Abstract:
Equipment for monitoring the performance of an engine fuel injector valve includes a source of pressurized fluid and an injector valve head connected to an injector valve and the source so that pressurized fluid is delivered to the valve. A regulator compensates for changes in pressure of the fluid and enables the change to be effected and maintained. A flow monitor is in the fluid path between the source and the head to monitor the flow of fluid. The source of pressurized fluid maintains a level of pressure in excess of a desired operating pressure. A fluid flow control coupled to a pressure sensor, near the test head indicates the pressure therein so that the flow control effects flow through the fluid path to maintain the pressure at the head.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119 to the foreign application number 9930120.2, filed on Dec. 21, 1999 in United Kingdom. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to monitoring equipment for monitoring the performance of an engine fuel injector valve, comprising a source of pressurized fluid and an injector valve head provided with connection means to enable an injector valve to be connected thereto, the head being connected to the source so that pressurized fluid from the source is delivered to the injector valve when the equipment is in use, there being regulator means of the equipment to compensate for changes in pressure of the fluid at the head owing to pulsed operation of the injector valve when the equipment is in use, as well as to enable a change in pressure to be effected and maintained at the head, and flow monitoring means in the fluid path between the source and the head to monitor the flow of fluid to the head. 
     Hitherto, air piloted pressure regulators have been used as the regulator means. However, such equipment has suffered from a relatively slow response time to pressure changes, especially because of the use of air as the control medium. This results in an undesirable level of hysteresis using such equipment. 
     The present invention seeks to obviate this disadvantage. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to monitoring equipment having the construction set out in the opening paragraph of the present specification, in which the source of pressurized fluid is such as to maintain a level of pressure in excess of a desired operating pressure, and in which the regulator means comprises fluid flow control means coupled to a pressure sensor, which is in or near the test head to provide an indication of the pressure therein so that the flow control means effects an increase or a decrease to flow of fluid through the said fluid path to maintain the pressure of the fluid at the head substantially at the desired operating pressure. 
     Preferably, the flow control means comprises a hydraulic amplifier arranged to operate valve means of the flow control means so as to effect such increase or decrease. 
     An especially fast response to changes of pressure is obtainable if the flow control means comprises a first movable member, transducer means which serves to provide a force which acts on and moves the first movable member in dependence upon the magnitude of an input signal delivered to the flow control means, two inputs connected to deliver pressurized fluid to opposite sides respectively of the first movable member and to opposite sides respectively of a second movable member, and output means from which fluid flows after it has reached the first movable member, in such a manner that movement of the first movable member in a first direction increases the resistance to flow of fluid from one of the two inputs to the said output means, so that pressure of fluid from that input urges the said second movable member in a given direction, whilst movement of the first movable member in a second direction, opposite to the first, increases the resistance to flow of fluid from the other of the said two inputs to the said output means, so that pressure of fluid from that other input urges the said second movable member in another direction opposite to the said given direction, the flow control means further comprising balancing means to balance the movement of the second movable member against the said force, and valve means which are opened to an extent which is dependent upon the position of the second movable member, whereby the extent to which the valve means is opened is dependent upon the magnitude of the input signal, so that the latter effects such increase or decrease. 
     Advantageously, the pressurized fluid delivered by the said two inputs is the pressurized fluid from the said source. 
     Preferably, the balancing means comprise a spring. 
     The valve means of the flow control means is preferably a slide valve, for example a spool valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An example of monitoring equipment embodying the present invention will now be described with reference to the accompanying drawings, in which: 
     FIG. 1 shows a circuit diagram of the equipment, and 
     FIG. 2 shows a diagram of flow control means of the equipment shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The equipment shown in FIG. 1 comprises a tank  10  filled with test fluid. A pump  12  is connected to the tank  10  by way of the test fluid conduit  14 . The pump  12  is connected electrically via a lead  16  to be controlled by a control processor  18 . 
     The pump  12  is connected to deliver test fluid under a pressure of up to 400 bar to a precision servo-electro-hydraulic pressure control valve constituting a flow regulator  20  via a test fluid conduit  22 . A return line  23  returns some of the test fluid from the regulator  20  back to the tank  10 . A temperature controller  24  and a filter  26  are included in the conduit  22  for the purpose of maintaining the temperature of the test fluid and extracting dirt particles from it respectively. There is also a relief valve  28  connected to the conduit  22  via a T-branch  30 . The other side of the relief valve  28  is provided with a return line  32  to return excess test fluid to the tank  10 . 
     Continuing downstream from the flow regulator  20 , the latter is connected via a further conduit  34  to enable test fluid to pass from the flow regulator  20  to an injector valve test head  36 . A filter  38  and a flow meter  40  are connected respectively in the conduit  34  to further clean the test fluid and to provide a measurement of the flow rate of test fluid to the test head  36  respectively. 
     The test head  36  is hollow so as to provide a test fluid chamber  42  which is in communication with the conduit  34 . A connector  44  is provided on the test head  36  to enable an injector valve  46  under test to be connected to the test head in such a fashion as to receive test fluid from the cavity  42 . An injector valve adjuster  47  is connected to enable adjustment of the injector valve  46  via an adjustment rod  48 . 
     A pressure sensor  49  and a temperature sensor  50  are positioned to measure the pressure and temperature respectively of the test fluid in the cavity  42 . Electrical connections are made respectively from the flow meter  40 , the pressure sensor  49  and the temperature sensor  50  to inputs of the control processor  18 , and electrical connections are made from outputs of the control processor  18  respectively to the pump  12 , the flow regulator  20 , the injector valve  46  under test, and the injector valve adjuster  47 . 
     A further output  52  from the control processor  18  provides data for display and/or recordal, including in particular cumulative values of the volume of test fluid which is injected through the injector valve  46  per injection. 
     A collecting vessel  54  is located to receive test fluid released from the injector valve  46 , and the return line  56  enables this collected test fluid to be returned to the tank  10 . 
     Further details of the flow regulator  20  are shown in FIG.  2 . Such a device is particularly accurate and fast in correcting for or adjusting the pressure of test fluid in the cavity  42 . 
     The flow regulator  20  comprises an electrical coil  60  which surrounds a magnetizable rocker  62  pivotally mounted about a pivot  64 . Permanent magnets  66  are arranged at an end of the rocker  62  which is beyond the coil  60 , to create a magnetic field, the lines of which extend transversely of the rocker  62 . 
     Located around the rocker  62  on the side of the pivot  64  thereof which is further from the coil  60  is a hollow flexible walled housing  68  which forms a seal around the rocker  62  without preventing rocking of the rocker  62  about its pivot  64 . Two inwardly directed opposing nozzles  70  are provided within the housing  66  are connected to cavities  72  and  74 , connected respectively to the two nozzles  70 . 
     These cavities  72  and  74  are in communication respectively with opposite sides of a slider  76  of a slide valve  78 . The slider  76  is coupled to the end  80  of the rocker  62  which is further from the permanent magnet  66  via a spring  82 . 
     Test fluid inlets  84  open into the cavities  72  and  74  respectively and test fluid outlet  86  provides an outlet from the interior of the housing  68 . The outlet  86  is connected to the return line  23  of FIG.  1 . The slide valve  78  is provided with an inlet  88  and outlet  90  connected respectively to the conduits  22  and  34 . The inlet  88  and outlet  90  are in alignment with one another. A bore  92  through the slide  76  connects the outlet  90  to the inlet  88 , and the effective available cross-section for test fluid passing through the bore  92  is determined to the extent to which the latter is in registration with the inlet and outlet  88  and  90 , which in turn is dependent upon the axial position of the slide  76  within the slide valve  78 . 
     Operation of the equipment is as follows. The injector  46  under test is secured to the head  36  by way of the connector  44 . Test fluid from the tank  10  is pumped into the system by way of the pump  12  and air is purged from all cavities and conduits in the system. The pump is set to operate by the control processor  18  at a pressure slightly higher than the desired pressure for test fluid within the head  36 . Test fluid is urged by the pump  12  into the conduit  22  so that it passes through the temperature controller  24  and the filter  26  to ensure that it has the right temperature and cleanliness, respectively. Test fluid continues from the conduit  22  through the flow regulator  20 , the further filter  38 , and the flow meter  40  before it reaches the test head  36 . The control processor  18  operates the injector valve  46  so that the latter is caused to inject fluid into the collecting vessel  54  from the interior  42  of the test head  36 . 
     The output from the flow meter  40  fed to the control processor  18  enables the latter to provide data output signals at its output  52  indicative of the volume of fluid discharged from the injector valve per injection. If desire or necessary, an adjustment may be made to the injector valve  46  by the control processor  18  via the injector valve adjuster  47  and the adjustment rod  48 . 
     The temperature sensor  50  enables an adjustment to be made to the output data signals at the output  52  by the control processor  18  to compensate for any difference in temperature between the desired temperature and the actual temperature. It also enables the control processor  18  to transmit a control signal to the temperature control  24  to adjust the temperature of test fluid flowing therethrough and thereby bring the temperature in the test head  36  closer to the desired temperature. 
     In the event that the pressure in the test head interior  42  as indicated by the sensor  48  differs from the desired pressure, this is compensated for by the control processor  18 , which detects this difference by virtue of the electrical connection it has with the pressure sensor  48 , and changes its control output to the flow regulator  20  accordingly. The manner in which the flow controller  20  operates will now be described with reference to FIG.  2 . 
     Pressurized test fluid from the conduit  22  is fed to the inlet  88 , via the bore  92  to the outlet  90 , the amount of flow through the bore  90  being determined by the extent to which the latter is in registration with the aligned inlet and outlet  88  and  90 , respectively. 
     Pressurized test fluid from the conduit  22  is also fed through the inlets  84  to fill the cavities  72  and  74 . Test fluid flows from the cavities  72  and  74 , via the nozzles  70  within the housing  68  and out from the housing  68  via the outlet  86  from whence it is returned via the return line  23  to the tank  10 . In the event that the electrical current through the coil  60  is increased, so as to magnetize the rocker  62  to a greater extent so that the end  62  thereof moves in the direction of the arrow-head shown adjacent thereto towards the right viewing in the direction of the diagram, a portion of the rod  62  immediately below the pivot  64  will then move closer to the nozzle  70  connected to the cavity  72  than it is to the other nozzle  70 . This reduces the extent to which test fluid can now flow from the cavity  72 , with the result that the pressure therein increases and urges the slider  76  in the direction of the arrow shown adjacent thereto towards the right viewing the apparatus in the manner shown in FIG.  2 . This pulls the end  80  of the rocker  62  in the direction of the arrow shown adjacent thereto towards the right viewing the apparatus as in FIG. 2 so as to increase the flow of test fluid through the nozzle  70  connected to the cavity  72 . Ultimately, a balanced position for the rocker  62  is achieved once again, but with the slider  76  moved further towards the right so that the force acting at the lower end of the rocker  62  compensates the force acting on the upper end of the rocker  62 . A corresponding movement of the slider  76  in the opposite direction will follow a decrease in the current through the coil  60  and a momentary increase in the pressure of test fluid in the cavity  74 . In this way the flow through the bore  92  is proportional to the current passed through the coil  60 . A very rapid compensation to the flow through the regulator  20  to compensate for any change in pressure at the head  36  is thereby achieved by virtue of the hydraulic amplifier which includes the cavities  72  and  74 . 
     In the event that a change in pressure is desired at the test head  36  during the course of the test procedure, the control processor  18  changes the electrical current delivered to the coil  60  of the flow regulator  20  and the flow regulator  20  speedily brings the value of the pressure of the test fluid in the test head  36  to the new desired pressure. 
     The illustrated equipment may provide the following advantages: 
     Very fast transient response times so that pressure changes can be achieved in less than 0.5 seconds. 
     Very accurate pressure control over a wide pressure range. Tests have shown control to better than +/−0.05% of value for both steady state and transient flow changes. 
     Operation with low viscosity test fluids (this is outside the normal operating viscosity range for this type of valve). 
     Insensitivity to pulsations caused by the injector. 
     Insensitivity to flow changes caused by changes to the injector duty cycle. 
     Numerous variations and modifications to the illustrated equipment may occur to the reader without taking the resulting construction outside the scope of the present invention. 
     To give one example, a gas spring may be provided to dampen the oscillatory changes of the pressure of the test fluid in the interior  42  of the test head  36 . The slide valve  78  may be in the form of a spool valve. 
     Another example of a modification would be the use of a pressure control valve with a return line when the injector is switched off to cope with any excess flow under those conditions.