JP3678608B2 - Shift control device for automatic transmission - Google Patents

Abstract

An automatic speed change gear adapted to estimate the input shaft torque of a speed change gear from the engine torque and to control the oil pressure during speed change according to the input shaft torque, wherein the estimated value of the input shaft torque is retained at the value prevailing immediately before speed change decision for a period of time from the speed change decision till the rate of change of the engine rpm exceeds a predetermined value, and when the rate of change exceeds the predetermined value, the estimated value of engine torque is processed by a low-pass filter having a time constant corresponding to the engine rpm and an estimated value of input shaft torque is found on the basis of the estimated value of the engine torque that has passed through the low-pass filter.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shift control device for an automatic transmission, and more particularly to a device configured to perform a shift by changing friction engagement elements that simultaneously perform engagement control and release control of different friction engagement elements.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an apparatus configured to change gears by switching friction engagement elements that simultaneously perform engagement control and release control of different friction engagement elements is disclosed in Japanese Patent Laid-Open Nos. 9-133205 and 5-164233. Is disclosed.
[0003]
For example, in the one disclosed in Japanese Patent Laid-Open No. 9-133205, in the transmission downshift, the transmission torque capacity of the friction engagement element on the high speed side is a value at which the output shaft torque does not become negative within the first time at the beginning of shifting. In the second time thereafter, the transmission torque capacity of the friction engagement element on the high speed side is increased to the same level as the input shaft torque, and the transmission torque capacity of the friction engagement element on the low speed side is set appropriately. After the second time, the transmission torque capacity of the low speed side frictional engagement element is increased to the input shaft torque or more, and the high speed side frictional engagement element is released.
[0004]
Japanese Patent Laid-Open No. 5-164233 discloses a configuration in which an engine torque generation delay adjustment is performed in the automatic transmission that performs the change-over shift so as to improve the accuracy of control according to the input shaft torque. Specifically, adjustment is performed to match that there is a slight time delay until the engine output corresponding to the intake air amount Q / rotational speed N is obtained.
[0005]
[Problems to be solved by the invention]
However, in a shift where the input shaft torque changes abruptly (for example, a downshift associated with depression of the accelerator: a power-on downshift), a relatively large dead time occurs and the input shaft torque starts to change in response. Since the response speed is not constant, it is difficult to adjust the generation delay with high accuracy, and the engagement hydraulic pressure does not correspond to the actual input shaft torque, resulting in a problem that the transmission performance is deteriorated.
[0006]
That is, Japanese Patent Laid-Open No. 5-164233 discloses a configuration for adjusting the time delay. For example, the estimated value of the input shaft torque is set to a constant characteristic 1 with respect to the intake air amount Q / rotational speed N. With a configuration that responds with the next delay, the time constant changes according to the operating conditions, and the dead time is different, so especially when the change of the input shaft torque is abrupt, such as during power-on downshift, A large error is generated between the actual input shaft torque and the estimated value, and the engagement hydraulic pressure at the time of the change gear shift cannot be controlled with high accuracy, and the shift performance may be impaired.
[0007]
The present invention has been made in view of the above-mentioned problems, and enables the generation delay adjustment to be performed with high accuracy, thereby improving the estimation accuracy of the input shaft torque, so that the engagement hydraulic pressure at the time of change gearing can be improved. The purpose is to improve the control accuracy.
[0008]
[Means for Solving the Problems]
Therefore, the invention described in claim 1 is a shift control device for an automatic transmission configured to perform a shift by switching friction engagement elements that simultaneously perform engagement control and release control of different friction engagement elements .
Engine torque estimating means for estimating engine torque based on a parameter for changing engine torque;
The time from the shift determination until the change speed of the engine rotation speed exceeds a predetermined value is determined as a dead time in the response characteristic of the engine torque with respect to the change in the parameter, and the input shaft torque of the transmission mechanism based on the engine torque in the dead time is determined. Dead time processing means for maintaining the estimated value at a value immediately before the shift determination;
When the change speed of the engine rotation speed exceeds the predetermined value after the shift determination, the engine torque is processed by a low-pass filter having a time constant set according to the engine rotation speed, and the result processed by the low-pass filter is input. Low-pass filter means for estimating the shaft torque;
Engagement oil pressure control means for controlling the engagement oil pressure of the friction engagement element at the time of shifting based on the estimated value of the input shaft torque;
It is comprised including.
[0011]
According to such a configuration, estimates the engine torque from the parameters to change the engine torque, the response delay characteristics of the actual input shaft torque versus the estimated value, identified as dead time and the time constant, the parameter is changed However, the input shaft torque is estimated on the assumption that an actual change appears after the dead time elapses and changes according to the time constant.
For example, during a power-on downshift, the engine rotation speed is defined as a dead time from when a shift determination (shift down request) is made based on a change in throttle opening until the engine speed change speed exceeds a predetermined value. From the time when the speed change speed exceeds a predetermined value, the input shaft torque is estimated on the assumption that the actual response change of the input shaft torque occurs with a time constant corresponding to the engine speed at that time.
[0012]
According to a second aspect of the present invention, the engine torque estimating means estimates the engine torque based on an engine intake air flow rate or a throttle opening and an engine speed as a parameter for changing the engine torque.
[0013]
According to this configuration, the engine torque is estimated based on the intake air amount of the engine and the engine rotation speed, or the throttle opening and the engine rotation speed .
[0016]
【The invention's effect】
According to the first aspect of the present invention, it is possible to easily and reliably determine the dead time in the response change of the input shaft torque, to avoid erroneously estimating the response change of the input shaft torque within the dead time, and further to the engine There is an effect that the input shaft torque can be estimated with high accuracy corresponding to the difference in the response time constant of the input shaft torque depending on the rotation speed .
[0017]
According to the invention of claim 2, there is an effect that the engine torque can be estimated with a simple configuration .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 shows a speed change mechanism in an automatic transmission according to an embodiment. An input shaft I / S to which a rotational driving force is transmitted from a crankshaft C / S of an engine via a torque converter T / C, An output shaft O / S arranged coaxially with the input shaft I / S, a first planetary gear set G1 and a second planetary gear set G2 provided coaxially on these input / output shafts, and various fluid friction engagements Composed of elements.
[0020]
L / C denotes a lockup clutch provided in the torque converter T / C.
The first planetary gear set G1 includes a simple planetary gear set including a sun gear S1, a ring gear R1, a pinion P1 meshing with the sun gear S1, and a pinion carrier PC1 that rotatably supports the pinion P1. The second planetary gear set G2 is also a simple planetary gear set including a sun gear S2, a ring gear R2, a pinion P2 meshing with the sun gear S2, and a pinion carrier PC2 that rotatably supports the pinion P2.
[0021]
The various fluid frictional engagement elements include first to third clutches C1, C2, C3, a first brake B1, a second brake B2, and a one-way clutch OWC.
[0022]
The carrier PC1 can be coupled to the input shaft I / S via the second clutch C2, the sun gear S1 can be fixed by the second brake B2, and the input shaft I / S can be fixed by the first clutch C1. It is fixed to S and configured to prevent reverse rotation via a one-way clutch OWC.
[0023]
The ring gear R1 is integrally coupled to the carrier PC2 and is drivably coupled to the output shaft O / S, and the sun gear S2 is coupled to the input shaft I / S. The ring gear R2 is configured to be connectable to the carrier PC1 via the third clutch C3.
[0024]
The first to third clutches C1, C2, C3, the first brake B1, and the second brake B2 are each operated by supplying hydraulic pressure to perform the coupling and fixing. As shown in FIG. By operating the first to third clutches C1, C2, C3, the first brake B1, and the second brake B2 in various combinations (indicated by ◯), the planetary gear is coupled with the operation of the one-way clutch OWC. By changing the rotation state of the elements constituting the group G1, G2, and thereby changing the rotation speed ratio of the output shaft O / S with respect to the rotation speed of the input shaft I / S, the forward fourth speed and the reverse first speed are obtained. be able to.
[0025]
The first brake B1 is operated at the first speed when the engine brake is required at the first speed. When the first brake B1 is not operated, the one-way clutch OWC receives the reaction force and the first speed is increased. Realized, engine braking becomes impossible due to idling of the one-way clutch OWC.
[0026]
Here, for example, when the upshift from the third speed to the fourth speed is performed, the release of the third clutch C3 and the engagement of the second brake B2 are performed simultaneously, and when the downshift from the fourth speed to the third speed is performed, The engagement of the third clutch C3 and the release of the second brake B2 are performed at the same time, and a shift is performed by such a change of the friction engagement elements.
[0027]
Control of the engagement hydraulic pressure of the friction engagement element in the change gear shift is performed by a configuration as shown in FIG.
In FIG. 3, an input shaft torque estimation unit A estimates the input shaft torque of the speed change mechanism. The estimation of the input shaft torque estimation will be described in detail later.
[0028]
The torque sharing ratio setting unit B sets a torque sharing ratio for gradually switching the sharing of torque transmission from the disengagement side frictional engagement element to the engagement side frictional engagement element during gear shifting.
[0029]
Then, in the necessary torque calculation unit C, based on the input shaft torque estimated and calculated by the input shaft torque estimation unit A and the torque sharing ratio set by the torque sharing ratio setting unit B, the required torque calculation unit C at the time of shifting according to the following equation: The required torque of each friction engagement element is calculated.
[0030]
Necessary torque = Torque sharing ratio × Estimated input shaft torque × Gain required hydraulic pressure calculation unit D calculates the hydraulic pressure required to obtain the required torque of each friction engagement element calculated by the required torque calculation unit C in the case of a clutch. For example, the calculation is performed according to the following formula.
[0031]
Required oil pressure = 1 / A {(T · i) / (N · μ · D) + F}
Where A is the clutch piston area (cm ² ), T is the estimated input shaft torque (kg · m), μ is the coefficient of friction, D is the effective facing diameter, N is the number of clutches, i is the torque sharing ratio, and F is the return Spring reaction force.
[0032]
When the required hydraulic pressure is calculated, a control signal corresponding to the required hydraulic pressure is obtained, and the control signal is output to a solenoid valve that controls the hydraulic pressure supplied to the friction engagement element to control the required hydraulic pressure (engagement hydraulic pressure). Control means).
[0033]
The flowchart of FIG. 4 shows the estimation process of the input shaft torque T in the input shaft torque estimation unit A, and will be described below with reference to the time chart of FIG.
[0034]
Note that the time chart of FIG. 5 shows an example of a downshift from the 3rd speed to the 2nd speed.
In step S21, a shift determination is made, and if it is a shift, the process proceeds to step S22, and the engine torque is estimated based on the intake air flow rate of the engine and the engine rotation speed (engine torque estimating means).
[0035]
In step S22, the engine torque is estimated based on the intake air flow rate and the engine rotation speed, which are parameters for changing the engine torque. However, the throttle opening is used instead of the intake air flow rate. Also good.
[0036]
In the next step S23, it is determined whether or not the change amount ΔN (change speed) per unit time of the engine rotation speed exceeds a predetermined value ΔNs.
Then, until the change amount ΔN (change speed) exceeds the predetermined value ΔNs, it is determined that it is within the dead time until the change of the input shaft torque starts to appear with respect to the accelerator opening change (throttle opening change). Then, the process proceeds to step S24, and a process for holding the input shaft torque estimated value immediately before the shift determination is performed (response characteristic value determining means).
[0037]
The process of holding the estimated input shaft torque is a value obtained by correcting the engine torque obtained from the intake air flow rate or throttle opening just before the shift determination and the engine rotational speed at that time by the torque ratio of the torque converter. Processing for torque may be used.
[0038]
On the other hand, when it is determined that the change amount ΔN (change speed) exceeds the predetermined value ΔNs, it is determined that the engine torque starts to change with respect to the accelerator opening change (throttle opening change), and the process proceeds to step S25. move on.
[0039]
In step S25, a time constant in the response change of the engine torque is set based on the engine speed at that time (response characteristic value determining means). Here, as shown in FIG. 6, the time constant is set so that the delay increases as the engine speed decreases.
[0040]
In step S26, the estimated value of the engine torque is processed by the low-pass filter having the set time constant. In step S27, the result processed by the low-pass filter is set as the input shaft torque T (input shaft torque estimating means). .
[0041]
Here, before or after processing with the low-pass filter, it is preferable to perform correction according to the torque ratio of the torque converter and set the processing result to the input shaft torque T.
[0042]
Note that the engagement hydraulic pressure control in the change gear shift is not limited to the above, and any configuration may be used as long as the engagement hydraulic pressure is controlled according to the input shaft torque. Obviously, the structure of the speed change mechanism is not limited to that shown in FIG.
[Brief description of the drawings]
FIG. 1 is a diagram showing a transmission mechanism of an automatic transmission according to an embodiment.
FIG. 2 is a diagram showing a correlation between a combination of operating states of friction engagement elements in the speed change mechanism and a gear position;
FIG. 3 is a control block diagram showing an outline of shift control of the automatic transmission.
FIG. 4 is a flowchart showing estimation control of input shaft torque.
FIG. 5 is a diagram showing characteristics of a response delay time constant in the estimation of the input shaft torque.
FIG. 6 is a time chart showing characteristics of estimation of the input shaft torque.
[Explanation of symbols]
A ... Input shaft torque estimation unit B ... Torque sharing ratio setting unit C ... Necessary torque calculation unit D ... Necessary oil pressure calculation unit B1, B2 ... Brake C1, C2, C3 ... Clutch G1, G2 ... Planetary gear set I / S ... Input Axis O / S ... Output shaft OWC ... One-way clutch T / C ... Torque converter

Claims (2)

In a shift control device for an automatic transmission configured to perform shift by changing friction engagement elements that simultaneously perform engagement control and release control of different friction engagement elements,
Engine torque estimating means for estimating engine torque based on a parameter for changing engine torque;
The time from the shift determination until the change speed of the engine rotation speed exceeds a predetermined value is determined as a dead time in the response characteristic of the engine torque with respect to the change in the parameter, and the input shaft torque of the transmission mechanism based on the engine torque in the dead time is determined. Dead time processing means for maintaining the estimated value at a value immediately before the shift determination;
When the change speed of the engine rotation speed exceeds the predetermined value after the shift determination, the engine torque is processed by a low-pass filter having a time constant set according to the engine rotation speed, and the result processed by the low-pass filter is input. Low-pass filter means for estimating the shaft torque;
Engagement oil pressure control means for controlling the engagement oil pressure of the friction engagement element at the time of shifting based on the estimated value of the input shaft torque ;
A shift control device for an automatic transmission, comprising: 2. The automatic transmission according to claim 1, wherein the engine torque estimating means estimates the engine torque based on an engine intake air flow rate or a throttle opening and an engine speed as a parameter for changing the engine torque. Shift control device.

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