Pilot operated flow regulating valve

Abstract: A pilot operated flow regulating valve has pressure governing chamber receiving a moveable pressure receiving member for common movements together with a main valve member (4) of said pilot operated flow regulating valve in relation to a fixed valve seat (1) and by a differential pressure exerted to said pressure receiving member from both surface sides, further has a leak route (16) of small cross-section extending between said pressure governing chamber (8) and either the upstream or the downstream side of said valve seat (1), and has a constant differential pressure control valve for selectively either controlling the pressure inside said pressure governing chamber (8) or for blocking a pilot route extending between said upstream and downstream sides.

Description: The present invention relates to a pilot operated flow regulating valve as defined in the preamble part of claim 1. Such valves are useable to regulate the flow of a fluid by maintaining a constant differential pressure between the upstream and the downstream side of the valve seat. Typical applications of said valves are: regulation of the flow of heated pressurised water passing a pressure loss generating heat exchanger, regulation of the flow of refrigerant through an expansion valve in a refrigerating cycle using carbon dioxide as said refrigerant, regulation of the fuel rate through a controllable fuel injection valve for direct injection in an internal combustion engine, etc., i.e. applications where the fluid at least temporarily undergoes a great pressure differential. Conventionally, in such pilot operated flow regulating valves a pilot route extends between the downstream side of the valve seat and the pressure governing chamber. The main valve member is opened and closed from the downstream side assisted by a constant pressure differential control valve actuated by said solenoid. The passage at the upstream side of the valve seat and the pressure governing chamber communicate with another via a leak route of small cross-section. However, the pressure governing chamber via said leak route then holds high pressure in relation to the downstream pressure when the pilot route is closed during main valve closing. Due to the high pressure differential fluid will then flow from pressure governing chamber to the downstream side through the pilot route and its vicinities and a flow larger than a certain degree always occurs inconveniently. Furthermore, in a pilot operated flow regulating valve as known in practice the initial fluid pressure does not act to generate a closing force at the main valve member in a state where the main valve member has reached its fully closed state so that a relatively strong spring is necessary to retain said fully closed state. Then, in order to open the main valve member again, an operating differential pressure stronger than the force of the spring must be produced. Said operating differential pressure reduces the fluid pressure as controlled by the flow regulating valve, because the valve does not respond unless the initial fluid pressure is sufficiently high to compensate said pressure loss and to overcome the force of the spring. This is an apparent shortcoming, particularly when the initial pressure of the fluid at the upstream side is low. The entire operable pressure range is limited. In the pilot operated flow regulating valve as known in Fig. 2 of US 4,431,020 A the main valve member is pressure balanced relative to the high fluid pressure at the upstream side of the main valve seat. in order to achieve a sufficient closing force for the main valve member two high rate closure springs are needed, one of them directly actuating the main valve member in closing direction, the other actuating the front surface of the pressure receiving member in the pressure governing chamber. Said strong closure spring assembly provided for the main valve member needs a relatively high differential pressure adjusted by the differential pressure control pilot valve when the main valve is to be brought into an open state for regulating the flow. This means that in a first operational phase of the flow regulating valve, namely until the main valve member can be pushed open, flow regulation is carried out by the pilot valve only. As a consequence, in case of high initial fluid pressure at the upstream side of the valve seat an undesirably strong actuating electromagnet is needed in the pilot valve. Moreover, the flow regulating characteristic of the pilot operated flow regulating valve shows a considerable bend at the transition from flow regulation by the pilot valve to flow regulation by the main valve member. Since the pilot valve is actuated by its electromagnet in opening direction, a relatively high rate closure spring is needed to assure a stable closing state of the valve member of the pilot valve. Said high rate closure spring needs a strong electromagnet in the pilot valve. The strong springs provided for the main valve member and the valve member of the pilot valve inevitably cause significant pressure losses in operation of the pilot operated flow regulating valve. In the pilot operated flow regulating valve as known from US 5,687,759 the pressure receiving member coupled to the main valve member directly is actuated by the high pressure at the upstream side of the valve seat. The pilot valve member is actuated by the electromagnet in opening direction. Both, the main valve member and the pilot valve member need strong closure springs inevitably causing significant pressure losses during operation of the pilot operated flow regulating valve. The strong closure spring of the valve member of the pilot valve, has to avoid leakage passing by the closed main valve member but needs a strong electromagnet for the actuation of the pilot valve. In case of relatively low pressure at the upstream side of the valve seat the main valve member cannot be brought into an open state but any flow regulation only is carried out by the pilot valve. The overall flow regulating characteristic may vary for the same current supplied to the electromagnet between a condition with low upstream pressure and a condition with high upstream pressure. It is an object of the invention to provide a pilot operated flow regulating valve of the kind as disclosed eliminating the drawbacks of conventional valves, such that the pilot operated flow regulating valve has an improved operational performance, does not need undesirable high differential pressure for response and eliminates the danger of undesirable leakage flows in the closed state. It is a part of said object to create a pilot operated flow regulating valve capable of definitely stopping a flow of fluid to the downstream side when the pilot route is closed, even though the upstream fluid pressure is high. Furthermore, a pilot operated flow regulating valve is to be provided having a good pressure efficiency and does not cause undesirable pressure losses in the fluid. Said objects can be achieved with the features as contained in claim 1. The respective actuation of the constant differential pressure control valve either opens or closes the main valve member or adjusts its relative position at the valve seat for the desired constant fluid flow. This operational performance is achieved without an undesirable pressure loss, because the leak route allows to relieve the pressure in the pressure governing chamber sufficiently to open the main valve member without a significant pressure loss. Furthermore, since the constant differential pressure control valve selectively also can be brought in a blocking position then the pilot route will be reliably blocked avoiding any undesired leak flow from the high pressure side to the low pressure side even in case of extreme high inlet pressure. Since the inside of the pressure governing chamber holds low pressure as also the passage at the downstream side, no leakage flow occurs from the pressure governing chamber to the downstream side even though the pressure in the passage at the upstream side of the dosed main valve member may be extremely high. According to claim 10 the pressure loss inevitably created by the heat exchanger can be utilised to operate the flow regulating valve. This is carried out by connecting the pressure governing chamber via the leak route with the downstream side of the valve seat. The constant differential pressure control valve is situated between a pipeline at the upstream side of the heat exchanger and the pressure governing chamber. A very reliable operation performance can be obtained even when the initial fluid pressure at the upstream side is low. The flow regulating valve shows a good pressure efficiency without creating significant fluid pressure losses. Preferred embodiments are contained in the other depending claims. Embodiments of the invention will be explained with the help of drawings. in the drawings is: Fig. 1 a longitudinal section of a pilot operated flow regulating valve (first embodiment of the invention), Figs 2 and 3 longitudinal sections of a further embodiment of the invention in an open state and in a fully closed state, respectively, and Fig. 4 a block diagram and longitudinal section of a further embodiment of the invention. The pilot operated flow regulating valves according to the present invention are mainly used when the valve has to be operated under a great differential pressure with a high pressure fluid. This can be the case for an expansion valve in a refrigerating cycle, e.g. using carbon dioxide as a refrigerant, for a direct injection fuel control valve for an internal combustion engine, or for a flow control valve for a high water pressure systems or the like. The embodiment of the pilot operated flow regulating valve as shown in Fig. 1 has a ringshaped valve seat 1 formed in the middle of a pipeline containing high pressure fluid, e.g. with a pressure of 50 to 100 times the atmospheric pressure or more. A pipeline 2 is provided at the upstream side of valve seat 1, while a pipeline 3 is provided at the downstream side of said valve seat 1. Valve seat 1 is formed within pipeline 2 at the upstream side. A main valve member 4 is provided having a cylindrical shape with an end face which is closed at the upstream side and is arranged by insertion and fitting in the valve seat 1 in a freely moveable manner in the direction of its longitudinal axis. On a side wall surface of said main valve member 4 a slit 5 can be provided for flow regulation. At the upstream side of main valve member 4 a stop valve portion 6 is formed as a flange-shaped projection. As soon as stop valve portion 6 is pressed against valve seat 1, the valve has its fully closed state, as shown. From pipeline 3 at the downstream side a cylindrical pressure governing chamber 8 is branching off. Pressure governing chamber 8 has a diameter larger than valve seat 1. A piston or disk-shaped pressure receiving member 9 is inserted in a axially freely moveable manner into pressure governing chamber 8. In this embodiment pressure governing chamber 8 is closed by an exterior bulk head 17. Pressure receiving member 9 is coupled to main valve member 4 into a united body by a coupling member in the form of a connecting rod 10 extending in the axial direction of pressure governing chamber 8. Main valve member 4 and pressure receiving member 9 have to move simultaneously in relation to valve seat 1. Compression coil springs 12, 13 are provided to prevent rattling of main valve member 4 and pressure receiving member 9. Main valve member 4 is receiving pressure in pipeline 2 (upstream side) on one surface and pressure in pipeline 3 (downstream side) on the opposite surface. Pressure receiving member 9 is receiving pressure or pilot pressure in pressure governing chamber 8 at its upper surface and also the pressure in pipeline 3 (downstream side) at its opposite surface. Pressure governing chamber 8 is communicating with the downstream side either (as shown) via a leak route 16 of small cross-section provided in a branch pilot line or directly (indicated by dotted lines) via a leak aperture 16 in pressure receiving member 9 directly. The pressure receiving or cross-sectional area of pressure governing chamber 8 and pressure receiving member 9, respectively, is bigger (e.g. 2 to 10 times bigger) than the pressure receiving area or cross-sectional area of valve seat 1. Therefore, by controlling the pilot pressure in pressure governing chamber 8 the state of main valve member 4 between its opened and closed positions is controlled by means of pressure receiving member 9 and coupling member or connecting rod 10. A pilot route 15 extends from the upstream side of pipeline 2 to pressure governing chamber 8 and is bypassing valve seat 1. Within pilot route 15 a constant differential pressure control valve 20 for the pilot route 15 and, optionally, a shut-off valve 30 are arranged in series. Pilot route 15 consists of three portions 15A, 15B, 15C among which portion 15A is connecting said upstream side with the inlet of constant differential pressure control valve 20; portion 15B is interconnecting a valve seat 21 of said constant differential pressure control valve 20 and a valve seat 31 of shut-off valve 30; and portion C is connecting valve seat 31 with the downstream side. The cross-sectional area of pilot route 15 is preferably larger than the cross-sectional area of leak route 16. Shut-off valve 30 is electromagnetically actuated in order to simply open or shut the pilot line by means of a shut-off valve body 32 co-acting with valve seat 31. Within pilot shut-off valve 30 a moveable iron core 33 is carrying valve body 32. Moveable iron core 33 is arranged to co-operate with fixed iron core 35. A valve closure spring 36 (compression coil spring) is interposed between both iron cores 33, 35. Electromagnetic coil 34 serves to attract moveable iron core 33 via fixed iron core 35 counter to the closing force of closure spring 36 and to open said shut-off valve 30. Without exciting current for electromagnetic coil 34 said closure spring 36 is maintaining shut-off valve 30 in its closed state. As follows, this embodiment will be described when said shut-off valve 30 is in its open state (electromagnetic coil 34 excited). Said constant differential pressure control valve 20 is also an electromagnetically actuated differential pressure valve with a conical pilot valve body 22 arranged at the downstream side of pilot valve seat 21. Pilot valve body 22 is coupled to a moveable iron core 23 which is drivable by an electromagnetic coil towards fixed iron core 25 by the magnetic field as soon as electromagnetic coil 24 is excited. Current on electromagnetic coil 24 is creating a closing force for pilot valve body 22 in relation to valve seat 21. The magnitude of said closing force is adjusted by the current supplied to electromagnetic coil 24. When the value of a current supplied to electromagnetic coil 24 is maintained constant, pilot valve body 22 opens as soon as the differential pressure between the upstream side and the downstream side of pilot valve seat 21 (that is the differential pressure between the inlet and the outlet of pilot route 15) is exceeding the force created by the constant current value. Pilot valve body 22 is closing as soon as the differential pressure becomes smaller than the force created by said constant current value. In this way the differential pressure between the inlet and the outlet of the pilot route 15 is maintained constant. By varying or selecting the value of the current supplied to electromagnetic coil 24 of valve 20 the differential pressure value between the inlet and the outlet of the pilot route can be controlled arbitrarily. The differential pressure value is a minimum in a state where there is no current supplied to electromagnetic coil 24. To the contrary, if maximum current is supplied to electromagnetic coil 24, the connection between the inlet and the outlet of pilot route 15 is blocked. The pilot pressure in pressure governing chamber 8 corresponds to the pressure at the outlet of pilot route 15. As, by constant differential pressure control valve 20, the differential pressure between the upstream side and said pressure governing chamber 8 can be kept constant, thereby the opening state of main valve member 4 is controlled as well as the flow of the pressure fluid flowing from pipeline 2 at the upstream side to pipeline 3 at the downstream side. As a consequence, said flow can also be kept constant. By changing the value of the current supplied to the electromagnetic coil 24 the flow from pipeline 2 to pipeline 3 can be controlled arbitrarily. In case that in the pilot operated flow regulating valve as described the current value for electromagnetic coil 34 of said shut-off valve 30 is set to OFF (no current) said shut-off valve is blocking pilot route 15 by means of closure spring 36. Pressure governing chamber 8 then communicates via leak route 16 with the downstream side or pipeline 3 so that the pilot pressure in governing chamber 8 finally is the same low pressure P1 as in pipeline 3 at the downstream side. Due to the differential pressure between pressure P1 at the downstream side and the high pressure in pipeline 2 at the upstream side stop valve portion 6 of main valve member 4 is pushed against valve seat 1. Main valve member 4 is set to a fully closed state. Since pressure governing chamber 8 has the same low pressure P1 as pipeline 3 at the downstream side, no leak flow can occur from pressure governing chamber 8 into pipeline 3 even though the pressure in pipeline 2 at the upstream side may be very high. A stable zero state of flow can be obtained. In the further embodiment of Fig. 2 pilot route 15 is formed in the interior of said flow regulating valve, namely by an axially through bore formed in coupling member or connecting rod 10 from the lower side of main valve member 4 to valve seat 21 provided at the upper end of said through bore (portion 15A), furthermore, by an inner bore of fixed iron core 25, a flow passage between the periphery of moveable iron core 23 and sleeve-shaped pressure receiving member 9 fixedly connected to fixed iron core 25 (portion 15B), and by a bore in the top portion of pressure receiving member 9 leading into pressure governing chamber 8 (portion 15C). Pilot valve body 22 of constant differential pressure control valve 20 provided within said pilot route 15 is constituted by a rod with a lower conical end seated with clearance within the bore of fixed iron core 25 and being actuatable by moveable iron core 23. The electromagnetic coil 24 for attracting moveable iron core 23 via fixed iron core 25 is disposed externally so as so surround the above-mentioned components. Shut-off valve 30 is constituted by valve seat 31 in the bore of the top portion of pressure receiving member 9 and shut-off valve body 32 protruding from the upper end of moveable iron core 23 towards valve seat 31. Rattling preventing springs 12, 13 are received in pressure governing chamber 8 and below main valve member 4, respectively. In this embodiment moveable iron core 23 as well as electromagnetic coil 24 also serve to actuate shut-off valve 30 to either adjust the closed or opened state of shut-off valve 30. Pressure governing chamber 8 is closed by a pot-shaped cover 17 defining a partition wall firmly secured to the carrying structure of the electromagnetic coil 24 such that all moveable components are received therein. Leak route 16 with small cross-section is constituted between the outer periphery of pressure receiving member 9 and the inner side of partition wall 17 and extends over several circumferential grooves 19 of fixed iron core 25 (three circumferential grooves formed in the outer peripheral surface of fixed iron core 25 in order to reduce a possible pressure loss in leak route 16 defined by the clearance between fixed iron core 25 and outer partition wall 17 of cylindrical shape with a closed tip portion). Main valve member 4 is located opposite to pipeline 2 at the upstream side of valve seat 1. Stop valve portion 6 in this case a disk-shaped rubber part. Pressure receiving member 9 and fixed iron core 25 are coupled together in a united body which is freely axially moveable. Since the pilot pressure and pressure governing chamber 8 is acting on the upper end surface of pressure receiving member 9, while the pressure in pipeline 3 at the downstream side is acting at the lower end surface of fixed iron core 25, fixed iron core 25 also becomes part of pressure receiving member 9 (fixed iron core 25 constitutes one half of pressure receiving member 9). The pressure receiving cross-sectional area of pressure receiving member 9 (and its iron core 25) is bigger than the cross-sectional area of valve seat 1 (e.g. about 2 to 10 times bigger). When current is supplied to electromagnetic coil 24 moveable iron core 23 is attracted to fixed iron core 25 so that pilot valve body 22 is pressed with a corresponding force against pilot valve seat 21. If said current supplied to electromagnetic coil 24 is constant, pilot valve body 22 will be opened as soon as the differential pressure between the upstream side and the downstream side of pilot valve seat 21 is exceeding a certain value. As soon as said differential pressure is decreasing below said value, said pilot valve body 22 will reach a closed state. In this way the differential pressure between the inlet and the outlet of the pilot route 15 can be kept constant. Since the pressure in pressure governing chamber 8 is the outlet pressure of pilot route 15, the differential pressure between pipeline 2 at the upstream side and the pressure in pressure governing chamber 8 can be held constant so that the opening state of main valve member 4 is controlled and the flow of the pressure fluid from pipeline 2 into pipeline 3 can be controlled to be constant. By varying the current value applied to electromagnetic coil 24 the flow of the pressure fluid from pipeline 2 to pipeline 3 can be controlled arbitrarily. If the current value for electromagnetic coil 24 is set to OFF (zero current), spring 36 provided between fixed iron core 25 and moveable iron core 23 will push moveable iron core 23 upwardly (Fig. 3), so that shut-off valve body 32 will be pressed against seat 31 and pilot route 15 will be blocked. At that time the pressure inside pressure governing chamber 8 will reach the pressure in pipeline 3 at the downstream side via leak route 16. Since then the pressure in governing chamber 8 will be the same as in pipeline 3, no leak flow can occur from pressure governing chamber 8 into pipeline 3, and a completely zero flow state can be obtained stably, even if the pressure inside pipeline 2 at the upstream side is very high. In the embodiment of Fig. 4 pilot operated flow regulating valve 100 is provided within a fluid pipeline 101 of a hot water supply equipment containing a heat exchanger 102 heated by a not shown heat source. Since heat exchanger 102 contains a long passage of relatively small cross-section a pressure loss unavoidably occurs in the fluid passing fluid pipeline 1, i.e. a pressure difference occurs between portion 101 a and portion 101b interconnected by heat exchanger 102. Said flow regulating valve 100 is provided between portion 101b and a downstream portion 101c of pipeline 101. The pressure difference generated by heat exchanger 102 might amount e.g. to about 0.2 to 0.5 kg/cm 2 , e.g.. Portion 101b of fluid pipeline 101 extends to the lower surface of main valve member 111 situated opposite to valve seat 112 from the upstream side to open and close fluid pipeline 101. In valve housing a passage of portion 101b is called upstream portion 1p of the flow regulating valve 10, while the passage leading into portion 101 c is called the downstream portion 1q. Pressure governing chamber 113 is branching off from downstream portion 1q. Moveable pressure receiving member 114 (a hard disk) is combined with a flexible diaphragm 115, both separating pressure governing chamber 113 from downstream portion 1q. Downstream portion 1q and pressure governing chamber 113 are connected by leak route 117 provided in pressure receiving member 114, 115 said leak route 117 having a small cross-sectional area. Main valve member 111 is unified with pressure receiving member 114, 115 by coupling member 118 extending axially in relation to valve seat 112. Compression coil spring 116 assists in closing main valve member 111. Compression coil spring 116 is seated in the valve housing around valve seat 112 and constantly is urging pressure receiving member 114, 115 in closing direction of main valve member 111. As a consequence, fluid pressure in portion 101b (in upstream portion 1 p) and the force of compression coil spring 116 act together in closing direction of main valve member 111. Since the cross-sectional area of pressure receiving member 114, 115 is made bigger than the cross-sectional area of valve seat 112, also the pressure in upstream portion 1q is generating a force component in closing direction of main valve member 111. The fluid pressure inside pressure governing chamber 13, however, is acting in the opening direction of main valve member 111. Due to this arrangement main valve member 111 is able to maintain any position in which said forces are balanced. Pressure governing chamber 113 is connected to pipeline portion 101 a (upstream side) by a pilot route 103. In pilot route 103 constant differential pressure control valve 20 is installed. Said constant differential pressure control valve 20 is driven electromagnetically in order to adjust a constant differential pressure. Pilot route 103 is formed with a cross-sectional area bigger than that of leak route 117. A compression coil spring 124 for generating a differential pressure is arranged between fixed iron core 122 and is pushing spherical pilot valve body 125 towards valve seat 126 in a direction from the low pressure side to the high pressure side (i.e., from the side of pressure governing chamber 113 to the side of portion 101a of pipeline 101 (upstream side). When no electric current is supplied to electromagnetic coil 121, pilot valve body 125 is strongly pressed against valve seat 26 by the force of compression coil spring 124 for the differential pressure, and pilot route 103 then is blocked. In this state pressure governing chamber 113 has a pressure equal to the pressure at the downstream portion 1q, namely via leak route 117. Main valve member 111 is pushed against valve seat 112 only by compression spring 116 so that the dosed state of main valve member 111 is created. As soon as electric current is supplied to electromagnetic coil 121, the force of spring 124 acting on pilot valve body 125 is decreasing as magnetic force is produced. Pilot valve body 125 gets separated from valve seat 26 by the differential pressure between portion 101 a of pipeline 101 at the upstream side and the fluid pressure in pressure governing chamber 113. The differential pressure between portion 101 a at the upstream side and the pressure in governing chamber 113 is balanced with the residual force applied to pilot valve body 125 and said differential pressure is maintained at a constant level corresponding to the current value applied to electromagnetic 121. Actually, with increasing current, the pressure in pressure governing chamber 113 will be close to pressure in portion 101 a of pipeline 101 at the upstream side. The fluid pressure in portion 101b of the pipeline is lower by a constant pressure drop than in portion 101 a at the upstream side due to the pressure loss in heat exchanger 102. Pressure receiving member 114, 115 moves in response to the control of the constant differential pressure control valve 20 so that main valve member 111 is separated from valve seat 112 and flow regulating valve 100 reaches an open valve state by which the flow of the fluid entering into portion 101c is controlled to a constant level. As a consequence, the pressure loss inevitably caused by heat exchanger 102 can be utilised even for the operation of flow regulating valve 100. As a result, no additional pressure loss for operating flow regulating valve 100 can occur so that its flow control can be performed definitely even in a environment where the initial pressure at the upstream side of fluid pipeline 101 is low. The application of the pilot operated flow regulating valve as shown in Fig 4 is not limited to the hot water supply equipment. Instead said embodiment as well can be applied to the flow control of refrigerant in a refrigerating cycle and other various kinds of equipment. Basically in the embodiment of Figs 4 a pressure loss inevitably created by a heat exchanger or a similar pressure drop generating device is utilised for the operation of the flow regulating valve having the outline as shown. The main advantage of said arrangement is that no pressure loss will occur for the operation of the flow regulating valve. To the contrary, a very reliable operational behaviour can be obtained even in case that the initial pressure of the high pressure fluid at the upstream side is low.

Claims: A pilot operated flow regulating valve, comprising a main valve member (4) arranged in the vicinity of a valve seat (1) formed in a passage supplying high pressure fluid in such a manner that a closed state occurs when said main valve member (4) contacts said valve seat (1) from a high pressure upstream side (2) of said valve seat (1); a pressure receiving member (9) moveably provided within a pressure governing chamber (8) and coupled with said main valve member (4) into one united body by a coupling member (10) such that the pressure receiving member strictly moves together with and actuates the main valve member (4) by receiving on its front and rear surfaces a pressure present at the downstream side of said valve seat (1) and a pressure inside said pressure governing chamber (8); a leak route (16) of small cross-section extending between the inside of the passage at the downstream side (3) of said valve seat (1) and said rear surface of said pressure receiving member (9) in said pressure governing chamber (8); said pressure governing chamber (8) is formed as a branch of said passage at the downstream side (3) of said valve seat (1); a pilot route (15A, 15B, 15C) communicating the high pressure upstream side (2) of said valve seat (1) and the rear surface of said pressure receiving member (9) in said pressure governing chamber (8); and an electromagnetically actuated control valve (20) within said pilot route, characterised in that that said electromagnetically actuated control valve (20) is a constant differential control valve for maintaining a constant differential pressure between a high pressure inlet and an outlet of said pilot route by opening when said differential pressure exceeds a certain value adjusted by the current supplied, and that with said pilot route blocked said main valve member (4) in its close state is actuated by the high pressure upstream of said valve seat (1). A pilot operated flow regulating valve as in claim 1, characterised in that said constant differential pressure control valve (20) has an actuating electromagnetic coil (24) supplied with current for arbitrarily varying a value of said constant differential pressure up to a value presenting a blocking state of said constant differential pressure control valve and the closed state of said main valve member (4). A pilot operated flow regulating valve as in claim 1, characterised in that an additional shut-off valve (30) is arranged within said pilot route in series with said constant differential pressure control valve (20) for selectively opening or blocking said pilot route (15A, 15B, 15C). A pilot operated flow regulating valve as in claim 1, characterised in that said pilot route at least partially is formed by an inside portion of said coupling member (10) and a through hole of said pressure receiving member (9), and that said constant differential pressure control valve (20) is arranged at said inside portion. A pilot operated flow regulating valve as in claim 2, characterised in that said actuating electromagnetic coil (24) is arranged externally of said pilot route and moves a pilot valve body (22) via a moveably iron core (23) arranged within said pilot route. A pilot operated flow regulating valve as in claims 3 and 5, characterised in that said moveably iron core (23) is actuating said pilot valve body (22) in a direction counter to pressure at said high pressure inlet of said pilot route, and that said shut-off valve (30) is arranged at an end portion of said moveable iron core (23) at a downstream side thereof adjacent to said pressure governing chamber (8). A pilot operated flow regulating valve as in at least one of claims 1 to 5 characterised in that said valve body (22, 125) of said constant differential pressure control valve (20) is provided for co-operation with a valve seat (21, 26) and is loaded in closing direction by the force of a valve closure spring (124) via said moveable iron core (23) located between said closure spring and said valve member, said moveable iron core (23) being attractable either parallel or counter to the force of said closure spring by said actuating electromagnetic coil (24, 121) and via a fixed iron core (25, 122). A pilot operated flow regulating valve as in claims 3 and 6, characterised in that said additional shut-off valve (30) has a valve member (32) co-operating with a valve seat (31) provided in said pilot route, said valve member (32) being loaded in closing direction by the force of a closure spring (36) and a moveable iron core (33) being attractable counter to the force of said closure spring (36) into an open state of said shut-off valve (30) by an electromagnetic coil (34) and a fixed iron core (35). A pilot operated flow regulating valve as in claim 1, characterised in that said front and rear surfaces of said pressure receiving member (9, 114) define pressure receiving areas which are significantly bigger than a pressure receiving area of said main valve member (4, 111), preferably approximately 2 to 10 times bigger. A pilot operated flow regulating valve as in at least one of claims 1 to 9, characterised in that said high pressure upstream side of said main valve member (111) and said valve seat (112) is connected to a fluid pipe line (101b) connected to a downstream side of a pressure loss generating heat exchanger (102), that said high pressure inlet of said pilot route (103) is connected to a fluid pipe line (101, 101a) connected to an upstream side of said heat exchanger (102), and that constant differential pressure control valve by pressure actuation of said main valve member (111) is performing flow control between said upstream side and said downstream side of said heat exchanger (102).

Inventors: HIROTA HISATOSHI, HIROTA, HISATOSHI, Hirota, Hisatoshi, c/o TGK Co., Ltd.
Applicants: TGK CO LTD, TGK CO., LTD.
Application year: 1999
Main classification: G05D7
IPC codes: G05D7