Four-stroke free piston engine

Abstract

The invention discloses a four-stroke free piston engine which comprises two sets of air cylinders, two swing gears, a one-way clutch and a transmission shaft, and each set of air cylinders comprises two opposite air cylinders. 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] This invention relates to the field of engine technology, and in particular to a four-stroke free piston engine. Background Technology

[0002] Hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and range-extended electric vehicles (REEV) are the main technological routes for energy-saving and new energy vehicles. What they have in common 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. Moreover, HEV, PHEV, and REEV all need to maximize the energy conversion efficiency of the engine.

[0003] The power generated by existing piston engines with crankshafts is transmitted from the piston to the pushrod, which then transmits the power to the crankshaft via the crank, thus converting it into rotational motion and outputting power. Due to the limitations of the pushrod and crankshaft, the piston stroke is fixed, so the compression ratio cannot be adjusted or optimized according to power requirements, which limits the system's thermal efficiency. Furthermore, when the piston is working, the pushrod applies a reaction force, the lateral component of which presses the piston tightly against the cylinder wall, greatly increasing friction and energy loss. Furthermore, constrained by their operating mode, most piston engines are two-stroke engines, including a compression stroke and a power stroke. At the end of the compression stroke (top dead center), the compressed gas mixture in the cylinder is ignited, and at the end of the power stroke (bottom dead center), scavenging occurs to expel exhaust gas and introduce air and gas. However, the scavenging time is very short, requiring air pressurization to force the exhaust gas out of the cylinder. Alternatively, during the gas exchange process, some exhaust gas may remain in the cylinder, while some fresh air may be entrained in the exhaust stream. This situation is called short-circuit loss, which also affects the efficiency of the entire power system.

[0004] At the beginning of the power stroke, the pressure inside the cylinder is at its highest, but the crankshaft is near top dead center, the pushrod lever arm on the crankshaft is very small, resulting in a smaller torque and therefore a smaller power output. Simultaneously, the energy contained in the high-temperature, high-pressure combustion gases is released more slowly, and energy losses due to gas leakage and heat loss also increase. Towards the end of the power stroke, the crankshaft is near bottom dead center, the pushrod lever arm on the crankshaft is also small, and the pressure inside the cylinder is lower, resulting in another lower power output. This reduces the engine's power density and increases power output fluctuations.

[0005] Furthermore, the loads between the pushrod and the crankshaft, and between the crankshaft and the housing, are substantial, resulting in significant frictional losses. High-pressure oil bearings are required, which in turn necessitate a high-pressure oil source and a high-pressure oil pump. This necessitates additional energy to drive the high-pressure oil pump, leading to a reduction in engine output power and efficiency. Since the high-pressure oil bearings of the pushrod and crankshaft are both moving parts, complex high-pressure oil circuits are needed to deliver high-pressure lubricating oil to them. These circuits must pass through moving components such as the crankshaft, crankshaft, and pushrod, increasing the manufacturing difficulty and cost of these components. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a four-stroke free piston engine that eliminates complex components such as pushrods, crankshafts, high-pressure oil bearings, and high-pressure oil pumps found in existing technologies. It also transforms the linear reciprocating motion of the piston into rotary motion to output rotational power, thereby improving engine efficiency and making it suitable as an engine for vehicles such as HEVs, PHEVs, and REEVs.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] This invention provides a four-stroke free piston engine, comprising two sets of cylinders, each set including two opposing cylinders, and a transmission assembly. The transmission assembly includes two rocker gears, a one-way clutch engaging with each rocker gear, and a transmission shaft. The rocker gears are fixed-axis rotating configurations. The pistons of the two cylinders in each set are connected by a push rod, each push rod having a rack. One rocker gear meshes with the racks of both push rods, and the other rocker gear meshes with at least one push rod rack. The rocker gears are connected to their corresponding transmission shafts via the one-way clutches. Each cylinder sequentially completes the intake stroke, compression stroke, power stroke, and exhaust stroke, forming a cycle. At least one cylinder's piston is always performing a power stroke, simultaneously driving the other three cylinders to complete their respective intake, compression, and exhaust strokes. The locking directions of the two one-way clutches are opposite to each other, ensuring that one of the transmission shafts outputs torque while the other idles, with the idle direction of the transmission shaft being the same as the rotation direction.

[0009] Furthermore, during the power stroke, one cylinder in one group generates a driving force to push its piston towards a first direction; and through the transmission assembly, it drives the piston of another cylinder in the same group to move towards the first direction to achieve the compression stroke, simultaneously driving the pistons of the third and fourth cylinders in another group to move towards a 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 it drives the piston of another cylinder in the same group to move towards the first direction to achieve the exhaust stroke, simultaneously driving the pistons of the third and fourth cylinders in another group to move towards a 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] Furthermore, the racks of the two push rods are single-sided racks and are arranged opposite to each other; the two rocker gears are both arranged between the racks of the two push rods, and the two rocker gears mesh with the two racks one by one; the rotation directions of the two drive shafts are set to be opposite to each other.

[0011] Furthermore, each of the two drive shafts is equipped with an output gear for outputting torque.

[0012] Furthermore, a coupling mechanism is provided between the two drive shafts to couple the power of the two drive shafts, ensuring that the output rotation direction remains unchanged and that the output rotational power is continuous and uninterrupted.

[0013] Furthermore, one of the push rods has a single-sided rack, and the other push rod has a double-sided rack; one rocker gear is disposed between the two push rods and meshes with the racks of the two push rods respectively; another rocker gear is disposed 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 drive shafts are the same.

[0014] Furthermore, each of the two drive shafts is equipped with an output gear for outputting torque.

[0015] Furthermore, a coupling mechanism is provided between the two drive shafts to couple the power of the two drive shafts, ensuring that the output rotation direction remains unchanged and that the output rotational power is continuous and uninterrupted.

[0016] The technical solution provided by this invention has the following beneficial effects:

[0017] 1. This invention eliminates the need for complex components such as push rods, crankshafts, high-pressure oil bearings, and high-pressure oil pumps found in existing technologies. This not only reduces overall costs but also transforms the linear reciprocating motion of the piston into rotational motion by using a push rod equipped with a rack to drive a corresponding rocker gear. This outputs rotational power to drive a rotary generator with stable power generation efficiency, thereby improving the conversion efficiency of mechanical energy into electrical energy. It also improves engine efficiency and can be used as a direct power source for driving HEV, PHEV, and REEV vehicles.

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

[0019] 3. The lever arm of the push rod force of the present invention relative to the drive shaft is equal to the radius of the rocker gear. At the beginning of the power stroke, when the combustion energy in the cylinder is at its maximum, the energy can be quickly transferred out, reducing leakage and heat loss, thereby improving engine efficiency. Attached Figure Description

[0020] Figure 1 The diagram shown is a schematic of a four-stroke free piston engine in the first stroke stage of Embodiment 1.

[0021] Figure 2 The diagram shown is a schematic of a four-stroke free piston engine in the second stroke stage in Embodiment 1.

[0022] Figure 3 The diagram shown is a schematic of a four-stroke free piston engine in the third stroke stage in Embodiment 1.

[0023] Figure 4 The diagram shown is a schematic of a four-stroke free piston engine in the fourth stroke stage in Embodiment 1.

[0024] Figure 5 The diagram shown is a schematic diagram of the power output connection of the four-stroke free piston engine in Embodiment 1.

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

[0026] Figure 7 The diagram shown is a schematic of a four-stroke free piston engine in the first stroke stage in Embodiment 2.

[0027] Figure 8 The diagram shown is a schematic of a four-stroke free piston engine in the second stroke stage in Embodiment 2.

[0028] Figure 9The diagram shown is a schematic of a four-stroke free piston engine in the third stroke stage in Embodiment 2.

[0029] Figure 10 The diagram shown is a schematic of a four-stroke free piston engine in the fourth stroke stage in Embodiment 2.

[0030] Figure 11 The diagram shown is a schematic diagram of the power output connection of the four-stroke free piston engine in Embodiment 2. Detailed Implementation

[0031] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0032] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] Reference Figure 1 As shown, this embodiment provides a four-stroke free piston engine (hereinafter referred to as a four-stroke engine). The four-stroke engine includes two sets of cylinders, each set of cylinders including two cylinders arranged opposite each other. The four-stroke engine also includes a transmission assembly, which includes two rocker gears, a one-way clutch that engages with each rocker gear, and a transmission shaft. The rocker gears are fixed-axis rotating. The pistons of the two cylinders in each set are connected by a push rod. The two push rods are respectively provided with racks. The two rocker gears mesh with the racks of the two push rods respectively. The rocker gears are connected to the corresponding transmission shafts through the one-way clutches. The rocker gears perform fixed-axis rocker rotation, such as clockwise or counterclockwise rotation, while the transmission shaft rotates in one direction.

[0035] Each cylinder sequentially completes the intake stroke, compression stroke, power stroke, and exhaust stroke, forming a cycle. Each cylinder is matched with a piston, forming a hermetically sealed combustion chamber. The piston moves back and forth in its corresponding cylinder to change the volume of the combustion chamber. The piston moves from one end of the cylinder to the other to complete one stroke. There are a total of four strokes forming a cycle, namely the intake stroke, compression stroke, power stroke, and exhaust stroke.

[0036] Furthermore, one cylinder's piston is always performing power strokes, simultaneously driving the other three cylinders to complete the intake, compression, and exhaust strokes respectively. The locking directions of the two one-way clutches are set to be opposite to each other, ensuring that one of the two drive shafts is outputting torque while the other is idling. The idling direction of the drive shaft is the same as the transmission rotation direction. That is, in any power stroke, one one-way clutch is always locked, causing the corresponding rocker gear and drive shaft to transmit power, while the other one-way clutch is disengaged, causing the corresponding drive shaft to rotate without load. This ensures that one of the two drive shafts is outputting torque while the other is idling, and the rotation direction of each drive shaft remains unchanged whether it is transmitting power or rotating without load. The one-way engagement characteristic of the one-way clutch allows the drive shaft to continue rotating along the transmission direction and by inertia when unloaded.

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

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

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

[0040] The first piston 2a and the second piston 2b are fixedly connected by the first push rod, so that the first piston 2a, the second piston 2b and the first push rod can make a left and right reciprocating linear motion together. The third piston 2d and the fourth piston 2c are fixedly connected by the second push rod, so that the third piston 2d, the fourth piston 2c and the second push rod can make a left and right reciprocating linear motion together.

[0041] The two rocker gears are a first rocker gear 4a and a second rocker gear 4b, which are set on the left and right respectively. The two one-way clutches are a first one-way clutch 5a and a second one-way clutch 5b respectively. The two drive shafts are a first drive shaft 6a and a second drive shaft 6b respectively.

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

[0043] Both the first one-way clutch 5a and the first drive shaft 6a are mounted on the first rocker gear 4a, and the first rocker gear 4a and the first drive shaft 6a are connected by the first one-way clutch 5a. In this embodiment, the first one-way clutch 5a is configured as follows: when the first rocker gear 4a rotates clockwise, the first one-way clutch 5a locks and transmits power; when the first rocker gear 4a rotates counterclockwise, the first one-way clutch 5a disengages, allowing the first drive shaft 6a to rotate clockwise freely.

[0044] The second one-way clutch 5b and the second drive shaft 6b are both mounted on the second rocker gear 4b, and the second rocker gear 4b and the second drive shaft 6b are connected by the second one-way clutch 5b. In this embodiment, the second one-way clutch 5b is configured as follows: when the second rocker gear 4b rotates counterclockwise, the second one-way clutch 5b locks and transmits power; when the second rocker gear 4b rotates clockwise, the second one-way clutch 5b disengages, allowing the second drive shaft 6b to rotate counterclockwise.

[0045] The first rocker gear 4a meshes with the first rack 3a and the second rack 3b respectively, and the second rocker 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 the following: Figure 1 The first stroke stage shown, as Figure 2 The second stroke stage shown, as Figure 3 The third stroke stage shown and as Figure 4 The fourth stroke stage is shown.

[0047] like Figure 1As shown, 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, which is the power stroke, and pushes the fourth piston 2c to move to the left, which in turn pushes the second rack 3b of the second push rod to move to the left, and then drives the first rocker gear 4a and the second rocker gear 4b to rotate clockwise, which in turn drives the first rack 3a of the first push rod to move to the right; moreover, the first push rod drives the first piston 2a to move to the right, and the volume in the first cylinder 1a increases, so as to draw in gas (such as air) or intake air without high pressure assistance, which is the intake stroke; the first push rod pushes the second piston 2b to move to the right, compressing the gas in the second cylinder 1b, which is the compression stroke; the second push rod pushes the third piston 2d to move to the left, and discharges the exhaust gas in the third cylinder 2d, which is the exhaust stroke.

[0048] During the first stroke, cylinder 1a is in the intake stroke, cylinder 1b is in the compression stroke, cylinder 1c is in the power stroke, and cylinder 1d is in the exhaust stroke. When cylinder 1c performs its power stroke, piston 2c pushes rack 3b of push rod to the left, thereby driving first rocker gear 4a and second rocker gear 4b to rotate clockwise. First rocker gear 4a drives first drive shaft 6a to rotate clockwise and transmits power via one-way clutch 5a. Simultaneously, one-way clutch 5b is disengaged, and second rocker gear 4b rotates relative to second drive shaft 6b without forming a transmission connection; therefore, second drive shaft 6b rotates counterclockwise. In short, the power output by piston 2c is transmitted to first drive shaft 6a via first rocker gear 4a and one-way clutch 5a, driving first drive shaft 6a to rotate clockwise, while second drive shaft 6b rotates counterclockwise.

[0049] like Figure 2 As shown, 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, which is the power stroke, and pushes the second piston 2b to move to the left. The second piston 2b pushes the first rack 3a of the first push rod to move to the left, driving the first rocker gear 4a and the second rocker gear 4b to rotate counterclockwise, which in turn drives the second rack 3b of the second push rod to move to the right; moreover, the first push rod drives the first piston 2a to move to the left and compresses the gas in the first cylinder 2a, which is the compression stroke; the second push rod drives the fourth piston 2c to move to the right and discharges the exhaust gas in the fourth cylinder 2c, which is the exhaust stroke; the second rack 3b drives the third piston 2d to move to the right, the volume in the third cylinder 1d increases and gas is drawn in, which is the intake stroke.

[0050] During the second stroke, cylinder 1a is in the compression stroke, cylinder 1b is in the power stroke, cylinder 1c is in the exhaust stroke, and cylinder 1d is in the intake stroke. When cylinder 1b performs its power stroke, piston 2b pushes rack 3a of push rod to the left, thereby driving first rocker gear 4a and second rocker gear 4b to rotate counterclockwise. The second rocker gear 4b drives second drive shaft 6b to rotate counterclockwise and transmits power via one-way clutch 5b. Simultaneously, one-way clutch 5a is disengaged, and the first rocker gear 4a and first drive shaft 6a rotate relative to each other without forming a transmission connection. Therefore, first drive shaft 6a rotates clockwise without load. In short, the power output by piston 2b is transmitted to second drive shaft 6b via second rocker gear 4b and one-way clutch 5b, driving second drive shaft 6b to rotate counterclockwise, while first drive shaft 6a rotates clockwise without load.

[0051] like Figure 3 As shown, 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 to the right, pushing the first rack 3a of the first push rod to move to the right, which in turn drives the first rocker gear 4a and the second rocker gear 4b to rotate clockwise, which in turn drives the second rack 3b of the second push rod to move to the left; moreover, the first push rod drives the second piston 2b to move to the right, venting the exhaust gas in the second cylinder 1b, which is the exhaust stroke; the second push rod drives the fourth piston 2c to move to the left, increasing the volume in the fourth cylinder 1c and drawing in gas, which is the intake stroke; the second push rod drives the third piston 2d to move to the left, compressing the gas in the third cylinder 1d, which is the compression stroke.

[0052] In the third stroke, cylinder 1a is in the power stroke, cylinder 1b is in the exhaust stroke, cylinder 1c is in the intake stroke, and cylinder 1d is in the compression stroke. When cylinder 1a performs its power stroke, piston 2a pushes rack 3a of push rod to the right, thereby driving first rocker gear 4a and second rocker gear 4b to rotate clockwise. Rocker gear 4a drives first drive shaft 6a to rotate clockwise and transmits power via one-way clutch 5a. Simultaneously, one-way clutch 5b is disengaged, and second rocker gear 4b rotates relative to second output gear 8b without forming a transmission connection. Therefore, second drive shaft 6b rotates counterclockwise. In short, the power output by piston 2a is transmitted to first drive shaft 6a via first rocker gear 4a and one-way clutch 5a, driving first drive shaft 6a to rotate clockwise, while second drive shaft 6b rotates counterclockwise.

[0053] like Figure 4As shown, when the first piston 2a is in the exhaust stroke, the driving force of the fourth stroke stage comes from the third piston 2d of the third cylinder 1d, that is, the fuel in the third cylinder 1d burns and expands to do work, which is the power stroke, and 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 rocker gear 4a and the second rocker gear 4b to rotate counterclockwise, which in turn 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, venting the exhaust gas in the first cylinder 1a, which 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 drawing in gas, which 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, which is the compression stroke.

[0054] In the fourth stroke, cylinder 1a is in the exhaust stroke, cylinder 1b is in the intake stroke, cylinder 1c is in the compression stroke, and cylinder 1d is in the power stroke. When cylinder 1d performs its power stroke, piston 2d pushes rack 3b of push rod to the right, thereby driving first rocker gear 4a and second rocker gear 4b to rotate counterclockwise. Second rocker gear 4b drives second drive shaft 6b to rotate counterclockwise and transmits power through one-way clutch 5b. Simultaneously, one-way clutch 5a is disengaged, and first rocker gear 4a and first drive shaft 6a rotate relative to each other without forming a transmission connection. Therefore, first drive shaft 6a rotates clockwise without load. In short, the power output by piston 2d is transmitted to second drive shaft 6b through second rocker gear 4b and one-way clutch 5b, driving second drive shaft 6b to rotate counterclockwise, while first drive shaft 6a rotates clockwise without load.

[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 the cycle repeatedly; in each stroke, there is always one cylinder in intake, another cylinder in compression, a third cylinder in power, and a fourth cylinder in exhaust.

[0056] In addition, the power generated by the cylinders in the first and third strokes is output through the first drive shaft 6a, which rotates clockwise, while the second drive shaft 6b rotates counterclockwise.

[0057] The power generated by the cylinders in the second and fourth strokes is output through the second drive shaft 6b, which rotates counterclockwise, while the first drive shaft 6a rotates clockwise.

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

[0059] In one cycle of the four-stroke engine of this embodiment, the four-stroke engine of this embodiment has a 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 higher thermal efficiency (i.e., thermal efficiency not less than 60%). It can also improve the potential for SI-HCCI conversion through the variable compression ratio.

[0060] The four-stroke engine of this embodiment eliminates complex components such as pushrods, crankshafts, high-pressure oil bearings, and high-pressure oil pumps found in existing technologies. This not only reduces overall costs but also converts the linear reciprocating motion of the piston into rotary motion by using a pushrod with a rack to drive a corresponding rocker gear. This outputs rotational power to drive a rotary generator with stable power generation efficiency, thereby improving the conversion efficiency of mechanical energy into electrical energy. It also improves engine efficiency and can be used as a direct power source for driving HEV, PHEV, and REEV vehicles.

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

[0062] In this embodiment, the lever arm of the push rod force on the drive shaft is equal to the radius of the rocker gear. At the beginning of the power stroke, when the combustion energy in the cylinder is at its maximum, the energy can be quickly transferred out, reducing leakage and heat loss, thereby improving engine efficiency.

[0063] Furthermore, in this embodiment, the four cylinders work together in a coordinated manner to achieve a four-stroke cycle. Two pushrods are arranged in parallel, with a rocker gear positioned in the middle, meshing with racks to ensure motion coupling between the two racks via the rocker gear. Compared to existing two-stroke engines, this embodiment's four-stroke engine features both an exhaust stroke and an intake stroke to ensure high-quality exhaust and intake. The driving force generated by the power stroke drives the piston to expel exhaust gas, leaving minimal exhaust residue. In the next stroke, the piston movement creates negative pressure within the cylinder, drawing in air and improving scavenging efficiency. Additionally, fresh gas containing fuel is not short-circuited out, avoiding fuel loss and enabling a higher effective compression ratio, making it more suitable for the HCCI combustion cycle and improving efficiency. It also allows for the use of existing four-stroke engine components, reducing manufacturing costs.

[0064] Moreover, when the piston is around top dead center, its acceleration is significantly higher, thereby reducing the residence time at high temperatures and reducing heat transfer losses during combustion. When the piston is around bottom dead center, the lever arm of the push rod does not decrease, and the output power decays less, thus achieving small output power fluctuations.

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

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

[0067] like Figure 6 As shown, when the first rocker gear 4a and the second rocker gear 4b rotate clockwise, the first drive shaft 6a rotates clockwise, and the power is directly output through the output gear 8, so that the output gear 8 rotates clockwise and outputs torque. At the same time, the second drive shaft 6b rotates counterclockwise. When the first rocker gear 4a and the second rocker gear 4b rotate counterclockwise, the first drive shaft 6a rotates clockwise, the second drive shaft 6b rotates counterclockwise and transmits power, and drives the second coupling gear 7b to rotate counterclockwise, synchronously driving the first coupling gear 7a to rotate clockwise and transmit power. The first coupling gear 7a drives the output gear 8 to rotate clockwise and output power. In this way, the output gear 8 can continuously output power and torque and maintain clockwise rotation.

[0068] Example 2

[0069] Reference Figure 7As shown, Embodiment 2 provides a four-stroke free piston engine. Embodiment 2 and Embodiment 1 have largely the same structure, 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 rocker gear 4a is disposed between the two push rods and meshes with the racks of the two push rods respectively; the second rocker gear 4b is disposed 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 rocker gear 4a rotates clockwise, the second rocker gear 4b rotates counterclockwise. Conversely, the first one-way clutch 5a is configured such that when the first rocker gear 4a rotates clockwise, the first one-way clutch 5a locks and transmits power; when the first rocker gear 4a rotates counterclockwise, the first one-way clutch 5a disengages, allowing the first drive shaft 6a to rotate clockwise freely. The second one-way clutch 5b is configured such that when the second rocker gear 4b rotates clockwise, the second one-way clutch 5b locks and transmits power; when the second rocker gear 4b rotates counterclockwise, the second one-way clutch 5b disengages, allowing the second drive shaft 6b to rotate clockwise freely. Since both drive shafts rotate in the same direction, this arrangement shortens the cylinder shaft length.

[0070] In this specific embodiment, such as Figure 11 As shown, a first gear 9a and a second gear 9b are respectively provided on the two transmission shafts. The first gear 9a and the second gear 9b are both meshed with a coupling gear 10 to form a coupling mechanism that alternately transmits 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 in this embodiment is as follows, and includes the following: Figure 7 The first stroke stage shown, as Figure 8 The second stroke stage shown, as Figure 9 The third stroke stage shown and as Figure 10 The fourth stroke stage is shown.

[0072] like Figure 7As shown, 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, which is the power stroke, and pushes the fourth piston 2c to move to the left, which in turn pushes the single-sided rack 3b' of the second push rod to move to the left, then drives the first rocker gear 4a to rotate clockwise, which in turn drives the double-sided rack 3a' of the first push rod to move to the right, and then the double-sided rack 3a' drives the second rocker gear 4b to rotate counterclockwise; moreover, the first push rod drives the first piston 2a to move to the right, the volume in the first cylinder 1a increases, and gas is drawn in, which is the intake stroke; the first push rod pushes the second piston 2b to move to the right, compressing the gas in the second cylinder 1b, which is the compression stroke; the second push rod pushes the third piston 2d to move to the left, discharging the exhaust gas in the third cylinder 2d, which is the exhaust stroke.

[0073] During the first stroke, cylinder 1a is in the intake stroke, cylinder 1b is in the compression stroke, cylinder 1c is in the power stroke, and cylinder 1d is in the exhaust stroke. When cylinder 1c performs its power stroke, piston 2c pushes the single-sided rack 3b' of the second push rod to the left, thereby driving the first rocker gear 4a to rotate clockwise. The first rocker gear 4a drives the first drive shaft 6a to rotate clockwise and transmits power through a one-way clutch 5a. Simultaneously, the double-sided rack 3a' drives the second rocker gear 4b to rotate counterclockwise. The one-way clutch 5b is disengaged, and the second rocker gear 4b rotates relative to the second drive shaft 6b without forming a transmission connection. Therefore, the second drive shaft 6b rotates clockwise without load. In short, the power output by piston 2c is transmitted to the first drive shaft 6a through the first rocker gear 4a and the one-way clutch 5a, driving the first drive shaft 6a to rotate clockwise, while the second drive shaft 6b rotates clockwise without load.

[0074] like Figure 8 As shown, 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, which is the power stroke, and pushes the second piston 2b to move to the left. The second piston 2b pushes the double-sided rack 3a' of the first push rod to move to the left, driving the first rocker gear 4a to rotate counterclockwise. Simultaneously, the double-sided rack 3a' drives the second rocker gear 4b to rotate clockwise, and the first rocker gear 4a drives the single-sided rack 3b' of the second push rod to move to the right. Moreover, the first push rod drives the first piston 2a to move to the left and compresses the gas in the first cylinder 2a, which is the compression stroke. The second push rod drives the fourth piston 2c to move to the right and discharges the exhaust gas in the fourth cylinder 2c, which is the exhaust stroke. The single-sided rack 3b' drives the third piston 2d to move to the right, the volume in the third cylinder 1d increases, and gas is drawn in, which is the intake stroke.

[0075] During the second stroke, cylinder 1a is in the compression stroke, cylinder 1b is in the power stroke, cylinder 1c is in the exhaust stroke, and cylinder 1d is in the intake stroke. When cylinder 1b performs its power stroke, piston 2b pushes the double-sided rack 3a' of the first push rod to the left, thereby driving the first rocker gear 4a to rotate counterclockwise. The second rocker gear 4b drives the second drive shaft 6b to rotate counterclockwise and transmits power through a one-way clutch 5b. Simultaneously, the double-sided rack 3a' drives the first rocker gear 4a to rotate counterclockwise. With the one-way clutch 5a disengaged, the first rocker gear 4a and the first drive shaft 6a rotate relative to each other but do not form a transmission connection. Therefore, the first drive shaft 6a rotates clockwise without load. In short, the power output by piston 2b is transmitted to the second drive shaft 6b through the second rocker gear 4b and the one-way clutch 5b, driving the second drive shaft 6b to rotate clockwise, while the first drive shaft 6a rotates clockwise without load.

[0076] like Figure 9 As shown, 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 to the right, pushing the double-sided rack 3a' of the first push rod to move to the right, which in turn drives the first rocker gear 4a to rotate clockwise, which in turn drives the single-sided rack 3b' of the second push rod to move to the left. Then the double-sided rack 3a' drives the second rocker gear 4b to rotate counterclockwise; moreover, the first push rod drives the second piston 2b to move to the right, venting the exhaust gas in the second cylinder 1b, which is the exhaust stroke; the second push rod drives the fourth piston 2c to move to the left, increasing the volume in the fourth cylinder 1c and drawing in gas, which is the intake stroke; the second push rod drives the third piston 2d to move to the left, compressing the gas in the third cylinder 1d, which is the compression stroke.

[0077] In the third stroke, 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 performing power, the first piston 2a pushes the double-sided rack 3a' of the first push rod to the right, thereby driving the first rocker gear 4a to rotate clockwise. The first rocker gear 4a drives the first drive 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 rocker gear 4b to rotate counterclockwise. The one-way clutch 5b is in the disengaged state, and the second rocker gear 4b rotates relative to the second output gear 8b without forming a transmission connection. Therefore, the second drive shaft 6b rotates clockwise without load. In short, the power output by the first piston 2a is transmitted to the first drive shaft 6a through the first rocker gear 4a and the one-way clutch 5a, driving the first drive shaft 6a to rotate clockwise, while the second drive shaft 6b rotates clockwise without load.

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

[0079] During the fourth stroke, 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 is performing power, the third piston 2d pushes the single-sided rack 3b' of the second push rod to move to the right, thereby driving the first rocker gear 4a to rotate counterclockwise. The first push rod drives the second rocker gear 4b to rotate clockwise. The second rocker 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 rocker gear 4a to rotate counterclockwise. The one-way clutch 5a is in the disengaged state. The first rocker gear 4a and the first transmission shaft 6a rotate relative to each other but do not form a transmission connection. Therefore, the first transmission shaft 6a rotates clockwise without load. In short, the power output by the third piston 2d is transmitted to the second drive shaft 6b through the second rocker gear 4b and the one-way clutch 5b, driving the second drive shaft 6b to rotate clockwise, while the first drive shaft 6a rotates clockwise.

[0080] In summary, the first drive shaft 6a can maintain clockwise rotation and alternate between driving and idling, and the second drive shaft 6b can also maintain clockwise rotation and alternate between idling and driving. Thus, the first drive shaft 6a and the second drive shaft 6b alternate between driving and idling, ensuring that one drive shaft is always in operation during each stroke, and outputting power through either the first output gear 8a or the second output gear 8b, rotating clockwise. Of course, in other embodiments, it is also possible to... Figure 5 The two drive shafts shown are each equipped with an output gear for outputting torque.

[0081] like Figure 11As shown, when the first rocker gear 4a rotates clockwise and the second rocker gear 4b rotates counterclockwise, the first drive shaft 6a rotates clockwise, driving the first gear 9a to rotate clockwise and then driving the output gear 8 to rotate counterclockwise to output power. Simultaneously, the second drive shaft 6b rotates clockwise without load. When the first rocker gear 4a rotates counterclockwise and the second rocker gear 4b rotates clockwise, the first drive shaft 6a rotates clockwise without load, and the second drive shaft 6b rotates clockwise to transmit power, driving the second gear 9b to rotate clockwise and then driving the output gear 8 to rotate counterclockwise to output power. Simultaneously, the first drive shaft 6b rotates clockwise without load. This ensures that the output gear 8 continuously outputs power and torque while maintaining counterclockwise rotation.

[0082] Example 3

[0083] Example 3 provides a four-stroke free piston engine. The structure of Example 3 is generally the same as that of Example 1, except that: the two push rods are integrally connected and move synchronously in the same direction; the racks on the two push rods are set on the same side; the two rocker gears are both set on the rack side of the two push rods; and the rotation directions of the two drive shafts are set to be opposite to each other.

[0084] In this embodiment, two push rods are integrally connected to form a single push rod, and then connected one by one by two rack gears to form a new rack on the integral push rod. The new rack and the two rocker gears are arranged on the same side of the two push rods, and the two rocker gears mesh with the new rack. In this way, it can be achieved that the piston of one cylinder is always doing work, and simultaneously 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 rocker gears are wider to overcome the gap between the two racks, thereby ensuring that the two rocker gears mesh with the two racks one by one.

[0086] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A four-stroke free-piston engine, comprising two sets of cylinders, each set of cylinders including two oppositely arranged cylinders, characterized in that: It also includes transmission components; The transmission assembly includes two rocker gears, a one-way clutch and a drive shaft that cooperate with each rocker gear, and the rocker gears are configured to rotate on a fixed axis. The pistons of the two cylinders in each group are connected by a push rod. Each push rod is equipped with a rack. One rocker gear meshes with the racks of both push rods, and the other rocker gear meshes with at least one rack of a push rod. The rocker gear is connected to the corresponding drive shaft through the one-way clutch. Each cylinder sequentially completes the intake stroke, compression stroke, power stroke, and exhaust stroke, forming a cycle. There is always one cylinder whose piston is performing power, synchronously driving the other three cylinders to complete their respective intake, compression, and exhaust strokes. The locking directions of the two one-way clutches are set to be opposite to each other to ensure that one of the two drive shafts is outputting torque while the other is idling, and the idling direction of the drive 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 in one group generates a driving force during its power stroke to push its piston in a first direction; and through the transmission assembly, it drives the piston of another cylinder in the same group to move in the first direction to achieve the compression stroke, simultaneously driving the pistons of the third and fourth cylinders in another group to move in a second direction opposite to the first direction, so that the third and fourth cylinders in the other group complete the intake stroke and the exhaust stroke respectively; or it drives the piston of another cylinder in the same group to move in the first direction to achieve the exhaust stroke, simultaneously driving the pistons of the third and fourth cylinders in another group to move in a second direction opposite to the first direction, so that the third and fourth cylinders in the other group complete the intake stroke and the compression stroke respectively.

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 rocker gears are both arranged between the racks of the two push rods, and the two rocker gears mesh with the two racks one by one; the rotation directions of the two drive shafts are set to be opposite to each other.

4. The four-stroke free-piston engine according to claim 3, characterized in that: Each of the two drive shafts is equipped with an output gear 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 drive shafts to couple the power of the two drive shafts, ensuring that the output rotation direction remains unchanged and that the output rotational power is continuous and uninterrupted.

6. The four-stroke free-piston engine according to claim 1 or 2, characterized in that: One of the push rods has a single-sided rack, and the other push rod has a double-sided rack; one rocker gear is located between the two push rods and meshes with the racks of the two push rods respectively; another rocker gear is located on the side of the double-sided rack away from the single-sided rack and meshes with the double-sided rack; the two drive shafts rotate in the same direction.

7. The four-stroke free-piston engine according to claim 6, characterized in that: Each of the two drive shafts is equipped with an output gear 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 drive shafts to couple the power of the two drive shafts, ensuring that the output rotation direction remains unchanged and that the output rotational power is continuous and uninterrupted.

9. The four-stroke free piston engine according to claim 1, characterized in that: The two push rods are connected as a single unit and move synchronously in the same direction; the racks on the two push rods are set on the same side, and the two rocker gears are set on the rack side of the two push rods, with the two rocker gears meshing with the two racks one by one; the rotation directions of the two drive shafts are set 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 to one; or the gears of the two racks are independent of each other.

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