EP1398295A1 - Valve for fuel-tapping - Google Patents

Abstract

The motor vehicle fuel feed valve has the output of the cut off (DEB-pressure volume) controlled through compensation of the feed pressure with a compensating opposing pressure. The valve has a diaphragm with the chamber (6) on one side connected with the fuel feed via a throttle. The opposite side of the diaphragm is exposed to a constant counter pressure via a throttle (5).

Description

The invention relates to a dispensing valve with switch-on blocking controlled by the delivery pressure of the fuel pump, in which the delivery pressure acts against a counterpressure on a shutdown unit in the form of a membrane unit or piston-cylinder unit, which closes the delivery valve at delivery pressures below a predetermined pressure value P _AUS and prevents reopening.

The pressure-controlled switch-on blocking (DEB) for nozzle valves (or pressure controlled safety shutdown like they do is also called) is a safety device. Your principal task is to ensure that the Nozzle is closed when depressurized. This means, that the nozzle valve after switching off the fuel pump switch off automatically at the end of the refueling process got to. It must not engage without the fuel pump switched on, d. H. can be opened by the customer. In addition, may the nozzle when the fuel pump is switched on again do not open automatically.

The DEB is especially with the refueling with amount preselection (Preset refueling) important because here at the end of the refueling process the column stops the fuel flow by turning off the Turns off the feed pump without closing a valve. The snapped Fuel nozzle remains open and can be taken in by the tank customer be hung in the column holder in this state. This carries the following security risk: a subsequent customer takes the snap-on nozzle out of the holder and stops it with the spout down. After a short delay the fuel pump starts before the nozzle in the car's fuel filler neck and fuel emerges unhindered into the environment.

The described risk is reduced by mechanical systems. Here the release button of the nozzle is released, as soon as the nozzle in the column holder from the customer is hooked in. Serve as an actuator for this z. B. recessed cams, bolts or in the column holder Lever. The disadvantages of these systems are that the Customer is included as an additional source of error. false Hooking the nozzle may under certain circumstances Prevent unlatching.

As a further development of the mechanical systems, there are hydraulic systems that cause the nozzle to close automatically after the refueling process. Here, the hydraulic pressure of the fuel flow z. B. converted into a force via a membrane or a piston. This force is used to counteract a spring that unlocks the trigger mechanism of the nozzle. So the nozzle can only be opened above a certain switch-on pressure threshold (P _ON ), since only then the spring force is compensated and a disengagement, ie triggering the trigger, is prevented. If, on the other hand, the hydraulic pressure falls below a certain switch-off pressure threshold (P _AUS ), the hydraulically applied force of the fuel flow is not sufficient to deactivate the spring, ie the trigger is triggered and the nozzle valve switches off automatically.

The respective pressure thresholds depend on various factors, such as B. flow conditions in the nozzle, effective area of the pressure / force transducer, spring forces, etc. P _OFF can therefore also assume smaller pressure values than P _ON .

When refueling with preselected amount, the hydraulic Systems basically the following problem: To achieve the amount specified by the customer in advance Fuel quantity, the fuel pump switches its volume flow shortly before the refueling end suddenly of great performance (e.g. 50 l / min) down to low output (e.g. 3 l / min). When the fuel pump is switched down, a "Vacuum Impact", i.e. H. a brief vacuum occurs up to a stall in the fuel channel. It must now be prevented be that the "vacuum blow" to trigger the DEB leads and thus causes an unwanted closing of the nozzle becomes. A hydraulic system must therefore be between Downshifting and shutting down the fuel pump can "distinguish".

One way to make hydraulic systems insensitive to Making short-term pressure drops is working with one time delay. Here, for. B. of the Fuel pump applied pressure using a check valve chambered in a tap valve and thus temporarily stored. Now the pressure in the supply line drops of this room for a longer period of time, the chambered in the room Relief overpressure via a strong constant throttle. As soon as the cut-off pressure of the DEB is reached, the nozzle is automatically switched off. A short-term Pressure drop in the system, e.g. B. in a "vacuum blow", however, does not trigger the DEB. The throttle on Exit of the buffer space is so strong that the chambered Do not apply pressure for the duration of the vacuum blow or can fall below the cut-off pressure.

The disadvantage of this system is that the nozzle after Refueling is closed slowly. In addition, with such Systems with strong chokes, which are small Have cross sections that are difficult to manufacture and which tend to seal when contaminated in the medium. Because the throttle is at the outlet of the temporary storage space the throttle is sealed Dirt, which is the check valve in the supply line could still happen unhindered, to the malfunction of the DEB. The pressure is chambered in the intermediate storage space and can are no longer mined, d. H. the nozzle would remain the preset fueling opened. Should the customer use the nozzle then unlatch yourself, would be due to the remaining pressure also a new, manual opening of the nozzle at switched off fuel pump possible.

Hydraulic systems are also known which operate with constant Work chokes in the inlet to the DEB. So that Do not get "vacuum blow" to the trigger mechanism of the DEB can and then the nozzle when switching down the pillar is prevented, must also be strong here Chokes with a very narrow cross section can be used. If the medium is contaminated, this could also result Add throttles. Unlike in the case above, this would have been As a result, pressure build-up in the DEB area is no longer possible would. The nozzle may also be used by the customer can no longer be opened while the fuel pump is running. The Refueling process would not be possible.

Systems with a throttle in the DEB inlet are also known, which by the pressure difference between their inlet and outlet pressure can be controlled (see WO 93/13011). Is the delivery pressure higher than the pressure in the DEB pressure chamber, so a notched pin lifted off an o-ring so that the throttle the fuel flow has only a slight resistance. If the delivery pressure drops, the pin settles valve-like on the O-ring, so that fuel only through the notch can flow back and a strong throttling effect occurs. Again, there is the problem of possible Pollution, due to which the pressure in the DEB area would not or would degrade slowly, so that the nozzle would remain open after the preset refueling.

In addition to the pollution problem already mentioned above Strong chokes have another disadvantage here: At high The system switches pressure differences across the throttle slowly. This means that e.g. B. with a short refueling resulting from the high zero delivery pressure of the fuel pump there is a pressure in the DEB room that is still above normal Flow pressure is. So the nozzle would be very close the short preset refueling slowly. A quick one Switch off the nozzle after switching off the metering pump but is absolutely necessary where the DEB additionally the Full hose function of the nozzle takes over (it must be ensured be that the hose leading to the nozzle after filling up, the customer keeps it not at least partially empty at the expense of the next customer can). So in this case the full hose property is not injured, must be during the pressure controlled Switch-off of fuel nozzle escaping fuel quantity be small.

The object of the invention is to create a Dispensing valve of the type mentioned at the beginning, with which on safe The type of switch-on blocking and the negative effects of the vacuum blow can be avoided.

The solution according to the invention is that the inlet to Switch-off device (DEB pressure chamber) by comparing the delivery pressure is controlled with a constant back pressure.

The inflow is therefore changed. In contrast to the state of the Technology (WO 93/13011) does not include the delivery pressure compared to the pressure in the shutdown device (DEB pressure chamber), but with a constant back pressure. In this way it is ensured that there is always an inflow when the Delivery pressure exceeds a predetermined value.

In a particularly advantageous embodiment, that the nozzle valve has a diaphragm valve in which the space on one side of the membrane with the fuel line is connected and in the one provided with a throttle leading to the switch-off unit, closable by the membrane Pipe opens, the other side of the membrane is subjected to constant back pressure.

The arrangement is such that the diaphragm valve is opened when the pressure in the fuel line is greater is as the constant back pressure. Is the pressure in the fuel line less than the constant back pressure, so the membrane due to the back pressure on the closable line pressed and closes it. Is the fuel pump switched on, the membrane is closed by the closable line pushed away and it can fuel over the line and the throttle flow to the shutdown unit so that in the shutdown unit there is pressure through which the nozzle valve is kept open. The throttle can be used as follows will be explained, a relatively small Have throttling effect. If the fuel pump is switched off and if the vacuum blow occurs, the pressure in the shutdown unit does not quickly become proportionate Remove weak throttle. This is because at the moment of the vacuum envelope the pressure in the room on one side of the Membrane is less than the back pressure, so the membrane is pressed against the lockable line and closes it. There is therefore no fuel from the shutdown unit drain off their pressure during the vacuum envelope maintains so that the nozzle remains on. Becomes with the preset refueling, the filling with a lower conveyor speed and thus a lower Delivery pressure continues, the diaphragm valve opens, and the pressure in the cut-off unit can go over the throttle adapt to the delivery pressure, which the valve then always can still keep open.

At least the constant back pressure is expedient partially caused by a spring. It is particularly advantageous it when the constant back pressure is the atmospheric pressure is because you automatically get a very receives precisely defined pressure. But it is also a combination of ambient pressure and spring action possible.

It is expediently provided that the membrane is a housing seals in the substantially middle of the membrane an essentially vertical, lockable line in Form of a pipe neck protrudes. That way is a safe and quick closing of the diaphragm valve guaranteed. The housing is expediently essentially cylindrical. The connection to the fuel line expediently takes place via a lateral cylinder wall.

It has proven particularly useful if the throttle for pressure equalization in a time of 0.1 to 5 seconds is designed, with a time of 0.5 to 3 seconds has proven to be particularly useful.

For this purpose, the throttle has a bore with a length from about 5 to 30 mm and a diameter of about 0.5 to 2 mm. It has a length of approximately 10 to 20 mm and a diameter of approximately 0.8 to 1.5 mm proven to be particularly useful.

The invention thus on the one hand the influence of "Vacuum envelope", on the pressure-controlled switch-on blocking (DEB) blocked during preset refueling to trigger to prevent the DEB when the pump shuts down. The nozzle closes automatically when the fuel pump is turned off, so that the "hose milking" in which a Customer still pushes fuel out of the hose when the Fuel pump is switched off, is prevented. The nozzle closes when the fuel pump is switched off quickly that this so-called full hose property does not get hurt. On the other hand, the nozzle is after starting the fuel pump is ready to be switched on quickly because the Throttle has a relatively weak effect. Since the Throttle forms a relatively large passage, that is System also not sensitive to pollution.

The invention is based on an advantageous Embodiment with reference to the accompanying drawings described in a schematic representation in the Dispenser valve installed diaphragm valve according to the invention shows.

A housing 1 is laterally at 3 via a corresponding line with the fuel supply line and thus the fuel pump connected. The housing is essentially cylindrical and has a tube extension 2 in its lower end face, that protrudes into space 6, which is closed by a membrane 4 which is freely clamped at its edges. In there is a throttle 5 with the pipe neck relatively large bore. The line 7 leads to the pressure chamber a pressure-controlled switch-on blocking.

The operation of a nozzle is not described here as it is well known. The invention could z. B. can be used with the nozzle of WO 93/13011, line 7 would then lead to cylinder 28. The However, the invention can also be used with other dispensing valves be, e.g. B. the nozzle of the European patent application 02 000 727.4. Here would then line 7 to room 27 of Guide piston-cylinder unit 19, 25 of FIG. 3.

The mode of action is as follows.

The membrane 4 seals the space 6 from the environment in which the ambient pressure P _U prevails. The pressure in space 6 is denoted by P ₁ , the pressure in line 2 between diaphragm 4 and throttle 5 is denoted by P ₂ , and the pressure in line 7 behind throttle 5, which is applied to the shutdown unit, is denoted by P ₃ designated. In the depressurized state (P ₁ = P ₂ = P _U ), the membrane 4 lies loosely on the pipe socket 2. If the fuel pump is switched on, a pressure P ₁ builds up in the membrane space 6 which is higher than the ambient pressure P _U. Due to the pressure difference P ₁ -P _U , the membrane 4 is immediately lifted off from the pipe socket 2, so that pressure compensation can take place between the membrane space 6 and the pipe socket 2 without a time delay, ie P ₁ = P ₂ > P _U. The pressure then propagates via the weak throttle 5 into the switch-off unit, which is referred to in the figure as the DEB pressure chamber. Because of the low throttling effect of throttle 5, P ₁ = P ₂ = P ₃ applies after a relatively short time.

The nozzle can only be opened when P ₃ exceeds the switch-on threshold P _ON > P _U. The valve remains open as long as P ₃ does not fall below a certain switch-off threshold value P _OFF , whereby P _{OFF is of course} greater than P _U.

The "vacuum blow" when the fuel pump is switched down towards the end of preset refueling now leads to the pressure P ₁ in the membrane space 6 falling for a certain time far below the ambient pressure P _U. The resulting pressure difference P _U -P ₁ results in a force which immediately presses the membrane 4 firmly onto the pipe socket 2, so that the pressure P ₂ cannot drop during the vacuum change. The nozzle therefore remains open since the relatively high pressure is still present.

The pressure P ₃ chambered in the DEB pressure chamber is only reduced via the weak throttle 5 when the vacuum blow is over, ie the pressure P ₁ has risen again above the ambient pressure P _U and the membrane 4 rises from the tube attachment. Now liquid can flow from the DEB pressure chamber back into the pipe neck 2, so that the pressure P _{3 can} now be adjusted to the now lower pressure P ₁ .

The time that the pressure P ₁ takes to rise from the ambient pressure level P _U to the flow pressure of the smaller metering flow (for example 3 liters per minute) P _MIN is thus bridged. Since the flow pressure P _{MIN is} greater than the cut-off pressure P _OFF , the nozzle remains open when P _{MIN is reached} in the DEB pressure chamber. The weak throttle 5 prevents the pressure in the DEB space from dropping below the switch-off value threshold P _OFF during this time between the end of the vacuum blow (re-reaching the ambient pressure) and the re-establishing of the flow pressure. The valve remains open. Without the diaphragm valve according to the invention, the throttle 5 would have to bridge a much longer period of time. At the above time between the end of the vacuum stroke and the re-establishment of the flow pressure, the duration of the applied vacuum would be added. The throttle 5 would have to have a smaller opening cross section than in the prior art in order to prevent the pressure in the DEB pressure chamber P _{3 from} dropping below the switch-off threshold value P _AUS during this long period of time. The diaphragm valve according to the invention thus closes the inlet to the DEB space as soon as and as long as a "vacuum blow" occurs towards the end of preset refueling. The pressure in the DEB room is chambered for this period. The diaphragm valve according to the invention thus ensures that the DEB can be operated with a weak throttle without the vacuum blow leading to the closure of the nozzle. A weak throttle with a large cross-section in turn allows the nozzle valve to be closed quickly after the fuel pump has been switched off because the switch-off pressure in the DEB space is reached quickly. A weak throttle with a large cross-section prevents the risk of clogging with dirt and guarantees the safe function of the pressure-controlled switch-on blocking. The diaphragm valve according to the invention does not hinder the pressure equalization between the DEB space and the main fuel channel in normal flow operation, ie quick closing of the nozzle after switching off the fuel pump and quick readiness to switch on after switching on the fuel pump are guaranteed.

Claims (10)

Dispensing valve with switch-on blocking controlled by the delivery pressure of the fuel pump, in which the delivery pressure acts against a counterpressure on a shutdown unit in the form of a membrane unit or piston-cylinder unit, which closes the delivery valve at delivery pressures below a predetermined pressure value P _AUS and prevents reopening, characterized in that that the inlet to the shutdown device (DEB pressure chamber) is controlled by comparing the delivery pressure with a constant back pressure. Dispensing valve according to claim 1, characterized in that it has a diaphragm valve in which the space (6) on one side of the diaphragm (4) is connected to the fuel line (3), and in which there is a throttle (5) for Shut-off unit leading, through the membrane (4) closable line (2, 7) opens, the other side of the membrane (4) is acted upon by constant back pressure. Dispensing valve according to claim 1 or 2, characterized in that the constant counter pressure is at least partially caused by a spring. Dispensing valve according to one of claims 1-3, characterized in that the constant back pressure is at least partially the atmospheric ambient pressure. Dispensing valve according to one of claims 2-4, characterized in that the membrane (4) closes a housing (1) into which the closable line (2, 7) in the form essentially perpendicular to the center of the membrane (4) of a pipe extension (2) protrudes. Dispensing valve according to claim 5, characterized in that the housing (1) is essentially cylindrical. Fuel nozzle according to claim 4 or 5, characterized in that the connection to the fuel line (3) takes place via a lateral cylinder wall. Nozzle according to one of claims 2-7, characterized in that the throttle (5) is designed for pressure equalization in a time of 0.1 to 5 seconds. Dispensing valve according to claim 8, characterized in that the throttle (5) is designed for pressure equalization in a time of 0.1 to 2 seconds. Dispensing valve according to one of claims 2-9, characterized in that the throttle (5) has a bore with a length of 3 to 30 mm and a diameter of 0.3 to 2 mm.

Images