Continuously variable transmission

Abstract

A continuously variable transmission (CVT) is disclosed. By appropriately connecting and releasing the friction element C1 connecting the first rotating component M1 and the planetary gear carrier PC1, and the friction element B2 connecting the gearbox TC and the planetary gear carrier PC1, forward and reverse gear shifting is achieved. By appropriately connecting and releasing the friction element B3 connecting the gear ring R3 and the gearbox TC, the characteristics of free rotation and stationary position between the rotating planetary gear components are utilized to achieve the mutual conversion of power interruption and power transmission, and simultaneous gear shifting. This eliminates the need for traditional clutches, hydraulic couplings, and other components, solving the vibration and shifting shock problems associated with clutch power connections used in manual transmissions (MT) and the low transmission efficiency of hydraulic couplings used in automatic transmissions (AT). By introducing the output shaft speed as a function of gear shifting, this function possesses continuity and differentiability. In other words, using the starting speed of the drive wheels as a variable in the transmission allows for a smooth, efficient, and continuous reduction of the gear ratio while maintaining a low rotational speed of the drive source. This solves the problems of limited gear ratio range in CVT transmissions, high energy consumption during high-speed cruising, and weak overtaking ability when relying on the high speed of the drive source. It also addresses the issues of low starting torque and high energy consumption during high-speed cruising in household electric vehicles due to manufacturing costs and back electromotive force. The all-gear connection solves the problem of chain slippage during high-torque starts in CVT transmissions and addresses the power loss caused by shift jerks in stepped transmissions.

Description

Technical Field

[0001] This invention relates to continuously variable transmissions (CVTs) suitable for (including but not limited to) wheel-to-wheel transmissions in vehicles. Background Technology

[0002] This invention can be used as an inter-wheel transmission device, and the invention will be described below through the lens of a vehicle transmission (hereinafter referred to as a transmission).

[0003] A transmission is used to regulate the speed and torque output of a drive source (such as an engine or electric motor) to adapt to different driving conditions. By changing the gear ratio, a transmission can enable functions such as forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation.

[0004] The following are the main problems, representative types, and causes of current mainstream transmissions: The reasons can be summarized in the following three aspects. First, the initial acceleration phase: a) The clutch used in a manual transmission (MT) completely disconnects from the engine power during engagement and disengagement, resulting in vibration during power transmission. b) The hydraulic coupling in an automatic transmission (AT) has low transmission efficiency and high drive source energy consumption. c) CVT transmissions suffer from low efficiency during high-torque acceleration due to chain slippage. d) The starting torque of electric motors in domestic electric vehicles is low due to manufacturing costs.

[0005] Secondly, during acceleration: the shift shocks in stepped transmissions such as MT and AT reduce transmission efficiency due to power loss. Furthermore, DCT transmissions exhibit noticeable shift shocks at low speeds.

[0006] Thirdly, during constant speed driving: CVT transmissions have a limited gear ratio range, and when high-speed cruising relies on the drive source to maintain high RPMs, energy consumption is high and overtaking is weak. Electric vehicle motors also experience high energy consumption during high-speed cruising due to back electromotive force. Summary of the Invention

[0007] This invention addresses the aforementioned problems by providing a continuously variable transmission (CVT) that utilizes three planetary gears and three friction elements to achieve functions such as forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation. Furthermore, by introducing the output shaft speed as a transmission shift function, this function possesses continuity and differentiability. In other words, using the starting speed of the drive wheels as the shift variable allows for efficient, smooth, and continuous reduction of the transmission ratio, while maintaining a low rotational speed of the drive source to preserve power reserves and reduce fuel and electricity consumption. The invention leverages the idle and stationary characteristics of the planetary gear rotating elements to achieve the mutual conversion between power interruption and power transmission, eliminating the need for traditional clutches, hydraulic couplings, and other components. The all-gear transmission can withstand higher torque and offers strong adaptability.

[0008] To achieve the aforementioned objective, the present invention provides a continuously variable transmission (CVT), comprising: a first planetary gear consisting of a first sun gear, a first ring gear, and a first planetary gear frame supporting a first pinion meshing with the first sun gear and the first ring gear; a second planetary gear consisting of a second sun gear, a second ring gear, and a second planetary gear frame supporting a second pinion meshing with the second sun gear and the second ring gear; a third planetary gear consisting of a third sun gear, a third ring gear, and a third planetary gear frame supporting a third pinion meshing with the third sun gear and the third ring gear; and three friction elements, which, by appropriately connecting and releasing the three friction elements, realize functions such as forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation, and can output torque from the input shaft to the output shaft. The feature is that the second sun gear is constantly connected to the first ring gear to form a first rotating component, the output shaft is constantly connected to the third planetary gear carrier and the second ring gear, the third sun gear is constantly connected to the second planetary gear carrier, the first sun gear is constantly connected to the input shaft, and the three friction elements are composed of the following friction elements: a first friction element that selectively connects the first planetary gear carrier and the first rotating component; a second friction element that selectively connects the first planetary gear carrier and the gearbox; and a third friction element that selectively connects the third ring gear and the gearbox. By combining two of the three friction elements simultaneously, functions such as forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation are achieved.

[0009] Therefore, in the continuously variable transmission (CVT) of this invention, by simultaneously connecting two of the three friction elements, functions such as forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation are achieved. Thus, when the transmission ratio is large, the drive wheel begins to rotate. As the vehicle's inertial force increases, the drive wheel speed continuously increases. Constrained by the drive wheel speed, the transmission ratio decreases smoothly and continuously, maintaining the drive source speed within its efficient operating range to reduce fuel and electricity consumption. This solves the problems of limited transmission ratio range in CVT transmissions, high energy consumption and weak overtaking ability when relying on high drive source speed for high-speed cruising; it also solves the problems of low starting torque and high power consumption during high-speed cruising in household electric vehicles due to manufacturing costs and back electromotive force. Utilizing the characteristics of idling and stationary rotation between planetary gear rotating elements, the mutual conversion between power interruption and power transmission is achieved, eliminating the need for traditional clutches and hydraulic couplings. This solves the vibration and shift shock problems associated with clutch power connections in MT transmissions; and it solves the low transmission efficiency problem of hydraulic couplings used in AT transmissions. The all-gear connection solves the problem of chain slippage during high-torque start-up in CVT transmissions; it also solves the power loss problem caused by shift jerking in stepped transmissions. It is durable, easy to operate, can withstand higher torque, is highly adaptable and suitable for high-performance or aggressive driving, and offers a high level of driving pleasure. Attached Figure Description

[0010] Figure 1 is a schematic diagram of a continuously variable transmission (CVT); Figure 2 is a diagram illustrating the shifting action of the forward gear of a continuously variable transmission (CVT). Figure 3 is a diagram illustrating the reverse gear function of a continuously variable transmission (CVT). Symbol Explanation PG1 First Planetary Gear S1 First Sun Gear PC1 First Planetary Gear Carrier R1 First gear ring PG2 Second Planetary Gear S2 Second Sun Gear PC2 Second Planetary Gear Carrier R2 Second Gear Ring PG3 Third Planetary Gear S3 Third Sun Gear PC3 Third Planetary Gear Carrier R3 Third Gear Ring IN input axis OUT output axis M1 First Rotating Component C1 First clutch (first friction element) B2 Second Brake (Second Friction Element) B3 Third Brake (Third Friction Element) TC transmission Detailed Implementation

[0011] The following description, based on the accompanying drawings, illustrates a continuously variable transmission (CVT) for implementing the present invention.

[0012] First, let's explain the composition.

[0013] Figure 1 This is a schematic diagram representing a continuously variable transmission (CVT). Below, based on... Figure 1 The planetary gear configuration and friction element configuration of a continuously variable transmission (CVT) are explained.

[0014] like Figure 1 As shown, the continuously variable transmission includes: a first planetary gear PG1, a second planetary gear PG2, a third planetary gear PG3, an input shaft IN, an output shaft OUT, a first rotating component M1, a first clutch C1 (first friction element), a second brake B2 (second friction element), a third brake B3 (third friction element), and a gearbox TC.

[0015] The aforementioned first planetary gear PG1 is composed of a first sun gear S1, a first planetary gear carrier PC1 that supports and meshes with the first pinion P1, and a first gear ring R1 that meshes with the first pinion P1.

[0016] The aforementioned second planetary gear PG2 is composed of a second sun gear S2, a second planetary gear carrier PC2 supporting and meshing with the second pinion P2, and a second gear ring R2 meshing with the aforementioned second pinion P2.

[0017] The aforementioned third planetary gear PG3 is composed of a third sun gear S3, a third planetary gear carrier PC3 supporting a third pinion P3 that meshes with the third sun gear S3, and a third gear ring R3 that meshes with the aforementioned third pinion P3.

[0018] The aforementioned input shaft IN is a shaft that receives the rotational drive torque from a drive source (such as an engine or electric motor) and is usually connected to the aforementioned first sun gear S1.

[0019] The aforementioned output shaft OUT is the shaft that outputs the drive torque after speed change via the transmission shaft and the end transmission gear, and is usually connected to the aforementioned third planetary gear carrier PC3 and the aforementioned second gear ring R2.

[0020] The first rotating member M1 is a rotating member that connects the first gear ring R1 and the second sun gear S2 without passing through a friction element.

[0021] The first clutch C1 is a first friction element that selectively connects the first planetary gear carrier PC1 and the first rotating member M1.

[0022] The aforementioned second brake B2 is a second friction element that selectively connects the aforementioned first planetary gear carrier PC1 and the aforementioned gearbox TC.

[0023] The aforementioned third brake B3 is a third friction element that selectively connects the aforementioned third gear ring R3 and the aforementioned gearbox TC.

[0024] like Figure 1 As shown, the first planetary gear PG1, the second planetary gear PG2, and the third planetary gear PG3 are arranged sequentially from the input shaft IN connected to the drive source toward the output shaft OUT.

[0025] The following section explains the transmission mechanism of a continuously variable transmission (CVT).

[0026] The continuously variable transmission (CVT) achieves forward movement, acceleration, constant speed driving, power interruption, and neutral operation through a combination of two simultaneously connected of three friction elements C1, B2, and B3. When the frictionless element is engaged, it operates in neutral. When the first clutch C1 is engaged, the power is interrupted. When the third brake B3 is engaged, it moves forward and accelerates simultaneously. When the third brake B3 is released appropriately, it achieves constant speed driving.

[0027] Reverse movement is achieved by simultaneously connecting two of the three friction elements C1, B2, and B3, and by simultaneously connecting the second brake B2 and the third brake B3.

[0028] Next, the function will be explained.

[0029] The function of the continuously variable transmission (CVT) is explained in terms of "speed change function in forward and reverse gears" and "advantages shown in comparison with existing technologies".

[0030] (The effect of shifting between forward and reverse gears) (Forward) In forward gear, such as Figure 2 As shown in the cross-section, the first clutch C1 and the third brake B3 are simultaneously engaged.

[0031] When no friction elements are engaged, the gear is in neutral. Through the engagement of the first clutch C1, the two rotating elements of the first planetary gear PG1—the first planetary gear carrier PC1 and the first ring gear R1—and the first rotating component M1 formed with the second sun gear S2 are directly connected. Because the input shaft IN is directly connected to the first sun gear S1, the three rotating elements S1, PC1, and R1 of the first planetary gear PG1, along with the input shaft IN and the second sun gear S2, rotate as a single unit. The second planetary gear carrier PC2 and the third sun gear S3 are directly connected, and the third ring gear R3 idles, resulting in a power interruption state. Through the engagement of the third brake B3 controlled by the accelerator pedal, the third ring gear R3 and the gearbox TC are directly connected and fixed. Furthermore, the second ring gear R2 and the third planetary gear carrier PC3 are directly connected to the output shaft OUT. This is the acceleration state.

[0032] Therefore, if the input speed is input to the first sun gear S1 via the input shaft IN, then to the second sun gear S2, and finally to the third sun gear S3 via the second planetary gear carrier PC2, the third planetary gear carrier PC3 of the third planetary gear PG3 will rotate simultaneously under the constraint of the reduced speed to a fixed third ring gear R3. The constraint condition at this time is that, via the first clutch C1 and the first rotating member M1, the three rotating elements S1, PC1, and R1 of the second sun gear S2 and the first planetary gear PG1, and the input shaft IN, are kept at the same speed, and the speeds of the second planetary gear carrier PC2 and the third sun gear S3 are also kept at the same speed. According to this rotational constraint relationship, the speed of the third planetary gear carrier PC3 becomes the speed after the input speed is reduced. The output speed (=reduction speed lower than input speed) from the third planetary gear carrier PC3 is transmitted to the output shaft OUT, while simultaneously being transmitted in the reverse direction to the second ring gear R2. This causes the second ring gear R2, the third planetary gear carrier PC3, and the output shaft OUT to simultaneously change from fixed to rotating. Therefore, in the second planetary gear PG2 with 2 inputs and 1 output, by specifying the speed of the second sun gear S2 (=input speed) and the linear acceleration speed of the second ring gear R2, the second planetary gear carrier PC2 and the third sun gear S3 are determined to continuously increase in speed, and the third planetary gear carrier PC3 is determined to maintain the transmission of linear acceleration speed to the output shaft OUT, thus achieving stepless speed increase in forward gears.

[0033] (Rewind) In reverse gear, such as Figure 3 As shown in the cross-section, the second brake B2 and the third brake B3 are connected simultaneously.

[0034] Through the connection of the second brake B2, the first planetary gear carrier PC1 and the gearbox TC are directly connected and fixed. Because the input shaft IN and the first sun gear S1 are directly connected, the two rotating elements of the first planetary gear PG1, the first sun gear S1 and the first ring gear R1, rotate in opposite directions. Through the connection of the third brake B3, controlled by the accelerator pedal, the third ring gear R3 and the gearbox TC are directly connected and fixed. Furthermore, the first ring gear R1 and the second sun gear S2 are directly connected, the second planetary gear carrier PC2 and the third sun gear S3 are directly connected, and the second ring gear R2, the third planetary gear carrier PC3, and the output shaft OUT are directly connected.

[0035] Therefore, if the input rotational speed passes through the input shaft IN and the first sun gear S1, and is output from the first planetary gear PG1 of the fixed first planetary gear carrier PC1 in the opposite direction to the input rotational direction from the first ring gear R1, and then passes through the second sun gear S2 and the second planetary gear carrier PC2 to the third sun gear S3, then the third planetary gear carrier PC3 of the third planetary gear PG3 is constrained by the fixed third ring gear R3 and rotates simultaneously. The constraint condition at this time is that, via the second brake B2 and the first rotating member M1, the rotational speeds of the second sun gear S2 and the first sun gear S1 of the second planetary gear PG2 are reduced in opposite directions, and the rotational speeds of the second planetary gear carrier PC2 and the third sun gear S3 are the same. According to this rotational constraint relationship, the rotational speed of the third planetary gear carrier PC3 becomes the speed after reducing the input rotational speed. The output speed (= input speed refers to the speed slightly lower than the input speed in the reverse direction) from the third planetary gear carrier PC3 is transmitted to the output shaft OUT, while the second ring gear R2 is transmitted in the opposite direction. This constrains the second planetary gear carrier PC2 and the third sun gear S3 to continuously increase speed, thus determining that the third planetary gear carrier PC3 maintains the transmission of linear acceleration speed to the output shaft OUT, achieving stepless speed increase in downshifting.

[0036] (Advantages shown in comparison with existing technologies) The advantages of the continuously variable transmission (CVT) shown below, compared with existing technologies, will be explained.

[0037] First, comparing the continuously variable transmission (CVT) with existing technologies, in the following points: 1. Transmission efficiency 2. Energy consumption of the driving source 3. Power performance during rapid acceleration 4. Smooth shifting 5. Structural complexity and maintenance costs 6. Smooth power transmission.

[0038] This section explains the advantages of continuously variable transmissions (CVTs) compared to existing transmission technologies.

[0039] The reasons can be summarized in the following three aspects. First, the initial stage: a) The clutch used in a manual transmission (MT) completely disconnects the power connection between the engine and the transmission, inevitably leading to severe clutch plate wear or shift shock during the connection process. b) The hydraulic coupling in an automatic transmission (AT) essentially utilizes the principle that "no shear force is generated within a stationary fluid" to cut off power transmission. The so-called flexible power transmission can be understood as simply slippage, resulting in low transmission efficiency and high drive source energy consumption. This is because solids are more efficient at transmitting force than fluids. c) In a CVT, the chain will slip once the starting torque exceeds a certain threshold, resulting in low efficiency during rapid acceleration. The meshing force of gears is more efficient than frictional transmission. d) Due to manufacturing costs, the starting torque of electric motors in domestic electric vehicles is low, requiring adjustment by the transmission. This invention relates to a continuously variable transmission (CVT) that utilizes the characteristics of freewheeling and stationary rotation between planetary gears to achieve the disconnection and connection of driving force transmission. It eliminates the need for traditional clutches, hydraulic couplings, and other components. The all-gear connection eliminates power fluctuations, resulting in high transmission efficiency, low friction loss, low energy consumption of the drive source, high starting torque, high speed and torque conversion efficiency, smooth power transmission, excellent performance during rapid acceleration, and the ability to drive aggressively. It also features a simple structure, high durability and reliability, and helps reduce costs.

[0040] Secondly, regarding the acceleration phase: stepped, fixed-ratio transmissions such as manual transmissions (MT) and automatic transmissions (AT) inevitably suffer from severe clutch wear or shift jerking, leading to power loss. Furthermore, dual-clutch transmissions (DCTs) exhibit noticeable jerking at low speeds. Continuously variable transmissions (CVTs), on the other hand, offer smooth power transmission and high efficiency. This invention's continuously variable transmission (CVT) can maintain a constant drive source speed while accelerating, further reducing energy consumption and reserving the drive source's rapid acceleration capability.

[0041] Thirdly, during the constant-speed driving phase: Due to the limited transmission ratio range of the CVT transmission, and the fact that domestic electric vehicles can only maintain speed by relying on the high speed of the drive source itself during high-speed cruising, the efficiency of rapid acceleration during overtaking is low, overtaking is sluggish, and the energy consumption of the drive source is high. The electric vehicle motor also consumes a lot of electricity during high-speed cruising due to the back electromotive force. The transmission ratio of the continuously variable transmission of this invention theoretically tends to be infinitely small as the vehicle speed increases, which can keep the drive source always in a highly efficient operating range, resulting in low energy consumption, sufficient power reserves, and high efficiency for rapid acceleration and overtaking at high speeds.

[0042] Next, the effects will be explained.

[0043] The following effects can be achieved in a continuously variable transmission (CVT).

[0044] (1) A continuously variable transmission (CVT) comprising: a first planetary gear PG1, which is composed of a first sun gear S1, a first ring gear R1, and a first planetary gear carrier PC1 supporting a first pinion P1 meshing with the first sun gear S1 and the first ring gear R1; a second planetary gear PG2, which is composed of a second sun gear S2, a second ring gear R2, and a second planetary gear carrier PC2 supporting a second pinion P2 meshing with the second sun gear S2 and the second ring gear R2; and a third planetary gear PG3, which is composed of a third sun gear S3, a third ring gear R3, and a third planetary gear carrier PC2 supporting a third sun gear S3 and the third ring gear R3 meshing with the third sun gear S3 and the third ring gear R3. The pinion P3 is composed of a third planetary gear carrier PC3; three friction elements are used to achieve forward movement, acceleration, constant speed driving, reverse movement, power interruption and neutral operation by properly connecting and releasing the three friction elements. The torque from the input shaft IN can be output to the output shaft OUT. The configuration is as follows: the second sun gear S2 is constantly connected to the first ring gear R1 to form a first rotating member M1; the output shaft OUT is constantly connected to the third planetary gear carrier PC3 and the second ring gear R2; the third sun gear S3 and the second planetary gear carrier PC2 are constantly connected; and the first sun gear S1 is constantly connected to the input shaft IN. The three friction elements described above are composed of the following friction elements: a first friction element (first clutch C1), which selectively connects the first planetary gear carrier PC1 and the first rotating member M1; a second friction element (second brake B2), which selectively connects the first planetary gear carrier PC1 and the gearbox TC; and a third friction element (third brake B3), which selectively connects the third gear ring R3 and the gearbox TC. By appropriately connecting and releasing the three friction elements, forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation are achieved.

[0045] Therefore, by introducing the output shaft speed as the transmission's shift function, this function possesses continuity and differentiability. In other words, using the drive wheel's starting speed as the shift variable allows for efficient, smooth, continuous, and uninterrupted reduction of the transmission ratio, while maintaining a low rotational speed of the drive source.

[0046] (2) Forward movement, acceleration, constant speed driving, power interruption, and neutral operation are achieved by simultaneously connecting two of the above three friction elements. When the vehicle is started, there are no friction elements connected. The rotational driving torque of the drive source is transmitted to the first sun gear S1 via the input shaft IN. The drive torque keeps the first row gear carrier PC1, which has the least rotational resistance, idling, which is the neutral gear operation.

[0047] When the gear shift lever is engaged in forward gear, it connects to the first friction element (first clutch C1). The two rotating elements of the first planetary gear PG1—the first planetary gear carrier PC1 and the first ring gear R1—and the first rotating component M1, which is formed with the second sun gear S2, are directly connected. Because the input shaft IN and the first sun gear S1 are directly connected, the three rotating elements S1, PC1, and R1 of the first planetary gear PG1, along with the input shaft IN and the second sun gear S2, rotate as a single unit. Constrained by the vehicle's static inertia, the second ring gear R2, which is normally connected to the output shaft OUT and the third planetary gear carrier PC3, remains fixed. The second planetary gear carrier PC2 and the third sun gear S3 are directly connected. At this time, the driving torque maintains the third ring gear R3, which experiences the least rotational resistance, rotating in reverse, resulting in a power interruption.

[0048] When the accelerator pedal is lightly pressed, the third friction element (third brake B3) is engaged. Assume the rotational relationship of the three rotating elements S3, PC3, and R3 of the third planetary gear PG3 is: S3 rotates at 100 rpm, PC3 at 30 rpm, and R3 at 20 rpm. The third ring gear R3 is connected to the gearbox TC. At this time, the driving force of the gear meshing with the maximum acceleration and minimum relative friction loss is transmitted to the third planetary gear carrier PC3. Because the rotational speed of the third ring gear R3 decelerates linearly from 20 rpm to 0 rpm, the third planetary gear carrier PC3, constrained by it and the third sun gear S3, must exhibit a mirror-symmetrical linear acceleration from 0 rpm to 30 rpm. The third planetary gear carrier PC3 is constantly connected to the output shaft OUT. At this time, the vehicle is in an idle start-up state. The process of the drive wheel speed from 0 to 1 rpm is differentiable, with no power fluctuations, smooth power transmission, high transmission efficiency, and low energy consumption of the drive source, achieving forward movement.

[0049] The second ring gear R2 is constantly connected to the third planetary gear carrier PC3 and the output shaft OUT. The second ring gear R2, constrained by the third planetary gear carrier PC3, undergoes linear acceleration rotation from a fixed state to the vehicle's starting drive wheel. In the second planetary gear PG2, the second sun gear S2 rotates at its idle speed from the drive source. At this time, the rotational speed of the second planetary gear carrier PC2, constrained by the second sun gear S2 and the second ring gear R2, becomes a linearly accelerated speed resulting from the superposition of the rotational speeds of the second sun gear S2 and the second ring gear R2, and is transmitted to the third sun gear S3. In the third planetary gear PG3, the third ring gear R3 remains fixed. The rotational speed of the third planetary gear carrier PC3, constrained by the third sun gear S3 and the third ring gear R3, maintains linear acceleration and is simultaneously transmitted to the output shaft OUT and the second ring gear R2, repeating this cycle. Therefore, when the transmission ratio is high, the drive wheels begin to rotate. As the vehicle's inertia increases, the drive wheel speed continuously rises. Constrained by the drive wheel speed, the transmission ratio efficiently, smoothly, and continuously decreases, maintaining the drive source speed at a low rotational speed to preserve power reserves and reduce energy consumption. This allows for acceleration while keeping the drive source speed constant. Pressing the accelerator pedal deeply increases the drive source speed to its maximum torque speed, releasing the drive source power reserves. Combined with the linear acceleration speed of the continuously variable transmission (CVT), this allows for high-performance or spirited driving, providing a strong driving pleasure.

[0050] During high-speed cruising, appropriately releasing the connection to the third friction element (third brake B3) keeps the third gear ring R3 at a constant speed of 0 or low speed, achieving constant speed driving. By introducing the output shaft OUT speed as the transmission shift function, this function is continuous. In other words, using the drive wheel speed as the shift variable allows for efficient, smooth, and continuous reduction of the transmission ratio, keeping the drive source speed within its efficient operating range to reduce energy consumption. When accelerating rapidly to overtake at high speed, pressing the accelerator pedal deeply releases the drive source's reserve power, which, combined with the linear acceleration speed of the continuously variable transmission, easily enables high-speed overtaking.

[0051] (3) The backward movement achieved by the combination of two of the above three friction elements being connected simultaneously is achieved by the simultaneous connection of the above second friction element (second brake B2) and the above third friction element (third brake B3).

[0052] When the shift lever is engaged in reverse, the second brake B2 is connected. The input speed passes through the input shaft IN and the first sun gear S1, and is transmitted from the first planetary gear PG1 (which is fixed to the first planetary gear carrier PC1) to the second sun gear S2, the second planetary gear carrier PC2, and the third sun gear S3 via the first ring gear R1, which outputs a rotation in the opposite direction to the input speed. Lightly pressing the accelerator pedal engages the third friction element (third brake B3), which transmits the input speed (which is the speed in the opposite direction) to the third planetary gear carrier PC3, the second ring gear R2, and the output shaft OUT, achieving acceleration while reversing.

[0053] Therefore, by using three planetary gears and three friction elements, while achieving forward movement, acceleration, constant speed driving, reverse movement, power interruption, and neutral operation, the efficiency of drive energy transmission can be improved by suppressing frictional losses generated during power transmission. It can output driving force according to vehicle conditions and reduce energy consumption. Furthermore, it can suppress shift shock. Additionally, it can be set to achieve both the required starting performance at the maximum gear ratio and the high-speed energy consumption rate at the minimum gear ratio, thus meeting the shifting requirements in heavy-duty vehicles and passenger vehicles. Moreover, the structure is relatively simple, which is advantageous in terms of durability, reliability, cost, and unit layout.

[0054] The continuously variable transmission (CVT) of the present invention has been described above. However, for specific configurations, design changes and additions are permitted as long as they do not depart from the spirit and scope of the present invention.

[0055] The continuously variable transmission of the present invention is in Figure 1 The schematic diagram shows an example of a continuously variable transmission (CVT) for a front-wheel-drive (FR) engine vehicle with a coaxial input / output shaft configuration. However, it is not limited to FR engine vehicles and can also be used in various vehicles such as front-wheel-drive (FF) engine vehicles, hybrid vehicles, electric vehicles, and fuel cell vehicles. Additionally, it can be used in vehicles powered by low-torque diesel engines. Furthermore, it can be used as a CVT for inter-wheel transmission devices such as wind power generators.

Claims

1. A continuously variable transmission, comprising: a first planetary gear comprising a first sun gear, a first ring gear, and a first planetary carrier supporting a first pinion gear engaged with the first sun gear and the first ring gear; a second planetary gear comprising a second sun gear, a second ring gear, and a second planetary carrier supporting a second pinion gear engaged with the second sun gear and the second ring gear; a third planetary gear comprising a third sun gear, a third ring gear, and a third planetary carrier supporting a third pinion gear engaged with the third sun gear and the third ring gear; three friction elements; and a transmission housing, wherein torque from an input shaft is output to an output shaft by selectively engaging the three friction elements to achieve forward, acceleration, constant speed, reverse, power interruption, and neutral operation, and wherein the second sun gear is permanently connected to the first ring gear to form a first rotational member, the output shaft is permanently connected to the third planetary carrier and the second ring gear, the third sun gear is permanently connected to the second planetary carrier, the first sun gear is permanently connected to the input shaft, the three friction elements comprise a first friction element selectively connecting the first planetary carrier to the first rotational member, a second friction element selectively connecting the first planetary carrier to the transmission housing, and a third friction element selectively connecting the third ring gear to the transmission housing, and wherein combinations of simultaneous engagement of two of the three friction elements achieve forward, acceleration, constant speed, reverse, power interruption, and neutral operation.

2. The continuously variable transmission of claim 1, wherein combinations of simultaneous engagement of two of the three friction elements achieve forward, acceleration, constant speed, power interruption, and neutral operation, and wherein neutral operation is achieved with no friction elements engaged, power interruption is achieved with the first friction element engaged, forward and simultaneous acceleration is achieved with the third friction element engaged, and constant speed is achieved by selectively disengaging the third friction element.

3. The continuously variable transmission of claim 1 or 2, wherein reverse operation is achieved by simultaneous engagement of the second friction element and the third friction element. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images