Information
-
Patent Grant
-
6290148
-
Patent Number
6,290,148
-
Date Filed
Monday, September 13, 199925 years ago
-
Date Issued
Tuesday, September 18, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Lerner; Herbert L.
- Greenberg; Laurence A.
- Stemer; Werner H.
-
CPC
-
US Classifications
Field of Search
US
- 239 5333
- 239 5336
- 239 5339
-
International Classifications
-
Abstract
A nozzle needle (60) of a fuel injection valve is guided axially in a nozzle body (50), and it points with its rear end face (61) into a compression chamber (15) and is operatively connected to a damping body (40). The recesses (46, 47, 48) of the damping body (40), together with the damping bore (14), form a fuel-filled damping chamber (40). Upon valve opening, the fuel in the compression chamber is compressed, and thus the valve opening is delayed. If the nozzle needle exceeds the damping stroke (hd), then the fuel is depressurized by a communication with an outflow chamber (12). The damping body is guided over at least part of its length in the damping bore.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a fuel injection valve and a method for setting a predeterminable damping stroke of a fuel injection valve.
In a common rail injection system, before the main injection a preinjection (pilot injection) is made, in order to achieve gentler combustion in the combustion chamber of the internal combustion engine and thus reduce the noise output by the engine. The fuel quantity dispensed into the combustion chamber in the pilot injection is smaller than the fuel quantity in the main injection. In known fuel injection valves, the opening of the injection valve is delayed in order to attain small injection quantities.
From German Patent Disclosure DE 43 40 305 A1, a fuel injection valve is known in which during the valve opening, a defined volume is positively displaced into an annular chamber, and this volume is diverted via a throttle and the valve opening is thus delayed in a defined manner.
From Japanese Patent Disclosure 10122078 A, an injector is known in which a nozzle needle is axially displaceably disposed in the guide bore of a nozzle body and opens with a delay, after the valve opening, up to a predetermined damping stroke. On its upper end, the nozzle needle has a cylindrical shaft, which in turn is subdivided by a shoulder into an upper shaft part of larger diameter and a lower shaft part of smaller diameter. The shaft is disposed axially displaceably in the damping bore of a damping unit. If the deflection of the nozzle needle exceeds the damping stroke, then fuel flows out through the annular gap that is formed by the lower shaft part and the damping bore. The nozzle needle and the shaft are embodied in one piece, comprising a single body.
SUMMARY OF THE INVENTION
The object of the invention to furnish a fuel injection valve in which the valve opening of a fuel injection valve is delayed by means that are simple to produce.
In the invention, upon valve opening, the fuel is compressed in a damping chamber and a compression chamber communicating with the damping chamber, so that a damping force that delays the valve opening acts on the nozzle needle. The damping body is operatively connected to the nozzle needle, and as a function of its position in the nozzle bore it opens up a communication between the damping chamber and the outflow chamber.
The damping body and the nozzle needle are two separate bodies, so that a force oriented radially to their axis, caused for instance by displacement toward one another of the injector bodies that guide the damping body and the nozzle needle, does not lead to shear forces or bending forces on the damping body and/or the nozzle needle.
The damping body is also guided in the damping bore over at least a substantial part of the length of the damping body and/or of the damping bore, and preferably over the entire length of the damping bore, so that canting of the damping body in the damping bore is averted. The annular gap between the damping body and the damping bore can be made so narrow that even given its slight axial length, which at maximum is as long as the damping stroke, it has a sealing effect.
To produce the fuel injection valve and to set the damping stroke, the fuel pressure in the fuel conduit and in the outflow chamber is first measured in a test setup, and from that, a conclusion is drawn about the damping stroke or the total stroke; the damping stroke in the fuel injection valve is then set. Production variations in the damping stroke are advantageously compensated for by the insertion of a compensation disk, whose thickness is selected as a function of the measured damping stroke.
Preferred exemplary embodiments of the invention are described in further detail below in conjunction with the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a longitudinal section through parts of the fuel injection valve having a first damping body;
FIG. 2
is a longitudinal section through parts of a fuel injection valve having a second damping body;
FIG. 2
a
is a cross section taken along the line A—A through the second damping body of
FIG. 2
;
FIG. 3
is a longitudinal section through parts of a fuel injection valve having a third damping body;
FIG. 3
a
is a cross section taken along the line B—B through the second damping body of
FIG. 3
;
FIG. 4
is a longitudinal section through parts of a fuel injection valve having a damping sleeve;
FIG. 4
a
is an enlargement of the detail marked C in
FIG. 4
;
FIG. 5
is a longitudinal section through a device for ascertaining and setting the damping stroke of a fuel injection valve; and
FIG. 6
is a longitudinal section through parts of a fuel injection valve having a compensation disk.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1
shows a longitudinal section through parts of a rotationally symmetrical fuel injection valve, which has a nozzle body
50
and a damping unit
10
, which are preferably planar on their end faces and which are braced against one another, thus creating a pressure proof seal. A nozzle needle
60
is guided axially in the central guide bore
52
of the nozzle body
50
; the tip of the nozzle needle
60
and the tip of the nozzle body
50
form an injection valve, in the form of an encompassing sealing edge or sealing face, with which the injection of the fuel into a combustion chamber is controlled. Upon valve opening, the nozzle needle
60
is deflected out of its closing position, and as a result the injection valve opens and fuel is injected into the combustion chamber.
The rear end of the nozzle needle
60
is preferably embodied as an end face
61
disposed perpendicular to the longitudinal axis
100
of the fuel injection valve, and it points into a compression chamber
15
, which is formed by an end piece of the guide bore
52
of preferably larger diameter and limits the deflection of the nozzle needle
60
to a total stroke h; the total stroke h is equivalent to the maximum deflection of the nozzle needle
60
. The recess for the compression chamber
15
is preferably made in the damping unit
10
, but it can also be made in the nozzle body
50
. The end face
61
of the nozzle needle
50
is operatively connected to a first damping body
40
, which is preferably embodied as a piston with a basically cylindrical shape and is guided in the central damping bore
14
, adjoining the compression chamber
15
, of the damping module
10
. The needle diameter dn, which is equivalent to the diameter on the rear end of the nozzle needle
60
, is greater than the piston diameter dd, which is equivalent to the diameter of the end of the damping body
40
contacting the nozzle needle
60
.
The compression chamber
15
has a chamber volume that is defined by the end face
61
of the nozzle needle
60
, the wall of the compression chamber
15
, and the end face, toward the nozzle needle, of the damping body
40
.
The damping body
40
is subdivided into a first body portion
42
and a second body portion
41
of greater diameter. A spring
20
, via a spring plate
30
, prestresses the damping body
40
toward the nozzle needle
60
.
Beginning at the compression chamber
15
, the damping bore
14
passes along the longitudinal axis
100
of the fuel injection valve and merges with a piston recess
13
for receiving the second body portion
41
and then widens into an outflow chamber
12
, in which the spring
20
and the spring plate
30
are accommodated; thus the piston recess is part of the outflow chamber
12
.
The first fuel conduit
11
extends in the damping unit
10
and merges with the second fuel conduit
51
, which is placed in the nozzle body
50
.
The damping unit
10
and the nozzle body
50
are so firmly braced together by their end faces, preferably via a tension element, that the fuel conduits
11
,
51
and the compression chamber
14
are closed off in pressure proof fashion.
The fuel pressure in the fuel conduits
11
,
51
, in a pressure chamber not shown, acts upon the nozzle needle with an opening force that acts counter to the spring force exerted by the spring
20
. If the fuel pressure in the fuel conduit
11
,
51
exceeds a predetermined fuel pressure, or if the closing force acting on the nozzle needle
60
in the direction of the nozzle tip is reduced via a servo valve, not shown, then the nozzle needle
60
is deflected in the direction of the compression chamber
15
, and as a result the injection valve opens, and fuel is injected into the combustion chamber of the engine. The damping bore
14
surrounds and guides the damping body
40
, and together with the recesses
46
,
47
,
48
of the damping body
40
it defines a fuel-filled damping chamber
45
with a damping volume. The damping body
40
has a central longitudinal bore
46
, which intersects the wall of a transverse bore
47
that extends transversely to the longitudinal axis
100
in the damping body
40
and has one or preferably two openings, which point into an encompassing annular groove
48
made in the damping body
40
.
The compression chamber
15
and the damping chamber
45
communicate hydraulically with one another. In the closing position of the nozzle needle
60
, the encompassing edge, pointing in the direction of the outflow clamber
12
, of the annular groove
48
has an axial spacing from the outflow chamber
12
that is equivalent to the damping stroke hd.
The valve opening is delayed as follows:
During the valve opening, the damping body
40
that is operatively connected to the nozzle needle
60
is deflected along with the nozzle needle
60
. The nozzled needle
60
, at its end face
61
, forces the fuel into the compression chamber
15
.
Since the needle diameter dn is greater than the piston diameter dd, upon valve opening the total volume that is enclosed by the compression chamber
15
and the damping chamber
45
is reduced, and as a result the fuel in the compression chamber
15
and the damping chamber
45
is compressed, and the fuel pressure is increased. As a result, a damping force that counteracts the deflection of the nozzle needle
60
acts on the end face
61
of the nozzle needle
60
. The damping force is dependent on the total volume, on the needle diameter dn, on the piston diameter dd, and on the deflectlon of the nozzle needle
60
. If the deflection of the nozzle needle
60
exceeds a predetermined damping strike hd, then the edge, toward the outflow chamber
12
, of the annular groove
48
of the damping body
40
is located above the damping bore
14
in the outflow chamber
12
,
13
, and as a result fuel flows out of the damping chamber
45
into the outflow chamber
12
via the annular groove
48
, and thus the compressed fuel is depressurized. The edge of the annular groove
48
, the damping body
40
and the damping bore
14
thus form a valve
14
,
48
,
40
. Thus the valve
14
,
48
,
40
opens when the nozzle needle
60
reaches a predetermined desired position. The fuel pressure in the outflow chamber
12
is low in comparison with the pressure in the damping chamber and is preferably equivalent to the fuel pressure in the fuel tank that adjoins the outflow chamber
12
. After the deflection of the nozzle needle
60
by a predetermined damping stroke hd, no further damping force is exerted on the end face
61
of the nozzle needle
60
, and thus the deflection of the nozzle needle
60
is no longer delayed.
The delaying of the motion of the valve opening is advantageously adjustable by means of a suitable selection of the needle diameter dn, the piston diameter dd, the volume of the damping chamber
45
and compression chamber
15
, and the length of the damping stroke hd.
The fuel injection valve is embodied especially advantageously if in short deflection processes of the nozzle needle
60
, of the kind that are usual for a pilot injection into the combustion chamber, the deflection of the nozzle needle
60
is less than the damping stroke hd, so that during the pilot injection the entire deflection of the nozzle needle
60
is damped.
During the main injection, a damped deflection of the nozzle needle
60
over its total stroke h is not desired; instead, what is desired is the fastest possible opening and closing of the nozzle needle
60
, so that a predetermined fuel quantity can be injected into the combustion chamber within a short time. This is attained by delaying the valve opening only during what in comparison with the total stroke h is a short damping stroke hd, while from the damping stroke hd to the total stroke h the valve opening is not delayed by the effect of the compressed fuel.
The delay in the valve opening is adjustable by the aforementioned characteristics, so that during a pilot injection, a predeterminable, small injection quantity is advantageously injected into the combustion chamber. During the motion of the valve closing
60
that is counter to the valve opening, the total volume increases, because of the mutually different needle diameter an and piston diameter dd. Via an inflow conduit, not shown, that has a return valve, replenishing fuel flows from the fuel conduit
11
,
41
into the compression chamber
15
and the damping chamber
45
. During the total stroke h, the motion of the needle closing is not delayed by the fuel in the compression chamber
15
and in the damping chamber
45
.
The damping body
40
and the nozzle needle
60
are embodied as separate bodies from one another, so that a force oriented radially to their axis and caused for instance by displacement of the damping unit
10
and nozzle body
50
counter to one another, does not lead to shearing or bending forces on the damping body and/or the nozzle needle, but merely displaces their end faces counter to one another.
The damping body
40
is guided in the damping bore
14
over at least part of the axial length of the damping body
40
and/or of the damping bore
14
, and preferably over a substantial portion, or all, of the length of the damping bore
14
, so that canting of the damping body in the damping bore is avoided. The annular gap between the damping body
40
and the damping bore
14
is embodied as so narrow that even given its slight axial length from the edge of the annular groove located toward the outflow chamber to the beginning of the outflow chamber
12
, which at most is substantially as long as the damping stroke hd, it has a sealing or at least strongly throttling effect.
The first body portion
41
has a larger diameter than the second body portion
42
, so that when the fuel injection valve is being assembled the damping body
40
will not be inserted incorrectly into the damping bore
14
.
FIG. 2
shows a longitudinal section through parts of the fuel injection valve; in comparison with the first damping body
40
in
FIG. 1
, the second damping body
70
in
FIG. 2
is embodied as a cylindrical body of constant diameter over its entire length. Also, preferably two opposed longitudinal grooves
71
are disposed on the second damping body
70
, from its end face resting on the nozzle needle
50
as far as its second annular groove
72
. The longitudinal grooves
71
are recesses that are made in the damping body
40
. The damping chamber
71
,
72
, comprising the longitudinal grooves
71
and the second annular groove
72
, is advantageously reduced in such as thus amplifies the delaying of the valve opening during the damping stroke hd. The damping body
70
, having a constant diameter, is also easier to manufacture.
In a further embodiment, recesses embodied as longitudinal grooves or cylindrical widenings are made in the wall of the damping bore
14
; they lead from the compression chamber
15
as far as the annular groove
48
.
FIG. 2
a
shows the cross section A—A of the second damping body
70
, with preferably two opposed longitudinal grooves
71
; a symmetrical radial force is advantageously exerted on the damping body
70
by the fuel.
In
FIG. 3
, the damping chamber of a third damping body
80
is formed, like the damping chamber
71
,
72
of FIG.
2
. In contrast to
FIG. 2
, the third damping body
80
is subdivided, as in
FIG. 1
, into a first and a second body portion
81
,
82
.
FIG. 3
a
shows the cross section B—B through the third damping body
80
.
In
FIG. 4
, a longitudinal section is shown through parts of the fuel injection valve; in comparison with the exemplary of
FIG. 2
, a cylindrical piston
90
with a further piston diameter dd
1
is fastened between the spring plate
30
and the nozzle needle
60
; it is surrounded and guided over part of its length by a damping body embodied as a damping sleeve
91
. A second damping bore
97
,
98
is subdivided, for guiding the damping sleeve
91
, into a first portion
97
and a second portion
98
, the latter being disposed in the direction of the spring plate and having a larger diameter. The damping sleeve
91
is guided in the first portion
97
and widens preferably conically in the part of the damping sleeve
91
located in the second portion
98
; the valve seat of the damping bore
97
,
98
and the preferably conical widening of the damping sleeve form a valve
99
, which closes off the damping chamber
93
,
92
from the outflow chamber
12
.
The damping sleeve
91
and the second portion
98
of the damping bore form a damping chamber
93
,
92
, which comprises two longitudinal grooves
92
and a rounded annular chamber
93
adjoining them; this annular chamber merges with a preferably conical face of the damping sleeve
91
, from which point the damping sleeve
91
extends cylindrically to its end face.
The spring plate
30
exerts a closing force on the valve
99
via a damping spring
94
.
In the closing position of the nozzle needle
60
, the end face toward the nozzle needle of the damping sleeve
91
has a damping spacing hd from the end face
61
of the nozzle needle
60
.
In
FIG. 4
a
, this region (detail C) is shown enlarged for the sake of clarity.
A further compression chamber
89
, disposed as in
FIG. 1
, has a chamber volume which is defined by the end face
61
of the nozzle needle
60
, the wall of the compression chamber
89
, the piston
90
, and the end face, toward the nozzle needle, of the damping sleeve
91
.
During the valve opening, the valve
99
remains closed as long as the deflection of the nozzle needle
60
does not exceed the damping stroke hd. Since the needle diameter dn of the nozzle needle
60
is greater than the further piston diameter dd
1
of the piston
90
, the volume of the further compression chamber
89
and of the damping chamber
93
,
92
decreases upon valve opening; the fuel is compressed thereby, and a delay in valve opening results. If the deflection of the nozzle needle
60
exceeds the damping stroke hd, then the end face
61
of the nozzle needle
60
strikes the end face of the damping sleeve
91
and deflects the damping sleeve
91
in the direction of the spring plate
30
. This causes the valve
99
to open, and thus the compressed fuel flows out of the compression chamber
15
and the damping chamber
93
,
92
, and the damping action and the delay in the valve opening thus cease.
The damping stroke hd depends on the production variations in the damping sleeve
91
, damping unit
10
, nozzle needle
60
, and nozzle body
50
. By measuring the axial spacing between the end toward the nozzle needle, of the damping unit
10
and the damping sleeve
91
while the valve
99
is closed, the damping stroke hd shown in
FIG. 4
is determined directly. By inserting a damping sleeve
91
with a sleeve length that compensates for the production variations, a predeterminable damping stroke hd is set.
FIG. 5
shows a device for measuring the damping stroke hd shown in
FIGS. 1-3
. The structure of the damping body
80
and the damping unit
10
in this device are equivalent to that in the exemplary embodiment of
FIG. 3
, but can also be equivalent to the structure of
FIG. 1
or FIG.
2
. In the manufacture of the fuel injection valve, the attained damping stroke hd may deviate relatively sharply from a predetermined desired value, since the damping stroke hd is dependent on the production variations in the damping body
80
, damping unit
10
, nozzle needle
60
and nozzle body
60
. To compensate for the production variations, with the arrangement described below the damping stroke hd of a fuel injection valve is ascertained, and with a thickness between the damping unit
10
and the nozzle body
50
that compensates for the production variations, a predeterminable damping stroke hd is set. An exemplary embodiment with a compensation disk is shown in FIG.
6
.
In
FIG. 5
, a test compensation disk
95
is fastened between the damping unit
10
and the nozzle body
50
and has a fuel conduit
121
and a connecting conduit
95
, which connects the fuel conduit
121
with the damping chamber of the damping body
80
. The damping body
10
, the test compensation disk
95
and the nozzle body
50
are fastened in a test module
120
by a tension element
125
. A setting screw
110
placed in the central bore of the test module
120
acts on the damping body
80
via a setting needle
115
and determines the deflection of the nozzle needle
60
, which is measured via a dial gauge
130
. The inflow pressure of the fuel in a fuel conduit
121
and the outflow pressure in an outflow chamber
122
are measured by a first and second manometer
140
,
150
. The fuel is delivered to the fuel conduit via a throttle, which is disposed upstream of the first manometer
140
. The fuel flows out via a throttle that is disposed downstream of the second manometer
150
.
The method for ascertaining the damping stroke hd is performed as follows:
In the closing position of the nozzle needle
60
, the fuel in the fuel conduit has a maximum pressure pmax. The outflow pressure in the outflow chamber is zero, because no fuel is flowing out into the outflow chamber.
By rotating the setting screw
110
, the nozzle needle
60
is deflected slowly in the direction of the damping unit
10
. The inflow pressure drops steadily until the damping stroke hd is reached, because by the opening of the injection valve, fuel is dispensed into the surroundings. The outflow pressure is still zero.
If the deflection of the nozzle needle
60
exceeds the damping stroke hd, causing fuel to flow via the connecting conduit
96
and the damping chamber into the outflow chamber
12
, the inflow pressure drops and the inflow pressure suddenly rises to the values p
1
and p
2
. Thus the damping stroke hd can be ascertained indirectly from the pressure course at the manometers
140
,
150
.
By further rotation of the setting screw
110
, the nozzle needle
60
is moved onward as far as the total stroke h. The inflow pressure drops, and the outflow pressure rises steadily. When the total stroke h is reached, the inflow pressure adjusts to a minimal value p
3
, and the outflow pressure adjusts to a maximal value p
4
, which does not vary further upon further rotation of the setting screw
110
. The total stroke h can thus be ascertained indirectly from the pressure course at the manometers
140
,
150
.
In
FIG. 6
, parts of a fuel injection valve are shown, in which in a distinction from
FIG. 2
, a cylindrical compensation disk
88
is disposed between the damping unit
10
and the nozzle body
50
, in which compensation disk a fuel conduit
87
and a central disk bore
86
that adjoins the damping bore
14
of the damping unit
10
are made. By the selection of a compensation disk
88
with a predetermined thickness, the damping stroke hd can be set as described in the exemplary embodiment of FIG.
4
. The compression chamber
15
is made preferably in the form of a chamfer in the nozzle body
50
and is bounded by the compensation disk
88
. Upon maximal deflection, the nozzle needle
60
strikes the compensation disk of the nozzle needle
60
and is thus deflected by the total stroke h.
The principle described here of the damping of valve opening can be employed also in fuel injection valves in which the valve opening is effected by an axial motion of the nozzle needle in the direction of the tip of the nozzle, as in the case of pintle nozzles, for example. The piston diameter of the damping body is then greater than the nozzle needle diameter.
One skilled in the art will construct an advantageous fuel injection valve from combinations of the exemplary embodiments described as well, to suit given peripheral conditions.
Claims
- 1. A fuel injection valve, comprising:a valve body formed with a guide bore and a nozzle needle guided in said guide bore, said guide bore discharging into a compression chamber communicating with an outflow chamber; a valve between said compression chamber and said outflow chamber, said valve having a damping body axially displaceable in a damping bore, said damping body connecting the compression chamber with the outflow chamber in dependence on a degree of deflection of the nozzle needle; said damping body and said nozzle needle being two separate bodies operatively connected to one another; said damping body being guided over at least a substantial portion of a length thereof in said damping bore; said damping bore being divided into a first portion and a second portion having a larger diameter than the first portion, and a valve seat merging the second portion with the first portion; and said damping body being a damping sleeve guiding therein a piston in an axially displaceable manner, and said damping sleeve: being guided in the first portion; having a larger diameter at a level of the second portion than at a level of the first portion; and together with the valve seat forming a valve between the compression chamber and the outflow chamber; said piston being operatively connected to said nozzle needle; and said nozzle needle, upon a deflection thereof by more than a predeterminable damping stroke, deflecting said damping sleeve and opening said valve.
- 2. The fuel injection valve according to claim 1, wherein said damping body is formed with an annular groove, with a transverse bore having a wall and an opening ending in said annular groove, and with a central longitudinal bore intersecting said wall of said transverse bore.
- 3. The fuel injection valve according to claim 1, wherein said damping body is formed with at least one longitudinal groove which ends in an annular groove surrounding said damping body.
- 4. The fuel injection valve according to claim 1, wherein said nozzle needle has a given needle diameter and said damping body has a piston diameter smaller than said needle diameter.
- 5. The fuel injection valve according to claim 1, wherein said damping body is divided into a first body portion with said damping chamber and a second body portion having a greater diameter than said first body portion.
- 6. The fuel injection valve according to claim 1, which comprises a compensation disk disposed between said damping unit and said nozzle body.
- 7. The fuel injection valve according to claim 1, wherein said piston has a further piston diameter and said nozzle needle diameter is greater than the further piston diameter.
- 8. The fuel injection valve according to claim 1, wherein a deflection of said nozzle needle at which said valve opens is smaller than a total stroke of said nozzle needle.
- 9. The fuel injection valve according to claim 1, which further comprises a spring disposed to axially prestress said damping body in a direction of said nozzle needle.
- 10. A method of adjusting a predeterminable damping stroke of a fuel injection valve provided with a damping body, which comprises the following steps:measuring a damping stroke attained with a fuel injection valve, by inserting a test compensation disk between said damping unit and said nozzle body, the compensation disk being formed with a connecting conduit between a fuel conduit and a compression chamber; defining a deflection of the nozzle needle by a setting screw; measuring an inflow pressure in the fuel conduit and an outflow pressure in an outflow chamber as a function of the deflection of the nozzle needle, whereby the outflow pressure rises and the inflow pressure falls if the deflection of the nozzle needle exceeds the damping stroke and a conclusion can be drawn from the inflow pressure, the outflow pressure, and the position of the setting screw, about the damping stroke; and setting the damping stroke in the fuel injection valve by introducing a compensation disk between the damping unit and the nozzle body.
Priority Claims (2)
Number |
Date |
Country |
Kind |
198 42 428 |
Sep 1998 |
DE |
|
199 40 558 |
Aug 1999 |
DE |
|
US Referenced Citations (6)
Foreign Referenced Citations (10)
Number |
Date |
Country |
3839812 |
Apr 1968 |
DE |
3041018 |
May 1982 |
DE |
3344723 |
Jun 1984 |
DE |
88 09 257 |
Dec 1989 |
DE |
3900763 |
Jul 1990 |
DE |
4126698 |
Oct 1992 |
DE |
4340305 |
Jun 1995 |
DE |
1110102 |
Apr 1968 |
GB |
2086473 |
May 1982 |
GB |
10-122078 |
May 1998 |
JP |