JP2007255672A - Automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure minimum travelling performance while reducing cost by optimizing a gear ratio with a main transmission device and a sub transmission device so as to be previously adaptable to an abnormal condition. <P>SOLUTION: To a first-speed gear ratio to a fifth-speed gear ratio with the main transmission device, five-stage total gear ratio with the sub transmission device is added. A low-speed range out of the added five-stage total gear ratio is set to be a total gear ratio where the main transmission device is fixed to first and second speeds to be increased at a sub gear ratio, and set in a speed range overlapped with third and fourth speed ranges. When a trouble occurs, the overlapped speed range is used for travel at a gear ratio close to the normal condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic transmission having a main transmission and a sub-transmission connected to the main transmission.

  2. Description of the Related Art In recent years, in vehicles such as automobiles, in order to reduce fuel consumption while effectively using engine output, there is a tendency that a shift range width required for a transmission is widened, and the number of shift stages is increasing. For this reason, an automatic transmission has been developed that enables further multi-stages by connecting a sub-transmission to the main transmission, and further shifting the shift output shifted by the main transmission using the sub-transmission.

  In such an automatic transmission, backup at the time of failure is important, and various techniques for coping with an abnormality have been conventionally proposed.

  For example, in Patent Document 1, an operating pressure control circuit that is switched by a first electromagnetic valve means to a hydraulic circuit that controls supply and discharge of the operating pressure to a plurality of friction elements, and an operating pressure is regulated by a second electromagnetic valve means. A pressure regulation circuit is provided in parallel, and when the first solenoid valve means cannot be controlled, the second solenoid valve means performs shift control via the pressure regulation circuit, and when the second solenoid valve means cannot be controlled, the first solenoid valve means A technique for performing shift control via an operating pressure control circuit is disclosed.

Further, in Patent Document 2, a plurality of transmissions are combined to enable multi-stage shifting, and an actuator for shifting is attached to each transmission, and when the gears are switched by driving these actuators, When a malfunction is detected for any of the actuators, a technology for backing up the shift control when the actuator fails is disclosed by prohibiting switching from the current gear to the gear that is associated with the malfunctioning actuator. Yes.
Japanese Patent No. 3165259 JP 2001-304401 A

  However, the technique disclosed in Patent Document 1 requires two systems of a normal time and a failure time, which complicates the apparatus and increases costs. Similarly, the technique disclosed in Patent Document 2 requires two types of sub-transmissions, ie, a splitter with a small gear ratio and a range with a large gear ratio, which complicates the device and increases costs.

  The present invention has been made in view of the above circumstances, and the gear ratio between the main transmission and the sub-transmission is optimized in advance so as to be able to cope with an abnormality, and a minimum traveling property is ensured even in an abnormality while reducing costs. It is an object of the present invention to provide an automatic transmission that can be used.

  In order to achieve the above object, an automatic transmission according to the present invention is an automatic transmission that achieves a large number of speeds by connecting a sub-transmission to a main transmission, and sets a first gear ratio in the sub-transmission. The first gear ratio range of the entire automatic transmission that is output when the second gear ratio is set is equal to the second gear ratio range of the entire automatic transmission that is output when the second gear ratio is set in the auxiliary transmission. And when the sub-transmission device is in an abnormal state in which either the first gear ratio or the second gear ratio cannot be set, the sub-transmission device sets the first gear ratio. One of the ratio and the second transmission ratio is set.

  The automatic transmission according to the present invention is an automatic transmission that achieves a large number of shift stages by connecting a sub transmission to a main transmission, and the sub transmission includes a first friction engagement element and a second friction engagement element. A first gear ratio is set by fastening the first friction engagement element and releasing the second friction engagement element. The automatic transmission that is output when the second gear ratio is set by releasing the coupling element and fastening the second friction engagement element, and when the first gear ratio is set in the auxiliary transmission. The first transmission ratio range of the entire transmission is set to partially overlap the second transmission ratio range of the entire automatic transmission that is output when the second transmission ratio is set in the auxiliary transmission. And the sub-transmission device is either the first speed ratio or the second speed ratio. When it is impossible to set the abnormality, the auxiliary speed change device and sets the other one of the first gear ratio or the second speed ratio.

  According to the present invention, since the gear ratio between the main transmission and the sub-transmission is optimized in advance so as to be able to cope with an abnormality, the minimum travel is possible even when an abnormality occurs while reducing costs. , Can ensure safety.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 relate to an embodiment of the present invention, FIG. 1 is a schematic diagram showing a layout of each element of an automatic transmission, FIG. 2 is a skeleton diagram of an auxiliary transmission, and FIG. FIG. 4 is an explanatory diagram showing a hydraulic system of the auxiliary transmission, and FIG. 5 is a flowchart of a failure speed change backup process.

  In FIG. 1, reference numeral 10 denotes an automatic transmission connected to the engine 1. In this embodiment, an automatic transmission having a driving force distribution mechanism mounted on a four-wheel drive vehicle will be described as an example. The automatic transmission 10 includes a torque converter 16 having a lock-up clutch 15, a main transmission 20 disposed at the rear of the torque converter 16, and a center differential device that distributes driving force from the output from the main transmission 20. 50 and a sub-transmission switching device 60 connected to the center differential device 50.

  The main transmission 20 is a transmission that automatically switches between multiple speeds, and an existing transmission can be used. However, it is desirable that the transmission is practically a 3rd or higher speed transmission. Further, in this embodiment, the auxiliary transmission switching device 60 can select a two-stage gear ratio by using the center differential device 50 together, and the automatic transmission as a whole with respect to the gear ratio range of the main transmission device 20 can be selected. A sub-transmission device that expands the shift range is formed.

  As will be described later, the sub-transmission device using the center differential device 50 and the sub-transmission switching device 60 has a low-side sub-transmission ratio as the first transmission ratio and a high-side second transmission ratio. A first transmission ratio range in which the low-side auxiliary transmission ratio is applied to the main transmission ratio of the main transmission 20 as a total transmission ratio of the automatic transmission 10 as a whole. A second gear ratio range in which the high side gear ratio is applied to the main gear ratio can be obtained. These first and second gear ratio ranges are set so as to partially overlap each other. Usually, one of the overlapping portions is used and the other is used as a backup when an abnormality occurs.

  In the automatic transmission 10 having such an auxiliary transmission, the torque converter 16 is connected to the output shaft (crankshaft) of the engine 1 via the input shaft 2, and the input shaft 2 is connected to the main transmission 20. Has been. The output shaft 3 of the main transmission 20 is arranged coaxially with the input shaft 2, and is branched and connected to the front drive shaft 4 as the front wheel transmission shaft and the auxiliary transmission switching device 60 via the center differential device 50. Reference numeral 5 denotes an oil pump that supplies oil to the torque converter 16.

  The front drive shaft 4 is disposed in parallel to the input shaft 2 and the output shaft 3, and the rear end of the front drive shaft 4 is connected to the center differential device 50 via the reduction gear 6. Further, the front end of the front drive shaft 4 is connected to a front differential device (not shown), and an output shaft that supports the front wheel is connected to the front differential device.

  On the other hand, the output side of the auxiliary transmission switching device 60 is connected to a rear drive shaft 7 as a rear wheel transmission shaft. The rear drive shaft 7 is disposed coaxially with the output shaft 3 behind the output shaft 3, and is connected to a rear wheel output shaft that supports the rear wheels via a propeller shaft, a rear differential device, and the like (not shown). It is installed.

  In this embodiment, the main transmission 20 is mainly composed of a skeleton in which three sets of planetary gears of a front planetary gear 21, a mid planetary gear 22, and a rear planetary gear 23 are connected in series, and in addition, friction engagement such as a brake and a clutch. It is an automatic transmission of 5 steps forward and 1 step reverse provided with elements.

  As friction engagement elements of the main transmission 20, a front brake (FR / B) 24 and a one-way clutch (3rdOWC) 25 are provided for the front planetary gear 21. Further, with respect to the mid planetary gear 22 and the rear planetary gear 23, an input clutch (I / C) 26, a high & low reverse clutch (H & LR / C) 27, a one-way clutch (1stOWC) 28, a direct clutch (D / C) 29, A reverse brake (REV / B) 30 and a forward brake (FWD / B) 31 are provided.

  Specifically, a front brake 24 and a one-way clutch 25 are interposed in parallel between the sun gear 21 a of the front planetary gear 21 and the case side which is a fixed member, and the carrier 21 b of the front planetary gear 21 is connected to the rear planetary gear 23. It is connected to the internal gear 23c. Further, an internal gear 21 c of the front planetary gear 21 is connected to the input shaft 2, and further connected to an internal gear 22 c of the mid planetary gear 22 via the input clutch 26.

  The mid planetary gear 22 has a forward brake 31 interposed between the sun gear 22 a and the case side, and an internal gear 22 c is connected to the carrier 23 b of the rear planetary gear 23. The carrier 22 b of the mid planetary gear 22 is connected to the output shaft 3, and the main transmission output is transmitted from the carrier 22 b to the center differential device 50.

  In the rear planetary gear 23, a direct clutch 29 is interposed between the sun gear 23a and the carrier 23b, and a reverse brake 30 is interposed between the carrier 23b and the case side. Further, between the sun gear 23a of the rear planetary gear 23 and the sun gear 22a of the mid planetary gear 22, a high & low reverse clutch 27 and a one-way clutch 28 are interposed in parallel.

  Each of these friction engagement elements is supplied and discharged by a control valve body 70 housed in an oil pan and individually engaged / disengaged, and as shown in FIG. (However, as will be described later, in this embodiment, the shift stage of the five forward speeds and the reverse speed by the main transmission 20 is used as the shift stage of the five forward speeds and the reverse speed in the automatic transmission 10. ).

  In FIG. 3, ◯ indicates fastening, ◎ indicates that it is involved in torque transmission at power-on, and ◇ indicates that it is involved in torque transmission during coasting. Further, Δ indicates that the hydraulic pressure is supplied but there is no effect on the output, and Δ * indicates that the engagement is performed in a predetermined vehicle speed region.

  Schematically, in the first speed of the drive (D) range, the forward brake 32 is engaged to lock the sun gear 22a of the mid planetary gear 22, and from the input shaft 2 to the internal gear 22c of the front planetary gear 21, the carrier 22b, the rear The power is transmitted to the output shaft 3 through the internal gear 23c and the carrier 23b of the planetary gear 23 and the internal gear 22c and the carrier 22b of the mid planetary gear 22.

  In the second speed in the D range, the direct clutch 29 is engaged in addition to the forward brake 31, and the sun gear 23a and the carrier 23b of the rear planetary gear 23 rotate together to output power that is increased more than in the first speed.

  In the third speed of the D range, the forward brake 32 is released with respect to the second speed and the sun gear 22a of the mid planetary gear 22 is unlocked. Instead, the high & low reverse clutch 27 is engaged, and the sun gear 22a of the mid planetary gear 22 is engaged. Is integrally rotated with the sun gear 23a and the carrier 23b of the rear planetary gear 23, the speed is increased from the second speed.

  In the fourth speed of the D range, the input clutch 26 is further engaged with the third speed, the internal gear 22c of the mid planetary gear 22 rotates integrally with the sun gear 22a, and the input shaft 2 and the output shaft 3 are directly connected. Further, in the fifth speed of the D range, the front brake 24 is engaged with the fourth speed, the sun gear 22a of the front planetary gear 21 is locked, and the rotation of the input shaft 2 is accelerated and transmitted to the output shaft 3.

  In the reverse (R) range, the sun gear 21a of the front planetary gear 21 is locked when the front brake 24 is engaged, and the internal gear 22c of the mid planetary gear 22 and the carrier 23b of the rear planetary gear 23 are locked when the reverse brake 30 is engaged. . Further, since the sun gear 22a of the mid planetary gear 22 and the sun gear 22a of the rear planetary gear 23 are connected by the high & low reverse clutch 27 being engaged, the rear planetary gear 23 is reversed with respect to the front planetary gear 21, and the carrier of the mid planetary gear 22 is reversed. Reverse rotation power having a large gear ratio is output via 22 b and transmitted to the output shaft 3.

  On the other hand, the center differential device 50 is a compound planetary gear type differential device, and is a first sun gear 51 connected to the output shaft 3 and a second gear connected to the auxiliary transmission switching device 60 via the intermediate shaft 8. The first sun gear 52, the first pinion 53 meshing with the first sun gear 51, the second pinion 54 meshing with the second sun gear 52, and the first and second pinions 53, 54 are rotatable. And a carrier 55 that supports the shaft. The first and second pinions 53 and 54 are integrally connected, and the carrier 55 is connected to the reduction gear 6 of the front drive shaft 4, and the auxiliary transmission switching device 60 is connected via the intermediate shaft 9. It is connected to.

  Thus, when the driving force output from the output shaft 3 is transmitted to the first pinion 53 via the first sun gear 51, the second pinion 54 and the carrier 55 integrated with the first pinion 53. Torque is transmitted to the second sun gear 52 and the reduction gear 6 at a predetermined distribution ratio via the. At this time, the rotation difference between the second sun gear 52 and the reduction gear 6 is absorbed by the rotation and revolution of the first and second pinions 53 and 54.

  Further, in this embodiment, the auxiliary transmission switching device 60 is a multi-step provided between three sets of hydraulic multi-plate clutches, that is, the case side which is a fixed member and the second sun gear 52 of the center differential device 50. A brake (MS / B) 61, a transfer clutch 62 for limiting a differential between the center differential device 50 and the rear drive shaft 7, a direct clutch (D) provided between the multi-step brake 61 and the transfer clutch 62 / C_2) 63. Among these clutches, the clutches involved in the shift are the multi-step brake 61 and the direct clutch 63, and the sub-gear ratio is switched to two stages of high / low by setting the engagement / release state in opposite relations. be able to.

  More specifically, the center differential device 50 and the sub-transmission switching device 60 as the sub-transmission device are in a coupling relationship shown in FIG. In other words, the second sun gear 52 of the center differential device 50 is configured to output the power distributed to the intermediate shaft 8 formed on the intermediate shaft 8, and the intermediate shaft 9 is loosely fitted inside the intermediate shaft 8. The intermediate shaft 9 is integrally coupled to the carrier 55 through the connecting member 56 at the gap between the first and second sun gears 51 and 52. Further, the reduction gear 6 is coupled to the front end of the carrier 55 so as to output the power of the carrier 55.

  Further, in the auxiliary transmission switching device 60, drum members 64 and 65 are provided on the intermediate shaft 8 and the rear drive shaft 7, respectively, and a direct clutch 63 is interposed between the drum members 64 and 65. Further, a transfer clutch 62 is interposed between the intermediate shaft 8 and the drum member 65, and a multi-step brake 61 is interposed between the drum member 64 and the case side, and the direct clutch 63 and the transfer clutch 62 are The multi-step brake 61 and the multi-step brake 61 are overlapped and arranged coaxially.

  The multi-step brake 61, the transfer clutch 62, and the direct clutch 63 are hydraulically controlled by a control valve body 70, and the sub-transmission ratio is set to 2 by the sub-transmission switching device 60 with respect to the main transmission 20 of the five forward speeds and the one reverse speed. By switching to the stage, it is possible to newly add five forward speeds as a whole of the automatic transmission 10, but as described below, some of the ranges of the ten speed ratio ranges Overlapping is made 8 steps forward and 1 step backward. In addition, when an abnormality occurs, the overlapped shift speed is used to enable backup travel at a gear ratio approached at the normal time.

  That is, when the multi-step brake 61 is released and the direct clutch 63 is engaged and the sub-transmission ratio is set to the low side, the intermediate shaft 8 and the rear drive shaft 7 that output the driving force distributed from the center differential device 50 are connected to the drum. They are connected via the members 64 and 65, and the subtransmission ratio is in a direct connection state of 1. As a result, the gear ratio of the main transmission 20 is output as the total gear ratio of the automatic transmission 10, and a gear ratio of 3.540 to 0.834 can be obtained for the first to fifth gears. At this time, a differential limiting torque is generated in the transfer clutch 62 in accordance with the rear wheel slip or the like.

  On the other hand, when the direct clutch 63 is released and the multi-step brake 61 is engaged and the sub-transmission ratio is set to the high side, the rear drive shaft is connected via the intermediate shaft 9 and the transfer clutch 62 coupled to the carrier 55 of the center differential device 50. 7, the intermediate shaft 8 and the second sun gear 52 are locked, the differential function of the center differential device 50 is blocked, and the carrier 55 is rotated at an increased speed. The sub-transmission ratio at this time is a transmission ratio determined by the gear specifications of the center differential device 50, and a value obtained by multiplying the main transmission ratio by the main transmission 20 by the sub-transmission ratio is the total transmission ratio of the entire automatic transmission 10. Is output.

  For example, if the speed increase ratio ip of the center differential device 50 is assumed to be ip = 0.457, as shown in FIG. .834, a total gear ratio of 5.17 to 0.381 can be added. Of the added five-stage total transmission ratio, the range on the lower speed side than the sixth speed shown in FIG. 3 is the total transmission in which the main transmission 20 is fixed at the first speed and the second speed and the speed is increased at the auxiliary transmission ratio ip. The ratio is set to 1.617, 1.057, and is set to a shift range that overlaps the shift range of the third speed (1.417) and the fourth speed (1.00).

  This overlapping transmission range is normally used with the sub-transmission ratio set to either the low side or the high side. A gear ratio close to normal (normal) can be obtained. As described above, in the present embodiment, normally, the third gear ratio and the fourth gear speed of the main transmission 20 with the auxiliary gear ratio set to the low side are used as the gear ratio in the overlapping gear shift range.

  As a result, as the total transmission ratio of the automatic transmission 10, in addition to the first to fifth speeds (ie, the main transmission ratios 1 to 5) with the auxiliary transmission ratio set to the low side, the main transmission ratio is changed to the third speed to the fifth speed. By setting the transmission ratios 0, 673, 0.457, and 0.381, which are set and increased at the high side auxiliary transmission ratio ip, to 6th speed, 7th speed, and 8th speed, respectively, 1st speed to 8th speed The gear ratio close to the normal time (normal time) can be obtained using the overlapping gear shift range even when an abnormality occurs.

  The shift backup control at the time of abnormality is performed by an electronic control unit (TCU) 80 in FIG. 4 that controls each friction engagement element of the automatic transmission 10 via the control valve body 70. During normal times, the TCU 80 controls the gear position of the automatic transmission 10 via the control valve body 70 in accordance with a previously stored shift schedule, and at the same time, self-diagnose whether there is an abnormality.

  In this self-diagnosis, it is particularly important to detect abnormalities in the multi-step brake 61 and the direct clutch 63 of the auxiliary transmission switching device 60, so that it is possible to ensure that both of them are broken and interlocked. I try to avoid it. Specifically, the TCU 80 constantly monitors the hydraulic system of the auxiliary transmission switching device 60 so as to ensure a minimum travel even when either the multi-step brake 61 or the direct clutch 63 fails. Yes.

  The hydraulic system of the auxiliary transmission switching device 60 is shown in FIG. 4, and electromagnetic switching valves 71 and 72, linear solenoid valves 73 and 74, etc. provided in the control valve body 70 are provided for the multi-step brake 61 and the direct clutch 63, respectively. Hydraulic pressure is supplied via In addition, hydraulic switches 77 and 78 that are turned on at a specified control pressure are interposed in the hydraulic line 75 of the multi-step brake 61 and the hydraulic line 76 of the direct clutch 63, respectively. A signal is input to the TCU 80, and abnormality of the multi-step brake 61 and the direct clutch 63 due to the valve fixing of the linear solenoid valves 73 and 74 is diagnosed.

  The abnormality diagnosis of the multi-step brake 61 and the direct clutch 63 is mainly based on an OFF failure in which the brake or clutch is locked in a released state and cannot be engaged with a control instruction for outputting hydraulic pressure, and a control instruction for releasing hydraulic pressure. This applies to ON failures that cannot be released because the brake or clutch is fixed in the engaged state. These failures are caused by various causes such as an abnormality in the hydraulic system, failures in the electromagnetic switching valves 71 and 72 and the linear solenoid valves 73 and 74, and oil leakage and sticking of the multi-step brake 61 and the direct clutch 63 itself. However, in the end, it can be determined by the ON / OFF state of the hydraulic switches 77 and 78 in response to the control instruction, and the sub-transmission ratio by the sub-transmission switching device 60 detects an abnormality on the low side or the high side. In this case, the main transmission device 20 is fixed to a predetermined gear position to ensure safety while switching to the normal side sub-transmission ratio.

  The fixing of the gear position of the main transmission 20 is determined according to whether the secondary gear shift is on the high side or the low side. In order to avoid the risk of further failure, for example, when an abnormality occurs in which the sub-shift cannot be set to the high side, that is, when the direct clutch 63 is turned on or when the multi-step brake 61 is turned off, The main transmission 20 is fixed to a gear stage that has the smallest relative rotation between the elements.

  In this embodiment, when an abnormality that cannot set the sub-shift to the high side occurs (low failure; failure that is fixed to the low side), the sub-transmission switching device 60 is set to the low side and the main transmission 20 is directly connected. Fix to the 4th speed which is the stage. When the main gear ratio is fixed at the fourth speed, the input clutch 26, the high & low reverse clutch 27, and the direct clutch 63 are all engaged, and the gears of the three planetary gears 21, 22, and 23 rotate together. It can be said that it is the safest state.

  On the other hand, when an abnormality that cannot set the sub-shift to the low side occurs (high failure; failure that is fixed to the high side), that is, when the direct clutch 63 fails or the multi-step brake 61 fails. The main transmission 20 is fixed at the largest transmission ratio, that is, the first speed, so that reliable traveling is possible. However, as in this embodiment, the condition is that the low-side sub-transmission ratio is larger than the high-side sub-transmission ratio.

  If the main gear ratio in a high failure is fixed at the fourth speed as the gear ratio with the smallest relative rotation, the total gear ratio of the entire transmission becomes too small depending on the setting of the sub gear ratio, and the traveling can be maintained. May become difficult. However, whether or not it is possible to drive at a fixed speed of 4 at the time of a high failure depends on the output characteristics of the engine and the configuration of the main transmission, so fixing to the 4th speed (speed ratio with the smallest relative rotation) is not necessarily The present invention is not limited to a low failure, and can be applied to a high failure depending on conditions.

  Next, a description will be given of failure-time shift backup processing corresponding to ON failure and OFF failure of the direct clutch 63 and the multi-step brake 61 by the TCU 80 with reference to the flowchart of FIG.

  In this failure speed change backup process, first, in step S1, it is checked whether or not an instruction for driving the linear solenoid valve 73 for controlling the hydraulic pressure of the direct clutch (D / C_2) 63 to output the hydraulic pressure is output. As a result, when a hydraulic pressure output instruction has been issued, the process proceeds to step S2, in which a signal from a hydraulic switch (C hydraulic pressure SW) 77 for detecting the pressure in the hydraulic line 75 of the direct clutch 63 is read and the switch is turned on. Check for no.

  As a result, when the hydraulic switch 77 is ON, the prescribed hydraulic pressure is supplied to the direct clutch 63, and it is determined that the direct clutch 63 is operating normally, and the process proceeds to step S8, where the multi-step brake (MS / B) The failure determination of 61 is performed. On the other hand, when the oil pressure switch 77 is OFF, it is determined that the specified oil pressure is not supplied to the direct clutch 63 and the clutch cannot be engaged (direct clutch OFF failure), and the process proceeds from step S2 to step S3.

  In step S3, the multi-step brake 61 is turned on to set the auxiliary gear ratio to the high side, and in step S4, the main gear ratio of the main transmission 20 is fixed to the first speed. Then, the driver is warned of the occurrence of an abnormality, and the process shifts to fail-safe control to ensure traveling for limp home.

  On the other hand, if the hydraulic pressure output instruction to the direct clutch 63 is not output in step S1, the process proceeds from step S1 to step S5 to check whether the signal of the hydraulic switch 77 is OFF. As a result, when the hydraulic switch 77 is ON, it is determined that there is an abnormality that cannot be released while the clutch is engaged (direct clutch ON failure), and the process proceeds from step S5 to step S6.

  In step S6, the multi-step brake 61 is turned off to set the auxiliary gear ratio to the low side, and in step S7, the main gear ratio of the main transmission 20 is fixed to the fourth speed. In the same manner, the driver is warned of the occurrence of an abnormality and shifts to fail-safe control to ensure traveling for limp home.

  If the hydraulic switch 77 is OFF in step S5, the process proceeds from step S5 to step S8 and subsequent steps, and the multi-step brake 61 is diagnosed. In the diagnosis of the multi-step brake 61, first, in step S8, it is checked whether or not an instruction to output the hydraulic pressure by driving the linear solenoid valve 74 that controls the hydraulic pressure of the multi-step brake 61 is output.

  If a hydraulic pressure output instruction has been issued, the process proceeds to step S9 to read a signal from a hydraulic switch (B hydraulic pressure SW) 78 that detects the pressure in the hydraulic line 76 of the multi-step brake 61, and whether the switch is ON. Check for no. As a result, when the hydraulic switch 78 is ON, it is determined that the specified hydraulic pressure is supplied to the direct clutch 63 and is operating normally, and the process is terminated.

  On the other hand, when the hydraulic switch 78 is OFF, it is determined that the prescribed hydraulic pressure is not supplied to the multi-step brake 61 and the engagement is impossible (multi-step OFF failure), and the direct clutch 63 is turned on in step S10. After turning on and setting the auxiliary transmission ratio to the low side, the main transmission ratio of the main transmission 20 is fixed to the fourth speed in the above-described step S7.

  If the hydraulic pressure output instruction to the multi-step brake 61 is not output in step S8, the process proceeds from step S8 to step S11 to check whether the signal of the hydraulic switch 78 is OFF. When the hydraulic switch 78 is OFF, an instruction not to output hydraulic pressure to both the direct clutch 63 and the multi-step brake 61, that is, an instruction to release both the direct clutch 63 and the multi-step brake 61 is output by the TCU 80. Will be. When both the direct clutch 63 and the multi-step brake 61 are released, the auxiliary transmission switching device 60 cannot transmit the driving force input from the output shaft 3 of the main transmission 20 to the front drive shaft 4 and the rear drive shaft 7. Therefore, if such an instruction is output from the TCU 80, it is determined that there is some abnormality, the process proceeds to step S7, the speed is fixed to the fourth speed as the speed ratio with the smallest relative rotation, and the driver is warned of the occurrence of the abnormality. To do. On the other hand, if the hydraulic switch 78 is ON, it is determined that there is an abnormality that cannot be released while the brake is engaged (multistep ON failure), and the direct clutch 63 is turned OFF in step S12 to set the auxiliary gear ratio to the high side. Thereafter, in step S4, the main transmission ratio of the main transmission 20 is fixed to the first speed.

  As described above, in the present embodiment, the first and second gear ratio ranges obtained by applying the gear ratio of the sub-transmission that can be switched in two steps to the main transmission are set to partially overlap. Normally, one of the overlapping parts is used and the other is used as a backup when an abnormality occurs. Therefore, the gear ratio is optimized in advance so that it can cope with an abnormality, and at the same time the abnormality is reduced while reducing costs. Limiting travelability can be ensured. In addition, when an abnormality occurs, backup traveling at a gear ratio close to that at normal time is possible by using the overlapping gear ratio.

Schematic showing the layout of each element of the automatic transmission Skeleton diagram of auxiliary transmission Explanatory drawing which shows the engagement state of a gear shift position and a friction engagement element Explanatory drawing showing the hydraulic system of the auxiliary transmission Flowchart of gear shift backup process at failure

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Automatic transmission 20 Main transmission 50 Center differential apparatus 60 Sub transmission switching apparatus 61 Multi step brake 63 Direct clutch

Claims (9)

In an automatic transmission that achieves a large number of shift stages by connecting a sub-transmission to the main transmission,
The first transmission ratio range of the entire automatic transmission that is output when the first transmission ratio is set in the auxiliary transmission, and the output that is output when the second transmission ratio is set in the auxiliary transmission. Set so that the second gear ratio range of the entire automatic gear shift partially overlaps,
When the sub-transmission device is in an abnormal state where either the first gear ratio or the second gear ratio cannot be set, the sub-transmission device sets the first gear ratio or the second gear ratio. An automatic transmission characterized in that one of the other is set.   During normal operation, either the first speed ratio or the second speed ratio is selected and used in a range where the first speed ratio range and the second speed ratio range overlap. The automatic transmission according to claim 1.   When the sub-transmission device is in an abnormal state in which one of the first gear ratio and the second gear ratio cannot be set, the main transmission device is set to a gear stage that has a combination with the smallest relative rotation. The automatic transmission according to claim 1 or 2, characterized by the above.   When the first gear ratio is set to be larger than the second gear ratio, and when the first gear ratio cannot be set, the main transmission has the largest gear ratio. It sets so that it may become. The automatic transmission in any one of Claims 1-3 characterized by the above-mentioned. In an automatic transmission that achieves a large number of shift stages by connecting a sub-transmission to the main transmission,
The sub-transmission device has a first friction engagement element and a second friction engagement element,
By fastening the first frictional engagement element and releasing the second frictional engagement element, setting a first transmission ratio;
Releasing the first frictional engagement element and fastening the second frictional engagement element to set a second transmission ratio;
Output when the first gear ratio is set in the auxiliary transmission, and when the first gear ratio range of the entire automatic transmission is set, and when the second gear ratio is set in the auxiliary transmission. The second speed ratio range of the entire automatic transmission is set to partially overlap,
When the sub-transmission device is in an abnormal state where either the first gear ratio or the second gear ratio cannot be set, the sub-transmission device sets the first gear ratio or the second gear ratio. An automatic transmission characterized in that one of the other is set.   2. The first friction engagement element is fastened when the first friction engagement element cannot be fastened, and the main transmission is set to have the largest speed ratio. 5. The automatic transmission according to 5.   When it is abnormal that the first friction engagement element cannot be released, the second friction engagement element is released, and the main transmission is set to a gear stage that has the least relative rotation. The automatic transmission according to claim 5.   When it is abnormal that the second friction engagement element cannot be fastened, the first friction engagement element is fastened, and the main transmission is set to a gear stage that has the least relative rotation. The automatic transmission according to claim 5.   2. The first friction engagement element is released when the second friction engagement element cannot be released, and the main transmission is set to have the largest speed ratio. 5. The automatic transmission according to 5.

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