Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1999-05-12
2000-04-18
Marmor, Charles A
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 46, B60K 4112
Patent
active
060509171
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for control of a CVT in which an electronic control unit detects and monitors the speed signals of a primary and a secondary disc.
The methodical operation of CVT is usually monitored by an electronic control unit. EP-PS 0228884 thus proposes to monitor the methodical operation of two speed sensors assigned to the primary and secondary taper disc pairs. Hereby is tested whether or not the speed signal is present. In the absence of speed of the secondary taper disc pair, it is proposed to adjust the reduction ratio to a fail-safe value. In the absence of the speed of the primary disc pair, it is proposed that the speed of the primary taper disc pair be adjusted to a fail-safe value.
The above described prior art has the disadvantage that brief failures are interpreted as an absence of the speed signal.
SUMMARY OF THE INVENTION
In view of the above, the invention is to solve the problem of providing for a CVT, a method which detects brief failures of the speeds of the primary and the secondary disc pairs and reacts thereto with adequate flexibility.
According to the invention, the problem is solved by the fact that in the presence of a stationary state while driving, a ratio of the variator is determined from the speed signals of the primary and secondary discs, the ratio is assigned to a first characteristic field, said characteristic field having one range of authorized ratios and ranges of unauthorized ratios. An error is detected when the ratio is in an unauthorized range and with detection of the error the pressure level of the variator is increased in a first step and if the error continues an emergency program is activated in a second step.
The solution, according to the invention, offers the advantage that by assigning the ratio to ranges of authorized and unauthorized ratio, not only is there tested the presence of speed signals per se, but also the correctness thereof in the stationary and dynamic ranges. If it is found that the ratio lingers in an unauthorized range, in adequate flexible reaction thereto the level of contact pressure of the variator is increased. In case the error continues, an emergency drive program is activated in a second step.
In a development of this, it is proposed that the range of authorized ratios has as upper limit the highest possible ratio of the variator and as lower limit the minimum possible ratio of the variator and, in development of this, it is proposed that the characteristic field has an additional range of stoppage, an error within this range existing when the number of revolutions of the primary disc is higher than the product of the number of revolutions of the secondary disc multiplied by the maximum possible ratio of the variator.
In a development, it is proposed that in the absence of error during a dynamic operation, an actual gradient of the ratio be determined from the ratio of the variator at a first and at a second moment. Thereafter, an operating point is determined from the actual gradient and the number of revolutions of the secondary disc at the second moment. This operating point is assigned to a second characteristic field, wherein the second characteristic field has a range of authorized and a range of unauthorized operating points. An error is detected when the operating point is in the range of unauthorized operating points wherein, with the detection of the error, in a first step the contact pressure level on the variator is increased and if the error continues, an emergency drive program is activated in a second step. This development offers the advantage that after it having been found, via the first characteristic field, that an operating point is in the authorized range, it is additionally tested, via the second characteristic field, whether the dynamics of adjustment of the variator coincide with predetermined values. In other words, by said additional function is tested whether slip occurs on the variator in the dynamic operation. In CVT of the taper disc continuously va
REFERENCES:
patent: 4698764 (1987-10-01), Inagaki et al.
patent: 5947862 (1999-09-01), Knapp et al.
patent: 5967918 (1999-10-01), Knapp et al.
Bacher Holger
Gierling Armin
Marmor Charles A
Waddell Tisha D.
ZF Friedrichshafen AG
LandOfFree
CVT control method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with CVT control method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CVT control method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2332582