JP3828948B2 - Method for measuring a small fuel injection quantity and measuring device for carrying out the method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a method for measuring a small fuel injection amount, wherein the fuel injection amount is injected into a measurement chamber by a fuel injection valve during an injection process, and an increase in volume of the measurement chamber is detected via a measurement piston. In this case, the measurement piston is brought from the starting position corresponding to the reference volume of the measurement chamber to the end position corresponding to the measurement volume after the end of the injection process against a certain return force, and the reference volume and the measurement volume The amount of injection is calculated from the difference between the measured value and the amount of piston movement. In addition, the present invention relates to a type in which the measurement chamber is discharged to the reference volume again.
[0002]
Furthermore, the present invention is a measuring apparatus for carrying out such a method, wherein a measuring chamber is provided, the measuring chamber is partitioned by one end face of the measuring piston, and the measuring piston is The fuel injected into the chamber can move in the cylinder against a certain return force, and the movement amount of the measurement piston is detected by the distance signal generator. And a valve that is electrically controlled is provided in the pressure relief line, and the valve opens the pressure relief line after the fuel injection into the measurement chamber is completed, and returns the measurement piston. In some cases, the pressure relief line is again closed by a control signal generated by the measuring piston when the measuring piston reaches a defined position.
[0003]
[Prior art]
A method of this type and the apparatus to which it belongs are known from German Offenlegungsschrift 3,916,419. This known method and device does not take into account the switching delay of the controlled solenoid valve provided in the pressure relief line when the reference volume of the measuring chamber is readjusted. Thereby, the measurement result must accept the inaccuracy.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to improve the method of the type mentioned at the outset and to provide a method in which the measurement accuracy is significantly increased even when measuring very small fuel injection quantities.
[0005]
A further object of the present invention is to provide an advantageous measuring device for carrying out such a method.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the method of the present invention maintains a substantially constant return speed of the measurement piston in the process of evacuating the measurement chamber to the reference volume again, and the closing motion characteristic of the electrically controlled valve. Taking into account the switching delay recognized on the basis of the curve, the travel distance of the measuring piston that proceeds within the time of the switching delay is taken into account, and the pressure relief line is connected with the switching threshold placed in front of the starting position of the measuring piston. A switching signal for reclosing by the electrically controlled valve is sent to the electrically controlled valve.
[0007]
Further, in order to solve the above-described problems, in the configuration of the measuring apparatus of the present invention, a pressure limiting valve is additionally disposed in the pressure relief line with respect to the valve that is electrically controlled.
[0008]
【The invention's effect】
According to the present invention, the measurement accuracy is remarkably improved even when an extremely small fuel injection amount is measured. In the method according to the present invention, the reference volume can be maintained with high accuracy based on the fact that the return speed of the measuring piston can be kept constant and the switching delay of the solenoid valve can be obtained. This requires little effort and does not require a separate controller to adjust this reference volume. As a result, a reproducible starting position of the measuring piston and accurate detection of each fuel injection amount are obtained at each measurement. In particular, fluctuations in the measurement result based on dynamic influence on the measurement result due to the difference in return speed of the measurement piston are also avoided.
[0009]
In an advantageous configuration as claimed in claim 2, if the specified travel distance of the measuring piston cannot be exceeded during the injection process, the measuring piston is not moved back, but the individual injection processes are carried out sequentially. By doing so, measurement errors at very small fuel injection quantities are reduced. In this case, in the configuration according to the third aspect, the volume of the injection is measured as a difference between two injections that are continuously performed with respect to the moving distance of the measurement piston.
[0010]
According to the configuration of the measuring device according to the present invention as set forth in claim 4, the measuring piston is further provided with a pressure limiting valve in addition to an electrically controlled valve, in the pressure releasing pipe for releasing pressure in the measuring chamber. A constant return speed of. In an advantageous configuration as claimed in claim 6, the pressure limiting valve comprises a valve member which is exposed to the same pressure as the measuring piston as a return force. As a result, it is possible to adjust a constant differential pressure in the flow cross section of the pressure relief pipe using a spring, so that the outflow amount flowing out from the measurement chamber per unit time and thus the return speed of the measurement piston is kept constant. can do.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the following, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
In order to measure an extremely small fuel injection amount injected by the fuel injection valve 1, the fuel injection valve 1 is inserted into the measuring device 2 as shown in FIG. Such a fuel injection valve 1 is advantageously a high-pressure injection valve used in self-igniting internal combustion engines. The fuel injection valve 1 injects a minimum fuel injection amount into a measurement chamber 3 formed in the measurement device 2. The measuring chamber 3 is formed as a closed cylinder 4 in the illustrated embodiment, in which a measuring piston 5 is slidably arranged. The end face 6 of the measurement piston 5 partitions the measurement chamber 3 in the cylinder 4. The back surface of the measurement piston 5 partitions a gas filling chamber 7 filled with gas, and nitrogen under a certain pressure is supplied from the nitrogen reservoir tank 22 to the gas filling chamber 7. The pressure of the nitrogen gas is adjusted so that the measurement piston 5 can be displaced against the return force of the nitrogen gas when fuel is injected into the measurement chamber 3. The movement of the measuring piston 5 is detected by a distance signal generator 8. This distance signal generator 8 acts on the back side of the end face 6 of the measuring piston 5 with a contact pin 9. The fuel injection valve 1 is mounted on a pipe piece 10 that leads to the measurement chamber 3. A pressure relief line 11 is led out from the measurement chamber 3, and an electrically controlled valve such as an electromagnetic valve 12 is arranged in the pressure relief line 11. This solenoid valve 12 opens and closes the flow passage portion of the pressure relief line 11 as a 2-port 2-position valve. The pressure relief pipe 11 continues to extend downstream of the electromagnetic valve 12, and a pressure limiting valve 14 is provided in the pressure relief pipe 11. Via this pressure limiting valve 14, the pressure relief line 11 communicates with the fuel outflow part without pressure. The pressure limiting valve 14 has a movable wall in the form of a piston 16 that is closely guided in a hole 17 provided in the casing 18 of the pressure limiting valve 14. One end of the piston 16, that is, the first end surface 19 is adjacent to a pressure chamber 20 provided in the casing 18 of the pressure limiting valve 14. The pressure chamber 20 is connected via a supply line 21 to the same nitrogen reservoir tank 22 as the nitrogen reservoir tank that supplies pressure applied to the back surface of the measurement piston 5.
[0013]
The other end of the piston 16, that is, the second end surface 24, partitions the inflow chamber 25. In the inflow chamber 25, a supply pipe line 26 is opened in parallel to the axis of the hole 17. This supply line 26 is always connected to the pressure release line 11 that has entered the pressure limiting valve 14. An outflow passage 27 is led out coaxially with the axis of the hole 17 on the side facing the second end face 24. An opening portion of the outflow passage 27 to the inflow chamber 25 is formed as a valve seat 28. The valve seat 28 cooperates with a ball 29 that serves as a valve member. The ball 29 is fixed to the second end surface 24 of the piston 16. In the range of the outflow passage 27, the plunger 31 is pressed against the valve member 29. The plunger 31 is closely guided in the outflow passage 27 at the rear end. The back surface 33 of the plunger 31 is loaded by a spring 32 supported by the casing of the pressure limiting valve 14. Further, the back surface 33 of the plunger 31 is connected to the pressure relief line 11 that has entered the pressure limiting valve 14. The plunger 31 holds an operating pin 34 on the side facing the valve member 29. This operating pin 34 opens an annular chamber between the outflow passage 27. This annular chamber is always connected to the hole 35 led out from the outflow passage 27 on the side. The hole 35 communicates with a portion of the pressure relief pipe 11 that continues to extend. In this case, the pressure relief line 11 supplies the fuel derived from the pressure limiting valve 14 to the fuel reservoir tank without pressure.
[0014]
Using the above measuring device, the fuel capacity can be sealed in the measuring chamber 3 by the electromagnetic valve 12 that closes the pressure relief line 11. The solenoid valve 12 takes such a position at the start of measurement of a small fuel injection amount. At this time, the measuring piston 5 has taken the starting position. At this starting position, the measuring piston 5 encloses a reference volume of fuel in the measuring chamber 3. This starting position is fed back to the control device 36 via the distance signal generator 8. This control device 36 also functions to control the solenoid valve 12. The fuel in the measurement chamber 3 is at a value defined by the nitrogen pressure in the gas filling chamber 7. In the illustrated embodiment, fuel is injected into the measurement chamber 3 via the fuel injection valve 1 by a fuel injection pump. At this time, an increase in volume occurs, and as a result, the measuring piston 5 is moved. This movement of the measuring piston 5 is also detected by the distance signal generator 8. From the volume difference obtained by subtracting the reference volume from the measured volume measured at the end position of the measurement piston 5 after the injection process, the injection volume is calculated by the control device 36 and a connected computer.
[0015]
In order to adjust the same state for the next measuring process, the measuring piston 5 is again returned to its starting position after the end of the first measuring process. At this starting position, the measuring piston 5 also partitions the reference volume. The return of the measuring piston 5 is performed by opening the pressure relief line 11 with the electromagnetic valve 12. The fuel flowing out at this time first flows into the pressure limiting valve 14 through the pressure relief pipe 11. In the pressure limiting valve 14, the valve member 29 is positioned in the closed position under the action of the pressure in the pressure chamber 20. The pressure in the pressure chamber 20 applies a resultant force to the piston 16 that is greater than the force transmitted to the piston 16 by the spring 32. With the introduction of fuel into the inflow chamber 25, the piston 16 is additionally supplied with pressure from the inflow chamber 25 at the second end surface 24, and this pressure also acts on the piston 16 via the back surface 33 of the plunger 31. The pressure flowing into the inflow chamber 25 is defined by the pressure in the gas filling chamber 7, and on the other hand, the same pressure as the pressure formed in the gas filling chamber 7 also acts on the first end surface 19 of the piston 16, so that the piston 16 Is compensated for the fluid force acting on the piston 16. However, the spring force of the spring 32 additionally acts on the piston 16. At this time, the spring 32, combined with the pressure in the inflow chamber 25, lifts the valve member 29 from the valve seat 28 and allows the fuel to flow out into the hole 35 or the pressure relief line 11 that continues. When the pressure decreases due to an excessive fuel flow cross section in the valve seat 28 provided in the inflow chamber 25, the closing force applied to the piston 16 from the pressure chamber 20 side becomes dominant, and the flow crossing The face is reduced. In this way, such a valve allows a constant pressure drop to be adjusted in the flow cross section between the valve member 29 and the valve seat 28 of the pressure limiting valve. As a result, the measurement piston 5 is returned to the starting position at a constant speed based on the fact that a constant amount of fuel flowing out per unit time is obtained.
[0016]
The return of the measuring piston 5 is terminated by closing the solenoid valve 12. This is because when a predetermined position of the measuring piston 5 detected by the distance signal generator 8 is exceeded, a control signal is sent to the control device 36 and the electromagnetic valve 12 is operated via the control device 36. Is done. The mode of operation of the solenoid valve is apparent from the diagram shown in FIG. In this diagram, the movement of the measuring piston 5 is shown by curve A. Starting from the measuring volume MV corresponding to the predetermined level reached, ie the end position of the measuring piston 5 after the injection process has been carried out, the pressure relief line 11 is opened at the time t1, so that the measuring piston 5 Corresponds to the inclination shown in the figure at a substantially constant speed to its starting position, ie to the reference volume BV reached at time t2. At this position, the measuring piston 5 remains until fuel is again injected into the measuring chamber 3 in a new measuring process at time t3. When fuel is again injected into the measuring chamber 3 at time t3, the measuring piston 5 is displaced, at which time the measuring piston 5 is possibly accompanied by a small overshoot process and then reaches the predetermined end position again. The measuring piston 5 remains in the end position until it is returned to the starting position again by opening the pressure relief line 11 before the introduction of a new measuring cycle.
[0017]
Curve B shows the opening and closing process of the solenoid valve 12. The solenoid valve 12 is controlled by the voltage course in the solenoid valve 12 indicated by curve C. As can be seen from the diagram of FIG. 2, when a voltage drop occurs at the solenoid valve 12 at time t0, the solenoid valve 12 first remains in the closed position and begins opening only at time t1. Such a time delay that occurs between the introduction of the signal and the actual movement of the closing member of the solenoid valve is well known, and such a time delay is effected by the action of the spring of the closing member. So it is constant. Actually, the fuel can flow into the pressure limiting valve 14 only after the opening of the solenoid valve 12 is started. The re-rising side edge at the time t1 ′ of voltage supply or current supply to the solenoid valve 12 again introduces a closing movement of the solenoid valve 12 after a certain delay time. Only when the time point t2 is reached, the solenoid valve 12 is closed after the time point t1 'with a delay of time tE. At this point, the fuel outflow through the pressure relief line 11 is also completely interrupted and the measuring piston 5 is brought into a resting state. For the above reasons, in order for the measurement piston 5 to return to the desired level BV corresponding to the reference volume, the starting point for introducing the closing process of the electromagnetic valve 12 is positioned earlier by time tE. There must be. However, this time corresponds to a certain point in the movement of the measuring piston 5. This is because the measuring piston 5 returns at a constant speed. Thus, a point in the return movement of the measuring piston 5 can be easily captured as a switching threshold, at which the switching between the electrical activation of the closing movement of the solenoid valve and the actual closing movement takes place. Delay is taken into account. This makes it possible to easily obtain a very accurate measurement result and a very accurate maintenance of the starting position of the measuring piston 5.
[0018]
The measuring device can detect a very wide variety of small fuel injection amounts. However, in the case of an extremely small injection amount in the range of fuel pre-injection, for example for a self-igniting internal combustion engine, the disadvantage is that only a very small movement step is carried out as a displacement movement based on the configuration dimensions of the measuring piston. Occurs. In this case, if an attempt is made to return to the starting position, a certain amount of error will occur despite the constant return movement, that is to say the measurement piston return speed which can be kept correspondingly small. . In such a case, the device according to the invention is adjusted in such a way that a return of the measuring piston to the starting position is only possible after the specified displacement of the measuring piston has been exceeded. Such an injection process performed with an extremely small fuel injection amount is first and cumulatively performed a plurality of times until the required displacement of the measuring piston is performed. Such a measurement of the individual injection quantity can be detected as a measurement piston position difference between the individual injection processes. At this time, the position of the measurement piston at the end of the preceding injection is a reference amount that is a reference volume. Such a process is illustrated in FIG.
[0019]
In the case of the first embodiment shown in FIG. 1, the movable wall of the pressure limiting valve 14 is formed as a piston 16, but unlike this first embodiment, in the second embodiment shown in FIG. This movable wall is formed as a diaphragm 116. The diaphragm 116 is tightly clamped and fixed between the first casing portion 118a and the second casing portion 118b of the casing 118 of the pressure limiting valve 114. As in the case of the first embodiment shown in FIG. 1, the movable wall formed as the diaphragm 116 surrounds the pressure chamber 20 already described in the first embodiment at one end surface 119. This pressure chamber 20 is also connected to a nitrogen reservoir tank 22 via a supply line 21. The second end surface of the diaphragm 116 closes the inflow chamber 125 on the side opposite to the pressure chamber 20. In the inflow chamber 125, a supply pipe 126 extending in parallel with the axis of symmetry of the valve body portion 40 inserted in a cylindrical shape in the second casing portion 118 b is opened. The end surface of the valve body portion 40 partitions the other end of the inflow chamber 125. The other end of the supply pipeline 126 is connected to the pressure relief pipeline portion 111a. Further, the valve body portion 40 is provided with an outflow passage 127 as a through hole in the longitudinal axis of the valve body portion 40. An opening portion of the outflow passage 127 to the inflow chamber 125 is formed as a valve seat 128. The valve seat 128 cooperates with the valve head 41 with a conically extending sealing surface that acts as a valve member. The valve head 41 is firmly connected to the diaphragm 116 via the coupling member 42. The valve head 41 has shifted to the guide shaft portion 43, and this guide shaft portion 43 always enters the cylindrical hole of the outflow passage 127 together with the guide piston 44. Further, the guide shaft portion 43 forms an annular chamber 45 together with the outflow passage 27 between the guide shaft portion 43 and a seal surface provided on the valve head 41. The annular chamber 45 is always connected to a pressure relief pipe portion 111 b branched from the outflow passage 127 within the range of the annular chamber 45. The back surface 133 of the guide piston 44 on the side opposite to the valve head 41 is connected to the pressure relief pipe line portion 111 a extending from the electromagnetic valve 12 through the opening of the outflow passage 127 extending from the valve body portion 40. The pressure relief line portion 111 a is also connected to the inflow chamber 25 through the supply line 126.
[0020]
Such a configuration has the following advantages. That is, it is no longer necessary to consider the special movability of the piston 16 of the first embodiment shown in FIG. 1 and the sealing performance that must be maintained with respect to the gas cushion. This is because the diaphragm 116 has high mobility with little hysteresis, and at the same time, the diaphragm 116 guarantees a perfect separation between the pressure chamber 20 and the inflow chamber 125. The guide of the valve member provided with the valve head 41 and the guide shaft portion 43 is received by an outflow passage 127 provided as a guide hole. In this connection, an auxiliary spring such as the spring 32 used in the first embodiment shown in FIG. 1 can be dispensed with based on the fact that a guide with less friction is obtained. In other respects, the working form of the pressure limiting valve is the same as that of the first embodiment shown in FIG.
[0021]
In order to obtain a particularly accurate measurement result, the measuring piston 5 used in the first embodiment shown in FIG. 1 must be formed in a particularly simple manner and is formed as a very thin pot-shaped piston. And is advantageous. On the other side, the measurement results are also influenced by the effect of friction on the piston guide. For this purpose, the guide must be lubricated. This is advantageously done via leaking fuel from the measuring chamber. In this regard, diesel fuel in particular has lubricating properties. However, in order to prevent the leaked fuel from flowing into the gas filling chamber 7, it is necessary to provide a leak groove on the wall of the cylinder that guides the piston. This is illustrated in FIG. In the embodiment shown in FIG. 5, the end face of the measurement piston 105 formed thin as described above also partitions the measurement chamber 103 in the cylinder 104. Fuel is introduced into the measurement chamber 103 by the fuel injection valve 101. This fuel can be led out again through a pressure relief line 111 under the control of an electrically controlled valve 112 as in the first embodiment shown in FIG. The leakage groove is provided as an annular groove 47 in a range that is always covered by the thin outer peripheral wall 48 of the measuring piston 105 of the cylinder 104, and thus forms a closed annular chamber. The annular chamber 47 is connected via a pressure relief line portion 211a extending from an electrically controlled valve 112. The other end of the pressure relief pipe is led out from the annular chamber 47 and opens to the pressure limiting valve 14; 114. Accordingly, the annular chamber 47 is flown by the fuel whose output is controlled by the electrically controlled valve 112, and the thin outer peripheral wall 48 corresponds to the nitrogen pressure formed in the gas filling chamber 7 within the range of the groove. Loaded by fuel pressure. In this way, it is avoided that the thin outer peripheral wall of the piston is deformed in the range of the annular chamber 47. Such deformation can lead to a failure of the measuring piston or at least a deterioration of the mobility. Also, the piston lubrication may be impaired. By using such means, the leaked fuel can escape through the annular chamber 47, so that a satisfactory separation between the gas component and the fuel component is obtained. Further, the inflow of nitrogen into the annular chamber 47 that may occur when the annular chamber 47 is free of pressure is also avoided. When nitrogen flows into the annular chamber 47, at least the piston outer peripheral wall region at the lower end is dried by the nitrogen flow, and the sliding characteristics of the piston may be significantly reduced. By means of the present invention, these disadvantages are sufficiently prevented.
[Brief description of the drawings]
FIG. 1 is a schematic view of a first embodiment of an apparatus according to the invention for carrying out the method according to the invention.
FIG. 2 is a diagram showing the relationship between the temporal movement of a measurement piston and the corresponding electromagnetic valve control and valve member movement.
FIG. 3 is a diagram showing the movement of a measurement piston when measuring a very small fuel injection amount in relation to time.
4 is a cross-sectional view showing another embodiment of the pressure limiting valve shown in FIG. 1. FIG.
FIG. 5 is a schematic view showing still another embodiment of the measuring apparatus shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel injection valve, 2 Measuring apparatus, 3 Measuring chamber, 4 Cylinder, 5 Measuring piston, 6 End surface, 7 Gas filling chamber, 8 Distance signal generator, 9 Contact pin, 10 Pipe piece, 11 Pressure relief line, 12 Solenoid valve , 14 pressure limiting valve, 16 piston, 17 hole, 18 casing, 19 first end face, 20 pressure chamber, 21 supply line, 22 nitrogen reservoir tank, 24 second end face, 25 inflow chamber, 26 supply line, 27 Outflow passage, 28 Valve seat, 29 Ball, 31 Plunger, 32 Spring, 33 Back surface, 34 Actuation pin, 35 Hole, 36 Control device, 40 Valve body part, 41 Valve head, 42 Connecting member, 43 Guide shaft part, 44 Guide piston, 45 annular chamber, 47 annular groove, 48 outer peripheral wall, 101 fuel injection valve, 103 measuring chamber, 104 cylinder, 105 measuring piston 111 pressure relief line, 111a pressure relief line part, 111b pressure relief line part, 112 valve, 114 pressure limiting valve, 116 diaphragm, 118 casing, 118a, 118b casing part, 119 end face, 125 inflow chamber, 126 supply line, 127 Outflow passage, 128 valve seat, 133 back surface, 211a pressure relief pipe section

Claims (16)

A method for measuring a small fuel injection amount, wherein the fuel injection amount is injected into a measurement chamber (3) by a fuel injection valve during an injection process, and an increase in volume of the measurement chamber (3) is measured with a measurement piston (5 In this case, the measurement piston (5) is measured from the starting position corresponding to the reference volume (BV) of the measurement chamber (3) against a certain return force after the end of the injection process. The injection amount is obtained from the difference between the reference volume (BV) and the measurement volume (MV) by the measurement piston movement amount, and after the measurement process, the measurement chamber (3) is brought to the end position corresponding to the volume (MV). The measurement chamber (3) is again brought into the reference volume (BV) via a valve (12) which is provided in the pressure relief line (11) derived from) and is electrically controlled by the movement of the measurement piston (5). In the type that discharges to, the measurement chamber (3) is opened again In the course of discharging until the quasi volume (BV), taking into account the constant maintaining return rate, closing movement characteristic curve based recognized is switched delay valve (12) which is the electrically controlled measuring piston (5) Then, the travel distance of the measuring piston (5) that proceeds within the time of the switching delay is taken into account, and the pressure relief pipe (11) is passed through the switching threshold value placed in front of the starting position of the measuring piston (5). A method for measuring a small fuel injection quantity, characterized in that a switching signal for reclosing by means of said electrically controlled valve (12) is sent to said electrically controlled valve.   After an injection series consisting of a plurality of injection processes or a plurality of injection processes in which the re-discharge of the measuring chamber (3) is cumulatively summed to achieve the defined travel distance from the starting position of the measuring piston (5) The method of claim 1, wherein the method is performed only. An injection series consisting of a plurality of injection processes in which the specified travel distance of the measuring piston (5) was not achieved even after cumulative addition, achieved after each preceding injection process of the measuring piston (5) The method of claim 2, wherein the determined position is used as a reference volume for determining the injection volume.   A measuring device for carrying out the method according to any one of claims 1 to 3, wherein a measuring chamber (3) is provided, the measuring chamber (3) being one of the measuring pistons (5). The measurement piston (5) is movable in the cylinder (4) against a certain return force by the fuel injected into the measurement chamber (3). The amount of movement of the measurement piston (5) is detected by the distance signal generator (8), the pressure relief line (11) is led out from the measurement chamber (3), and the pressure relief line ( 11) is provided with an electrically controlled valve (12), by which the pressure relief line (11) is opened after the fuel injection into the measurement chamber (3) is completed, When the measuring piston (5) reaches the specified position when the measuring piston (5) returns, the measurement In the type in which the pressure relief line (11) is closed again by a control signal generated by the piston (5), an electrically controlled valve ( 12. A measuring device for measuring a small fuel injection quantity, characterized in that a pressure limiting valve (14) is additionally arranged relative to 12).   5. The measuring device according to claim 4, wherein the pressure limiting valve (14) is arranged downstream of the electrically controlled valve (12) formed as a solenoid valve.   The measuring piston (5) is loaded with a constant fluid pressure, the pressure limiting valve (14) has a movable wall (16), which wall (16) is one of the first end faces. In the pressure relief line (11) downstream of the electrically controlled valve (12) at the other second end face (24), which is loaded by the constant fluid pressure in (19). It is loaded by the pressure and the spring force of the spring (32), and together with the action of the spring (32), the action of the pressure on the second end face (24) is caused by the movable wall (16). 6. Measuring device according to claim 4 or 5, wherein the movable adjustable valve member (29) is movable from a closed position.   The movable wall (16) is formed as a cylindrical piston (16) guided in a casing (18) of the pressure limiting valve (14), and a second end face ( 24) partitions an inflow chamber (25) connected to the pressure relief pipe (11) located on the upstream side of the pressure limiting valve (14), and the valve member (29) is connected to the piston (16). ), And the valve member (29) enters the inflow chamber (25) and is provided in the outflow passage (27) opened at this location. 7. Measuring device according to claim 6, cooperating with a seat (28).   The spring (32) loading the piston (16) acts on the piston (16) via a plunger (31) guided on an extension of the outflow passage (27). measuring device.   The measuring device according to claim 8, wherein the back surface of the plunger (31) is exposed to the pressure in the pressure relief line (11) on the upstream side of the pressure limiting valve (14).   The measuring device according to claim 9, wherein the valve member (29) is provided with a ball that is pressed into the piston (16) and press-fitted.   The movable wall is formed as a diaphragm (116) fastened to a casing (118a, 118b) of the pressure limiting valve (114), and a second end face (124) of the diaphragm (116) An inflow chamber (125) connected to a portion (111a) located on the upstream side of the pressure limiting valve (114) of the pressure release pipe is partitioned, and the valve member (129) is formed of the diaphragm (116). The valve member (129) is inserted into the inflow chamber (125) and is provided in the outflow passage (127) opened at this location. 7. A measuring device according to claim 6, cooperating with (128).   The valve member (129) has a valve head (41) provided with a guide shaft portion (43), and the guide shaft portion (43) has an annular groove following the valve head (41). The other end of the annular groove is partitioned by a guide piston (44) provided in the guide shaft portion (43) to form an annular chamber (45) together with the outflow passage (127). The annular chamber (45) is always connected to a portion (111b) of the pressure relief pipe that is led out from the inner wall of the outflow passage (127), and the valve head (41) is connected to a coupling portion ( The measurement according to claim 11, wherein the measurement is connected to the diaphragm (116) via 42) and a sealing surface provided on the valve head (41) controls the outflow passage (127). apparatus.   The back surface of the guide shaft portion (43) opposite to the valve head (41) is also subjected to the pressure in the upstream portion (111a) of the pressure limiting valve (114) of the pressure relief conduit. 13. A measuring device according to claim 12, which is exposed.   The measurement piston (105) is formed as a piston having a thin peripheral wall (48) formed in a pot shape, and the measurement chamber (103) is partitioned with the bottom surface facing outward as an end face. 7. A measuring device according to claim 6, wherein a distance signal generator (8) is connected to the bottom surface inside the piston in a frictional connection manner and is loaded by fluid pressure.   An annular groove (47) is arranged on the wall of the cylinder (104) where the measuring piston (105) is guided, and the annular groove (47) forms an annular chamber together with the measuring piston (105). 15. The measuring device according to claim 14, wherein the annular chamber is always connected to a part (211a) of the pressure relief line located upstream of the electrically controlled valve (12). .   16. The annular chamber (47) is disposed in the pressure relief line portion (211a) between the electrically controlled valve (12) and the pressure limiting valve (114). The measuring device described.

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