JP3592176B2 - Control method of automatic transmission for vehicle - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of controlling an automatic transmission for a vehicle, and more particularly, to a method of reducing a shock when a shift lever is switched from a travel range to a travel range through a neutral range again, such as D → N → D, R → N → R. It is about.
[0002]
[Prior art]
Generally, in an automatic transmission for a vehicle, a predetermined engagement element is engaged or released by switching a shift lever to switch between a traveling range and a neutral range. The shift lever is mechanically connected to the manual valve, switches an oil passage of the manual valve, and supplies and discharges the original pressure to and from the engagement element.
[0003]
[Problems to be solved by the invention]
By the way, when the vehicle is stopped, the driver may operate the shift lever to switch from the travel range to the travel range again via the neutral range, such as D → N → D or R → N → R. In particular, when such an operation is performed quickly, there is a problem that a shock called a garage shock occurs.
[0004]
FIG. 11 shows the temporal changes of the hydraulic pressure of the engagement element, the turbine speed, and the output shaft torque when the shift lever is switched from N → D → N → D.
In the first N range, the turbine speed is maintained at approximately the same speed as the idle speed. However, when the turbine is switched to the D range and hydraulic pressure is supplied to the engagement element to start engagement, the turbine speed is reduced. The number of revolutions gradually decreases to almost 0 rpm (when the vehicle is at a standstill). At this time, a shift shock hardly occurs because the shock absorbing function of the torque converter works.
Next, when the range is switched to the N range again, the hydraulic pressure of the engagement element starts to be released, so that the turbine speed starts to increase. However, when the range is quickly switched from the N range to the D range, the supply time of the hydraulic pressure is started before the hydraulic pressure of the engagement element is sufficiently released because the holding time in the N range is short. As a result, the turbine speed drops sharply to 0 rpm, and the shock absorption function of the torque converter does not work, causing a shock.
Such a shock tends to occur particularly at low temperatures.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a control method of an automatic transmission for a vehicle, which can effectively reduce a shock when the shift lever is quickly switched from a travel range to a travel range again via a neutral range.
[0006]
[Means for Solving the Problems]
The above object is achieved by the present invention. In other words, the invention according to claim 1 is an automatic transmission for a vehicle in which a predetermined engagement element is engaged or released by switching a shift lever to switch between a traveling range and a neutral range. A step of detecting that the shift lever is switched from the traveling range to the traveling range again through the neutral range, a step of detecting an input rotation speed in the neutral range state at the time of the switching, and A step of delaying the supply of hydraulic pressure to the engagement elements engaged in the travel range until the number of rotations returns to or above the target rotation speed.
[0007]
For example, assuming a case where the shift lever is quickly switched from D to N to D, the hydraulic pressure of the engagement element is released with the switch from D to N, and the input rotation speed starts to increase. Subsequently, when the range is quickly switched from the N to the D range, the supply of the hydraulic pressure is started before the hydraulic pressure of the engagement element is sufficiently released, so that the input rotation speed drops rapidly to 0 rpm. Therefore, in the present invention, the supply of the hydraulic pressure to the engagement element is delayed until the input rotation speed in the N range returns to the target rotation speed or more. That is, even when the shift lever is switched to the D range, the engagement element is kept on standby without supplying hydraulic pressure. As a result, when the supply of the hydraulic pressure to the engagement element is started next time, the input rotation speed does not rapidly drop to 0 rpm, and the shock is improved.
If the target input speed at the time of starting the supply of the hydraulic pressure to the engagement element is set too high, the start of the engagement of the engagement element is delayed. It is preferable to set it near the minimum rotation speed at which the shock absorption function by this can work.
[0008]
The control method of the present invention is preferably applied to an electronically controlled automatic transmission using a solenoid valve. That is, when the shift lever is switched, the manual valve mechanically connected to the shift lever is also switched at the same time, and the line pressure is supplied to the hydraulic circuit of the engagement element via the manual valve. In the hydraulic circuit of the engaging element to be engaged, a control valve for controlling the hydraulic pressure of the engaging element is provided. As the control valve, an electromagnetic valve such as a linear solenoid valve or a duty control valve is used. In the present invention, the input rotation speed at the time of switching from D → N → D or R → N → R is electrically detected, and the solenoid valve is electronically controlled in accordance with the input rotation speed, so that the engagement element is controlled. The hydraulic pressure supply can be freely delayed. That is, the present invention can be implemented by using an existing electronically controlled automatic transmission and only partially changing the control program of the engagement element.
[0009]
By the way, the engagement element is provided with a piston for receiving the oil pressure to fasten the clutch plate and a return spring for returning and urging the piston. Even if the oil pressure is supplied to the piston, the engagement starts immediately. Not in translation. In other words, an invalid stroke occurs until the piston moves against the return spring under the oil pressure and comes into contact with the clutch plate, which causes a delay in engagement. In order to eliminate such an engagement delay, in the conventional automatic transmission, a high oil pressure (for example, a line pressure) is temporarily applied at the start of engagement of the engagement element to eliminate the invalid stroke in a short time. "Wrapping" is widely practiced. In the present invention, the term “backlash” is not limited to the case where the piston is moved as described above, but also includes a control of only filling the hydraulic circuit to the engagement element with oil, and the engagement delay is reduced. Any control can be used as long as it can be shortened a little. Even when the engagement element changes state from engagement to release to engagement as in D → N → D or R → N → R, backlash is performed. Even if the supply of hydraulic pressure to the engagement elements is delayed until the input rotation speed returns to or above the target rotation speed, the backlash reduces the input rotation speed, causing a shock. there is a possibility.
[0010]
Therefore, in the second aspect, as the holding time in the N range becomes shorter, the amount of backlash is reduced, or when the holding time in the N range is shorter than the set time, the backpacking is prohibited. In other words, when the holding time in the N range is short, the supply of the hydraulic pressure to the engagement element is delayed as in claim 1, and the amount of backlash is reduced as the holding time in the N range is shortened. Or, by prohibiting backlash, it is possible to achieve both elimination of the engagement delay and reduction of the shock at the time of re-engagement. Specific methods for reducing the amount of backlash include a method of shortening the backlash time and a method of lowering the backlash hydraulic pressure.
Further, in the case of the method of prohibiting backlash when the holding time in the N range is shorter than the set time, it is possible to achieve both the elimination of the engagement delay and the reduction of the shock at the time of re-engagement, and the control is improved. It has the advantage of being simple.
[0011]
The control method according to claim 2 may be performed only when the oil temperature of the automatic transmission is lower than the set temperature. That is, when the ATF oil temperature is low, the viscosity of the oil increases, and the fall of the hydraulic pressure becomes slow. Therefore, the relationship between the holding time of the N range and the engagement shock is different at the high temperature. Therefore, the control according to claim 2 may be performed only when the oil temperature is lower than the set temperature, and the control may be performed as usual when the oil temperature is higher than the set temperature.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a vehicle system equipped with an automatic transmission for a vehicle according to the present invention.
The output of the engine 1 is transmitted to a transmission mechanism 4 via a torque converter 3 of the automatic transmission 2, and the transmission mechanism 4 is connected to wheels (not shown) via an output shaft 5. The automatic transmission 2 includes an oil pump 6 driven by the engine 1 via a torque converter 3, and the discharge pressure of the oil pump 6 is sent to a hydraulic control device 7. The hydraulic control device 7 includes first to fourth solenoid valves 21 to 24. By controlling these solenoid valves 21 to 24 by the electronic control device 20, various types of engagement elements incorporated in the speed change mechanism 4 are controlled. The hydraulic pressure is controlled according to various signals according to the traveling state. Here, signals such as a shift position, an input rotation speed (turbine rotation speed), a vehicle speed, a throttle opening, and an ATF oil temperature are input to the electronic control device 20.
[0013]
FIG. 2 shows an example of the transmission mechanism 4.
The transmission mechanism 4 includes an input shaft 10 to which engine power is transmitted via a torque converter 3, three clutches C <b> 1 to C <b> 3 and two brakes B <b> 1 and B <b> 2 as engagement elements, a one-way clutch F, a Ravigneaux type planetary gear. A mechanism 11, a differential device 14, and the like are provided.
The forward sun gear 11a of the planetary gear mechanism 11 is connected to the input shaft 10 via a C1 clutch, and the forward sun gear 11a is also connected to the transmission case 16 via a B1 brake. The rear sun gear 11b is connected to the input shaft 10 via a C2 clutch. The carrier 11c is connected to the input shaft 10 via a center shaft 15 and a C3 clutch. The carrier 11c is connected to the transmission case 16 via a B2 brake and a one-way clutch F that allows only the forward rotation (engine rotation direction) of the carrier 11c. The carrier 11c supports two types of pinion gears 11d and 11e, the forward sun gear 11a meshes with a long pinion 11d having a long shaft length, and the rear sun gear 11b meshes with a long pinion 11d via a short pinion 11e having a short shaft length. . The ring gear 11f that meshes with only the long pinion 11d is connected to the output gear 12. The output gear 12 is connected to a differential 14 via an intermediate shaft 13.
[0014]
The transmission mechanism 4 achieves four forward speeds and one reverse speed as shown in FIG. 3 by operating the clutches C1, C2, C3, the brakes B1, B2, and the one-way clutch F. In FIG. 3, ● indicates the operating state of the hydraulic pressure. The B2 brake is engaged at the time of retreat and at the first speed of the L range. FIG. 3 also shows the operating states of the first to fourth solenoid valves 21 to 24. ○ indicates an energized state, X indicates a non-energized state, and △ indicates a temporary energized state. This operation table shows the operation in the steady state.
[0015]
The first solenoid valve 21 is for B1 brake control, the second solenoid valve 22 is for C2 clutch control, and the third solenoid valve 23 is for C3 clutch control and B2 brake control. Further, the fourth solenoid valve 24 is used for control during switching between the L range (first speed) and the R range. A duty control valve or a linear solenoid valve is used for the first to third solenoid valves 21 to 23 to perform delicate hydraulic control, and an ON / OFF switching valve is used for the fourth solenoid valve 24.
The hydraulic control device 7 may be provided with electromagnetic valves for lock-up control of the torque converter 3 and line pressure control in addition to the four electromagnetic valves 21 to 24 for shift control.
[0016]
FIG. 4 is a schematic diagram illustrating an example of a hydraulic circuit of the C2 clutch.
The manual valve 30 and the line pressure P _L is input at all times, by switching to the D position in conjunction with the manual valve 30 and the operation of the shift lever 31, the line pressure P _L is normally open second solenoid valve 22 To the C2 clutch.
In FIG. 4, x indicates a drain.
Although FIG. 4 shows an example in which the C2 clutch is controlled by the second solenoid valve 22 alone, a combination of the solenoid valve and a spool valve controlled by the signal pressure of the solenoid valve may be used, or another valve may be interposed. Of course, it may be possible.
[0017]
Next, an example of a control method according to the present invention is shown in FIG. FIG. 5 shows the supply current of the second solenoid valve and the C2 clutch pressure when the shift lever is switched from N → D → N → D, that is, when the state of the C2 clutch changes from release to engagement to release to engagement. , The change over time of the turbine speed and the output shaft torque.
In the first N range, since the oil supply passage from the manual valve 30 is drained, the C2 clutch is released, and the turbine speed is maintained at approximately the same as the idle speed. When the range is switched to the D range, hydraulic pressure is supplied from the manual valve 30 to the C2 clutch via the second solenoid valve 22, and the C2 clutch starts to be engaged. Therefore, the turbine rotation speed is almost 0 rpm (when the vehicle is in a stopped state). ). At this point, almost no shift shock occurs.
Here, when the range is switched to the N range again, the hydraulic pressure of the C2 clutch is released, so that the turbine rotational speed starts to increase. However, when the range is quickly switched from the N range to the D range, the turbine rotational speed drops rapidly to 0 rpm, causing a shock. May occur. However, according to the present invention, even if the shift lever is switched from the N range to the D range, the second solenoid valve 22 is maintained in the ON (drain) state until the turbine speed reaches the target speed N ₀ , and the C2 clutch is switched. Delay or wait for hydraulic supply. The target rotation speed N ₀ is set to a rotation speed N ₀ higher than the turbine rotation speed that decreases instantaneously when hydraulic pressure is supplied to the C2 clutch. Therefore, when the hydraulic pressure supply to the C2 clutch is started next time, the turbine speed does not drop rapidly to 0 rpm, and the torque converter can absorb the shock, so that the shift shock can be improved.
After switching to the N → D, the delay period _{T 0} until the turbine speed reaches the target rotational speed _{N 0,} depending on the ATF temperature and the clutch capacity is about 100 msec. In the meantime, the turbine speed increases by several hundreds or more, so that the shock at the time of re-engaging the C2 clutch can be eliminated.
[0018]
FIG. 6 shows a control method of the present invention when the shift lever is switched from D → N → D or R → N → R.
When starting, first, it is determined whether or not the shift lever has been switched from D → N → D or R → N → R (step S1). When the switch detects the turbine speed Nt at the N-range immediately before switching to D or R range (step S2), and compares this turbine speed Nt and the target rotational speed N ₀ (step S3). By the time of Nt _{<N 0,} the process returns to step S3, waits for the turbine speed Nt increases. That is, the state of the N range is maintained even after the shift lever is switched to the D range or the R range. When Nt ≧ N ₀ , hydraulic pressure supply to the engagement elements (C2 clutch in the case of D → N → D, B2 brake in the case of R → N → R) is started, and shifts to the D range or the R range. Transition. Specifically, the electronic control unit 20 starts controlling the supply current to the second solenoid valve 22 or the third solenoid valve 23, thereby gradually engaging the C2 clutch or the B2 brake.
[0019]
5 and 6, an example in which no backlash is performed when the C2 clutch is engaged is described. Next, an example in which backlash is performed will be described with reference to FIG.
Here, a method of shortening the backlash time as the holding time (disengagement time of the C2 clutch) of the N range becomes shorter will be described.
FIG. 7 shows a change in the supply current to the C2 clutch control solenoid valve 22 when the shift lever is switched from N → D → N → D. Here, a normally-open valve whose output oil pressure is turned on when the current is off is used as the solenoid valve, but in the case of a normally-closed valve, ON and OFF are reversed.
At the time of the first switching from N to D, since the holding time of the N range before that is long, even if the backpacking is performed with the normal backpacking time Ta, almost no shock occurs, and the clutch engagement delay occurs. Can be effectively eliminated.
On the other hand, when switching to the second N → D, while the turbine speed as in FIG 5 rises to the target rotational speed N _0, for delaying the supply of hydraulic pressure to the C2 clutch, providing the waiting time T _0. However, since the turbine speed also be provided a waiting time T ₀ has not increased to the idling rotational speed of the normal, there is a possibility that shock is generated when providing a gap filling time Ta as usual. Therefore, when the holding time Tn of the N range is short, the amount of backlash is reduced by shortening the backlash time Tb as compared with the normal time.
As a result, the amount of backlash during the second switching from N to D is reduced, and the turbine speed is not significantly reduced, so that a shock can be avoided.
[0020]
FIG. 8 shows the relationship between the holding time Tn of the N range and the loosening time Tc.
In FIG. 8A, the setting of the play time Tc is set to increase almost proportionally with the increase of the holding time Tn. When the predetermined holding time Tno is exceeded, the backlash time Tc becomes the reference time Tco and becomes constant.
The solid line in FIG. 8A is a case where the holding time Tn and the stuffing time Tc are in a proportional relationship. As shown in (b), when the time is equal to or shorter than the predetermined holding time Tno, the backpacking time Tc may be set to 0, that is, the backpacking may be prohibited. If rattling is prohibited, the change in turbine speed at that time is as shown in FIG.
As described above, by varying the loosening time Tc according to the holding time Tn, it is possible to prevent the delay of the engagement of the engagement element and eliminate the shock.
[0021]
FIG. 9 shows another embodiment of the rattling control, that is, a method of lowering the rattling oil pressure (current value) as the holding time of the N range becomes shorter.
Also in this case, similarly to FIG. 7, a change in the supply current to the C2 clutch control solenoid valve (normally open type) 22 when the shift lever is switched from N to D to N to D is shown.
At the time of the first switching from N to D, since the holding time of the N range before that is long, almost no shock is generated even if the backlash is performed with the normal backlash hydraulic pressure Pa, and the clutch engagement delay occurs. Can be effectively eliminated.
During the second switching from N to D, the holding time Tn in the N range is short, so that the supply of the hydraulic pressure to the C2 clutch is delayed while the turbine speed increases to the target speed N ₀ (time T ₀ ). . When the supply of the hydraulic pressure to the C2 clutch is started, the amount of backlash is reduced by lowering the backlash hydraulic pressure Pb from a normal state.
As a result, the amount of backlash during the second switching from N to D is reduced, and the turbine speed is not significantly reduced, so that a shock can be avoided.
[0022]
FIG. 10 shows the relationship between the holding time Tn and the loosening oil pressure Pc.
In (a) of FIG. 10, the setting hydraulic pressure Pc is set to increase almost proportionally with the increase of the holding time Tn. When the predetermined holding time Tno is exceeded, the backlash hydraulic pressure Pc becomes the reference pressure Pco and becomes constant.
Note that the solid line in FIG. 10A is a case where the holding time Tn and the loosening oil pressure Pc are in a proportional relationship, but the solid line may be set in a step-like manner as shown by a broken line, and furthermore, FIG. As shown in (b), the backlash hydraulic pressure Pc may be set to 0, that is, the backlash is prohibited during the predetermined holding time Tno or less.
[0023]
The present invention is not limited to the above embodiment.
In the above embodiment, an automatic transmission having three clutches C1 to C3 and two brakes B1 and B2 has been described. However, the present invention is not limited to this, and is applicable to an automatic transmission having various engagement elements. It is.
Further, the control method of the present invention is effective not only for switching D → N → D and R → N → R, but also for switching R → P → R and the like, and further for switching D → N → R → N → D. As described above, the present invention is effective even in a case where another travel range exists between the N ranges.
[0024]
In the above-described embodiment, an example in which only one of the loosening time Tc or the loosening oil pressure (current) Pc is changed based on the holding time Tn of the N range, but both may be changed simultaneously. That is, as the holding time Tn becomes shorter, both the backlash time Tc and the backlash hydraulic pressure Pc may be set shorter (smaller).
[0025]
In the above embodiment, the backlash time or the backlash oil pressure is set based on the holding time of the N range, but may be set in consideration of the oil temperature condition. That is, when the ATF oil temperature is low, the fall of the oil pressure is slow, and the relationship between the holding time and the engagement shock is different between high temperature and high temperature. Therefore, only when the oil temperature is lower than the set temperature, the holding time becomes shorter as the holding time becomes shorter. If the oil volume is set to a small value or the holding time is shorter than the set time, rattling is prohibited, and if the oil temperature is higher than the set temperature, the rattling control is performed as usual (the rattling time and the rattling hydraulic pressure). May be fixed).
[0026]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the present invention, when the shift lever is switched from the travel range to the travel range again through the neutral range, the input rotation speed in the neutral range state becomes equal to the target rotation speed. Since the supply of the hydraulic pressure to the engagement elements engaged in the travel range is controlled to be delayed until the number of rotations returns to a value equal to or more than the number, the input rotation speed does not drop rapidly and shift shock can be reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram in which an automatic transmission for a vehicle according to the present invention is mounted.
FIG. 2 is a skeleton diagram of a transmission mechanism of the automatic transmission of FIG.
FIG. 3 is an operation table of each engagement element and a solenoid valve of the transmission mechanism shown in FIG. 2;
FIG. 4 is a schematic diagram of an example of a hydraulic circuit of a C2 clutch.
FIG. 5 is a time change diagram of a C2 clutch pressure, a turbine speed, and an output shaft torque according to the present invention.
FIG. 6 is a flowchart of an example of a control method according to the present invention.
FIG. 7 is a time change diagram of a current supplied to a solenoid valve of an example in which the play control is used in combination with the present invention.
FIG. 8 is a diagram showing a relationship between a play time and a holding time in FIG. 7;
FIG. 9 is a time change diagram of a current supplied to a solenoid valve in another example in which play control is also used in the present invention.
FIG. 10 is a diagram showing the relationship between the backlash hydraulic pressure and the holding time in FIG. 9;
FIG. 11 is a time change diagram of a hydraulic pressure, a turbine rotation speed, and an output shaft torque of a conventional engagement element.
[Explanation of symbols]
C2 clutch (engagement element)
B2 Brake (engagement element)
20 Electronic control unit 22, 23 Solenoid valve

Claims (2)

In a vehicular automatic transmission in which a predetermined engagement element is engaged or released by switching a shift lever to enable switching between a traveling range and a neutral range,
A step of detecting that the shift lever has been switched from the traveling range to the traveling range again through the neutral range,
Detecting the input rotation speed in the neutral range state at the time of the switching, and until the detected input rotation speed returns to the target rotation speed or more, the hydraulic pressure applied to the engagement element engaged in the traveling range. Controlling the automatic transmission for a vehicle, comprising a step of delaying the supply. Including a step of temporarily supplying high oil pressure at the start of the supply of hydraulic pressure to the engagement element to perform backlash, and as the holding time in the neutral range becomes shorter, the backlash amount is reduced, or 2. The control method for an automatic transmission for a vehicle according to claim 1, wherein when the holding time in the neutral range is shorter than the set time, rattling is prohibited.

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