JP3600714B2 - Control device for automatic transmission - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an automatic transmission, and more specifically, in an automatic transmission that controls the oil pressure of a friction engagement element according to a control signal, learns the correlation between the control signal and the oil pressure, and adjusts the control accuracy of the oil pressure. Technology for improving.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a vehicle automatic transmission, when a friction engagement element such as a clutch is engaged, first, hydraulic fluid is precharged, and then the return pressure is maintained just before the engagement force is generated. There is known a configuration in which the hydraulic pressure is controlled so as to advance the fastening of the elements (see Japanese Patent Application Laid-Open No. 8-334171). Note that the return pressure is a pressure corresponding to the spring force of the return spring that urges the friction engagement element in the release direction.
[0003]
Further, there has also been proposed a shift control device configured to learn the return pressure (precharge pressure) to avoid occurrence of a delay in engagement of a friction engagement element (see Japanese Patent Application Laid-Open No. 5-106722, etc.). ).
[0004]
[Problems to be solved by the invention]
By the way, by learning the return pressure, it is possible to accurately maintain the state immediately before the fastening force is generated, thereby ensuring the responsiveness of the subsequent hydraulic control. This is more often due to a deviation in the correlation between the control signal for the solenoid valve for controlling the hydraulic pressure and the actually obtained hydraulic pressure than to the variation in force.
[0005]
That is, even if the control signal corresponding to the required oil pressure is output to the solenoid valve in order to supply the oil pressure corresponding to the spring force of the return spring, if the actual oil pressure obtained for the control signal varies, the spring The hydraulic pressure corresponding to the force cannot be obtained, and the control signal needs to be corrected by learning.
However, conventionally, since only the learning of the return pressure is performed, in the subsequent control of the engagement pressure, it is not possible to control to a desired hydraulic pressure due to a difference in correlation between the hydraulic pressure and the control signal, and as a result, There was a possibility of causing a shift shock or the like.
[0006]
The present invention has been made in view of the above problems, and has as its object to enable correction of a correlation between a control signal and hydraulic pressure, thereby improving hydraulic pressure control accuracy.
[0007]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 includes an elastic member for urging the friction engagement element in the release direction, and controls the hydraulic pressure of the friction engagement element by a control signal to release and fasten the friction engagement element. In the control device for an automatic transmission configured to control the control signal when the elastic member is in a predetermined state, based on a reference pressure stored in advance corresponding to the predetermined state, The configuration is such that the relative relationship between the control signal and the hydraulic pressure is learned.
[0009]
According to this configuration, the control signal when the elastic member is brought into the predetermined state by applying the hydraulic pressure against the urging force of the elastic member (return spring or the like) is required to obtain the predetermined state. This corresponds to a pre-stored reference pressure, whereby the relative relationship between the control signal and the hydraulic pressure is learned. That is, the elastic member corresponds to the control factor that requires a constant hydraulic pressure in the first aspect.
[0010]
According to the second aspect of the invention, when the friction engagement element is fastened, the hydraulic oil is precharged, and then the return pressure is maintained at a return pressure for stroke until just before the fastening force is generated against the elastic member. The control signal is output in order to advance the engagement of the friction engagement element.The control signal for obtaining the return pressure is learned, and based on the learning result and a return pressure as a reference pressure stored in advance. In this configuration, the relative relationship between the control signal and the hydraulic pressure is learned.
[0011]
According to this configuration, the predetermined state of the elastic member is a state in which a hydraulic pressure corresponding to a spring force acting in a releasing direction of the elastic member is supplied, and the friction engagement element is stroked to just before the engagement. The control signal for obtaining the state immediately before the engagement is learned, and the relative relationship between the control signal and the oil pressure is learned from the reference pressure corresponding to the urging force of the elastic member and the control signal for obtaining the state immediately before the engagement.
[0012]
The learning of the return pressure is performed by, for example, detecting that excessive return pressure is detected based on torque pull-in or rotation decrease in a configuration in which the two frictional engagement elements are simultaneously released and engaged to perform a gear shift. Can be done.
According to the third aspect of the present invention, a hydraulic switch for detecting a hydraulic pressure of the friction engagement element is provided, and the control signal when the elastic member is brought into a predetermined state and the control signal stored in advance corresponding to the predetermined state are stored. And learning the relative relationship between the control signal and the hydraulic pressure based on the reference pressure and learning the relative relationship between the control signal and the hydraulic pressure based on the control signal at the switching point of the hydraulic switch. .
[0013]
According to this configuration, the relative relationship between the control signal and the hydraulic pressure is learned at two points, that is, the hydraulic pressure at which the elastic member is brought into a predetermined state and the hydraulic pressure at which the hydraulic switch is switched.
[0014]
【The invention's effect】
According to the first aspect of the present invention, the relative relationship between the hydraulic pressure and the control signal is learned based on the biasing force of the elastic member which is hardly affected by disturbances such as input torque and temperature. Can be correctly corrected, so that the hydraulic pressure supplied to the friction engagement element can be controlled with high accuracy.
[0015]
According to the second aspect of the present invention, by setting the state in which the friction engagement element is stroked immediately before the engagement to the predetermined state of the elastic member, it is possible to accurately learn a control signal corresponding to the urging force of the elastic member, Thus, there is an effect that the relative relationship between the hydraulic pressure and the control signal can be correctly corrected.
[0016]
According to the third aspect of the present invention, the relative relationship between the control signal and the hydraulic pressure is learned based on both the control signal when the elastic member is brought into the predetermined state and the control signal at the switching point of the hydraulic switch. This has the effect that the relative relationship can be corrected with higher accuracy.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a diagram showing a system configuration of an automatic transmission according to the present invention. An output torque of an engine 1 mounted on a vehicle (not shown) is transmitted to drive wheels via an automatic transmission 2.
[0018]
The automatic transmission 2 has a configuration in which a shift is performed by controlling the supply of operating hydraulic pressure to frictional engagement elements such as a clutch and a brake by a solenoid valve unit 3, and more specifically, shown in FIG. Thus, the configuration is such that the output torque of the engine is input via the torque converter T / C, and includes the front planetary gear set 83 and the rear planetary gear set 84, and the reverse clutch R / C, A high clutch H / C, a band brake B / B, a low & reverse brake L & R / B, and a forward clutch FWD / C are provided. In FIG. 2, reference numeral 81 denotes an input shaft of the transmission, 82 denotes an output shaft of the transmission, Ne denotes an engine rotation speed, Nt denotes a turbine rotation speed, and No denotes an output shaft rotation speed.
[0019]
In the above configuration, as shown in FIG. 3, the combination of the engagement and disengagement of the reverse clutch R / C, high clutch H / C, band brake B / B, low & reverse brake L & R / B, and forward clutch FWD / C. The shift is performed accordingly, for example, at the time of the upshift from the third speed to the fourth speed, the release of the forward clutch FWD / C and the engagement of the band brakes B / B are performed simultaneously. That is, the automatic transmission 2 according to the present embodiment is configured to execute a shift (so-called clutch-to-clutch shift) in which the two friction engagement elements are simultaneously engaged and released without using the one-way clutch. (See FIG. 4).
[0020]
The control unit 4 stores a table indicating a correlation between a control signal (current control signal) for each solenoid valve of the solenoid valve unit 3 and a hydraulic pressure, and obtains a control signal corresponding to a required hydraulic pressure by table conversion. Output to the solenoid valve to control the current flowing through the solenoid.
In the engagement control of a friction engagement element such as a clutch, as shown in FIG. 4, first, a precharge is performed to cause an invalid stroke of the friction engagement element until immediately before contact, and then the operating oil pressure is reduced to just before the engagement force is generated. , And then control the operating oil pressure so that the engagement of the friction engagement element proceeds at a predetermined timing. The return pressure is a pressure corresponding to the spring force of a return spring (elastic member) for urging the friction engagement element in the release direction.
[0021]
Here, the control unit 4 controls the oil pressure as described above when the friction engagement element is engaged, and learns the return pressure (instruction value).
In the learning of the return pressure, as shown in the flowchart of FIG. 5, it is determined whether or not the pull-in of the torque (see FIG. 4) when maintaining the return pressure is larger than an allowable value (S1). If the pull-in torque is larger than the allowable value, it is determined that the return pressure is excessive, and the return pressure is reduced by a predetermined value (S2), while if the pull-in torque is smaller than the allowable value (S3). When it is determined that the return pressure can be increased, the return pressure is increased by a predetermined value (S4), and the return pressure at which the pull-in torque becomes close to the allowable value as a result is learned.
[0022]
If the return pressure is excessive, a state in which the engagement operation is relatively too early with respect to the release operation (hereinafter, this state is referred to as an interlock) will increase the torque withdrawal. Then, an appropriate return pressure, that is, a hydraulic pressure that can be maintained just before the engagement in accordance with the spring force of the return spring is learned.
[0023]
The magnitude of the allowable value of the pull-in torque with respect to the allowable value is, specifically, a value indicating the pull-in torque while the minimum torque Pmin at the time when the torque is reduced while the return pressure is held, while the torque after the end of the torque phase and the inertia phase. When the minimum torque Pmin is lower than the reference torque Ps / l, it is determined that the pull-in of the torque is larger than an allowable value. Conversely, the minimum torque Pmin exceeds the reference torque Ps / l. Sometimes, it is determined that the pull-in of the torque is smaller than the allowable value.
[0024]
In the learning of the return pressure, when the initial value is corrected based on the pull-in of the torque when the control signal corresponding to the initial value of the return pressure is output, the control signal corresponding to the corrected return pressure is transmitted to the next shift. It is output at times to approach the expected return pressure for each shift.
Instead of determining whether the return pressure is too high or too low based on the pull-in of the torque, the interlock is determined based on the engine rotation fluctuation, and the return pressure is increased so as to increase the return pressure within a range where the interlock does not occur. The pressure may be learned. That is, if the occurrence of the interlock can be detected, the return pressure can be learned based on the detection result, and the learning method (interlock detection method) is not limited to the above.
[0025]
Incidentally, the return pressure is required in accordance with the spring force of the return spring, in other words, the hydraulic pressure required to bring the return spring into a predetermined state. It is a control factor that is hardly affected by disturbances such as temperature conditions. Therefore, if the expected oil pressure is obtained by the output of the control signal to the solenoid valve, there is almost no need for correction by learning. In other words, the amount of correction required by learning is converted to the control signal. On the other hand, it can be presumed that it is due to the variation in the hydraulic pressure actually obtained.
[0026]
Therefore, as shown in FIG. 6, a result of learning the return pressure, that is, a hydraulic pressure corresponding to a control signal when an appropriate return pressure is obtained on a hydraulic-control signal conversion table before correction, The return pressure is compared with a design return pressure (a reference pressure corresponding to the spring force of the return spring) stored in advance, and the conversion table of the hydraulic pressure-control signal is corrected based on the comparison result.
[0027]
For example, as shown in FIG. 7, on the conversion table before correction, it was learned that a return pressure of 100 KPa was required to bring the friction engagement element into a state immediately before engagement, whereas the return pressure When the design value of is 80 KPa, by outputting a value corresponding to 100 KPa as a control signal, only 80 KPa is actually obtained. Therefore, the control signal corresponding to 100 KPa is changed to 80 KPa. In order to correspond, the relative relationship between the control signal and the oil pressure is shifted in the negative direction by 20 KPa as a whole (the characteristic line is shifted downward by 20 KPa in the figure in parallel).
[0028]
As described above, the required return pressure can be correctly obtained by correcting the conversion table of the hydraulic pressure-control signal, and the required pressure can be accurately controlled in the subsequent engagement pressure control and release pressure control. As a result, the engagement and disengagement of the friction engagement element can be controlled with high precision, and high gear shifting performance can be exhibited.
Here, in the case of a configuration in which the friction engagement element such as the clutch is provided with a hydraulic switch (see FIG. 8) whose output is switched ON / OFF based on a predetermined hydraulic pressure for fail-safe or the like, As described above, the conversion table of the hydraulic pressure-control signal may be corrected based on the learning result of the return pressure, and the correction based on the control signal at the ON / OFF switching point of the hydraulic switch may be performed.
[0029]
Specifically, the control signal when the ON / OFF switching of the hydraulic switch occurs is learned, and, for example, a point defined by a design value of the return pressure and a control signal corresponding thereto, The inclination of the characteristic line is corrected so as to pass through two points, ie, a point defined by the hydraulic pressure at which the output changes and a control signal corresponding thereto (see FIG. 8).
[0030]
As described above, if the learning using the hydraulic switch is also used, the conversion table of the hydraulic pressure-control signal can be corrected more accurately.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an automatic transmission to which the present invention is applied.
FIG. 2 is a configuration diagram showing details of an automatic transmission.
FIG. 3 is a diagram showing a state of a shift by a combination of engagement states of friction engagement elements in the automatic transmission.
FIG. 4 is a time chart showing a state of hydraulic control during shifting.
FIG. 5 is a flowchart showing how return pressure is learned.
FIG. 6 is a diagram showing a basic configuration of learning control of a hydraulic-control signal conversion table.
FIG. 7 is a diagram showing how a conversion table is corrected.
FIG. 8 is a diagram showing a state of conversion table correction using a result of a hydraulic switch together.
[Explanation of symbols]
Reference Signs List 1 engine 2 automatic transmission 3 solenoid valve unit 4 control unit 83 front planetary gear set 84 rear planetary gear set R / C reverse clutch H / C high clutch B / B band brake L & R / B low & reverse brake FWD / C forward clutch

Claims (3)

An automatic transmission having an elastic member for urging the frictional engagement element in the release direction and controlling release and engagement of the frictional engagement element by controlling a hydraulic pressure of the frictional engagement element by a control signal . In the control device,
Learning the relative relationship between the control signal and the hydraulic pressure based on the control signal when the elastic member enters a predetermined state and a reference pressure stored in advance corresponding to the predetermined state. Control device for automatic transmission. When the friction engagement element is fastened, the hydraulic oil is precharged, and then maintained at the return pressure that causes the stroke to occur immediately before the fastening force is generated against the elastic member, and then the fastening of the friction engagement element proceeds. Output the control signal to cause
A control signal for obtaining the return pressure is learned, and a relative relationship between the control signal and a hydraulic pressure is learned based on the learning result and a return pressure as a reference pressure stored in advance. 2. The control device for an automatic transmission according to claim 1 . A hydraulic switch for detecting the hydraulic pressure of the friction engagement element is provided, based on the control signal when the elastic member is in a predetermined state, and a reference pressure stored in advance corresponding to the predetermined state, The method according to claim 1 or 2 , wherein the relative relationship between the control signal and the hydraulic pressure is learned, and the relative relationship between the control signal and the hydraulic pressure is learned based on a control signal at a switching point of the hydraulic switch. A control device for the automatic transmission according to the above.

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