to the outside. Then, due to the pressure inside the air chamber 32, the two slide valves 3 move in a direction to contract the air chamber 33 against the expansion force of the spring 34. At this time, the air inside the air chamber 33 is exhausted as shown in FIG. 3B. Then, when the slide valve 3 stops, the intake port 12 and the window 31 coincide with each other, so that the intake air compressed by the turbocharger 7 is supplied from the intake port 12 to the combustion chamber. Therefore, this engine operates as a uniflow two-stroke engine.

Next, when the engine is operating at low speed and low load or at high speed, the supply of compressed air from the pressure tank 41 to the air chamber 32 is stopped and the air chamber 32 is opened to the outside. Then, the expansion force of the spring 34 causes the slide valve 3 to slide so that the suction port 12 and the window portion 31 do not coincide with each other, thereby closing the suction port 12. Then, the intake valve drive device 51 and the exhaust valve drive device 61 perform a normal four-cycle operation. The rotating electrical machine 73 operates as an electric motor to energize supercharging operation when high output is required from the engine, such as during sudden acceleration, and operates as a generator during high-speed operation. , converts and recovers the thermal energy of exhaust gas into electrical energy.

An embodiment of the present invention will be described below. FIG. 4 shows a performance curve of a 2-4 cycle engine which is an embodiment of the present invention. This performance curve shows the relationship between torque and engine speed, with engine speed on the horizontal axis and engine torque on the vertical axis. In other words, when the engine starts, it operates in two cycles (performance curve B).
, and the turbocharger is driven (performance curve A). In other words, by supercharging the engine with a turbocharger when the engine is running at low speeds, it takes advantage of the characteristics of a 2-stroke engine, which outputs high torque at low speeds while efficiently scavenging air, which is the drawback of 2-stroke engines. It is something to do. Next, at the intersection of performance curve A and performance curve B, that is, when the engine speed reaches NA, the turbocharger is stopped and the engine is operated as a two-stroke engine. Next, when the performance curve B of the 2-stroke engine and the performance curve C of the 4-stroke engine intersect, that is, when the engine speed reaches NB, the engine is switched to the 4-stroke engine and high-speed operation is performed. In this way, by switching the three elements of turbocharger, 2-cycle mode, and 4-cycle mode operation according to the engine operating status, the performance curve of a 2-4 cycle engine as shown in Figure 4 can be created. obtain.

Next, a method of operating the 2-4 cycle engine of this embodiment will be explained using FIG. First, the engine is started, the turbocharger is energized by the electric motor to increase the intake pressure and start is made easier (step S1), and the fuel pump and intake/exhaust valves are turned on. 2 cycles, and after completing the start, a sensor detects the engine load, rotation speed, and accelerator conditions to determine whether the engine is in acceleration mode (step S
2). When the engine is still in acceleration mode, the electric mode of the turbo charger is calculated, the turbo charger is activated, and the engine speed N at that time is the set engine speed NA (Figure 4 ) is compared with (step S3
). When the condition N<NA, the current state is maintained and the turbocharger continues to operate. As the engine continues to operate under these conditions, the engine speed increases, and N>N
When condition A is satisfied, the turbocharger is stopped and two-cycle operation is performed. When the engine speed increases due to this 2-cycle operation and the condition of N>NA is satisfied (step S4), the fuel pump and cam are set to 4-cycle, and 2-
A four-stroke engine operates on four cycles. In this way, the vehicle uses the turbocharger to scavenge air at the start, avoiding the disadvantages of the 2-stroke engine, and making use of the characteristics of the 2-stroke engine, which outputs high torque at low speeds, to achieve smooth operation. - The vehicle will be launched immediately.

After the vehicle has been started in this manner, it is operated in the normal running state as follows. In step S5, when the engine is operating in the 2-cycle mode, the engine load and engine rotation speed are detected by the sensor, and when the engine rotation speed is increasing due to engine acceleration, the engine rotation speed is changed to the 2-cycle mode. - It is determined whether or not it is on (step S6). And that Zo-
When the engine is still in the 2-cycle zone, the fuel pump
The cam is left as is, and in step S7, the engine rotation speed N at that time is compared with the set rotation speed NB (FIG. 4). As a result of this comparison, when N<NB, 2-cycle operation is continued to output high torque at low speeds, and when N>NB, the fuel pump and intake/exhaust valves are
Switch to 4-cycle mode to achieve better fuel efficiency when driving at high speeds. Also, in step S5, 2
When not in the cycle mode, the fuel pump and cam are switched to the 4-cycle mode, and the 2-cycle mode is switched to the 2-cycle mode in step S6.
When it is not on, it is also switched to 4 cycles.

Next, during driving, if the acceleration mode is not for climbing a hill, for example, the acceleration state is checked in step S2, the boost level is calculated according to the engine load, the turbocharger drive conditions are calculated, and the operation is performed in step S2. S3
The condition of N<NA is determined, and if this condition is still met, the turbocharger is operated. This allows it to operate in two cycles at low speeds, and
The engine operates and outputs a large torque.

In this way, by switching between the three conditions of turbocharger, 2-cycle and 4-cycle operation depending on the engine operating conditions, 2-cycle operation at low speeds is possible.
2 while avoiding the drawbacks to cycle engine scavenging.
This makes it possible to operate with high torque by taking advantage of the characteristics of a cycle engine, and to switch to 4-cycle mode at high speeds, realizing fuel-efficient operation.

[0028]

Effects of the Invention As detailed above, according to the present invention, the three operating requirements of the turbocharger, 2-cycle, and 4-cycle are selectively switched according to the operating conditions of the engine. Utilizes the characteristic of a 2-stroke engine that generates high torque at low speeds while avoiding the problem of scavenging at low engine speeds,
At high speeds, the engine can be set to 4 cycles for more fuel-efficient driving. This greatly improves the efficiency of the engine, and also allows a large amount of torque to be obtained at the start, making it possible to change the conventional four-speed transmission to a transmission with one reverse speed and two forward speeds. , its structure can be simplified.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of an engine for implementing the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is a perspective view of the slide valve in FIG. 1;

FIG. 4 is a diagram showing a performance curve of the 2-4 cycle engine of the present invention.

FIG. 5 is a block diagram showing a method of operating a 2-4 cycle engine having the performance of FIG. 4;

[Explanation of sign]

1...Engine body 2...Piston 3...Slide valve 5...Intake valve 6...Exhaust valve 7...Turbo charger 8...Controller 12...Inlet 31...Window part 34...Spring

Claims (1)

[Claims] In a 2-4 cycle switching engine equipped with a turbocharger attached to an electric motor, the three operating elements of the turbocharger, 2-cycle, and 4-cycle are sequentially selected and switched according to the engine operating conditions. 1. A method of operating a 2-4 cycle engine, characterized in that the engine is operated with a 2-4 cycle engine.