JPH0533623A - Two-cycle heat insulated engine - Google Patents

Abstract

PURPOSE:To increase braking force at the time of engine brake in a two-cycle engine. CONSTITUTION:The second exhaust valve 22 which is driven by a motor-driven valve system mechanism 24 is installed at a cylinder head 11 to be opened at the top dead center of a piston at the time of engine brake. The air compressed by a rising piston 3 is press-fed to a turbo charger 4 to operate a revolving electric machine 41 by power generation. It is thus possible to increase engine braking force by means of compression and power generation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle adiabatic engine having a heat insulating structure in a portion related to a combustion chamber of the engine, and more particularly to a two-cycle adiabatic engine having a good engine brake function.

[0002]

2. Description of the Related Art In recent years, in order to improve the thermal efficiency of an engine, heat-resistant ceramics are used for the combustion chamber, for example, a cylinder head, a piston head, an intake / exhaust valve, etc., so that cooling of the engine is unnecessary. The engine is being tried.

On the other hand, in a uniflow two-cycle engine, an exhaust valve is arranged at the head of the cylinder, and an intake port is provided in the lower portion of the cylinder corresponding to the piston bottom dead center. Since the compressed air due to the above is pumped from the intake port, intake and exhaust are performed simultaneously, and the fuel explodes every rotation of the crankshaft, the rotation fluctuation of the output shaft is small and high torque can be generated.

[0004]

In the above-described two-cycle engine, when the engine is operated as a brake, the intake and exhaust openings are close to each other, unlike four cycles in which the intake and exhaust strokes are independent. In addition, the effect of engine braking is poor, and the pressure balance between intake air and scavenging air is not well balanced, which makes gas exchange in the cylinder difficult. That is, if the scavenging air pressure is high, the exhaust gas in the cylinder can be pushed out to perform intake / exhaust, but in order to raise the scavenging air pressure, supercharging pressure of the turbocharger due to exhaust energy is not sufficient, and supercharging by electric drive of the turbocharger There is a problem in that means for increasing the boost pressure and driving power are required.

The present invention has been made in view of the above problems, and an object thereof is to provide a two-cycle adiabatic engine which is intended to eliminate the inconvenience during engine braking.

[0006]

In order to achieve the above-mentioned object, according to the present invention, a relevant portion of the combustion chamber of the engine has a heat insulating structure, an exhaust valve is provided on the top of the cylinder, and an intake port is provided below the cylinder. In a two-stroke adiabatic engine of the type, after determining the necessity of engine braking from the exhaust valve provided at the top of the cylinder and the operating state of the engine, and during engine braking, the exhaust valve is opened at the piston top dead center position. Provided is a two-cycle adiabatic engine including a valve opening / closing control means for performing a valve closing operation.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a structural block diagram showing an embodiment of a two-cycle adiabatic engine according to the present invention.

In FIG. 1, reference numeral 1 denotes a cylinder of the engine 10, which has a cylinder head 11 and a cylinder liner 12. The lower surface of the cylinder head 11 and the cylinder liner 12 are made of a heat-resistant ceramic material and formed into a heat insulating structure. ing. The cylinder head 11 has a first exhaust valve 21 made of high-strength and heat-resistant ceramics.
And a second exhaust valve 22 are provided, and the first exhaust valve 21
Is driven by a valve operating mechanism 23 having a normal timing of opening / closing in response to the vertical movement of the piston 3, while the second exhaust valve 22 is an electrically operated valve operating mechanism 24 controlled by a controller described later. The valve is opened / closed by.

Reference numeral 13 denotes an intake port penetrating below the cylinder liner 12, and when the intake port is open, the exhaust gas is scavenged by fresh air pressure-fed from the turbocharger 4 driven by the exhaust energy, and at the time of the next combustion. It inhales the necessary air.

A rotary electric machine 41 is attached to the turbine shaft of the turbocharger 4, and is configured to be electrically operated or generate electricity depending on the operating state of the engine 10.

Reference numeral 51 is a rotation sensor for detecting the number of revolutions of the engine 10, 52 is a crank position sensor for detecting the crank position, and 53 is a load sensor for the engine 10.
For detecting the load state of the vehicle, 54 is an accelerator pedal 55
Is an accelerator sensor for detecting the stepping state of the sensor, and detection signals from these sensors are connected to the input circuit of the controller 5, respectively.

The controller 5 is composed of a microcomputer, and is provided with a central control unit for performing arithmetic processing, various memories for storing arithmetic processing procedures and control procedures, an input / output circuit, and the like. When it is determined that the engine brake needs to be operated, a command is issued to the valve operating mechanism 24 for operating the second exhaust valve 22, and, for example, in FIG. As shown in (A) and (B), the second exhaust valve 22 is opened at the top dead center position of the piston 3 to discharge the compressed air due to the rise of the piston 3, and the valve is immediately closed after the discharge. Then, as shown in (C) and (D) of FIG. 2, the internal pressure of the cylinder is lowered by lowering the piston, and the reduced negative pressure facilitates introduction of fresh air from the intake port 13 during scavenging. To It has been made.

Next, the operation of this embodiment thus constructed will be described.

During normal operation of the engine 10, the first exhaust valve 21 is opened and closed by the valve operating mechanism 23 at the valve timing in the two-cycle operation, and the second exhaust valve 22 remains closed. The engine 10 is operated.

On the other hand, when the accelerator pedal 55 is not depressed and the engine brake is judged to be necessary by the signals from the rotation sensor 51, the load sensor 53, etc., the controller 5 instructs the valve operating mechanism 24. The second exhaust valve 22 is opened near the top dead center of the piston.

Therefore, as shown in FIGS. 2A and 2B, the air in the cylinder compressed by the rise of the piston 3 is released at the top dead center position, but the work of this compression is performed by the brake. The energy of the air that becomes the braking force of the vehicle and is blown into the turbocharger 4 when it is further released is converted into electric power by the rotating electric machine 41 that operates to generate electricity.

Then, when the piston 3 descends from the top dead center, the second exhaust valve 22 is immediately closed by the valve operating mechanism 24, and thus is closed as shown in FIGS. 2 (C) and (D). The air in the cylinder has a negative pressure, and fresh air can be efficiently introduced through the intake port 13 even if the scavenging air pressure has not risen.

The present invention has been described above with reference to the above-described embodiments, but within the scope of the present invention, for example, the valve mechanism 23 of the first exhaust valve 21 also employs a valve mechanism using electromagnetic force. During engine braking, the opening and closing of the second exhaust valve 22 is controlled at the top dead center position of the piston.
Further, when the piston descends, various modifications and applications are possible in which the negative pressure is promoted without opening the valve until the intake port 13 opens, and these modifications and applications are not excluded from the scope of the present invention. Absent.

[0020]

According to the present invention as in the above embodiments,
A second exhaust valve, which is electrically driven to open and close, is attached to the top of the cylinder of a uniflow type two-cycle adiabatic engine.
When the engine is braked, the second piston is at the top dead center position.
The exhaust valve is opened, and the air compressed by the piston rise is discharged to the turbocharger, so that the compression work and the power generation of the rotating electric machine by the rise of the turbine inlet pressure are simultaneously performed, and the engine braking force is increased. In addition, since the negative pressure is generated by closing the second exhaust valve when the piston descends from the top dead center, there is an advantage that fresh air is introduced into the cylinder even if the scavenging pressure is low. Be done.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a two-cycle adiabatic engine according to the present invention.

FIG. 2 is an explanatory diagram showing an example of the operation of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... Piston 4 ... Turbocharger 5 ... Controller 10 ... Engine 13 ... Intake port 21 ... First exhaust valve 22 ... Second exhaust valve 41 ... Rotating electric machine

Claims (1)

Claim: What is claimed is: 1. A uniflow type two-cycle adiabatic engine in which a relevant portion of a combustion chamber of an engine has a heat insulating structure, an exhaust valve is provided at the top of the cylinder, and an intake port is provided below the cylinder. An exhaust valve provided in the engine, and a valve opening / closing control means for determining the necessity of engine braking from the operating state of the engine and for operating the engine braking to open the exhaust valve at the piston top dead center position and then close the valve. A two-cycle adiabatic engine characterized by