A wet clutch with segmented self-adjusting control

Abstract

The present invention relates to a segmented, self-adjusting wet clutch, belonging to the technical field of automatic transmissions. The clutch clutch comprises a transmission shaft and a clutch piston cylinder. A piston is provided in the piston chamber of the clutch piston cylinder, and the piston's active surface is divided into an inner active surface and an outer active surface. A baffle ring is provided in the clutch piston cylinder, which divides the piston chamber into a first cavity and a third cavity. The first cavity is connected to a main oil passage in the transmission shaft, and the inner active surface and the outer active surface are located in the first cavity and the third cavity, respectively. The clutch piston cylinder also comprises a radially extending mounting hole. A plurality of through holes are provided between the mounting hole and the piston chamber, namely a first throttle hole, a second throttle hole, a third throttle hole, and a second oil drain hole. The clutch piston cylinder also comprises a first oil drain hole connected to the mounting hole. A shift auxiliary control valve is provided in the mounting hole, comprising a base, a valve piston, a valve stem, and a valve sleeve arranged in sequence. The present invention can achieve auxiliary adjustment of the clutch at each control stage during the shifting process.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic transmissions, and in particular relates to a segmented self-adjusting controlled wet clutch. Background Art

[0002] AT hydraulic automatic transmission usually contains multiple multi-plate wet shift clutches. Its shifting is that the transmission TCU issues a shift control command after calculating the shift logic. According to the current gear and the target gear, the proportional solenoid valve corresponding to the clutch that needs to be engaged and disengaged is driven to act. According to the size of the output control current, the transmission oil pressure and flow at the outlet of the proportional solenoid valve can be controlled. After adjustment by the proportional solenoid valve, the transmission oil enters the piston chamber of the shift clutch through the oil channel. When the thrust generated by the oil pressure can overcome the resistance of the return spring and the friction resistance of the clutch piston itself, the oil pushes the piston to move and gradually compresses the friction plate and steel plate, so that the driven part and the active part of the clutch engage to transmit power.

[0003] Throughout the clutch engagement or disengagement process, the pressure, flow rate, and duration directly determine the quality of the entire shift. Due to inherent characteristics of the proportional solenoid valve (such as the excitation current for initial pressure buildup and hysteresis), which limit control of certain pressure and flow ranges, precise control of clutch engagement or disengagement throughout the entire shifting process is difficult. Therefore, controlling shift quality solely through the proportional solenoid valve requires extensive calibration and testing. Therefore, a constant oil drain hole is typically incorporated into the clutch piston cylinder on the oil inlet side of the wet clutch during the design process to help reduce pressure shock during the clutch filling phase and accelerate the oil drain process during disengagement, reducing disengagement time. However, this auxiliary valve performs a relatively simple function, only providing a limited regulatory effect during a specific phase (such as filling or disengagement) and still cannot fully assist in the overall clutch control process. Therefore, the shift calibration and commissioning process still requires extensive testing. Summary of the Invention

[0004] In order to solve the problems of single proportional solenoid valve control and the functional limitations of the constant oil drain hole solution mentioned above, the present invention provides a wet clutch with segmented self-adjusting control, which adopts an auxiliary control valve to realize auxiliary adjustment of the clutch in each control stage during the shifting process, thereby achieving more precise adjustment and control for the entire control process, greatly reducing the testing and calibration workload of the automatic transmission shift quality.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a segmented self-adjusting wet clutch comprising a transmission shaft and a clutch piston cylinder, the clutch piston cylinder being fixed to the transmission shaft, a piston being provided in a piston chamber of the clutch piston cylinder, the piston having an active surface divided into an inner active surface and an outer active surface in a radial direction and arranged in a stepped manner, a baffle ring being provided in the clutch piston cylinder, the baffle ring dividing the piston chamber into a first cavity and a third cavity, the first cavity being connected to a main oil passage in the transmission shaft, the inner active surface being located in the first cavity, and the outer active surface being located in the third cavity;

[0006] A radially extending mounting hole is further provided in the clutch piston cylinder. The mounting hole is a through hole. A plurality of through holes are provided on the cylinder wall between the mounting hole and the piston cavity. The plurality of through holes are respectively a first throttle hole, a second throttle hole, a third throttle hole and a second oil drain hole. A first oil drain hole that is always connected to the mounting hole is also provided on the cylinder wall of the clutch piston cylinder. The first throttle hole is connected to the first cavity, and the second throttle hole, the third throttle hole and the second oil drain hole are all connected to the third cavity.

[0007] A shift auxiliary control valve is provided in the mounting hole, comprising a base, a valve piston, a valve stem and a valve sleeve arranged in sequence. The base is fixed in the mounting hole and is provided with a through-hole. The space between the base and the transmission shaft and the hole together form a second cavity. The second cavity is always connected to the first cavity through the first throttle hole. The valve stem is relatively slidably provided in the valve sleeve, the proximal end of the valve stem is inserted into the valve piston, and the distal end of the valve sleeve is axially positioned in the mounting hole. A valve spring is provided outside the valve sleeve, and the two ends of the valve spring respectively press against the valve sleeve and the valve piston.

[0008] In the initial state of the wet clutch, the valve acting surface of the valve piston forms a blockage for the channel in the base, the side surface of the valve piston forms a blockage for the second throttle hole, the first slot hole set on the valve piston is aligned with the third throttle hole, and the second slot hole set on the valve sleeve is aligned with the second oil drain hole and avoids the valve stem.

[0009] Furthermore, the aperture of the second throttle hole is smaller than that of the first throttle hole, and through the throttling effect of the second throttle hole, the oil pressure in the second cavity pushes the valve piston to move and can block the third throttle hole; the aperture of the third throttle hole is larger than that of the second throttle hole.

[0010] Furthermore, the valve piston is a cylindrical structure with one end open, the closed end of which is the valve action surface, and the open end is used to receive the insertion of the valve stem.

[0011] Furthermore, the longitudinal cross-section of the valve stem is T-shaped, and its T-shaped head is inserted into the valve piston through the open end of the valve piston, and the outer diameter of the T-shaped head matches the inner diameter of the valve piston, and the proximal end of the valve spring is pressed against the T-shaped head.

[0012] Furthermore, the longitudinal section of the valve sleeve is T-shaped, its T-shaped head is away from the valve piston, and is axially fixed in the mounting hole of the clutch piston cylinder by a retaining ring, and the central hole of the valve stem in the valve sleeve is a through hole; the distal end of the valve spring is pressed against the T-shaped head.

[0013] Furthermore, a gasket is provided outside the valve sleeve, and the distal end of the valve spring rests on the gasket.

[0014] Furthermore, a fixing hole is provided on the base, and a fixing member passes through the fixing hole to fix the base in the mounting hole.

[0015] Furthermore, an annular groove communicating with the third throttle hole is provided on the inner wall of the mounting hole.

[0016] Furthermore, the engagement process of the wet clutch includes the following three stages:

[0017] (1) First stage: The oil enters the first cavity through the main oil channel. One path of oil acts on the inner working surface of the piston, forming a thrust F1, pushing the piston to move and eliminating the idle stroke between the piston and the first steel plate in the clutch piston cylinder; the other path of oil enters the second cavity through the first throttle hole, forming a thrust F2 acting on the valve piston, and F2 is smaller than the initial elastic force of the valve spring;

[0018] (2) Second stage: The oil pressure increases, making the thrust F2 greater than the initial elastic force of the valve spring, pushing the valve piston to move. A portion of the oil in the second chamber enters the third chamber through the second throttle hole, acting on the outer surface of the piston to form a thrust F3. Through the action of the second throttle hole, the side of the valve piston can completely cover the third throttle hole, and the valve stem moving with the valve piston completely covers the second oil drain hole.

[0019] (3) The third stage: The oil pressure continues to increase, pushing the valve piston to continue moving, so that the third throttle hole connects the second cavity and the third cavity. The oil pushes the piston to quickly press the friction plate and steel plate of the wet clutch to achieve full engagement.

[0020] Furthermore, the disengagement process of the wet clutch includes the following two stages:

[0021] (1) First stage: After the proportional solenoid valve in the wet clutch is powered off, the oil in the third chamber enters the second chamber through the third throttle hole and the second throttle hole, then enters the first chamber through the first throttle hole, and finally is discharged into the oil tank through the main oil channel from the drain port of the proportional solenoid valve;

[0022] (2) The second stage: As the oil flows out, the pressure in the third cavity, the second cavity and the first cavity also decreases. When the thrust F2 in the second cavity is less than the elastic force of the valve spring, the valve spring pushes the valve piston to reset, and the valve stem slides along the valve sleeve; when the second oil drain hole is no longer blocked by the valve stem, part of the oil remaining in the third cavity due to the centrifugal force of the clutch rotation will be discharged into the oil tank through the second oil drain hole, the second slot hole and the center hole inside the valve sleeve; part of the residual oil in the third cavity near the transmission shaft flows into the valve spring gap through the third throttle hole and the first slot hole on the valve piston, and is finally discharged into the oil tank through the first oil drain hole.

[0023] The beneficial effects of the present invention are as follows: the present invention adopts a multi-element combination shift auxiliary control valve on the wet clutch, which can realize the three-stage auxiliary control function of the clutch engagement process, and can significantly improve the rapid oil filling and elimination of idle stroke stage, smooth control of the slip control stage, and control effect of the rapid engagement stage during the clutch engagement process, as well as improve the oil leakage speed during the clutch separation process and the rapid discharge effect of residual oil.

[0024] Compared with the clutch control using only a single constant oil drain hole in the prior art, the scheme described in the present invention can better play an auxiliary control role in the shifting process control, shorten the shifting time, make the shifting quality smooth and impact-free, and make the control effect more precise and the control method simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 Schematic diagram of the structure of the wet clutch with segmented self-adjusting control according to the present invention;

[0027] Figure 2 Schematic diagram of the distribution of oil holes on the clutch piston cylinder in the present invention;

[0028] Figure 3 This is a schematic diagram of the working principle of the shift assist control valve of the present invention during the first stage of the wet clutch engagement process;

[0029] Figure 4 This is a schematic diagram of the working principle of the shift assist control valve of the present invention during the second stage of the wet clutch engagement process;

[0030] Figure 5This is a schematic diagram of the working principle of the shift assist control valve of the present invention during the third stage of the wet clutch engagement process;

[0031] Figure 6 This is a schematic diagram of the working principle of the shift assist control valve of the present invention in the first stage of the wet clutch disengagement process;

[0032] Figure 7 This is a schematic diagram of the working principle of the shift assist control valve of the present invention in the second stage of the wet clutch disengagement process;

[0033] Figure 8 Schematic diagram of the structure of a wet clutch using a constant oil drain hole in the prior art;

[0034] Figure 9 It is the proportional solenoid valve drive control parameter formed after debugging and calibration when a wet clutch solution with a constant oil drain hole is adopted in the prior art;

[0035] Figure 10 The wet clutch scheme using a constant oil drain hole in the prior art and Figure 9 The test curve diagram of the control parameters shown in the figure is on the actual vehicle;

[0036] Figure 11 The proportional solenoid valve drive control parameters formed after debugging and calibration when the wet clutch solution of the shift auxiliary control valve is adopted in the present invention;

[0037] Figure 12 The wet clutch scheme and the shift auxiliary control valve of the present invention are Figure 11 The test curve diagram of the control parameters shown in the figure is on the actual vehicle;

[0038] Figure numerals: 1. Clutch piston cylinder, 101. Spacer ring, 2. Fixing pin, 3. Base, 4. Valve piston, 401. Valve acting surface, 402. First slot, 5. Valve spring, 6. Valve stem, 7. Gasket, 8. Valve sleeve, 801. Center hole, 802. Second slot, 9. Retaining ring, 10. First throttle hole, 11. Second throttle hole, 12. Third throttle hole, 13. First oil drain hole, 14. Second oil drain hole, 15. Piston, 1501. Inner acting surface, 1502. Outer acting surface, 16. Return spring, 17. Friction plate, 18. Steel plate, 19. Main oil channel, 20. Drive shaft, 21. First cavity, 22. Second cavity, 23. Third cavity, 24. Clutch outer hub, 25. Clutch inner hub, 26. Gear, 27. Normal oil drain hole. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but they are not intended to limit the invention in any way.

[0040] like Figure 1 The figure shows a step-by-step self-adjusting wet clutch. Its overall structure is essentially the same as that of a conventional wet clutch, including a clutch piston cylinder 1, a piston 15, a return spring 16, a friction plate 17, a steel plate 18, a transmission shaft 20, a clutch inner hub 25, a clutch outer hub 24, and a gear 26. The following describes only the connections between the main components. The clutch piston cylinder 1 is fixed to the transmission shaft 20 using an interference fit (or other suitable fixing method). The piston 15 is disposed within the piston cavity of the clutch piston cylinder 1. The ends of the return spring 16 abut against the piston 15 and the clutch inner hub 25, respectively, to control the return of the piston 15 during the clutch disengagement phase. The friction plate assembly, consisting of the friction plate 17 and the steel plate 18, is disposed within the clutch hub, consisting of the clutch inner hub 25 and the clutch outer hub 24. The clutch inner hub 25 is fixed to the transmission shaft 20, and the clutch outer hub 24 is connected to the gear 26.

[0041] When the wet clutch is in the engaged state, the friction plate 17 and the steel plate 18 are pressed by the piston 15. At this time, the power input from the drive shaft 20 is transmitted to the friction plate group through the clutch inner hub 25, then to the clutch outer hub 24, and finally output through the gear 26.

[0042] The structure of the shift assist control valve proposed in the present invention, its installation on the wet clutch, and its working principle are described in detail below.

[0043] Continue to refer Figure 1As shown, a radially extending mounting hole is provided on one side of the piston chamber of the clutch piston cylinder 1. The shift-assisting control valve is mounted in this mounting hole, with the length of the shift-assisting control valve being less than the depth of the mounting hole. The shift-assisting control valve primarily comprises a base 3, a valve piston 4, a valve spring 5, a valve stem 6, a gasket 7, a valve sleeve 8, and a retaining ring 9. The base 3 is provided with fixing holes, which are secured to the mounting hole of the clutch piston cylinder 1 via fixing pins 2 or other fixing members such as screws. The base 3 also serves as the bottom support for the shift-assisting control valve. An axially extending channel is provided within the base 3. The valve piston 4 is mounted on the side of the base 3 facing away from the transmission shaft 20. This cylindrical structure is open at one end and closed at the other. The closed end forms the valve operating surface 401 of the valve piston 4 and aligns with one end of the channel within the base 3, thereby sealing the channel when the shift-assisting control valve is in its initial state (which also applies to the wet clutch). The valve stem 6 has a T-shaped longitudinal cross-section. Its T-shaped head is inserted into the valve piston 4 through the open end of the valve piston 4, and its outer diameter matches the inner diameter of the valve piston 4. The body of the valve stem 6 is inserted into the center hole of the valve sleeve 8 and slides in engagement with the valve sleeve 8. The valve sleeve 8 has a T-shaped longitudinal cross-section, with its T-shaped head facing away from the valve piston 4. It is axially secured within the mounting hole of the clutch piston cylinder 1 by a retaining ring 9. The center hole of the valve sleeve 8 is a through hole. A valve spring 5 and a gasket 7 are also sheathed around the valve sleeve 8. The proximal end of the valve spring 5 contacts the valve piston 4, while the distal end contacts the gasket 7. The gasket 7 is used to adjust the initial spring force of the valve spring 5 in its initial state. Increasing the number of gaskets 7 increases the initial spring force, while decreasing the number decreases it.

[0044] It should be noted that the “proximal end” and “distal end” mentioned in the present invention are both based on the transmission shaft 20 , the end close to the transmission shaft 20 is the “proximal end”, and the end far from the transmission shaft 20 is the “distal end”.

[0045] like Figure 2As shown, the piston 15's active surface is radially divided into an inner active surface 1501 and an outer active surface 1502, separated by a predetermined axial distance. Consequently, the inner active surface 1501 and the outer active surface 1502 form a stepped surface, with the inner active surface 1501 proximal to the transmission shaft 20 and the outer active surface 1502 distal to the transmission shaft 20. A baffle ring 101 is provided on the side of the clutch piston cylinder 1 facing the piston 15. This baffle ring 101 extends axially within the piston cavity along the transmission shaft 20, radially dividing the piston cavity into two parts: a first cavity 21 proximal to the transmission shaft 20, and a third cavity 23 distal to the transmission shaft 20. Of the two active surfaces of the piston 15, the one within the first cavity 21 is the annular inner active surface 1501, while the one within the third cavity 23 is the annular outer active surface 1502. A main oil passage 19 is provided within the drive shaft 20 of the wet clutch. One end of the main oil passage 19 opens onto the circumferential surface of the drive shaft 20 and communicates with the first cavity 21. The space between the base 3 and the axial surface of the drive shaft 20, as well as the channel within the base 3, together form a second cavity 22. The second cavity 22 and the first cavity 21 are communicated via a first throttle hole 10 provided on the clutch piston cylinder 1. A second throttle hole 11, a third throttle hole 12, and a second oil drain hole 14 are also provided on the side of the clutch piston cylinder 1 facing the piston 15. A first oil drain hole 13 is provided on the side of the clutch piston cylinder 1 facing away from the piston 15. The second throttle hole 11, the third throttle hole 12, and the second oil drain hole 14 are separated from the first throttle hole 10 by a spacer ring 101. Therefore, the second throttle hole 11, the third throttle hole 12, and the second oil drain hole 14 all communicate with the third cavity 23.

[0046] The inner ends of the second throttle hole 11 and the second oil drain hole 14 are both opened to the mounting hole wall in the clutch piston cylinder 1, and the outer end openings are connected to the third cavity 23. The inner end of the third throttle hole 12 is opened to the mounting hole wall of the clutch piston cylinder 1, and the outer end opening is connected to the third cavity 23.

[0047] When the wet clutch is in its initial state, the shift-assisting control valve is also in its initial state. The valve operating surface 401 on one end of the valve piston 4 abuts the end surface of the base 3 to block the second cavity 22. Simultaneously, the side of the valve piston 4, close to the base 3, blocks the second throttle hole 11. Furthermore, a first slot 402 is provided on the side of the valve piston 4, aligned and connected to the third throttle hole 12. The T-shaped head of the valve sleeve 8 is provided with a second slot 802 that radially penetrates the valve sleeve 8 and, in the initial state, aligns and connects with the second oil drain hole 14. The inner side of the second slot 802 is connected to the center hole 801 in the valve sleeve 8. The first oil drain hole 13 is connected to the space outside the valve sleeve 8 where the valve spring 5 is located.

[0048] Preferably, a circumferentially extending annular groove is provided on the wall of the mounting hole at the inner end opening of the third throttle hole 12 , and the third throttle hole 12 is connected to the first slotted hole 402 on the side surface of the valve piston 4 through the annular groove.

[0049] Preferably, an annular groove is provided on the outer circumferential surface of the valve sleeve 8 , and the second oil drain hole 14 is connected with the second slotted hole 802 through the annular groove.

[0050] Multiple piston seals are provided between the piston 15 and the clutch piston cylinder 1 and the transmission shaft 20. The piston seals can be sealing rings. The piston seals can be provided on the piston 15, the clutch piston cylinder 1 or the transmission shaft 20. The specific details can be determined according to design requirements.

[0051] Figure 1 、 2 The figure shows the initial state of the wet clutch. The control process of the wet clutch is divided into two types of control: engagement and separation. Therefore, in the following content, Figures 3-5 The control principle of the shift auxiliary control valve during the clutch engagement process is explained. Figure 6-7 The control principle of the shift assist control valve during clutch disengagement is described. The directional words involved, such as "up", "down", "left", "right", etc., are based on the corresponding drawings.

[0052] The engagement process of the wet clutch can be divided into the following three stages:

[0053] (1) The first stage: Figure 3 As shown in the figure, the arrow indicates the direction of oil flow. The oil first enters the first cavity 21 through the main oil channel 19. One path of oil impacts the inner working surface 1501 of the piston 15 to form a thrust F1, F1=P1×S1, P1 is the oil pressure value in the first stage, S1 is the annular area of ​​the inner working surface 1501, and the value of the thrust F1 generated needs to be greater than the sum of the initial elastic force of the return spring 16 and the resistance of the piston seal to push the piston 15 to the right, thereby eliminating the idle stroke L between the piston 15 and the first steel plate 18 (as shown in FIG. Figure 2 As shown in the figure, another oil path enters the second cavity 22 through the first throttle hole 10 and impacts the valve operating surface 401 of the valve piston 4, generating a thrust F2, where F2 = P2 × S2. P2 is the pressure generated when the oil enters the second cavity 22 after passing through the first throttle hole 10 (due to the throttling effect of the small hole of the first throttle hole 10, a pressure differential is generated, so P2 is smaller than P1), and S2 is the area of ​​the valve operating surface 401. When the F2 value is smaller than the initial elastic force of the valve spring 5, the valve piston 4 cannot be pushed upward. Otherwise, the valve piston 4 is pushed upward.

[0054] The purpose of the first stage is to quickly eliminate the idle stroke L between the piston 15 and the first steel plate 18. Therefore, the key technical design feature is to ensure that the oil in the first stage flows into the first cavity 21 at a relatively high flow rate, while controlling the flow rate of the oil flowing into the second cavity 22. This prevents excessive oil from entering the second cavity 22 and lifting the valve piston 4, allowing the oil to enter the third cavity 23 through the second cavity 22 and the second throttle hole 11. Therefore, the P1 value in this stage must ensure that F1 is greater than the sum of the initial elastic force of the return spring 16 and the resistance of the piston seal, and F2 is less than the initial elastic force of the valve spring 5. This ensures that the piston 15 can move rightward to eliminate the idle stroke, while the valve piston 4 cannot move upward.

[0055] In this embodiment, the volume of the third cavity 23 is approximately three times that of the first cavity 21. Therefore, according to the principle that volume equals flow rate multiplied by time, the time for the oil in this embodiment to act on the piston 15 in the first cavity 21 to control and eliminate the idle stroke L is equivalent to about 30% of the time for the oil in the prior art to act on the piston in the piston cavity (i.e., the first cavity 21 and the third cavity 23) to eliminate the idle stroke. In this way, the present invention can significantly shorten the control time of this stage compared to the prior art. The prior art wet shift clutch structure can refer to Figure 8 As shown, the piston cavity is not divided into two separate cavities, but remains an integrated cavity.

[0056] (2) The second stage: Figure 4 As shown in the figure, the arrow indicates the direction of oil flow. After the first stage, when P1 gradually increases and F2 exceeds the initial elastic force of the valve spring 5, the valve piston 4 is pushed upward (the upward position in the figure is actually away from the transmission shaft 20). Some oil then enters the third chamber 23 through the second throttle hole 11. This oil impacts the outer surface 1502 of the piston 15, generating a thrust F3, where F3 = P3 × S3. P3 is the pressure generated by the oil entering the third chamber 23 through the second throttle hole 11 (due to the pressure differential created by the small throttling effect of the second throttle hole 11, and its aperture is much smaller than that of the first throttle hole 10, P3 is much smaller than P2 and P1), and S3 is the annular area of ​​the outer surface 1502. The combined force of F1 and F3 acts on the piston 15, with F1 overcoming the return spring 16 and frictional resistance, and F3 continuously pushing the piston 15 to the right, gradually compressing the friction plate 17 and the steel plate 18.

[0057] The purpose of the second stage is to enable the clutch to be in a slip state, so that the torque and speed can change smoothly and avoid engagement shock. Therefore, in this stage, the oil flow in the third cavity 23 and the pressure on the outer surface 1502 need to change gradually and smoothly from small to large, among which the second throttling hole 11 plays a key role in throttling and reducing pressure, and its aperture value is the key to the design. Specifically, the aperture design of the second throttling hole 11 needs to achieve the following purposes: (1) the upper limit of the rise of the P2 pressure in this stage can be limited to ensure that the side of the valve piston 4 can completely cover the third throttling hole 12 to prevent oil from entering the third throttling hole 12; (2) the valve stem 6 moves with the valve piston 4, and the amplitude of the movement needs to ensure that the position of the valve stem 6 after moving in the valve sleeve 8 can completely cover the second oil drain hole 14 to prevent the oil in the third cavity 23 from being discharged into the oil tank through the second oil drain hole 14.

[0058] (3) The third stage: Figure 5 As shown, the arrow in the figure indicates the direction of oil flow. After the second stage is completed, as the value of P1 continues to increase, the value of P2 also increases. When F2 exceeds the current elastic force of the valve spring 5, the valve piston 4 is pushed to continue moving upward, so that the third throttle hole 12 is no longer blocked by the valve piston 4, connecting the second cavity 22 and the third cavity 23. A portion of the oil in the second cavity 22 enters the third cavity 23 through the third throttle hole 12. Because the aperture of the third throttle hole 12 is larger than that of the second throttle hole 11, the majority of the oil will enter the third cavity 23 through the third throttle hole 12. Since both the second throttle hole 11 and the third throttle hole 12 are connected to the third cavity 23 at this stage, the flow rate and pressure in the third cavity 23 will increase rapidly, causing the clutch friction plate 17 and the steel plate 18 to be quickly compressed and ultimately achieve full engagement.

[0059] The purpose of the third stage is to enable the clutch to engage quickly and form sufficient torque reserve. Therefore, the third throttle hole 12 plays a key role in increasing flow and raising pressure in this stage. Its aperture value is the key to the design and needs to be significantly larger than the aperture of the second throttle hole 11.

[0060] The disengagement process of the wet shift clutch can be divided into the following two stages:

[0061] (1) The first stage: Figure 6 As shown in the figure, the arrow indicates the direction of oil flow. After the proportional solenoid valve is powered off, its oil drain port opens, and the oil in the clutch oil chamber will flow out from the oil drain port. The oil in the third cavity 23 enters the second cavity 22 through the third throttle hole 12 and the second throttle hole 11, and then enters the first cavity 21 through the first throttle hole 10, and then passes through the main oil channel 19 and is discharged from the proportional solenoid valve oil drain port to the oil tank.

[0062] (2) The second stage: Figure 7 As shown in the figure, the arrows indicate the direction of oil flow. As the oil flows out of the clutch cavity, the pressure in the third cavity 23, the second cavity 22, and the first cavity 21 also decreases. When the thrust F2 in the second cavity 22 is less than the elastic force of the valve spring 5, the valve spring 5 resets, causing the valve piston 4 to move toward the base 3, and the valve stem 6 also slides along the valve sleeve 8. When the second oil drain hole 14 is no longer blocked by the valve stem 6, the residual oil in the third cavity 23 due to the centrifugal force of the clutch rotation will be discharged into the oil tank through the second oil drain hole 14, the second slot 802, and the center hole 801 in the valve sleeve 8. In addition, the residual oil in the third cavity 23 near the transmission shaft 20 will flow through the third throttle hole 12 and the first slot 402 on the valve piston 4 into the gap between the valve spring 5 and finally be discharged into the oil tank through the first oil drain hole 13.

[0063] Comparative test: The gear shifting control process is tested on an actual vehicle to compare the control effects of the present invention scheme with the original scheme of the prior art. The effect is mainly judged based on whether the gear shifting control quality is smooth and the improvement effect of the gear shifting control process (such as shortening the gear shifting time, simplifying the control process, etc.).

[0064] In the original solution of the prior art, a regular oil drain hole 27 communicating with the piston cavity is provided in the clutch piston cylinder 1 of the wet clutch in the AT automatic transmission. Figure 8 The solution of the present invention mainly relates to the shift auxiliary control valve, and the structure of the clutch piston cylinder 1 is modified accordingly, while the other parts remain unchanged.

[0065] The AT automatic transmission used for testing has a total of 6 forward gears, 6 wet clutches and 6 proportional solenoid valves. Each gear requires two clutches to engage to form. Taking the control process of shifting from 2nd gear to 3rd gear as an example, 2nd gear requires clutches 1 and 5 to engage, and 3rd gear requires clutches 3 and 5 to engage. Therefore, the process of shifting from 2nd gear to 3rd gear requires clutch 1 to disengage and clutch 3 to engage to complete the gear shift. Therefore, the entire shifting process requires controlling the action (disengagement) of proportional solenoid valve No. 1 corresponding to clutch No. 1, and the action (engagement) of proportional solenoid valve No. 3 corresponding to clutch No. 3. Because the clutch part is a rotating component, it is impossible to install a sensor to collect the actual pressure data in the clutch oil chamber (i.e., the piston chamber, which is the third chamber 23 for the present invention). Therefore, in actual testing, a pressure sensor is usually installed at the proportional solenoid valve outlet pressure point to collect the pressure at the solenoid valve outlet, i.e., before entering the main oil channel 19 in the clutch drive shaft 20. Since there are oil channels and throttle holes between the clutch oil chamber and the solenoid valve outlet, according to the hydraulic pressure loss theory, the actual pressure in the clutch oil chamber (i.e., the piston chamber, which is the third chamber 23 for the present invention) is lower than the pressure at the collection point. Since it is impossible to measure it in practice, the pressure in the oil chamber is simulated and calculated using a simulation tool, and a comprehensive analysis is performed based on the actual test results.

[0066] Figure 9 The figure shows the proportional solenoid valve drive control parameters for a conventional wet clutch solution with a constant oil drain hole, resulting from calibration and commissioning. In the figure, clutch #1, which is to be disengaged, maintains a control current of 770mA from 0ms to 400ms, maintaining its engagement state. At 400ms, the current decreases directly from 770mA to 0mA, indicating that clutch #1 is disengaged at that time. Clutch No. 3, which needs to be engaged, maintains a control current of 500mA from 0ms to 400ms in the oil filling stage to eliminate the idle stroke. At 400ms, the current decreases from 500mA to 330mA, and then from 400ms to 1100ms, the current gradually increases from 330mA to 420mA, and the control current change rate is 0.13mA / ms. This process is used to control the clutch in the slipping stage to complete torque transmission and speed changes. From 1100ms to 1500ms, the current quickly increases from 420mA to 770mA, and the control current change rate is 0.875mA / ms. This process is used to control the clutch to quickly engage and complete the torque reserve.

[0067] Wet clutch solution with constant oil drain hole and Figure 9 The test results of the control parameters shown in the figure on the actual vehicle are as follows: Figure 10 As shown in the figure, the process of shifting from 2nd gear to 3rd gear is shown. Figure 9 The actual test curves collected by the control parameters shown. Figure 10The five curves in the middle represent the engine speed curve, input speed curve, output speed curve, clutch No. 1 oil pressure curve and clutch No. 3 oil pressure curve from top to bottom according to the leftmost end of the time axis, and the violent fluctuation in the middle section of the clutch No. 3 oil pressure curve is simulated to form a simulated oil pressure curve in the clutch No. 3 cavity composed of dots.

[0068] according to Figure 10 As shown in the figure, upon completion of the first stage of clutch 3 oil filling, the input speed dropped from 1155 rpm to 749 rpm in 208 ms, followed by a fluctuation of approximately 250 ms. The figure also shows slight fluctuations in the output speed, which manifests as a slight shift jerk in actual shift quality. The figure shows that the pressure at the solenoid valve outlet measured in the second stage ranged from 60-105 PSI, with a period of approximately 180 ms between 60-95 PSI and a sharp fluctuation of approximately 30 PSI. Simulations indicate that the theoretical pressure within the clutch oil chamber during this stage ranged from 80-100 PSI, showing no significant decrease compared to the measured pressure. This is attributed to the fact that during the first stage of oil filling, the entire clutch chamber is fully opened when the piston moves right. By the time the second stage begins, after eliminating the idle stroke, the entire chamber is already filled with oil, and the oil pressure within the chamber is close to that of the oil inlet passage. Through actual measurement and verification, the method to eliminate the shifting frustration is to adjust the initial oil pressure of the second stage, that is, the sliding stage. However, the minimum excitation current of the proportional solenoid valve to establish the oil pressure is 300~320mA. Figure 7 At the start of the intermediate slip phase, the control current for clutch No. 3 is reduced from 500mA to 330mA. 330mA is slightly greater than the proportional solenoid valve's excitation current to build pressure. In actual practice, if this current is reduced further, the oil pressure begins to fluctuate violently at the end of the oil filling phase, and the input speed begins to rise rapidly rather than fall. This phenomenon is known as power interruption. Analysis of the root causes revealed that, on the one hand, the proportional solenoid valve's excitation current to build oil pressure has a lower limit, and on the other hand, the constant oil drain hole continuously drains oil, preventing the clutch oil chamber from maintaining a stable flow rate, causing the oil pressure to fluctuate violently. Testing also confirmed that increasing the first-stage oil filling time increases the jerk (causing a significant increase in clutch oil chamber pressure), while decreasing the filling time results in a brief power interruption at the end of the filling phase. Therefore, the figure shows an acceptable control state after final commissioning and calibration, with slight shifting jerk. In addition, as shown in the figure, the separation of clutch No. 1 starts at 343.6s, drops to 20PSI at 343.7s, maintains for about 190ms, and drops to 0PSI at 343.9s, taking a total of 300ms. The oil pressure maintained at 20PSI indicates that the residual oil in the clutch oil chamber is not discharged quickly.

[0069] Figure 11 The figure shows the proportional solenoid valve drive control parameters, resulting from calibration and debugging, for the wet clutch solution employing the shift assist control valve of the present invention. In the figure, clutch No. 1, which requires disengagement, maintains a control current of 770 mA from 0ms to 200ms, maintaining its engagement state. At 200ms, the current decreases directly from 770 mA to 0 mA, representing clutch No. 1 disengagement at 200ms. Clutch No. 3, which requires engagement, maintains a control current of 500 mA from 0ms to 150ms during the oil filling phase to eliminate idle travel. From 150ms to 500ms, the current gradually increases from 500mA to 570mA at a rate of 0.2mA / ms, controlling the clutch in the slip phase to achieve torque transmission and speed change. From 650ms to 1000ms, the current rapidly increases from 570mA to 770mA at a rate of 0.57mA / ms, controlling the clutch to quickly engage and achieve torque reserve.

[0070] Wet clutch solution with shift assist control valve and Figure 11 The test results of the control parameters shown in the figure on the actual vehicle are as follows: Figure 12 shown.

[0071] Figure 12 The figure shows the process of shifting from 2nd gear to 3rd gear. Figure 11 The actual test curves collected by the control parameters shown. Figure 12 In the figure, the five curves represent the engine speed curve, input speed curve, output speed curve, clutch No. 1 oil pressure curve and clutch No. 3 oil pressure curve from top to bottom according to the leftmost end of the time axis, and the simulated oil pressure curve in the clutch cavity No. 3 composed of dots is formed by simulation in the middle section of the clutch No. 3 oil pressure curve.

[0072] Figure 12As shown in the figure, neither the input speed nor the output speed fluctuated during the second slip phase, demonstrating smooth, impactless shifting during actual testing. Comparing the pressure measured at the solenoid valve outlet of clutch No. 3 with the simulated oil chamber pressure, we can see that the actual oil filling time for this scheme is approximately 170ms. After completing the first phase and entering the second phase, the simulated oil pressure rapidly rises from 0 PSI to 60 PSI, then gradually rises to 85 PSI, completing torque transmission and speed change. According to the aforementioned operating principle of the shift assist valve scheme, in the first phase, no oil enters the third chamber 23, resulting in an oil pressure of 0 PSI. In the second phase, oil enters the third chamber 23 through the second orifice 11, creating a significant orifice throttling effect. This causes the oil pressure in the third chamber 23 to be significantly lower than the oil pressure at the solenoid valve outlet. This throttling effect controls the flow rate into the third chamber 23, ensuring a low and smooth oil pressure during the slip phase, ensuring a smooth shift. In addition, as shown in the figure, the separation of clutch No. 1 starts at 1692s and drops to 0PSI at 1692.15s, which takes a total of 150ms. During this process, there is no phenomenon of residual oil maintaining low oil pressure for a certain period of time as described in the previous case. This shows that in this solution, the oil can be discharged quickly when the clutch is separated, and the separation time is shortened.

[0073] According to the comparison of the above measured shift test results, the shift auxiliary control valve clutch scheme of the present invention is compared with the clutch scheme using a constant oil drain hole. During the shift process, the time for filling oil in the first stage to eliminate the idle stroke is shortened from 400ms to 170ms; during the second stage of slipping, the oil pressure in the third cavity 23 of the clutch can be controlled between 60-85PSI, which is 15-20PSI lower than the cavity pressure of 80-100PSI in the scheme using a constant oil drain hole, and is not limited by the lower limit of the proportional solenoid valve excitation current. The entire shift process time is reduced from 1500ms in the original scheme to 1000ms. After a lot of debugging and calibration, the clutch scheme using a constant oil drain hole still has slight shifting jerks. The scheme of the present invention has smooth shifting without impact and simple control parameters.

[0074] Overall performance evaluation: The present invention's shifting solution resulted in smooth, impact-free shifting, significantly shortening the oil filling and disengagement phases during the shifting process, thereby shortening the overall shifting time. Compared to the original solution with a constant oil drain hole, which relied on the proportional solenoid valve's output current to control the engagement process, the present invention's solution utilizes the shift assist valve's segmented automatic adjustment during the control process, significantly reducing reliance on the proportional solenoid valve's current output control. This, in turn, further expands the solenoid valve's adjustable range and effectiveness, reducing the difficulty of shift quality calibration and debugging.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation methods of the present invention can be modified or replaced with equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A segmented, self-adjusting wet clutch comprising a transmission shaft and a clutch piston cylinder, wherein the clutch piston cylinder is fixed to the transmission shaft and a piston is disposed in a piston chamber of the clutch piston cylinder. The piston's active surface is radially divided into an inner active surface and an outer active surface, and is arranged in a stepped manner. The invention is characterized in that: A baffle ring is provided in the clutch piston cylinder, which divides the piston cavity into a first cavity and a third cavity. The first cavity is connected to the main oil channel in the transmission shaft. The inner working surface is located in the first cavity, and the outer working surface is located in the third cavity. A radially extending mounting hole is further provided in the clutch piston cylinder. The mounting hole is a through hole. A plurality of through holes are provided on the cylinder wall between the mounting hole and the piston cavity. The plurality of through holes are respectively a first throttle hole, a second throttle hole, a third throttle hole and a second oil drain hole. A first oil drain hole that is always connected to the mounting hole is also provided on the cylinder wall of the clutch piston cylinder. The first throttle hole is connected to the first cavity, and the second throttle hole, the third throttle hole and the second oil drain hole are all connected to the third cavity. A shift auxiliary control valve is provided in the mounting hole, comprising a base, a valve piston, a valve stem and a valve sleeve arranged in sequence. The base is fixed in the mounting hole and is provided with a through-hole. The space between the base and the transmission shaft and the hole together form a second cavity. The second cavity is always connected to the first cavity through the first throttle hole. The valve stem is relatively slidably provided in the valve sleeve, the proximal end of the valve stem is inserted into the valve piston, and the distal end of the valve sleeve is axially positioned in the mounting hole. A valve spring is provided outside the valve sleeve, and the two ends of the valve spring respectively press against the valve sleeve and the valve piston. In the initial state of the wet clutch, the valve acting surface of the valve piston forms a blockage for the channel in the base, the side surface of the valve piston forms a blockage for the second throttle hole, the first slot hole set on the valve piston is aligned with the third throttle hole, and the second slot hole set on the valve sleeve is aligned with the second oil drain hole and avoids the valve stem.

2. The segmented self-adjusting wet clutch according to claim 1, characterized in that: The aperture of the second throttle hole is smaller than that of the first throttle hole, and through the throttling effect of the second throttle hole, the oil pressure in the second cavity pushes the valve piston to move and can block the third throttle hole; the aperture of the third throttle hole is larger than that of the second throttle hole.

3. The segmented self-adjusting wet clutch according to claim 1, characterized in that: The valve piston is a cylindrical structure with one end open, the closed end of which is the valve action surface, and the open end is used to receive the insertion of the valve stem.

4. The segmented self-adjusting wet clutch according to claim 3, characterized in that: The longitudinal section of the valve stem is T-shaped, and its T-shaped head is inserted into the valve piston through the open end of the valve piston, and the outer diameter of the T-shaped head matches the inner diameter of the valve piston, and the proximal end of the valve spring is pressed against the T-shaped head.

5. The segmented self-adjusting wet clutch according to claim 1, characterized in that: The longitudinal section of the valve sleeve is T-shaped, and its T-shaped head is away from the valve piston and is axially fixed in the mounting hole of the clutch piston cylinder by a retaining ring. The central hole of the valve sleeve that accommodates the valve stem is a through hole; the distal end of the valve spring is pressed against the T-shaped head.

6. The segmented self-adjusting wet clutch according to claim 5, characterized in that: A gasket is further provided outside the valve sleeve, and the distal end of the valve spring rests on the gasket.

7. The segmented self-adjusting wet clutch according to claim 1, characterized in that: The base is provided with a fixing hole, and the fixing piece passes through the fixing hole to fix the base in the installation hole.

8. The segmented self-adjusting wet clutch according to claim 1, characterized in that: An annular groove communicating with the third throttle hole is provided on the inner wall of the mounting hole.

9. The segmented self-adjusting wet clutch according to any one of claims 1 to 8, characterized in that: The engagement process of a wet clutch consists of the following three stages: (1) First stage: The oil enters the first cavity through the main oil channel. One path of oil acts on the inner working surface of the piston, forming a thrust F1, pushing the piston to move and eliminating the idle stroke between the piston and the first steel plate in the clutch piston cylinder; the other path of oil enters the second cavity through the first throttle hole, forming a thrust F2 acting on the valve piston, and F2 is smaller than the initial elastic force of the valve spring; (2) Second stage: The oil pressure increases, making the thrust F2 greater than the initial elastic force of the valve spring, pushing the valve piston to move. A portion of the oil in the second chamber enters the third chamber through the second throttle hole, acting on the outer surface of the piston to form a thrust F3. Through the action of the second throttle hole, the side of the valve piston can completely cover the third throttle hole, and the valve stem moving with the valve piston completely covers the second oil drain hole. (3) The third stage: The oil pressure continues to increase, pushing the valve piston to continue moving, so that the third throttle hole connects the second cavity and the third cavity. The oil pushes the piston to quickly press the friction plate and steel plate of the wet clutch to achieve full engagement.

10. The segmented self-adjusting wet clutch according to any one of claims 1 to 8, characterized in that: The disengagement process of the wet clutch consists of the following two stages: (1) First stage: After the proportional solenoid valve in the wet clutch is powered off, the oil in the third chamber enters the second chamber through the third throttle hole and the second throttle hole, then enters the first chamber through the first throttle hole, and finally is discharged into the oil tank through the main oil channel from the drain port of the proportional solenoid valve; (2) The second stage: As the oil flows out, the pressure in the third cavity, the second cavity and the first cavity also decreases. When the thrust F2 in the second cavity is less than the elastic force of the valve spring, the valve spring pushes the valve piston to reset, and the valve stem slides along the valve sleeve; when the second oil drain hole is no longer blocked by the valve stem, part of the oil remaining in the third cavity due to the centrifugal force of the clutch rotation will be discharged into the oil tank through the second oil drain hole, the second slot hole and the center hole inside the valve sleeve; part of the residual oil in the third cavity near the transmission shaft flows into the valve spring gap through the third throttle hole and the first slot hole on the valve piston, and is finally discharged into the oil tank through the first oil drain hole.

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