U.S. patent application number 09/920585 was filed with the patent office on 2002-03-14 for device for controlling the flow rate of hydraulic fluid in a supply line for vehicles.
This patent application is currently assigned to Firma Carl Freudenberg. Invention is credited to Brandenburger, Walter.
Application Number | 20020030330 09/920585 |
Document ID | / |
Family ID | 7661019 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020030330 |
Kind Code |
A1 |
Brandenburger, Walter |
March 14, 2002 |
DEVICE FOR CONTROLLING THE FLOW RATE OF HYDRAULIC FLUID IN A SUPPLY
LINE FOR VEHICLES
Abstract
A device for controlling the flow rate of hydraulic fluid in a
supply line for the cylinder chambers of suspension cylinders in
vehicles, especially tractors, having a permanent suspension axle,
whose height is regulated by a level control device, a choke being
inserted into the supply line for limiting the flow rate of the
hydraulic fluid, the supply line (2) being furnished with a bypass
line (15) circumventing the choke (4), an auxiliary choke (16),
controlled by a control unit (17) having level sensors, being
inserted into the bypass line, the auxiliary choke being switched
on in response to pronounced static load change when the limit
stops of the vehicle axle are reached, permitting a larger flow
rate of the hydraulic fluid.
Inventors: |
Brandenburger, Walter;
(Neuss, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Assignee: |
Firma Carl Freudenberg
|
Family ID: |
7661019 |
Appl. No.: |
09/920585 |
Filed: |
August 1, 2001 |
Current U.S.
Class: |
280/5.503 |
Current CPC
Class: |
B60G 2300/026 20130101;
B60G 7/04 20130101; B60G 17/04 20130101 |
Class at
Publication: |
280/5.503 |
International
Class: |
B60G 017/01 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2000 |
DE |
P 10052888.0 |
Claims
What is claimed is:
1. A device for controlling the flow rate of hydraulic fluid in a
supply line for a cylinder chamber of a suspension cylinder in a
vehicle having a permanent suspension axle, whose height is
regulated by a level control device, comprising: a choke inserted
into the supply line (2) for limiting the flow rate of the
hydraulic fluid, the supply line (2) being furnished with a bypass
line (15) circumventing the choke (4); and an auxiliary choke (16),
controlled by a control unit (17) having level sensors, inserted
into the bypass line, the auxiliary choke being switched on in
response to pronounced static load change when the limit stops of
the vehicle axle are reached, permitting a higher flow rate of the
hydraulic fluid.
2. The control device according to claim 1, wherein the auxiliary
choke (16) is switched off once again after the vehicle axle has
moved from its limit stops by at least 2 mm.
3. A vehicle which incorporates the control device according to
claim 1.
4. A tractor which incorporates the control device according to
claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a device for controlling the flow
rate of hydraulic fluid in a supply line to the cylinder chambers
of suspension cylinders in vehicles, especially tractors, having a
permanent suspension axle, whose height is regulated by a level
control device, a choke being inserted into the supply line for
limiting the flow rate of the hydraulic fluid.
[0003] 2. Description of Related Art
[0004] From German Patent 42 42 448, a hydropneumatic suspension
device is known for vehicles having high load-bearing requirements
and having a load-sensing pump as a pressure supply, in which
static load changes are compensated for by increasing and
decreasing control processes. The dynamic position change is
measured by electrical sensors and is conveyed to the level control
device as an averaged signal. To adjust the control speed, a choke,
through which fluid can flow in both directions, is inserted into
the supply line leading to the suspension cylinder circuit.
However, this choke is an obstacle for rapid pressure adjustment in
response to large load changes.
[0005] An improvement is achieved by the device described in German
Patent 197 19 075 A1, which, in the decreasing control mode, makes
possible an essentially identical volume flow, thus, at the same
time, making possible the decreasing control processes,
irrespective of the varying static pressure level. This solution
makes it possible to use a larger control nozzle, which permits
higher control quantities at lower axle loads, thus shortening the
adjusting times. When the vehicle axle reaches the limit stops in
particularly high load changes, this measure is not sufficient.
SUMMARY OF THE INVENTION
[0006] It is an object of the invention to create a suspension
concept that, in response to load changes, keeps the adjustment
times short, up to point of reaching the limit stops. It is a
further object of the invention to provide such 10 a suspension
design that is comfortable and soft overall.
[0007] These and other objects of the invention are achieved in a
device for controlling the flow rate of hydraulic fluid in a supply
line to the cylinder chambers of suspension cylinders in vehicles,
especially tractors, having a permanent suspension axle, whose
height is regulated by a level control device, a choke being
inserted into the supply line for limiting the flow rate of the
hydraulic fluid. According to the invention, the supply line is
provided with a bypass line that circumvents the choke, an
auxiliary choke, controlled by a control unit via level sensors,
being inserted into the bypass line, the auxiliary choke being
switched on in response to pronounced static load change when the
limit stops of the vehicle axle have been reached, thus permitting
a larger flow rate of the hydraulic fluid. As a result of this
measure, adjusting times in the accumulator are shortened. Using
the bypass line, the pressure adjustment is carried out in a rapid
and short-term manner. As soon as the pressure adjustment is
completed and the vehicle axle has moved slightly from its limit
stops, the auxiliary choke is closed once again and the further
control process can be carried out, for example in the manner
indicated in German Patent 197 19 075. The level control device can
be set so that it disconnects the auxiliary choke as soon as the
vehicle axle has moved from its limit stop by at least two
millimeters. In this manner, the accumulators can be filled up or
emptied to the required load pressure more rapidly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will be described in greater detail
with reference to the following drawings wherein:
[0009] FIG. 1 is a simplified circuit diagram which depicts a
device which can be inserted into a conventional circuit for
overall control.
DETAILED DESCRIPTION OF THE INVENTION
[0010] FIG. 1 illustrates a simplified circuit diagram, which
contains all of the parts relating to the new device. Furthermore,
this device can be inserted into a conventional circuit diagram for
overall control. Valve 1, which is driven for the increasing
control function, is inserted between a pump, which is not depicted
in greater detail, and hydraulic supply line 2, which leads to
suspension cylinder 3. Located in supply line 2, in a familiar
manner, is fixed choke 4, which limits the flow rate in both
directions. Also located in supply line 2 is openable check valve
5, to which control line 6 is connected. Supply line 2 leads
finally to cylinder chamber 7 of suspension cylinder 3 and at the
same time also to the cylinder chamber of a second suspension
cylinder, which is not depicted in greater detail. Also connected
to supply line 2 is pressure accumulator 8, which has the function
of a suspension component. Via a further supply line 9, ring
chambers 10 of suspension cylinder 3 are connected to each other.
Here pressure accumulator 11 is connected as a suspension
component. Control line 6 leads to openable check valve 5, it being
necessary, in the decreasing control function, for the control line
to be acted upon by pressurized oil. The pressure in ring chamber
10 is generally kept constant by a separate control device.
[0011] In the area of choke 4, supply line 2 is provided with a
bypass line 15, into which auxiliary choke 16 is inserted.
Auxiliary choke 16 is controlled by a control unit 17 as a function
of the vehicle axle position. Reference numeral 18 designates
symbolically an electrical level sensor, to whose lever 19 vehicle
axle is connected via a lever system. Reference numerals 0 as well
as I and II indicate the center position and the end positions of
the vehicle axle. On the left side of the FIGURE, the corresponding
position of piston 20 is indicated. In the 0 position, the axle is
in its standard level, and piston 20 is in the center of suspension
cylinder 3. In the drawing, auxiliary choke 16 is in the closed
position. When check valve 5 is closed, the vehicle axle is
suspended by suspension cylinder 3 in conjunction with pressure
accumulators 8 and 11. As soon as the static load changes such that
the limit stops of the vehicle axles are reached, so that positions
I or II are reached, this is transmitted to level regulator 18 via
lever 19 and is communicated to control unit 17 as a signal.
[0012] When the axle load is sharply reduced, in particular when
heavy rear trailer devices are lifted, the axle is pressed into the
rebound limit stops by the excess pressure of accumulator 8 and
lever 19 adopts position I. In response to the subsequent
decreasing control function, pressure line 6 is supplied with
pressure via the undepicted control block, so that pressurized oil
can flow from accumulator 8 via opened check valve 5. In position I
on lever 19, control unit 17 is activated by the signal of level
sensor 18 so as to open choke 16, so that pressurized oil can
escape from the cylinder suspension circuit more rapidly so as to
be able to change the axle position as rapidly as possible.
[0013] When the axle load increases sharply, the axle lies on the
suspension limit stops due to insufficient pressurized oil, and
lever 19 adopts position II, so that, activated by level sensor 18,
control unit 17 opens choke 16, and, in the increasing control
process, by opening valve 1 and releasing check valve 5,
accumulator 8 is filled rapidly to the necessary pressure level in
order to be able to move the axle from the limit stops without a
long delay. After a short lifting motion from the limit stops,
choke 16 is switched off once again so that the axle is reset at
the setpoint level at the regulating speed determined by choke
4.
* * * * *