Disclosure of Invention
According to one aspect of the present invention, an automatic transmission clutch control method is provided for controlling a clutch to a linkage point. The automatic transmission clutch control method includes:
pre-charging oil: pre-charging the clutch according to the pre-charging oil pressure value;
and a second oil filling step: for the clutch which is pre-filled with oil, filling oil for the second time to the clutch so that the clutch reaches the linkage point state;
in the second oil filling process, the clutch pressure is used as a control quantity, so that the clutch pressure is increased by a fixed clutch pressure increase value; or, the clutch is filled with oil for a fixed time by taking the oil filling time of the clutch as a control quantity. Preferably, the pre-charge oil pressure value is adjustable.
The method can further comprise an adjusting step of adjusting the pre-filling pressure value to obtain the pre-filling pressure value corresponding to the current use condition of the clutch.
Specifically, the adjusting step includes:
step a: controlling a clutch to pre-charge oil according to the current pre-charge oil pressure value;
step b: controlling the clutch to carry out secondary oil filling according to the fixed time length, and obtaining an engine output torque increment value in the secondary oil filling process;
step c: judging whether the difference between the output torque increment value of the engine and a preset torque increment calibration value is within a preset error range or not; if yes, ending the adjusting step; if not, performing the step d;
step d: and changing the pre-charging pressure value, taking the changed pre-charging pressure value as the current pre-charging pressure value, and repeating the steps a to c.
Wherein, in step d:
when the output torque increment value of the engine is smaller than the torque increment calibration value, increasing the pre-charge pressure value by a preset step value so as to change the pre-charge pressure value; or,
and when the output torque increment value of the engine is greater than the torque increment calibration value, reducing the pre-oil charge pressure value by a preset step value so as to change the pre-oil charge pressure value.
In particular, the preset step value is 0.1 bar.
Specifically, the preset error range is ± 10%.
Preferably, the adjusting step is performed each time the transmission control unit of the vehicle is powered on.
In accordance with another aspect of the present invention, an automatic transmission clutch control method is provided for adjusting a pre-charge pressure value of a clutch to accommodate current clutch usage conditions. The method comprises the following steps:
step a: controlling the clutch to pre-charge oil according to the current pre-charge oil pressure value of the clutch;
step b: controlling the clutch to carry out secondary oil filling according to a preset fixed oil filling duration, and obtaining an engine output torque increment value in the secondary oil filling process;
step c: judging whether the difference between the output torque increment value of the engine and a preset torque increment calibration value is within a preset error range or not; if so, keeping the current pre-filling oil pressure value; if not, performing the step d;
step d: and changing the pre-charging pressure value, taking the changed pre-charging pressure value as the current pre-charging pressure value, and repeating the steps a to c.
Wherein, in step d:
when the output torque increment value of the engine is smaller than the torque increment calibration value, increasing the pre-charge pressure value by a preset step value so as to change the pre-charge pressure value; or,
and when the output torque increment value of the engine is greater than the torque increment calibration value, reducing the pre-oil charge pressure value by a preset step value so as to change the pre-oil charge pressure value.
In particular, the preset step value is 0.1 bar.
Specifically, the preset error range is ± 10%.
Preferably, the method is performed each time a transmission control unit of the vehicle is powered up.
The automatic transmission clutch control method is particularly suitable for controlling a DCT transmission clutch.
The clutch is controlled to quickly reach the linkage point by controlling the pressure of the clutch or the oil charging time of the clutch, so that the vehicle can be quickly started, and the wear of the clutch can be greatly reduced for the automatic transmission without the clutch position sensor, thereby reducing unnecessary oil consumption. In addition, the pre-charging oil pressure of the clutch is automatically adjusted according to the actual wear condition of the clutch, so that the clutch can reach a linkage point according to a preset control step, and the acceleration of the aging speed of the clutch caused by the wear of the clutch is reduced.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
In the working process of the vehicle clutch, the clutch finishes the three-time oil charging process: the clutch is pre-filled with oil, so that a control oil path of the clutch is filled with oil when the clutch is in a pre-filled state, and the driving part and the driven part are not in contact; the second time of oil filling, so that the clutch reaches a linkage point state from a pre-oil filling state; after the brake is released, the clutch is charged for the third time, so that the clutch finishes the engagement process and starts to transmit the torque of the engine. In the invention, the clutch is required to be controlled from an unlinked state to a linked point, so that the pre-charging pressure value and the secondary charging pressure value of the clutch are required to be controlled.
In the case of a clutch that is not worn, the following parameter acquisition and calibration operations can be performed first, which can be performed, for example, before the vehicle leaves the factory. The unworn clutch pre-charge pressure value P1 can be calibrated first, so that the control oil path of the clutch is filled with oil when the clutch is in a pre-charge state, the driving part and the driven part are not in contact, the output torque of the engine is unchanged for keeping the idling operation, and the output torque of the engine at the moment is recorded as T1. The clutch is then filled a second time to the point of linkage. In the process of filling oil for the second time to the clutch, along with the increasing of the pressure value of the clutch, the driving part and the driven part of the clutch start to contact to generate sliding friction, and the output torque of the engine can be correspondingly increased for keeping idle running. The elapsed time T for the process, the clutch pressure value P2 at which the clutch reaches the linkage point, and the engine second output torque value T2 are recorded, such that the clutch pressure increase DeltaP = P2-P1, the rate of change of clutch pressure GradP = (P2-P1)/T, and the engine output torque increase calibration DeltaT = T2-T1 are calibrated when the clutch reaches the linkage point from the pre-charge state.
In fact, the engine output torque increase calibration value DeltaT when the clutch reaches the linkage point position from the non-linkage state can be regarded as a fixed value, so whether the clutch reaches the linkage point position can be judged according to the engine output torque increase calibration value DeltaT.
For the clutch oil filling process, too fast clutch pressure change may cause engine stall, and too slow clutch pressure change may cause clutch slip friction to be severe, so in the actual design of the vehicle, the clutch pressure change rate GradP is usually set to a calibrated fixed value to avoid the above problems. The rate of change of clutch pressure, GradP = DeltaP/t, may thus be considered a substantially constant amount, such that the desired clutch pressure increase, DeltaP = GradP t, may be achieved by controlling the length of time, t, that takes for the second fill, to achieve the desired clutch pressure value, P2= P1+ DeltaP.
And recording the pre-charging pressure value P1 of the clutch and the time consuming for the second charging t by the transmission control unit, so that when the clutch is controlled to reach the linkage point state from the non-linkage state, firstly controlling the clutch to complete pre-charging by the pre-charging pressure value P1, and then controlling the clutch to perform the second charging for the time t by the clutch pressure change rate GradP, so that the clutch can reach the linkage point. Of course, in another embodiment, the transmission control unit may also directly record the clutch pressure increase DeltaP and control the clutch pressure to P2= P1+ DeltaP during the second fill, i.e. the clutch may be brought to the linkage point.
After the clutch is worn in the using process, the clutch pressure value P2 required by the clutch to reach the linkage point state changes. The inventor of the present application has found through research that, although the clutch pressure value P2 may vary, the effect of clutch wear or other factors on the clutch pressure is actually mainly reflected in the pre-charge pressure value P1. That is, if a new appropriate pre-fill pressure value P1 can be accurately determined as the clutch wears, the clutch can be brought to the linkage point state after the clutch pre-fill is completed, during the second fill, as long as the clutch pressure value is increased by DeltaP.
FIG. 1 is a graph illustrating pressure changes from an unengaged state to a linkage point for an unworn automatic transmission clutch. Pre-filling oil to the clutch from-0.5 s to 0s in the graph 1, so that the control oil circuit of the clutch is filled with the oil at 0 s; the clutch is then filled a second time from 0s to 0.5s (i.e., the second fill time period t described above) to the point of linkage. As can be seen from fig. 1, since the pre-charge pressure is appropriate, the output torque of the engine increases with the increase of the pressure value of the clutch at the beginning of the second charge. As shown in fig. 1, the engine output torque value at the time of completion of the pre-oil charge was 2Nm, the engine output torque value after completion of the second oil charge was 10Nm, and the increase in the engine output torque during the second oil charge was 8 Nm. When the clutch is in a linkage point state, the driving part and the driven part of the clutch can be quickly jointed after the brake is released, so that the vehicle can be quickly started.
As the number of times of using the clutch increases, the clutch is worn, which results in a change in the position of the clutch linkage point, and after the clutch is pre-filled with oil at the pre-filling pressure value P1, the control oil path of the clutch may not be filled with oil, or may already be filled with oil and the driving part and the driven part may already come into contact with each other, which results in that after the clutch is filled with oil for the second time in the time period t (i.e., from 0s to 0.5s in fig. 2 and 3), the clutch may not reach the linkage point position as shown in fig. 2, or may already have passed the linkage point position as shown in fig. 3. Thus, after each power-up of the transmission control unit, the pre-fill pressure value P1 of the clutch is adjusted to be able to adapt to the current usage situation of the clutch by performing the following adjustment steps:
step a, controlling a clutch to pre-charge oil according to the current pre-charge oil pressure value P1 of the clutch;
b, controlling the clutch to perform second oil filling according to the time length t to obtain an engine output torque increment DeltaT2 in the second oil filling process;
step c, comparing whether DeltaT2 is equal to a preset engine output torque increase calibration value DeltaT or not, and ending the adjusting step if the DeltaT2 is equal to the preset engine output torque increase calibration value DeltaT or the error is within a preset error range; otherwise, changing the pre-filling oil pressure value P1; specifically, the sizes of DeltaT2 and DeltaT are judged, and if DeltaT2< DeltaT, the step d is continued; if DeltaT2> DeltaT, continuing to step e;
d, increasing the pre-filling oil pressure value P1 by a preset step value to serve as a new pre-filling oil pressure value P1, and repeating the steps a to c;
and e, reducing the pre-filling oil pressure value P1 by a preset step value to serve as a new pre-filling oil pressure value P1, and then repeating the steps a to c.
Wherein the preset step value may be 0.1 bar. The preset error range is +/-10%. Of course, the preset step value and the preset error range can be other values to adapt to different adjustment precisions.
Taking fig. 1 to 3 as an example, if the engine output torque increase calibration value DeltaT =8Nm is preset, the engine output torque increase value shown in fig. 1 is equal to DeltaT, and the pre-charge pressure value P1 does not need to be adjusted. The increase in engine output torque shown in fig. 2 is less than 8Nm and it is necessary to increase the pre-charge pressure value P1 to allow the clutch to reach the linkage point after a second charge of fuel for a fixed period of time t, so that the clutch can be quickly engaged after the brake is released, reducing engine idle time. The increase in engine output torque shown in fig. 3 is greater than 8Nm, and the pre-charge pressure P1 needs to be reduced to avoid excessive engine output torque due to excessive clutch engagement, wasting energy, and further exacerbating clutch wear.
The adjusted pre-charging pressure value P1 of the clutch is recorded by the transmission control unit, and the pre-charging of the clutch is completed by controlling the clutch according to the adjusted pre-charging pressure value P1, so that the control oil circuit of the clutch is just fully filled with oil after the pre-charging is completed, and the clutch can be controlled to reach the position of a linkage point. The wear state of the clutch in the running process of the vehicle is unpredictable, so that the clutch can not adapt to various states by the preset pre-charging pressure value, the pre-charging pressure value of the clutch can be adjusted at any time according to the adjusting step to obtain the pre-charging pressure value of the clutch suitable for the current state, and the wear is reduced to prolong the service life of the clutch.
It should be appreciated that the method of adjusting the clutch pre-charge pressure value P1 described above is not only applicable to the automatic transmission clutch control method of the present invention, but may also be applicable to adjusting the clutch pre-charge pressure value in other clutch control methods.
The above examples are only for illustrating the technical solutions of the present invention, and are not intended to limit the scope of the present invention. Modifications and equivalents may be made thereto by those skilled in the art without departing from the spirit and scope of the present invention.