JP2815596B2 - Slip control device for torque converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a slip control device for a torque converter having a lock-up clutch.

(Prior Art) Conventionally, a lock-up clutch capable of being fastened to the front cover is provided between the torque converter and the front cover, and three different power transmission characteristics can be obtained by selecting an operation state of the lock-up clutch. It is known to gain. That is, as shown in the shift map of FIG. 2, a lock-up control region located on the high vehicle speed side in the shift region, a slip control region located on the low vehicle speed / low load side, and a converter control region belonging to the other regions. One control area is set. In the lock-up control region, the lock-up clutch is in a completely engaged state, in the converter control state, the lock-up clutch is in a semi-engaged state, and in the slip control state, the lock-up clutch is in a released state. is there. An example of such a method for performing slip control with the lock-up clutch half-engaged in the slip control region is disclosed in, for example, JP-A-57-33253.

On the other hand, as a method of the slip control, there is a so-called slip control in which the rotation difference between the engine rotation speed and the turbine rotation speed is always kept constant, and a differential pressure between the fastening chamber and the release chamber of the torque converter (that is, There is a so-called constant differential pressure slip control that always keeps the lock-up clutch engagement force constant. In general, slip control with a constant rotation difference is performed in a region other than during a gear shift, and slip control with a constant differential pressure is performed during a gear shift.
This is because slip control with a constant differential pressure is performed during a gear shift because slip control with a constant rotational difference is difficult and stability is deteriorated because a large rotational difference displacement occurs during a gear shift. is there.

Note that the engagement force of the lock-up clutch is controlled by a duty solenoid valve (first
The slip ratio is controlled by adjusting the duty ratio of the engine speed and the turbine speed within a predetermined range during the slip control in which the rotation difference is constant. The feedback control is performed as described above, and the duty ratio is fixed to a predetermined value during the slip control in which the differential pressure is constant.

(Problems to be Solved by the Invention) Incidentally, as described above, the shift in the slip control region is performed by the slip control with a constant differential pressure. In this case, the duty ratio is fixed to a predetermined value and the engagement force of the lock-up clutch is changed. The conventional idea is that the gear shift shock is almost the same regardless of the gear shift state (ie, the gear shift position specified by the vehicle speed and the throttle opening) as long as the gear ratio is maintained constant. there were.

However, the inventors of the present application questioned such a conventional idea from the feeling of driving a real vehicle, and actually examined the degree of shift shock for each shift state. That is, as shown by arrows A, B, and C in FIG. 2, a 2 → 3 shift in the high throttle opening range (hereinafter, referred to as an A shift) and a 2 → 3 shift in the low slip control range.
The shift shock was examined for three shifts, ie, during a shift (hereinafter referred to as a B shift) and during a 3 → 4 shift (hereinafter referred to as a C shift) in a high throttle opening range. The gear shift shock is greater during the A shift than during the shift,
In addition, a result was obtained that the shift shock was larger during the A shift between the A shift and the C shift.

Thus, the present inventors have investigated the cause of the change in the shift shock depending on the shift state despite the shift in the slip control with the fixed duty ratio and the fixed differential pressure. As a result, the following facts were found. That is, the conventional idea is that when the duty ratio is fixed to a predetermined value as shown by a dotted line in FIG. 6, the engagement indoor pressure of the torque converter is constant regardless of a change in the engine speed. However, according to the experiments performed by the inventors of the present application, as shown by the solid line in the figure, even if the duty ratio is fixed to a predetermined value, the fastening chamber pressure gradually increases with an increase in the engine speed. Was found. It is considered that this is because both the hydraulic pressure in the fastening chamber and the hydraulic pressure in the release chamber of the torque converter rise due to the centrifugal force generated by the rotation of the torque converter. In this case, in the general torque converter, since the oil amount (that is, mass) in the engagement chamber is larger than the oil amount in the release chamber, the hydraulic pressure increase width in the engagement chamber is naturally larger than the oil pressure increase width in the release chamber. As a result, a pressure difference occurs between the two due to the effect of the centrifugal force. Therefore, even if the differential pressure is set by adjusting the duty ratio, the differential pressure is newly generated due to the centrifugal force. The engagement force of the clutch changes substantially gradually as the engine speed increases.

Therefore, the difference in the shift shock at each shift shown in FIG. 2 can be explained as follows. That is, between the A shift and the B shift, since the engine speed is higher and the engagement force of the lock-up clutch is higher during the A shift, the shift shock is greater in the A shift than in the B shift. Things. In both the A-shift and the C-shift, the shift speed is higher in the A-shift than in the B-shift because the engine speed is higher and the lock-up clutch engagement force is higher in the lower-speed A-shift. Is larger.

Accordingly, the present invention provides a slip control device for a torque converter capable of performing slip control with a constant differential pressure regardless of a change in the engine speed. In view of the above, it is an object of the present invention to provide a torque converter slip control device capable of reducing a shift shock in a slip control region as much as possible regardless of a shift state during shifting.

(Means for Solving the Problems) In the present invention, as a specific means for solving such problems, a lockup between a turbine coupled to a turbine shaft and a front cover coupled to an engine output shaft is provided. A clutch is interposed, hydraulic pressure supplied to both sides of the lock-up clutch is adjusted by hydraulic control means, and a fastening force between the lock-up clutch and the front cover can be adjusted by the set differential pressure. In the slip control device for a torque converter in which the set differential pressure adjusted by the hydraulic pressure control means is fixed and the slip control with the lock-up clutch half-engaged is performed, The set differential pressure, which is adjusted by the hydraulic control means at the time of control, is set at a high engine speed. It is characterized by comprising a correcting means for correcting so as to decrease the degree.

(Operation) In the present invention, with such a configuration, the differential pressure adjusted by the hydraulic pressure control means is corrected in a direction to decrease with an increase in the engine speed, whereby the change in the differential pressure due to the centrifugal force is reduced. The effects will be eliminated as much as possible.

(Effects of the Invention) Therefore, according to the slip control device for a torque converter of the present invention, the engagement force of the lock-up clutch in the specific operation region can be equalized as much as possible regardless of the change in the engine speed. Thus, by setting the differential pressure correction value appropriately, it is possible to obtain an effect that it is possible to reduce the shift shock particularly in the specific operation region as much as possible.

(Embodiment) Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. 1 to FIG.

FIG. 1 shows a torque converter provided with a slip control device according to an embodiment of the present invention. The torque converter 1 includes a pump 5 fixed to one side of a front cover 3 and a case 4 connected to an engine output shaft 2 and rotating integrally with the engine output shaft 2. A turbine 6 rotatably provided on the other side of the front cover 3 and the case 4 and rotatably driven by the rotation of the pump 5 via hydraulic oil, and interposed between the pump 5 and the turbine 6. It has a stator 7 that increases the torque when the speed ratio of the turbine rotation speed to the pump rotation speed is equal to or less than a predetermined value, and a lock-up clutch 8 interposed between the turbine 6 and the front cover 3.

The rotation of the turbine 6 is controlled by a turbine shaft 9.
And output to a transmission gear mechanism (not shown). The lock-up clutch 8 is connected to the turbine shaft 9, and when the lock-up clutch 8 is fastened to the front cover 3, the engine is connected via the front cover 3 and the lock-up clutch 8. The output shaft 2 and the turbine shaft 8 are directly connected.

In addition, a mainstream line 10 connected to an oil pump (not shown) connects the fastening chamber 27 of the torque converter 1 with an oil pump (not shown).
Hydraulic oil is introduced via the lock-up valve 11 and the converter line 12, and the pressure of the hydraulic oil in the engagement chamber 27 constantly urges the lock-up clutch 8 in the engagement direction. On the other hand, a lock-up release line 14 led from the lock-up valve 11 is connected to a release chamber 13 between the lock-up clutch 8 and the front cover 3. When hydraulic pressure (release pressure) is introduced into the release chamber 13, the lock-up clutch 8 is released.

Further, a converter outline 17 for sending hydraulic oil to an oil cooler 16 via a pressure holding valve 15 is connected to the torque converter 1.

On the other hand, the lock-up valve 11 has a spool 18 and
The spool 18 is provided with a spring 19 for urging the spool 18 rightward in the drawing, and on both sides of the port 20 to which the lock-up release line 14 is connected, a pressure regulating port 21 to which the mainstream line 10 is connected and a drain port 22 are provided.

A pilot line 23 for applying a pilot pressure to the spool 18 is connected to an end of the lock-up valve 11 on the right side in the drawing, and is provided between a tank 25 and a drain line 24 branched from the pilot line 23. Is provided with a duty solenoid valve 26.

This duty solenoid valve 26 is turned on and off at a predetermined duty ratio by a control signal,
The pilot pressure in the pilot line 23 is adjusted to a value corresponding to the above-mentioned duty ratio by opening and closing at a very short cycle.

This pilot pressure is applied to the spool 18 of the lock-up valve 11 in a direction opposite to the biasing force of the spring 19, and the spool 18 is released in lock-up in the same direction as the biasing force of the spring 19. The release pressure in line 14 is acting. The spool 18 moves due to the relationship between the hydraulic pressure and the urging force, and the lock-up release line 14 communicates with the mainstream line 10 (pressure regulating port 21) or the drain port 22. That is, the duty solenoid valve 26
Is controlled to a value corresponding to the duty ratio of.

Here, when the duty ratio (ON time ratio during one cycle of ON and OFF) is 0%, the amount of drain from the pilot line 23 is minimized, and the pilot pressure or the release pressure is maximized. Is completely released (OFF), and the converter control state is established. When the duty ratio is 100%, the drain amount is maximized, and the pilot pressure or the release pressure is minimized, so that the lock-up clutch 8 is completely engaged (ON).
Thus, a complete lock-up control state is established. further,
In the middle range of the duty ratio, the lock-up clutch 8 is set in the slip state, and the slip control state is established. In this region, the slip amount of the lock-up clutch 8 is controlled according to the duty ratio.

FIG. 2 shows a shift map having a shift pattern and a converter control pattern of an automatic transmission (not shown) including the torque converter 1 and a transmission gear mechanism connected to the turbine shaft 9 of the torque converter 1. . The shift pattern has an upshift line and a downshift line for each of the first to fourth speeds. On the other hand, the converter control pattern is set as follows. In other words, in the acceleration region, the acceleration slip control region corresponds to the low vehicle speed / low load region (corresponding to the specific operation region in the claims).
And a lock-up control region in a high vehicle speed region, and a converter control region in other regions.

Here, as the form of the slip control in the slip control region, there are the control for keeping the rotation difference constant and the control for keeping the differential pressure as described above. In this embodiment, the constant differential pressure is kept only at the time of shifting within this slip control region. Slip control is performed, and control for keeping the rotation difference constant is performed in other regions. The present invention is directed to slip control during shifting in this slip control region. That is, when upshifting or downshifting is performed in the slip control region, the set differential pressure set by the duty solenoid valve 26 (that is, the set fastening force of the torque converter 8) as described above influences the centrifugal force. In response to this change, the shift shock is prevented from changing depending on the magnitude of the engine speed. More specifically, the hydraulic pressure acting on both sides of the lock-up clutch 8 is corrected by correcting the set differential pressure so that the set differential pressure decreases as the engine speed increases (that is, as the hydraulic pressure rise due to centrifugal force increases). Is maintained constant irrespective of the change in the engine speed, and the substantial engagement force of the lock-up clutch 8 at the time of shifting is maintained constant regardless of the shifting state. Things.

Hereinafter, the actual slip control at the time of shifting will be described with reference to the flowchart shown in FIG.

After the control starts, first detects the engine rotational speed N _E and the turbine speed N _T and the vehicle speed V and the throttle opening degree, respectively (step S _1).

Next, the current control area is determined (step S ₂ ), and if it is the non-slip control area, the shift map (FIG. 4)
Performs normal control (i.e., the converter control or lock-up control) along (step S _9). On the other hand, in the case of the slip control region, it determines whether upshifting (Step S _3). Here, when it is determined that the vehicle is not shifting up, slip control with a constant rotation difference is performed.
That is, first obtains the engine rotational speed N _E and the rotational difference .DELTA.N from the turbine speed N _T (N _E -N _T) in step S _6, the rotational difference correction value of the duty ratio corresponding to this rotation difference .DELTA.N? DM
The determined from the rotational difference correction value map shown in FIG. 3 (step S _7).

In this embodiment, feedback control is performed so that the rotation difference ΔN falls within the range of 60 to 80 rpm. For example, when the rotation difference ΔN is larger than 80 rpm, the rotation difference correction value Δdm is set to a positive value. On the other hand, if it is smaller than 60 rpm, it is set to a negative value.

Then, the next duty ratio dm by adding the rotational difference correction value Δdm obtained in step S ₇ to the current duty ratio dm
The gain (step S _8).

On the other hand, a result of the determination in step S _3, if it is determined that the upshift, together with changing the differential pressure constant control from the rotational difference constant control the control mode is corrected in consideration of the engine rotational speed.

That is, in step S _4, the predetermined set duty ratio dmo (fixed value), the differential pressure value correction value α shown in FIG. 5 by adding, to calculate the duty ratio dm in the differential pressure constant slip control. Then, persisting the slip control in the duty rate dm to the shift end (step S _5), after the shift end is again shift to slip control of the rotational difference.

As described above, the slip control with a constant differential pressure is performed at the time of upshifting, and the duty ratio of the duty solenoid valve 26 for setting the differential pressure is appropriately corrected according to the engine speed, thereby controlling the engagement force of the lock-up clutch. The resulting pressure in the fastening chamber is brought as close as possible to the ideal characteristic shown by the broken line in FIG. As a result,
Regardless of the shift state in the slip control region, the shift shock is substantially the same, and the shift shock does not increase in a specific shift state as in the related art. Therefore, as in this embodiment, by setting the correction value α to α = 1 on the low rotational speed side of the engine, the shift shock during the shift in the slip control region can be minimized in any shift state. It is possible to reduce it.

[Brief description of the drawings]

FIG. 1 is a main part system diagram of a slip control device of a torque converter according to an embodiment of the present invention, FIG. 2 is a shift map diagram, FIG. 3 is a rotation difference correction value map of a duty ratio, and FIG.
FIG. 5 is a control flowchart, FIG. 5 is a duty value correction value map, and FIG. 6 is a change characteristic diagram of the engagement indoor pressure of the torque converter. DESCRIPTION OF SYMBOLS 1 ... Torque converter 2 ... Engine output shaft 3 ... Front cover 4 ... Case 5 ... Pump 6 ... Turbine 7 ... Stator 8 ... Lockup clutch 9 ... Turbine shaft 11 ... Lockup valve 13 …… Release chamber 26 …… Duty solenoid valve 27 …… Conclusion chamber

Claims (1)

(57) [Claims] 1. A lock-up clutch is interposed between a turbine connected to a turbine shaft and a front cover connected to an engine output shaft, and hydraulic pressure supplied to both sides of the lock-up clutch is controlled by hydraulic control means. The set differential pressure can be adjusted to adjust the fastening force between the lock-up clutch and the front cover, and in the specific operation region, the set differential pressure adjusted by the hydraulic control means is fixed at a fixed value to lock the lock-up clutch. A slip control device for a torque converter which performs a slip control with a clutch half-engaged, wherein the set differential pressure adjusted by the hydraulic control means during the slip control in the specific operation region is controlled by an engine speed. Characterized by comprising a correction means for correcting so as to decrease as the torque is higher. The slip control system.