Valve

A housed valve is proposed which serves in particular as a metering and distribution valve for a fuel injection system of a mixture-compressing internal combustion engine with externally supplied ignition. The valve includes a control slide with a control edge and at least two control slits. The control edge opens the control slits to a greater or lesser extent depending on the relative movement between the control slide and the control slits. A helical spring is supported on one control slide end, the end of the spring oriented toward the control slide being bent at an angle and arranged to protrude into an opening of the control slide end, while the other end of the spring is connected in a twist-free manner with the valve housing. As a result, there is a friction-free means of securing the control slide from twisting, so that deviations in the fluid quantities metered at the individual control slits can be equalized during the assembly of the valve by retroactive machining of the control edge in the various areas associated with the control slits.

BACKGROUND OF THE INVENTION 
The invention relates to a valve, in particular a metering and distribution 
valve for a fuel injection system, which includes a control slide provided 
with a control edge, and a valve housing provided with two control slits 
which are opened by the slide control edge to a greater or lesser extent 
upon a relative movement between the control slide and the control slits. 
A valve is already known, in particular a distribution and metering valve 
in a fuel injection system for mixture-compressing internal combustion 
engines with externally supplied ignition, in which as a result of the 
differences in height of the control slits necessitated by manufacturing 
considerations the fuel quantities metered for the individual cylinders of 
the engine deviate from one another to an undesirably great degree, 
especially in the idling range, causing difficulties in setting the idling 
in the system. A retroactive machining of the control edge of the control 
slide in order to balance out the differences in height of the control 
slits is useful only if twisting of the control slide relative to the 
individual control slits is prevented. If the twisting of the control 
slide is prevented by means of a pin, which is connected to the control 
slide and can slide in a groove of the valve housing, then the result is 
an undesirable increase in the frictional force engaging the control 
slide. 
OBJECT AND SUMMARY OF THE INVENTION 
The valve according to the invention includes a helical spring which is 
supported at a first end of the control slide. The end of the spring 
orientated towards the control slide is bent at an angle and arranged to 
protrude into an appropriate embodied opening at the first end of the 
control slide, and the opposite end of this spring is connected with the 
valve housing in a twist-free manner. 
The valve according to the invention has the advantage over the prior art 
that the control slide is secured against twisting without increasing 
friction, while assembly is simple and costs are low. In addition, the 
control slide is held in a predefined outset position by the helical 
spring whenever the valve is not functioning. 
The invention will be better understood and further objects and advantages 
thereof will become more apparent from the ensuing detailed description of 
a preferred embodiment taken in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, a fuel injection system is shown which includes an intake 
manifold 1 having a conical section 2 which contains an air flow rate 
member 3, beyond which there is located an intake tube region 4 containing 
an arbitrarily settable throttle valve 5. Aspirated air flows through the 
intake tube in the direction of the arrow to a manifold 6, from which it 
is directed via individual intake tube regions 7 to one or more cylinders 
8 of an internal combustion engine. 
In the present case, the air flow rate member 3 is a baffle plate disposed 
transversely with respect to the direction of air flow and capable of 
displacement within the conical region 2 of the intake tube as an 
approximately linear function of the air flow rate through the tube. The 
air pressure between the air flow rate member 3 and the throttle valve 5 
will be constant, provided that the restoring force acting on the air flow 
rate member 3 is constant and that the air pressure ahead of the member 3 
is also constant. The air flow rate member 3 controls the opening of a 
metering and distribution valve assembly 10. The motion of the air flow 
rate member 3 is transmitted by an operating lever 11, which is pivoted on 
the same shaft as a correction lever 12 and which actuates the control 
slide 14, which is the movable member of the metering and distribution 
valve assembly 10. A mixture control screw 15 permits an adjustment of the 
desired fuel-air mixture. The end face 16 of the control slide 14 remote 
from the lever 11 experiences the pressure of a control fluid, which is 
exerted upon the air flow rate member 3 and acts as a return force in 
opposition to the force of the flowing air. 
Fuel is supplied by an electric fuel pump 19, which aspirates fuel from a 
fuel tank 20 and delivers it through a storage container 21, a filter 22 
and a fuel line 23 to the fuel metering and distribution assembly 10. 
The fuel supply line 23 splits into several branches which lead to chambers 
26 of the fuel valve assembly 10. One side of a diaphragm 27 in each 
chamber is affected by fuel pressure. The chambers 26 also communicate 
with an annular groove 28 of the control slide 14. Depending on the axial 
position of the control slide 14, the annular groove overlaps control 
slits 29 to varying degrees, permitting fuel to flow into chambers 30 
which are divided from the chambers 26 by the diaphragm 27. From the 
chambers 30, fuel flows through the injection channels 33 to the 
individual injection valves 34, which are located in the vicinity of the 
engine cylinders 8 in the intake tube region 7. The diaphragm 27 is the 
movable valve member of a flat seat valve which is held open by a spring 
35 whenever the fuel injection system is not operating. The diaphragm 
boxes, defined in each case by a chamber 26 and a chamber 30, insure that 
the pressure drop at the metering valve 28, 29, 31 is substantially 
constant, independently of the fuel quantity metered at the metering valve 
28, 29, 31 and flowing to the injection valves 34. This insures that the 
metered-out fuel is exactly proportional to the control path of the slide 
14. 
During a pivoting displacement of the operating lever 11, the air flow rate 
member 3 is moved into the conical region 2 so that the varying annular 
cross section between the flow rate member and the conical wall remains 
proportional to the displacement of the air flow rate member 3. The force 
which generates the restoring force on the control slide 14 is a 
pressurized fluid, which, in this case, is fuel. To provide this fluid, a 
control pressure line 36 branches off from the main fuel supply line 23 
via a decoupling throttle 37. The control pressure line 36 communicates 
via a damping throttle 38 with a pressure chamber 39 which is provided in 
the valve housing 32 and into which one end face 16 of the control slide 
14 protrudes. 
The control pressure line 36 contains a control pressure valve 42, which 
permits control fluid to return to the fuel tank 20 via a return line 43 
without pressure. The control pressure valve 42 permits changing the 
pressure which produces the restoring force during the warm-up of the 
engine in accordance with time and temperature. The control pressure valve 
42 is a flat-seat valve having a fixed control valve seat 44 and a 
diaphragm 45, which is urged in the closing direction by a spring 46. The 
spring 46 acts via a spring support 47 and a transmission pin 48 upon the 
diaphragm 45. When the engine temperature is below the normal operating 
temperature, a first bimetallic spring 49 acts in opposition to the force 
of the spring 46. The bimetallic spring 49 carries an electric heater 50, 
the operation of which after starting causes a diminution of the force of 
the bimetallic spring 49 on the spring 46, and by this means the control 
pressure in the control pressure line 36 increases. 
Branching off from the fuel supply line 23 is a line 53, in which a 
pressure regulating valve 54 is disposed. By means of this pressure 
regulating valve 54, a constant fuel pressure is maintained upstream of 
the metering valve 28, 29, 31. The pressure regulating valve 54 shown by 
way of example in the drawing has a regulating piston 55, which can be 
displaced by the fuel pressure in the line 53 counter to the force of a 
regulating spring 56, so that fuel can flow out of the line 53 over a 
regulating edge 57 and back into the fuel container 20. A blocking valve 
58 can be opened simultaneously by the regulating piston 55 as it opens, 
the blocking valve 58 being disposed directly downstream of the pressure 
control valve 42 in the return line 43. To this end, the regulating piston 
55, as it opens and with the engine operating, engages an actuation pin 
59, which displaces the movable valve member 60 in the opening direction 
counter to the force of a blocking spring 61. If the engine is turned off, 
then there is no further supply of fuel by the electric fuel pump 19, and 
the pressure regulating valve 54 closes. At the same time, the blocking 
spring 61 engaging the actuating pin 59 displaces the movable valve member 
60 of the blocking valve 58 in the closing direction, so that the escape 
of fuel out of the control pressure line 36 via the pressure control valve 
42 is precluded, and the fuel injection system remains filled with fuel, 
ready for a new start-up of the engine. 
The detail A, indicated in FIG. 1 with broken lines, is shown in FIG. 2 on 
a different scale and in more detail. A helical spring 63 is disposed in 
accordance with the invention in the pressure chamber 39, being supported 
at one end on the end face 16 of the control slide 14 and at the other end 
on the base 64 of a damping sheath 65 embodied in an inverted cuplike 
form. On its side remote from the end face 16 of the control slide 14, the 
base 64 defines the pressure chamber 39. The damping sheath 65 is inserted 
into an appropriate opening 66 of the valve housing 32 and secured against 
twisting. The damping throttle opening 38 is provided in the base 64 of 
the damping sheath 65. As shown in FIG. 3, the end 67 of the helical 
spring 63 oriented toward the base 64 of the damping sheath 65 is bent 
relative to the coiling of the spring. This spring end 67 is secured on 
the base 64, preferably by welding or soldering. The spring end 68 of the 
helical spring 63 oriented toward the control slide 14 is also bent at an 
angle from the spring coil, preferably in such a fashion that it extends 
parallel to the control slide axis and protrudes into an appropriately 
embodied opening 69 of the control slide 14 which is provided eccentric to 
and parallel with the control slide axis. The embodiment and disposition 
of the helical spring 63 in accordance with the invention thus prevents 
twisting on the part of the control slide 14. As a result, the fuel 
quantities metered at the individual control slits 29 can be measured and 
compared at a predetermined control position of the control slide 14, and 
if there are any deviations then the control edge 31 can be retroactively 
machined in the region of the pertinent control slits 29 until such time 
as identical metered fuel quantities result at the individual control 
slits. 
The helical spring 63 is preferably embodied as yielding (that is, not 
stiff), having a flat spring characteristic, and its spring force exerted 
on the control slide 14 is very small in comparison with the force exerted 
on the control slide 14 by the pressure in the pressure chamber 39. When 
the engine is not operating, and the pressure in the lines and the units 
of the fuel injection system may have fallen to a pressure which is less 
than that of the atmosphere by an amount represented by the geodetic 
pressure difference between the fuel container 20 and the pressure chamber 
39, then the spring force of the helical spring 63 is still sufficiently 
great to displace the control slide 14 into its outset position, in which 
position the control slits 29 are closed. 
The foregoing relates to a preferred exemplary embodiment of the invention, 
it being understood that other embodiments and variants thereof are 
possible within the spirit and scope of the invention, the latter being 
defined by the appended claims.