Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2000-03-02
2001-06-26
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S339000, C074S360000, C477S908000
Reexamination Certificate
active
06250172
ABSTRACT:
The present invention relates to a gear change for a commercial vehicle.
BACKGROUND OF THE INVENTION
It is known that commercial vehicles are provided with a gear change with a high number of gear ratios, for example eight, twelve or sixteen forward gear ratios and one or more reverse gear ratios.
The known gear changes generally comprise two or three groups or stages arranged in cascade with one another and each defining a reduced number (from two to four) of transmission ratios; therefore, the total number of gear ratios of the gear change is defined by the product of the transmission ratios of the individual stages.
A typical configuration is one comprising a main group or “main box” with four ratios plus reverse and at least one auxiliary group or “range” disposed downstream of the main stage and defining two transmission ratios for a total of eight gear ratios. The transmission ratios of the auxiliary group are calculated so as to define, in combination with the transmission ratios of the main group, two sets of gear ratios (I,II,III,IV; V,VII,VIII) which are separate and adjacent one another.
The selection and engagement of the gear ratios are controlled by a manually operated lever, the control grid of which (i.e. the entirety of the paths along which the lever has to be moved to select and disengage the various gear ratios) becomes increasingly complex as the number of gear ratios increases.
Referring to the example illustrated above (eight forward gear ratios), the grid may be of the so-called “double H” type; the gear ratios are disposed in pairs (I and II; III and IV; etc.) in respective engagement planes which can be selected by moving the lever along a selection plane (generally transversal with respect to the direction of travel of the vehicle); the gear ratios associated with the selected engagement plane can be engaged by subsequently moving the lever along the engagement plane forwards (odd gear ratios) or rearwards (even gear ratios) with respect to the selection plane.
Since the overall dimensions of the grid are limited for ergonomic and space reasons, as the number of gear ratios increases inevitable the distance between the various engagement planes decreases; in operation, this may give rise to the possibility of selection errors in the engagement plane, resulting in the engagement of incorrect gear ratios.
With the aim of resolving this problem selector levers with a “repeated H” grid have been proposed; in this case the grid is a simple H but the lever is provided with a selector which can move vertically making it possible to “split” the grid itself into two superimposed planes, to each of which corresponds a respective transmission ratio of the auxiliary group. The selection of the transmission ratios of the main group takes place in each of the two planes, said selection being easy and reliable since the distance between the planes of engagement is greater than in the case of a corresponding double H grid.
However, this arrangement also has drawbacks since it is possible for the driver to move the selector inadvertently into the upper level or lower lever, or vice versa, when changing gear, which in some cases may have serious consequences both for driving safety and for the mechanical integrity of the power plant. For example, when changing gear so as to “drop down” from the eighth gear ratio an error of this type could result in the engagement of third gear instead of seventh gear, of second gear instead of sixth gear, with the obvious risks of causing the engine to run at a speed of rotation greatly exceeding the limits of mechanical strength.
To resolve this problem electronic control systems have been proposed, which at the input receive a plurality of signals relating to the operating parameters of the gear change (speed of rotation of the input and output shafts, gear ratio engaged, gear ratio selected, etc.), and which process said input signals so as to enable or prevent the operation of the selector on the basis of stored maps. However, such systems entail both the use of a complicated and costly control unit and the installation of additional components for the gear change (mechanical locking elements, sensors and associated wiring).
Moreover, systems of the above-mentioned type are not always reliable and may not intervene at the right time in the case of particularly rapid maneuvers.
SUMMARY OF THE INVENTION
The object of the present invention is to devise a gear change which makes it possible to eliminate the drawbacks associated with the above-mentioned known gear changes.
The above object is achieved by the present invention in that it relates to a gear change for a commercial vehicle of the type comprising:
an input shaft;
an output shaft;
a gear-type transmission interposed between said input shaft and said output shaft and comprising at least one main group defining a plurality of main transmission ratios and an auxiliary group with two auxiliary transmission ratios defining respective pluralities of gear ratios of said gear change in combination with the main transmission ratios, said auxiliary group comprising a coupling member which can move between a first coupling position, in which a first auxiliary transmission ratio is activated, and a second coupling position, in which a second auxiliary transmission ratio is activated;
an actuator for controlling said movable coupling member, and
a control unit adapted to generate control signals for said actuator in response to a plurality of input signals which are representative of operating parameters of said gear change and of the position of manual selector means associated with said gear change,
characterised in that said actuator is adapted to adopt three stable positions which correspond, respectively, to said first position, to said second position and to a third neutral position of said movable coupling member, which is intermediate with respect to said first and second positions, in which said input shaft and said output shaft are uncoupled from one another; said control unit comprising means for comparing the speed of rotation of said input shaft following the engagement of a new gear ratio with a predetermined range of acceptable values, and means for generating control signs to arrange said actuator in said third position in the event that said speed is outside said predetermined range of acceptable values.
REFERENCES:
patent: 4676115 (1987-06-01), Morscheck et al.
patent: 5050079 (1991-09-01), Steeby
patent: 5054591 (1991-10-01), Braun
patent: 5315514 (1994-05-01), Steeby et al.
patent: 5416698 (1995-05-01), Hutchinson
patent: 5429005 (1995-07-01), Fukui et al.
patent: 5436833 (1995-07-01), Janecke
patent: 5511437 (1996-04-01), Braun
patent: 5974906 (1999-11-01), Stine et al.
patent: 6044721 (2000-04-01), Genise
patent: 0 737 828 (1996-10-01), None
Caramagno Augusto
Pigozzi Gian Maria
Ho Ha
Iveco Fiat S.p.A.
Kenyon & Kenyon
Marmor Charles A
LandOfFree
Gear change for a commercial vehicle does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gear change for a commercial vehicle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gear change for a commercial vehicle will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2470210