Vehicle control device and control method

Abstract

To suppress a seizing of friction panels when a friction fastening element is in a released state.SOLUTION: A vehicle V includes: a drive source 50; and a moisture-type friction fastening element 10 in which a rotation force from the drive source 50 is input. The friction fastening element 10 includes a first friction panel 14 and a second friction panel 24 that come into a fastened state and a released state. In the released state, when a rotational speed difference between the first friction panel 14 and the second friction panel 24 increases from a state of less than a first threshold value to be a second threshold value or more which is larger than the first threshold value, a rotational speed control is performed to reduce the rotation speed of the first friction panel 14 to decrease the rotation speed difference. When the rotation speed control is executed in the released state, the rotation speed control is terminated when the rotation speed difference comes to less than the first threshold value.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The technology disclosed herein belongs to the technical field of vehicle control devices and control methods. [Background technology]

[0002] Conventionally, a friction fastening element has been known that transmits power from a cylindrical outer member to an outer member by fastening together a plurality of outer friction plates engaged with the outer member and a plurality of inner friction plates engaged with an inner member disposed inside the outer member.

[0003] The hydraulic clutch actuation device disclosed in Patent Document 1 is equipped with a pressure regulating member that regulates the pressure of hydraulic oil to a commanded hydraulic pressure. The pressure regulating member separates the discharged oil into hydraulic oil and lubricating oil to be supplied to the friction engagement part, and is capable of changing the flow path area that determines the oil supply flow rate of the lubricating oil. The control device controls the pressure regulating member so that, when the friction engagement part is engaged, the flow path area becomes a set area that is variably set based on the rotational speed difference between the rotational speed of the first friction engagement element (first friction plate) and the rotational speed of the second friction engagement element (second friction plate), and controls the hydraulic pump so that, when the friction engagement part is engaged, the hydraulic oil is regulated to the commanded hydraulic pressure by the pressure regulating member whose flow path area is the set area. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-149458 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the frictional engagement elements are in a disengaged state, if the first friction plate rotates at high speed and the difference in rotation speed between the first friction plate and the second friction plate increases, the second friction plate may vibrate. If the second friction plate vibrates, the second friction plate may come into contact with the first friction plate, potentially causing seizure. If the control described in Patent Document 1 is applied when the frictional engagement elements are in a disengaged state, the amount of lubricant supplied increases as the difference in rotation speed increases. Therefore, when the first friction plate rotates at high speed, it is expected that the lubricant will reduce the vibration of the second friction plate.

[0006] However, after careful consideration, the inventors of the present application found that the rotational speed difference at which the second friction plate starts to vibrate is different from the rotational speed difference at which the second friction plate starts to vibrate and then stops vibrating.With the control described in Patent Document 1, when the second friction plate is vibrating, there is a risk that the lubricating oil will be insufficient, and the vibration of the second friction plate will not be sufficiently suppressed.

[0007] The technology disclosed herein has been made in view of the above points, and its purpose is to suppress seizure between friction plates when the frictional engagement element is in a released state. [Means for solving the problem]

[0008] In order to solve the above problem, a first aspect of the technology disclosed herein is directed to a vehicle control device, and includes a drive source, a wet friction engagement element to which rotational power from the drive source is input, and a control unit that controls the drive source. The friction engagement elements include first and second friction plates that are in an engaged state and a disengaged state, a first member that engages with the first friction plate and rotates together with the first friction plate by the rotational power from the drive source, and a second member that engages with the second friction plate and receives rotational power from the first member in the engaged state. The control unit executes rotation speed reduction control to reduce the rotation speed difference by reducing the rotation speed of the first friction plate when a rotation speed difference between the first and second friction plates increases from a state where it is less than a first threshold to a second threshold value or greater that the first threshold value, and terminates the rotation speed reduction control in the disengaged state when the rotation speed difference becomes less than the first threshold value after the rotation speed reduction control has been executed.

[0009] In the first aspect, even if the rotation speed difference becomes less than the second threshold after the rotation speed reduction control is executed, the rotation speed reduction control is executed until the rotation speed difference becomes less than the first threshold. Therefore, the rotation speed difference can be quickly reduced to a rotation speed difference that makes it difficult for the second friction plate to vibrate, and vibration of the second friction plate can be efficiently suppressed. Therefore, the control device can suppress seizure between the friction plates when the frictional engagement element is in the disengaged state.

[0010] A second aspect of the technology disclosed herein is the first aspect, wherein the control unit reduces the rotation speed of the first friction plate by reducing the output of the drive source during the rotation speed suppression control.

[0011] In the second aspect, by reducing the output of the drive source, the input rotation speed to the frictional engagement element is reduced, thereby reducing the rotation speed of the first friction plate, which allows the control device to suppress seizure between the friction plates when the frictional engagement element is in the disengaged state.

[0012] A third aspect of the technology disclosed herein is the second aspect, wherein the frictional engagement element is part of an automatic transmission that shifts the rotational power of the drive source, and the control unit controls the automatic transmission and, when the rotation speed difference increases from a state where it is less than the first threshold and becomes equal to or greater than a third threshold that is greater than the first threshold and less than the second threshold, upshifts the automatic transmission, and, after upshifting the automatic transmission, reduces the output of the drive source when the rotation speed difference exceeds the third threshold and becomes equal to or greater than the second threshold.

[0013] In the third aspect, the automatic transmission is shifted up before the rotation speed difference reaches the first threshold, thereby reducing the rotation speed of the first friction plate. This prevents the rotation speed difference from reaching the second threshold, thereby preventing the second friction plate from starting to vibrate. As a result, the control device can prevent the friction plates from seizing together when the frictional engagement element is in a disengaged state.

[0014] A fourth aspect of the technology disclosed herein is the second aspect, wherein the frictional engagement element is part of an automatic transmission that changes the rotational power of the drive source, and the control unit controls the automatic transmission and, in the rotation speed suppression control, reduces the output of the drive source and upshifts the automatic transmission to reduce the rotation speed of the first friction plate.

[0015] In the fourth aspect, the rotation speed of the first friction plate is reduced by upshifting the automatic transmission, so the rotation speed of the first friction plate can be reduced while suppressing a decrease in vehicle speed. This allows the control device to suppress seizure between the friction plates while suppressing an impact on the driving feel when the frictional engagement element is in a disengaged state.

[0016] A fifth aspect of the technology disclosed herein is the second aspect, wherein the control unit prohibits the rotation speed suppression control when the temperature of the frictional engagement element is lower than a predetermined temperature.

[0017] In the fifth aspect, when the temperature of the frictional engagement element is low and the friction plates are unlikely to seize together, the rotation speed suppression control is prohibited, thereby reducing the impact on the driving feel.

[0018] A sixth aspect of the technology disclosed herein is the second aspect, wherein when the temperature of the frictional engagement element is below a predetermined temperature, the control unit reduces the rate at which the output of the drive source is reduced in the rotation speed suppression control compared to when the temperature of the frictional engagement element is equal to or higher than the predetermined temperature.

[0019] In the sixth aspect, when the temperature of the frictional engagement element is low and the friction plates are unlikely to seize together, the output of the drive source is reduced but the rate at which it is reduced is slowed, thereby minimizing the impact on the driving feel.

[0020] A seventh aspect of the technology disclosed herein is any one of the first to sixth aspects, wherein the second threshold value is a value set in consideration of the viscosity of the lubricating oil supplied between the first friction plate and the second friction plate, the gap between the first friction plate and the second friction plate, and the static friction between the second friction plate and the second member.

[0021] In the seventh aspect, the rotational speed difference at which the second friction plate starts to vibrate is set with high precision, thereby enabling the control device to suppress deterioration of energy consumption when the frictional engagement element is in a disengaged state.

[0022] An eighth aspect of the technology disclosed herein is any one of the first to sixth aspects, wherein the first threshold value is a value set in consideration of the viscosity of the lubricating oil supplied between the first friction plate and the second friction plate, the gap between the first friction plate and the second friction plate, and the dynamic friction between the second friction plate and the second member.

[0023] In the eighth aspect, the rotational speed difference at which the second friction plate is less likely to vibrate is set with high precision, thereby enabling the control device to suppress deterioration of energy consumption when the frictional engagement element is in a disengaged state.

[0024] A ninth aspect of the technology disclosed herein is any one of the first to fourth aspects, further comprising a rotation speed difference calculation unit that detects the rotation speed difference, wherein the frictional engagement element is part of an automatic transmission, and the rotation speed difference calculation unit calculates the rotation speed difference based on the gear position of the automatic transmission and the input rotation speed or the output rotation speed of the automatic transmission.

[0025] In the ninth aspect, the configuration of the control device can be made as compact as possible.

[0026] A tenth aspect of the technology disclosed herein is directed to a method for controlling a vehicle, the vehicle including a drive source and a wet friction engagement element to which rotational power from the drive source is input, the friction engagement element having first and second friction plates that are in an engaged state and a disengaged state, a first member that engages with the first friction plate and rotates together with the first friction plate by the rotational power from the drive source, and a second member that engages with the second friction plate and to which rotational power is transmitted from the first member in the engaged state, the method comprising the steps of: executing rotation speed suppression control to reduce the rotation speed difference by reducing the rotation speed of the first friction plate when a rotation speed difference between the first and second friction plates increases from a state where it is less than a first threshold value to a second threshold value or greater that is greater than the first threshold value in the disengaged state; and terminating the rotation speed suppression control when the rotation speed difference becomes less than the first threshold value while the rotation speed suppression control is being executed in the disengaged state. [Effects of the Invention]

[0027] As described above, according to the technique disclosed herein, the control device can suppress seizure between the friction plates when the frictional engagement element is in a released state. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a vehicle controlled by a control device according to a first exemplary embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of an automatic transmission. [Figure 3] Figure 3 is an automatic transmission engagement table. [Figure 4] FIG. 4 is a cross-sectional view of a frictional fastening element. [Figure 5] FIG. 5 is a block diagram showing a control system for supplying lubricating oil to frictional engagement elements. [Figure 6] FIG. 6 is a graph showing the relationship between the rotation speed difference and the drag resistance. [Figure 7] FIG. 7 is a diagram illustrating the conditions under which the second friction plate vibrates. [Figure 8] FIG. 8 is a map showing an example of the cooling characteristics of the temperatures of the frictional engagement elements. [Figure 9] FIG. 9 is a flowchart showing the processing operations in vibration suppression control. [Figure 10] FIG. 10 is a time chart showing the relationship between the rotation speed difference, the gear position, and the engine rotation speed in vibration suppression control. [Figure 11] FIG. 11 is a flowchart showing the processing operation in vibration suppression control of the control device according to the second embodiment. [Figure 12] FIG. 12 is a flowchart showing a processing operation in vibration suppression control of the control device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the first exemplary embodiment will be described in detail with reference to the drawings.

[0030] First Embodiment (1) Overall vehicle configuration FIG. 1 shows an automobile V (an example of a vehicle) to which the disclosed technology is applied. The automobile V is a hybrid automobile that can run on electric power. The automobile V has a total of four wheels: front wheels FW and rear wheels RW.

[0031] The automobile V is equipped with a drive source 50, which includes an engine 51 and a motor 52 that generate driving force for the automobile V. These work together to drive the rear wheels RW, causing the automobile V to move. The automobile V is a rear-wheel drive vehicle. The motor 52 is used not only as a drive source but also as a generator during regeneration.

[0032] The automobile V is equipped with a high-voltage battery 42 having a rated voltage of 50 V or less. The motor 52 is driven by power supplied from the high-voltage battery 42, mainly assisting the engine 51 (a so-called mild hybrid vehicle). The automobile V may also be a so-called plug-in hybrid vehicle that can receive power from an external power source.

[0033] In the case of this automobile V, the engine 51 is disposed at the front of the body, and the drive wheels are disposed at the rear of the body. In other words, this automobile V is a so-called FR vehicle.

[0034] The automobile V is equipped with an automatic transmission 1 that accelerates or decelerates the rotational power output from a drive source 50. The automatic transmission 1 is disposed behind a motor 52.

[0035] The automobile V is equipped with a propeller shaft 7, a differential gear 9, and a drive shaft DS in order to transmit the rotational power changed by the automatic transmission 1 to the rear wheels RW. The rotational power output from the automatic transmission 1 is input to the differential gear 9 via the propeller shaft 7. The differential gear 9 distributes the input rotational power to a pair of drive shafts DS. The distributed rotational power is transmitted to each rear wheel RW via each drive shaft DS.

[0036] (2) Drive source The engine 51 is, for example, an internal combustion engine that burns fossil fuel. The engine 51 is also a so-called four-stroke engine that generates rotational power by repeating cycles of intake, compression, expansion, and exhaust. There are various types and forms of the engine 51, such as spark ignition engines and compression ignition engines, but the technology disclosed herein is not particularly limited to the type or form of the engine 51.

[0037] In this automobile V, engine 51 is disposed in the approximate center in the width direction of the vehicle, with crankshaft 51a that outputs rotational power facing the front-to-rear direction of the vehicle body. Automobile V is equipped with various devices and mechanisms associated with engine 51, such as an intake system, an exhaust system, and a fuel supply system.

[0038] The motor 52 is a permanent magnet synchronous motor driven by three-phase AC. The motor 52 is disposed in series with the rear side of the engine 51 via a K0 clutch 53. The motor 52 is also disposed in series with the front side of the automatic transmission 1.

[0039] The K0 clutch 53 is disposed between the crankshaft 51a and the front end of the motor shaft 52a of the motor 52. The K0 clutch 53 switches between a state in which the crankshaft 51a and the motor shaft 52a are connected and a state in which the crankshaft 51a and the motor shaft 52a are separated.

[0040] The rear end of the motor shaft 52a is connected to the input shaft 4 of the automatic transmission 1. In other words, the engine 51 is connected to the automatic transmission 1 via the K0 clutch 53 and the motor shaft 52a. The engine 51 is separated from the automatic transmission 1 by disengaging the K0 clutch 53.

[0041] While the vehicle V is traveling, the K0 clutch 53 is switched between an engaged state and a disengaged state. For example, when the vehicle V is decelerating, the K0 clutch 53 may be disengaged and regeneration may be performed with the engine 51 disconnected.

[0042] The motor 52 is connected to a high-voltage battery 42 via an inverter 41 and a high-voltage cable 45. In the case of this automobile V, the high-voltage battery 42 is a DC battery with a rated voltage of 50 V or less, specifically 48 V.

[0043] The high-voltage battery 42 supplies high-voltage DC power to the inverter 41. The inverter 41 converts the DC power into three-phase AC and supplies it to the motor 52. This causes the motor 52 to rotate. The motor 52 also supplies regenerative energy to the high-voltage battery 42.

[0044] The high-voltage battery 42 is also connected to a DC-DC converter 43 via a high-voltage cable 45. The DC-DC converter 43 converts high-voltage DC power of 48 V into low-voltage DC power of 12 V and outputs it. The output side of the DC-DC converter 43 is connected to a low-voltage battery 44 (a so-called lead-acid battery) via a low-voltage cable 46. The low-voltage battery 44 is connected to various electrical components via the low-voltage cable 46.

[0045] (3) Automatic transmission The automatic transmission 1 is a hydraulically controlled multi-stage automatic transmission (so-called AT) and includes a housing 2, an input shaft 4, an output shaft 5, a speed change device 6, and a connecting / disconnecting device 8.

[0046] The housing 2 forms the outer shell of the automatic transmission 1. The housing 2 houses the connecting / disconnecting device 8 and the transmission device 6, and supports the input shaft 4 and the output shaft 5 in a rotatable state.

[0047] The input shaft 4 is disposed at the front end of the automatic transmission 1. The input shaft 4 is connected to a motor shaft 52a. The output shaft 5 is disposed at the rear end of the automatic transmission 1. The output shaft 5 rotates independently of the input shaft 4.

[0048] The interrupter 8 is connected to the input shaft 4. The interrupter 8 is configured to input the rotational power output by the drive source 50 to the transmission 6 as needed. The interrupter 8 is, for example, a torque converter.

[0049] The transmission 6 is disposed around the input shaft 4 and the output shaft 5. The transmission 6 switches the rotation speed of the rotational power input from the input shaft 4 via the connecting / disconnecting device 8 and transmits it to the output shaft 5.

[0050] (3-1) Transmission As shown in FIG. 2, the transmission 6 has a first planetary gear set PG1 (hereinafter referred to as the first gear set PG1), a second planetary gear set PG2 (hereinafter referred to as the second gear set PG2), a third planetary gear set PG3 (hereinafter referred to as the third gear set PG3), and a fourth planetary gear set PG4 (hereinafter referred to as the fourth gear set PG4), which are arranged in the axial direction of the input shaft 4. The first gear set PG1, the second gear set PG2, the third gear set PG3, and the fourth gear set PG4 are arranged in this order from the front side (the drive source 50 side). Multiple power transmission paths are formed from the input shaft 4 to the output shaft 5. The first to fourth gear sets PG1 to PG4 are arranged coaxially with the input shaft 4 and the output shaft 5.

[0051] The first gear set PG1 has a first sun gear S1, a first ring gear R1, and a first carrier C1 as rotating elements. The first gear set PG1 is a single-pinion type, and a plurality of pinions Pi1 supported by the first carrier C1 and arranged at intervals in the circumferential direction of the first gear set PG1 are meshed with both the first sun gear S1 and the first ring gear R1.

[0052] The second gear set PG2 has a second sun gear S2, a second ring gear R2, and a second carrier C2 as rotating elements. The second gear set PG2 is a single-pinion type, and a plurality of pinions Pi2 supported by the second carrier C2 and arranged at intervals in the circumferential direction of the second gear set PG2 are meshed with both the second sun gear S2 and the second ring gear R2.

[0053] The third gear set PG3 has a third sun gear S3, a third ring gear R3, and a third carrier C3 as rotating elements. The third gear set PG3 is a single-pinion type, and a plurality of pinions Pi3 supported by the third carrier C3 and arranged at intervals in the circumferential direction of the third gear set PG3 are meshed with both the third sun gear S3 and the third ring gear R3.

[0054] The fourth gear set PG4 has a fourth sun gear S4, a fourth ring gear R4, and a fourth carrier C4 as rotating elements. The fourth gear set PG4 is a single-pinion type, and multiple pinions Pi4 are supported by the fourth carrier C4 and arranged at intervals in the circumferential direction of the fourth gear set PG4. The pinions Pi4 are meshed with both the fourth sun gear S4 and the fourth ring gear R4.

[0055] The first sun gear S1 of the first gear set PG1 is divided into two parts in the axial direction of the input shaft 4: a front first sun gear S1a disposed relatively forward and a rear first sun gear S1b disposed relatively rearward. In other words, the first gear set PG1 is a double-sun gear type gear set. The front and rear first sun gears S1a, S1b have the same number of teeth and are engaged with the pinion Pi1 supported by the first carrier C1. Therefore, the rotation speeds of the front and rear first sun gears S1a, S1b are always equal. In other words, the front and rear first sun gears S1a, S1b always rotate at the same rotational speed, and when rotation of one gear stops, rotation of the other gear also stops.

[0056] The first sun gear S1 (strictly speaking, the rear first sun gear S1b) and the fourth sun gear S4 are always connected, the first ring gear R1 and the second sun gear S2 are always connected, the second carrier C2 and the fourth carrier C4 are always connected, and the third carrier C3 and the fourth ring gear R4 are always connected. In addition, the input shaft 4 is always connected to the first carrier C1, and the output shaft 5 is always connected to the fourth carrier C4.

[0057] The transmission 6 also has a plurality of frictional engagement elements 10 (first clutch CL1, second clutch CL2, third clutch CL3, first brake BR1, and second brake BR2) for selecting one of a plurality of power transmission paths formed by the first to fourth gear sets PG1 to PG4 and switching the power transmission path.

[0058] The first clutch CL1 is configured to connect and disconnect the input shaft 4 and the first carrier C1 to and from the third sun gear S3. The first clutch CL1 is disposed in front of the first gear set PG1.

[0059] The second clutch CL2 is configured to connect and disconnect the first ring gear R1 and the second sun gear S2 from the third sun gear S3. The second clutch CL2 is disposed in front of the first clutch CL1.

[0060] The third clutch CL3 is configured to connect and disconnect the second ring gear R2 and the third sun gear S3. The third clutch CL3 is disposed in front of the second clutch CL2.

[0061] The first brake BR1 is configured to connect and disconnect the first sun gear S1 (strictly speaking, the front first sun gear S1a) and the housing 2. The first brake BR1 is disposed in front of the third clutch CL3 and near the housing 2. When the first brake BR1 is engaged, the first sun gear S1 is fixed to the housing 2.

[0062] The second brake BR2 is configured to connect and disconnect the third ring gear R3 and the housing 2. When the second brake BR2 is engaged, the third ring gear R3 is fixed to the housing 2.

[0063] 3 shows an engagement table for the automatic transmission 1. Circles in the table indicate engagement. As mentioned above, this automatic transmission 1 incorporates three clutches, consisting of a first clutch CL1, a second clutch CL2, and a third clutch CL3, as frictional engagement elements 10, and two brakes, consisting of a first brake BR1 and a second brake BR2.

[0064] The automatic transmission 1 uses hydraulic control to selectively engage three elements from among the first clutch CL1, second clutch CL2, third clutch CL3, first brake BR1, and second brake BR2, thereby switching the gears of the automatic transmission between forward gears (1st to 8th gears) and reverse gear (reverse gear).

[0065] Specifically, first gear is established by engaging first clutch CL1, first brake BR1, and second brake BR2. Second gear is established by engaging second clutch CL2, first brake BR1, and second brake BR2. Third gear is established by engaging first clutch CL1, second clutch CL2, and second brake BR2. Fourth gear is established by engaging second clutch CL2, third clutch CL3, and second brake BR2. Fifth gear is established by engaging first clutch CL1, third clutch CL3, and second brake BR2. Sixth gear is established by engaging first clutch CL1, second clutch CL2, and third clutch CL3. Seventh gear is established by engaging first clutch CL1, third clutch CL3, and first brake BR1. Eighth gear is established by engaging second clutch CL2, third clutch CL3, and first brake BR1. Reverse gear is established by engaging third clutch CL3, first brake BR1, and second brake BR2.

[0066] For example, when shifting up from first gear, the gear changes from first gear to second gear by engaging second clutch CL2 instead of first clutch CL1. The gear changes from second gear to third gear by engaging first clutch CL1 instead of first brake BR1. The gear changes from third gear to fourth gear by engaging third clutch CL3 instead of first clutch CL1. When shifting down, the procedure is reversed from that of shifting up.

[0067] (3-2) Frictional fastening element The frictional engagement elements 10 will be described in detail using the first brake BR1 as an example. The clutches CR1 to CR3 and the brakes BR1 and BR2 are functionally different but structurally almost the same.

[0068] 4, the frictional engagement element 10 includes a plurality of first friction plates 14, a plurality of second friction plates 24, a hub 12 that engages with the first friction plates 14 and rotates together with the first friction plates 14, and a drum 22 that engages with the second friction plates 24 and to which rotational power is transmitted from the hub 12. The frictional engagement element 10 also includes a piston 30 that is axially movably disposed on one axial side of the second friction plates 24, a cover member 32 that is attached to the end face of the drum 22 on the piston 30 side so as to cover the piston 30, and an end plate 34 that is disposed on the other axial side of the second friction plates 24. The first friction plates 14 and the second friction plates 24 may be collectively referred to simply as "friction plates."

[0069] (3-2-1) Hub, Drum As shown in Fig. 4, the hub 12 is disposed inside the drum 22 and is rotatable relative to the drum 22. The hub 12 is a cylindrical member. The input shaft 4 passes through the inside of the hub 12. A plurality of axially extending internal spline teeth 16 are formed on the outer circumferential surface of the hub 12 at intervals in the circumferential direction.

[0070] The drum 22 is a bottomed cylindrical member having a cylindrical peripheral wall portion 22a and a disk-shaped bottom wall portion 22b, through the center of which the input shaft 4 passes. The drum 22 is disposed coaxially with the input shaft 4 inside the housing 2 and is fixed to the housing 2. The input shaft 4 passes through the drum 22 along its central axis. Furthermore, the drum 22 and the hub 12 are disposed concentrically. The drum 22 supports the hub 12 so that the hub 12 can rotate about its cylindrical axis. Furthermore, on the inner peripheral surface of the drum 22, external spline teeth 26 extending in the axial direction of the drum 22 are formed in a row spaced apart circumferentially.

[0071] As shown in FIG. 4 , the outer peripheral surface of the hub 12 and the inner peripheral surface of the drum 22 face each other in the radial direction. An annular space is formed between the outer peripheral surface of the hub 12 and the inner peripheral surface of the drum 22, serving as a plate accommodating chamber 40. When the automatic transmission 1 is in operation, lubricating oil (ATF: Automatic Transmission Fluid) is circulated and supplied to the plate accommodating chamber 40 from a lubrication device 36, which is composed of an oil pump, a flow control valve, and the like. The lubrication device 36 is provided in the automatic transmission 1. The lubrication device 36 introduces ATF into the plate accommodating chamber 40 through an oil introduction passage 36a formed inside the hub 12 and an oil supply hole 12a provided to communicate the oil introduction passage 36a with the outer periphery of the hub 12. The ATF that has flowed into the plate accommodating chamber 40 flows out from an oil drain hole 22c provided to communicate the plate accommodating chamber 40 with the outer periphery of the drum 22. The ATF flowing out of the drum 22 is returned to the lubrication device 36 through an oil return passage 36b formed inside the housing 2. In this way, the friction engagement element 10 is a wet friction engagement element in which the ATF is circulated and supplied.

[0072] (3-2-2) 1st friction plate, 2nd friction plate 4, the first friction plates 14 are annular plate members made of metal. The first friction plates 14 are arranged on the outer periphery of the hub 12 and are aligned in the axial direction.

[0073] A plurality of internal spline grooves 15 are formed at intervals in the circumferential direction on the inner peripheral edge of each first friction plate 14. The internal spline grooves 15 of each first friction plate 14 engage with internal spline teeth 16 of the hub 12. In other words, each first friction plate 14 is spline-engaged with the outer periphery of the hub 12. As a result, each first friction plate 14 is disposed on the outer periphery of the hub 12 so as to be slidable in the axial direction, and is prevented from rotating relative to the hub 12.

[0074] The second friction plates 24 are annular plate members made of metal and thicker than the first friction plates 14. The second friction plates 24 are arranged side by side in the axial direction inside the drum 22. Each second friction plate 24 is arranged between each first friction plate 14. Specifically, the first friction plates 14 and the second friction plates 24 are arranged alternately in the axial direction inside the drum 22.

[0075] Each second friction plate 24 has a plurality of external spline grooves 25 formed at intervals in the circumferential direction on its outer circumferential edge. The external spline grooves 25 of each second friction plate 24 engage with external spline teeth 26 formed on the inner circumferential portion of the drum 22. In other words, each second friction plate 24 is spline-engaged with the inner circumferential portion of the drum 22. As a result, each second friction plate 24 is disposed on the inner circumferential portion of the drum 22 so as to be slidable in the axial direction, and is prevented from rotating relative to the drum 22.

[0076] 4, a ring groove extending in the circumferential direction is formed in the inner peripheral portion of the drum 22 on the other axial side of the end plate 34. A resilient, arc-shaped snap ring 23 is fitted into the ring groove. Fitting the snap ring 23 into the ring groove prevents the end plate 34 from moving axially to the other side.

[0077] As shown in FIG. 4 , the piston 30 is disposed inside the drum 22 and is movable in the axial direction of the drum 22. By sliding the piston 30 in the axial direction, the second friction plates 24 and the first friction plates 14 are moved axially, thereby switching the frictional engagement element 10 between an engaged state and a released state. Specifically, when the piston 30 is moved from one side to the other in the axial direction in the released state, the first friction plates 14 and the second friction plates 24 come into close contact with each other in the axial direction, and the frictional engagement element 10 is switched to the engaged state. On the other hand, when the piston 30 is moved from one side to the other in the axial direction in the engaged state, the first friction plates 14 and the second friction plates 24 move away from each other in the axial direction, and the frictional engagement element 10 is switched to the released state. When the frictional engagement element 10 is in the engaged state, a braking force is applied to the hub 12, and rotation of the hub 12 is stopped. On the other hand, when the frictional engagement element 10 is in the released state, rotation of the hub 12 relative to the drum 22 is permitted.

[0078] (3-2-3) Piston The piston 30 is integrally formed of a pressing portion 30a, an operating portion 30b, and the like.

[0079] The pressing portion 30a is located in the plate accommodating chamber 40, and is arranged further axially to one side than the friction plates. The pressing portion 30a is arranged to face the second friction plate 24, which is located furthest axially to one side. On the other hand, the operating portion 30b is located inside the hub 12, and is arranged between the spring 31 provided on the input side and the hydraulic chamber 38 provided on one axial side. The hydraulic chamber 38 is partitioned liquid-tightly by the operating portion 30b.

[0080] The actuating part 30b is biased toward the output side by the elastic force of the spring 31. Pressurized oil is supplied to or discharged from a hydraulic pump (not shown) to the hydraulic chamber 38 as needed, causing hydraulic pressure to act on the actuating part 30b, causing the actuating part 30b to move in the axial direction.

[0081] When pressure oil is supplied to the hydraulic chamber 38, the operating part 30b slides to the other side in the axial direction against the elastic force of the spring 31. When pressure oil is discharged from the hydraulic chamber 38, the operating part 30b slides to one side in the axial direction due to the elastic force of the spring 31.

[0082] As the actuating portion 30b moves due to this hydraulic control, the pressing portion 30a moves axially within the plate accommodating chamber 40, advancing and retreating to one side and the other side in the axial direction. When pressure oil is supplied to the hydraulic chamber 38, the actuating portion 30b moves to the other side in the axial direction, and the pressing portion 30a moves toward the other side in the axial direction, bringing the first friction plates 14 and the second friction plates 24 into close contact with each other. This places the frictional engagement element 10 in an engaged state. On the other hand, when oil is discharged from the hydraulic chamber 38, the actuating portion 30b moves to one side in the axial direction, and the pressing portion 30a moves toward the other side in the axial direction, separating the first friction plates 14 and the second friction plates 24. This places the frictional engagement element 10 in a released state.

[0083] (4) Lubrication system control system As shown in FIG. 5, the control device of the automobile V includes an ECU (Electrical Control Unit) 100 for controlling the drive source 50 and the automatic transmission 1. The ECU 100 is a controller based on a well-known microcomputer and includes a central processing unit (CPU), a memory, and an interface (I / F) circuit. The CPU executes programs. The memory is configured, for example, with a random access memory (RAM) or a read-only memory (ROM) and stores programs and data. The interface circuit inputs and outputs electrical signals. The functions of the ECU 100 are realized when the CPU reads and executes the programs stored in the memory. The ECU 100 is an example of a control unit.

[0084] 5, various sensors SW1 to SW7 are electrically connected to the ECU 100. The sensors SW1 to SW7 are electrically connected to the ECU 100 via, for example, a CAN (Controller Area Network). The sensors SW1 to SW7 output signals to the ECU 100. The sensors include the following sensors. Vehicle speed sensor SW1: Measures the vehicle speed from the number of rotations of the wheels W. Accelerator opening sensor SW2: Measures the accelerator opening corresponding to the amount of accelerator pedal operation. Input rotation speed sensor SW3: Measures the rotation speed of the input shaft 4 of the automatic transmission 1. Output rotation speed sensor SW4: Measures the rotation speed of the output shaft 5 of the automatic transmission 1. Oil temperature sensor SW5: Measures the temperature of the ATF. Oil pressure sensor SW6: Measures the oil pressure of the hydraulic oil supplied to each frictional engagement element 10. Input torque sensor SW7: Measures the input torque of the input shaft 4 of the automatic transmission 1.

[0085] The ECU 100 determines the operating state of the automatic transmission 1 based on signals from these sensors SW1 to SW7, and calculates control variables for the engine 51, the inverter 41, the K0 clutch 53, and the automatic transmission 1 according to a predetermined control logic. The control logic is stored in a memory. The control logic includes calculating target variables and / or control variables using a map stored in the memory.

[0086] The ECU 100 controls the gear position of the automatic transmission 1 based on the detection results of, for example, a vehicle speed sensor SW1, an accelerator opening sensor SW2, an input rotation speed sensor SW3, and an output rotation speed sensor SW4.

[0087] The ECU 100 calculates the temperature of the frictional engagement element 10 based on the input rotation speed sensor SW3, the output rotation speed sensor SW4, the oil pressure sensor SW6, and the input torque sensor SW7. The method of calculating the temperature will be described in detail later.

[0088] The ECU 100 calculates the difference between the rotation speed of the first friction plate 14 and the rotation speed of the second friction plate 24 in the frictional engagement element 10 (hereinafter simply referred to as the rotation speed difference) based on the gear position of the automatic transmission 1 and the detection results of at least one of the input rotation speed sensor SW3 and the output rotation speed sensor SW4. The ECU 100 constitutes a rotation speed difference calculation unit.

[0089] The ECU 100 executes rotation speed suppression control to control the rotation speed difference by controlling the rotation speed of the first friction plate 14 based on the temperature and rotation speed difference of the frictional engagement element 10. Details of the rotation speed suppression control will be described later.

[0090] (5) Drag resistance When the frictional engagement element 10 is in a disengaged state, drag resistance occurs in the first friction plate 14. The drag resistance varies depending on the difference in rotation speed between the first friction plate 14 and the second friction plate 24. In the disengaged state, no rotational power is input to the second friction plate 24, and the rotation speed of the second friction plate 24 decreases, so the rotation speed of the first friction plate 14 becomes higher than the rotation speed of the second friction plate 24.

[0091] Figure 6 is a graph showing the relationship between the difference in rotation speed and drag resistance. The solid line shows the drag resistance during the ascending process when the difference in rotation speed is increased from a small state, and the dashed line shows the drag resistance during the descending process when the difference in rotation speed is decreased from a large state.

[0092] As shown in Figure 6, during the increase in the rotational speed difference, drag resistance increases rapidly as the rotational speed difference increases, then peaks and decreases rapidly as the rotational speed difference increases. Drag resistance then gradually increases as the rotational speed difference increases, and increases rapidly as the rotational speed difference increases once the rotational speed difference exceeds a certain value. During the decrease in rotational speed after the sudden increase in the rotational speed difference, even if the rotational speed difference decreases, drag resistance does not decrease as much as during the increase in rotational speed, and remains larger than during the increase in rotational speed. Once the rotational speed difference becomes small to a certain extent, drag resistance during the decrease in rotational speed becomes approximately the same as drag resistance during the increase in rotational speed.

[0093] The aforementioned change in drag resistance will be explained using the first brake BR1 as an example of the frictional engagement element 10. When the frictional engagement element 10 is the first brake BR1, the rotational speed difference corresponds to the rotational speed of the first friction plate 14. The reason drag resistance increases when the rotational speed difference is small, i.e., when the rotational speed of the first friction plate 14 is low, is due to shear torque generated when the first friction plate 14 rotates while cutting off the ATF. As the rotational speed of the first friction plate 14 increases, centrifugal force causes the ATF to diffuse radially, reducing the shear torque and the drag resistance. Thereafter, as the rotational speed of the first friction plate 14 increases, drag resistance gradually increases due to the influence of the viscosity of the ATF. Then, when the rotational speed of the first friction plate 14 exceeds the aforementioned certain value, the second friction plate 24 vibrates (fluttering occurs), and drag resistance increases rapidly.

[0094] The conditions under which the second friction plates 24 vibrate are related to the fluid negative pressure from the ATF and the friction force between the second friction plates 24 and the drum 22. As shown in FIG. 7, fluid negative pressure is input to the second friction plates 24 from both axial sides, generating first negative pressure energy Ep1 and second negative pressure energy Ep2 based on the fluid negative pressure. A static friction force is generated between the second friction plates 24 and the drum 22, and the energy required to overcome this static friction force, i.e., the energy required to overcome the maximum static friction force between the second friction plates 24 and the drum 22, is defined as counter-friction energy Ef. For the second friction plates 24 to start vibrating, the absolute value of the difference between the first negative pressure energy Ep1 and the second negative pressure energy Ep2 must be greater than the counter-friction energy Ef. In other words, for the second friction plates 24 to start vibrating, the following equation 1 must be satisfied:

[0095] |Ep1-Ep2|>Ef (Equation 1) The first negative pressure energy Ep1 and the second negative pressure energy Ep2 are affected by the wedge pressure effect caused by the tilt of the second friction plate 24. Specifically, the first negative pressure energy Ep1 and the second negative pressure energy Ep2 become larger as the gap between the first friction plate 14 and the second friction plate 24 becomes smaller, as the viscosity of the ATF becomes higher, and as the rotation speed of the first friction plate 14 becomes higher. In other words, the rotation speed of the first friction plate 14 at which the above formula 1 is established is determined by the viscosity of the ATF, the gap between the first friction plate 14 and the second friction plate 24, and the static friction between the second friction plate 24 and the drum 22.

[0096] When the above formula 1 is established and the second friction plate 24 starts to vibrate, the friction force acting between the second friction plate 24 and the drum 22 becomes a kinetic friction force. If the counter-friction energy after the second friction plate 24 starts to vibrate is Ef', then in order for the second friction plate 24 to continue vibrating, the following formula 2 must be established.

[0097] |Ep1-Ep2|>Ef' (Equation 2) Because the kinetic friction force is smaller than the maximum static friction force, the counter-friction energy Ef' after the second friction plates 24 start to vibrate is smaller than the counter-friction energy Ef before the second friction plates 24 start to vibrate. The rotation speed of the first friction plates 14 at which the above formula 2 is satisfied is lower than the rotation speed of the first friction plates 14 at which the above formula 1 is satisfied. Therefore, once the above formula 1 is satisfied and the second friction plates 24 start to vibrate, even if the rotation speed of the first friction plates 14 decreases, the above formula 2 is satisfied and the second friction plates 24 continue to vibrate. When the rotation speed of the first friction plates 14 drops to a rotation speed at which the above formula 2 is no longer satisfied, the second friction plates 24 stop vibrating.

[0098] For the above reasons, the relationship between the rotational speed difference and the drag resistance forms a hysteresis curve as shown in Figure 6.

[0099] (6) Rotation speed suppression control If the second friction plates 24 vibrate, they may come into contact with the first friction plates 14, potentially causing seizure. Conventionally, the vibration of the second friction plates 24 has been suppressed by increasing the flow rate of ATF as the rotational speed difference increases. However, as described above, once the second friction plates 24 begin to vibrate, the second friction plates 24 continue to vibrate even if the rotational speed difference is reduced below the rotational speed difference at which the vibration began. For this reason, there is a risk that the amount of ATF will be insufficient when the second friction plates 24 are vibrating, making it impossible to sufficiently suppress the vibration of the second friction plates 24.

[0100] Therefore, in this embodiment 1, the rotation speed of the first friction plate 14 is actively reduced to prevent the second friction plate 24 from starting to vibrate, and after vibration has started, rotation speed suppression control is executed to quickly reduce the rotation speed difference.

[0101] In the rotation speed suppression control according to the first embodiment, when the difference in rotation speed between the first friction plate 14 and the second friction plate 24 increases from a state below the first threshold value to a second threshold value or greater while the friction engagement element 10 is in the released state, the ECU 100 reduces the output of the drive source 50 to reduce the rotation speed of the first friction plate.

[0102] The first threshold value is a value higher than the rotational speed difference at which the drag resistance peaks on the side with a smaller rotational speed difference, as shown in FIG. 6. The first threshold value is the rotational speed at which the vibration of the second friction plates 24 is deemed to have stopped after the second friction plates 24 have started vibrating. The first threshold value is set taking into consideration the viscosity of the ATF in the frictional engagement element 10, the gap between the first friction plates 14 and the second friction plates 24, and the dynamic friction between the second friction plates 24 and the drum 22. The first threshold value Cc1 is not particularly limited, but is, for example, 6000 rpm. The viscosity of the ATF in the frictional engagement element 10 is the viscosity at the oil temperature when the drive source E has completed warming up.

[0103] The second threshold value is the rotation speed at which the second friction plate 24 is deemed to start vibrating. The second threshold value is set taking into consideration the viscosity of the ATF in the frictional engagement element 10, the gap between the first friction plate 14 and the second friction plate 24, and the static friction between the second friction plate 24 and the drum 22. The second threshold value is not particularly limited, but is, for example, 12,000 rpm. The viscosity of the ATF in the frictional engagement element 10 is the viscosity at the oil temperature when the drive source E has completed warming up.

[0104] In the rotation speed suppression control, the ECU 100 reduces the output of the drive source 50, particularly the rotation speed of the engine 51 and the rotation speed of the motor 52. If the rotation speed of the engine 51 and the rotation speed of the motor 52 are reduced, the rotation speed of the input shaft 4 is reduced, and therefore the rotation speeds of the hub 12 and the first friction plate 14 can be reduced. The ECU 100 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52, for example, by limiting the vehicle speed. The ECU 100 reduces the rotation speed of the engine 51, for example, by cutting fuel to the engine 51. The ECU 100 reduces the rotation speed of the motor 52, for example, by reducing the power supplied to the motor 52.

[0105] Here, when the rotation speed of the engine 51 and the rotation speed of the motor 52 are reduced by the rotation speed suppression control, the vehicle speed inevitably decreases. Since this reduction in vehicle speed is not intended by the driver of the vehicle, this reduction in vehicle speed may cause a deterioration in the driving feeling. Therefore, in the first embodiment, when the rotation speed difference increases from a state where it is less than the first threshold value to a third threshold value or greater that is greater than the first threshold value and less than the second threshold value, the automatic transmission 1 is shifted up. The third threshold value is a value slightly smaller than the second threshold value. The third threshold value is not particularly limited, but is, for example, 11,500 rpm.

[0106] Upshifting the automatic transmission 1 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52 required to maintain the vehicle speed. Therefore, the rotation speed of the input shaft 4 decreases while maintaining the vehicle speed, and it is possible to reduce the rotation speeds of the hub 12 and the first friction plate 14. Furthermore, by upshifting before the rotation speed reaches the second threshold value and reducing the rotation speed difference, it is possible to prevent the rotation speed suppression control from being executed.

[0107] When the rotation speed difference increases even after the automatic transmission 1 is shifted up and exceeds the third threshold and becomes equal to or greater than the second threshold, the ECU 100 reduces the output of the drive source 50 (the rotation speed of the engine 51 and the rotation speed of the motor 52).

[0108] In addition, in the first embodiment, the rotation speed reduction control is not executed in a situation where seizure between the friction plates does not occur. Specifically, the ECU 100 prohibits the rotation speed reduction control when the temperature of the friction engagement element 10 is below a predetermined temperature.

[0109] The ECU 100 calculates the rotation speed reduction control based on the detection results of the input rotation speed sensor SW3, output rotation speed sensor SW4, oil pressure sensor SW6, and input torque sensor SW7, as well as the cooling temperature of each frictional engagement element 10 due to heat dissipation into the surrounding atmosphere and ATF. The ECU 100 calculates the temperature of each of the frictional engagement elements 10: the first clutch CL1, the second clutch CL2, the third clutch CL3, and the second brake BR2. The ECU 100 prohibits rotation speed reduction control when the temperature of the frictional engagement element 10 with the highest temperature among the frictional engagement elements 10 is below a predetermined temperature. The predetermined temperature is a temperature at which the friction plates will not seize together.

[0110] The ECU 100 calculates the temperature of each frictional engagement element 10 based on the following equation 3 using the temperature T0 of each frictional engagement element 10 calculated in the immediately preceding cycle, the absorbed energy Ea of each frictional engagement element 10, the heat capacity Q of the friction plates of each frictional engagement element 10, the heat dissipation rate Sc from each frictional engagement element 10 to the surrounding atmosphere and ATF, and the cycle time (time required for one calculation) tc. Note that the initial value of the temperature T0 of each frictional engagement element 10 calculated in the immediately preceding cycle is the ATF oil temperature detected by the oil temperature sensor SW5.

[0111] T1=T0+E / Q+Sc×tc (Formula 3) The ECU 100 calculates the absorbed energy Ea of each frictional engagement element 10 based on the rotational speed difference ΔN between the frictional engagement elements 10 and the transmission torque Trq of each frictional engagement element 10, based on the following equation 4.

[0112] E=ΔN×Trq (Formula 4) As described above, the ECU 100 calculates the rotation speed difference ΔN based on the gear position of the automatic transmission 1 and the detection result of at least one of the input rotation speed sensor SW3 and the output rotation speed sensor SW4.

[0113] The ECU 100 calculates the transmission torque Trq based on the following equation 5. Specifically, the ECU 100 uses the friction coefficient μ, the number n of friction surfaces, the clutch effective radius calculated from the friction surface major diameter Do of each friction engagement element 10 and the friction surface minor diameter Di of each friction engagement element 10, the piston area calculated from the piston major diameter Dpo and piston minor diameter Dpi, the operating oil pressure Pa detected by the oil pressure sensor SW6, and the pressure Pr by the spring 31.

[0114]

number

[0115] The ECU 100 calculates the heat release rate Sc based on a map showing the relationship between the heat release rate Sc of each frictional engagement element 10 and the heat release temperature ΔT of each frictional engagement element 10. FIG. 8 shows the map showing the relationship between the heat release temperature ΔT and the heat release rate Sc. This map is calculated using an approximation formula derived from experimental values ​​of the temperature drop rate of a specific frictional engagement element 10 when a specific flow rate of ATF is supplied to the specific frictional engagement element 10 that is engaged in a specific gear shift state. Note that this map is stored in the memory of the ECU 100 for each frictional engagement element 10 that is engaged in a plurality of gear shift states. The ECU 100 calculates the heat release temperature ΔT of each frictional engagement element 10 by subtracting the ATF oil temperature from the temperature T0 of each frictional engagement element (the value calculated in the previous cycle). The ECU 100 determines the heat release rate Sc based on the calculated heat release temperature ΔT and the map.

[0116] The ECU 100 calculates the temperature of each frictional engagement element 10, compares the highest temperature with a predetermined temperature, and determines whether or not to execute rotation suppression control.

[0117] 9 is a flowchart of vibration suppression control executed by the ECU 100. The processing according to this flowchart is executed by the CPU reading a program from memory. In the initial state, the difference in rotation speed between the first friction plate 14 and the second friction plate 24 is less than the first threshold value. While the flowchart is being executed, the ECU 100 constantly reads information from the sensors SW1 to SW7 and calculates the difference in rotation speed and the temperature of each friction engagement element 10.

[0118] In step S101, the ECU 100 determines whether the rotation speed difference Cd between the first friction plate 14 and the second friction plate 24 is equal to or greater than the third threshold value Cc3. If the rotation speed difference Cd is equal to or greater than the third threshold value Cc3 (YES), the ECU 100 proceeds to step S102. If the rotation speed difference Cd is less than the third threshold value Cc3 (NO), the ECU 100 returns.

[0119] In step S102, the ECU 100 upshifts the automatic transmission 1. The ECU 100 upshifts the gear by one gear.

[0120] In the next step S103, the ECU 100 determines whether the rotation speed difference Cd is equal to or greater than the second threshold value Cc2. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (YES), the ECU 100 proceeds to step S104. If the rotation speed difference Cd is less than the second threshold value Cc2 (NO), the ECU 100 returns.

[0121] In step S104, the ECU 100 determines whether the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc. The ECU 100 makes this determination by comparing the temperature of the frictional engagement element 10 with the predetermined temperature Tc. If the result is YES, meaning that the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc, the ECU 100 proceeds to step S105. If the result is NO, meaning that the temperature Tf of the frictional engagement elements 10 is lower than the predetermined temperature Tc, the ECU 100 returns.

[0122] In step S105, the ECU 100 reduces the output of the drive source 50. In particular, the ECU 100 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52.

[0123] In the next step S106, the ECU 100 determines whether the rotation speed difference Cd is less than the first threshold value Cc1. If the rotation speed difference Cd is less than the first threshold value Cc1 (YES), the ECU 100 proceeds to step S108. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (NO), the ECU 100 proceeds to step S107.

[0124] In step S107, the ECU 100 determines whether the temperature Tf of the frictional engagement element 10 is lower than the predetermined temperature Tc. If the result is YES, meaning that the temperature Tf of the frictional engagement element 10 is lower than the predetermined temperature Tc, the ECU 100 proceeds to step S108. If the result is NO, meaning that the temperature Tf of the frictional engagement element 10 is equal to or higher than the predetermined temperature Tc, the ECU 100 returns to step S106.

[0125] In step S108, the ECU 100 cancels the reduction in the output of the driving source 50. After step S108, the ECU 100 returns.

[0126] FIG. 10 is a time chart showing an example of the rotation speed difference, gear position, and flow rate when the vibration suppression control described above is executed. Here, the first brake BR1 is used as an example of the frictional engagement element 10. In the initial state, the automatic transmission 1 is in second gear, and the frictional engagement element 10 is in an engaged state. Because the frictional engagement element 10 is in the engaged state, the rotation speed difference between the first friction plate 14 and the second friction plate 24 is zero. In addition, the automobile V is running mainly driven by the engine 51.

[0127] At time t1, the gear is shifted up from second speed to third speed, and the frictional engagement element 10 is released, and the rotation speed difference gradually increases.

[0128] At time t2, when the rotation speed difference becomes equal to or greater than the third threshold value Cc3, the gear is shifted up from third to fourth. The upshift reduces the rotation speed of the engine 51. This reduces the rotation speed difference.

[0129] The rotation speed of the engine 51 continues to increase after the upshift, and when the rotation speed difference reaches the second threshold value Cc2 at time t3, the rotation speed of the engine 51 is reduced by the rotation speed suppression control.

[0130] At time t4, when the rotation speed difference becomes less than the first threshold value Cc1, the rotation speed suppression control ends. The gear is shifted down from fourth to third. The downshift increases the rotation speed of the engine 51. This increases the rotation speed difference. Thereafter, when the engine rotation speed is maintained constant, the rotation speed difference also becomes constant.

[0131] (7) Effects of the First Embodiment Therefore, in the first embodiment, when the rotation speed difference between the first friction plate 14 and the second friction plate 24 increases from a state where it is less than the first threshold to a second threshold or greater, the ECU 100 executes rotation speed suppression control to reduce the rotation speed difference by reducing the rotation speed of the first friction plate 14. When the rotation speed difference becomes less than the first threshold while the rotation speed suppression control is being executed in the disengaged state, the ECU 100 terminates the rotation speed suppression control. As a result, even if the rotation speed difference becomes less than the second threshold after the rotation speed suppression control is executed, the rotation speed suppression control continues to be executed until the rotation speed difference becomes less than the first threshold. Therefore, the rotation speed difference can be quickly reduced to a rotation speed difference at which the second friction plate 24 is unlikely to vibrate, and vibration of the second friction plate 24 can be efficiently suppressed. Therefore, the first embodiment can suppress seizure between the friction plates when the friction engagement element 10 is in the disengaged state.

[0132] Furthermore, by quickly reducing the rotational speed difference, it is possible to shorten the period during which the second friction plate 24 vibrates. This shortens the period during which the drag resistance increases due to the vibration of the second friction plate 24. This first embodiment can suppress deterioration of energy consumption.

[0133] In the first embodiment, the ECU 100 reduces the rotation speed of the first friction plates 14 by reducing the rotation speed of the drive source 50 during rotation speed reduction control. This directly reduces the input rotation speed to the friction engagement element 10, thereby efficiently reducing the rotation speed of the first friction plates 14. The first embodiment can prevent the friction plates from seizing together when the friction engagement element 10 is in the released state.

[0134] In the first embodiment, the ECU 100 upshifts the automatic transmission 1 when the rotation speed difference increases from a state where it is less than the first threshold to a third threshold or greater, which is greater than the first threshold and less than the second threshold. After the automatic transmission 1 is upshifted, the ECU 100 reduces the rotation speed of the drive source 50 when the rotation speed difference exceeds the third threshold and becomes greater than the second threshold. This allows the automatic transmission 1 to upshift before the rotation speed difference reaches the first threshold, thereby reducing the rotation speed of the first friction plate 14. Since the rotation speed difference can be prevented from reaching the second threshold, the second friction plate 24 can be prevented from starting to vibrate. Furthermore, since the rotation speed of the drive source 50 required to maintain vehicle speed is reduced by upshifting compared to before the upshift, an increase in the rotation speed difference during acceleration can be suppressed. As a result, the first embodiment can prevent the friction plates from seizing when the frictional engagement element 10 is in a disengaged state.

[0135] In the first embodiment, the ECU 100 prohibits the rotation speed reduction control when the temperature of the frictional engagement element 10 is below a predetermined temperature. In a situation where the temperature of the frictional engagement element 10 is low and the friction plates are unlikely to seize together, prohibiting the rotation speed reduction control can reduce the impact on the driving feel.

[0136] In the first embodiment, the second threshold value is set in consideration of the viscosity of the ATF in the frictional engagement element 10, the distance between the first friction plate 14 and the second friction plate 24, and the static friction between the second friction plate 24 and the drum 22. This allows the rotation speed difference at which the second friction plate 24 begins to vibrate to be set with high precision. The first embodiment can prevent the friction plates from seizing together when the frictional engagement element 10 is in a disengaged state.

[0137] In the first embodiment, the first threshold value is set in consideration of the viscosity of the lubricating oil in the frictional engagement element 10, the gap between the first friction plate 14 and the second friction plate 24, and the dynamic friction between the second friction plate 24 and the drum 22. This allows for accurate setting of the rotation speed difference at which the second friction plate 24 is less likely to vibrate. The first embodiment can prevent the friction plates from seizing together when the frictional engagement element 10 is in the released state.

[0138] In the first embodiment, the ECU 100 calculates the difference in rotation speed between the first friction plate 14 and the second friction plate 24 based on the gear position of the automatic transmission 1 and the input rotation speed or the output rotation speed of the automatic transmission 1. This eliminates the need to provide a sensor to detect the rotation speed of the first friction plate 14 and a sensor to detect the rotation speed of the second friction plate 24. The first embodiment allows the automatic transmission 1 to have a compact configuration.

[0139] Second Embodiment Hereinafter, the second embodiment will be described in detail with reference to the drawings. In the following description, parts common to the first embodiment will be given the same reference numerals and detailed description thereof will be omitted.

[0140] (8) Vibration suppression control In the second embodiment, the configuration of the frictional engagement element 10 is the same as in the first embodiment. However, in the second embodiment, the processing operation of the ECU 100 in vibration suppression control is different from that in the first embodiment.

[0141] 11 is a flowchart of vibration suppression control executed by the ECU 100 in the second embodiment. The processing according to this flowchart is executed by the CPU reading a program from memory. In the initial state, the difference in rotation speed between the first friction plate 14 and the second friction plate 24 is less than the first threshold value. While the flowchart is being executed, the ECU 100 constantly reads information from the sensors SW1 to SW7 and calculates the difference in rotation speed and the temperature of each friction engagement element 10.

[0142] In step S201, the ECU 100 determines whether the rotation speed difference Cd between the first friction plate 14 and the second friction plate 24 is equal to or greater than the third threshold value Cc3. If the rotation speed difference Cd is equal to or greater than the third threshold value Cc3 (YES), the ECU 100 proceeds to step S202. If the rotation speed difference Cd is less than the third threshold value Cc3 (NO), the ECU 100 returns.

[0143] In step S202, the ECU 100 upshifts the automatic transmission 1. The ECU 100 upshifts the gear by one gear.

[0144] In the next step S203, the ECU 100 determines whether the rotation speed difference Cd is equal to or greater than the second threshold value Cc2. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (YES), the ECU 100 proceeds to step S204. If the rotation speed difference Cd is less than the second threshold value Cc2 (NO), the ECU 100 returns.

[0145] In step S204, the ECU 100 determines whether the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc. The ECU 100 makes this determination by comparing the temperature of the frictional engagement element 10 with the predetermined temperature Tc. If the result is YES, meaning that the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc, the ECU 100 proceeds to step S205. If the result is NO, meaning that the temperature Tf of the frictional engagement elements 10 is lower than the predetermined temperature Tc, the ECU 100 proceeds to step S206.

[0146] In step S205, the ECU 100 reduces the output of the drive source 50 at the first speed. In particular, the ECU 100 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52.

[0147] In step S206, the ECU 100 reduces the output of the drive source 50 at a second speed. The second speed is lower than the first speed. In particular, the ECU 100 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52.

[0148] In the next step S207, the ECU 100 determines whether the rotation speed difference Cd is less than the first threshold value Cc1. If the rotation speed difference Cd is less than the first threshold value Cc1 (YES), the ECU 100 proceeds to step S208. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (NO), the ECU 100 returns to step S204.

[0149] In step S208, the ECU 100 cancels the reduction in the output of the drive source 50. After step S208, the ECU 100 returns.

[0150] (7) Effects of the Second Embodiment In the second embodiment, when the temperature of the frictional engagement element 10 is below a predetermined temperature, the ECU 100 reduces the rate at which the output of the drive source 50 is reduced during rotation speed suppression control, compared to when the temperature of the frictional engagement element 10 is equal to or higher than the predetermined temperature. As a result, in a situation where the temperature of the frictional engagement element 10 is low and the friction plates are unlikely to seize together, the output of the drive source 50 is reduced, but at a slower rate, thereby minimizing the impact on the driving feel.

[0151] Third Embodiment Hereinafter, the third embodiment will be described in detail with reference to the drawings. In the following description, parts common to the first and second embodiments will be given the same reference numerals, and detailed description thereof will be omitted.

[0152] (10) Vibration suppression control In the third embodiment, the configuration of the frictional engagement element 10 is the same as in the first embodiment. However, in the third embodiment, the processing operation of the ECU 100 in vibration suppression control is different from that in the first embodiment.

[0153] 12 is a flowchart of vibration suppression control executed by the ECU 100 in the third embodiment. The processing according to this flowchart is executed by the CPU reading a program from memory. In the initial state, the difference in rotation speed between the first friction plate 14 and the second friction plate 24 is less than the first threshold value. While the flowchart is being executed, the ECU 100 constantly reads information from the sensors SW1 to SW7 and calculates the difference in rotation speed and the temperature of each friction engagement element 10.

[0154] In step S301, the ECU 100 determines whether the rotation speed difference Cd between the first friction plate 14 and the second friction plate 24 is equal to or greater than the second threshold value Cc2. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (YES), the ECU 100 proceeds to step S302. If the rotation speed difference Cd is less than the second threshold value Cc2 (NO), the ECU 100 returns.

[0155] In step S302, the ECU 100 determines whether the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc. The ECU 100 compares the temperature of the frictional engagement element 10 with the predetermined temperature Tc to make this determination. If the result is YES, meaning that the temperature Tf of the frictional engagement elements 10 is equal to or higher than the predetermined temperature Tc, the ECU 100 proceeds to step S303. If the result is NO, meaning that the temperature Tf of the frictional engagement elements 10 is lower than the predetermined temperature Tc, the ECU 100 returns.

[0156] In step S303, the ECU 100 upshifts the automatic transmission 1. The ECU 100 upshifts the gear by one gear.

[0157] In the next step S304, the ECU 100 reduces the output of the drive source 50. In particular, the ECU 100 reduces the rotation speed of the engine 51 and the rotation speed of the motor 52.

[0158] In the next step S305, the ECU 100 determines whether the rotation speed difference Cd is less than the first threshold value Cc1. If the rotation speed difference Cd is less than the first threshold value Cc1 (YES), the ECU 100 proceeds to step S307. If the rotation speed difference Cd is equal to or greater than the second threshold value Cc2 (NO), the ECU 100 proceeds to step S306.

[0159] In step S306, the ECU 100 determines whether the temperature Tf of the frictional engagement element 10 is lower than the predetermined temperature Tc. If the result is YES, meaning that the temperature Tf of the frictional engagement element 10 is lower than the predetermined temperature Tc, the ECU 100 proceeds to step S307. If the result is NO, meaning that the temperature Tf of the frictional engagement element 10 is equal to or higher than the predetermined temperature Tc, the ECU 100 returns to step S305.

[0160] In step S307, the ECU 100 cancels the reduction in the output of the drive source 50.

[0161] In the next step S308, the ECU 100 downshifts the automatic transmission 1. The ECU 100 downshifts the gear by one step. After step S308, the ECU 100 returns.

[0162] (11) Effects of the Third Embodiment In the third embodiment, the ECU 100 reduces the rotation speed of the first friction plates 14 during the rotation speed suppression control by reducing the output of the drive source 50 and upshifting the automatic transmission 1. Thus, the rotation speed of the first friction plates 14 is reduced by upshifting the automatic transmission 1, so the rotation speed of the first friction plates 14 can be reduced while suppressing a decrease in vehicle speed. Furthermore, because the rotation speed of the drive source 50 is reduced by upshifting, the rotation speed of the first friction plates 14 can be reduced quickly, and ultimately the difference in rotation speed between the first friction plates 14 and the second friction plates 24 can be reduced quickly. The third embodiment can suppress seizure between the friction engagement elements 10 while suppressing an impact on the driving feel when the friction engagement elements 10 are in a disengaged state.

[0163] Other Embodiments The technology disclosed herein is not limited to the above-described embodiments, and can be substituted within the scope of the claims.

[0164] For example, in the above-described first to third embodiments, the first and second thresholds are set based on the viscosity of the ATF at the oil temperature when the warm-up of the driving source E is complete. However, the first and second thresholds may be set based on the current viscosity of the ATF. The current viscosity of the ATF can be calculated based on the detected value of the oil temperature sensor SW5 and a map or a calculation formula stored in the memory of the ECU 100. As the viscosity of the ATF increases, the energy due to the wedge pressure effect at the same engine speed increases. Therefore, the first and second thresholds may be set lower than in the first to third embodiments. Conversely, as the viscosity of the ATF decreases, the energy due to the wedge pressure effect at the same engine speed decreases. Therefore, the first and second thresholds may be set higher than in the first to third embodiments. Furthermore, the first and second thresholds may be changed before and after the warm-up of the driving source E is complete. Before the warm-up of the driving source E is complete, the oil temperature is low and the viscosity of the ATF is high. Therefore, the first and second thresholds may be set lower than in the first to third embodiments.

[0165] In the above-described first to third embodiments, the ECU 100 calculates the difference in rotation speed between the first friction plate 14 and the second friction plate 24 based on the gear position of the automatic transmission 1 and the detection results of at least one of the input rotation speed sensor SW3 and the output rotation speed sensor SW4. However, the present invention is not limited to this, and a sensor for detecting the rotation speed of the first friction plate 14 and a sensor for detecting the rotation speed of the second friction plate 24 may be provided, and the ECU 100 may calculate the difference in rotation speed based on the detection results of these sensors.

[0166] In the first to third embodiments described above, the temperature of each frictional engagement element 10 is calculated by the ECU 100. However, this is not limiting, and a sensor for measuring the temperature of each frictional engagement element 10 may be provided.

[0167] Furthermore, in the first to third embodiments described above, the frictional engagement element 10 is a part of the automatic transmission 1, but it may also be applied to an in-vehicle device other than the automatic transmission 1.

[0168] Furthermore, in the above-described first and second embodiments, the automatic transmission 1 is upshifted when the rotation speed difference between the first friction plate 14 and the second friction plate 24 is equal to or greater than the third threshold value. Furthermore, in the above-described third embodiment, the automatic transmission 1 is upshifted as rotation speed suppression control. However, this is not limited to this, and this shift control may be omitted. In particular, when the automatic transmission 1 is configured only with friction engagement elements 10 that are not maintained in a released state during upshifting, such as the first clutch CL1 and the second clutch CL2, the above-described shift control is not necessary.

[0169] In the first and third embodiments described above, the rotation speed reduction control is prohibited when the temperature Tf of the frictional engagement element 10 is equal to or higher than the predetermined temperature Tc. In the second embodiment described above, the rotation speed reduction control is changed based on whether the temperature Tf of the frictional engagement element 10 is equal to or higher than the predetermined temperature Tc. However, the present invention is not limited to this, and a preset rotation speed reduction control may be executed regardless of the temperature of the frictional engagement element 10.

[0170] Furthermore, in the above-described first to third embodiments, the target vehicle is a hybrid automobile, but the target vehicle may also be an electric automobile that runs on a motor alone, or an automobile that runs on an engine alone.

[0171] The above-described embodiments are merely examples and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations that fall within the scope of the claims equivalents are within the scope of the present disclosure. [Industrial Applicability]

[0172] The technology disclosed herein is useful as a vehicle control device. [Explanation of symbols]

[0173] 1 Automatic transmission 10 Frictional fastening elements 12 Hub (first member) 14 1st friction plate 22 Drum (second member) 24 2nd friction plate 50 Power Source 100 ECU (control unit, rotation speed difference calculation unit) V Automobile (vehicle)

Claims

1. A control device for a vehicle, A driving source; a wet friction engagement element to which rotational power from the drive source is input; a control unit that controls the drive source, The frictional fastening element is a first friction plate and a second friction plate that are in an engaged state and a disengaged state; a first member that engages with the first friction plate and rotates together with the first friction plate due to rotational power from the drive source; a second member that engages with the second friction plate and to which rotational power is transmitted from the first member in the fastened state; Including, The control unit In the released state, when the rotation speed difference between the first friction plate and the second friction plate increases from a state where it is less than a first threshold value to become equal to or greater than a second threshold value that is greater than the first threshold value, a rotation speed suppression control is executed to reduce the rotation speed difference by reducing the rotation speed of the first friction plate, A vehicle control device that terminates the rotation speed suppression control when the rotation speed difference becomes less than the first threshold value while the rotation speed suppression control is being executed in the released state.

2. 2. The vehicle control device according to claim 1, The control unit is a vehicle control device that, during the rotation speed suppression control, reduces the rotation speed of the first friction plate by reducing the output of the drive source.

3. 3. The vehicle control device according to claim 2, the frictional engagement element is part of an automatic transmission that changes the rotational power of the drive source, The control unit controlling the automatic transmission, and shifting up the automatic transmission when the rotation speed difference increases from a state where it is less than the first threshold value and becomes equal to or greater than a third threshold value that is greater than the first threshold value and less than the second threshold value; A vehicle control device that reduces the output of the drive source when the rotation speed difference exceeds the third threshold and becomes equal to or greater than the second threshold after the automatic transmission is shifted up.

4. 3. The vehicle control device according to claim 2, the frictional engagement element is part of an automatic transmission that changes the rotational power of the drive source, The control unit controls the automatic transmission and, in the rotation speed suppression control, reduces the output of the drive source and upshifts the automatic transmission to reduce the rotation speed of the first friction plate.

5. 3. The vehicle control device according to claim 2, The control unit prohibits the rotation speed suppression control when the temperature of the frictional engagement element is lower than a predetermined temperature.

6. 3. The vehicle control device according to claim 2, The control unit is a vehicle control device that, when the temperature of the frictional engagement element is below a predetermined temperature, reduces the rate at which the output of the drive source is reduced in the rotation speed suppression control compared to when the temperature of the frictional engagement element is equal to or higher than the predetermined temperature.

7. The vehicle control device according to any one of claims 1 to 6, a control device for a vehicle, wherein the second threshold value is a value set taking into consideration the viscosity of the lubricating oil supplied between the first friction plate and the second friction plate, the distance between the first friction plate and the second friction plate, and the static friction between the second friction plate and the second member.

8. The vehicle control device according to any one of claims 1 to 6, a first threshold value being a value set in consideration of the viscosity of the lubricating oil supplied between the first friction plate and the second friction plate, the distance between the first friction plate and the second friction plate, and the dynamic friction between the second friction plate and the second member.

9. The vehicle control device according to any one of claims 1 to 6, a rotation speed difference calculation unit that detects the rotation speed difference, the frictional engagement element is part of an automatic transmission, The rotation speed difference calculation unit calculates the rotation speed difference based on a gear position of the automatic transmission and an input rotation speed or an output rotation speed of the automatic transmission.

10. A vehicle control method, comprising: The vehicle is A driving source; a wet frictional fastening element to which rotational power from the drive source is input, The frictional fastening element is a first friction plate and a second friction plate that are in an engaged state and a disengaged state; a first member that engages with the first friction plate and rotates together with the first friction plate due to rotational power from the drive source; a second member that engages with the second friction plate and to which rotational power is transmitted from the first member in the fastened state; and a step of executing a rotation speed suppression control to reduce the rotation speed difference by reducing the rotation speed of the first friction plate when the rotation speed difference between the first friction plate and the second friction plate increases from a state where it is less than a first threshold value to a second threshold value or more that is greater than the first threshold value in the released state; and terminating the rotation speed suppression control when the rotation speed difference becomes less than the first threshold value while the rotation speed suppression control is being executed in the released state.

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