JP3596077B2 - Control device for automatic transmission - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a control device for an automatic transmission.
[0002]
[Prior art]
In general, automatic transmissions are provided with a planetary gear type multi-stage transmission gear mechanism, which performs a gear shift by switching an operation state of a frictional engagement element such as a brake or a clutch to switch a power transmission path. I have. The brake for switching the power transmission path is often of a band brake type having a brake band (brake drum). In such an automatic transmission, it has been proposed to variably control the working oil pressure in accordance with the temperature of the working oil in order to prevent the shift response from deteriorating due to the viscosity change of the working oil of the frictional engagement element ( (See JP-A-64-35154)
[0003]
[Problems to be solved by the invention]
By the way, in the above-described band brake type friction fastening element, the coefficient of friction between the brake band and the brake drum is extremely large at low temperatures as compared with high temperatures, so that at the same operating hydraulic pressure as at high temperatures at low temperatures. If the band brake type frictional engagement element is engaged in this way, the shock at the time of shifting to a specific shift speed obtained by engaging the band brake type frictional engagement element will be large. For this reason, it is conceivable to lower the operating oil pressure when shifting to the specific gear stage.
[0004]
However, lowering the operating oil pressure requires a predetermined amount of oil pressure regardless of the temperature in order to engage the band brake frictional engagement element. Therefore, the shelf pressure by the accumulator or the like (intermediate hydraulic pressure during shifting) is required. ) In some cases, formation may not be successful, and conversely, the shift shock may increase.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in an automatic transmission in which a specific gear is obtained by engaging a predetermined frictional engagement element of a band brake type, a shift at a low temperature is provided. An object of the present invention is to provide a control device for an automatic transmission that can reliably prevent a shock.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration. That is,
In an automatic transmission configured to obtain a specific gear by switching a power transmission path by engaging a predetermined friction engagement element of a band brake type,
Temperature detection means for detecting a value related to the temperature of the predetermined frictional engagement element,
Prohibition means for prohibiting a shift to the specific shift speed when it is determined from the detection result of the temperature detection means that the temperature of the friction engagement element is equal to or lower than a predetermined temperature;
Is provided. Preferred embodiments of the present invention based on the above configuration are as described in claims 2 and 3 in the claims.
[0007]
【The invention's effect】
According to the first aspect of the present invention, the shift to a specific shift speed at which the shift shock at a low temperature becomes a problem is prohibited, so that the shift shock can be reliably prevented.
[0008]
With the configuration as described in claim 2, the temperature of the band brake type frictional engagement element is detected instead of the temperature of the hydraulic oil, and temperature detection becomes easy. In particular, since an automatic transmission generally includes a temperature detection unit for hydraulic oil, it is not necessary to separately provide a temperature detection unit dedicated to a predetermined frictional engagement element.
[0009]
By adopting the configuration as described in claim 3, it is preferable to prevent hunting and to surely confirm that the temperature has risen to a temperature at which no shift shock occurs by setting the hysteresis by the switching delay means. Become.
[0010]
The configuration as described in claim 4 is preferable for preventing a shift shock when the engine is under a low load, in which a shift shock is particularly problematic. In addition, when the engine is under a high load, the shift shock does not cause much problem, while running using a specific shift speed, that is, acceleration is obtained.
[0011]
With the configuration as described in claim 5, the shift shock can be prevented by a simple method of switching the shift characteristics. Further, it is preferable to set the shift characteristic for the cold state to one that does not support running or the like, by sufficiently considering that a specific gear position cannot be set.
[0012]
The configuration as described in claim 6 is preferable in preventing a shock due to switching of the shift characteristic.
[0013]
With the configuration as described in claim 7, the same effect as the effect corresponding to claim 3 can be obtained.
[0014]
By adopting the configuration as described in claim 8, the shift characteristic for the cold state is set to one that does not support running, etc., taking into account that it is not possible to take a specific gear stage. Can be.
[0015]
(Example)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, the automatic transmission includes a torque converter 1, a multi-gear transmission mechanism 2, and an overdrive planetary gear transmission mechanism 3 disposed between the torque converter 1 and the multi-gear transmission mechanism 2. And
[0016]
The torque converter 1 includes a pump impeller (hereinafter abbreviated as “pump”) 5 connected to an engine output shaft 4 and a turbine runner (hereinafter “turbine”) arranged opposite to the pump 5. ), And a stator 7 disposed between the pump 5 and the turbine 6. The converter 6 is connected to the converter output shaft 8. A lock-up clutch 9 is provided between the converter output shaft 8 and the pump 5. The lock-up clutch 9 is constantly urged in the direction of engagement by the hydraulic oil pressure circulating in the torque converter 1, and is maintained in an open state when an opening hydraulic pressure is supplied from the outside.
[0017]
The multi-stage gear transmission 2 has a front planetary gear mechanism 10 and a rear planetary gear mechanism 11, and a sun gear 12 of the front planetary gear mechanism 10 and a sun gear of the rear planetary gear mechanism 11 are connected by a connection shaft 14. The input shaft 15 of the multi-gear transmission mechanism 2 is connected to a connection shaft 14 via a front clutch 16 and to an internal gear 18 of a front planetary gear mechanism 10 via a rear clutch 17. A second brake 19 for selecting the second speed is provided between the coupling shaft 14, that is, the sun gears 12, 13 and the transmission case C. The planetary carrier 20 of the front planetary gear mechanism 10 and the internal gear 21 of the rear planetary gear mechanism 11 are connected to an output shaft 22. A low reverse brake 24 and a one-way clutch 25 are provided between the planetary carrier 23 of the rear stage planetary gear mechanism 11 and the transmission case C.
[0018]
The multi-stage gear transmission mechanism 2 has a conventionally known transmission mechanism, and has three forward speeds and one reverse speed, and has a front clutch 16, a rear clutch 17, a second brake 19, a low The required gear stage can be obtained by appropriately operating the reverse brake 24 with a hydraulic actuator as described later.
[0019]
The overdrive planetary gear transmission mechanism 3 has a planetary carrier 27 that rotatably supports a planetary carrier 26 and a sun gear 29 that is connected to the internal gear 30 via a direct clutch 29. An overdrive brake 31 is provided between the sun gear 29 and the transmission case C, and the internal gear 30 is connected to the input shaft 15 of the multi-gear transmission mechanism 2.
[0020]
When the direct clutch 29 is engaged and the overdrive brake 31 is released, the converter output shaft 8 and the input shaft 15 are directly connected to each other. After that, when the overdrive brake 31 is engaged and the direct clutch 29 is released, the converter output shaft 8 and the input shaft 15 are overdriven. Works.
[0021]
In this transmission, a manual valve of a hydraulic control circuit, which will be described later, is manually operated to select each friction member (clutch and brake) of the multi-stage gear transmission mechanism 2 and the overdrive planetary gear transmission mechanism 3. Is appropriately operated to obtain a required shift speed, and the control pattern of each friction member is set as shown in FIG. 2 for each range similarly to the conventional structure.
[0022]
FIG. 3 shows a control system for performing a shift control. In the figure, reference numeral U denotes a control unit constituted by using a microcomputer, and the control unit U has signals from the sensors S1 to S3. Is entered. The sensor S1 detects a vehicle speed. The sensor S2 detects an engine load (in the embodiment, a throttle opening). The sensor S3 detects the temperature of the hydraulic oil of the friction engagement element of the automatic transmission (temperature detection means), and detects the temperature of the second brake 19 as a predetermined friction engagement element in the claims. It is assumed.
[0023]
The control unit U controls a shift valve (shift valve) incorporated in a hydraulic circuit of the automatic transmission to control operations of various friction engagement elements shown in FIGS. That is, the shift control is performed so that the shift speed is determined based on the shift characteristics described later (the operation states of the various friction engagement elements are switched and controlled in accordance with the mode shown in FIG. 2).
[0024]
As the shift characteristics used for the shift control, two types of shift characteristics shown in FIGS. 6 and 7 are stored in the ROM of the control unit U in advance. The shift characteristics shown in FIG. 6 are for normal use, that is, for warm use, and are set so that all shift speeds from the first to fourth speeds can be taken. The shift characteristics shown in FIG. 7 are for cold use, and are set so that three shift speeds of first, third, and fourth speeds can be taken, excluding the second speed as a specific shift speed. Have been. That is, in the embodiment, since the specific shift speed obtained when the second brake 19 as the band brake type friction engagement element is engaged is the second speed (see FIG. 2), the second speed is excluded. Then, the shift characteristic for cold state shown in FIG. 7 is set.
[0025]
Further, the shift characteristic for the cold state in FIG. 7 is set as follows in comparison with the shift characteristic for the warm state in FIG. That is, in the cold shift characteristic, the 1-3 shift characteristic line of both the upshift line and the downshift line corresponds to the 1-2 shift characteristic line and the 2-3 shift characteristic line in the warm shift characteristic. It is set to be between. That is, as compared with the shift characteristic for the warm state, the region of the first speed, which is one step lower than the second speed as the specific gear, is expanded to the higher speed side, and the speed of one step is higher than the second speed. The third speed region on the side is expanded to a lower speed side. Note that the shift characteristic line between the third speed and the fourth speed is set to be the same as the warm speed shift characteristic.
[0026]
The details of the shift control by the control unit U will be described with reference to a flowchart shown in FIG. 8, where Q indicates a step in the following description. After a signal is input from the sensor in Q1 in FIG. 8, it is determined in Q2 whether the engine load detected by the sensor S2 is at a low load equal to or less than a predetermined load. If the determination in Q2 is YES, it is determined in Q3 whether the temperature detected by the sensor S3 is a low temperature equal to or lower than a predetermined temperature (for example, 40 ° C.).
[0027]
If the determination in Q3 is YES, in Q4, the shift characteristic for cold state shown in FIG. 7 is selected, and then in Q5, the gear stage gL is determined based on the shift characteristic for cold state. Thereafter, in Q6, after the gear stage gL is set to the final gear stage gF (execution of the final gear stage gF), the flag is set to 1 in Q7, and thereafter, the process returns to Q1.
[0028]
When the determination in Q2 is NO or the determination in Q3 is NO, the process shifts to Q8. In Q8, it is determined whether or not the flag is 1. If the determination in Q8 is YES, in Q9, the gear change characteristic for warm time shown in FIG. 6 is selected, and then in Q10, the gear stage gH is determined based on the gear change characteristic for warm time. Next, the selection of the shift characteristic for the cold state in Q11 and the determination of the gear stage gL based on the shift characteristic for the cold state in Q12 are performed.
[0029]
In Q13, it is determined whether or not the gear stage gH for the warm state and the gear stage gL for the cold state are the same. If the determination in Q13 is NO, in Q14, after the gear stage gL for the cold state is set to the final gear stage gF (execution of the final gear stage gF), the process returns to Q9. If the determination in Q13 is YES, the flag is reset to 0 in Q15, and then, in Q16, the warm speed gear gH is set to the final gear gF (execution of the final gear gF). If the determination in Q8 is NO, in Q17 and Q18, after the gear stage gH is determined based on the warm-time shift characteristics, the process proceeds to Q16.
[0030]
In FIG. 8, the processing of Q4 to Q7 corresponds to the operation of the prohibiting means in the claims. Further, the processes of Q9 to Q14 are processes corresponding to the shift characteristic switching delay means in the claims.
[0031]
Here, FIG. 4 shows a mode of occurrence of a shift shock when the operating oil pressure is reduced to shift from the first speed to the second speed at a low temperature. Will be quite large. FIG. 5 shows a shift shock when shifting from the first speed to the third speed without lowering the operating oil pressure (in a case where the operating oil pressure is increased as in the normal shift control) at a low temperature. This shows the manner of occurrence, and it is understood that shift shock is sufficiently prevented (reduced).
[0032]
Although the embodiments have been described above, the present invention is not limited to this, and includes, for example, the following cases.
(1) The sensor S3 as the temperature detecting means may be a sensor for directly detecting the temperature of the second brake 19 as a predetermined frictional engagement element, or an appropriate value relating to the temperature of the predetermined frictional engagement element. Can be detected.
[0033]
(2) The shift characteristic switching delay process in Q9 to Q14 may be performed only during a period from when the sensor S3 detects a temperature higher than the predetermined temperature to when a predetermined time elapses. Further, in place of the processing in Q9 to Q14, the shift control is continued based on the shift characteristic for a cold period until a predetermined time elapses after the temperature higher than the predetermined temperature is detected by the sensor S3. Thus, the shift control may be switched to the shift control based on the warm-time shift characteristic immediately after the elapse of the predetermined time.
[0034]
(3) It may be possible to set only the gear ratio during warm operation and not select the specific gear stage (second speed in the embodiment) during the cold period (the operation region in which the specific gear stage should be selected). At this time, for example, the gear position selected last time is kept).
[0035]
(4) The number of specific gears is not limited to one, but may be an automatic transmission having two or more gears (automatic transmissions have recently become more and more multi-gear). The present invention is suitable for application to a small number of automatic transmissions.
[0036]
(5) When setting the shift characteristic for the cold state, of the adjacent shift steps that are one step next to the specific shift step, as compared with the shift characteristic for the warm state, Only one of the region and the region of the lower gear may be expanded to the region of the specific gear. Of course, when an adjacent gear stage exists only on the low speed side or high speed side of a specific gear stage, the area of one existing adjacent gear stage may be expanded.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing an example of a multi-speed transmission gear mechanism having a band brake type frictional fastening element.
FIG. 2 is a diagram showing a relationship between an operation state of a friction engagement element and a shift speed in the transmission gear mechanism shown in FIG.
FIG. 3 is a diagram illustrating an example of a control system.
FIG. 4 is a diagram showing a shift shock generation mode when shifting from a first speed to a second speed at a low temperature.
FIG. 5 is a diagram showing a shift shock generation mode when shifting from a first speed to a third speed at a low temperature.
FIG. 6 is a diagram showing an example of a shift characteristic for a warm state.
FIG. 7 is a diagram showing an example of a shift characteristic for a cold state.
FIG. 8 is a flowchart showing a control example of the present invention.
[Description of sign]
2: Multi-stage transmission gear mechanism 19: Predetermined friction fastening element (band brake type)
U: Control unit S3: Temperature sensor (temperature detecting means)

Claims (8)

In an automatic transmission configured to obtain a specific gear by switching a power transmission path by engaging a predetermined friction engagement element of a band brake type,
Temperature detection means for detecting a value related to the temperature of the predetermined frictional engagement element,
Prohibition means for prohibiting a shift to the specific shift speed when it is determined from the detection result of the temperature detection means that the temperature of the friction engagement element is equal to or lower than a predetermined temperature;
A control device for an automatic transmission, comprising: In claim 1,
A control device for an automatic transmission, wherein the temperature detecting means is set to detect a temperature of hydraulic oil of the predetermined frictional engagement element. In claim 2,
In a state where the prohibiting means is operating, when the temperature detected by the temperature detecting means detects a temperature higher than the predetermined temperature, the operation of the prohibiting means is continued until a predetermined time has elapsed from the detection of the high temperature. A control device for an automatic transmission, comprising a switching delay means for continuing the switching. In claim 2,
The control device for an automatic transmission, wherein the prohibiting means is set to operate only when the engine load is lower than a predetermined load. In claim 2,
A shift characteristic for warm time set so as to be able to be taken by all shift speeds and a shift characteristic for cold time set so as to be able to take a shift stage other than the specific shift stage are preset.
A control device for an automatic transmission, wherein the prohibiting means is set to select the cold shift characteristic as a shift characteristic used for shift control. In claim 5,
In a state in which the prohibiting means is operated and the cold shift characteristic is selected, when a temperature higher than the predetermined temperature is detected by the temperature detecting means, based on the cold shift characteristic. A shift characteristic for switching a shift characteristic used for shift control to the warm shift characteristic when the determined shift stage and the shift stage determined based on the warm shift characteristic become the same shift stage. A control device for an automatic transmission, comprising switching delay means. In claim 6,
An automatic transmission, wherein the shift characteristic switching delay unit is set to operate only during a period from when the temperature detecting unit detects a temperature higher than the predetermined temperature to when a predetermined time elapses. Control device. In claim 5,
The automatic transmission includes, in addition to the specific gear, at least a low gear that is one gear lower than the specific gear and a high gear that is one gear higher than the specific gear. Be taken,
The low-speed gear shift characteristic is expanded to a high-speed side and the high-speed gear shift area is expanded to a low-speed side as compared with the warm shift characteristic. A control device for an automatic transmission.

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