CN107701305B - Free piston engine with variable stroke - Google Patents

Abstract

The invention discloses a free piston engine with variable stroke. The engine comprises a combustion chamber part, a spring chamber part, a permanent magnet linear motor part and an electronic control unit part, and realizes full flexible control of an intake valve and an exhaust valve by adopting a cam-free variable gas distribution mode and electromagnetically driving a gas distribution mechanism; the electronic control unit controls the displacement of the piston by adjusting the size and the direction of the electrified current of the permanent magnet linear motor coil, realizes the variable upper and lower dead points and the variable compression ratio of the piston, and realizes the real-time control of the valve opening time, the valve lift curve and the valve distribution duration by changing the control signal of the cam-free variable valve distribution mechanism. The invention has simple structure and high efficiency, realizes the full flexible control of each actuating mechanism of the engine and improves the energy-saving and environment-friendly performance of the engine.

Description

A variable stroke free piston engine

technical field

The invention relates to the technical field of vehicle engines, in particular to a variable stroke free piston engine.

Background technique

Reciprocating cycle engines are divided into two-stroke engines and four-stroke engines according to the number of strokes in one working cycle. A working cycle of a two-stroke internal combustion engine is divided into two strokes, the first stroke piston moves from bottom dead center to top dead center to complete intake and compression, and the second stroke piston moves from top dead center to bottom dead center to complete work and discharge Gas, a working cycle is completed. A working cycle of a four-stroke internal combustion engine is divided into four strokes. The first stroke piston moves from top dead center to bottom dead center to complete intake air, the second stroke piston moves from bottom dead center to top dead center to complete compression, and the third stroke The piston moves from the top dead center to the bottom dead center to complete the work, and the fourth stroke piston moves from the bottom dead center to the top dead center to complete the exhaust.

Compared with the two engines, the reciprocating motion of the piston of the two-stroke engine does one work at a time, and the power density is larger. The number of times of work per unit time is twice that of the four-stroke engine. The structure of the engine is compact, but although the number of work per unit time of the two-stroke engine is twice that of the four-stroke engine, due to the large volume loss and poor ventilation effect, the residual exhaust gas in the cylinder is relatively high, and the fuel utilization rate is low. Its power performance is only increased by 50%-70%; the four strokes of the four-stroke engine are completely separated, the ventilation effect is better, the fuel utilization rate is high, and the emission is low, but because the piston reciprocates twice to complete one work, the power is lower for two-stroke engines.

The free-piston engine has no crank-and-rod mechanism, which is simpler than the traditional engine, with fewer parts and smaller volume, and the engine piston has no lateral force during motion, and the friction resistance of the piston is small and has a long service life. Since there is no constraint of the crank-and-rod mechanism, the position of the upper and lower dead centers of the piston is variable, and the engine has a variable compression ratio, which can optimize the fuel economy and reduce emissions of the engine in combination with different engine operating conditions, and also realize the engine adaptability to multiple fuel capacity.

At present, there are three main schemes for realizing variable stroke technology: the first one is to configure two-stroke cylinders on the engine, and use two-stroke cylinders and four-stroke cylinders to work separately according to actual needs, that is, multi-cylinder cooperation mode, the engine The utilization rate is low, which increases the weight and cost of the engine; the second is to use a set of gas distribution system to meet the gas distribution of two-stroke and four-stroke at the same time, and the camshaft is provided with two-stroke gas distribution lines and four-stroke gas distribution lines. The profile line and the transition profile line for switching use hydraulic or mechanical drive to change the position of the variable cam to complete the switching of the gas distribution. The design and production are difficult, the controllability is low, and good fuel economy cannot be obtained; The third is to change the structure of the engine block, combine the intake and exhaust valve distribution of the four-stroke engine with the scavenging and ventilation of the two-stroke engine, and use the combination of different air passage closures to complete the work of each stroke , the engine utilization rate of this scheme is high, but the variable compression ratio cannot be realized, and the utilization of different fuels cannot be realized, which has limitations in fuel adaptability and fuel economy.

Contents of the invention

The purpose of the present invention is to provide a variable-stroke free-piston engine that can be freely switched between two-stroke and four-stroke and has a variable compression ratio, which can meet the needs of different working conditions and has better fuel economy and Power, and can meet the work of different fuels.

The technical solution that realizes the object of the present invention is: a kind of variable-stroke free-piston engine, comprises four parts of combustion chamber, spring chamber, permanent magnet linear motor and electronic control unit, wherein:

The combustion chamber part includes variable valve train, engine cylinder head, engine block, piston and spark plug, wherein the variable valve train changes the valve lift, valve opening time and valve opening duration under the control of the electronic control unit to realize Fully flexible control of engine gas distribution;

The spring chamber part includes a spring and a bracket. The spring is fixed between the engine piston and the linear motor. When the piston goes down, the spring is compressed to limit the displacement of the piston and store energy. When the piston goes up, the spring provides recovery energy;

The permanent magnet linear motor part includes a linear motor shell and a coil mover, wherein the inner coils of the coil mover are arranged as concentric solenoids, and the coil mover of the linear motor is fixedly connected with the engine piston. The electronic control unit adjusts the current of the linear motor coil and direction to control the displacement of the engine piston;

When the engine is working, the electronic control unit makes real-time control of the gas distribution, fuel injection, ignition and piston displacement of the engine according to different requirements, so that the engine can work under different strokes and different loads.

Further, the upper and lower dead centers of the piston are variable, and the compression ratio is variable.

Further, the material of the housing of the linear motor is a permanent magnet.

Further, there is a working gap between the inner side of the linear motor shell and the coil mover of the linear motor, so that the coil mover can move up and down.

Compared with the prior art, the present invention has the remarkable advantages as follows: (1) the camshaft air distribution mechanism and the crank connecting rod mechanism are eliminated, the structure is simple and the utilization rate is high; (2) the camshaft variable air distribution mechanism replaces the The camshaft gas distribution mechanism and the linear motor drive replace the crank connecting rod mechanism, which realizes the fully flexible control of each actuator of the engine, and enables the engine to realize variable stroke and variable compression ratio under the control of the electronic control unit (ECU). , can freely switch between two-stroke and four-stroke; (3) It can meet the needs of different working conditions, has better fuel economy and power, and can meet the work of different fuels.

Description of drawings

Fig. 1 is a structural schematic diagram of a variable-stroke free-piston engine of the present invention.

Figure 2 is a schematic diagram of the working conditions of a four-stroke engine.

Figure 3 is a schematic diagram of the working conditions of the two-stroke engine.

Detailed ways

The variable-stroke free-piston engine of the present invention comprises combustion chamber, spring chamber, permanent magnet linear motor and electronic control unit four parts, wherein:

The combustion chamber part includes a variable valve mechanism 1, an engine cylinder head 2, an engine block 5, a piston 4 and a spark plug 3, wherein the variable valve mechanism 1 changes the valve lift, valve opening time, The valve opening duration realizes the fully flexible control of engine gas distribution;

The spring chamber part includes a spring 7 and a bracket 8, wherein the spring 7 is fixed between the engine piston 4 and the linear motor. When the piston 4 goes down, the spring 7 is compressed to limit the displacement of the piston 4 and store energy. When the piston 4 goes up, the spring 7 provides restore energy;

The permanent magnet linear motor part includes a linear motor housing 9 and a coil mover 10, wherein the inner coils of the coil mover 10 are arranged as concentric solenoids, the coil mover 10 of the linear motor is fixedly connected with the engine piston 4, and the electronic control unit adjusts the linear The magnitude and direction of the electric current of the motor coil realizes the control of the displacement of the engine piston 4;

When the engine is working, the electronic control unit makes real-time control of the gas distribution, fuel injection, ignition and piston 4 displacement of the engine according to different requirements, so that the engine can work under different strokes and different loads.

Further, the upper and lower dead centers of the piston 4 are variable, and the compression ratio is variable.

Further, the material of the linear motor housing 9 is permanent magnet.

Further, there is a working gap between the inner side of the linear motor casing 9 and the coil mover 10 of the linear motor, so that the coil mover 10 can move up and down.

The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments.

Example 1

Referring to Fig. 1, a variable-stroke free-piston engine of the present invention includes four parts: a combustion chamber part, a spring chamber part, a permanent magnet linear motor part and an electronic control unit part.

in:

The combustion chamber part includes a variable valve mechanism 1, an engine cylinder head 2, an engine block 5, a piston 4 and a spark plug 3, wherein the variable valve mechanism 1 changes the valve lift, valve opening time, The valve opening duration realizes the fully flexible control of engine air distribution; the upper and lower dead centers of the piston 4 are variable, and the compression ratio is variable;

The spring chamber part includes a spring 7 and a bracket 8, wherein the spring 7 is fixed between the engine piston 4 and the linear motor. When the piston 4 goes down, the spring 7 is compressed to limit the displacement of the piston 4 and store energy. When the piston 4 goes up, the spring 7 provides restore energy;

The permanent magnet linear motor part includes a linear motor housing 9 and a coil mover 10, wherein the inner coils of the coil mover 10 are arranged as concentric solenoids, the coil mover 10 of the linear motor is fixedly connected with the engine piston 4, and the electronic control unit adjusts the linear The size and direction of the energized current of the motor coil realize the control of the displacement of the engine piston 4; the material of the linear motor housing 9 is a permanent magnet; there is a working gap between the inner side of the linear motor housing 9 and the coil mover 10 of the linear motor, Make the coil mover 10 move up and down;

When the engine is working, the electronic control unit makes real-time control of the gas distribution, fuel injection, ignition and piston 4 displacement of the engine according to different requirements, so that the engine can work under different strokes and different loads.

The working conditions of the four-stroke engine are shown in Figure 2:

Power stroke: the electronic control unit (ECU) controls the spark plug 3 to ignite, the mixed working fluid in the cylinder starts to burn, and the pressure in the cylinder rises to push the piston 4 to move from the top dead center to the bottom dead center to complete the power stroke;

Exhaust stroke: the piston 4 moves from the bottom dead center to the top dead center under the joint action of the spring 7 and the linear motor mover 10, and at the same time, the electronic control unit (ECU) sends an exhaust valve opening signal to the variable valve train 1 , the variable valve mechanism 1 opens the exhaust valve and keeps it open. At the end of the exhaust stroke, the electronic control unit (ECU) sends an exhaust valve closing signal to the variable valve mechanism 1, and the variable valve mechanism 1 closes. The exhaust valve remains closed to complete the exhaust stroke;

Intake stroke: the piston 4 moves from the top dead center to the bottom dead center under the action of the linear motor mover 10, and at the same time, the electronic control unit (ECU) sends the intake valve opening signal to the variable valve train 1, and the variable distribution Air mechanism 1 opens the intake valve and keeps it open. At the end of the intake stroke, the electronic control unit (ECU) sends an intake valve closing signal to the variable valve mechanism 1, and the variable valve mechanism closes the intake valve and keeps it open. In the closed state, the intake stroke is completed;

Compression stroke: the piston 4 moves from the bottom dead center to the top dead center under the joint action of the spring 7 and the linear motor mover 10, the intake valve and the exhaust valve remain closed, and the fuel injector receives the fuel injection signal from the controller to start The fuel injection mixes with fresh air to complete the compression stroke and the cycle ends.

The working conditions of the two-stroke engine are shown in Figure 3:

The first stage: the electronic control unit (ECU) controls the spark plug 3 to ignite, the mixed working fluid in the cylinder starts to burn, and the pressure in the cylinder rises rapidly to push the piston 4 to move from the top dead center to the bottom dead center to perform work. During the movement of the piston, The variable valve mechanism 1 opens the exhaust valve and the intake valve successively to start exhaust and intake, and the first stage ends when the piston 4 moves to the bottom dead center;

The second stage: the piston 4 moves from the bottom dead center to the top dead center under the joint action of the spring 7 and the linear motor mover 10, and the variable valve mechanism 1 closes the exhaust valve and the intake valve successively to complete the exhaust and intake valves. The fuel injector receives the fuel injection signal from the controller to mix the fuel injection with fresh air, and the piston 4 moves to the top dead center to compress the mixed gas in the cylinder to complete the second stage, and a cycle ends.

The switching process of the engine from the four-stroke working condition to the two-stroke working condition: After the electronic control unit (ECU) receives the stroke switching signal, it controls the engine to continue to work in the four-stroke working condition until the end of the compression stroke (the end of this cycle), and then switches into two-stroke control mode.

The switching process of the engine from the two-stroke working condition to the four-stroke working condition: After receiving the stroke switching signal, the electronic control unit (ECU) controls the engine to continue to work in the two-stroke working condition until the end of the second stage (the end of this cycle), Switch to four-stroke control mode.

In summary, the variable-stroke free-piston engine of the present invention can be freely switched between two-stroke and four-stroke, and has a variable compression ratio to meet the needs of different working conditions, and has better fuel economy and power. And can meet the work of different fuels.

Claims (4)

1. A free piston engine with variable stroke is characterized by comprising four parts, namely a combustion chamber, a spring chamber, a permanent magnet linear motor and an electronic control unit, wherein:

the combustion chamber part comprises a variable valve mechanism (1), an engine cylinder cover (2), an engine cylinder body (5), a piston (4) and a spark plug (3), wherein the variable valve mechanism (1) changes a valve lift, a valve opening time and a valve opening duration under the control of an electronic control unit, so that the full-flexible control of engine valve distribution is realized;

the spring chamber part comprises a spring (7) and a bracket (8), wherein the spring (7) is fixed between the piston (4) of the engine and the linear motor, the spring (7) is compressed when the piston (4) descends, the displacement of the piston (4) is limited and energy is stored, and the spring (7) provides return energy when the piston (4) ascends;

the permanent magnet linear motor part comprises a linear motor shell (9) and a coil rotor (10), wherein coils in the coil rotor (10) are arranged in a concentric solenoid way, the coil rotor (10) of the linear motor is fixedly connected with an engine piston (4), and an electronic control unit realizes the control of the displacement of the engine piston (4) by adjusting the size and the direction of the electrifying current of the coil of the linear motor;

when the engine works, the electronic control unit controls the gas distribution, oil injection, ignition and piston (4) displacement of the engine in real time according to different requirements, so that the engine can work under different strokes and different loads.

2. The variable stroke free piston engine as claimed in claim 1 wherein top dead center and bottom dead center of the piston (4) is variable and the compression ratio is variable.

3. The variable stroke free piston engine according to claim 1 wherein the material of the linear motor housing (9) is a permanent magnet.

4. The variable stroke free piston engine according to claim 1, wherein a working gap is left between the inside of the linear motor housing (9) and the coil mover (10) of the linear motor, so that the coil mover (10) can move up and down.