Free piston engine

Abstract

The invention discloses a free piston engine which comprises two oppositely-arranged air cylinders and further comprises two swing gears, one-way clutches and transmission shafts, the one-way clutches and the transmission shafts are matched with the swing gears respectively, pistons of the two air cylinders are connected through a push rod provided with a rack, and the swing gears are meshed with the rack. The swing gear is in transmission connection with the transmission shaft corresponding to the swing gear through one-way clutches to form fixed-axis rotation, one-time linear reciprocating of the piston forms a cycle, and the locking directions of the two one-way clutches are opposite to each other, so that it is guaranteed that the two transmission shafts alternately output torque and idle within two strokes of one reciprocating. The idling direction of the two transmission shafts is the same as the transmission rotation direction, a transmission mechanism composed of a crankshaft and the like is omitted, and linear reciprocating motion of the piston is converted into rotation motion so as to output power in a rotation form.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engine technology, in particular to a free piston engine. BACKGROUND

[0002] Hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and range-extended electric vehicle (REEV) are the main technical routes of energy-saving and new energy vehicles, and the common point of the three is that they all contain a piston engine with a crankshaft, and convert fuel (such as gasoline, diesel, methanol, natural gas, hydrogen, etc.) into mechanical energy, and HEV, PHEV and REEV all need to maximize the energy conversion efficiency of the engine.

[0003] The power generated by the existing piston engine is transmitted to the push rod by the piston, and the push rod is transmitted to the crankshaft by the crank, and then converted into rotary motion and output power. Due to the limitation of the push rod and the crankshaft, the stroke of the piston is fixed, so it is impossible to adjust and optimize the compression ratio according to the power demand, and the system thermal efficiency is limited, and when doing work, the push rod will exert a counterforce, and its transverse component will tightly press the piston against the cylinder wall, greatly increasing the friction and energy loss.

[0004] When the work stroke just starts, the pressure in the cylinder is the largest, but the crank is close to the top dead center at this time, the force arm of the push rod to the crankshaft is small, the torque formed is small, and thus the output power is also small. At the same time, the energy release of high-temperature and high-pressure gas is slow, and the energy loss caused by gas leakage and heat loss also increases.

[0005] When the work stroke is about to end, the crank is close to the bottom dead center at this time, the force arm of the push rod to the crankshaft is small, and the pressure in the cylinder is small at this time, so the output power is also small, that is, the power density of the engine is reduced, and the fluctuation of the output power is also increased.

[0006] In addition, the load between the push rod and the crankshaft, and the crankshaft and the shell is large, the friction loss is large, and high-pressure oil lubrication bearing is needed, and the oil pump consumes energy, thereby reducing the efficiency of the engine. SUMMARY

[0007] Therefore, the present application provides a free piston engine to solve the above problems, which can cancel the complex transmission mechanism composed of the push rod and the crankshaft in the prior art, and convert the linear reciprocating motion of the piston into rotary motion to output power in rotary form, while improving the efficiency of the engine.

[0008] To achieve the above purpose, the technical scheme provided by the present application is as follows:

[0009] The application provides a free piston engine, which comprises two oppositely arranged cylinders and a transmission unit; the transmission unit comprises two rocking gears, a one-way clutch matched with each rocking gear and a transmission shaft; the pistons of the two cylinders are connected through a push rod, the push rod is provided with a rack, the two rocking gears are engaged with the rack, and the rocking gears are connected with the corresponding transmission shafts through the one-way clutches to form fixed-axle rotary arrangement; the piston makes a linear reciprocating motion to form two strokes; one of the cylinders is always in compression and the other cylinder is always in work in each stroke; the linear reciprocating motion of the piston forms a cycle, and the locking directions of the two one-way clutches are opposite to each other to ensure that the two transmission shafts alternately output torque and idle in two strokes of one reciprocation, and the idle directions of the two transmission shafts are the same as the transmission rotary directions.

[0010] Further, the rack is a single-sided rack, and the two rocking gears are arranged on the same side of the corresponding push rod; the rotary directions of the two transmission shafts are opposite to each other.

[0011] Further, the two rocking gears are arranged at intervals.

[0012] Further, the two transmission shafts are respectively provided with output gears for outputting torque to realize alternating torque output.

[0013] Further, the two transmission shafts are respectively provided with meshing coupling gears, and one of the transmission shafts is provided with an output gear for outputting torque to realize continuous torque output.

[0014] Further, the rack is a double-sided rack, and the two rocking gears are arranged on the two sides of the corresponding push rod; the rotary directions of the two transmission shafts are the same.

[0015] Further, the two transmission shafts are respectively provided with output gears for outputting torque to realize alternating torque output.

[0016] Further, the two transmission shafts are respectively provided with first gears and second gears, the first gears and the second gears are engaged with a coupling gear to form a coupling arrangement for alternately transmitting power; the coupling gear is assembled with a connecting shaft, and the connecting shaft is provided with an output gear for outputting torque to realize continuous torque output.

[0017] The technical scheme provided by the application has the following beneficial effects:

[0018] The present application can cancel the complex transmission mechanism constituted by the crankshaft and the like in the prior art, not only can reduce the overall cost, but also through the push rod provided with the rack to push the corresponding swing gear to rotate, and then realize the conversion of the linear reciprocating motion of the piston into the rotary motion, to output the power in the rotary form, to drive the rotary generator with stable power generation efficiency, to improve the conversion efficiency from mechanical energy to electric energy, and at the same time, can improve the engine efficiency, and can also be used as a direct power for driving HEV, PHEV and REEV and the like. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 shows a schematic diagram of a free piston engine in a first state in embodiment one;

[0020] Figure 2 Fig. 2 shows a schematic diagram of a power output connection of the free piston engine in embodiment one;

[0021] Figure 3 Fig. 3 shows another schematic diagram of a power output connection of the free piston engine in embodiment one;

[0022] Figure 4 Fig. 4 shows a schematic diagram of a free piston engine in a second state in embodiment one;

[0023] Figure 5 Fig. 5 shows a schematic diagram of a free piston engine in a third state in embodiment one;

[0024] Figure 6 Fig. 6 shows a schematic diagram of a free piston engine in a fourth state in embodiment one;

[0025] Figure 7 Fig. 7 shows a schematic diagram of a free piston engine in a first state in embodiment two;

[0026] Figure 8 Fig. 8 shows a schematic diagram of a free piston engine in a second state in embodiment two;

[0027] Figure 9 Fig. 9 shows a schematic diagram of a free piston engine in a third state in embodiment two;

[0028] Figure 10 Fig. 10 shows a schematic diagram of a free piston engine in a fourth state in embodiment two;

[0029] Figure 11 Fig. 11 shows a schematic diagram of one kind of power output connection of the free piston engine in embodiment two. DETAILED DESCRIPTION

[0030] For further illustration of the embodiments, the present application provides the accompanying drawings. These drawings are part of the disclosure of the present application, which mainly serve to illustrate the embodiments, and can be used to explain the operating principles of the embodiments in conjunction with the related description. Those of ordinary skill in the art should be able to understand other possible implementations and advantages of the present application in conjunction with these. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0031] The present application is further illustrated in conjunction with the accompanying drawings and specific embodiments.

[0032] Embodiment one

[0033] Referring to Figure 1 The embodiment provides a free piston engine (hereinafter referred to as piston engine), which comprises two oppositely arranged cylinders, and a transmission unit, the transmission unit comprises two swing gears, a one-way clutch matched with each swing gear, and a transmission shaft, the pistons of the two cylinders are connected by a push rod 3, the push rod 3 is provided with a rack 31, and the rack 31 is a single-sided rack, the swing gears are all engaged with the rack 31, and the swing gears are connected with the corresponding transmission shafts through the one-way clutches to form a fixed shaft rotation arrangement, that is, each swing gear, the corresponding one-way clutch, and the transmission shaft are coaxially arranged, and the swing gears rotate in a fixed shaft manner, such as alternating clockwise rotation or counterclockwise rotation, while the transmission shaft rotates in a single direction.

[0034] The piston makes a linear reciprocating motion each time to form two strokes, and in each stroke, one cylinder is always compressing and the other cylinder is always doing work.

[0035] The linear reciprocating motion of the piston forms a cycle, and the locking directions of the two one-way clutches are opposite to each other to ensure that the two transmission shafts alternately output torque and idle in the two strokes of one reciprocation, and the idle directions of the two transmission shafts are the same as the transmission directions, that is, in any one stroke, one one-way clutch is locked to transmit power to the corresponding swing gear and transmission shaft, and the other one-way clutch is separated to idle the corresponding transmission shaft, so that the two transmission shafts alternately output torque and idle in the two strokes of one reciprocation, and the rotation directions of the two transmission shafts remain unchanged whether they transmit power or idle; the one-way clutch characteristic of the one-way clutch allows the transmission shaft to continue to rotate in the transmission direction by inertia when idling.

[0036] In the embodiment, the two swing gears are arranged on the same side of the corresponding push rod 3 and are spaced apart from each other, and the two one-way clutches are arranged in opposite directions, so that the rotation directions of the two transmission shafts are opposite to each other, and the two transmission shafts are respectively provided with output gears for outputting torque to realize alternating output of torque.

[0037] In specific implementation, the two cylinders are a first cylinder 1a and a second cylinder 1b arranged in left and right spaces and symmetrically, the first cylinder 1a and the second cylinder 1b are fixedly assembled on the shell of the engine, the first cylinder 1a is provided with a first combustion chamber and a first piston 2a, the second cylinder 1b is provided with a second combustion chamber and a second piston 2b, and the first piston 2a and the second piston 2b are fixedly connected through the push rod 3 to realize left and right reciprocating linear motion of the first piston 2a, the second piston 2b and the push rod 3.

[0038] The two swing gears are a first swing gear 4a and a second swing gear 4b arranged in left and right directions, the two one-way clutches are a first one-way clutch 5a and a second one-way clutch 5b, and the two transmission shafts are a first transmission shaft 6a and a second transmission shaft 6b, the first transmission shaft 6a is provided with a first output gear 8a for outputting torque, and the second transmission shaft 6b is provided with a second output gear 8b for outputting torque.

[0039] The first one-way clutch 5a and the first transmission shaft 6a are assembled on the first swing gear 4a, and the first swing gear 4a and the first transmission shaft 6a are drivingly connected through the first one-way clutch 5a.

[0040] The second one-way clutch 5b and the second transmission shaft 6b are assembled on the second swing gear 4b, and the second swing gear 4b and the second transmission shaft 6b are drivingly connected through the second one-way clutch 5b.

[0041] The first swing gear 4a and the second swing gear 4b are engaged with the rack 31.

[0042] When the push rod 3 moves in a first direction (e.g., to the right), the rack 31 drives the first swing gear 4a and the second swing gear 4b to rotate in a clockwise direction; conversely, when the push rod 3 moves in a second direction opposite to the first direction (e.g., to the left), the rack 31 drives the first swing gear 4a and the second swing gear 4b to rotate in a counterclockwise direction.

[0043] When the first swing gear 4a rotates clockwise, the first one-way clutch 5a is in a locked state, so that the first swing gear 4a and the first transmission shaft 6a are drivingly connected, i.e., the first swing gear 4a drives the first transmission shaft 6a to rotate in a clockwise direction and transmits power.

[0044] When the first swing gear 4a rotates counterclockwise, the first one-way clutch 5a is in a disengaged state, so that the transmission connection between the first swing gear 4a and the first transmission shaft 6a is disconnected, that is, the first swing gear 4a cannot drive the first transmission shaft 6a to rotate counterclockwise, and power cannot be transmitted to each other. At this time, the first transmission shaft 6a continues to rotate clockwise by inertia.

[0045] When the second swing gear 4b rotates counterclockwise, the second one-way clutch 5b is in a locked state, so that the second swing gear 4b and the second transmission shaft 6b can realize transmission, that is, the second swing gear 4b drives the second transmission shaft 6b to rotate counterclockwise and transmit power.

[0046] When the second swing gear 4b rotates clockwise, the second one-way clutch 5b is in a disengaged state, so that the transmission connection between the second swing gear 4b and the second transmission shaft 6b is disconnected, that is, the second swing gear 4b cannot drive the second transmission shaft 6b to rotate clockwise, and power cannot be transmitted to each other. At this time, the second transmission shaft 6b continues to rotate counterclockwise by inertia.

[0047] In summary, when the push rod 3 moves to the right, the first one-way clutch 5a is locked, and the power output by the push rod 3 is transmitted to the first transmission shaft 6a through the first swing gear 4a and the first one-way clutch 5a, and is output in a clockwise rotation. At the same time, the second transmission shaft 6b rotates counterclockwise without load; when the push rod 3 moves to the left, the second one-way clutch 5b is locked, and the power output by the push rod 3 is transmitted to the second transmission shaft 6b through the second swing gear 4b and the second one-way clutch 5b, and is output in a counterclockwise rotation. At the same time, the first transmission shaft 6a rotates clockwise without load.

[0048] The piston engine of this embodiment is a two-stroke engine. A complete working cycle is formed by the two strokes of the piston engine and the scavenging after the power stroke. Each cylinder completes intake, compression stroke, expansion power stroke and exhaust in one cycle.

[0049] When the push rod 3 moves to the right, the gas in the first cylinder 1a does work, the first piston 2a moves to the right, and the second piston 2b also moves to the right, compressing the oil and gas mixture in the second cylinder 1b; when the push rod 3 moves to the left, the gas in the second cylinder 1b does work, the second piston 2b moves to the left, and the first piston 2a also moves to the left, compressing the oil and gas mixture in the first cylinder 1a; the piston of a piston engine makes one back and forth motion, which is two strokes, that is, one cycle. In each stroke, there is always one cylinder compressing and the other cylinder doing work.

[0050] In each stroke, there is always one transmission shaft being driven and transmitting power, while the other transmission shaft is not subjected to force and idles by inertia, and this process is repeated alternately, so that in each stroke, there is always one transmission shaft outputting power.

[0051] In each stroke, there is always one transmission shaft being driven and transmitting power, while the other transmission shaft is not subjected to force and idles by inertia, and this process is repeated alternately, so that in each stroke, there is always one transmission shaft outputting power.

[0052] The specific working principle of the piston engine of this embodiment is as follows, and one cycle of the piston engine includes a first state, a second state, a third state and a fourth state.

[0053] like Figure 1 The piston engine shown is in a first state, the first piston 2a has just completed a power stroke and reached the bottom dead center, and has completed exhaust and intake through scavenging, while the second piston 2b has completed a compression stroke and reached the top dead center.

[0054] like Figure 4 The piston engine shown is in the second state, with the first cylinder 1a in a compression stroke. The stroke driving force for the first piston 2a comes from the second piston 2b in the second cylinder 1b. That is, the gas in the second combustion chamber of the second cylinder 1b burns and rapidly expands to produce work, pushing the second piston 2b to the left. The second cylinder 1b is in a power stroke. The rapid expansion of the second piston 2b can reduce knock during SI combustion in the second cylinder 1b, reduce nitrogen oxides, and improve unburned hydrocarbon (i.e., UHC) and CO gas emissions. At this time, the second piston 2b drives the push rod 3 to the left, thereby driving the first piston 2a to the left and compressing the gas in the first cylinder 1a. This is the compression stroke. During this process, the rack 31 drives the first and second rocking gears 4a, 4b to rotate counterclockwise. Only the second one-way clutch 5b transmits power to cause the second transmission shaft 6b to rotate counterclockwise and output power. However, the first one-way clutch 5a does not transmit power, and the first transmission shaft 6a can only rely on inertia to maintain clockwise rotation.

[0055] like Figure 5 The piston engine shown is in the third state, the first piston 2a completes the compression stroke and reaches the top dead center, while the second piston 2b completes the power stroke and reaches the bottom dead center, and after scavenging, exhaust and intake are completed.

[0056] like Figure 6The piston engine shown is in the fourth state, when the first cylinder 1a is in the power stroke, i.e. the gas in the first combustion chamber of the first cylinder 1a burns and expands rapidly to do work, pushing the first piston 2a to move to the right, the first cylinder 1a is in the power stroke, the rapid expansion of the first piston 2a can reduce the knock in the SI combustion in the first cylinder 1a, reduce nitrogen oxides, and improve unburned hydrocarbon and CO gas emissions, at this time the first piston 2a drives the push rod 3 to move synchronously to the right, in turn driving the second piston 2b to move to the right and compressing the gas in the second cylinder 1b, which is in the compression stroke, the rack 31 drives the first and second swing gears 4a and 4b to rotate clockwise, only the first one-way clutch 5a transmits power to make the first transmission shaft 6a rotate clockwise and output power, but the second one-way clutch 5b does not transmit power, and the second transmission shaft 6b can only rely on inertia to keep rotating counterclockwise.

[0057] As shown in Figure 2 The first transmission shaft 6a keeps rotating clockwise and alternately transmits power and idles in turn, while the second transmission shaft 6b keeps rotating counterclockwise and alternately idles and transmits power in turn.

[0058] The first transmission shaft 6a and the second transmission shaft 6b alternately transmit power and idle in turn to ensure that one of the transmission shafts is always transmitting power in each stroke, and the torque is output through the first output gear 8a or the second output gear 8b respectively.

[0059] In one cycle of the piston engine, the piston engine has variable stroke and compression ratio, the variable compression ratio allows the use of different fuels to improve the flexibility and adaptability of the piston engine, and also promotes HCCI combustion to ensure higher thermal efficiency (i.e. thermal efficiency not less than 60%), and also improves the potential of SI-HCCI transition through variable compression ratio.

[0060] The embodiment replaces the complex transmission mechanism composed of a crankshaft and the like in the prior art with the push rod 3 provided with the rack 31 and the transmission unit, which not only reduces the number of moving parts, simplifies the transmission structure and reduces the overall cost, but also cancels the high-pressure oil lubricated bearing to cancel the oil pump, thereby reducing energy consumption and improving system energy conversion efficiency, and also effectively reducing the lateral load on the engine piston, thereby reducing the friction loss between the piston and the cylinder wall.

[0061] Moreover, the rack 31 on the push rod 3 pushes the corresponding swing gear to rotate, thereby converting the linear reciprocating motion of the piston of the piston engine into rotary motion to output rotary power, which is used to drive a rotary generator with stable power generation efficiency, thereby improving the conversion efficiency from mechanical energy to electrical energy, and also improving the engine efficiency, and also serving as direct power for driving HEV, PHEV and REEV vehicles.

[0062] In addition, when the piston of the piston engine is around the top dead center, the acceleration is obviously higher, thereby reducing the residence time at high temperature and reducing the heat loss in the combustion process, when the piston of the piston engine is around the bottom dead center, the force arm of the push rod 3 does not decrease, the output power attenuation is smaller, so as to realize small output power fluctuation.

[0063] Compared with the prior art piston engine, the piston engine has strong vibration in three-axis directions of x-axis, y-axis and z-axis, but the piston engine of the embodiment has strong vibration in only one direction (i.e. the movement direction of the piston along left and right), and the NVH (NVH includes noise, vibration and sound roughness) characteristic is significantly improved.

[0064] Of course, in other embodiments, the number of the cylinders is not limited to this, and can be more than two, which will not be described in detail here.

[0065] In addition, as shown in Figure 3 Two coupling gears 7 are arranged on the two transmission shafts respectively, and the first transmission shaft 6a is provided with an output gear 8 for outputting torque, so as to realize continuous output of torque.

[0066] When the first transmission shaft 6a is driven, the power is directly output through the output gear 8 assembled on the first transmission shaft 6a, at this time, the first transmission shaft 6a rotates clockwise, and the second transmission shaft 6b rotates counterclockwise.

[0067] When the first transmission shaft 6a is idle, the first transmission shaft 6a rotates clockwise, and the second transmission shaft 6b transmits power, and the second transmission shaft 6b rotates counterclockwise, driving the coupling gear on the second transmission shaft 6b to rotate counterclockwise, thereby driving the coupling gear on the first transmission shaft 6a to rotate clockwise and transmit power, so as to drive the output gear 8 assembled on the first transmission shaft 6a to rotate clockwise and output power.

[0068] In this way, in each stroke as shown in Figure 3 The output gear 8 always outputs power and rotates clockwise.

[0069] Embodiment Two

[0070] Referring to Figure 7 The embodiment two provides a free piston engine, and the structure of the embodiment two is basically the same as that of the embodiment one, and the difference lies in that the push rod 3' is provided with a double-sided rack, two swing gears are arranged on the upper side and the lower side of the push rod 3' respectively, and the rotation directions of the two transmission shafts are the same.

[0071] The first swing gear 4a is engaged with the lower side rack of the push rod 3', and the second swing gear 4b is engaged with the upper side rack of the push rod 3', so as to realize that the rotation directions of the two swing gears are always opposite.

[0072] When the push rod 3' moves to the right, the rack on the lower side of the push rod 3' pushes the first rocking gear 4a to rotate clockwise, the first one-way clutch 5a is locked, and the first transmission shaft 6a rotates clockwise and transmits power; at the same time, the rack on the upper side of the push rod 3' pushes the second rocking gear 4b to rotate counterclockwise, the second one-way clutch 5b is disengaged, and the second transmission shaft 6b is not subjected to force and idles clockwise by inertia.

[0073] When the push rod 3' moves to the left, the upper rack of the push rod 3' pushes the second rocking gear 4b to rotate clockwise, the second one-way clutch 5b is locked, and the second transmission shaft 6b rotates clockwise and transmits power; at the same time, the lower rack of the push rod 3' pushes the first rocking gear 4a to rotate counterclockwise, the first one-way clutch 5a is disengaged, and the first transmission shaft 6a is not subjected to force and idles clockwise by inertia.

[0074] The specific working principle of this embodiment is as follows:

[0075] like Figure 7 The piston engine shown is in a first state, the first piston 2a has just completed a power stroke and reached the bottom dead center, and has completed exhaust and intake through scavenging, while the second piston 2b has completed a compression stroke and reached the top dead center.

[0076] like Figure 8 The piston engine shown is in the second state. When the first piston 2a is in the compression stroke, the stroke driving force of the first piston 2a comes from the second piston 2b of the second cylinder 1b, that is, the gas in the second combustion chamber of the second cylinder 1b burns and expands rapidly to do work, pushing the second piston 2b to move to the left. The second cylinder 1b is in the power stroke. At this time, the second piston 2b drives the push rod 3' to move to the left, thereby driving the first piston 2a to move to the left and compressing the gas in the first cylinder 1a. This is the compression stroke. During this process, the lower rack of the push rod 3' drives the first rocking gear 4a to rotate counterclockwise, and the upper rack of the synchronous push rod 3' drives the second rocking gear 4b to rotate clockwise. Only the second one-way clutch 5b transmits power to make the second transmission shaft 6b rotate clockwise, but the first one-way clutch 5a does not transmit power. The first transmission shaft 6a can only rely on inertia to keep rotating clockwise.

[0077] like Figure 9 The piston engine shown is in the third state, the first piston 2a completes the compression stroke and reaches the top dead center, while the second piston 2b completes the power stroke and reaches the bottom dead center, and after scavenging, exhaust and intake are completed.

[0078] like Figure 10The piston engine shown is in the fourth state. When the first piston 2a is in the power stroke, the gas in the first combustion chamber of the first cylinder 1a burns and expands rapidly to do work, pushing the first piston 2a to move to the right. The first cylinder 1a is in the power stroke. At this time, the first piston 2a drives the push rod 3' to move to the right, and then drives the second piston 2b to move to the right and compresses the gas in the second cylinder 1b, which is a compression stroke; the lower side rack of the push rod 3' drives the first rocking gear 4a to rotate clockwise, and at the same time, the upper side rack of the push rod 3' drives the second rocking gear 4b to rotate counterclockwise. Only the first one-way clutch 5a transmits power to make the first transmission shaft 6a rotate clockwise, but the second one-way clutch 5b does not transmit power. The second transmission shaft 6b can only rely on inertia to keep rotating clockwise.

[0079] This embodiment provides a push rod 3' with a double-sided rack and the transmission unit to replace the complex transmission mechanism composed of the crankshaft and the like in the prior art. This not only reduces the number of moving parts, simplifies the transmission structure, and reduces the overall cost, but also eliminates the high-pressure oil-lubricated bearings and the oil pump, thereby reducing energy consumption and improving the energy conversion efficiency of the system. It also effectively reduces the lateral load on the engine piston, thereby reducing the friction loss between the piston and the cylinder wall.

[0080] Moreover, by pushing the corresponding rocking gear to rotate through the push rod 3', the linear reciprocating motion of the piston of the piston engine is converted into rotational motion to output power in the form of rotation, which is used to drive a rotating generator with stable power generation efficiency, thereby improving the conversion efficiency of mechanical energy into electrical energy, and at the same time improving the engine efficiency. It can also be used as a direct power for driving vehicles such as HEVs, PHEVs and REEVs.

[0081] In another preferred embodiment, Figure 11 As shown, a first gear 10a and a second gear 10b are respectively provided on the two transmission shafts. The first gear 10a and the second gear 10b are both engaged with a coupling gear 7 to form a coupling setting for alternately transmitting power. The coupling gear 7 is equipped with a connecting shaft 9, and the connecting shaft 9 is provided with an output gear 8 for outputting torque to achieve continuous output torque.

[0082] In the embodiment, the first gear 10a, the second gear 10b and the coupling gear 7 engaged with the first gear 10a and the second gear 10b constitute an output torque coupling mechanism, the first gear 10a and the first transmission shaft 6a are fixedly connected and rotate clockwise, the second gear 10b and the second transmission shaft 6b are fixedly connected and rotate clockwise, the first gear 10a and the second gear 10b are engaged with the coupling gear 7 respectively to realize power coupling of the first gear 10a and the second gear 10b alternately transmitted, thereby forming power continuously output, and then the power is transmitted through the connecting shaft 9 assembled on the coupling gear 7 to drive the output gear 8 fixed on the connecting shaft 9 to rotate and continuously output torque.

[0083] Of course, in other embodiments, the two transmission shafts shown in FIG. 1 can also be provided with output gears 8 for outputting torque, and the first transmission shaft 6a and the second transmission shaft 6b output power alternately to realize alternating output torque, which will not be described in detail here. Figure 2

[0084] Although the present application is specifically shown and described in connection with the preferred embodiments, it should be understood that various changes in form and details can be made therein without departing from the spirit and scope of the application as defined in the appended claims.​

Claims

1. A free piston engine comprising two oppositely disposed cylinders characterised in that: The transmission unit is further provided; The transmission unit comprises two swing gears, a one-way clutch matched with each swing gear and a transmission shaft; The pistons of the two cylinders are connected by a push rod, the push rod is provided with a rack, the swing gears are engaged with the rack, and the swing gears are connected with the corresponding transmission shafts through the one-way clutches to form a fixed shaft rotation. Each linear reciprocating motion of the piston corresponds to two strokes, one cylinder is always in compression and the other cylinder is always in work in each stroke, one cycle of linear reciprocating motion of the piston is formed, and the locking directions of the two one-way clutches are opposite to each other to ensure that the two transmission shafts alternately output torque and idle in two strokes of one reciprocation, and the idle directions of the two transmission shafts are the same as the transmission rotation directions.

2. The free piston engine of claim 1, wherein: The rack is a single-sided rack, and the two swing gears are arranged on the same side of the corresponding push rod.

3. The free piston engine of claim 1, wherein: The two swing gears are arranged at intervals.

4. The free piston engine according to claim 2 or 3, characterized in that: The two transmission shafts are respectively provided with output gears for outputting torque to realize alternating output of torque.

5. The free piston engine according to claim 2 or 3, characterized in that: The two transmission shafts are respectively provided with meshing coupling gears, and one of the transmission shafts is provided with an output gear for outputting torque to realize continuous output of torque.

6. The free piston engine of claim 1, wherein: The rack is a double-sided rack, and the two swing gears are arranged on the two sides of the corresponding push rod.

7. The free piston engine of claim 5, wherein: The two transmission shafts are respectively provided with output gears for outputting torque to realize alternating output of torque.

8. The free piston engine of claim 5, wherein: The two transmission shafts are respectively provided with first gears and second gears, the first gears and the second gears are engaged with a coupling gear to form a coupling arrangement for alternating transmission of power, the coupling gear is assembled with a connecting shaft, and the connecting shaft is provided with an output gear for outputting torque to realize continuous output of torque.

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