Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2000-05-08
2002-04-02
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S473110, C074S473300
Reexamination Certificate
active
06363806
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a shift control method for a pneumatic shift system, and more particularly, to a shift control method for a pneumatic shift system in which a piston of a shift control device of the shift system is rapidly returned to a position effecting neutral shifting following driver manipulation of a gearshift lever to a neutral range from a drive range.
(b) Description of the Related Art
In trucks, buses and other such vehicles in which the engine is provided at the rear of the vehicle, because of the substantial distance between the transmission and the driver, a shift device is typically provided to convey clutch and gearshift lever operations to the transmission. A pneumatic shift system, rather than the conventional hydraulic or mechanical shift system, is being increasingly used to perform such a function. In the pneumatic shift system, air pressure is electronically controlled to change shift speeds and modes of the transmission.
FIG. 1
shows a schematic view of a typical pneumatic shift system to which the present invention is applied.
FIG. 2
shows a schematic view of a shift control device and related elements shown in FIG.
1
.
In the pneumatic shift system, a lever position sensor
6
detects driver manipulation of a gearshift lever
4
L. The lever position sensor
6
outputs electrical signals corresponding to the change in position of the gearshift lever
4
L to an electronic control unit (ECU
8
), after which the ECU
8
outputs signals to control a magnetic valve assembly
10
to open and closed states according to the signals received from the lever position sensor
6
. Accordingly, air is supplied to or exhausted from a shift control device
12
to control a transmission
14
into various forward and reverse shift speeds and modes.
The magnetic valve assembly
10
is connected to an air tank
15
and receives the supply of air from the air tank
15
. Also, by the supply and exhaust of air from and to the air tank
15
via a reaction valve
18
, which is a 3-way magnetic valve connected to a reaction cylinder (not shown), shift feeling is provided to the driver when the gearshift lever
4
L is manipulated to different shift modes.
The ECU
8
is connected to a shift mode display
20
, and the ECU
8
performs control such that the shift mode display
20
displays the present shift mode after receiving signals from the lever position sensor
6
. The ECU
8
is also connected to a warning lamp
24
which alerts the driver of either shift failure caused by the incorrect supply of air to the magnetic valve assembly
10
, or of the mis-operation of the gearshift lever
4
L by the driver. The ECU
8
detects such problems through its connection with a shift mode sensor
22
.
The shift control device
12
includes a first cylinder
26
and a second cylinder
28
. Air is supplied to and exhausted from the first cylinder
26
and the second cylinder
28
by the operation of the magnetic valve assembly
10
which operates according to signals output from the ECU
8
. The magnetic valve assembly
10
and the shift control device
12
are connected via air pipes
9
to enable such operation. A piston
30
is slidably disposed within the shift control device
12
. The piston
30
is displaced in a rightward or leftward direction (in the drawing) according to the supply of air to the first cylinder
26
and the second cylinder
28
.
A striker
32
is fixedly disposed on the piston
30
. Accordingly, when the piston
30
is displaced in the leftward direction, the striker
32
is also moved such that it operates the transmission
14
to either a first, third or fifth speed of a drive range; and when the piston
30
is displaced in the rightward direction, the striker is moved such that it operates the transmission
14
to either a second or fourth speed of the drive range, or into reverse. That is, when the driver operates the gearshift lever
4
L to different shift modes, the ECU
8
controls the magnetic valve assembly
10
so that air is supplied to or exhausted from the first cylinder
26
and the second cylinder
28
of the shift control device
12
, thereby controlling the displacement of the piston
30
and the striker
32
.
Accordingly, when the gearshift lever
4
L is shifted into one of the drive ranges from the neutral range, starting from a state of equilibrium, compressed air is exhausted from either the first or second cylinder
26
and
28
such that smooth shifting is realized. However, when the gearshift lever
4
L is shifted into the neutral range from one of the drive ranges, shifting is delayed by the operation of again obtaining a state of equilibrium by overcoming the force of compressed air acting in one direction.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a shift control method for a pneumatic shift system in which to effect shifting into neutral, compressed air is supplied to both cylinders of the pneumatic shift system following the rapid exhaust of compressed air from one of the two cylinders, thereby realizing rapid shifting into the neutral range.
To achieve the above object, the present invention provides a shift control method for a pneumatic shift system including the steps of determining if a gearshift lever is positioned in a neutral range after receiving gearshift lever position signals; controlling a first magnetic chamber of a magnetic valve assembly from ON to OFF for a predetermined time interval if the gearshift lever is in the neutral range; and controlling both the first magnetic chamber and a second magnetic chamber of the magnetic valve assembly to ON if the predetermined time interval has elapsed.
REFERENCES:
patent: 3939722 (1976-02-01), Stromberg
patent: 4269079 (1981-05-01), Fredell et al.
patent: 5433125 (1995-07-01), Muller
patent: 5797294 (1998-08-01), Bohner et al.
patent: 6170347 (2001-01-01), Kim
patent: 6196077 (2001-03-01), Lee
patent: 11326105 (2000-11-01), None
patent: 11343855 (2001-02-01), None
Christie Parker & Hale LLP
Ho Ha
Hyundai Motor Company
Marmor Charles A
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