Four-stroke free piston engine

Abstract

The utility model discloses a four-stroke free piston engine, which comprises two groups of cylinders, two rocking gears, a one-way clutch and a transmission shaft, pistons of the two air cylinders in the same group are connected through push rods, racks are arranged on the two push rods respectively, one swing gear is meshed with the racks of the two push rods respectively, the other swing gear is meshed with the rack of at least one push rod, and the swing gears are in transmission connection with the corresponding transmission shafts through one-way clutches. Each air cylinder sequentially completes an air inlet stroke, a compression stroke, a power stroke and an exhaust stroke to form a cycle, a piston of one air cylinder always works and synchronously drives the other three air cylinders to complete the air inlet stroke, the compression stroke and the exhaust stroke respectively, and the locking directions of the two one-way clutches are opposite. Therefore, it is guaranteed that one of the two transmission shafts outputs torque, the other transmission shaft idles, and the idling direction of the transmission shafts is the same as the transmission rotation direction.

Description

Technical Field

[0001] The utility model relates to the technical field of engines, and particularly relates to a four-stroke free piston engine. Background Art

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

[0003] The power generated by the existing piston engine with a crankshaft is transmitted from the piston to the push rod, and then from the push rod to the crankshaft through the crank, and then converted into rotational motion and output power. Due to the limitations of the push rod and the crankshaft, the stroke of the piston is fixed. Therefore, the compression ratio cannot be adjusted and optimized according to the power demand, and the system thermal efficiency is limited. Moreover, when doing work, the push rod will apply a reaction force, and its lateral component will tightly press the piston against the cylinder wall, greatly increasing the friction and energy loss. And restricted by the working mode, most piston engines are two-stroke engines, including a compression stroke and a power stroke, and the compressed mixed gas in the cylinder is ignited at the end of the compression stroke (top dead center), and scavenging and ventilation are carried out at the end of the power stroke (bottom dead center) to discharge exhaust gas, charge air and gas. However, the scavenging time is very short, and it is necessary to pressurize the air to forcibly discharge the exhaust gas in the cylinder; or during the gas exchange process, part of the exhaust gas will remain in the cylinder, and at the same time, part of the fresh air is easily entrained in the exhaust stream. This situation is called short-circuit loss, which will also affect the efficiency of the entire power system.

[0004] When the power stroke just starts, the pressure in the cylinder is the largest, but at this time the crank is close to the top dead center, the force arm of the push rod on the crankshaft is very small, the formed torque is small, and thus the output power is also small. At the same time, the energy contained in the high-temperature and high-pressure gas is released slowly, and the energy loss caused by gas leakage and heat loss also increases accordingly. When the power stroke is about to end, the crank is close to the bottom dead center at this time, the force arm of the push rod on the crankshaft is small, and the pressure in the cylinder is small at this time, so the output power is also small, that is, it reduces the power density of the engine and also increases the fluctuation of the output power.

[0005] In addition, the load between the push rod and the crankshaft, and between the crankshaft and the housing is very large, the friction loss is large, and a high-pressure oil bearing is required. The high-pressure oil bearing requires a high-pressure oil source and is equipped with a high-pressure oil pump. Therefore, additional energy is consumed to drive the high-pressure oil pump to work, resulting in reduced engine output power and efficiency. The high-pressure oil bearings of the push rod and crank are both moving, requiring a complex high-pressure oil circuit to deliver high-pressure lubricating oil to the high-pressure oil bearing. The oil circuit needs to pass through moving parts such as the crankshaft, crank and push rod, which increases the difficulty of manufacturing the above parts and increases the cost accordingly. Summary of the invention

[0006] To this end, in order to solve the above-mentioned problems, the utility model provides a four-stroke free piston engine, which can eliminate the complex components such as the push rod, crankshaft, high-pressure oil bearing and high-pressure oil pump in the prior art, and convert the linear reciprocating motion of the piston into rotational motion to output power in a rotational form, while improving the engine efficiency, and is suitable as an engine for vehicles such as HEV, PHEV and REEV.

[0007] To achieve the above purpose, the technical solution provided by the utility model is as follows:

[0008] The utility model provides a four-stroke free piston engine, comprising two groups of cylinders, each group of cylinders comprising two cylinders arranged oppositely, and also comprising a transmission assembly; the transmission assembly comprises two swing gears and a one-way clutch and a transmission shaft matched with each swing gear, the swing gear being arranged for fixed axis rotation; the pistons of the two cylinders of each group are connected through a push rod, the two push rods are respectively provided with racks, one swing gear is respectively meshed with the racks of the two push rods, the other swing gear is meshed with the rack of at least one push rod, and the swing gear is transmission-connected with the corresponding transmission shaft through the one-way clutch; each cylinder completes intake stroke, compression stroke, power stroke and exhaust stroke in sequence, and forms a cycle, and there is always a piston of a cylinder doing work, and synchronously drives the other three cylinders to respectively complete intake stroke, compression stroke and exhaust stroke, and the locking directions of the two one-way clutches are arranged to be opposite to each other, so as to ensure that one of the two transmission shafts is outputting torque and the other is idling, and the idling direction of the transmission shaft is the same as the transmission rotation direction.

[0009] Further, a cylinder in one group forms a driving force during the power stroke to push its piston to move in the first direction; and through the transmission assembly, the piston of another cylinder in the same group is driven to move in the first direction to achieve the compression stroke, and the pistons of the third and fourth cylinders in the other group are synchronously driven to move in the second direction opposite to the first direction, so that the third and fourth cylinders in the other group respectively complete the intake stroke and the exhaust stroke; or the piston of another cylinder in the same group is driven to move in the first direction to achieve the exhaust stroke, and the pistons of the third and fourth cylinders in the other group are synchronously driven to move in the second direction opposite to the first direction, so that the third and fourth cylinders in the other group respectively complete the intake stroke and the compression stroke.

[0010] Further, the racks of the two push rods are single-sided racks and are arranged opposite to each other; the two swing gears are both arranged between the racks of the two push rods, and the two swing gears are respectively engaged with the two racks; the rotation directions of the two transmission shafts are set to be opposite to each other.

[0011] Further, output gears for outputting torque are respectively arranged on the two transmission shafts.

[0012] Further, a coupling mechanism is arranged between the two transmission shafts to couple the power of the two transmission shafts, ensure that the output rotation direction remains unchanged, and output continuous and uninterrupted rotational power.

[0013] Further, the rack of one push rod is a single-sided rack, and the rack of the other push rod is a double-sided rack; one swing gear is arranged between the two push rods and is respectively engaged with the racks of the two push rods; the other swing gear is arranged on the side of the double-sided rack away from the single-sided rack and is engaged with the double-sided rack; the rotation directions of the two transmission shafts are the same.

[0014] Further, output gears for outputting torque are respectively arranged on the two transmission shafts.

[0015] Further, a coupling mechanism is arranged between the two transmission shafts to couple the power of the two transmission shafts, ensure that the output rotation direction remains unchanged, and output continuous and uninterrupted rotational power.

[0016] Through the technical solution provided by the present utility model, the following beneficial effects are achieved:

[0017] 1. The utility model can eliminate complex components such as push rods, crankshafts, high-pressure oil bearings, and high-pressure oil pumps in the prior art. It can not only reduce the overall cost, but also drive the corresponding swing gear to rotate through the push rod provided with a rack, thereby realizing the conversion of the linear reciprocating motion of the piston into a rotational motion to output power in a rotational form, which is used to drive a rotary generator with stable power generation efficiency to improve the conversion efficiency from mechanical energy to electrical energy. At the same time, it can improve the engine efficiency and can also be used as the direct power for driving vehicles such as HEV, PHEV, and REEV.

[0018] 2. The push rod of the utility model is arranged at the pressure center of the piston to ensure that the eccentric force generated by the push rod is very small and can be ignored, thereby reducing energy loss and improving engine efficiency.

[0019] 3. The force arm of the acting force of the push rod of the utility model on the transmission shaft is equal to the radius of the swing gear. At the beginning of the power stroke, it can quickly transfer the energy when the gas energy in the cylinder is the largest, reduce leakage and heat loss, and thus improve engine efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure shows a schematic diagram of a four-stroke free piston engine in the first stroke stage of Embodiment 1;

[0021] Figure 2 The figure shows a schematic diagram of a four-stroke free piston engine in the second stroke stage of Embodiment 1;

[0022] Figure 3 The figure shows a schematic diagram of a four-stroke free piston engine in the third stroke stage of Embodiment 1;

[0023] Figure 4 The figure shows a schematic diagram of a four-stroke free piston engine in the fourth stroke stage of Embodiment 1;

[0024] Figure 5 The figure shows a schematic diagram of the power output connection of the four-stroke free piston engine in Embodiment 1;

[0025] Figure 6 The figure shows another schematic diagram of the power output connection of the four-stroke free piston engine in Embodiment 1;

[0026] Figure 7 The figure shows a schematic diagram of a four-stroke free piston engine in the first stroke stage of Embodiment 2;

[0027] Figure 8 The figure shows a schematic diagram of a four-stroke free piston engine in the second stroke stage of Embodiment 2;

[0028] Figure 9 Shown is a schematic diagram of a four-stroke free-piston engine in the third stroke stage in the second embodiment;

[0029] Figure 10 Shown is a schematic diagram of a four-stroke free-piston engine in the fourth stroke stage in the second embodiment;

[0030] Figure 11 Shown is a schematic diagram of the power output connection of the four-stroke free-piston engine in the second embodiment. Detailed implementation manners

[0031] To further illustrate each embodiment, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used to explain the operating principle of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0032] Now, the present invention will be further described in conjunction with the accompanying drawings and the detailed implementation manners.

[0033] Embodiment 1

[0034] Referring to Figure 1 As shown, this embodiment provides a four-stroke free-piston engine (hereinafter simply referred to as a four-stroke engine). The four-stroke engine includes two groups of cylinders. Each group of cylinders includes two oppositely arranged cylinders. The four-stroke engine further includes a transmission assembly. The transmission assembly includes two rocking gears, one-way clutches and transmission shafts that cooperate with each rocking gear. The rocking gears are arranged to rotate about a fixed axis. The pistons of the two cylinders in each group are connected by a push rod. Rack teeth are respectively arranged on the two push rods. The two rocking gears are respectively meshed with the rack teeth of the two push rods. And the rocking gears are drivingly connected to the corresponding transmission shafts through the one-way clutches. The rocking gears perform rocking rotation about a fixed axis, such as clockwise rotation or counterclockwise rotation, while the transmission shafts perform unidirectional rotation.

[0035] Each cylinder sequentially completes an intake stroke, a compression stroke, a power stroke and an exhaust stroke, and forms a cycle. That is, each cylinder is respectively matched with a piston to form an airtight combustion chamber. The piston makes a reciprocating motion in the corresponding cylinder to change the volume of the combustion chamber. Moreover, when the piston moves from one end of the cylinder to the other end, that is, one stroke is completed, and a total of four strokes form a cycle, which are an intake stroke, a compression stroke, a power stroke and an exhaust stroke in sequence.

[0036] And there is always a piston of a cylinder doing work and synchronously driving the other three cylinders to complete the intake stroke, compression stroke, and exhaust stroke respectively. The locking directions of the two one-way clutches are set to be opposite to each other to ensure that one of the two transmission shafts outputs torque and the other idles. The idling direction of the transmission shaft is the same as the transmission rotation direction. That is, in any power stroke, there is always one one-way clutch locked to enable the corresponding swing gear and transmission shaft to transmit power, while the other one-way clutch disengages to enable the corresponding transmission shaft to rotate idly, so that one of the two transmission shafts outputs torque and the other idles. Moreover, whether the two transmission shafts are transmitting power or rotating idly, their respective rotation directions always remain unchanged. The one-way clutch characteristic enables the transmission shaft to continue to rotate along the transmission direction by inertia when idling.

[0037] In this embodiment, the racks of the two push rods are single-sided racks and are arranged opposite to each other. The two swing gears are both arranged between the racks of the two push rods, and the two swing gears are engaged with the two racks one by one. The rotation directions of the two transmission shafts are set to be opposite to each other, and output gears for outputting torque are respectively arranged on the two transmission shafts to achieve torque output.

[0038] During specific implementation, the two cylinders of one group are respectively the first cylinder 1a and the second cylinder 1b which are symmetrically arranged with a left and right spacing. The two cylinders of the other group are respectively the third cylinder 1d and the fourth cylinder 1c which are symmetrically arranged with a left and right spacing. Specifically, the first cylinder 1a, the second cylinder 1b, the third cylinder 1d, and the fourth cylinder 1c are all fixedly assembled on the housing of the four-stroke engine and are stationary.

[0039] A first combustion chamber and a first piston 2a are arranged in the first cylinder 1a, a second combustion chamber and a second piston 2b are arranged in the second cylinder 1b, a third combustion chamber and a third piston 2d are arranged in the third cylinder 1d, and a fourth combustion chamber and a fourth piston 2c are arranged in the fourth cylinder 1c. The two push rods are respectively the first push rod and the second push rod, and the racks of the first push rod and the second push rod are respectively the first rack 3a and the second rack 3b.

[0040] The first piston 2a and the second piston 2b are fixedly connected through the first push rod to enable the first piston 2a, the second piston 2b, and the first push rod to make left and right reciprocating linear motions together. The third piston 2d and the fourth piston 2c are fixedly connected through the second push rod to enable the third piston 2d, the fourth piston 2c, and the second push rod to make left and right reciprocating linear motions together.

[0041] The two swing gears are respectively the first swing gear 4a and the second swing gear 4b arranged on the left and right. The two one-way clutches are respectively the first one-way clutch 5a and the second one-way clutch 5b. The two transmission shafts are respectively the first transmission shaft 6a and the second transmission shaft 6b.

[0042] As Figure 5 shown, a first output gear 8a for outputting torque is assembled on the first transmission shaft 6a, and a second output gear 8b for outputting torque is assembled on the second transmission shaft 6b.

[0043] The first one-way clutch 5a and the first transmission shaft 6a are both assembled on the first swing gear 4a, and the first swing gear 4a and the first transmission shaft 6a are in transmission connection through the first one-way clutch 5a. In this embodiment, the first one-way clutch 5a is arranged as follows: when the first swing gear 4a rotates clockwise, the first one-way clutch 5a locks and transmits power; when the first swing gear 4a rotates counterclockwise, the first one-way clutch 5a disengages and allows the first transmission shaft 6a to rotate clockwise idly.

[0044] The second one-way clutch 5b and the second transmission shaft 6b are both assembled on the second swing gear 4b, and the second swing gear 4b and the second transmission shaft 6b are in transmission connection through the second one-way clutch 5b. In this embodiment, the second one-way clutch 5b is arranged as follows: when the second swing gear 4b rotates counterclockwise, the second one-way clutch 5b locks and transmits power; when the second swing gear 4b rotates clockwise, the second one-way clutch 5b disengages and allows the second transmission shaft 6b to rotate counterclockwise idly.

[0045] The first swing gear 4a meshes with the first rack 3a and the second rack 3b respectively, and the second swing gear 4b also meshes with the first rack 3a and the second rack 3b respectively.

[0046] The specific working principle of the four-stroke engine in this embodiment is as follows, and includes a first stroke stage as Figure 1 shown, a second stroke stage as Figure 2 shown, a third stroke stage as Figure 3 shown, and a fourth stroke stage as Figure 4 shown.

[0047] As Figure 1As shown in the figure, first, when the first piston 2a is in the intake stroke, the driving force in the first stroke stage comes from the fourth piston 2c in the fourth cylinder 1c. That is, the fuel in the fourth cylinder 1c burns and expands to do work, which is the power stroke. The fourth piston 2c is pushed to move leftward, and then the second rack 3b of the second push rod is driven to move leftward. Subsequently, the first swing gear 4a and the second swing gear 4b are driven to rotate clockwise, and then the first rack 3a of the first push rod is driven to move rightward. Moreover, the first push rod drives the first piston 2a to move rightward, and the volume in the first cylinder 1a increases, so as to inhale gas (such as air) or intake air without the need for high-pressure assistance. This is the intake stroke. The first push rod pushes the second piston 2b to move rightward to compress the gas in the second cylinder 1b. This is the compression stroke. The second push rod pushes the third piston 2d to move leftward to discharge the waste gas in the third cylinder 2d. This is the exhaust stroke.

[0048] In the first stroke stage, at this time, the first cylinder 1a is in the intake stroke, the second cylinder 1b is in the compression stroke, the fourth cylinder 1c is in the power stroke, and the third cylinder 1d is in the exhaust stroke. When the fourth cylinder 1c does work, the fourth piston 2c pushes the second rack 3b of the second push rod to move leftward, and then the first swing gear 4a and the second swing gear 4b are driven to rotate clockwise. The first swing gear 4a drives the first transmission shaft 6a to rotate clockwise and transmit power through the one-way clutch 5a. At the same time, the one-way clutch 5b is in a disengaged state, and the second swing gear 4b rotates relative to the second transmission shaft 6b and no transmission connection is formed. Therefore, the second transmission shaft 6b rotates idly counterclockwise. In short, the power output by the fourth piston 2c is transmitted to the first transmission shaft 6a through the first swing gear 4a and the one-way clutch 5a, and the first transmission shaft 6a is driven to rotate clockwise, while the second transmission shaft 6b rotates idly counterclockwise.

[0049] As Figure 2 shown in the figure, then when the first piston 2a is in the compression stroke, the driving force in the second stroke stage comes from the second piston 2b in the second cylinder 1b. That is, the fuel in the second cylinder 1b burns and expands to do work, which is the power stroke. The second piston 2b is pushed to move leftward, and the second piston 2b pushes the first rack 3a of the first push rod to move leftward, driving the first swing gear 4a and the second swing gear 4b to rotate counterclockwise, and then driving the second rack 3b of the second push rod to move rightward. Moreover, the first push rod drives the first piston 2a to move leftward and compress the gas in the first cylinder 2a. This is the compression stroke. The second push rod drives the fourth piston 2c to move rightward to discharge the waste gas in the fourth cylinder 2c. This is the exhaust stroke. The second rack 3b drives the third piston 2d to move rightward, the volume in the third cylinder 1d increases, and gas is inhaled. This is the intake stroke.

[0050] In the second stroke stage, the first cylinder 1a is in the compression stroke, the second cylinder 1b is in the power stroke, the fourth cylinder 1c is in the exhaust stroke, and the third cylinder 1d is in the intake stroke; when the second cylinder 1b is in the power stroke, the second piston 2b pushes the first rack 3a of the first push rod to move leftward, thereby driving the first swing gear 4a and the second swing gear 4b to rotate counterclockwise. The second swing gear 4b drives the second transmission shaft 6b to rotate counterclockwise and transmit power through the one-way clutch 5b. At the same time, the one-way clutch 5a is in a disengaged state, and the first swing gear 4a and the first transmission shaft 6a rotate relative to each other and no transmission connection is formed. Therefore, the first transmission shaft 6a idles clockwise. In short, the power output by the second piston 2b is transmitted to the second transmission shaft 6b through the second swing gear 4b and the one-way clutch 5b, and drives the second transmission shaft 6b to rotate counterclockwise, while the first transmission shaft 6a idles clockwise.

[0051] As Figure 3 shown, then when the first piston 2a is in the power stroke, the driving force in the third stroke stage comes from the first piston 2a of the first cylinder 1a, that is, the fuel in the first cylinder 1a burns and expands to do work, which is the power stroke, and pushes the first piston 2a to move rightward, pushing the first rack 3a of the first push rod to move rightward, thereby driving the first swing gear 4a and the second swing gear 4b to rotate clockwise, and then driving the second rack 3b of the second push rod to move leftward; moreover, the first push rod drives the second piston 2b to move rightward to discharge the waste gas in the second cylinder 1b, which is the exhaust stroke; the second push rod drives the fourth piston 2c to move leftward, the volume in the fourth cylinder 1c increases, and gas is inhaled, which is the intake stroke; the second push rod drives the third piston 2d to move leftward to compress the gas in the third cylinder 1d, which is the compression stroke.

[0052] In the third stroke stage, the first cylinder 1a is in the power stroke, the second cylinder 1b is in the exhaust stroke, the fourth cylinder 1c is in the intake stroke, and the third cylinder 1d is in the compression stroke; when the first cylinder 1a is in the power stroke, the first piston 2a pushes the first rack 3a of the first push rod to move rightward, thereby driving the first swing gear 4a and the second swing gear 4b to rotate clockwise. The first swing gear 4a drives the first transmission shaft 6a to rotate clockwise and transmit power through the one-way clutch 5a. At the same time, the one-way clutch 5b is in a disengaged state, and the second swing gear 4b and the second output gear 8b rotate relative to each other and no transmission connection is formed. Therefore, the second transmission shaft 6b idles counterclockwise. In short, the power output by the first piston 2a is transmitted to the first transmission shaft 6a through the first swing gear 4a and the one-way clutch 5a, and drives the first transmission shaft 6a to rotate clockwise, while the second transmission shaft 6b idles counterclockwise.

[0053] As Figure 4As shown, finally, when the first piston 2a is in the exhaust stroke, the driving force in the fourth stroke stage comes from the third piston 2d in the third cylinder 1d, that is, the fuel in the third cylinder 1d burns and expands to do work. This is the power stroke, which pushes the third piston 2d to move to the right. The third piston 2d pushes the second rack 3b of the second push rod to move to the right, driving the first swing gear 4a and the second swing gear 4b to rotate counterclockwise. Furthermore, it drives the first rack 3a of the first push rod to move to the left. Moreover, the first push rod drives the first piston 2a to move to the left to discharge the waste gas in the first cylinder 1a. This is the exhaust stroke. The first push rod drives the second piston 2b to move to the left, increasing the volume in the second cylinder 1b and sucking in gas. This is the intake stroke. The second push rod drives the fourth piston 2c to move to the right to compress the gas in the fourth cylinder 2c. This is the compression stroke.

[0054] In the fourth stroke stage, at this time, the first cylinder 1a is in the exhaust stroke, the second cylinder 1b is in the intake stroke, the fourth cylinder 1c is in the compression stroke, and the third cylinder 1d is in the power stroke. When the third cylinder 1d does work, the third piston 2d pushes the second rack 3b of the second push rod to move to the right, further driving the first swing gear 4a and the second swing gear 4b to rotate counterclockwise. The second swing gear 4b drives the second transmission shaft 6b to rotate counterclockwise and transmit power through the one-way clutch 5b. At the same time, the one-way clutch 5a is in the disengaged state, and the first swing gear 4a rotates relative to the first transmission shaft 6a and no transmission connection is formed. Therefore, the first transmission shaft 6a idles clockwise. In short, the power output by the third piston 2d is transmitted to the second transmission shaft 6b through the second swing gear 4b and the one-way clutch 5b, driving the second transmission shaft 6b to rotate counterclockwise, while the first transmission shaft 6a idles clockwise.

[0055] The above four strokes constitute a complete working cycle of a four-stroke engine, that is, the cylinders sequentially enter the intake stroke, compression stroke, power stroke, and exhaust stroke, repeating in a cycle. In each stroke, there is always one cylinder intake, another cylinder compression, the third cylinder doing work, and the fourth cylinder exhausting.

[0056] In addition, the power generated by the cylinder work in the first stroke stage and the third stroke stage is output through the first transmission shaft 6a and rotates clockwise. At the same time, the second transmission shaft 6b idles counterclockwise.

[0057] The power generated by the cylinder work in the second stroke stage and the fourth stroke stage is output through the second transmission shaft 6b and rotates counterclockwise. At the same time, the first transmission shaft 6a idles clockwise.

[0058] In summary, the first transmission shaft 6a can maintain clockwise rotation and alternate between driving and idling, and the second transmission shaft 6b can also maintain counterclockwise rotation and alternate between idling and driving. In this way, the first transmission shaft 6a and the second transmission shaft 6b alternate between driving and idling, and there is always one transmission shaft driving in each stroke, and the power is output through the first output gear 8a or the second output gear 8b respectively.

[0059] Within one cycle of the four-stroke engine of this embodiment, the four-stroke engine of this embodiment has variable stroke and compression ratio. The variable compression ratio allows the use of different fuels to improve the flexibility and adaptability of the engine, and can also promote HCCI combustion to ensure a higher thermal efficiency (i.e., the thermal efficiency is not less than 60%), and can also improve the potential of SI-HCCI transition through the variable compression ratio.

[0060] The four-stroke engine of this embodiment can eliminate complex components such as push rods, crankshafts, high-pressure oil bearings, and high-pressure oil pumps in the prior art. It can not only reduce the overall cost, but also realize the conversion of the linear reciprocating motion of the piston into rotational motion by pushing the corresponding swing gear with a push rod provided with a rack, so as to output rotational power for driving a rotary generator with stable power generation efficiency, improve the conversion efficiency from mechanical energy to electrical energy, and at the same time improve the engine efficiency. It can also be used as the direct power for driving vehicles such as HEV, PHEV, and REEV.

[0061] The push rod of this embodiment is arranged at the pressure center of the piston to ensure that the eccentric force generated by the push rod is very small and can be ignored, thereby reducing energy loss and improving engine efficiency.

[0062] The lever arm of the force of the push rod of this embodiment on the transmission shaft is equal to the radius of the swing gear. At the beginning of the power stroke, when the gas energy in the cylinder is the largest, the energy can be quickly transmitted, reducing leakage and heat loss, thereby improving engine efficiency.

[0063] In addition, the 4 cylinders of this embodiment cooperate and work in coordination to achieve a four-stroke cycle. The two push rods are arranged in parallel, with a swing gear arranged in the middle and meshing with the racks respectively to ensure that the two racks are motion-coupled through the swing gear. Compared with the existing two-stroke engine, the four-stroke engine of this embodiment is provided with an exhaust stroke and an intake stroke to ensure high-quality exhaust and intake. The driving force formed by the power stroke drives the piston to squeeze out the exhaust gas, and there is very little exhaust gas residue. In the next stroke, the piston movement forms a negative pressure in the cylinder to attract air to enter, improving the scavenging efficiency. In addition, the fresh gas containing fuel will not be short-circuited and discharged, avoiding fuel loss, and can also achieve a larger effective compression ratio, being more suitable for the HCCI combustion cycle, improving efficiency, and can also use the components of the existing four-stroke engine, reducing the manufacturing cost.

[0064] Moreover, when the piston is around the top dead center, its acceleration is significantly higher, thereby reducing the residence time at high temperatures and decreasing the heat transfer loss during the combustion process. When the piston is around the bottom dead center, the force arm of the push rod does not decrease, and the output power attenuation is small, so as to achieve small output power fluctuations.

[0065] In addition, compared with the prior art piston engines that have strong vibrations in the three axes directions such as the x-axis, y-axis, and z-axis, the four-stroke engine of this embodiment only has strong vibrations in one direction (i.e., the moving direction of the piston along the left and right), and the NVH (NVH includes noise, vibration, and harshness) characteristics are significantly improved.

[0066] Of course, in other embodiments, a coupling mechanism may also be provided between the two transmission shafts to couple the power of the two transmission shafts, ensure that the output rotation direction remains unchanged, and output continuous and uninterrupted rotational power.

[0067] As Figure 6 shown, when the first swing gear 4a and the second swing gear 4b rotate clockwise, the first transmission shaft 6a rotates clockwise, and the power is directly output through the output gear 8 to achieve clockwise rotation of the output gear 8 and output torque. At the same time, the second transmission shaft 6b idles counterclockwise; when the first swing gear 4a and the second swing gear 4b rotate counterclockwise, the first transmission shaft 6a idles clockwise, the second transmission shaft 6b rotates counterclockwise and transmits power, drives the second coupling gear 7b to rotate counterclockwise, synchronously drives the first coupling gear 7a to rotate clockwise and transmit power, and the first coupling gear 7a drives the output gear 8 to rotate clockwise and output power. In this way, it can be ensured that the output gear 8 continuously outputs power and torque and maintains clockwise rotation.

[0068] Embodiment Two

[0069] Refer to Figure 7As shown, the second embodiment provides a four-stroke free piston engine. The structure of the second embodiment is substantially the same as that of the first embodiment, except that: the rack of the first push rod is a double-sided rack 3a', and the rack of the second push rod is a single-sided rack 3b'; the first swing gear 4a is arranged between the two push rods and meshes with the racks of the two push rods respectively, and the second swing gear 4b is arranged on the side of the double-sided rack 3a' away from the single-sided rack 3b' and meshes with the double-sided rack 3a'; when the first swing gear 4a rotates clockwise, the second swing gear 4b rotates counterclockwise, Vice versa; the first one-way clutch 5a is arranged such that when the first swing gear 4a rotates clockwise, the first one-way clutch 5a is locked and transmits power; when the first swing gear 4a rotates counterclockwise, the first one-way clutch 5a is separated and the first transmission shaft 6a is allowed to idle clockwise; the second one-way clutch 5b is arranged such that when the second swing gear 4b rotates clockwise, the second one-way clutch 5b is locked and transmits power; when the second swing gear 4b rotates counterclockwise, the second one-way clutch 5b is separated and the second transmission shaft 6b is allowed to idle clockwise. The rotation directions of the two transmission shafts are the same, and such a layout can shorten the length of the cylinder axis.

[0070] In this specific embodiment, Figure 11 As shown, the two transmission shafts are respectively provided with a first gear 9a and a second gear 9b, and the first gear 9a and the second gear 9b are both engaged with a coupling gear 10 to form a coupling mechanism for alternately transmitting power. The coupling gear 10 is equipped with a connecting shaft, and the connecting shaft is provided with an output gear 8 for outputting torque.

[0071] The specific working principle of the four-stroke engine of this embodiment is as follows, and includes the following steps: Figure 7 The first stroke stage shown, Figure 8 The second stroke stage shown in Figure 9 The third stroke stage shown and Figure 10 The fourth stroke stage is shown.

[0072] like Figure 7As shown in the figure, first, when the first piston 2a is in the intake stroke, the driving force in the first stroke stage comes from the fourth piston 2c of the fourth cylinder 1c. That is, the fuel in the fourth cylinder 1c burns and expands to do work. This is the power stroke, which pushes the fourth piston 2c to move leftward, and then pushes the single-sided rack 3b' of the second push rod to move leftward. Then it drives the first swing gear 4a to rotate clockwise, and further drives the double-sided rack 3a' of the first push rod to move rightward. Then the double-sided rack 3a' drives the second swing gear 4b to rotate counterclockwise; moreover, the first push rod drives the first piston 2a to move rightward, the volume in the first cylinder 1a increases, and gas is inhaled. This is the intake stroke; the first push rod pushes the second piston 2b to move rightward, compressing the gas in the second cylinder 1b. This is the compression stroke; the second push rod pushes the third piston 2d to move leftward, discharging the waste gas in the third cylinder 2d. This is the exhaust stroke.

[0073] In the first stroke stage, at this time, the first cylinder 1a is in the intake stroke, the second cylinder 1b is in the compression stroke, the fourth cylinder 1c is in the power stroke, and the third cylinder 1d is in the exhaust stroke; when the fourth cylinder 1c does work, the fourth piston 2c pushes the single-sided rack 3b' of the second push rod to move leftward, and then drives the first swing gear 4a to rotate clockwise. The first swing gear 4a drives the first transmission shaft 6a to rotate clockwise and transmit power through the one-way clutch 5a; at the same time, the double-sided rack 3a' drives the second swing gear 4b to rotate counterclockwise, and the one-way clutch 5b is in a disengaged state. The second swing gear 4b rotates relative to the second transmission shaft 6b and no transmission connection is formed. Therefore, the second transmission shaft 6b rotates idly clockwise. In short, the power output by the fourth piston 2c is transmitted to the first transmission shaft 6a through the first swing gear 4a and the one-way clutch 5a, and drives the first transmission shaft 6a to rotate clockwise, while the second transmission shaft 6b rotates idly clockwise.

[0074] As Figure 8 shown in the figure, then when the first piston 2a is in the compression stroke, the driving force in the second stroke stage comes from the second piston 2b of the second cylinder 1b. That is, the fuel in the second cylinder 1b burns and expands to do work. This is the power stroke, which pushes the second piston 2b to move leftward. The second piston 2b pushes the double-sided rack 3a' of the first push rod to move leftward, driving the first swing gear 4a to rotate counterclockwise. Synchronously, the double-sided rack 3a' drives the second swing gear 4b to rotate clockwise, and the first swing gear 4a drives the single-sided rack 3b' of the second push rod to move rightward; moreover, the first push rod drives the first piston 2a to move leftward and compresses the gas in the first cylinder 2a. This is the compression stroke; the second push rod drives the fourth piston 2c to move rightward, discharging the waste gas in the fourth cylinder 2c. This is the exhaust stroke; the single-sided rack 3b' drives the third piston 2d to move rightward, the volume in the third cylinder 1d increases, and gas is inhaled. This is the intake stroke.

[0075] In the second stroke stage, the first cylinder 1a is in the compression stroke, the second cylinder 1b is in the power stroke, the fourth cylinder 1c is in the exhaust stroke, and the third cylinder 1d is in the intake stroke. When the second cylinder 1b performs work, the second piston 2b pushes the double-sided rack 3a' of the first push rod to move leftward, thereby driving the first swing gear 4a to rotate counterclockwise. The second swing gear 4b drives the second transmission shaft 6b to rotate counterclockwise and transmit power through the one-way clutch 5b. At the same time, the double-sided rack 3a' drives the first swing gear 4a to rotate counterclockwise, and the one-way clutch 5a is in a disengaged state. The first swing gear 4a and the first transmission shaft 6a rotate relative to each other and no transmission connection is formed. Therefore, the first transmission shaft 6a idles clockwise. In short, the power output by the second piston 2b is transmitted to the second transmission shaft 6b through the second swing gear 4b and the one-way clutch 5b, and drives the second transmission shaft 6b to rotate clockwise, while the first transmission shaft 6a idles clockwise.

[0076] As Figure 9 shown, then when the first piston 2a is in the power stroke, the driving force in the third stroke stage comes from the first piston 2a of the first cylinder 1a, that is, the fuel in the first cylinder 1a burns and expands to do work, which is the power stroke, and pushes the first piston 2a to move rightward, pushing the double-sided rack 3a' of the first push rod to move rightward, thereby driving the first swing gear 4a to rotate clockwise, and then driving the single-sided rack 3b' of the second push rod to move leftward. Then the double-sided rack 3a' drives the second swing gear 4b to rotate counterclockwise. Moreover, the first push rod drives the second piston 2b to move rightward, discharging the waste gas in the second cylinder 1b, which is the exhaust stroke. The second push rod drives the fourth piston 2c to move leftward, the volume in the fourth cylinder 1c increases, and gas is inhaled, which is the intake stroke. The second push rod drives the third piston 2d to move leftward, compressing the gas in the third cylinder 1d, which is the compression stroke.

[0077] In the third stroke stage, the first cylinder 1a is in the power stroke, the second cylinder 1b is in the exhaust stroke, the fourth cylinder 1c is in the intake stroke, and the third cylinder 1d is in the compression stroke. When the first cylinder 1a performs work, the first piston 2a pushes the double-sided rack 3a' of the first push rod to move rightward, thereby driving the first swing gear 4a to rotate clockwise. The first swing gear 4a drives the first transmission shaft 6a to rotate clockwise and transmit power through the one-way clutch 5a. At the same time, the double-sided rack 3a' drives the second swing gear 4b to rotate counterclockwise, and the one-way clutch 5b is in a disengaged state. The second swing gear 4b and the second output gear 8b rotate relative to each other and no transmission connection is formed. Therefore, the second transmission shaft 6b idles clockwise. In short, the power output by the first piston 2a is transmitted to the first transmission shaft 6a through the first swing gear 4a and the one-way clutch 5a, and drives the first transmission shaft 6a to rotate clockwise, while the second transmission shaft 6b idles clockwise.

[0078] As shown Figure 10 in the figure, finally, when the first piston 2a is in the exhaust stroke, the driving force in the fourth stroke stage comes from the third piston 2d in the third cylinder 1d, that is, the fuel in the third cylinder 1d burns and expands to do work. This is the power stroke, and it pushes the third piston 2d to move to the right. The third piston 2d pushes the single-sided rack 3b' of the second push rod to move to the right, driving the first swing gear 4a to rotate counterclockwise, and the first swing gear 4a drives the double-sided rack 3a' of the first push rod to move to the left, thereby driving the second swing gear 4b to rotate clockwise; moreover, the first push rod drives the first piston 2a to move to the left, discharging the exhaust gas in the first cylinder 1a. This is the exhaust stroke; the first push rod drives the second piston 2b to move to the left, increasing the volume in the second cylinder 1b and sucking in gas. This is the intake stroke; the second push rod drives the fourth piston 2c to move to the right, compressing the gas in the fourth cylinder 2c. This is the compression stroke.

[0079] In the fourth stroke stage, at this time, the first cylinder 1a is in the exhaust stroke, the second cylinder 1b is in the intake stroke, the fourth cylinder 1c is in the compression stroke, and the third cylinder 1d is in the power stroke; when the third cylinder 1d does work, the third piston 2d pushes the single-sided rack 3b' of the second push rod to move to the right, thereby driving the first swing gear 4a to rotate counterclockwise, and the first push rod drives the second swing gear 4b to rotate clockwise. The second swing gear 4b drives the second transmission shaft 6b to rotate clockwise and transmit power through the one-way clutch 5b. At the same time, the double-sided rack 3a' drives the first swing gear 4a to rotate counterclockwise, and the one-way clutch 5a is in a disengaged state. The first swing gear 4a and the first transmission shaft 6a rotate relative to each other and no transmission connection is formed. Therefore, the first transmission shaft 6a rotates idly clockwise. In short, the power output by the third piston 2d is transmitted to the second transmission shaft 6b through the second swing gear 4b and the one-way clutch 5b, driving the second transmission shaft 6b to rotate clockwise, while the first transmission shaft 6a rotates idly clockwise.

[0080] All in all, the first transmission shaft 6a can maintain clockwise rotation and alternate between transmission and idling, and the second transmission shaft 6b can also maintain clockwise rotation and alternate between idling and transmission. In this way, the first transmission shaft 6a and the second transmission shaft 6b alternate between transmission and idling. There is always one transmission shaft in transmission in each stroke and they are respectively output through the first output gear 8a or the second output gear 8b, rotating clockwise. Of course, in other embodiments, output gears for outputting torque can also be respectively provided on the two transmission shafts as shown Figure 5 in the figure.

[0081] As shown Figure 11As shown, when the first swing gear 4a rotates clockwise and the second swing gear 4b rotates counterclockwise, the first transmission shaft 6a is driven clockwise, driving the first gear 9a to rotate clockwise and driving the output gear 8 to rotate counterclockwise to output power. At the same time, the second transmission shaft 6b idles clockwise; when the first swing gear 4a rotates counterclockwise and the second swing gear 4b rotates clockwise, the first transmission shaft 6a idles clockwise, the second transmission shaft 6b rotates clockwise and transmits power, driving the second gear 9b to rotate clockwise and driving the output gear 8 to rotate counterclockwise to output power. At the same time, the first transmission shaft 6b idles clockwise. In this way, it can ensure that the output gear 8 continuously outputs power and torque and keeps rotating counterclockwise.

[0082] Embodiment III

[0083] Embodiment III provides a four-stroke free piston engine. The structure of Embodiment III is generally the same as that of Embodiment I, except that: the two push rods are integrally connected and move in the same direction synchronously. The racks on the two push rods are arranged on the same side. The two swing gears are both arranged on the rack sides of the two push rods, and the rotation directions of the two transmission shafts are set to be opposite to each other.

[0084] In this embodiment, the two push rods are integrally connected to form an integral push rod, and then connected to each other through the gears of the two racks to form a new rack on the integral push rod. The new rack and the two swing gears are both arranged on the same side of the two push rods, and the two swing gears are engaged with the new rack. In this way, it can also ensure that the piston of one cylinder is always doing work and synchronously driving the other three cylinders to complete the intake stroke, compression stroke, and exhaust stroke respectively.

[0085] Of course, in other embodiments, the gears of the two racks can also be independent of each other, and the gears of the two swing gears are relatively wide to overcome the distance between the two racks, so as to ensure that the two swing gears are engaged with the two racks one by one.

[0086] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them fall within the protection scope of the present invention.

Claims

1. A four-stroke free piston engine, comprising two groups of cylinders, each group of cylinders comprising two cylinders arranged opposite to each other, characterized in that: Also includes a transmission assembly; The transmission assembly includes two swing gears and a one-way clutch and a transmission shaft matching each swing gear, and the swing gear is arranged to rotate on a fixed axis; The pistons of the two cylinders of each group are connected by a push rod, and the two push rods are respectively provided with racks, one of the swing gears is respectively engaged with the racks of the two push rods, and the other swing gear is engaged with the rack of at least one push rod, and the swing gear is connected to the corresponding transmission shaft through the one-way clutch; Each cylinder completes the intake stroke, compression stroke, power stroke and exhaust stroke in sequence to form a cycle, and there is always a piston of one cylinder doing work, and synchronously drives the other three cylinders to complete the intake stroke, compression stroke and exhaust stroke respectively, and the locking directions of the two one-way clutches are set to be opposite to each other to ensure that one of the two transmission shafts is outputting torque and the other is idling, and the idling direction of the transmission shaft is the same as the transmission rotation direction.

2. The four-stroke free piston engine according to claim 1, characterized in that: One cylinder of one group generates a driving force during a power stroke to push its piston to move toward a first direction; and through the transmission assembly, drives the piston of another cylinder in the same group to move toward the first direction and realize a compression stroke, and synchronously drives the pistons of the third cylinder and the fourth cylinder of the other group to move toward a second direction opposite to the first direction, so that the third cylinder and the fourth cylinder of the other group respectively complete an intake stroke and an exhaust stroke; or drives the piston of another cylinder in the same group to move toward the first direction and realize an exhaust stroke, and synchronously drives the pistons of the third cylinder and the fourth cylinder of the other group to move toward the second direction opposite to the first direction, so that the third cylinder and the fourth cylinder of the other group respectively complete an intake stroke and a compression stroke.

3. The four-stroke free piston engine according to claim 1 or 2, characterized in that: The racks of the two push rods are single-sided racks and are arranged opposite to each other; the two swing gears are arranged between the racks of the two push rods, and the two swing gears are meshed with the two racks one by one; the rotation directions of the two transmission shafts are arranged to be opposite to each other.

4. The four-stroke free piston engine according to claim 3, characterized in that: The two transmission shafts are respectively provided with output gears for outputting torque.

5. The four-stroke free piston engine according to claim 3, characterized in that: A coupling mechanism is provided between the two transmission shafts to couple the power of the two transmission shafts and ensure that the output rotation direction remains unchanged and the output rotation power is continuous and uninterrupted.

6. The four-stroke free piston engine according to claim 1 or 2, characterized in that: The rack of one of the push rods is a single-sided rack, and the rack of the other push rod is a double-sided rack; one of the swing gears is arranged between the two push rods and meshes with the racks of the two push rods respectively; the other swing gear is arranged on the side of the double-sided rack away from the single-sided rack, and meshes with the double-sided rack; the rotation directions of the two transmission shafts are the same.

7. The four-stroke free piston engine according to claim 6, characterized in that: The two transmission shafts are respectively provided with output gears for outputting torque.

8. The four-stroke free piston engine according to claim 6, characterized in that: A coupling mechanism is provided between the two transmission shafts to couple the power of the two transmission shafts and ensure that the output rotation direction remains unchanged and the output rotation power is continuous and uninterrupted.

9. The four-stroke free piston engine according to claim 1, characterized in that: The two push rods are integrally connected and move synchronously in the same direction; the racks on the two push rods are arranged on the same side, the two swing gears are arranged on the rack sides of the two push rods, and the two swing gears are meshed with the two racks one by one; the rotation directions of the two transmission shafts are arranged to be opposite to each other.

10. The four-stroke free piston engine according to claim 9, characterized in that: The gears of the two racks are connected one by one; or the gears of the two racks are independent of each other.

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