JP2008106943A - Automatic transmission and standby hydraulic pressure value setting method for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for setting a highly accurate and robust standby hydraulic pressure value. <P>SOLUTION: An electronic control part of an automatic transmission makes stepped hydraulic pressure waveform control wherein a step pressure ΔP is very small while a step interval Δt is sufficiently long. Changes in flow rate are negligible and piston speed is slow and constant so that pressure equivalent to the pressure of a return spring is available. In a learning mode, the electronic control part of the automatic transmission makes the driving control of hydraulic pressure, monitors a difference value Nte between turbine speed Nt and engine speed Ne in a measuring cycle sufficiently shorter than the time interval Δt, detects whether the stroke of a piston has been out of the area of flow rate control (piston end), and sets an engagement hydraulic pressure Pc at that time as a standby hydraulic pressure value related to a frictional engagement element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic transmission and a standby hydraulic pressure value setting method for an automatic transmission.

  In the hydraulic control of an automatic transmission, the hydraulic pressure from a hydraulic pressure source is directly controlled by a solenoid valve to control the hydraulic pressure supplied to the friction engagement elements (friction clutch, friction brake). A method of performing non-engagement is known. For example, in Japanese Patent Laid-Open No. 2002-295529, electronic control is performed in this system in order to perform control that “the play area until the clutch starts to be engaged is suddenly engaged, and when the clutch starts to be engaged, the connection speed is switched and connected slowly”. A clutch torque point learning method is introduced in which the control unit learns the duty ratio of a duty pulse as a torque transmission start point (torque point) and performs optimal solenoid valve release control.

  As shown in FIG. 8, in the play area of the first half of the piston stroke of a clutch piston (hereinafter simply referred to as a piston), so-called precharge is performed to rapidly fill the friction engagement element with fluid, thereby increasing the piston operation. To be done. After a predetermined precharge time has elapsed, the piston speed is reduced to near zero immediately before the engagement of the friction engagement element, and the hydraulic pressure (standby hydraulic pressure) corresponding to the return spring of the reaction element is reduced. It is necessary to hold and make the piston stand by to improve responsiveness and followability. Thus, both shortening of the shift operation and prevention of shift shock can be achieved.

  However, there is a variation in the spring force of the return spring itself, and unlike general pressure control, the piston strokes, so it becomes an area for flow control, and various specifications other than the control valve performance, for example, the amount of oil pump realized. There is a situation that the command pressure does not match the actual pressure. For these reasons, it is desired to propose a method for accurately detecting and setting the return spring equivalent pressure (standby hydraulic pressure). In particular, if the return spring equivalent pressure (standby hydraulic pressure) for appropriate standby control of the piston can be set at the initial shipment of the vehicle, individual differences in the vehicle due to variations in automatic transmissions, engines, solenoid valves, etc. can be absorbed. It is possible to provide stable quality.

  As a technique for setting a return spring equivalent pressure (standby hydraulic pressure) in consideration of such individual differences for each vehicle, for example, in Japanese Patent Laid-Open No. 8-338519, a change in the rotational speed of an input shaft is monitored and the change is detected. On the basis of this, a fluid-operated friction element fastening control device capable of correcting the critical pressure, ie, the standby pressure, at which the fastening force is generated is introduced. JP-A-8-303568 discloses an appropriate initial control pressure, that is, a standby pressure, based on an engagement start pressure at the time when clutch engagement is started by performing appropriate neutral control. Possible automatic transmission control devices are introduced.

  However, in the technique described in Japanese Patent Application Laid-Open No. 8-338519, the input shaft rotation speed change is inherently minute and easily detected by fluctuations in the engine rotation speed and noise. When the precharge control is inappropriate, there is a problem that the input shaft rotational speed change itself disappears. Therefore, although it can be applied to long-term learning, it is not suitable for application at the initial shipment.

Even with the technique described in Japanese Patent Application Laid-Open No. 8-338519, it is necessary to change the threshold value used for detecting the engagement start pressure for each automatic transmission because the characteristics differ for each automatic transmission. It is necessary to consider the influence of changes in temperature (oil temperature). Further, since the technique described in this publication originates from the optimal neutral control, the input torque is relatively small as in the case of the N → D C ₁ clutch, and the rotation change is equal to or less than the input shaft rotation change. Although it can be preferably applied to the detection of the standby pressure in the frictional engagement element, the required detection accuracy cannot be expected for the detection of the standby pressure in the other frictional engagement elements because the change in rotation is severe.

JP 2002-295529 A JP-A-8-338519

JP-A-8-303568

  The present invention has been made in view of the above-described circumstances, and its object is to provide a high-accuracy and robust standby that can be applied regardless of changes in various conditions such as individual differences in vehicle and temperature. An object of the present invention is to provide a hydraulic pressure value setting method and an automatic transmission having such a standby hydraulic pressure value setting function.

  According to a first aspect of the present invention that provides means for solving the above-described problems, a plurality of friction engagement elements constituting a plurality of shift stages by a combination of engagement and disengagement, and the hydraulic pressure to be supplied A control unit that controls engagement / disengagement of the friction engagement element by control, and a switching unit to a learning mode for learning a standby hydraulic pressure value after precharging; Standby hydraulic pressure value determining means which is activated by switching to the learning mode and determines a standby hydraulic pressure value based on at least an input value consisting of the turbine speed, and is switched to the learning mode when the vehicle is stopped. In this case, the standby hydraulic pressure value determining means sets the hydraulic pressure relating to the friction engagement element for setting the standby hydraulic pressure value to a predetermined level while maintaining the input shaft rotational speed of the automatic transmission. Increment every time interval, The friction engagement element is shifted to the engagement side, and the input value is measured and stored for a predetermined cycle in a predetermined determination cycle. Further, the current input value and the input value before the predetermined determination cycle are The difference value is calculated and stored, and in the current determination cycle, the change in the input value due to the decrease in the turbine speed satisfies a predetermined noise removal condition, and the difference value in the current determination cycle is When the difference value in the previous determination cycle exceeds a predetermined threshold value and the difference value in both determination cycles indicates a decreasing tendency of the turbine rotation speed, the hydraulic pressure at that time is set as the standby hydraulic pressure. An automatic transmission characterized by learning setting is provided.

  Further, according to the second aspect of the present invention, a plurality of friction engagement elements constituting a plurality of shift stages by a combination of engagement and disengagement, and engagement of the friction engagement elements by controlling the hydraulic pressure to be supplied. Standby hydraulic pressure setting after precharging of an automatic transmission having a control unit for controlling engagement / disengagement and standby hydraulic pressure value determining means for determining a standby hydraulic pressure value based on at least an input value consisting of turbine speed In the method, the control unit gradually increases the hydraulic pressure related to the friction engagement element for setting the standby hydraulic pressure value at predetermined time intervals while maintaining the input shaft rotation speed of the automatic transmission when the vehicle is stopped. The friction engagement element is shifted to the engagement side, and the standby hydraulic pressure value determining means measures the input value in a predetermined determination cycle, stores and holds the predetermined cycle, and further determines the current input value. Input value before a given judgment cycle Is calculated and stored, and in the current determination cycle, the change in the input value due to the decrease in the turbine speed satisfies the predetermined noise removal condition, and the difference value in the current determination cycle If the difference value in the previous determination cycle exceeds a predetermined threshold value and the difference value in both determination cycles shows a decreasing tendency of the turbine rotation speed, the hydraulic pressure at that time is set as the standby hydraulic pressure. A standby hydraulic pressure value setting method characterized in that learning setting is performed as follows.

  Further, when the automatic transmission includes an engine speed input means, it is preferable that the standby hydraulic pressure value determination means uses a difference value between the turbine speed and the engine speed as the input value.

  According to the present invention, it is possible to absorb individual differences between vehicles and set an accurate standby pressure. Further, the present invention has an advantage that it is not easily affected by changes in various conditions such as a vehicle, an automatic transmission, and temperature. It has been found from actual vehicle data that the present invention is very strong against hydraulic vibration.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an automatic transmission according to an embodiment of the present invention. Referring to FIG. 1, the automatic transmission 1 includes a transmission main body 2, a hydraulic control unit 3, and an electronic control unit 4.

  The transmission main body 2 includes an input shaft 11 connected to the turbine 10a of the torque converter 10, an output shaft 12 connected to the wheel side, a double pinion planetary gear G1 and a single pinion planetary gear G2 connected to the input shaft 11. , G3, friction clutches C1, C2, and C3 disposed between the input shaft 11, the double pinion planetary gear G1, and the single pinion planetary gears G2 and G3, and friction brakes B1 and B2. With the above configuration, the engagement / disengagement pair of the friction clutches C1, C2, C3 and the friction brakes B1, B2, which are friction engagement elements, is selected by the hydraulic control unit 3 and the electronic control unit 4, and FIG. Any of the shift speeds illustrated in FIG.

  FIG. 3 is a schematic diagram of a wet multi-plate clutch exemplified as the friction engagement element. Referring to FIG. 3, a piston 31, a return spring 32 serving as a reaction force element of the piston 31, a driven plate 331 fitted to the clutch drum 33 side, and a drive plate 341 fitted to the clutch hub 34 side It is equipped with. When the piston 31 is sufficiently pressed against each plate by the oil pressure by the oil pressure control unit 3, friction is generated between the driven plate 331 and the drive plate 341, and the state is shifted to the engaged state, and the turbine rotational speed Nt decreases. On the other hand, when the hydraulic pressure is reduced by the hydraulic pressure control unit 3, the return spring 32 pushes back the piston 31 and shifts to the disengaged state.

  Based on an instruction from the electronic control unit 4, the hydraulic control unit 3 switches an internal hydraulic circuit, selects a friction engagement element, controls the hydraulic pressure to be supplied, and engages / engages the friction engagement element. Control disengagement.

  The electronic control unit 4 includes a turbine rotation sensor 13 for detecting the turbine rotation speed Nt of the input shaft 11 (turbine 10a), a position sensor 14 for detecting the position of the selector lever operated by the driver, and an engine rotation speed Ne. It is a computer that drives and controls the hydraulic control unit 3 based on input values from various sensors including an engine rotation sensor 15 to be detected. In addition, the electronic control unit 4 includes a learning mode switching unit 41 configured to be shifted to an operation mode for learning a standby hydraulic pressure value, and a standby hydraulic pressure determination unit 42 configured to perform standby hydraulic value setting processing. And. When a predetermined operation that can be detected by the computer constituting the electronic control unit 4 is performed, the learning mode switching unit 41 starts a standby pressure setting process described later.

By the way, the state of the hydraulic system represented by the above-described wet multi-plate clutch is expressed by the following formula (1) (continuous fluid type) and formula (2) (piston motion equation).

  Here, Pc: engagement hydraulic pressure, K: bulk modulus, V: volume, Qs: input flow rate, Qb: leakage flow rate, Ap: piston area, k × x + Fset: return spring force, m: piston mass, C: damping It is a coefficient.

  Here, a case is assumed in which a stepped hydraulic waveform obtained by increasing the hydraulic pressure by the step pressure is used with a sufficient time interval. That is, when the step pressure is very small and the step interval is long enough, the flow rate change can be ignored, the piston speed is slow and constant, the damping force need not be considered, and the state is almost static. Conceivable.

Therefore, in such a state, the left side of Equation (2) only needs to consider the third and fourth terms, and the following Equation (3) is obtained.

  If the piston is moved to the engagement side while the static state is maintained and the end of the flow rate control region of the piston stroke can be detected, the indicated pressure at that time can be adopted as the return spring equivalent pressure Pc. .

  As a specific example, the setting of the standby hydraulic pressure value for the friction clutch C3 will be described. When the engine is started, the vehicle is stopped (the output shaft 12 is fixed), and the program for setting is started, for example, the select lever moves from the N range (the friction brake B2 is engaged) to the R range (friction). When the clutch C3 and the friction brake B2 are engaged), the electronic control unit 4 first engages the friction brake B2 via the hydraulic control unit 3. As described above, in the N range, the electronic control unit 4 maintains this state because it is neutral with the friction brake B2 engaged.

  Subsequently, the electronic control unit 4 gradually increases the hydraulic pressure of the friction clutch C3 by the step pressure ΔP (for example, 10 Kpa) every time interval Δt (for example, 0.9 sec) via the hydraulic pressure control unit 3. A drive signal is output.

  FIG. 4 is a diagram showing a stepwise hydraulic waveform formed by the above control and a change in the turbine rotational speed Nt. As shown in FIG. 4, the electronic control unit 4 performs the above-described drive control, and sets the difference value Nte between the turbine speed Nt and the engine speed Ne at a measurement cycle that is sufficiently shorter than the time interval Δt, for example, at an interval of 100 msec. Monitoring is performed to detect whether or not the piston stroke has left the flow control region (piston end) (determination in FIG. 3), and the engagement hydraulic pressure Pc at that time is set as a standby hydraulic pressure value for the friction clutch C3. To do.

Next, details of the determination process will be described with reference to FIG. First, after performing a predetermined initialization process (step S1), the electronic control unit 4 increases the engagement hydraulic pressure by a step pressure ΔP (step S2), and then receives it from the turbine rotation sensor 13 and the engine rotation sensor 15. , to hold the calculated input value Nte predetermined n cycles storage, _Nte the previous cycle, Nte 1, the contents of the · · · _{Nte n-1,} with a Nte _1, Nte 2 · · · Nte _n, The input value Nte of the current cycle is stored and held (step S3). Subsequently, the difference between the electronic control unit 4, the difference value DerutaNte of the previous cycle and DerutaNte _1, stores holding an input value Nte the current cycle, and the input value Nte _n predetermined cycle before (e.g., 500 msec before) And the difference value ΔNte is stored and held (step S4). Then, as a result of the above, it is determined whether or not the piston end is established depending on whether or not all of the following conditions (A) to (D) are established (step S5).
(A) ΔNte> threshold value Nte_th (for example, 10 rpm)
(B) ΔNte ₁ > threshold value Nte_th (for example, 10 rpm)
(C) ΔNte> ΔNte ₁
(D) Nte continuously increases or is equal to a predetermined m times or more (for example, m = 5).
_{(Nte> = Nte 1> =} Nte 2 ···> = Nte m)
The condition (D) is for preventing erroneous determination due to noise or the like. If the piston end is established, the engagement hydraulic pressure at that time is learned and set as a standby hydraulic pressure value (step S7).

  On the other hand, when the piston end is not established, as long as the time interval Δt continues, the processing from step S3 to step S5 is repeated. When the time interval Δt ends, the processing returns to step S2 and A process of increasing the combined hydraulic pressure by the step pressure ΔP is performed (step S6).

FIG. 6 is a diagram for explaining the determination condition by showing a change in decrease in the turbine rotational speed Nt in the vicinity of the determination point. In addition, although the engine speed Ne is introduced in the above determination conditions, the engine speed Ne is substantially constant, and is omitted in FIG. 6 for simplicity. As shown in FIG. 6, the solid lines (Nt, Nt ₁ , Nt ₂ ,... Nt _n ) connecting the black circles are judgment limit points, and it is possible to detect a sudden drop in the turbine speed indicating that the piston end is established. It has become. That is, if the turbine rotational speed Nt continuously decreases in the shaded areas B and C, the above conditions (A) to (D) are satisfied, and the piston stroke has left the flow rate control area (piston end). And the above conditions (A) to (D) can be satisfied even if the turbine rotational speed Nt increases in the shaded area A.

  The return spring equivalent pressure obtained in this way accurately matches the value obtained by determining the piston stroke based on the above equation (3) and dividing the return spring load measured at the single item level by the piston area. did. That is, the dispersion of individual vehicles is absorbed, and the return spring equivalent pressure corresponding to each automatic transmission is detected with high accuracy, and this value can be preferably used as the standby hydraulic pressure value after precharging.

  Further, by adjusting the step pressure ΔP by the electronic control unit 4, it is possible to reduce erroneous determination and variation. For example, when the gradient of the actual pressure is small with respect to the command pressure, it is expected that the rotational change will be small. In this case, it is possible to cope with it by slightly increasing the step pressure ΔP.

  In the present embodiment, | Nt−Ne | = Nte is used as an input value, and fluctuations in engine rotation are taken into consideration. The reason is explained here. FIG. 7 is a diagram of measurement of actual pressure and turbine rotation change when stepping up in a stepwise manner with respect to the friction engagement element in which rotation change is difficult to appear. Referring to FIG. 7, because of the stepped hydraulic waveform, the change in the turbine rotational speed is extremely gradual. Therefore, in the present embodiment, in consideration of the case of a friction engagement element in which such a change in rotation is difficult to occur, fluctuations in engine rotation are also taken into consideration. Moreover, by doing in this way, it can apply preferably also to a vehicle with a large engine rotation fluctuation | variation.

  In the present embodiment, an example in which the computer determination cycle is set to 100 msec and the threshold value is set to 10 rpm is described as a preferred embodiment, but these are not particularly limited. Moreover, when using in a motor bench etc., it replaces with | Nt-Ne | = Nte and should just use turbine rotation speed Nt. In this case, as shown in FIG. 6, the inequalities in the conditional expressions (A) to (D) are reversed and the threshold value may be a negative number.

1 is a diagram illustrating an overall configuration of an automatic transmission according to an embodiment of the present invention. It is a figure which shows the relationship between engagement / disengagement of a friction engagement element, and a gear stage. It is a cross-sectional schematic diagram of the wet multi-plate clutch illustrated as a friction engagement element. It is a figure showing the change of the oil pressure waveform used by the present invention, and turbine revolving speed Nt. It is a flowchart showing the flow of the setting process of the standby hydraulic pressure value of one embodiment of this invention. It is a figure for showing a change of turbine revolving speed near a judgment point, and explaining an example of judgment conditions. It is the figure which measured the actual pressure and turbine rotation change at the time of stepping up hydraulic pressure. It is a figure showing the waveform at the time of the upshift speed change of an automatic transmission.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automatic transmission 2 Transmission main body 3 Hydraulic control part 4 Electronic control part 10 Torque converter 10a Turbine 11 Input shaft 12 Output shaft 13 Turbine rotation sensor 14 Position sensor
15 Engine rotation sensor 31 Piston 32 Return spring 33 Clutch drum 34 Clutch hub 41 Learning mode switching means 42 Standby hydraulic pressure determination means 331 Driven plate 341 Drive plate B1, B2 Friction brake C1, C2, C3 Friction clutch G1 Double pinion planetary gear G2 , G3 single pinion planetary gear

Claims (4)

A plurality of friction engagement elements that constitute a plurality of shift speeds by a combination of engagement and disengagement, and a control unit that controls engagement / disengagement of the friction engagement elements by controlling the hydraulic pressure to be supplied. An automatic transmission having
Means for switching to a learning mode for learning a standby hydraulic pressure value after precharging;
Standby hydraulic pressure value determining means that is activated by switching to the learning mode and determines a standby hydraulic pressure value based on an input value consisting of at least the turbine speed,
When the vehicle is stopped and the learning mode is switched, the standby hydraulic pressure value determining means is
While maintaining the input shaft rotation speed of the automatic transmission, the control unit causes the friction engagement element to gradually increase the hydraulic pressure related to the friction engagement element for setting the standby hydraulic pressure value at predetermined time intervals. Move the element to the engagement side,
Further, the input value is measured and stored for a predetermined cycle in a predetermined determination cycle, and the difference value between the current input value and the input value before the predetermined determination cycle is calculated and stored.
In the current judgment cycle,
The change in the input value due to the decrease in the turbine speed satisfies the predetermined noise removal condition, and
When the difference value in the current determination cycle and the difference value in the previous determination cycle both exceed a predetermined threshold value, and the difference value in both determination cycles indicates a decreasing tendency of the turbine speed,
Learning and setting the oil pressure at the time as a standby oil pressure;
Automatic transmission characterized by. The automatic transmission according to claim 1, wherein
Having an engine speed input means,
The standby hydraulic pressure value determining means uses a difference value between the turbine speed and the engine speed as an input value,
Automatic transmission characterized by. A plurality of friction engagement elements that constitute a plurality of shift speeds by a combination of engagement and disengagement, a control unit that controls engagement / disengagement of the friction engagement elements by controlling the hydraulic pressure to be supplied, and at least A standby hydraulic pressure value determining means for determining a standby hydraulic pressure value based on an input value comprising a turbine rotational speed, and a standby hydraulic pressure value setting method after precharging of an automatic transmission,
In a state where the input shaft speed of the automatic transmission is maintained in a vehicle stop state,
The control unit gradually increases the hydraulic pressure related to the friction engagement element for setting the standby hydraulic pressure value at predetermined time intervals, and causes the friction engagement element to shift to the engagement side,
The standby hydraulic pressure determining means is
In the predetermined determination cycle, the input value is measured and stored for a predetermined number of cycles. Further, the difference value between the current input value and the input value before the predetermined determination cycle is calculated and stored.
In the current judgment cycle,
The change in the input value due to the decrease in the turbine speed satisfies the predetermined noise removal condition, and
When the difference value in the current determination cycle and the difference value in the previous determination cycle both exceed a predetermined threshold value, and the difference value in both determination cycles indicates a decreasing tendency of the turbine speed,
Learning and setting the oil pressure at the time as a standby oil pressure;
A method for setting a standby hydraulic pressure value. The standby hydraulic pressure value setting method according to claim 3,
The standby hydraulic pressure value determining means uses a difference value between the turbine speed and the engine speed as an input value,
A method for setting a standby hydraulic pressure value.

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