JPH04314927A - Operation method for two/four-cycle engine - Google Patents

Abstract

PURPOSE:To suppress the shock in selection and improve engine efficiency by starting an engine in four-cycle and selecting the operation into two cycle by an acceleration signal, accelerating the engine in two-cycle, and then selecting the operation into four-cycle through the transition in the torque zone of two-cycle when high speed operation is realized. CONSTITUTION:In the high speed operation of an engine, the ordinary four-cycle operations is carried out by an intake valve driving device 51 and an exhaust valve driving device 61. When the high engine output is demanded in the sharp acceleration or the like, an electric rotary machine 73 operates as an electric motor, and energizes the supercharging operation. Further, in the high speed operation, the engine operates as power generator, and the thermal energy of the exhaust gas is converted to the electric energy and recovered. When a clutch is in OFF state in acceleration on the engine stare, switching to two-cycle operation is performed, while in the selection to two-cycle from four-cycle during traveling, operation is performed through the transition in the torque zone two-cycle operation.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies to a 2-4 cycle engine that sequentially selects and switches 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 a method of operating a 2-4 cycle engine that improves engine efficiency by preventing shock from occurring due to torque difference when switching from 4 cycle to 2 cycle.

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 placed below the cylinder sleeve, and air is pumped in near the bottom dead center of the piston to simultaneously perform intake and exhaust in parallel. Since the explosion occurs each time the output shaft rotates, there is little rotational variation and high torque can be generated. On the other hand, 2
A cycle engine performs intake and exhaust simultaneously, so when the engine load is low and the engine speed is low, such as when idling, the intake pressure is low and sufficient scavenging cannot be performed. When the pressure is increased by a supercharger or the like, intake air blow-by occurs, and at such a stage, engine efficiency is low and unburned HC remains in the exhaust gas. In addition, since a two-stroke engine performs intake and exhaust at the same time,
During high-speed operation, air and gas are not replaced sufficiently, making it impossible to produce high output, and the combustion load in the combustion chamber increases, causing problems in terms of durability.

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 scavenging efficiency when operating at low load and low speed than a two-cycle engine, but has a characteristic that high torque cannot be obtained when the engine rotates at low speeds. However, a four-stroke engine has the characteristic that the exhaust gas is clean when the engine is running at low speed and under low load, and the fuel consumption rate is low when the engine rotation speed is high.

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, current turbochargers are equipped with a power generator coaxially with the turbine, which increases the boost pressure at low speeds and high loads, and when the engine load is high, the exhaust gas has sufficient energy. The electric power obtained by rotating the turbine and operating the motor-generator as a generator using the rotational force is stored in the power storage means. A proposed system uses the electric power stored in the power storage means to operate the motor generator to drive the compressor when the engine load is low, making it possible to supercharge the intake air even when the engine load is low. has been done.

[0006]

[Problem 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 light or heavy load, and the above-mentioned 4-stroke engine can also be operated only in a 4-cycle operation mode. . In view of this situation, the applicant proposed a 2-cycle engine that can be operated by switching between 2-cycle and 4-cycle operations with one engine.
For example, a four-cycle engine has already been filed as Japanese Patent Application No. 1-112507. Although these series of 2-4 cycle engines can perform switching operations that take advantage of the advantages of 2-stroke and 4-cycle operating systems, the reality is that the advantages of these operating systems cannot be fully utilized yet, and furthermore, the engine speed is low. It is not possible to dramatically improve operating efficiency under high loads.

The present invention eliminates the shock caused by the torque difference when switching from 4-cycle to 2-cycle in a 2-4 cycle engine, and adjusts the characteristics of the 2-stroke engine and 4-stroke engine as well as the characteristics of the turbocharger to the engine operation. The present invention provides a method for operating a 2-4 cycle engine that can be selected depending on the situation and has good acceleration and durability.

[0008]

[Means for Solving the Problems] The means according to the present invention for solving the above problems is based on a motor whose rotation is energized by an electric motor.
In an engine equipped with a bot charger that can switch between 2 and 4 cycles, the engine is started in the 4th cycle and switched to the 2nd cycle by an acceleration signal, and when the engine is accelerated in the 2nd cycle and becomes high-speed operation, the 2nd cycle torque zone is activated.
This is characterized by switching the cycle to 4 cycles.

[0009]

[Operation] Since the present invention is constructed as described above, the engine is started in four cycles. This makes it possible to create a low pollution exhaust engine. Next, when the engine is started and the switching to 2-cycle mode is to be performed, confirmation is made using the acceleration signal and the clutch is in the OFF state. When accelerating, the turbocharger is driven to supercharge the 2-stroke engine, efficiently replacing air and exhaust gas, and taking advantage of the 2-stroke engine's characteristics at low speeds to output high torque. Smooth start of
Go to Su. 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 operates with good acceleration by taking advantage of the characteristics of a 2-stroke engine. Next, when the engine rotational speed exceeds a certain rotational speed and the engine is operated at high speed, the amount of fuel in the two-stroke engine is throttled and its output is made close to that of a four-stroke engine, thereby shifting the torque zone of the two-stroke engine and switching to the four-stroke engine. As a result, the difference in torque between the 2nd cycle and the 4th cycle is reduced, so there is no shock when switching between them, and high-speed operation is performed in the 4th cycle, making it possible to drive 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 represents 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 by 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. In FIG. 4, the engine is started in four cycles. This allows it to operate as a low pollution engine. Next, in step S1, it is determined whether the engine is accelerating. That is, during acceleration, the transmission is shifted from first gear to second gear, so the clutch is turned off during this time (step S2). With the clutch OFF, the camshaft and injection pump are set to two cycles, the fuel valve is operated, the turbocharger is operated by the generator motor, and the clutch is turned ON (Step S).
3). In this way, the engine is accelerated from first gear to second gear,
Moreover, by switching from 4-cycle to 2-cycle with the clutch in the OFF state, no shock occurs due to the torque difference. Then, in step S3, the clutch is turned on, and the engine is accelerated by supercharging with the turbocharger and performing two-cycle operation while performing two-cycle scavenging. Then, the engine speed, engine load, and accelerator opening are detected, and in step S4, it is determined whether or not the engine will operate with exhaust gas, and the turbochart will be activated.
Operate the jar at full load and perform two-cycle operation.

In this manner, the turbocharger is operated at full load and is operated in two cycles to accelerate the engine and shift the engine to high speed operation. However, since the TCG (turbo motor) only operates at low speeds and high loads and during acceleration, it is necessary to judge the conditions and operate in 4 cycles at high speeds and high loads where the turbocharger does not need to be accelerated by the electric motor in the 4 cycle zone. 4). In step S5, the conditions for 4 cycles are determined in the acceleration state of the engine,
It is determined whether the engine rotational speed and torque are suitable for switching to 4-cycle mode, and if they are suitable, the turbocharger is operated at full load and high-speed operation is performed using 4-cycle mode. When the engine shifts from high-speed running to low-speed operation and the engine torque becomes unsuitable for 4-cycle operation, the engine is switched to 2-cycle operation. This switching involves cutting the fuel, setting the camshaft and fuel pump to 2-cycle mode, moving through the 2-cycle torque zone, and returning to step S1 to perform 2-cycle operation. By moving the torque zone in the two cycles in this manner, no shock occurs due to the torque difference.

Next, in step S1, when starting on a slope, the vehicle may climb the slope without changing the gears and maintaining the 4-cycle cycle. In such a case, step S6
, the engine speed becomes high in S7, and
Engine load increases. Therefore, it is necessary to switch to two cycles and output a large torque. In this switching to 2-cycle mode, fuel injection is stopped, the camshaft and injection pump are set to 2-cycle mode, the fuel valve is opened, and the transition is made to the 2-cycle torque zone, where step S
Return to 1 and run 2 cycles. By shifting the 2-cycle torque zone and switching from 4-cycle to 2-cycle in this way, shocks due to torque differences do not occur.

Furthermore, when the engine is idling with the clutch turned off in step S3, and when the engine speed is low and the engine load is small and the engine is not accelerated in steps S6 and S7, four-cycle operation is performed.

[0027] As described above, during acceleration when starting the engine, the clutch is OFF and the vehicle is switched to 2-cycle mode, and when the vehicle is switched from 4-cycle mode to 2-cycle mode while the vehicle is running, the 2-cycle torque zone is shifted.

[0028]

As described in detail above, according to the present invention, when accelerating at the time of starting the engine, the clutch is OFF, the mode is switched to 2-cycle, and when switching from 4-cycle to 2-cycle while driving, the 2-cycle mode is switched to 2-cycle. Since the torque zone of the cycle is shifted, there is no torque difference and no shock occurs due to switching. As a result, the driver does not feel any discomfort and can enjoy comfortable driving. In addition, the turbocharger efficiently scavenges air in the 2-stroke engine while outputting high torque with the 2-stroke engine, and 4-cycle operation is performed when driving at high speeds, resulting in excellent acceleration and fuel efficiency. You can get a cycle engine.

[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 block diagram illustrating a method of operating a 2-4 cycle engine according to an embodiment of the present invention.

[Explanation of sign]

1 Engine body 2 Piston 3 Slide valve 5 Intake valve 6 Exhaust valve 7 Turbocharger 8 Controller 12 Inlet 31 Window section 34 Spring

Claims (1)

[Claims] In an engine that can switch from 2 to 4 cycles and is equipped with a turbocharger that has an electric motor on the same axis, the engine is started in 4 cycles and switched to 2 cycles by an acceleration signal, and when the engine is accelerated in 2 cycles and becomes high-speed operation, 2 to 4 cycles are switched. A method of operating a 2-4 cycle engine, characterized by shifting the cycle torque zone and switching to 4 cycle.