JPH01150050A - Hydraulic control device for automatic transmission - Google Patents

Abstract

PURPOSE:To perform the most accurate back pressure control in the present of an accumulator by performing a study correction of the method of electronic control for a value of parameters in a speed change thereafter in accordance with the detected speed change time. CONSTITUTION:An electronic control means electronically controls a back pressure of an accumulator in accordance with a value of parameters, for instance, engine torque or the like able to estimate a degree of a speed change shock, controlling the engaging transient oil pressure of a friction engaging unit. After the control in the above, a computer detects the speed change time by detecting a change of turbine speed specifying the speed change in its start and end, and in accordance with this speed change time, a study correction of the method of electronic control is performed for the value of the parameter in the speed change thereafter. Accordingly, even when the parameter is the same value, the method is successively studied in a manner wherein the electronic control is performed considering the actual speed change time. Thus performing the most accurate back pressure control in the present of the accumulator by a study control, the speed change shock can be prevented from its generation.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a hydraulic control device for an automatic transmission, and more particularly to an improvement in a hydraulic control device for an automatic transmission that can alleviate shock during gear shifting.

[Conventional technology]

The hydraulic control device for an automatic transmission is provided with an accumulator having a cylinder-piston structure that can adjust the transient hydraulic pressure of the frictional engagement device between a shift valve for changing gears and a frictional engagement device. ing. This accumulator maintains the oil pressure supplied to the frictional engagement device at a set oil pressure for a predetermined period of time to reduce shock during gear shifting. The optimal value of this set oil pressure changes depending on the engine torque input to the automatic transmission. Also, this setting oil pressure is
It can be controlled by changing the oil pressure applied to the back pressure chamber of the accumulator. In view of these points, JP-A-61-130653 is equipped with a solenoid valve for controlling the back pressure of the accumulator, and the ON-OFF duty ratio of this solenoid valve is determined for each throttle opening. However, methods have been proposed to precisely control accumulator backpressure.

[Problems to be solved by the invention]

However, with this technology, the duty-next pressure guided to the accumulator back pressure control valve in response to the throttle opening was uniquely determined, so once the throttle opening was determined, the accumulator back pressure was completely set to a specific value. fixed,
Therefore, there was a problem that the oil pressure set by the accumulator was also fixed at a specific value (Fig. 8 (A) -
(See (D)). In other words, in reality, even if the throttle opening is the same, engine torque varies greatly depending on factors such as engine speed, intake temperature, and intake pressure (or boost pressure), so the determined accumulator back pressure may not necessarily be appropriate. There was a problem. Regarding this problem, for example, Japanese Patent Application Laid-Open No. 61-149657
The countermeasures are disclosed in the publication. In other words, this measure means that when controlling the back pressure of the accumulator, it is not only the throttle opening that is controlled, but also various factors such as automatic transmission oil temperature, engine intake air temperature, engine rotation speed, supercharging pressure, etc. This allows for more detailed control. However, as mentioned above, no matter how many parameters indicating the steady state of the vehicle and the state of the driving environment are taken in,
In hydraulic control, there are and will always be variations and changes over time that cannot be predicted at the design stage. For example, even if the throttle opening, engine speed, intake temperature, intake pressure, etc. are the same, the engine torque changes due to changes in the engine itself over time, and changes the shift characteristics. Also, variations in the dimensions and ease of movement of each valve and accumulator in an automatic transmission naturally affect the hydraulic characteristics, but even if these variations are tuned at the time of manufacture! ! It changes over time. Furthermore, if the oil in the automatic transmission deteriorates or is contaminated with impurities that affect the flow of oil, the shifting characteristics will also change. Furthermore, Fig. 9 shows the traveling distance and the dynamic friction coefficient μ of the frictional engagement device.
As the frictional engagement device wears out and the dynamic friction coefficient μd becomes smaller, as shown in the figure, the speed change characteristic becomes significantly different from the initial state. Therefore, since there are such uncertain factors, it is not always possible to obtain the same speed change characteristics if the accumulator back pressure is uniquely determined by various parameters such as the throttle opening degree. This point will be specifically explained based on FIG. Figure 10 shows the output shaft torque waveform during a typical power-on upshift (upshift with the accelerator depressed), where the solid line is normal and the broken line is when the engine torque decreases. The dashed lines each indicate when the dynamic friction coefficient μd decreases. When the accumulator back pressure is determined and controlled only by the throttle opening, when the throttle opening is the same, the set pressure by the accumulator does not change even if the engine torque decreases, so the shifting speed becomes faster, and the shifting time becomes faster as shown by the dotted line. becomes shorter. Also, if the engine torque itself is taken into account when controlling the back pressure of the accumulator, it becomes possible to control the back pressure of the accumulator according to changes in engine torque, but even if the back pressure of the accumulator is the same, the coefficient of kinetic friction When μd decreases, the transmission torque capacity of the engaged friction material decreases, the shift time increases, and in the case of the ViA end, the accumulator's operating head [(buffer area) end] Even if this point is reached, the shift may not be completed yet, and an extremely large shift shock may occur. This is because the transmitted torque capacity increases rapidly at the end of the accumulator's operating range. However, as described above, it is extremely difficult to deal with changes in the dynamic friction coefficient μd at the design stage.

[Purpose of the invention]

The present invention has been made in view of such conventional problems, and it is possible to accurately follow the uncertain variations inherent in vehicles that occur during manufacturing or over time when controlling back pressure of an accumulator. It is an object of the present invention to provide a hydraulic control device for an automatic transmission that can always obtain the best shifting characteristics.

[Means to solve the problem]

As summarized in FIG. 1, the present invention electronically controls the back pressure of an accumulator according to the value of a parameter that can estimate the magnitude of a shift shock, thereby reducing the engagement transient hydraulic pressure of a friction engagement device. A hydraulic control device for an automatic transmission, comprising means for detecting a shift time, and means for learning and correcting how to electronically control the value of the parameter in a subsequent shift according to the shift time. By preparing for this, the above objectives were achieved.

[Operation and effects of the invention]

In the present invention, the back pressure of the accumulator is basically determined according to a parameter that can estimate the magnitude of the shift shock, such as the value of engine torque. Moreover,
A shift time is detected, and the character spacing is corrected in accordance with the detected shift time in an electronic control method for the value of the parameter in a subsequent shift. As a result, even if the parameter values are the same, the electronic control will be sequentially learned to take into account the actual shift time, and changes over time that cannot be grasped with the parameters that are constantly being captured. be able to respond appropriately. Note that the back pressure of the accumulator may be of the type that controls the duty ratio of a so-called solenoid valve, or
A type that uses an electromagnetic proportional valve that can change the output oil pressure depending on the load current may be used. Since the present invention does not perform feedback correction of the accumulator back pressure in real time, the calculation speed does not need to be very fast, and the present invention uses learning to control the accumulator back pressure most appropriate to the current situation, that is, the friction engagement device. Engagement transient hydraulic control can be performed.

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. FIG. 2 shows an overall outline of a vehicle automatic transmission to which this embodiment is applied. This automatic transmission includes a torque converter section 20 and an overdrive mechanism section 40 as its transmission sections.
and an underdrive mechanism section 60 with three forward stages and one reverse stage. The torque converter section 20 is of a well-known type and includes a pump 21, a turbine 22, a stator 23, and a lock-up clutch 24. The overdrive mechanism section 40 includes a set of planetary gears including a sun gear 43, a ring gear 44, a planetary pinion 42, and a carrier 41, and the rotational state of the planetary gears is controlled by a clutch Co1, a brake Bo, and a one-way clutch Fo. controlled by. The underdrive mechanism section 60 includes a common sun gear 6
1, ring gear 62.63, planetary binion 64.
65 and carriers 66 and 67, and the rotational state of these two sets of TI planetary gear devices and the connection state with the overdrive mechanism are controlled by the clutch C1.
, C2, brakes 81 to B3, and one-way clutch F
1. Controlled by F2. Since this transmission unit itself is well known, the specific connection state of each component will only be shown in a skeleton diagram in FIG. 2, and detailed explanation will be omitted. This automatic transmission includes a transmission section as described above,
and a computer 84. The computer 84 includes a throttle sensor 801 that detects the throttle opening θ to reflect the output (torque) of the engine 1, and a vehicle speed N.
o (rotational speed sensor of the output shaft 70 for automatic gear shifting) 82, and the drum of the clutch Co, which is selected as a member whose rotational speed changes when gear shifting is performed, in order to detect gear shifting time. rotational speed N C
Each signal from the sensor 99 and the like is input. The rotational speed of the clutch Co is equal to the turbine rotational speed between the first speed stage and the third speed stage, and is zero during the fourth speed stage. The Go rotational speed changes significantly as the speed change is performed. Therefore, C. By detecting the rotational speed NGO, the start and end of a shift can be detected, and as a result, the shift time can be detected. The computer 84 receives these signals and controls the solenoid valves S1 and S2 (for shift valves) in the hydraulic control circuit 86 according to a preset throttle opening-vehicle speed shift map.
, and SL (for lock-up clutch), and execute the combination of engagement of each clutch, brake, etc. as shown in Fig. 3, thereby performing basic shift control for each gear. This is done using a known method. Also, a duty solenoid 104.10 is used to control accumulator back pressure.
6 is driven and controlled. FIG. 4 shows the main parts of the hydraulic control circuit 86. In the figure, numeral 102 is a duty modulator valve, 104.106 is a duty solenoid, and 108.1
10 is a damper, 112 and 114 are accumulator control valves, and 116 and 118 are accumulators for controlling the engagement wave transmission oil pressure to the clutch C2 and brake B2, respectively. The duty modulator valve 102 has a well-known configuration and reduces the line pressure PL to a constant pressure PL1. This constant pressure PL1 is the duty solenoid 10
The supply pressure will be 4.106. The duty solenoids 104 and 106 reduce the constant pressure PL+ by rapidly turning on and off at intervals according to the duty ratio commanded by the computer 84, and generate duty control pressures PS1 and PS2. Therefore, duty control pressures P81 and PS2 are maintained at predetermined values determined by the respective duty ratios regardless of changes in line pressure PL. The dampers 108 and 110 are connected to the duty solenoid 104.
．． Duty control pressure Ps accompanying high-speed on-off of 106
i, Absorb PS2 pulsation. The duty control pressures PSI and PS2 are led to accumulator control valves 112 and 114, respectively, and the line pressure PL is adjusted to the duty control pressure PSI in a well-known manner.
, PS2 is regulated and controlled according to the value of accumulator 116.11 as accumulator back pressure PA+, PAz.
8 back pressure chambers 116A and 118A. As is clear from FIG. 3, for example, when shifting from the first gear to the second gear, the brake B2 is engaged, and the accumulator back pressure PA2 at this time learns the duty ratio of the duty solenoid 106. Optimization is achieved through correction and control. The learning control for shifting from the first gear to the second gear will be described in detail below. FIG. 5 shows an example of the basic duty ratio with respect to the throttle opening. That is, in response to the throttle opening signal input from the throttle opening sensor 80, the computer 84 starts controlling the duty solenoid 106 using the basic duty ratio as shown in FIG. Note that this horizontal axis may be any parameter that represents engine torque, such as intake pipe negative pressure or intake air M. Naturally, it is also possible to use the engine torque itself. FIG. 6(A) is an example of a change in the rotational speed of the clutch Co when shifting from the first gear to the second gear. In order to understand this gear shift time,
It is determined that the shift starts at the time ^, and the end of the shift is determined at the time . In this case, the time required for the actual gear shift, that is, the actual gear shift time 1R, is calculated as (day - t^). Based on this actual shift time TR, the duty solenoid 106
Correct the duty ratio. DSSD 1 = DSSD 1 + (1-tR/
jK)xDssDIB ・・・・・・ (1)
Here, DSSDl is the duty ratio of the duty solenoid 106, tK is the basic (ideal) shift time predetermined for shifting from the first gear to the second gear, and DSS
DIB is a correction coefficient. This correction coefficient 08SD I B is designed to change depending on the throttle opening. DSSD1 uses the basic duty ratio shown in FIG. 5 in the initial state (in which the backup RAM of the computer 84 is also cleared). The corrected duty ratio DSSD1 is stored in the backup RAM in the computer 84 to be used as the duty ratio at the next time of shifting from 1 to 2 with the same throttle opening. When changing the opening degree from 1 to 2, the corrected value becomes the initial value. The duty ratio DSSD1 is also corrected during the 1st to 2nd shift, and becomes the updated value each time. Similar corrections are made for other speed changes, such as those in which clutch C2 is engaged. This causes variations in engine torque, changes over time, and hydraulic pressure side t.
Regardless of variations in each valve of the ill device, changes over time, variations in the characteristics of the dynamic friction coefficient μd of the friction engagement device, changes over time, etc., when the same type of speed change and the same throttle opening, It becomes possible to always obtain the same shifting characteristics. FIG. 7 shows a flowchart of the above control. In this flowchart, a shift from the first gear to the second gear is taken as an example. In FIG. 7(A), when there is a decision to shift from the first gear to the second gear, the solenoid S1 for performing the gear shift is driven (step 151), and the shift from the 1st to the 2nd gear is activated. The flag Fo is set to 1 (step 152). FIG. 7(B) shows a duty ratio correction routine that is different from the main routine regarding shift determination. In step 201, it is determined whether Fo=1. If Fo=O (speed change from 1 to 2 is not in progress), this routine exits. If Fo=1, the process advances to step 202. In steps 202 to 208, it is determined whether the actual speed change has already started, that is, whether the change in the rotational speed of the clutch Co has started or not, and whether the above-mentioned [^ has been reached] is determined. This determination is made, for example, 01 times in a row if the actual Go rotational speed (=turbine rotational speed) Neo is smaller than a value (NcolN^) that is smaller than the Co rotational speed Nco1 at the first gear by a predetermined rotational speed N^. It depends on whether it is judged or not. Since the 1st to 2nd gear shift point (vehicle speed) is determined for each throttle opening, the Co rotational speed Nco1 at the time of 1st gear is determined between that gear point (vehicle speed) and the 1st gear shift point (vehicle speed). It is determined from the gear ratio of The predetermined rotational speed N^ mainly takes into consideration the correspondence error between the throttle opening and the 1→2 shift point (vehicle speed). The reason for confirming that 01 times are repeated is mainly to prevent detection errors. Specifically, in step 202, Nco<Ncol−N^
It is determined whether or not the following holds true. When this condition is satisfied, the process proceeds to step 203, and a flag F1 indicating whether the condition is satisfied for the first time is determined. Since this flag F1 is initially set to zero, the process advances to step 204. At 204, flag F1 is set to 1. Thereafter, in step 205, the number of detections n^ is set to 1. After being reset and returning to step 202, N c
When it is determined that the condition o < N co 1- N^ is satisfied again, it is determined in step 203 that F1=1, so the process proceeds to step 206, and the number of detections n^ is n
, or more is determined. Since this nl is generally set to about 2 to 4 times, a "NO" determination is initially made, and the number of detections n^ is incremented in step 207. In this way N c
o < N co 1- Each time N^ is detected consecutively, the number of detections n^ is incremented. If the condition is not satisfied even at − degrees, it is set to Fl-0 in step 202A, so the number of detections n^ is set to 1 again when the condition is satisfied next time. When the number of detections n^ reaches 01, it is determined that the shift has started and that the hitting time t^ has arrived, and the process proceeds to step 208. In step 208, the determination flag F2 is checked to determine whether or not the determination in step 206 is rYEsJ for the first time. This flag F2 is initially set to F1=0. Therefore, the process first proceeds to step 209, sets F2=1, and confirms and stores the time t^ in FIG. 6 (step 210
). Specifically, a counter Tl1l is started. This counter Tm is incremented by a regular interrupt from the computer 84. In steps 212 to 217, it is determined whether or not the shift has been completed, that is, whether or not the time t8 has been reached. The basic procedure is the same as steps 202 to 207 described above. However, the determination of the end of the shift is based on the Go rotation speed N C
fil (N co 2 + N
This is performed depending on whether it is determined that a is smaller than 02 times in a row. Once the throttle distance is determined, the Co rotational speed N co 2 in the second gear is determined from the 1→2 gear shift point (vehicle speed) and the gear ratio of the second gear. The predetermined rotational speed N days mainly takes into consideration the correspondence error between the throttle opening and the 1→2 shift point (vehicle speed). The reason for confirming that the detection has occurred twice in a row is mainly to prevent detection errors. Flag F3 of step 213 has the same meaning as 7-lag F1 of step 203, and step 212A has the same meaning as step 202A. Further, "0 day increment" in step 217 has the same meaning as "n^ increment" in step 207. In this way, when it is determined that the condition of N co < N co 2 +N days is satisfied 02 times in a row, step 2
Proceeding to step 18, time te is determined and stored. Specifically, the increment of the counter Tl set in step 210 is stopped at this stage. In step 219, the shift time [R] is determined. Specifically, this is done by checking the count number of the counter Tm incremented between the day and the time t^. After the shift time tR is determined, the process proceeds to step 220, and the duty ratio [)SSDI is calculated based on the above-mentioned equation (1).
Correct. After that, in step 221, the flag F
Clear o=F3. According to the above flow, when it is determined to shift from 1 to 2, the shift start timing t^ is determined in step 210, and
In step 218, the WJt date at the end of the shift is determined. After that, the duty ratio DSSDI is determined based on the shift time tR.
will be corrected. In this way, the duty ratio DSSDI is corrected every time a 1st → 2nd shift occurs,
As a result, the speed change characteristics can be brought closer to ideal conditions. For shifting from 2nd gear to 3rd gear, clutch C2
Learning control of the duty ratio is performed using a similar procedure. Note that in this embodiment, neither duty control nor learning control is performed for the shift from the third gear to the fourth gear. This is because the shift shock from the third gear to the fourth gear is originally small. However, in the present invention, learning control may also be performed for the third to fourth gears.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the gist of the present invention, and FIG. 2 is a block diagram showing the gist of the present invention.
A schematic block diagram of a vehicle automatic transmission to which an embodiment of the present invention is applied, FIG. 3 is a diagram showing the operating state of the frictional engagement device in the automatic transmission, and FIG. 4 is a diagram showing the operating state of the frictional engagement device in the automatic transmission. Fig. 5 is a hydraulic circuit diagram showing the main parts of the hydraulic control system of
A pictorial diagram showing the relationship between throttle opening and basic duty ratio, Figure 6 is a diagram showing changes in the rotational speed of clutch Co, and Figure 7 (A>, (B) is a diagram showing the learning correction of duty ratio. Flowchart showing the control flow for performing
) to (D) are diagrams showing the relationship between each parameter in a conventional back pressure control device for an accumulator, and FIG. 9 is a diagram showing the relationship between the travel distance and the coefficient of dynamic friction of the friction material of the friction engagement device. The diagram in FIG. 10 is a diagram for explaining how the output shaft torque of the automatic transmission changes during normal operation, when the engine torque decreases, and when the dynamic friction coefficient of the friction material decreases. 104.106...Duty solenoid, 112.
114...Accumulator control valve, 116.118...Accumulator, N co...
Rotational speed of clutch Co, [R...shift time, DSSDl...duty ratio, DSSDIB...correction coefficient.

Claims (3)

[Claims] (1) Hydraulic control of an automatic transmission that controls the transient hydraulic pressure for engagement of the frictional engagement device by electronically controlling the back pressure of the accumulator according to the value of a parameter that can estimate the magnitude of the shift shock. An automatic transmission characterized in that the device comprises: means for detecting a shift time; and means for learning and correcting the electronic control method for the value of the parameter in a subsequent shift according to the shift time. Hydraulic control device. (2) The hydraulic control device for an automatic transmission according to claim 1, wherein the learning of the shift time is performed by detecting fluctuations in the turbine rotation speed and specifying the start and end of the shift. (3) The learning of the shift time is performed by detecting fluctuations in the rotation speed of a member whose rotation speed changes due to the shift and identifying the start and end of the shift. Hydraulic control device for the automatic transmission described.