Automatic transmission

Abstract

To realize a technique capable of forming a shift stage using a double piston-type frictional engagement element, even in a failure state in which one of pistons of the double piston-type frictional engagement element fails to generate engagement pressure.SOLUTION: A control device 60 applies any one of a first piston B2a and a second piston B2b that generates engagement pressure as a normal piston, in a specific failure state in which any one of the first piston B2a and the second piston B2b fails to generate the engagement pressure, and performs torque limit control for limiting the torque transmitted to an input member from a driving power source to fall below a limit torque, which is set within a range where a double piston-type second brake B2 can transmit by the engagement pressure of the normal piston in a direct engagement state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an automatic transmission equipped with multiple friction engagement elements. [Background technology]

[0002] Automatic transmissions equipped with a double-piston type friction engagement element are known to ensure high torque capacity. Patent Document 1 describes an automatic transmission equipped with a hydraulic friction engagement device having a first hydraulic piston and a second hydraulic piston. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-112245 [Overview of the project] [Problems that the invention aims to solve]

[0004] The automatic transmission described in Patent Document 1 detects an abnormality in the first solenoid valve that acts on the first hydraulic piston based on the change in the input shaft rotation speed. However, the automatic transmission in Patent Document 1 did not anticipate the use of a double-piston type friction engagement element after detecting an abnormality. Therefore, it was not possible to form a gear using the double-piston type friction engagement element, which severely restricted the operation of the vehicle. However, with a double-piston type friction engagement element, even if engagement pressure is not generated in one of the pistons, if engagement pressure is generated in the other piston, it is possible to engage within the range of that engagement pressure, and there is room to form a gear using the double-piston type friction engagement element and use it for vehicle operation.

[0005] Therefore, it is desirable to realize a technology that enables the formation of gear stages using a double-piston friction engagement element even in a faulty state where engagement pressure is not generated by one of the pistons of the double-piston friction engagement element. [Means for solving the problem]

[0006] In light of the above, the characteristic configuration of the automatic transmission is: An automatic transmission comprising: a transmission device that transmits the rotation of an input member driven by a power source to an output member at a gear ratio of one of several gear stages; and a control device that controls the transmission device, The transmission comprises a plurality of friction engagement elements and a plurality of control valves for controlling the engagement state of the plurality of friction engagement elements, and a plurality of gear stages are formed according to the engagement state of the plurality of friction engagement elements. The target engagement element is a double-piston type friction engagement element, one of the plurality of friction engagement elements, comprising a first piston operated by hydraulic pressure controlled by a first control valve, which is a first control valve, and a second piston operated by hydraulic pressure controlled by a second control valve, which is a second control valve, and engaged by the engagement pressure of at least one of the first piston and the second piston. The gear shift stage formed by engaging the aforementioned target engagement element is designated as the target gear shift stage. The control device is In a specific fault condition where engagement pressure is not generated in either the first piston or the second piston, the piston that generates engagement pressure is considered the normal piston. The key feature is torque limiting control, which limits the torque transmitted from the driving force source to the input member to a limit torque set within a range that the target engaging element can transmit in a directly engaged state by the engagement pressure of the normal piston.

[0007] This feature configuration makes it possible to engage the target engagement element using the normal piston that generates engagement pressure, even in a specific fault condition where engagement pressure is not generated in either the first or second piston of the target engagement element, thereby forming a gear shift using that target engagement element. Furthermore, when forming a gear shift using such a target engagement element, torque limiting control is performed to limit the torque transmitted from the drive source to the input member to a limit torque set within the range that the target engagement element can transmit in a direct engagement state by the engagement pressure of the normal piston. This makes it easier to avoid deterioration and failure of the target engagement element due to the continued slip engagement state of the target engagement element.

[0008] Further features and advantages of the technology relating to this disclosure will become clearer from the following description of exemplary and non-limiting embodiments, with reference to the drawings. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram of an automatic transmission according to an embodiment of the present invention. [Figure 2] Control block diagram of the automatic transmission shown in Figure 1. [Figure 3] Figure 1 is a diagram illustrating the engagement table of the automatic transmission. [Figure 4] A cross-sectional view showing an enlarged view of the second brake in Figure 1. [Figure 5] A schematic diagram illustrating the hydraulic circuit of the automatic transmission shown in Figure 1. [Figure 6] A schematic diagram showing the drive force transmission state in the hydraulic circuit of Figure 5, where the forward travel stage is formed. [Figure 7] A schematic diagram showing the power transmission state in which a reverse travel stage is formed in the hydraulic circuit of Figure 5. [Figure 8] Figure 5 shows a state in which the switching control valve is malfunctioning in the hydraulic circuit where a reverse travel stage is formed during power transmission. [Figure 9] A flowchart showing the processing procedure for torque limiting control by the control device in Figure 1. [Modes for carrying out the invention]

[0010] An embodiment of the automatic transmission 10 according to this embodiment will be described based on the drawings. FIG. 1 is a schematic diagram of the automatic transmission 10. FIG. 2 is a control block diagram of the automatic transmission 10. In this embodiment, the automatic transmission 10 is mounted on a vehicle including a vehicle power source 11, a driving force source 12 such as a rotating electric machine, a differential device and wheels (not shown), and transmits the driving force input from the driving force source 12 to a differential gear device. The differential gear device distributes the input driving force to a pair of wheels. As the vehicle power source 11, for example, a power storage device such as a battery provided in the vehicle, a power receiving device that receives power supply from outside the vehicle, or the like is used. In the present application, the "rotating electric machine" is used as a concept including any of a motor (electric motor), a generator (generator), and a motor-generator that performs both functions of a motor and a generator as required.

[0011] The automatic transmission 10 includes a transmission device 20 that changes the rotation of an input member 20n driven by a driving force source 12 at a gear ratio ν of any one of a plurality of gear stages and transmits it to an output member 20t. In this embodiment, the automatic transmission 10 further includes a torque converter 30 as a fluid coupling. The torque converter 30 includes a stator-side impeller 34 having a one-way clutch 37 between a pump-side impeller (pump impeller) 32 drivingly connected to an output member 12t of the driving force source 12 and a case that is a non-rotating member 14, and a turbine-side impeller (turbine runner) 36 drivingly connected to an input member 20n of the transmission device 20. In the illustrated example, the torque converter 30 is provided with a direct clutch CD1, which is a lock-up clutch, in the power transmission path between the pump-side impeller 32 and the turbine-side impeller 36. In the illustrated example, the rotational speed of the output member 12t of the driving force source 12 is detected by a driving force source rotational speed sensor 42. The rotational speed of the input member 20n of the transmission device 20 is detected by an input shaft rotational speed sensor 44. The rotational speed of the output member 20t of the transmission device 20 is detected by an output shaft rotational speed sensor 46.

[0012] In the present application, "driving connection" refers to a state in which two rotating elements are connected so as to be able to transmit a driving force, including a state in which the two rotating elements are connected so as to rotate integrally, or a state in which the two rotating elements are connected so as to be able to transmit a driving force via one or more transmission members. Such transmission members include various members that transmit rotation at the same speed or with speed change, and for example, shafts, gear mechanisms, belts, chains, etc. are included. Further, as such a transmission member, an engagement device that selectively transmits rotation and a driving force, for example, a friction engagement device or a meshing engagement device, etc. may be included.

[0013] FIG. 3 is a diagram showing an engagement table of the automatic transmission 10. The transmission device 20 includes a plurality of friction engagement elements CL and a plurality of control valves VL that control the engagement states of the plurality of friction engagement elements CL. Depending on the engagement states of the plurality of friction engagement elements CL, any one of a plurality of gear stages is formed. In the present embodiment, the plurality of friction engagement elements CL include a clutch C that engages rotating members with each other and a brake B that engages a non-rotating member with a rotating member. In the example shown in FIG. 1, the transmission device 20 is configured using a first planetary gear mechanism PG1 and a second planetary gear mechanism PG2.

[0014] In the present embodiment, as shown in FIGS. 1 to 3, the transmission device 20 includes a direct clutch CD1, a first clutch C1, a second clutch C2, a third clutch C3, a fourth clutch C4, a first brake B1, and a second brake B2 as the plurality of friction engagement elements CL.

[0015] The transmission 20 has a symmetric engagement element DP, which is a double-piston type friction engagement element that is one of a plurality of friction engagement elements CL and comprises a first piston B2a that is operated by hydraulic pressure controlled by a first control valve VL1, which is a first control valve, and a second piston B2b that is operated by hydraulic pressure controlled by a second control valve VL2, which is a second control valve, and is engaged by the engagement pressure of at least one of the first piston B2a and the second piston B2b. In the illustrated example, the first control valve VL1 is a sixth linear solenoid valve SL6, the second control valve VL2 is a switching control valve Vn1, and the symmetric engagement element DP is a second brake B2.

[0016] Figure 4 is an enlarged view of the cross-section of the second brake B2. In the example shown in Figure 4, the second brake B2 comprises a piston case 51, an inner piston (first piston B2a), an outer piston (second piston B2b), and a plurality of friction plates 52. The first piston B2a and the second piston B2b are slidably arranged within the piston case 51. O-rings 57 are fitted to the first piston B2a and the second piston B2b to seal them against the inner circumferential surface of the piston case 51. A first oil chamber 54 is formed between the first piston B2a and the piston case 51. A second oil chamber 56 is formed between the second piston B2b and the piston case 51.

[0017] The tip of the first piston B2a is positioned between the second piston B2b and the friction plate 52, and is in contact with the friction plate 52. The first piston B2a is biased by the return spring 58 in a direction away from the friction plate 52. When hydraulic pressure is supplied to the first oil chamber 54, the tip of the first piston B2a presses against the friction plate 52, generating engagement pressure that engages the second brake B2. Also, when hydraulic pressure is supplied to the second oil chamber 56, the second piston B2b presses against the friction plate 52 via the first piston B2a, generating engagement pressure that engages the second brake B2.

[0018] Here, regarding the engagement state of the friction engagement element CL, the state in which rotation and torque are not transmitted between the engaging members of the friction engagement element CL is defined as the "released state," and the state in which rotation and torque are transmitted between the engaging members of the friction engagement element CL is defined as the "engaged state." Furthermore, within the "engaged state," the state in which torque is transmitted while there is a difference in rotation between the engaging members of the friction engagement element CL is defined as the "slip engagement state," and the state in which the engaging members on both sides of the friction engagement element CL are engaged to rotate as a single unit is defined as the "direct engagement state." Note that the "released state" also includes the state in which rotation and torque are unintentionally transmitted due to the joint rotation between the engaging members of the friction engagement element CL, even though the friction engagement element CL is controlled to be unengaged.

[0019] In this embodiment, as shown in Figure 3, when multiple friction engagement elements CL marked with "○" are engaged and the remaining friction engagement elements CL are released, a driving force transmission state is achieved, i.e., one of the multiple gear stages is formed. When all friction engagement elements CL are released, a neutral stage "N" is formed, which puts the transmission 20 into a neutral state. In this embodiment, since one of the gear stages is formed when two friction engagement elements CL are engaged, a neutral stage "N" is also formed when only one of the multiple friction engagement elements CL is engaged.

[0020] In this embodiment, the multiple gears include eight forward gears "D" with different gear ratios ν: the first gear "1st", second gear "2nd", third gear "3rd", fourth gear "4th", fifth gear "5th", sixth gear "6th", seventh gear "7th", and eighth gear "8th", and a reverse gear "R". In the forward gears "D", the gear ratio ν decreases in stages from the first gear "1st" to the eighth gear "8th", that is, from the low-speed gears to the high-speed gears. Here, the gear ratio ν is the ratio of the rotational speed of the input member 20n to the rotational speed of the output member 20t. Although not shown in Figure 3, the direct-drive clutch CD1 is preferably in a disengaged state in the neutral gear "N" and reverse gear "R", and in the forward gear "D", it is switched between engaged and disengaged states depending on conditions such as vehicle speed, throttle opening, and engine speed.

[0021] Figure 5 is a simplified diagram of the hydraulic circuit 25 of the transmission 20. The transmission 20 includes a hydraulic generator 22 that generates hydraulic pressure for engaging multiple friction engagement elements CL, and a hydraulic circuit 25 that can switch the hydraulic pressure supply path from the hydraulic generator 22 to each of the multiple control valves VL. In this embodiment, the hydraulic circuit 25 consists of multiple control valves VL and oil passages. In this embodiment, the transmission 20 has multiple control valves VL that individually control the hydraulic pressure to the multiple friction engagement elements CL in order to control the engagement state of the multiple friction engagement elements CL. In the example shown in Figure 5, the first linear solenoid valves SL1 to the sixth linear solenoid valve SL6, the first switching valve Vw1, the second switching valve Vw2, the first auxiliary hydraulic pressure supply valve Vs1, the third auxiliary hydraulic pressure supply valve Vs3, the switching control valve Vn1, the check valve Vc1, and the manual valve MV function as the multiple control valves VL. These multiple control valves VL are supplied with hydraulic pressure discharged from the oil pump OP of the hydraulic pressure generating device 22 shown in Figure 2, which has been regulated to the appropriate line pressure by the primary regulator valve Vp1, secondary regulator valve Vp2, etc.

[0022] In this embodiment, the first linear solenoid valve SL1 to the fourth linear solenoid valve SL4 adjust the supply hydraulic pressure according to the current applied to their respective solenoid sections to generate engagement pressure for engaging the first clutch C1 to the fourth clutch C4. The fifth linear solenoid valve SL5 adjusts the supply hydraulic pressure according to the current applied to its solenoid section to generate engagement pressure for engaging the first brake B1. The sixth linear solenoid valve SL6 adjusts the supply hydraulic pressure according to the current applied to its solenoid section to operate the first piston B2a and generate engagement pressure for engaging the second brake B2.

[0023] In this embodiment, the first switching valve Vw1 is a valve that switches the direct-drive clutch CD1 between the engaged side (lock-up on side) and the released side (lock-up off side), and functions as a so-called lock-up relay valve. The second switching valve Vw2 is a valve that can interrupt the hydraulic pressure from the hydraulic pressure generator 22 to the second piston B2b and can be switched between the interrupted side and the engaged side, and functions as a so-called B2 apply control valve. The switching control valve Vn1 is a valve that outputs a signal pressure to switch the first switching valve Vw1 and the second switching valve Vw2, and functions as a so-called ON-OFF solenoid valve. Preferably, the switching control valve Vn1 outputs a signal pressure to switch the first switching valve Vw1 in the forward travel stage D, and outputs a signal pressure to switch the second switching valve Vw2 in the reverse travel stage R.

[0024] In this embodiment, the first auxiliary hydraulic supply valve Vs1 is a linear solenoid valve, and when the first switching valve Vw1 is switched to the lock-up on side, it functions as a so-called lock-up solenoid valve (SLU) that supplies hydraulic pressure to the direct-drive clutch CD1 to generate engagement pressure. The check valve Vc1 is a check valve that keeps the oil flow in a constant direction and restricts backflow. The manual valve MV is a switching valve that switches the line pressure supply path according to the selection of the shift range. The first auxiliary hydraulic supply valve Vs1 also functions as an auxiliary hydraulic supply device 24 that supplies auxiliary hydraulic pressure to the first linear solenoid valve SL1, etc. The third auxiliary hydraulic supply valve Vs3 is an auxiliary hydraulic supply device 24 that supplies auxiliary hydraulic pressure to the third linear solenoid valve SL3, etc.

[0025] The shift range includes, for example, non-driving ranges such as parking range (P range) and neutral range (N range), and driving ranges such as reverse driving range (R range) and forward driving range (D range). One of these shift ranges is selected by the driver operating the shift lever or by the vehicle control device performing automatic driving. The forward driving range (D range) may include a brake range (B range) in which the engine braking effect is prioritized, and a sport range (S range) in which the responsiveness of the accelerator pedal is prioritized. In this embodiment, when the neutral range (N range) is selected, a neutral position N is formed and the transmission 20 is in a neutral state. Also in this embodiment, when the parking range (P range) is selected, a neutral position N is formed and the transmission 20 is in a neutral state.

[0026] Here, the double-piston type friction engagement element CL is referred to as the target engagement element DP. The gear shift stage formed by engaging the target engagement element DP is referred to as the target gear shift stage H. In this embodiment, the automatic transmission 10 is capable of switching between at least a first travel range and a second travel range, and the transmission 20 includes a second engagement element SC, which is a friction engagement element CL other than the target engagement element DP and is in a released state when the second travel range is selected, and a switching valve that shuts off the hydraulic pressure supplied to the second piston B2b when the first travel range is selected. In the illustrated example, the direct-drive clutch CD1 functions as the second engagement element SC that is in a released state when the second travel range is selected. In this embodiment, the second switching valve Vw2 functions as a switching valve that shuts off the hydraulic pressure supplied to the second piston B2b when the first travel range is selected. Furthermore, the hydraulic pressure controlled by the switching control valve Vn1, which is the second control valve VL2, is supplied to the direct-drive clutch CD1, which is the second engagement element SC, when the first travel range is selected, and to the second piston B2b when the second travel range is selected. Preferably, the first travel range is the forward travel range (D range), and the second travel range is the reverse travel range (R range).

[0027] Figures 6 to 8 show a simplified representation of the hydraulic circuit 25 in the power transmission state. In Figures 6 to 8, the oil passages supplied with hydraulic pressure from the hydraulic pressure generator 22 are shown with thick lines. The second linear solenoid valve SL2, the fourth linear solenoid valve SL4, and the fifth linear solenoid valve SL5 are omitted.

[0028] Figure 6 shows a simplified hydraulic circuit 25 when the forward driving range (D range) is selected with the direct-drive clutch CD1 engaged. In Figure 6, the first clutch C1 is engaged by the control of the first linear solenoid valve SL1, one of the multiple control valves VL. Also, hydraulic pressure is supplied to the first piston B2a by the control of the sixth linear solenoid valve SL6, engaging the second brake B2. That is, the first stage 1st is formed. The first switching valve Vw1 shown in Figure 6 is set to the lock-up on side by the signal pressure from the switching control valve Vn1. In this case, hydraulic pressure controlled by the first auxiliary hydraulic supply valve Vs1 is supplied to the direct-drive clutch CD1.

[0029] As shown in Figure 6, in the D range, the signal pressure from the manual valve MV causes the second switching valve Vw2 to shut off the hydraulic pressure supplied to the second piston B2b (i.e., the off side). The switching control valve Vn1 can output a signal pressure to switch the second switching valve Vw2 to the side where hydraulic pressure is supplied to the second piston B2b (i.e., the on side), but since the signal pressure from the manual valve MV is higher than the signal pressure from the switching control valve Vn1, the second switching valve Vw2 is kept in the off side.

[0030] Figure 7 shows a simplified representation of the hydraulic circuit 25 when the reverse travel range (R range) is selected. In Figure 7, the third clutch C3 is engaged by the control of the third linear solenoid valve SL3, one of the multiple control valves VL. In addition, hydraulic pressure is supplied to the first piston B2a by the control of the sixth linear solenoid valve SL6. Furthermore, the second switching valve Vw2 is switched to the ON position by the switching control valve Vn1, and hydraulic pressure is supplied to the second piston B2b from the manual valve MV. In other words, the reverse travel stage R is formed.

[0031] As shown in Figure 7, in the R range, the signal pressure from the manual valve MV causes the first switching valve Vw1 to shut off the hydraulic pressure supplied to the direct-drive clutch CD1 (i.e., the lock-up off side). The switching control valve Vn1 can output a signal pressure to switch the first switching valve Vw1 to the side where hydraulic pressure is supplied to the direct-drive clutch CD1 (i.e., the lock-up on side), but since the signal pressure from the manual valve MV is higher than the signal pressure from the switching control valve Vn1, the first switching valve Vw1 is maintained in the lock-up off side.

[0032] As a result, the signal pressure output from the switching control valve Vn1 switches the first switching valve Vw1 in D range and the second switching valve Vw2 in R range. Therefore, the hydraulic pressure controlled by the switching control valve Vn1 is the hydraulic pressure supplied to the direct-drive clutch CD1 in D range (in this example, the hydraulic pressure controlled by the first auxiliary hydraulic pressure supply valve Vs1), and in R range, the hydraulic pressure supplied from the manual valve MV to the second piston B2b (in this example, the hydraulic pressure supplied from the hydraulic pressure generator 22).

[0033] Figure 8 shows a state in which the switching control valve Vn1 is faulty in the hydraulic circuit 25 when the R range is selected. When the reverse travel stage R is formed normally in the R range, as shown in Figure 7, the second brake B2 is engaged by the engagement pressure of both the first piston B2a and the second piston B2b, so a high transmission torque capacity is ensured. However, when the switching control valve Vn1 is faulty, as shown in Figure 8, the second switching valve Vw2 does not switch to the ON side, so the second brake B2 is engaged only by the engagement pressure of the first piston B2a, and the second brake B2 cannot generate a high transmission torque capacity. Therefore, when a high torque is input from the input member 20n, it exceeds the transmission torque capacity of the second brake B2, and the second brake B2 enters a slip engagement state.

[0034] If the control device 60 is in a specific fault condition where engagement pressure is not generated in either the first piston B2a or the second piston B2b, it will consider the piston that generates engagement pressure as the normal piston and perform torque limiting control S10 to limit the torque Tn transmitted from the drive source 12 to the input member 20n to a limiting torque Tk set within the range in which the target engagement element DP can transmit the torque in a directly engaged state by the engagement pressure of the normal piston.

[0035] In this embodiment, the upper limit of the torque Td1 that the target engagement element DP can transmit in a directly engaged state by the engagement pressure of a normal piston is set to the faulty transmission torque capacity Td1. MAX The gear ratio of the power transmission path from the input member 20n to the target engagement element DP is set to gear ratio ν. DP Therefore, the torque of the drive source 12 that can be transmitted within the range in which the second brake B2 (target engagement element DP) does not slip is the torque that can be transmitted during a failure, Tk. MAX This can be expressed by the following equation (1). Tk MAX =Td1 MAX / ν DP ...(1) The limiting torque Tk is the transmittable torque Tk during a failure. MAXThe following values ​​are set, preferably the torque Tk that can be transmitted during a failure. MAX It will be set to this.

[0036] Limiting the torque Tn transmitted from the drive source 12 to the input member 20n is achieved, for example, by controlling the drive source 12 to limit its output torque, or by slipping a clutch in the power transmission path from the drive source 12 to the input member 20n to limit the transmitted torque.

[0037] Figure 9 is a flowchart showing an example of torque limiting control S10. In torque limiting control S10, the control device 60 performs a specific fault determination process S11 to determine whether or not a specific fault condition exists in which engagement pressure is not generated for either the first piston B2a or the second piston B2b. In the example shown in Figure 2, the control device 60 is equipped with a specific fault determination unit 62, and the specific fault determination unit 62 executes the specific fault determination process S11.

[0038] In this embodiment, the control device 60 determines that a specific fault state exists if the control valve VL that controls the hydraulic pressure supplied to the target engagement element DP (in this case, the second brake B2) is malfunctioning. In this embodiment, it also determines that a specific fault state exists if the control valve VL that controls the hydraulic pressure supplied to the target engagement element DP cannot be controlled. Furthermore, in this embodiment, it also determines that a specific fault state exists if the control current or control voltage of the control valve VL that controls the hydraulic pressure supplied to the target engagement element DP shows an abnormal value. In the example shown in Figure 5, the control device 60 determines that a specific fault state exists if the control current or control voltage of the first control valve VL1 (sixth linear solenoid valve SL6) or the second control valve VL2 (switching control valve Vn1) shows an abnormal value.

[0039] In addition, in the present embodiment, the control device 60 determines that a specific failure state has occurred when either one of the second switching valve Vw2 and the second control valve VL2 (switching control valve Vn1) has failed. Further, the control device 60 determines that a specific failure state has occurred when the slip engagement state has occurred even though the second engagement element SC is controlled to be in the direct connection engagement state. In the illustrated example, the second engagement element SC, which is a friction engagement element other than the target engagement element DP and is in the released state in the case of the second travel range, is the direct connection clutch CD1.

[0040] In addition, in the present embodiment, the control device 60 determines that a specific failure has occurred when the target engagement element DP does not enter the released state or the like. The fact that the target engagement element DP does not enter the released state can be determined, for example, by the fact that the gear stage formed by the target engagement element DP entering the released state is not appropriately formed. In the present embodiment, the control device 6 determines that a specific failure has occurred even in such a case. For example, when the target engagement element DP is the second brake B2, the control device 60 determines that a specific failure state has occurred when the gear stages 2nd to 8th formed by the second brake B2 entering the released state are not appropriately formed.

[0041] In the present embodiment, the control device 60 is the rotation speed (min -1 ) of the input member 20n in FIG. 1 and the rotation speed (min -1 ) of the output member 20t. When the rotational speed difference, which is the difference between the two, is not within a predetermined range in the gear stage formed by the target engagement element DP entering the released state, it is determined that a specific failure state has occurred.

[0042] Returning to FIG. 9, when the control device 60 determines that no specific failure has occurred in the specific failure determination process S11, the control device 60 repeats the specific failure determination process S11 at a predetermined cycle. When it is determined that a specific failure has occurred in the specific failure determination process S11, a hydraulic pressure supply prohibition process S12 is performed. In the present embodiment, as shown in FIG. 2, the control device 60 includes a hydraulic pressure supply prohibition control unit 63, and the hydraulic pressure supply prohibition control unit 63 executes the hydraulic pressure supply prohibition process S12.

[0043] In the hydraulic supply prohibition process S12, the device 60 designates the piston that is in a faulty state where engagement pressure is not generated between the first piston B2a and the second piston B2b as the abnormal piston, and designates the control valve VL corresponding to the abnormal piston between the first control valve VL1 (sixth linear solenoid valve SL6) and the second control valve VL2 (switching control valve Vn1) as the abnormal control valve, and prohibits the supply of hydraulic pressure to the abnormal piston by the abnormal control valve while the torque limit control S10 is being executed. In the example shown in Figure 8, the abnormal piston is the second piston B2b, and the supply of hydraulic pressure to the second piston B2b is prohibited by the control of the switching control valve Vn1, which is the abnormal control valve.

[0044] Next, the control device 60 defines the driving range in which the target gear H can be selected as the target driving range, and the driving ranges other than the target driving range as the non-target driving range, and performs a target driving range determination process S13 to determine whether the selected shift range is within the target driving range. In the example shown in Figure 2, the control device 60 is equipped with a target driving range determination unit 64, and the target driving range determination unit 64 executes the target driving range determination process S13.

[0045] If the shift range selected in the target driving range determination process S13 is determined to be the target driving range, the control device 60 executes the input member torque limiting process S14. In the example shown in Figure 2, the control device 60 is equipped with an input member torque limiting control unit 65, and the input member torque limiting control unit 65 executes the input member torque limiting process S14. In the input member torque limiting process S14, the torque Tn transmitted from the drive force source 12 to the input member 20n is limited to a limit torque Tk or less, resulting in a torque limiting state (input member torque limiting ON).

[0046] If the shift range selected in the target driving range determination process S13 is determined not to be a target driving range, that is, if the shift range is an untarget driving range, the control device 60 executes the input member torque limit release process S15. In the example shown in Figure 2, the input member torque limit control unit 65 executes the input member torque limit release process S15. In the input member torque limit release process S15, the automatic transmission 10 is set to a torque limit release state (input member torque limit OFF) where the torque Tn transmitted from the drive force source 12 to the input member 20n is not limited to less than or equal to the limit torque Tk.

[0047] When the input member torque limiting process S14 or the input member torque limit release process S15 is executed, the control device 60 executes the power supply interruption determination process S16. In the power supply interruption determination process S16, the control device 60 determines whether or not the power supply from the vehicle power supply 11 to the control device 60 has been interrupted. In the example shown in Figure 2, the power supply interruption determination unit 66 executes the power supply interruption determination process S16. The detection of whether or not the power supply has been interrupted may be performed when the interruption of the power supply is decided, or when the power supply has been interrupted and then restarted.

[0048] If the power supply interruption determination process S16 determines that the power supply has not been interrupted, the control device 60 returns to the target driving range determination process S13. If the power supply interruption determination process S16 determines that the power supply has been interrupted, the control device 60 releases the prohibition on hydraulic supply to the abnormal piston by the abnormal control valve and terminates the torque limit control S10 with the automatic transmission 10 in the above torque limit release state. Note that the power supply interruption determination process S16 may also be executed in other cases, for example, when a fault diagnostic clearing process is performed on the control device 60.

[0049] According to the automatic transmission 10 described above, torque limiting control S10 is performed to limit the torque Tn transmitted from the drive source 12 to the input member 20n to less than or equal to a limiting torque Tk set within the range in which the target engagement element DP can transmit in a directly engaged state by the engagement pressure of the normal piston. Therefore, even in a specific fault condition in which engagement pressure is not generated in either the first piston B2a or the second piston B2b of the target engagement element DP, it is possible to engage the target engagement element DP using the normal piston that generates engagement pressure and to form a gear shift using the target engagement element DP. Furthermore, when forming a gear shift using such a target engagement element DP, torque limiting control S10 is performed to limit the torque Tn transmitted from the drive source 12 to the input member 20n to less than or equal to a limiting torque Tk set within the range in which the target engagement element DP can transmit in a directly engaged state by the engagement pressure of the normal piston. This makes it easier to avoid deterioration or failure of the target engagement element DP due to the continued slip engagement state of the target engagement element DP.

[0050] Furthermore, in the automatic transmission 10 described above, the piston that is in a faulty state where no engagement pressure is generated between the first piston B2a and the second piston B2b is designated as the abnormal piston, and the control valve VL corresponding to the abnormal piston between the first control valve VL1 (sixth linear solenoid valve SL6) and the second control valve VL2 (switching control valve Vn1) is designated as the abnormal control valve. During the execution of torque limit control S10, the control device 60 prohibits the supply of hydraulic pressure to the abnormal piston by the abnormal control valve. This prevents unintended engagement pressure from being generated in the abnormal piston due to the supply of hydraulic pressure, which would otherwise cause a control failure of the target engagement element DP.

[0051] The control device 60 defines the driving range in which the target gear H can be selected as the target driving range, and the driving range other than the target driving range as the excluded driving range. When the vehicle transitions from the target driving range to the excluded driving range, or when the power supply from the vehicle power supply 11 is interrupted, the control device 60 terminates the torque limit control S10. This allows for a proper recovery from the state in which the torque limit control S10 is being performed.

[0052] The automatic transmission 10 is capable of switching the shift range between at least a first travel range and a second travel range. The transmission 20 includes a second engagement element SC (direct clutch CD1) which is a friction engagement element CL other than the target engagement element DP and is in a released state in the second travel range, and a second switching valve Vw2 which shuts off the hydraulic pressure supplied to the second piston B2b in the first travel range. The hydraulic pressure controlled by the second control valve VL2 (switching control valve Vn1) is supplied to the second engagement element SC (direct clutch CD1) in the first travel range and to the second piston B2b in the second travel range. A specific fault condition occurs if either the second switching valve Vw2 or the second control valve VL2 fails. Therefore, if either the second switching valve Vw2 or the second control valve VL2 fails, the engagement pressure of the second piston B2b will not be generated. However, if either the second switching valve Vw2 or the second control valve VL2 fails, a specific fault condition will occur, allowing the torque limit control S10 to be started appropriately.

[0053] The control device 60 determines that a specific fault condition exists if the second engagement element SC (direct-drive clutch CD1) enters a slip-engaged state despite being controlled to be in a direct-engaged state. Therefore, the specific fault condition can be determined based on the engagement state of the second engagement element SC (direct-drive clutch CD1) without having to set the target engagement element DP to an engaged state. Consequently, torque limit control S10 can be started promptly.

[0054] [Other Embodiments] Next, other embodiments of the automatic transmission 10 will be described.

[0055] (1) In the above embodiment, the case in which the automatic transmission 10 is mounted on a vehicle equipped with a power source 12 such as a rotating electric machine was described as an example. Here, the power source 12 is not limited to a rotating electric machine, but may be an internal combustion engine, or a hybrid of an internal combustion engine and a rotating electric machine. That is, the vehicle may be an automobile with only an internal combustion engine as the power source 12, a hybrid automobile with an internal combustion engine and a rotating electric machine as the power source 12, or an electric automobile. Furthermore, this automatic transmission 10 may be mounted on a vehicle other than an automobile.

[0056] (2) In the above embodiment, a configuration was described as in which the first clutch C1 to the fourth clutch C4 and the first brake B1 are controlled by the first linear solenoid valve SL1 to the fifth linear solenoid valve SL5, respectively. However, it is not essential that the friction engagement element CL and the control valve VL correspond one-to-one in this manner. For example, a configuration in which multiple friction engagement elements CL are controlled by a combination of one linear solenoid valve and a switching valve is also possible.

[0057] (3) In the above embodiment, a configuration in which the control device 60 performs a hydraulic supply prohibition process S12 to prohibit the supply of hydraulic pressure to the abnormal piston by the abnormal control valve while the torque limit control S10 is being executed was described as an example. However, the configuration is not limited to such a configuration, and for example, the hydraulic supply prohibition process S12 may not be executed. Also, in the above embodiment, a configuration in which the control device 60 enters a torque limit release state when it transitions from the target driving range to an outside driving range, or when the power supply from the vehicle power supply 11 is interrupted was described as an example. However, the configuration is not limited to such a configuration, and for example, the torque limit state may continue even when it transitions to an outside driving range.

[0058] (4) In the above embodiment, a configuration in which the first auxiliary hydraulic supply valve Vs1, which functions as an auxiliary hydraulic supply device 24, supplies auxiliary hydraulic pressure to the first linear solenoid valve SL1 was described as an example. However, the configuration is not limited to such a configuration, and for example, the first auxiliary hydraulic supply valve Vs1 may not function as an auxiliary hydraulic supply device 24 to the linear solenoid valve.

[0059] (5) The configurations disclosed in the embodiments described above can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. With regard to other configurations, the embodiments disclosed herein are merely illustrative in all respects. Therefore, various modifications can be made as appropriate without departing from the spirit of this disclosure. [Industrial applicability]

[0060] The technology disclosed herein can be used in vehicles equipped with an automatic transmission. [Explanation of symbols]

[0061] 10: Automatic transmission, 11: Vehicle power supply, 12: Drive source, 20: Transmission, 20n: Input component, 20t: Output component, 60: Control device, B2: Second brake (target engagement element DP), B2a: First piston, B2b: Second piston, CD1: Direct-drive clutch (second engagement element SC), SL6: Sixth linear solenoid valve (first control valve VL1), Vn1: Switching control valve (second control valve VL2), Vw2: Second switching valve (switching valve)

Claims

1. An automatic transmission comprising: a transmission device that transmits the rotation of an input member driven by a power source to an output member at a gear ratio of one of several gear stages; and a control device that controls the transmission device, The transmission comprises a plurality of friction engagement elements and a plurality of control valves for controlling the engagement state of the plurality of friction engagement elements, and a plurality of gear stages are formed according to the engagement state of the plurality of friction engagement elements. The target engagement element is a double-piston type friction engagement element, which is one of the plurality of friction engagement elements and comprises a first piston operated by hydraulic pressure controlled by a first control valve, which is a first control valve, and a second piston operated by hydraulic pressure controlled by a second control valve, which is a second control valve, and is engaged by the engagement pressure of at least one of the first piston and the second piston. The gear shift stage formed by engaging the aforementioned target engagement element is designated as the target gear shift stage. The control device is In a specific fault condition where engagement pressure is not generated in either the first piston or the second piston, the piston that generates engagement pressure is considered the normal piston. An automatic transmission that performs torque limiting control to limit the torque transmitted from the driving force source to the input member to a limit torque set within a range that the target engaging element can transmit in a directly engaged state by the engagement pressure of the normal piston.

2. The piston that is in a faulty state where no engagement pressure is generated between the first piston and the second piston is designated as the faulty piston, and the control valve that corresponds to the faulty piston between the first control valve and the second control valve is designated as the faulty control valve. The automatic transmission according to claim 1, wherein the control device prohibits the supply of hydraulic pressure to the abnormal piston by the abnormal control valve while the torque limiting control is being performed.

3. The driving range in which the aforementioned target gear can be selected is designated as the target driving range, and the driving ranges other than the aforementioned target driving range are designated as the excluded driving range. The automatic transmission according to claim 1, wherein the control device terminates the torque limiting control when it moves from the target driving range to the non-target driving range, or when the power supply from the vehicle power source is interrupted.

4. The aforementioned automatic transmission is capable of switching between at least a first driving range and a second driving range. The transmission includes a second engagement element, which is a friction engagement element other than the target engagement element and is in a released state in the second travel range, and a switching valve that shuts off the hydraulic pressure supplied to the second piston in the first travel range. The hydraulic pressure controlled by the second control valve is supplied to the second engagement element in the first travel range and to the second piston in the second travel range. The automatic transmission according to any one of claims 1 to 3, wherein the control device determines that the specific fault condition is present when either the switching valve or the second control valve fails.

5. The automatic transmission according to claim 4, wherein the control device determines that the specific fault condition is present if the second engagement element enters a slip engagement state despite being controlled to a direct engagement state.

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