Hydraulic control device of automatic transmission

Abstract

To provide a hydraulic control device of an automatic transmission which can suppress the damage of an oil pump while suppressing an erroneous operation of a fuel safe valve which is arranged at a hydraulic control circuit.SOLUTION: (a) After gear change control of an automatic transmission 16 is executed, line pressure gradual reduction control for gradually reducing prescribed line pressure PL which has been temporarily boosted during the gear change control of the automatic transmission 16, and returning the line pressure to original pressure is executed. (b) During the execution of the line pressure gradual control, engagement pressure excess control for controlling engagement pressure supplied to a fuel safe valve 74 from solenoid valves SL1 to SL5 so as to become the line pressure PL or lower is executed. By this constitution, a loss (fuel consumption and electricity consumption accompanied by the drive of an oil pump 40) of the oil pump 40 can be suppress while suppressing an erroneous operation of the fuel safe valve 74 provided at a hydraulic control circuit 60.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a hydraulic control device for an automatic transmission in which a predetermined gear shift stage is selectively established from among a plurality of gear shift stages. [Background technology]

[0002] There is known a hydraulic control device for an automatic transmission having a plurality of hydraulic friction engagement devices (hereinafter referred to as "gear-shift engagement devices") to which output pressures of a plurality of solenoid valves provided in a hydraulic control circuit are respectively supplied, and a predetermined number of the gear-shift engagement devices are engaged by supplying engagement pressure as output pressure from a predetermined number of the plurality of solenoid valves, thereby selectively establishing a predetermined gear shift stage from a plurality of gear shift stages. For example, one such device is described in Patent Document 1. In the hydraulic control device described in Patent Document 1, in the gear-shift engagement device having a hydraulic switch provided in an oil passage, the indicated pressure of the solenoid valve that supplies the engagement pressure when gear shifting is not being performed is set lower than the line pressure, thereby preventing the hydraulic switch from being affected by oil vibrations of the line pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-106433 A Summary of the Invention [Problem to be solved by the invention]

[0004] During the shift control of the automatic transmission, the amount of hydraulic oil supplied to the shift engagement device increases, so that the line pressure is temporarily increased. After the shift control, the line pressure, which was temporarily increased in order to suppress the loss of the oil pump, is gradually decreased and returned to the original state. Moreover, the engagement pressure supplied to the engaged one of the shift engagement devices during the shift control is set to the maximum pressure after the shift control. In this way, after the shift control, the engagement pressure supplied to the shift engagement device is set to the maximum pressure, while the line pressure is gradually decreased. In addition, in order to prevent a shock when the shift engagement device is switched from an engaged state to a released state when the shift range is switched from the D range to the N range, the shift engagement device has a back pressure characteristic that makes it difficult for the supplied engagement pressure to be released. Due to this back pressure characteristic, there is a risk that the engagement pressure will exceed the line pressure and become high after the shift control. For example, in the case where a hydraulic control circuit is provided with a fail-safe valve supplied with line pressure that operates to select a normal connection state and output pressure of at least some of a plurality of solenoid valves that operate to select a fail connection state when an engagement pressure exceeding a predetermined number is supplied from the plurality of solenoid valves, the fail-safe valve may malfunction if the engagement pressure exceeds the line pressure after the shift control. Note that the hydraulic control device described in Patent Document 1 aims to suppress deterioration in durability of the hydraulic switch due to hydraulic vibration of the line pressure, and is not intended to suppress malfunction of the fail-safe valve provided in the hydraulic control circuit that executes the shift control of the automatic transmission.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a hydraulic control circuit for an automatic transmission that can suppress loss in the oil pump while suppressing malfunction of a fail-safe valve provided in the hydraulic control circuit. [Means for solving the problem]

[0006] The gist of the present invention is a hydraulic control device for an automatic transmission having a plurality of hydraulic friction engagement devices to which engagement pressures of a plurality of solenoid valves provided in a hydraulic control circuit are respectively supplied, and a predetermined gear shift stage is selectively formed from a plurality of gear shift stages by supplying a predetermined number of the engagement pressures from the plurality of solenoid valves to engage a predetermined number of the plurality of hydraulic friction engagement devices, wherein (a) the base pressures of the plurality of solenoid valves are each set to a predetermined line pressure, (b) a normal connection state in which the engagement pressures of at least some of the plurality of solenoid valves are supplied to the corresponding hydraulic friction engagement devices, and (c) a normal connection state in which the engagement pressures of at least some of the plurality of solenoid valves are supplied to the corresponding hydraulic friction engagement devices, (c) the predetermined line pressure, which is operated so that the normal connection state is selected, and at least a portion of the engagement pressure, which is operated so that the fail connection state is selected, are supplied to the fail safe valve; (d) after shift control of the automatic transmission, line pressure gradual reduction control is executed to gradually reduce the predetermined line pressure, which was temporarily increased during shift control of the automatic transmission, to its original state; and (e) during the line pressure gradual reduction control, engagement pressure transient control is executed to control the engagement pressure supplied from the plurality of solenoid valves to be equal to or lower than the predetermined line pressure. Effect of the Invention

[0007] According to the hydraulic control device for an automatic transmission of the present invention, (a) after the shift control of the automatic transmission, a line pressure gradual reduction control is executed to gradually reduce the predetermined line pressure, which was temporarily increased during the shift control of the automatic transmission, to the original state, and (b) during the line pressure gradual reduction control, an engagement pressure transient control is executed to control the engagement pressure supplied from the plurality of solenoid valves to the fail-safe valve so that it is equal to or lower than the predetermined line pressure. This suppresses malfunction of the fail-safe valve provided in the hydraulic control circuit and suppresses loss of the oil pump. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram of an automatic transmission to which the present invention is applied, where (a) is a schematic diagram of the automatic transmission, (b) is an engagement operation table explaining the relationship between the shift operation of the automatic transmission and combinations of the engagement and disengagement states of the shift engagement devices used therein, and (c) is a diagram explaining the configuration of a hydraulic control circuit related to the shift control of the automatic transmission. [Diagram 2] 4 is an example of a flowchart illustrating the control operation of the electronic control device shown in FIG. [Diagram 3] 3 is an example of a time chart when the flowchart of FIG. 2 is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. EXAMPLES

[0010] 1 is an explanatory diagram of an automatic transmission 16 to which the present invention is applied, where (a) is a schematic diagram of the automatic transmission 16, (b) is an engagement operation table explaining the relationship between the gear shift operation of the automatic transmission 16 and combinations of engagement and disengagement states of gear shift engagement devices used therein, and (c) is a diagram explaining the configuration of a hydraulic control circuit 60 related to gear shift control of the automatic transmission 16. Note that the automatic transmission 16 is configured approximately symmetrically with respect to an axis C, and the lower half of the axis C is omitted in FIG. 1(a).

[0011] 1(a), in a vehicle 10, a crankshaft 22, a torque converter 14, an input shaft 24, an automatic transmission 16, and an output gear 26 are connected in this order from the engine 12 side in a power transmission path between an engine 12, which is a power source, and a pair of drive wheels (not shown), and these are well-known components. The automatic transmission 16 is housed in a case 18, which is a non-rotating member.

[0012] The automatic transmission 16 is a planetary gear type multi-stage transmission that has a plurality of shifting engagement devices CB and performs so-called clutch-to-clutch shifting by switching one of the shifting engagement devices CB. The shifting engagement devices CB include clutches C1 and C2 and brakes B1, B2, and B3, which are a plurality of hydraulic friction engagement devices, and correspond to the "hydraulic friction engagement devices" in the present invention. The plurality of shifting engagement devices CB and the one-way clutch F1 are connected as shown in FIG. 1(a). In the automatic transmission 16, a plurality of gear stages with different gear ratios γ are formed by selectively engaging two of the plurality of shifting engagement devices CB. The "two" that are selectively engaged correspond to the "predetermined number" in the present invention. In the engagement operation table shown in FIG. 1(b), "○" indicates an engaged state, "◎" indicates an engaged state during engine braking, "△" indicates an engaged state only during driving, and "blank" indicates a released state. The gear ratio γ of the first gear 1st, which is the lowest gear, is the largest, and the gear ratio γ of the higher gears is smaller.

[0013] The hydraulic control circuit 60 is a hydraulic control circuit related to the shift control of the automatic transmission 16. The hydraulic control circuit 60 includes solenoid valves (for example, linear solenoid valves) SLT, SL1 to SL5. The hydraulic oil pumped from the oil pump 40 is adjusted by a relief type pressure regulating valve 64 to a line pressure PL [Pa]. The pressure regulating valve 64 adjusts the pressure according to a pilot pressure PSLT [Pa] supplied from the solenoid valve SLT. The line pressure PL is adjusted according to, for example, an input torque Tin [Nm] of the automatic transmission 16 or a throttle valve opening θth [%] which is a substitute value thereof. The line pressure PL is supplied to a manual valve 70 which is linked to the shift lever 50. When the shift lever 50 is operated to a forward drive position such as the "D" position, the manual valve 70 supplies a D range pressure PD (the same pressure as the line pressure PL) [Pa]. When the shift lever 50 is operated to the "R" position, i.e., the reverse drive position, the manual valve 70 supplies the R range pressure PR (the same pressure as the line pressure PL) [Pa] to the brake B3 via the shuttle valve 72. The modulator valve 68 uses the line pressure PL as the source pressure and supplies a constant modulator pressure PM [Pa] to the solenoid valve SLT etc., regardless of the line pressure PL.

[0014] The solenoid valves SL1 to SL5 are provided corresponding to the multiple gear shift engagement devices CB, respectively, and correspond to the "solenoid valve" in the present invention. The solenoid valves SL1 to SL5 use the line pressure PL as the base pressure, and are each controlled according to a hydraulic control signal Sp output from the electronic control device 90. Output pressures PC1 to PC2, PB1 to PB3 [Pa] (hereinafter referred to as "output pressures PC1, etc."), which are actual pressures output from the solenoid valves SL1 to SL5, are each independently controlled and supplied to the clutches C1, C2 and the brakes B1, B2, B3, respectively. Hereinafter, when the output pressures PC1, etc. are engagement pressures, they may be referred to as engagement pressures PC1 to PC2, PB1 to PB3, respectively. The engagement pressures refer to hydraulic pressures that bring the respective gear shift engagement devices CB into an engaged state at the output pressure PC1, etc.

[0015] The fail-safe valve 74 in the hydraulic control circuit 60 is a known one, and has a similar configuration to that shown in, for example, Fig. 6 of JP 2008-190667 A. The fail-safe valve 74 is supplied with a line pressure PL which operates to select a normal connection state described below, and output pressures PC1 and the like of the solenoid valves SL1-SL5 which operate to select a fail connection state described below when three or more engagement pressures, which is more than the above-mentioned "predetermined number" of two, are output from the solenoid valves SL1-SL5.

[0016] For example, during normal forward driving, the fail-safe valve 74 biases one or more spool valve elements 74b provided within the fail-safe valve 74 toward a normal position based on a spring 74a provided in the fail-safe valve 74 and the line pressure PL (or the D-range pressure PD which is the same pressure as the line pressure PL). When the spool valve element 74b is placed in the normal position, the fail-safe valve 74 is placed in a normal connection state. The "normal connection state" is a connection state in which the output pressures PC1, etc. of the solenoid valves SL1 to SL5 are supplied to the corresponding gear shift engagement devices CB.

[0017] In the event of an abnormality during forward travel, i.e., when engagement pressures are supplied from at least three of the solenoid valves SL1 to SL5, such as output pressure PC1, the fail-safe valve 74 has the spool valve element 74b placed in the fail position against the biasing force of the spring 74a and the line pressure PL based on the supply of engagement pressures from the at least three. The spool valve element 74b being placed in the fail position places the fail-safe valve 74 in a fail-connected state. The "fail-connected state" is a connection state in which the supply of output pressures PC1, etc. to at least some of the shift engagement devices CB is cut off in a state other than a normal connection state, i.e., in an abnormal state. For example, in the fail-connected state, the supply of engagement pressures PB1 to PB3 to the brakes B1 to B3 is all cut off, and the pressure of the hydraulic oil supplied to the brakes B1 to B3 is set to the drain pressure EX.

[0018] In this way, the fail-safe valve 74 is switchable between a normal connection state and a fail connection state, and fails to operate based on the engagement pressure being simultaneously supplied from at least three of the output pressures PC1, etc., thereby preventing interlocking of the automatic transmission 16.

[0019] The electronic control device 90 includes a so-called microcomputer equipped with a CPU, RAM, ROM, an input / output interface, etc., and the CPU performs signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM, thereby executing shift control of the automatic transmission 16. The electronic control device 90 corresponds to the "hydraulic control device" of the present invention. The electronic control device 90 outputs a hydraulic control signal Sp to the hydraulic control circuit 60 in order to execute shift control. The hydraulic control signal Sp is a signal that specifies each command pressure, such as the output pressure PC1 of the solenoid valves SLT, SL1 to SL5.

[0020] Fig. 2 is an example of a flowchart explaining the control operation of the electronic control device 90 shown in Fig. 1(c). For example, this is executed when the automatic transmission 16 is shifted from the third gear 3rd to the second gear 2nd when the vehicle 10 decelerates and stops with the second start switch in the on state. When the second start switch is in the on state, the formation of the first gear 1st is prohibited in the automatic transmission 16, and one of the second gears 2nd to 6th is formed.

[0021] First, in step S10 (hereinafter, "step" will be omitted), it is determined whether or not the shift control has been performed. The shift control has been performed after the gear ratio γ has become that after the shift control. If the determination in S10 is NO, the process returns. If the determination in S10 is YES, in S20, control is started to gradually return the line pressure PL, which was temporarily increased during the shift control, to the original line pressure PL after the shift control (hereinafter, referred to as "line pressure decrease control"), and in S30, it is determined whether or not the line pressure decrease control has ended. If the determination in S30 is YES, in S40, control is executed to set the command pressure PB1_cmd[Pa] to the maximum command pressure PB1_max (hereinafter, referred to as "maximum pressure output control"), and the process returns.

[0022] If the determination in S30 is NO, in S50, the command pressure PB1_cmd is calculated by subtracting a predetermined first offset pressure Offset1 [Pa] from the command pressure PL_cmd [Pa], which is the command pressure of the line pressure PL, and in S60, it is determined whether the calculated value in S50 exceeds the guard pressure PB1_gd. The first offset pressure Offset1 is a predetermined offset pressure of the command pressure PB1_cmd that is determined in advance experimentally or by design so that the output pressure PB1 does not exceed the line pressure PL during the line pressure reduction control even when considering, for example, the temperature of the hydraulic oil and the exhaust pressure characteristics of the engagement device CB. The guard pressure PB1_gd is obtained by adding a predetermined second offset pressure Offset2 [Pa] to the minimum command pressure PB1_min of the command pressure PB1_cmd that can realize the engagement pressure PB1 that can achieve the engagement force required for the brake B1. The second offset pressure Offset2 is a predetermined offset pressure of the command pressure PB1_cmd, which is determined experimentally or by design, so that the engagement force required for the brake B1 is reliably achieved even when the temperature of the hydraulic oil and the engagement characteristics of the gear shift engagement device CB are taken into consideration. If the determination in S60 is NO, the command pressure PB1_cmd is calculated as the guard pressure PB1_gd in S70. If the determination in S60 is YES or after S70 is executed, the command pressure PB1_cmd calculated in S50 or S70 is output to the solenoid valve SL3 in S80, and S30 is executed again. The control of the command pressure PB1_cmd in S80 during the period until the determination in S30 becomes YES corresponds to the "engagement pressure transient control" in the present invention. In the engagement pressure transient control, when the command pressure PB1_cmd exceeds the guard pressure PB1_gd, the command pressure PB1_cmd is controlled so that the engagement pressure PB1 is equal to or lower than the line pressure PL. In the engagement pressure transient control of this embodiment, S60 to S70 are executed, but the present invention may be configured such that these steps are not executed. Since the switching response of the connection state of the fail-safe valve 74 is low, even if S70 is not executed and the engagement pressure PB1 exceeds the line pressure PL for a short period of time, the fail-safe valve 74 is unlikely to malfunction.

[0023] Fig. 3 is an example of a time chart when the flowchart of Fig. 2 is executed. In Fig. 3, the command pressure PB1_cmd and the output pressure PB1 according to this embodiment are indicated by solid lines, and the command pressure PB1_cmd and the output pressure PB1 according to the comparative example are indicated by dashed lines. The horizontal axis of Fig. 3 is time t [sec]. The comparative example differs from this embodiment in that the engagement pressure transient control is not executed after the shift control, and the maximum pressure output control is started immediately after the end of the shift control.

[0024] During the shift control, a line pressure increase control is executed to temporarily increase the line pressure PL. A line pressure decrease control is executed for a predetermined period (time t1 to t3) from the end of the shift control. The execution period T (= t3 - t1) of the line pressure decrease control is a period that is determined experimentally or by design in advance to suppress loss in the oil pump 40. After the line pressure decrease control is executed, the line pressure PL that was temporarily increased during the shift control is returned to its original state, and a line pressure output control is executed to adjust the line pressure according to, for example, the input torque Tin. During the shift control, an engagement pressure output control is executed to control the command pressure PB1_cmd to a constant pressure that engages the brake B1, and the output pressure PB1 gradually increases.

[0025] In the comparative example, the maximum pressure output control is executed immediately after the shift control ends. This causes the engagement pressure PB1 to rise to the line pressure PL. Incidentally, in order to counter the shock caused when the shift engagement device CB is switched from an engaged state to a released state when the shift range is switched from the D range to the N range, the shift engagement device CB has a back pressure characteristic that makes it difficult for the supplied engagement pressure to be released compared to the drop in the line pressure PL. Therefore, the engagement pressure PB1 is difficult to drop compared to the drop in the line pressure PL, and the engagement pressure PB1 becomes higher than the line pressure PL during the period from time t1 to time t4. As a result, for example, even though the engagement pressures supplied to the fail-safe valve 74 are the two engagement pressures PC1 and PB1, the spool valve element 74b may be set to the fail position. If the supply of the engagement pressures PB1 to PB3 to the brakes B1 to B3 is all cut off due to the malfunction of the fail-safe valve 74, the brake B1 may be switched from an engaged state to a released state when the vehicle is stopped, causing a shock. The longer the execution period T, the greater the loss in the oil pump 40. The shorter the execution period T, the more likely the fail-safe valve 74 is to malfunction.

[0026] In this embodiment, while the line pressure gradually reducing control is being executed, the engagement pressure transient control is executed. While the line pressure output control is being executed, the maximum pressure output control is executed. By the engagement pressure transient control, the engagement pressure PB1 is reliably controlled to be equal to or lower than the line pressure PL during the period from time t1 to time t2, so that the malfunction of the fail-safe valve 74 is suppressed.

[0027] According to this embodiment, (a) after the shift control of the automatic transmission 16, line pressure gradual reduction control is executed to gradually reduce the line pressure PL, which was temporarily increased during the shift control, to the original level, and (b) during the line pressure gradual reduction control, engagement pressure transient control is executed to control the engagement pressure PB1 supplied from the solenoid valve SL3 to the fail-safe valve 74 to be equal to or lower than the line pressure PL. This suppresses malfunction of the fail-safe valve 74 provided in the hydraulic control circuit 60, while suppressing losses in the oil pump 40 (fuel consumption and electricity consumption associated with driving the oil pump 40).

[0028] It should be noted that the above is an embodiment of the present invention, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0029] In the above embodiment, the 2nd start switch is in the on state and the automatic transmission 16 is shifted from the third gear 3rd to the second gear 2nd, but the present invention is not limited to this. [Explanation of symbols]

[0030] 16: automatic transmission, 60: hydraulic control circuit, 74: fail-safe valve, 90: electronic control device (hydraulic control device), CB: gear shift engagement device (hydraulic friction engagement device), PL: line pressure, SL1 to SL5: solenoid valves (solenoid valves)

Claims

[Claim 1] A hydraulic control device for an automatic transmission having a plurality of hydraulic friction engagement devices to which engagement pressures of a plurality of solenoid valves provided in a hydraulic control circuit are respectively supplied, and a predetermined gear shift stage is selectively established from a plurality of gear shift stages by supplying a predetermined number of the engagement pressures from the plurality of solenoid valves to engage the predetermined number of the plurality of hydraulic friction engagement devices, The source pressure of each of the plurality of solenoid valves is set to a predetermined line pressure, a fail-safe valve capable of switching between a normal connection state in which at least some of the engagement pressures of the plurality of solenoid valves are supplied to the corresponding hydraulic friction engagement devices and a fail-connection state in which the supply of the at least some of the engagement pressures to the corresponding hydraulic friction engagement devices is blocked; The predetermined line pressure that operates the valve so that the normal connection state is selected, and at least a portion of the engagement pressure that operates the valve so that a fail connection state is selected are supplied to the failsafe valve, After the shift control of the automatic transmission, a line pressure gradual reduction control is executed to gradually reduce the predetermined line pressure that was temporarily increased during the shift control of the automatic transmission to an original state, During the line pressure gradual reduction control, an engagement pressure transient control is executed to control the engagement pressure supplied from the plurality of solenoid valves to the fail-safe valve so that the engagement pressure is equal to or lower than the predetermined line pressure. A hydraulic control device for an automatic transmission comprising:

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