JP2005140215A - Hydraulic control of automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hydraulic control of an automatic transmission for driving a vehicle by achieving a specified transmission step, while avoiding interlock from occurring in the transmission mechanism. <P>SOLUTION: The hydraulic control of an automatic transmission comprises a solenoid valve SL1 for making a switching operation between a low-speed step selector-valve 51 and a high-speed step selector-valve 52. When the high-speed step is achieved, an engagement element C-2 is engaged all the time with the low-speed step selector-valve and the high-speed step selector-valve. At the time when a hydraulic-pressure detector S/W detects a hydraulic-pressure of a hydraulic-servo of at least three engagement elements, which cause interlock by application of hydraulic pressure of a hydraulic-servo 82 of the engagement element C-2, the solenoid valve is actuated to carry out a gear-shift, that is, when low-speed step is achieved, valve-selection is made to a specified transmission step on the side of the low-speed step, and when high-speed step is achieved, the valve-selection is made to a specified transmission step on the side of the high-speed step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an automatic transmission mounted on a vehicle, and more particularly to a hydraulic control device that controls an engagement element in the transmission mechanism.

In an automatic transmission mounted on a vehicle, a reduced speed rotation and a non-reduced speed rotation are input to a Ravigneaux type planetary gear unit, and two of six engagement elements including four clutches and two brakes are simultaneously engaged. There is one that achieves multi-speed shifting at eight forward speeds (see Patent Document 1).
JP 2001-182785 A

Further, in the hydraulic control device of the automatic transmission, a hydraulic pressure detection switch is attached to the hydraulic servos of all the engagement elements, and abnormal tie-ups of the engagement elements are detected by the hydraulic pressure detection switch to interlock the transmission mechanism. There is one that performs control to avoid this (see Patent Document 2).
Japanese Patent No. 2668359

  By the way, in the conventional hydraulic control, when the engagement element for achieving the low speed stage fails to the engaged state, the neutral speed up to a predetermined vehicle speed is prevented so that an engine overrev is not generated due to an excessive engine brake operation. There is a problem that the driving force cannot be obtained during this period.

  SUMMARY OF THE INVENTION Accordingly, the present invention generally provides a hydraulic control device for an automatic transmission that enables vehicle travel by achieving a predetermined shift stage while avoiding interlocking of the speed change mechanism due to tie-up of an engagement element. With a purpose. Another object of the present invention is to prevent an extreme upshift or downshift from occurring when a predetermined shift speed is achieved.

  To achieve the above object, the present invention provides a plurality of engagement elements that are selectively engaged to achieve a plurality of shift speeds, and a solenoid that supplies hydraulic pressure to the respective hydraulic servos of the engagement elements. In a hydraulic control device for an automatic transmission comprising an operation control valve and a hydraulic pressure detecting means for detecting the hydraulic pressure of each hydraulic servo, two engagements engaged to achieve a predetermined gear position on the low speed stage side Supply of hydraulic pressure to the hydraulic servo of the two engagement elements engaged to achieve a predetermined shift speed on the high speed stage side, and a low speed switching valve for switching supply / cutoff of hydraulic pressure to the hydraulic servo of the element A high-speed stage switching valve for switching off and a solenoid valve for switching the low-speed stage switching valve and the high-speed stage switching valve are provided, and the low-speed stage switching valve and the high-speed stage switching valve are provided with a high-speed switching valve. Of the engaging element that is always engaged when the stage is achieved By applying the hydraulic pressure of the pressure servo, the solenoid valve is actuated when the hydraulic pressure detection means detects the hydraulic pressure of the hydraulic servo of three or more engagement elements. And when the high speed is achieved, the speed is switched to a predetermined speed on the high speed side.

  According to the configuration of the present invention, the hydraulic servo hydraulic pressure of the engaging element that is always engaged when the high speed stage is achieved is applied to the low speed stage switching valve and the high speed stage switching valve, and both the switching valves are connected to the solenoid. By selectively switching with the valve, it is possible to switch to a predetermined shift stage on the low speed stage when the low speed stage is achieved, and to switch to a predetermined shift stage on the high speed stage when the high speed stage is achieved. Therefore, according to this configuration, the vehicle can be driven at a predetermined shift stage while avoiding the interlock of the transmission mechanism. Further, it is possible to prevent an extreme shift from occurring when shifting to a predetermined shift stage. Furthermore, since not only the high speed stage but also the low speed stage can be achieved, the driving force when the vehicle restarts can be sufficiently secured.

  A speed change mechanism according to the application of the present invention includes, as an engagement element, a low speed stage clutch that maintains a constant engagement state when a low speed stage is achieved, and a high speed stage clutch that maintains a constant engagement state when a high speed stage is achieved. Is done. The low speed stage switching valve is arranged in the supply oil path of the low speed stage clutch hydraulic servo, and the high speed stage switching valve is arranged in the supply oil path of the high speed stage clutch hydraulic servo.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a skeleton of a gear train of an automatic transmission of 8 forward speeds and 1 reverse speed as one application object of the present invention. As shown in the figure, this automatic transmission is a vertical type for a front engine and a rear drive, and includes a torque converter 2 with a lock-up clutch and a planetary gear transmission 1.

  The planetary gear transmission 1 is composed of a Ravigneaux type planetary gear unit G and a planetary gear G1 for speed reduction that inputs a reduced speed rotation to the planetary gear unit G. The planetary gear unit G includes a large-diameter sun gear S2, a small-diameter sun gear S3, a short pinion P3 that meshes with each other and meshes with the small-diameter sun gear S3, a long pinion P2 that meshes with the large-diameter sun gear S2, and a pair thereof. The carrier C3 that supports the pinion and the ring gear R3 that meshes with the long pinion P2. The planetary gear G1 for reduction includes a sun gear S1, a pinion P1 meshed with the sun gear S1, a pinion P1 ′ meshed with the pinion P1, a carrier C1 supporting both the pinions P1 and P1 ′, and a ring gear meshed with the pinion P1 ′. It consists of a double pinion planetary gear consisting of three elements R1.

  The small-diameter sun gear S3 in the planetary gear unit G is connected to the ring gear R1 of the reduction planetary gear G1 by a first clutch C-1 (hereinafter abbreviated as C1 clutch). The large-diameter sun gear S2 is connected to the ring gear R1 of the reduction planetary gear G1 by a third clutch C-3 (hereinafter abbreviated as C3 clutch), and a fourth clutch C-4 (hereinafter referred to as C4 clutch). It is connected to the carrier C1 of the reduction planetary gear G1 by abbreviation) and can be locked to the case 10 by a first brake B-1 (hereinafter abbreviated as B1 brake). Further, the carrier C3 is connected to the input shaft 11 by a second clutch C-2 (hereinafter abbreviated as C2 clutch), and a case by a second brake B-2 (hereinafter abbreviated as B2 brake). 10 can be locked to the case 10 by a one-way clutch F-1 arranged in parallel with the B2 brake. The ring gear R3 is connected to the output shaft 19. The reduction planetary gear G1 has its sun gear S1 fixed to the transmission case 10, the carrier C1 is connected to the input shaft 11, and is connected to the large-diameter sun gear S2 of the planetary gear unit G via the C4 clutch, and the ring gear R1 is connected to the C1 clutch. Is connected to the small-diameter sun gear S3 of the planetary gear unit G, and is connected to the large-diameter sun gear S2 of the planetary gear unit G via the C3 clutch.

  As described above, each of the clutches and brakes of the planetary gear transmission 1 configured as described above includes a hydraulic servo including a friction member and a piston / cylinder mechanism that engages / releases them. The control by the electronic control device and the hydraulic control device which will be described later is applied to each hydraulic servo by the hydraulic control device attached to the transmission case 10 based on the vehicle load in the speed range corresponding to the range selected by the driver. The friction member is engaged / released by the supply / discharge of hydraulic pressure, and the speed is changed.

  FIG. 2 is a speed diagram illustrating the operation of the planetary gear transmission 1 by engaging and releasing the clutches and brakes and the one-way clutch. In this speed diagram, the vertical axis indicates each shift element described above them, the gear ratio is indicated by the mutual width between the vertical axes, and the input rotational speed to the planetary gear transmission 1 is indicated by the length in the vertical axis direction. A speed ratio of 1 is shown. In the figure, the mark ● represents the engagement of the engagement element immediately indicated, and the mark ○ represents the output rotational speed ratio of the planetary gear transmission 1.

  In this gear train, in the present embodiment, the lower gear stage, which is the first to fourth gears, selectively selects other engagement elements based on the input of the reduced speed rotation to the small-diameter sun gear S3 by the engagement of the C1 clutch. This is achieved by simultaneously engaging the two. That is, the first speed (1ST) is achieved by automatic engagement of the one-way clutch F-1 corresponding to the engagement of the B2 brake. In this case, referring to FIG. 1, the rotation decelerated from the input shaft 11 via the reduction planetary gear G1 is input to the small-diameter sun gear S3 via the C1 clutch and is locked by the engagement of the one-way clutch F-1. As shown in FIG. 2, the reduced rotation with the maximum gear ratio of the ring gear R 3 is output to the output shaft 19.

  Next, the second speed (2ND) is achieved by simultaneous engagement of the B1 brake. In this case, referring to FIG. 1, the rotation reduced from the input shaft 11 via the reduction planetary gear G1 is input to the small-diameter sun gear S3 via the C1 clutch, and is applied to the large-diameter sun gear S2 locked by the engagement of the B1 brake. Taking the reaction force, the reduced rotation of the ring gear R3 is output to the output shaft 19. The reduction ratio at this time is smaller than the first speed (1ST) as shown in FIG.

  The third speed (3RD) is achieved by simultaneous engagement of the C3 clutch. In this case, referring to FIG. 1, the rotation reduced from input shaft 11 via reduction planetary gear G1 is simultaneously input to large-diameter sun gear S2 and small-diameter sun gear S3 via C1 clutch and C3 clutch, and planetary gear unit G is directly connected. Therefore, the rotation of the ring gear R3 having the same speed as the input rotation to both sun gears is output from the ring gear R3 as a reduced rotation with respect to the input rotation (speed ratio = 1) as shown in FIG.

  Further, the fourth speed (4TH) is achieved by simultaneous engagement of the C4 clutch. In this case, referring to FIG. 1, the rotation decelerated from the input shaft 11 via the reduction planetary gear G1 is input to the small-diameter sun gear S3 via the C1 clutch, and is input from the input shaft 11 via the C4 clutch on the other hand. The non-decelerated rotation is input to the large-diameter sun gear S2, and the rotation of the ring gear R3 in which the rotation of the intermediate speed between the two input rotations is slightly increased as compared with the decelerated rotation of the planetary gear for deceleration as shown in FIG. Is output as

  Next, in the present embodiment, the gear stage on the high speed side, which is the fifth to eighth speeds, selectively selects other engagement elements based on the input of non-decelerated rotation to the carrier C3 due to the engagement of the C2 clutch. This is achieved by simultaneous engagement. That is, the fifth speed (5TH) is achieved by simultaneous engagement of the C1 clutch. In this case, referring to FIG. 1, the rotation decelerated from the input shaft 11 via the reduction planetary gear G1 is input to the small-diameter sun gear S3 via the C1 clutch, and is input from the input shaft 11 via the C2 clutch on the other hand. The non-decelerated rotation is input to the carrier C3, and the rotation at an intermediate speed between the two input rotations is output as the rotation of the ring gear R3 slightly decelerated with respect to the input rotation as shown in FIG.

  Next, the sixth speed (6TH) is achieved by simultaneous engagement of the C4 clutch. In this case, referring to FIG. 1, non-decelerated rotation input from the input shaft 11 via the C4 clutch is input to the large-diameter sun gear S2, and on the other hand, non-decelerated input from the input shaft 11 via the C2 clutch. Since the rotation is input to the carrier C3 and the planetary gear unit G is directly connected, the rotation of the ring gear R3 at the same speed as the input rotation to the sun gear S2 and the carrier C3 is the input rotation (speed ratio = 1) as shown in FIG. ) Is output to the ring gear R3.

  Further, the seventh speed (7TH) is achieved by simultaneous engagement of the C3 clutch. In this case, referring to FIG. 1, the rotation reduced on the one hand from the input shaft 11 via the reduction planetary gear G1 is inputted to the large-diameter sun gear S2 via the C3 clutch, and on the other hand, inputted from the input shaft 11 via the C2 clutch. The non-decelerated rotation is input to the carrier C3, and the rotation of the ring gear R3 is output as a rotation slightly increased from the input rotation as shown in FIG.

  The eighth speed (8TH) is achieved by simultaneous engagement of the B1 brake. In this case, referring to FIG. 1, non-decelerated rotation is input from the input shaft 11 via the C2 clutch only to the carrier C3, and a reaction force is applied to the large-diameter sun gear S2 locked by the engagement of the B1 brake. The further increased rotation of the ring gear R3 as shown in FIG.

  The reverse (R) is achieved based on the engagement of the B2 brake. In this case, as another engagement element to be simultaneously engaged, either the C3 clutch or the C4 clutch can be selected according to the setting of the reverse gear ratio. When the C3 clutch is a simultaneous engagement element, referring to FIG. 1, the rotation reduced from the input shaft 11 via the reduction planetary gear G1 is input to the large-diameter sun gear S2 via the C3 clutch, and the B2 brake is engaged. A reverse rotation having a large gear ratio of the ring gear R3 taking a reaction force on the locked carrier C3 is output to the output shaft. Further, when the C4 clutch is a simultaneous engagement element, as can be seen with reference to FIG. 2, the reverse speed ratio increases in the reverse rotation direction by the amount that the rotation input to the large-diameter sun gear S2 becomes the non-deceleration rotation. However, the relationship between input and output elements is the same.

  Next, FIG. 3 shows the above-described relationship between the operation of the clutches and brakes in the planetary gear transmission 1 and the shift speed achieved thereby. In the figure, ◯ indicates engagement, and X indicates release. In this chart, a C3 clutch is used as a simultaneous engagement element during reverse (R).

  Next, in the gear train shown in FIG. 1, the configuration of the hydraulic control device for achieving each of the shift speeds shown in the operation chart of FIG. 3 will be described. FIG. 4 is a circuit diagram schematically showing the hydraulic control device. This hydraulic circuit is sucked up by an oil pump (not shown) as a hydraulic power source, and the hydraulic pressure discharged to the line pressure oil passage is regulated by a regulator valve, and is necessary for maintaining the engagement of the engagement element according to the running load of the vehicle A line pressure PL is created, and a circuit for supplying and discharging the line pressure to the hydraulic servos 81 to 86 of each engagement element directly or via a manual valve as a control base pressure is configured. The hydraulic circuit shown in FIG. 4 omits the illustration of each of the above valves, and supplies the hydraulic pressure directly supplied from the oil passage leading to the line pressure oil passage through the oil passage leading to the “D” range port of the manual valve. The oil pressure is indicated by D, and the oil pressure supplied from the oil passage leading to the “R” port is indicated by R.

  As shown in FIG. 4, this hydraulic circuit includes C1-C4 clutch hydraulic servos 81-84 and a maximum output when no solenoid signal is applied as a solenoid-operated control valve for controlling the hydraulic pressure supplied to each hydraulic servo. Linear solenoid valves SLC1 to SLC4, B1 brake hydraulic servo 85, linear solenoid valves SLB1 which are in an output state when a solenoid signal is applied as a solenoid operated control valve for controlling the hydraulic pressure supplied to the hydraulic servo, and B2 A brake hydraulic servo 86, a low speed switching valve 51, a high speed switching valve 52, a normally closed on / off solenoid valve SL1 that outputs a signal pressure for switching both switching valves, and each hydraulic servo An oil pressure switch S / W as an attached oil pressure sensor is provided as a main component. A switching valve 53 that switches the supply path between when the first-speed engine brake is achieved and when the reverse is achieved, a normally-closed on-off solenoid valve SL2 that outputs a solenoid signal pressure for switching, and a high-speed switching valve 52 And a shuttle valve 54 for selecting a signal pressure to be applied.

  Specifically, the oil supply path to the hydraulic servo 81 of the C1 clutch is connected to the out port of the low speed stage switching valve 51 via the linear solenoid valve SLC1. The low speed switching valve 51 is constituted by a spool valve, and C2 clutch servo pressure PC2 (the C2 clutch described later) to the other end (upper end in the figure) with respect to the application of the line pressure PL to one end (lower end in the figure) of the spool. The hydraulic pressure supplied to the hydraulic servo 82 and the signal pressure output from the solenoid valve SL1 are superimposed and the return spring load is applied (the direction of the load is indicated by a dotted arrow. This notation is the same for the other valves. )). The D range pressure is supplied to the import of the switching valve 51 for the low speed stage. Due to the relationship between this connection and the application of signal pressure, the low-speed stage switching valve always maintains the D range pressure communication state at the 1st to 4th speeds (the port communication state is indicated by a diagonal line rising to the right in the figure). When the 5th to 8th speed C2 clutch servo pressure PC2 and solenoid SL1 signal pressure are applied, the switching operation is performed against the application of the line pressure PL, the supply of the D range pressure is cut off, and the out port is connected to the drain EX. (The port communication state at this time is indicated by the slanting line on the right in the figure).

  The oil supply path to the hydraulic servo 84 of the C4 clutch is also connected to the out port of the low speed stage switching valve 51 through the linear solenoid valve SLC4. Accordingly, the supply and shutoff of the D range pressure via the low speed stage switching valve are performed simultaneously for the linear solenoid valve SLC1 and the linear solenoid valve SLC4.

  The oil supply path to the hydraulic servo 82 of the C2 clutch is connected to the oil supply path for the D range pressure via the high speed stage switching valve 52 and the linear solenoid valve SLC2 upstream thereof. The high-speed switching valve 52 is constituted by a spool valve, and is opposed to the C2 clutch servo pressure PC2 or reverse pressure R and the return spring load that are selectively applied to one end (lower end in the figure) of the spool via the shuttle valve 54. The switching operation is performed by applying the signal pressure of the solenoid valve SL1 to the other end (upper end in the figure). The high speed stage switching valve 52 has three imports including the communication of the C2 clutch hydraulic servo 82 to the linear solenoid valve SLC2, the import for the drain of the hydraulic servo 82 of the C2 clutch, the outport and the drain port. And four out ports and four drain EX ports. The port communication state of the high-speed switching valve 52 when the solenoid valve SL1 signal pressure is not applied is indicated by a right-downward oblique line, and the port communication state when the solenoid valve SL1 signal pressure is applied is indicated by a right-upward oblique line.

  The oil supply path to the hydraulic servo 83 of the C3 clutch is connected to the out port of the high speed switching valve 52 via the linear solenoid valve SLC3, and the import connected to this out port is connected to the supply oil path of the line pressure PL. Has been. With this connection, the line pressure PL is always supplied to the linear solenoid valve SLC3 that controls the hydraulic pressure of the hydraulic servo 83 of the C3 clutch except when the high-speed switching valve 52 is switched by applying the solenoid valve SL1 signal pressure. Is called.

  The supply oil path to the hydraulic servo 85 of the B1 brake is connected to the out port of the high speed switching valve 52 via the linear solenoid valve SLB1, and the import leading to this out port is connected to the supply oil path of the D range pressure. It is connected. Due to this connection relationship, the supply of the D range pressure to the linear solenoid valve SLB1 that controls the hydraulic pressure of the hydraulic servo of the B1 brake is always performed except when the high speed stage switching valve 52 is switched by the application of the solenoid valve SL1 signal pressure. . However, since the linear solenoid valve SLB1 is a normally closed valve that shuts off the hydraulic pressure output when the linear solenoid signal is cut off, unlike the linear solenoid valve for other clutches, the D range via the high speed switching valve 52 is used. The supply of pressure does not immediately become the supply of hydraulic pressure to the hydraulic servo 85.

  The supply oil path to the hydraulic servo 86 of the B2 brake is connected to the supply oil path of the reverse range pressure R and the out port of the high speed stage switching valve 52 via the switching valve 53. The switching valve 53 is a spool valve that is switched by applying an on / off solenoid valve SL2 signal pressure that opposes the load of the return spring. With this connection relationship, the reverse range pressure R is supplied to the hydraulic servo 86 of the B2 brake when the solenoid valve SL2 signal pressure is applied to the switching valve 53, and the high speed stage switching is performed when the solenoid valve SL2 signal pressure is not applied. The output hydraulic pressure regulated by the linear solenoid valve SLC2 supplied via the valve 52 is supplied. Further, the reverse prohibition (R prohibition) shown in FIG. 2 that prohibits the achievement of the reverse gear when the reverse gear is selected during forward travel at a predetermined vehicle speed (for example, 7 km / h or more) is the on / off solenoid valve SL2. The reverse range pressure R is achieved by shutting off the supply of the B2 brake to the hydraulic servo 86 by making the signal pressure non-applied.

  In the hydraulic circuit having the above-described configuration, when the first to fourth speeds are achieved, the port communication of the low-speed stage switching valve 51 is in the state of communication with the diagonal line rising to the right in the figure, and the port communication state of the high-speed stage switching valve 52 is the return. Only the load of the spring is in the state of slanting lines in the lower right direction in the figure. In this state, hydraulic pressure is supplied to all linear solenoid valves. Therefore, under this state, only the linear solenoid valve SLC1 is brought into a pressure regulation state by applying a solenoid signal to achieve the first speed, and in addition, the linear solenoid valve SLB1 is similarly brought into a pressure regulation state. Thus, the second speed by the two-element engagement is achieved, and the linear solenoid valve SLC3 is brought into the pressure regulation state, so that the third speed by the two-element engagement is also achieved, and the linear solenoid valve SLC4 is brought into the pressure regulation state. Thus, the fourth speed is also achieved by the two-element engagement.

  In any of these cases, when the servo pressure of the other engaging element is generated in addition to the above two elements, this is detected by the hydraulic switch S / W of the hydraulic servo, and the solenoid signal that the solenoid valve SL1 is turned on based on this is detected. Pressure output state. With this signal pressure output, the high-speed switching valve 52 is switched, the hydraulic pressure supply is cut off, and the interlock due to the engagement of three or more elements is prevented. On the other hand, although the low speed stage switching valve 51 is applied with the solenoid signal pressure of the solenoid valve SL1, the hydraulic servo pressure PC2 of the C2 clutch, which is the high speed stage engagement element, is not applied. Since the application cannot be overcome, the initial state is maintained. Therefore, when this state occurs due to the failure of the linear solenoid signal, the fourth speed is achieved by simultaneous engagement of the C1 clutch and the C4 clutch. This state is also established when all solenoid signals including the solenoid valve SL1 are off-failed. Therefore, at the time of solenoid signal all-fail, the fourth speed is naturally achieved, and the vehicle can be driven by the gear position. Further, since this state is achieved only by connecting the oil passage, it is established when the vehicle restarts.

  On the other hand, in the achieved state of the fifth to eighth speeds, the port communication of the low-speed stage switching valve 51 is in the state of the oblique line in the upper right direction in the figure, and the port communication state of the high-speed stage switching valve 52 is the application of the C2 clutch servo pressure PC2. And the load of the return spring is in the state of slanting lines in the lower right of the figure. Even in this state, hydraulic pressure is supplied to all the linear solenoid valves. Therefore, under this state, the pressure regulation state is maintained by applying a solenoid signal to the linear solenoid valve SLC2, and in addition to this, the linear solenoid valve SLC1 is similarly brought into the pressure regulation state. When the fifth speed is achieved and the linear solenoid valve SLC4 is in the pressure regulation state, the sixth speed is also achieved by the two-element engagement, and when the linear solenoid valve SLC3 is in the pressure regulation state, the two-element engagement is also achieved. The seventh speed is achieved, and the linear solenoid valve SLB1 is brought into the pressure regulation state, whereby the eighth speed is also achieved by the two-element engagement.

  In any of these cases, when a servo pressure of another element is generated in addition to the above two elements, this is detected by the hydraulic switch S / W of the hydraulic servo, and based on that, the solenoid valve SL1 is turned on to output a solenoid signal pressure. State. In this case, unlike when the low speed stage is achieved, the C2 clutch servo pressure PC2 is applied to the high speed stage switching valve 52, so that the high speed stage switching valve 52 is not switched by the solenoid signal pressure output from the solenoid valve SL1. . On the other hand, since the solenoid signal pressure of the solenoid valve SL1 is superimposed and applied to the already applied C2 clutch servo pressure PC2, the low-speed stage switching valve 51 is switched over by overcoming the application of the opposing line pressure PL to supply hydraulic pressure. It becomes a cut-off state. Therefore, when this state occurs due to the failure of the linear solenoid signal, the supply of the D range pressure is cut off for the hydraulic servo 82 of the B1 brake by closing the linear solenoid valve SLB1 of the B1 brake. The seventh speed is achieved by simultaneous engagement. This state is also established when all solenoid signals fail off. Therefore, at the time of solenoid signal all-fail, the seventh speed is naturally achieved, and the vehicle can be driven by the shift speed. However, since this state is established on the assumption that the C2 clutch servo pressure is applied, it is not maintained when the vehicle restarts after the C2 clutch servo pressure has once decreased, and the fourth speed is established for the reason described above. become.

  Thus, according to this embodiment, the hydraulic pressure of the hydraulic servo 82 of the C2 clutch which is always engaged when the fifth to eighth speeds are achieved is applied to the low speed switching valve 51 and the high speed switching valve 52 in advance. The two switching valves are selectively switched by the solenoid valve SL1 to switch to the fourth speed as a predetermined shift stage on the low speed stage side when the first to fourth speeds are achieved, and to the high speed when the high speed stage is achieved. It is possible to switch to the seventh speed as a predetermined gear position on the stage side. Therefore, according to this configuration, the vehicle can travel at the fourth speed or the seventh speed while avoiding interlocking of the speed change mechanism. Further, since the shift to the fourth speed is made from the first to third speed shells, and the shift to the seventh speed is made from the fifth to eighth speeds, it is possible to prevent an extreme shift from occurring. Furthermore, since the fourth speed of the low speed stage can be achieved instead of the seventh speed of the high speed stage, the driving force when the vehicle restarts can be sufficiently secured by establishing the fourth speed.

  Although the present invention has been described in detail with reference to one embodiment, the scope of application of the idea of the present invention is not limited to the illustrated transmission mechanism and hydraulic circuit, but is widely applied to hydraulic control of a general transmission mechanism. It is possible.

It is a skeleton figure which shows the gear train of the 8-speed automatic transmission controlled by the hydraulic control apparatus based on the Example of this invention. It is a speed diagram which shows the action | operation of a gear train. It is an action | operation chart which shows the action | operation of the gear train by a hydraulic control apparatus. It is a circuit diagram of a hydraulic control device.

Explanation of symbols

C-1 C1 clutch (engagement element)
C-2 C2 clutch (engagement element)
C-3 C3 clutch (engagement element)
C-4 C4 clutch (engagement element)
B-1 B1 brake (engaging element)
B-2 B2 brake (engaging element)
51 Low-speed stage switching valve 52 High-speed stage switching valve SL1 Solenoid valve 81-86 Hydraulic servo S / W Hydraulic switch (hydraulic detection means)

Claims (1)

A plurality of engagement elements selectively engaged to achieve a plurality of shift speeds, a solenoid-operated control valve for supplying hydraulic pressure to the respective hydraulic servos of the engagement elements, and the hydraulic pressures of the respective hydraulic servos In a hydraulic control device for an automatic transmission provided with a hydraulic pressure detecting means for detecting
A low-speed stage switching valve that switches between supplying and shutting off the hydraulic pressure to the hydraulic servo of the two engagement elements engaged to achieve a predetermined gear position on the low-speed stage side;
A high-speed stage switching valve that switches between supply and cut-off of hydraulic pressure to the hydraulic servo of two engagement elements engaged to achieve a predetermined shift stage on the high-speed stage side;
An engagement element that is always engaged with the low-speed stage switching valve and the high-speed stage switching valve when the high-speed stage is achieved. When the hydraulic pressure detecting means detects the hydraulic pressure of the hydraulic servos of three or more engaging elements, the solenoid valve is operated, and when the low speed stage is achieved, the low speed stage side is applied. A hydraulic control device for an automatic transmission, wherein the automatic transmission hydraulic pressure control device switches to a predetermined gear position, and switches to the predetermined gear position on the high speed side when the high speed stage is achieved.

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