Pressure control system for clutch and transmission

Abstract

The utility model provides a system for a transmission clutch, and relates to a pressure control system for the clutch and a transmission. In one example, a clutch has a pressure control system that includes a piston housing that encloses a piston chamber and a piston, and a diffuser located in the piston chamber. The diffuser may have a tangential passage for directing fluid flow into the piston cavity.

Description

Technical Field

[0001] This description generally relates to methods and systems for vehicle transmissions. Background Art

[0002] The powertrain of a vehicle may include a transmission that relies on the opening and closing of a clutch to effect gear shifts between drive gears or gear sets. To shift gears smoothly between different gears, e.g., without sudden changes in torque output, precise control of the clutch pressure may be required. For example, in the case of a wet clutch, the inflow of hydraulic fluid into the cavity of a wet clutch piston may exert non-uniform hydraulic pressure on the piston during wet clutch engagement. The non-uniform pressure may cause the piston to tilt while moving towards the clutch pack of the wet clutch.

[0003] The tilting of the piston may cause the initial contact point of the piston with the clutch pack to become dispersed over time. For example, when the piston is aligned parallel to the surface of the clutch pack, the initial single contact point between the piston and the surface of the clutch pack may remain constant, enabling torque to be transmitted to the wet clutch in a uniform and constant manner. When the piston is not parallel to the surface of the clutch pack, the piston may initially contact the surface of the clutch pack at one point, but as the hydraulic pressure in the cavity increases, the alignment of the piston changes until the piston is parallel to the surface of the clutch pack. During the period when the piston is parallelly aligned, the torque transmission through the wet clutch may be uncontrolled, which may result in shocks and / or torque oscillations in the vehicle driveline. The gear shift may be jerky, making the vehicle's driver and passengers uncomfortable. Summary of the Utility Model

[0004] In one example, the above problem can be solved by a pressure control system for the clutch. The pressure control system may include a piston housing that encloses a piston cavity and a piston, and a diffuser located within the piston cavity. The diffuser may have tangential channels for guiding fluid into the piston cavity. In this way, the gear shift actuated by the clutch will be smooth without shocks or torque oscillations.

[0005] For example, the tangential channels of the diffuser may slow down the fluid flowing into the cavity without transferring momentum to the piston. The impact of the inflowing fluid on the piston along the axial direction is thus reduced. In addition, the volume of the piston cavity in combination with the return force exerted by at least one return spring may keep the piston aligned perpendicular to the axis, so that the piston contacts the clutch pack of the clutch at a single contact point.

[0006] It should be understood that the above summary is provided to introduce in a simplified form concepts that are further described in the detailed description. It is not intended to identify the key or essential features of the claimed subject matter, the scope of which is uniquely determined by the claims that follow the detailed description. Additionally, the claimed subject matter is not limited to embodiments that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram showing an example vehicle powertrain system that may include a pressure control system for regulating clutch pressure.

[0008] Figure 2 A cross-sectional view of a clutch equipped with a pressure control system.

[0009] Figure 3 Shows Figure 2 A first view of a clutch diffuser.

[0010] Figure 4 Shows Figure 3 A second view of the diffuser.

[0011] Figure 5 Shows Figure 3 A third view of the middle diffuser.

[0012] Figure 6 Shows an example of a transmission shifting method, where the transmission has at least one clutch with a pressure control system. DETAILED DESCRIPTION

[0013] The following description relates to systems and methods for wet clutches. Wet clutches may be included in vehicle powertrain components, examples of which are shown Figure 1 to facilitate, for example, the engagement and disengagement of gears or gear sets and brakes in a vehicle transmission. For example, the vehicle transmission may be an automatic transmission that shifts gears by opening and closing the wet clutch. The opening and closing of the wet clutch can be achieved by a hydraulic change in the wet clutch, which can force the piston of the wet clutch to move. As Figure 2 shown, by configuring a pressure control system on the wet clutch, the movement of the piston can be made consistent with the axis. The pressure control system includes a piston chamber having a target volume and a diffuser that controls the inflow of hydraulic fluid into the piston chamber. Different views of the diffuser are shown as Figures 3 - 5 shown. Figure 6 Shows a method for implementing a shift on a transmission that is configured with a clutch having a pressure control system as described herein.

[0014] First, look at Figure 1, the vehicle 100 shown in the figure has a power system 101 and a transmission system 103. The power assembly includes a prime mover 106 and a transmission 108. The prime mover 106 can be, for example, an internal combustion engine and / or an electric motor, and its working principle is to provide rotational power to the transmission 108. The transmission 108 can be any type of transmission, such as a manual transmission, an automatic transmission, or a continuously variable transmission. The transmission 108 receives the rotational power generated by the prime mover 106 as input and outputs rotational power to the transmission system 103 according to the selected gear or setting.

[0015] In one example, the transmission 108 can be an automatic transmission, which includes more than one clutch for engaging and disengaging the gears and brakes of the automatic transmission. In Figure 1 it, more than one clutch can be generally represented as clutch 130, where the clutch 130 can rely on the translation of the piston according to the change of hydraulic pressure and can be arranged in the transmission 108 to achieve gear shifting. It can be understood that Figure 1 the clutch 130 in it is only a general description of the location where the clutch 130 is located and does not represent the actual location in the transmission 108. In addition, as described above, there may be more than one clutch 130 in the transmission 108. Other details of the clutch 130 and the clutch 130 pressure control system will be further introduced below. In addition, the dual-clutch automatic transmission described above is a non-limiting example of a clutch environment in which the pressure control system can be implemented. Similarly, the pressure control system can also be applied to various types of wet clutches, such as brakes for example.

[0016] The prime mover 106 can be powered by energy from an energy storage device 105. In one example, the energy storage device 105 is a battery for storing electrical energy. An inverter 107 can be installed between the energy storage device 105 and the prime mover 106 to adjust direct current (DC) to alternating current (AC).

[0017] The vehicle 100 can be a commercial vehicle, a light, medium or heavy vehicle, a passenger vehicle, an off-road vehicle or a multi-purpose vehicle. In addition, the vehicle 100 and / or one or more of its components can also be used in industrial, locomotive, military, agricultural and aerospace fields. In one example, the vehicle 100 is an electric vehicle.

[0018] In certain examples, such as Figure 1As shown, the powertrain 103 includes a first axle assembly 102 and a second axle assembly 112. The first axle assembly 102 can be configured to drive a first set of wheels 104, and the second axle assembly 112 can be configured to drive a second set of wheels 114. In one example, the first axle assembly 102 is arranged near the front end 150 of the vehicle 100, thus including a front axle, and the second axle assembly 112 is arranged near the rear end 152 of the vehicle 100, thus including a rear axle. The powertrain 103 is shown in a four-wheel drive configuration, but other configurations can also be adopted. For example, the powertrain 103 can include a front-wheel drive, rear-wheel drive, or all-wheel drive configuration. In addition, the powertrain 103 can also include one or more tandem axle assemblies. Therefore, without departing from the scope of the present disclosure, the powertrain 103 can also have other configurations. Figure 1 The configuration shown is for illustration only and not for limitation. In addition, the vehicle 100 can also include other wheels not connected to the powertrain 103.

[0019] In some four-wheel drive configurations, such as Figure 1 shown, the powertrain 103 includes a transfer case 110 configured to receive the rotational power output from the transmission 108. The first drive shaft 113 is drivingly connected to the first output end 111 of the transfer case 110, and the second drive shaft 122 is drivingly connected to the second output end 121 of the transfer case 110. The first drive shaft 113 (e.g., the front drive shaft) transmits the rotational power from the transfer case 110 to the first differential 116 of the first axle assembly 102 to drive the first set of wheels 104, and the second drive shaft 122 (e.g., the rear drive shaft) transmits the rotational power from the transfer case 110 to the second differential 126 of the second axle assembly 112 to drive the second set of wheels 114. For example, the first differential 116 is drivingly coupled to a first set of axles 118 coupled to the first set of wheels 104, and the second differential 126 is drivingly coupled to a second set of axles 128 coupled to the second set of wheels 114.

[0020] In some examples, additionally or alternatively, vehicle 100 can be a hybrid vehicle, including an engine and an electric machine, each configured to provide power to one or more of the first axle assembly 102 and the second axle assembly 112. For example, one or both of the first axle assembly 102 and the second axle assembly 112 can be driven by power from the engine in a first operating mode, in which the electric machine does not operate to provide power (e.g., engine-only mode); in a second operating mode, driven by power from the electric machine, in which the engine does not operate to provide power (e.g., electric-only mode); and in a third operating mode, driven by power from the engine and the electric machine (e.g., electric assist mode). As another example, one or both of the first axle assembly 102 and the second axle assembly 112 can be an electric axle assembly, configured to be driven by an integrated electric machine.

[0021] Vehicle 100 may also include a control system 14. The control system 14 receives information from a plurality of sensors 16 and sends control signals to a plurality of actuators 18. For example, sensors 16 can include at least one clutch sensor 132 for monitoring the position of the clutch 130. When the prime mover 106 includes an engine, other sensors, such as pressure, temperature, air / fuel ratio, and composition sensors, can be connected to different locations of the vehicle 100. The plurality of actuators can include valves that control the flow of hydraulic fluid through the clutch 130. The control system 14 can include a controller 12, which can receive input data from various sensors, process the input data, and trigger the plurality of actuators 18 in response to the processed input data according to instructions or codes programmed therein, which correspond to one or more routines. In particular, the controller 12 can be a microcomputer, including a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values, such as a read-only memory chip, random access memory, keep-alive memory, and a data bus.

[0022] As described above, the transmission of the vehicle can include at least one clutch to facilitate shifting of the drive gears of the transmission. The clutch can be a wet clutch. When hydraulic fluid flows into the clutch and increases the hydraulic pressure in the clutch, the gears of the transmission can engage, causing the piston to move towards the clutch pack of the clutch against the spring force. When the hydraulic pressure is released, the opposing spring force drives the piston away from the clutch pack, causing the gears to disengage.

[0023] When it is required to engage the transmission gears, the piston initially does not exert any force on the clutch pack, which is an assembly of a separator plate and friction plates. As hydraulic fluid is delivered to the clutch, for example, into the piston chamber, the piston begins to move towards the clutch pack during the filling phase until the piston contacts the clutch pack. The initial contact of the piston with the clutch pack can be referred to as the engagement point, which can be a single contact point when the piston is axially aligned during movement.

[0024] From the contact point, torque can be transferred from the input shaft to the gear through the frictional force generated by the clutch, which may correspond to a modulation phase. During the modulation phase, hydraulic fluid does not flow into the piston chamber, but the hydraulic pressure in the clutch increases according to a modulation curve. For example, the modulation curve can be selected according to a feedforward algorithm based on initial conditions. In another example, the modulation curve can be selected according to an algorithm with a feedback loop with parameters such as controlling the clutch slip speed (e.g., the speed between the friction plates and separator plates of the clutch pack).

[0025] However, in some cases, the piston may not displace while remaining axially aligned during the filling phase. Instead, the piston may tilt relative to the axis, and when tilted, the engagement point spreads over a period of time rather than remaining a constant single-point initial contact until the piston is axially aligned. Therefore, the contact between the piston and the clutch assembly may occur during the engagement phase when the piston stops tilting, rather than at the engagement point. Torque is transferred to the gear at the start of the engagement phase and continues to be transferred throughout the duration of the engagement phase.

[0026] When the contact between the piston and the clutch pack occurs during the engagement phase rather than at the engagement point, the vehicle's driveline (e.g., the powertrain and power transmission system) may experience shocks and / or torque oscillations. The smoothness of gear shifting may thus be reduced, causing discomfort to the driver and passengers. In a clutch configuration where the inflow direction of the hydraulic fluid is axial, the shifting experience may deteriorate further, resulting in the hydraulic fluid impacting the piston in a direction perpendicular to the piston surface after entering the piston chamber. Additionally, due to the relatively narrow diameter of the fluid passage, the shifting quality may deteriorate when the inflow speed of the hydraulic fluid is high. Moreover, when the flow rate of the hydraulic fluid is high, such as when the clutch is large, the piston surface is correspondingly large, or the number of clutch discs in the clutch pack increases, resulting in an increased stroke of the piston during the filling phase, the shocks and / or torque oscillations may become significant.

[0027] To mitigate the poor gear shifting caused by the tilting of the clutch piston, in one example, the clutch can be configured with a pressure control system that includes a relatively large piston chamber volume and a diffuser for introducing hydraulic fluid into the piston chamber. Figure 2An example of a clutch 200 (e.g., a wet clutch configured as a brake) with a pressure control system 202 is described in the form of a cross-sectional view. A set of reference axes 201, representing the y-axis, x-axis, and z-axis, are provided in the figure.

[0028] The clutch 200 can be coupled to a part of a transmission 204, and the transmission 204 can be Figure 1 an embodiment of the transmission 108 in Figure 1 and the clutch 200 can be an embodiment of the clutch 130 in. In one example, the part of the transmission 204 can be a brake. The clutch pack 206 of the clutch 200 can be composed of separating disks 208 and friction disks 210 arranged alternately along the Z-axis, and the Z-axis can be perpendicular to the axial direction of the clutch 200. The clutch pack 206 can be arranged between the piston 212 and the end plate 209 of the clutch 200. For example, when the clutch 200 is in the closed position, the outermost surface of the clutch pack 206 can contact the end of the piston 212, the innermost surface of the clutch pack 206 can be in contact with the end plate 209, and the outermost and innermost surfaces are aligned with the Y-x plane. The piston 212 can be axially aligned with the clutch pack 206 and is located in the piston chamber 214 of the clutch 200. The piston 212 can be enclosed within a piston housing 216, and the inner surface of the piston housing 216 can define the volume of the piston chamber 214.

[0029] The piston 212 can include an extension portion 217 that protrudes from the piston housing 216 along the Z-axis. The extension portion 217 can provide a rigid surface through which the force applied by at least one return spring 203 can be transmitted to the piston 212. The force applied by the return spring 203 is represented by the arrow 205 and can be a return force.

[0030] The pressure control system 202 of the clutch 200 can include the piston chamber 214 and a diffuser 218. The diffuser 218 can be connected to the piston housing 216 and enclosed within the piston housing 216. The interface between the diffuser 218 and the piston housing 216 can be optionally sealed to prevent leakage of hydraulic fluid (such as oil) when flowing between the diffuser 218 and the piston chamber 214. However, in other examples, since the diffuser 219 can reduce the impact of the flow on the piston 212 and the piston 212 may not be adversely affected by leakage, sealing may not be required. Therefore, in some examples, the interface between the diffuser 218 and the piston housing 216 can be unsealed. Bolts 220 can be used to hold the diffuser 218 in place in the clutch 200 and absorb at least part of the impact of the force exerted when hydraulic fluid flows in.

[0031] The diffuser 218 is in Figures 3 - 5It is shown in more detail in and will be further described below. The diffuser 218 is also included in the pressure control system 202 of the clutch 200 and can be disposed at the intersection between the inflow passage 222 of the clutch 200 and the piston chamber 214. The inflow passage 222 can convey hydraulic fluid from a hydraulic fluid source to the piston chamber 214. For example, the hydraulic fluid can be stored in an oil tank, and the flow of the hydraulic fluid can be driven by a pump. The direction of the inflow passage 222 can be aligned with the axial direction and can convey the hydraulic fluid in the axial direction to the diffuser 218.

[0032] When the clutch 200 requires the brake to be activated, the hydraulic fluid can enter the piston chamber 214 through the inflow passage 222 via the piston housing 216. Before the start of a gear shift, the piston chamber 214 is not pressurized, and the piston 212 remains at a certain distance from the outermost surface of the clutch pack 206. Therefore, the piston 212 is not in contact with the clutch pack 206. As described above, after the brake is activated, the hydraulic oil can flow into the piston chamber 214 during the oil filling stage of the clutch operation. As the volume of the hydraulic fluid in the piston chamber 214 increases, the pressure in the piston chamber 214 may rise due to the force exerted by the return spring 203, thereby pushing the piston 212 to translate relative to the return spring 203 and towards the clutch pack 206, as shown by the arrow 207.

[0033] When the piston 212 slides towards the clutch pack 206, when the piston 212 remains aligned with the axial direction (e.g., the Z-axis) during the filling stage of the clutch operation, the piston 212 can contact the outermost surface of the clutch pack 206 at a point (e.g., the contact point). At the engagement point, the modulation stage begins, and the torque is transmitted from the input torque source (such as the input shaft) to the brake housing connected to the clutch 200. The gear is thus engaged by the clutch 200 (e.g., the clutch 200 is closed). Due to the contact between the piston 212 and the clutch pack 206, the piston 212 can apply a compressive force to the clutch pack 206 in the direction shown by the arrow 207, thereby achieving torque transmission. As the hydraulic pressure in the piston chamber 214 increases, the pressing force exerted by the piston on the clutch pack 206 may increase to the maximum force, which, as described above, can be determined according to the modulation curve or the feedforward algorithm.

[0034] Compressing the clutch pack 206 causes the separator plate 208 and the friction plate 210 to be squeezed against each other between the piston 212 and the end plate 209. The compressed clutch pack 206 applies a brake to the input shaft based on friction and drives the gear to rotate synchronously with the input torque source. When a subsequent gear shift is required, the hydraulic fluid can flow out of the piston chamber 214 to relieve the hydraulic pressure. When the hydraulic pressure in the piston chamber 214 decreases, the restoring force generated by the spring force forces the piston to translate away from the clutch pack 206, thereby decompressing the clutch pack and releasing the clutch 200 from the gear (e.g., the clutch 200 is opened).

[0035] During the filling phase when the piston 212 slides towards the clutch assembly 206, the pressure control system 202 can prevent the piston 212 from tilting. For example, the size (such as volume) of the piston chamber 214 can be large enough to apply a single pressure value to the piston 212. For example, when the piston 212 is in the contact position (e.g., in contact with the clutch assembly 206), the cross-sectional area of the flow region of the piston chamber 214 behind the piston 212 may be at least twice the cross-sectional area of the volume of the inflow passage 222. Any imbalance caused by an increase in the frictional force on one side of the piston 212 can be balanced by an increase in the return force of the return spring 203 in the area close to and corresponding to the damaged side of the piston 212. Therefore, the tilting of the piston 212 can be compensated by controlling the hydraulic pressure borne by the piston 212 and the return force of the return spring 203, and the return force of the return spring 203 will increase as the piston 212 tilts.

[0036] In addition, the impact force of the hydraulic fluid flowing into the piston 212 can be regulated by the diffuser 218. By arranging the diffuser 218 at the intersection of the inflow passage 222 and the piston chamber 214, the direction of the inflowing fluid can be prevented from axially impacting the piston 212. Instead, the diffuser 218 can receive the hydraulic fluid in a direction perpendicular to the axial direction. The hydraulic fluid can pass through at least two tangential channels (such as spiral channels) provided therein, and the hydraulic fluid is introduced into the piston chamber 214 by rotating the inflowing hydraulic fluid. The hydraulic fluid thus flows out of the diffuser 218 and enters the piston chamber 214 along a spiral path. The diffuser 218 can make the hydraulic fluid uniformly contact the piston 212, thereby dispersing the impact force of the inflowing hydraulic fluid on the piston 212 so that the impact force does not concentrate or unevenly distribute in any area of the piston surface.

[0037] The diffuser 218 is shown in Figure 3 in a view along the axial direction (e.g., the Z-axis) and Figure 2 the direction shown by the arrow 205, and is shown in Figure 4 in a cross-sectional view along the x-y plane, and is shown in Figure 5 in a cross-sectional view along the same x-y plane but at an angle opposite to Figure 4 . As shown in Figure 4 and Figure 5 , the diffuser 218 can be located inside the piston chamber 214 and is fixed to the piston housing 216 by bolts 220. A sealing device (such as an O-ring 402) can be installed at the interface between the bolts 220 and the piston housing 216 to ensure a sealed engagement of the bolts with the piston housing 216, so that the hydraulic fluid does not leak from the hole 404 of the piston housing 216 for receiving the bolts 220.

[0038] As shown in Figure 3As shown, the diffuser 218 may include a plate 302. The first surface 304 of the plate forms a smooth, continuous, and unbroken surface except for the opening 306 for receiving the bolt 220. The orientation of the plate is perpendicular to the axial direction, for example, coplanar with the Y-x plane. The plate 302 may have a curved outer geometry, such as Figure 3 shown, which is a non-limiting example of the outer geometry of the plate 302. For example, the plate 302 may have various outer geometries. In addition, the relative dimensions of the plate, including thickness, length, and width, may differ from the illustrated dimensions without departing from the scope of the present disclosure.

[0039] Looking again Figure 4 and Figure 5 , the plate 302 of the diffuser 218 is spaced apart from the piston housing 216 and does not directly contact the piston housing 216. The diffuser 218 also has a shank 406 that extends between the plate 302 and the piston housing 216 and is continuous with the plate 302. In other words, the diffuser 218 is a single continuous structure composed of the plate 302 and the shank 406. The opening 306 may completely pass through the shank 406 along the Z-axis, providing a sleeve for receiving and mating with the bolt 220. As Figure 4 shown, the diameter 408 of the shank 406 at its widest region may be narrower than the width 410 (or length) of the plate 302.

[0040] As Figure 5 shown, the shank 406 may include a first channel 502 and a second channel 504 that extend through the material of the diffuser 218, forming a helical path through the diffuser 218. The first and second channels 502, 504 may fluidly couple the inflow channel 222 (as Figure 2 shown) with the piston chamber 214. As shown by the arrow 506, the first and second channels 502 are oppositely arranged on the central axis 501 of the diffuser 218 and may discharge the inflowing hydraulic fluid into the region between the piston housing 216 and the plate 302 of the diffuser 218 in the piston chamber 214. The perpendicular arrangement of the plate 302 with respect to the axial direction and the parallel arrangement with the piston housing 216 may force the hydraulic fluid to initially flow in a direction perpendicular to the axial direction after entering the piston chamber 214.

[0041] The hydraulic fluid may flow from the first and second channels 502, 504 into the region between the piston housing 216 and the plate 302 in the piston chamber 214 and flow around the edge of the plate 302. The inflow path through the diffuser 218 may force the hydraulic fluid to flow tangentially, causing the hydraulic fluid to rotate along a double-helical path into the piston chamber region between the plate 302 of the diffuser 218 and the piston 212 (as Figure 2 shown). The hydraulic fluid does not directly contact the piston 212 axially but is tangentially distributed on the surface of the piston 212.

[0042] Figure 6 shows an example of a method 600 of operating one or more clutches of a vehicle to facilitate gear shifting. These clutches can be similar to Figure 2 the clutch 200 in Figure 1 and implemented in a transmission, such as Figure 1 the transmission 108 in Figure 1 The instructions for performing the method can be executed by a controller, such as

[0043] the controller 12 in

[0044] At 602, the method includes estimating and / or measuring the current state of the transmission. For example, data from transmission sensors can be used to determine which gears of the transmission are engaged and disengaged based on the position of the clutches, the torque input to the transmission, the torque output from the transmission, etc. By way of example, the transmission can include a first clutch configured to engage a first gear (or first gear set) and a second clutch configured to engage a second gear (or second gear set). The current state of the transmission can include the first clutch being disengaged from the first gear and the second clutch being engaged with the second gear.

[0045] If a gear shift request is received at 604, the method proceeds to 608 to adjust the engagement and disengagement of the transmission gears. For example, the requested gear shift can be from second gear to first gear. In response to the request, the first clutch can be actuated to close. Valves and pumps that control the flow of hydraulic fluid can be adjusted and / or activated to deliver hydraulic fluid through an inlet passage to the piston chamber of the first clutch. When the hydraulic fluid flows into the piston chamber, the hydraulic fluid first passes through a diffuser that is disposed at the intersection of the inlet passage and the piston chamber and is located within the piston chamber. The hydraulic fluid passes through the tangential passages of the diffuser, causing the hydraulic fluid to rotate into the piston chamber, thereby minimizing the direct axial impact of the hydraulic fluid on the piston of the first clutch. As the hydraulic oil flows into the piston chamber, the pressure within the piston chamber increases and the piston is forced towards the clutch pack of the first clutch. Since the volume of the piston chamber and the return force exerted by at least one return spring of the clutch exert a single pressure on the piston, the piston remains axially aligned.

[0046] The first gear is locked to the clutch based on the frictional force generated between the friction plates of the clutch pack of the first clutch. Torque from a torque input, such as an input shaft, can be transmitted to the first gear.

[0047] Meanwhile, after receiving a shift request, the second clutch can be adjusted to an open position to disengage the second gear. For example, a regulating valve and a pump for directing hydraulic fluid to the first clutch can also include a regulating valve and a pump for releasing hydraulic fluid from the second clutch, thereby dissipating the hydraulic pressure accumulated therein. As the hydraulic oil flows out of the piston chamber of the second clutch, the hydraulic pressure in the piston chamber decreases, and the return force of at least one return spring of the second clutch will be greater than the hydraulic pressure. The return force forces the piston of the second clutch away from the clutch pack of the second clutch. Torque is no longer transmitted to the second gear through the second clutch. The method returns to the starting point.

[0048] In this way, the shift process of the wet clutch transmission will not generate shocks or torque oscillations. By installing a pressure control system (including a relatively large piston chamber volume and a diffuser) on at least one clutch of the transmission, the hydraulic pressure and the hydraulic oil flowing into the piston chamber can be alleviated during the oil filling stage of the clutch operation. The relatively large piston chamber volume allows a single pressure value to be applied to the piston, thereby reducing the possibility of the piston tilting during the filling stage of the clutch operation. The contact between the clutch piston and the clutch pack may occur at a single contact point, such as the engagement point, rather than being distributed during the engagement stage. The return force exerted by at least one return spring of the clutch can counteract any unbalanced frictional force on the piston. In addition, the direction and path of the hydraulic fluid flowing into the piston chamber can be controlled by the diffuser, which can direct the fluid to flow in along a tangential path, thereby reducing the impact of the fluid on the piston. The pressure control system described herein can provide a simple and low-cost mechanism that can improve the shift quality and reduce the sensitivity of clutch control to variable initial conditions such as slip speed and / or oil temperature.

[0049] Figures 2 - 5Shows an example configuration of the relative positioning of various components. If the elements shown in the figure are in direct contact or directly coupled to each other, then in at least one example, these elements can be referred to as being in direct contact or directly coupled respectively. Similarly, in at least one example, elements shown adjacent or contiguous to each other can be adjacent or contiguous to each other respectively. For example, elements in face-to-face contact with each other can be referred to as face-to-face contact elements. Another example is that in at least one example, elements are placed separately from each other with only space in between and no other elements, and can be referred to as being placed separately from each other. Also, elements shown above / below each other, on opposite sides of each other, or to the left / right of each other relative to each other can be referred to as such elements. Additionally, as shown in the figure, in at least one example, the topmost element or element point can be referred to as the "top" of the element, and the bottommost element or element point can be referred to as the "bottom" of the element. The top / bottom, upper / lower, above / below used herein can be relative to the vertical axis in the figure and are used to describe the positioning of the various elements in the figure relative to each other. Thus, in one example, an element shown above other elements is vertically positioned above the other elements. For another example, the shapes of the elements depicted in the figure can be referred to as having these shapes (e.g., circular, straight, planar, curved, round, chamfered, beveled, or similar shapes). Additionally, in at least one example, elements shown intersecting each other can be referred to as intersecting elements or intersecting each other. Further, in one example, an element shown inside or outside another element can be referred to as such an element. Figures 2 - 5 Shown approximately to scale.

[0050] The following claims particularly point out certain combinations and sub-combinations that are regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or equivalent elements. These claims should be understood to include one or more such elements, neither requiring nor precluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics can be claimed by modifying these claims or by presenting new claims in this application or related applications. These claims, whether broader, narrower, the same, or different in scope from the original claims, are also regarded as being included in the subject matter of this disclosure.

Claims

1. A pressure control system for a clutch, characterized in that: The pressure control system includes a piston housing including a piston chamber and a piston; and A diffuser is located in the piston chamber, and the diffuser includes a plurality of tangential channels for guiding the fluid to flow into the piston chamber.

2. The pressure control system of claim 1, wherein the diffuser is located at the intersection of an inflow passage and the piston chamber, the inflow passage delivering fluid to the piston chamber.

3. A pressure control system according to claim 2, wherein the diffuser is coupled to the piston housing by bolts extending through the piston housing, wherein the bolts seal the diffuser, or the multiple tangential channels of the diffuser couple the inflow channel with the piston chamber fluid, and the system further includes at least one return spring, which applies a return force to the extended portion of the piston in a direction away from the clutch.

4. The pressure control system as claimed in claim 1, wherein said diffuser has a plate arranged perpendicular to the clutch shaft direction, and a stem extending between said plate and said piston housing.

5. The pressure control system of claim 4, wherein the plurality of tangential passages of the diffuser discharge fluid into the area between the plate and the piston housing in the piston cavity.

6. A pressure control system as described in claim 5, wherein the fluid flows perpendicular to the clutch axis after entering the piston chamber, and after flowing through the edge of the plate, enters the area between the plate and the piston in the piston chamber along a spiral path.

7. The pressure control system of claim 1, wherein the piston is located between a plurality of friction plates and the diffuser.

8. A transmission, characterized in that: The transmission includes gears; and A clutch connected to the gear, the clutch having a diffuser to reduce the impact of hydraulic fluid on the clutch piston, wherein the volume of the clutch piston chamber is configured to apply a pressure value to the clutch piston so as to combine with the return force of at least one return spring to keep the clutch piston aligned in a direction perpendicular to the axial direction.

9. The transmission of claim 8, wherein the diffuser is completely enclosed within the piston cavity and is configured to distribute hydraulic fluid to different portions of the piston cavity, with the hydraulic fluid bypassing portions of the piston adjacent to the diffuser.

10. The transmission of claim 8, wherein the diffuser receives hydraulic fluid from the inflow passage in a direction parallel to the axial direction and discharges the hydraulic fluid into the piston chamber through the diffuser along a tangential path, or the volume of the piston chamber is configured to include a single pressure applied to the piston surface to overcome the force of at least one return spring, and the piston chamber extends around most of the circumference of the piston.

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