High-pressure test platform for testing leakage of fuel pump valve arrangement

Abstract

A high-pressure test platform 10 for testing leakage of a valve arrangement in a component (e.g. a fuel pump 12) comprising a high-pressure test line 11 connected to a source of pressurised test fluid

Description

Technical field The present invention generally relates to a high-pressure test platform configured to perform bleed down measurements on valve arrangements, more specifically at the outlet valves and / or the pressure relief valves of high-pressure fuel pumps. Background Art Engine components such as fuel pumps are conventionally submitted to testing at the end of the production line in order to check the proper sealing of valves arranged therein. A conventional high-pressure fuel pump, as known e.g. from US 10,907,600, is of the displacement type and comprises a body that houses a pumping chamber that cooperates with a reciprocating piston. Fuel is admitted via an electromechanically controlled inlet valve and flow out via an outlet valve. A pressure relief valve is arranged in a return path connecting the valve outlet section to the pumping chamber. Such fuel pump is typically tested under high pressure, in order to detect potential fluid leakage, also referred to as “bleeding”, at the outlet valve or pressure relief valve Current high-pressure test platforms usually comprise a high-pressure test line connected at one end to the outlet port of the fuel pump to be tested, and at the other end to a source of pressurised test fluid. A test section of the test line comprises a pressure sensor and a test chamber that can be isolated from the source of pressurised test fluid by a block valve. A control unit is configured to monitor the variation of pressure in the test section over time. The bleed down measurement process then involves increasing the pressure within the test section to a predetermined value, closing the block valve, thus sealing off the test section, before measuring the variation in pressure and temperature over time in the test section to determine the leakage of the valves in the valve arrangement. A drawback of such high-pressure test platforms is that during bleed down measurements of valve arrangements, the platform itself is susceptible to leak fluid through its block valves. This platform leakage can be misinterpreted as leakage from the valve arrangement to test, thus impacting the validity of the measurements. Technical problem It is an object of the invention to provide a test platform of improved design, which avoids the above-mentioned drawbacks. This object is achieved by a high-pressure test platform as claimed in claim 1. General Description of the Invention The present invention provides a high-pressure test platform for testing leakage of a valve arrangement in a component. The present test platform has been developed for bleed measurements of high-pressure fuel pumps, but can generally find application for bleed testing of components comprising one or more valve arrangements, in fuel systems of other fluid carrying components. The test platform comprises a high-pressure test line connected at one end to a source of pressurised test fluid and at the opposite end to a connector for fluid coupling to a port of the component to be tested. A test chamber (with predefined volume), and a first block valve are serially connected from the connector end, forming a test section. A pressure sensor is arranged to determine a pressure (of the test fluid) in the test section and a control unit is configured to monitor the variation of pressure in the test section over time, i.e. to determine a pressure decay. The pressure drop in the test section may be referred to as bleed down, it can be expressed e.g. as a pressure drop or the rate of change of the pressure (decay). According to the invention, a buffer chamber with a predefined volume is serially connected in the test line between the first block valve and a second block valve, separating the buffer chamber from the source of pressurised test fuel. Hence the test line includes, after the test section coupled to the component under test, a second volume (which is at the same pressure at the beginning of the test) with a respective (second) block valve. The first block valve is thus placed between the test chamber and the buffer chamber at high pressure, instead of being at low pressure. In other words, there is a small pressure differential between the two sides of the first block valve, which allows reducing possible leakage from the test section. In embodiments, the high-pressure test platform further comprises a dirt line branching off from the test section, itself comprising a third block valve, for enabling discharge of contaminated fuel. The dirt line is conventionally provided for purging purposes. In particular, the dirt line further may comprise a second buffer chamber having a predetermined volume connected between the third block valve and a fourth block valve, separating this second buffer chamber from the test section and the discharge area. The technical advantage of this buffer chamber is to reduce the difference in pressure at each side of the fourth block valve, thus preventing / reducing leaks through this valve. Preferably, said first and / or second buffer chamber has / have a predetermined volume in the range of 100 to 300 cm3, in particular about 200 cm3. Preferably, said test chamber has a predetermined volume in the range of 100 to 300 cm3, in particular about 200 cm3. The source of pressurised test fluid may comprise a high-pressure pump, a highly pressurised container (with regulator) and / or a pressure amplifier with a plunger or a piston. The high-pressure test platform may be designed to perform various tests on a fuel pump which typically comprises an inlet valve to let fuel in the pump, a plunger, a pump chamber of which the volume varies with the movement of said plunger to increase the pressure of the fuel, and an outlet check valve to release the fuel contained within the pump chamber once it has reached a sufficient pressure. Said fuel pump may also comprise a pressure relief valve arranged in a channel connecting a section downstream of the outlet check valve with the pump chamber. The pressure relief valve is normally closed and configured to open in case the pressure downstream of the OCV surpasses a pre-determined critical value. The fuel pump may be a high-pressure fuel pump. 06 03 25 A temperature sensor may further be arranged to determine a temperature in a test section of the test line between the connector and the first block valve. Data from the temperature sensor may then be used to eliminate noise in the data from the pressure sensor caused by variations in temperature (e.g. an unexpected 5 temperature increase leading to an increase in pressure). A second pressure sensor is advantageously arranged to determine a pressure in a buffer section of the test line between the first block valve and the second block valve. Data from the second pressure sensor may then be used to measure leakage to and from the buffer section and test the general tightness of the circuit. In practice, 10 the reading of the second pressure sensor may be used to confirm (validate) the reading of the first pressure sensor. For example, the control unit may be configured to measure the pressure variation in the test section after establishing the test pressure in the system. The pressure is monitored in the test section for a predetermined test time period (e.g. between 20 15 and 60 s). The result of the measurement may be expressed as a pressure drop (difference between start pressure, i.e. test pressure, and pressure at the end of the test period). The bleed down level may also be expressed as decay rate, i.e. variation of pressure over time (duration of test period). Additionally, the control unit is advantageously configured to measure / monitor the 20 pressure in the buffer section (between the first and second block valves) to assess leakage in this section. Normally, is the system is fluid tight, the pressure variation in this buffer section should be minimal. A large pressure drop would indicate leakage through the first and / or second block valve. The pressure drop (or decay rate) in the buffer section (measured during the test period) may thus be compared 25 to a predetermined threshold. If the pressure drop (or decay rate) does not exceed that predetermined threshold, then it is considered that there is no leakage in the buffer section. The measured bleed down level in the test section can thus be confirmed. 30 According to another aspect, the invention provides a method for measuring bleed down of a valve arrangement in a component by means of the herein disclosed high-pressure test platform. The method comprises: 06 03 25 - fluidly coupling the component to the connector; - building up pressure in the test line up to a predetermined test pressure; - closing the first and second block valves; - detecting the level of bleed down based on the variation of pressure over 5 time in the test section. The method further comprises: - in parallel to the bleed down detection, monitoring the pressure in the test line in a buffer section between the first block valve and the second block valve; 10 - confirming the level of bleed down if the pressure drop in the buffer section does not exceed a predetermined threshold. In embodiments, the component is a fuel pump comprising an outlet valve arrangement and a pressure relied valve. In such case, a test pressure of up to 50 bar may be used for bleed down measurement of the outlet valve arrangement; and 15 a test pressure of at least 250 bar may be used for bleed down measurement of the pressure relief valve. Description of Preferred Embodiment Figure 1 principle diagram illustrating a high-pressure test platform (or system) 10 20 according to an embodiment of the invention. The test platform 10 may be designed to perform a range of tests on high-pressure fuel pumps. However, the present description will only focus on the test platform section configured for bleed down tests. High-pressure fuel pumps are widely used in the automotive industry to perform 25 delivery of fuel at specific times and pressure values. A High-pressure fuel pump, designated 12 in Fig.1, usually comprises, a body 12.1, a pump chamber 12.2 of which the volume varies with the movement of a reciprocating plunger 12.3 to increase the pressure of the fuel. Fuel is allowed into the pump chamber via an inlet valve (IV) 12.4. An outlet valve arrangement 12.5 is provided to release the fuel contained within the pump chamber once it has reached a sufficient pressure. The outlet valve arrangement typically takes the form of a check valve and is referred to as outlet check valve (OCV). The fuel pump may further comprise a pressure relief valve (PRV) arranged in the pump body, in a passage connecting a section downstream of the OCV with the pump chamber. The PRV is a normally closed check valve, that is configured to open if the pressure downstream of the OCV surpasses a pre-determined critical value. The OCV hence allows fluid to flow back to the pump chamber, thus preventing potentially hazardous situations. Such a fuel pump is e.g. disclosed in patent US 10,907,600. The high-pressure test platform 10 schematically illustrated on Figure 1 comprises a high-pressure test line 11 connected at one end to a source of pressurised test fluid 24 and at the opposite end to a connector 13 for fluid coupling to the outlet port of a high-pressure fuel pump 12. The source of pressurised test fluid 24 may typically comprise pressure amplifier 24 with a plunger or a piston for delivery of pressurised test fluid. The test fluid may be a calibration oil that has similar fluid properties as fuel, as is known in the art. The high-pressure test line 11 comprises a test chamber 14, a first pressure sensor 16 arranged to determine the pressure within the test chamber 14, a temperature sensor 17 arranged to determine the temperature within the test chamber 14, a first block valve 18, a second pressure sensor 19, a first buffer chamber 20 and a second block valve 22. The test platform 10 also comprises a dirt line (for purging) branching off from the test line 11 at the junction between the high-pressure pump 12 and the test chamber 14 to discard contaminated fuel or test fluid out of the test platform. The dirt line comprises a second buffer chamber 28 connected on one end to a third block valve 26 and on the other end to a fourth block valve 30 linked to the test line 11. A control unit 32 is configured to monitor the pressure measured by the pressure sensor 16, and evaluate the pressure variations in the test section. The high-pressure test platform 10 is then used to measure the leakage (bleed down) of the OCV and the PRV of the high-pressure fuel pump 12 according to the following steps: - fluidly coupling the high-pressure fuel pump 12 to the connector 13 of the to the high-pressure test line 11; - opening the first 18, second 22 and fourth 30 block valves, and closing the third block valve 26; - building up pressure in the test line 11 and the dirt line up to a predetermined test pressure. For example, to test the OCV, the test pressure may be up to 50 bar. To test the PRV, test pressures higher than 250 bar are used. - closing the first 18, second 22 and fourth 30 block valves; - detecting the level of bleed down based on the variation of pressure over time in the test section detected by the sensor 16. The technical effect of the first 20 and second 28 buffer chambers is thus to reduce the pressure differential at the first 18 and fourth 30 block valves, respectively. The likelihood of test fluid leaking out of the test section through these valves is therefore decreased, implying that leakage detected by the pressure sensor 16 more likely happened at the OCV and / or the PRV of the fuel pump 12. The high-pressure test platform 10 may also include another test section with connector (not represented) for coupling with the high-pressure fuel pump 12 at its inlet, allowing the test platform to perform other tests on the fuel pump on a different section of the test platform or to pressurise test fluid in the fuel pump during tests. As mentioned previously, only the section of the test platform configured for bleed down testing is discussed and represented on the drawing. It should be noted that connections between the different components of the high-pressure test platform have been represented by lines for the sake of clarity. In reality, the different components are linked by tubes of small cross-sectional area (e.g. of internal diameter between 4 and 8 mm, in particular about 6 mm). In contrast, the test chamber and both buffer chambers have a volume of 200 cm3. The vast majority of the volume within the platform is thus located within the test chamber and the buffer chambers. It should also be noted that outside of leakages through the platform valves and the pump valves, the platform is built completely leak-proof, i.e. platform leakage may only happen around valves. 06 03 25

Claims

1. A high-pressure test platform (10) for testing leakage of a valve arrangement in a component, said high-pressure test platform (10) comprising a high-pressure test line (11) connected at one end to a source of pressurised test fluid (24) and 5 having at the opposite end a connector (13) for fluid coupling to a port of said component;wherein said test line (11) further comprises, serially connected from the connector end, a test chamber (14) having a predefined volume and a first block valve (18);10 wherein a pressure sensor (16) is arranged to determine a pressure in a test section of the test line (11) between the connector (13) and the first block valve (18);wherein a control unit (32) is configured to monitor the pressure in said test section by means of said pressure sensor, and detect pressure decay;15 characterized in that a first buffer chamber (20) having a predetermined volume is serially connected in the test line (11) between said first block valve (18) and a second block valve (22), separating said buffer chamber (20) from the source of pressurised test fuel (24), anda second pressure sensor (19) is arranged to determine a pressure in a buffer 20 section of the test line (11) between the first block valve (18) and the second block valve (22).

2. The high-pressure test platform (10) according to claim 1, further comprising a dirt line branched off from the test section, comprising a third block valve (26), for enabling discharge of contaminated fuel.25 3. The high-pressure test platform (10) according to claim 2, wherein the dirt linecomprises a second buffer chamber (28) having a predetermined volume connected between the third block valve (26) and a fourth block valve (30).06 03 254. The high-pressure test platform (10) according to any one of the preceding claims, wherein said first buffer chamber (20), respectively said second buffer chamber (28), has a predetermined volume in the range of 100 to 300 cm3, in particular about 200 cm3.5 5. The high-pressure test platform (10) according to any one of the precedingclaims, wherein said test chamber (16) has a predetermined volume in the range of 100 to 300 cm3, in particular about 200 cm3.

6. The high-pressure test platform (10) according to any one of the preceding claims, wherein the source of pressurised test fluid (24) comprises a high-10 pressure pump, highly pressurised container, and / or a pressure amplifier with a plunger or a piston.

7. The high-pressure test platform (10) according to any one of the preceding claims, wherein the component is a fuel pump having an inlet valve to let fuel in the pump, a plunger, a pump chamber of which the volume varies with the 15 movement of said plunger to increase the pressure of the fuel, and an outlet check valve to release the fuel contained within the pump chamber once it has reached a sufficient pressure.

8. The high-pressure test platform (10) according to claim 7, wherein the fuel pump further comprises a pressure relief valve located downstream of said outlet 20 check valve to release fuel back in the pump chamber if the pressure downstream surpasses a predetermined critical value.

9. The high-pressure test platform (10) according to claim 7 or 8, wherein the fuel pump is a high-pressure fuel pump (12).

10. The high-pressure test platform (10) according to any one of the preceding 25 claims, wherein a temperature sensor (17) is arranged to determine a temperature in a test section of the test line (11) between the connector (13) and the first block valve (18).06 03 2511. A method for measuring bleed down of a valve arrangement in a component by means of the high-pressure test platform (10) according to any one of the preceding claims, said method comprising:- fluidly coupling the component to the connector (13);5 - building up pressure in the test line (11) up to a predetermined test pressure;- closing the first (18) and second (22) block valves;- detecting the level of bleed down based on the variation of pressure over time in the test section; and- in parallel to the bleed down detection, monitoring the pressure in the test 10 line (11) in a buffer section between the first block valve (18) and the secondblock valve (22);- confirming the level of bleed down if the pressure drop in the buffer section does not exceed a predetermined threshold.

12. The method according to claim 11, wherein the component is a fuel pump 15 comprising an outlet valve arrangement and a pressure relied valve, and wherein:a test pressure of up to 50 bar is used for bleed down measurement of the outlet valve arrangement; anda test pressure of at least 250 bar is used for bleed down measurement of the 20 pressure relief valve.

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