Line pressure control device for automatic transmission

Description: TECHNICAL FIELD [Detailed description of the invention]

(Industrial application field) The present invention relates to a line pressure control device for an automatic transmission, particularly a device for appropriately controlling the line pressure during shifting. (Conventional technology) In an automatic transmission, various friction elements (clutch, brake, etc.) of the transmission gear mechanism are selectively hydraulically operated by line pressure to select a predetermined shift stage, and the friction element to be operated is changed to move to another shift stage. Shift gears. Therefore, if the line pressure is too high, the transient fastening capacity of the friction element becomes excessive and a large shift shock occurs, and if the line pressure is too low, the transient fastening capacity of the friction element becomes too small and the friction element slips. As a result, the service life is shortened. Therefore, it is necessary to control the line pressure properly. Conventionally, as described in "Automatic Transmission RE4RO1A Type Maintenance Manual" (A261C07) issued by Nissan Motor Co., Ltd. in March 1987, shifting and non-shifting are performed. The line pressure is controlled by determining the drive tuty of the line pressure control solenoid based on the engine throttle opening from the table data shown in Fig. 6 (A is for non-shifting and B is for shifting). It was. (Problems to be solved by the invention) However, in such a conventional line pressure control device, when the line pressure control solenoid has a variation in the product, the characteristics change with time, or the friction element has a variation in the product, or the friction material has a lapse of time. When changes occur, these cannot be dealt with. In the former case, the line pressure deviates from the appropriate value even with the same solenoid drive duty, and in the latter case, even if the line pressure is controlled in a wrong manner, it is not an appropriate value for the friction element. However, in any case, due to insufficient application of line pressure, a large shift shock and a shortened life of friction elements are unavoidable. In the present invention, as shown in FIG. 8, the automatic converter of the above document instantly t₁In the case of upshifting from the 1st speed to the 2nd speed by turning the shift solenoid from ON to OFF, when the line pressure is low, the 2nd speed selective pressure using this as the original pressure rises as shown by the solid line. The corresponding friction element is fastened and advanced, and the input / output rotation ratio of the transmission gear mechanism is N._T/ N_O(N_T: Input speed, N_O: Output rotation speed) changes from the 1st speed equivalent value to the 2nd speed equivalent value as shown by the solid line, and the transmission output torque changes as shown by the solid line, whereas the line pressure is high. The operation waveform is as shown by the dotted line, and the gear ratio is N._T/ N_OFrom the viewpoint that it is possible to determine whether or not the lie pressure is an appropriate value in consideration of the above-mentioned variation and change with time from the time when is changing, that is, the inertia phase time T. Basically, the present invention proposes a line pressure control device that adjusts the line pressure by adjusting the line pressure by the amount of the line pressure correction amount for directing the inertia phase time during the shift to the target value during the shift. By the way, in the line pressure control method based on the learning control, if the above learning control is continued even while the hydraulic oil temperature of the automatic transmission is low and the control system including the line pressure control solenoid is unstable, the lie pressure control is randomized during this period. Therefore, learning control is rather absent. A technique for determining whether or not to perform line pressure learning control according to the hydraulic oil temperature of an automatic transmission has been conventionally proposed in Japanese Patent Application Laid-Open No. 62-137459. However, this conventional technique is not limited to the fact that the line pressure learning control is not performed at a low temperature, and the above-mentioned problem that the line pressure learning control becomes random cannot be solved. (Means to solve the problem) The present invention proposes a line pressure learning control device that does not cause this problem, and as shown in Fig. 1, the concept is shown. In an automatic transmission in which various friction elements of the transmission gear mechanism are selectively hydraulically operated by line pressure to select a predetermined transmission stage, and the friction element to be operated is changed to shift to another transmission stage. An input rotation speed detecting means that detects information according to the input rotation speed of the transmission gear mechanism, and An output rotation speed detecting means that detects information according to the output rotation speed of the transmission gear mechanism, and Inertia phase time measuring means for measuring the time during which the speed change gear mechanism is shifting based on signals from these means, and A line pressure correction amount calculation means for obtaining a line pressure correction amount for directing the inertia phase time during shifting to a target value, and A line pressure adjusting means for determining the line pressure by adjusting the line pressure correction amount during shifting this time, An oil temperature sensor that detects the hydraulic oil temperature of an automatic transmission, and It is characterized by a configuration provided with a learning control prohibition means for prohibiting a change in the line pressure correction amount by stopping the operation of the line pressure correction amount calculation means in a low temperature where the hydraulic oil temperature is less than a set value. (For use) The speed change gear mechanism selectively hydraulically operates various friction elements by the line pressure to select a predetermined speed change stage, and the supply power is accelerated / decelerated and output at this speed change stage. Then, the speed change gear mechanism is changed to another speed change stage by changing the friction element that is hydraulically operated. During this period, the input rotation speed detecting means and the output rotation speed detecting means detect information corresponding to the input rotation speed and the output rotation speed of the transmission gear, respectively. The inertia phase time measuring means measures the time during which the transmission gear mechanism is shifting, that is, the inertia phase time during the shifting, based on the signals from both of these means. The lie pressure correction amount calculation means obtains the line pressure correction amount that makes the inertia phase time during the previous shift toward the target value, and the line pressure adjustment means adjusts the line pressure by the above correction amount during the current shift to adjust the line pressure. Learn and control. Therefore, it is possible to constantly control the line pressure during shifting, which is prompted by the actual situation of the automatic transmission. In other words, even if the line pressure control element has a product variation or the characteristics change with time, or the friction element has a product variation or the friction material changes with time, these automatic transmissions The line pressure is controlled during shifting in consideration of the individual difference with time, and it is possible to avoid a situation in which a large shift shock is caused due to excess or deficiency of the line pressure or the life of the friction element is shortened. By the way, in a low temperature where the hydraulic oil temperature of the automatic transmission detected by the oil temperature sensor is less than the set value, the learning control prohibiting means stops the operation of the line pressure correction calculation means and prohibits the change of the line pressure correction amount. To do. Therefore, in the low temperature, the line pressure control system is unstable and the line pressure control by the learning control is made random, and this random control can be prevented by prohibiting the learning control. (Example) Hereinafter, examples of the present invention will be described in detail with reference to the drawings. FIG. 2 shows a power train control system of an automobile having a built-in line pressure control device of the present invention, in which 1 is an electronically controlled fuel injection engine, 2 is an automatic transmission, 3 is a differential gear, and 4 is a drive wheel. The engine 1 is equipped with a computer 5 for engine control, and this computer has an engine speed of N._ESignal from engine rotation sensor 6 to detect, signal from vehicle speed sensor 7 to detect vehicle speed V, signal from throttle sensor 8 to detect engine throttle opening TH, and intake air amount to detect engine intake air amount Q Input the signal etc. from the sensor 9. The computer 5 has a fuel injection pulse width T based on these input information._PIs determined and commanded to the engine 1, or an ignition timing control signal (not shown) is supplied to the engine 1. Engine 1 has a fuel injection pulse width T_PThe fuel is supplied in an amount corresponding to the engine, and the fuel is burned in time with the rotation of the engine for operation. The automatic transmission 2 includes a torque converter 10 and a speed change gear mechanism 11 in tandem, and inputs engine power to the input shaft 12 via the torque converter 10. The transmission input rotation to the shaft 12 is accelerated or decelerated according to the selected shift stage of the transmission gear mechanism 11 to reach the output shaft 13, and reaches the drive wheel 4 from this output shaft via the differential gear 3 to drive the vehicle. it can. The speed change gear mechanism 11 incorporates various friction elements (not shown) such as a brake in the clutch that determines the transmission path (shift stage) from the force shaft 12 to the output shaft 13, and these various friction elements are combined with the line pressure P._LThe engine is selectively hydraulically operated to select a predetermined gear, and the friction element to be actuated is changed to shift to another gear. A shift control computer 14 and a control valve 15 are provided for this shift control. The computer 14 selectively turns on the shift control shift solenoids 15a and 15b in the control valve 15, and selectively lines various friction elements so that the corresponding shift stage is selected by the combination of ON and OFF of these shift solenoids. Pressure P_LTo control the shift control. The shift control computer 14 also controls the line pressure control duty solenoid 16 in the control valve 15 by the drive duty D to control the line pressure P in the control valve 15._L(The line pressure rises as the duty D increases) shall be controlled as intended by the present invention. For the above shift control and line pressure control, a signal from the vehicle speed sensor 7 and a signal from the throttle sensor 8 are input to the computer 14, respectively, and the rotation speed N of the shaft 12 is N._TThe signal from the input rotation sensor 17 and the rotation speed N of the shaft 13_OThe signal from the output rotation sensor 18 for detecting the above and the signal from the oil temperature sensor 19 for detecting the hydraulic oil temperature TEM of the automatic transmission are input. The computer 14 executes the control programs shown in FIGS. 3 to 5 to perform line pressure control and shift control. First, to explain the line pressure control of FIG. 3 that is repeatedly executed by the scheduled interrupt, in step 20, it is checked whether or not the gear is shifting depending on whether or not the flag FLAG1 described later is 1. If non-shifting is in progress, in step 21, the line pressure control solenoid drive duty D corresponding to the throttle opening TH is table-looked up from the non-shifting table data shown by the solid line A in Fig. 6, and then this drive duty is performed in step 22. Output D to solenoid 16 and line pressure P_LIs controlled to the normal value for non-shifting. On the other hand, during shifting, in step 23, the line pressure control solenoid drive duty D corresponding to the throttle opening TH is table-looked up from the table data for transformation shown by the dotted line B in FIG. Next, in step 24, the line pressure control solenoid drive duty correction amount ΔD corresponding to the throttle opening TH is obtained from the line pressure control solenoid drive duty correction amount data stored as RAM data by the learning control described later, for example, as shown in FIG. Is read. After that, in step 25, D + ΔD is output to the solenoid 16 and the line pressure P_LIs controlled to the value for shifting. Next, in order to explain the shift control and the line pressure solenoid drive duty correction amount control in Fig. 4, which are repeatedly executed by the scheduled interrupt, first, in step 30, it is checked whether FLAG1 is 1 or not, that is, whether the shift is in progress. .. If the vehicle is not shifting, the required shift stage corresponding to the combination of the vehicle speed V and the throttle opening TH is determined based on the normal shift pattern predetermined in step 31. In the next step 32, it is checked whether or not the required shift gear should be changed depending on whether or not the required shift gear is different from the current selected shift gear. If shifting should be performed, FLAG1 = 1 is set as shown in step 33, and the solenoids 15a and 15b are switched ON and OFF to execute shifting to the required shift stage. As a result, steps 31 to 33 are skipped when shifting is in progress. In step 34, the hydraulic oil temperature TEM of the automatic transmission is read, and in the next step 35, it is checked whether or not the inertia phase is in progress. In this check, the input / output rotation speed ratio N of the transmission gear mechanism 11_T/ N_OIt is determined that the inertia phase is in progress while the gear ratio represented by is changing from the gear ratio corresponding to the shift stage before the shift to the gear ratio corresponding to the shift stage after the shift. Then, the timer TM is incremented (stepped) in step 36 during the inertia phase, and the inertia phase time is measured by the timer TM by skipping step 36 after the inertia phase. In the next step 37, it is checked whether the inertia phase is completed (shift end), and if it is not completed, the program is finished as it is, and if it is finished, the flag FLAG1 is set to 0 in step 38 corresponding to the shift end. At the same time as resetting to, set the flag FLAG2 to 1 to execute the learning control that corrects the RAM data in Fig. 7. While the shift is completed in this way and the shift is not performed thereafter, the control proceeds to step 39 through steps 30 to 32, but since FLAG2 = 1 is set as described above, step 40 is selected and the following learning control is performed. After correcting and updating the previous data of the line pressure solenoid drive duty correction amount ΔD shown in FIG. 7, FLAG2 and timer TM are cleared by executing step 41. This step 40 is as shown in FIG. 5. First, in step 50, it is checked whether or not the oil temperature TEM is low, for example, less than 20 ° C. If the temperature is not low, the timer TM measurement time, that is, the inertia phase time is checked in step 52. This inertia phase time TM is the target value (different depending on the type of shift and throttle opening) corresponding to the preferable line pressure for preventing shift shock and preventing the life of friction elements from shortening._SWhen is the same, the RAM data of the correction amount ΔD in Fig. 7 is not changed and is used as it is for the line pressure control during the next shift. But TM> T_SAt times, the line pressure is too low and the life is shortened due to the slip of the friction element. Therefore, by executing step 53, the RAM data of the correction amount ΔD in Fig. 7 is increased by 0.1% to control the line pressure during the next shift. Use. Therefore, the line pressure solenoid drive duty D + ΔD during line pressure control can be increased by 0.1% from the previous time to increase the line pressure by that amount, and the line pressure can be brought closer to an appropriate value to avoid shortening the life of the friction element. be able to. Conversely, TM> T_SAt this time, the line pressure is too high and a large shift shock occurs due to the excessive fastening capacity of the friction element. Therefore, by executing step 54, the RAM data of the correction amount ΔD in Fig. 7 is reduced by 0.1%, and the line during the next shift is being performed. Used for pressure control. Therefore, the line pressure solenoid drive duty D + ΔD during line pressure control can be reduced by 0.1% from the previous time to reduce the line pressure by that amount, and the line pressure can be brought closer to an appropriate value to prevent a large shift shock. it can. By repeating such actions (learning control), the line pressure solenoid drive duty correction amount ΔD is the line pressure solenoid drive duty D + ΔD during shifting, and the line pressure is an appropriate value (regardless of individual differences in the automatic transmission or changes over time. Initial phase time TM is the target value T_S), And the line pressure during gear shifting can be controlled to an appropriate value that does not shorten the life of the friction element or cause a large shift shock under any change in circumstances. By the way, in step 50 in Fig. 5, when it is determined that the temperature is low at TEM <20 ° C, the control is terminated as it is, and the RAM data of the correction amount ΔD in Fig. Used for pressure control, learning control is prohibited. For this reason, the system including the duty solenoid 16 for line pressure control is unstable during the low temperature, and the line pressure control by the learning control is made random. This random control can be prevented by prohibiting the learning control. it can. (Effect of the invention) Thus, as described above, the device of the present invention has an inertia phase time TM as a target T._SSince the line pressure during shifting is learned and controlled so that the line pressure during shifting can be maintained at an appropriate value without excess or deficiency even if there are individual differences in the automatic transmission or changes over time, it is large. It is possible to prevent a shift shock and a decrease in the life of the friction element. Further, since this learning control is prohibited during low oil temperature at which the line pressure control system becomes unstable, it is possible to prevent the line pressure control during shifting at low oil temperature from becoming random.

[Simple explanation of drawings]

FIG. 1 is a conceptual diagram of the line pressure control device of the present invention. FIG. 2 is a control system diagram of an automobile power train showing an embodiment of the apparatus of the present invention. 3 to 5 are flowcharts showing the line pressure control and shift control program of the shift control computer in the same example. Fig. 6 is a characteristic diagram of the line pressure control solenoid drive duty. FIG. 7 is a diagram illustrating a momentary RAM data regarding the correction amount of the same duty. FIG. 8 is a shift operation time chart showing the occurrence status of the inertia phase during shift. 1 ...... Electronically controlled fuel injection engine 2 ...... Automatic transmission 3 ...... Differential gear 4 ...... Drive wheels 5 ...... Computer for engine control 6 ...... Engine rotation sensor 7 ...... Vehicle speed sensor, 8 ...... Throttle sensor 9 ...... Intake air amount sensor 10 ...... Torque converter 11 ...... Transmission gear mechanism 14 ...... Shift control computer 15 ...... Control valve 15a, 15b ...... Shift solenoid for shift control 16 ...... Duty solenoid for line pressure control 17 ...... Input rotation sensor 18 ...... Output rotation sensor 19 ...... Oil temperature sensor