Pulse-width-regulating valve

Abstract

A pulse-width-regulating valve is for the regulation of a fluid flow or a fluid pressure. The pulse-width-regulating valve comprises a cut-off valve connected in series with an inflow valve, at least one of the cut-off valve and the inflow valve being provided with an axially displaceable or rotatable valve element which has an opening position or a closing position at a distance from a starting position of the valve element. A method of operating a pulse-width-regulating valve comprises: regulating a valve gear device by a valve synchronizer, in accordance with at least two displacement curves; and by one or more valve actuators, displacing or rotating corresponding valve elements arranged in the pulse-width-regulating valve.

Claims

1. A pulse-width-regulating valve configured to regulate at least one of a fluid flow and a fluid pressure, the pulse-width-regulating valve comprising: a valve housing comprising an inlet port, an outlet port, and an intermediate-passage port disposed between the inlet port and the outlet port; a cut-off valve comprising a first valve element having a first through-going fluid passage, the first valve element being movable into and between an open position in which fluid flow from the inflow port to the intermediate-passage port is allowed via the first through-going fluid passage and a closed position in which fluid flow from the inflow port to the intermediate-passage port is prevented; an inflow valve connected in series with the cut-off valve, the inflow valve comprising a second valve element having a second through-going fluid passage, the second valve element being movable into and between an open position in which a fluid flow from the intermediate-passage port to the outlet port is allowed via the second through-going fluid passage and a closed position in which fluid flow from the intermediate-passage port to the outlet port is prevented; and wherein the cut-off valve and the inflow valve each comprise a gliding port transition that is configured such that the first valve element and second valve element can be accelerated prior to reaching their respective open and closed positions, thereby enabling opening and closing of the cut-off valve and the inflow valve at a highest possible displacement speed of the respective first and second valve elements, the pulse-width-regulating valve further comprising a valve gear device that is configured to move at least one of the cut-off valve and the inflow valve into and between the respective open and closed positions, wherein the valve gear device is configured to move the cut-off valve at a first opening speed towards the open position, wherein the valve gear device is configured to move the cut-off valve at a first closing speed towards the closed position, wherein the first opening speed is greater than the first closing speed, and wherein the valve gear device is configured to move the inflow valve at a second opening speed towards the open position, wherein the valve gear device is configured to move the inflow valve at a second closing speed towards the closed position, wherein the second closing speed is greater than a second opening speed.

2. A pulse-width-regulating valve configured to regulate at least one of a fluid flow and a fluid pressure, the pulse-width-regulating valve comprising: a valve housing comprising an inlet port, an outlet port, and an intermediate-passage port disposed between the inlet port and the outlet port; a cut-off valve comprising a first valve element having a first through-going fluid passage, the first valve element being movable into and between an open position in which fluid flow from the inflow port to the intermediate-passage port is allowed via the first through-going fluid passage and a closed position in which fluid flow from the inflow port to the intermediate-passage port is prevented; an inflow valve connected in series with the cut-off valve, the inflow valve comprising a second valve element having a second through-going fluid passage, the second valve element being movable into and between an open position in which a fluid flow from the intermediate-passage port to the outlet port is allowed via the second through-going fluid passage and a closed position in which fluid flow from the intermediate-passage port to the outlet port is prevented; and wherein the cut-off valve and the inflow valve each comprise a gliding port transition that is configured such that the first valve element and second valve element can be accelerated prior to reaching their respective open and closed positions, thereby enabling opening and closing of the cut-off valve and the inflow valve at a highest possible displacement speed of the respective first and second valve elements, the pulse-width-regulating valve further comprising a driving flow channel formed through the first valve element, wherein the driving flow channel is in fluid communication with the second valve element when the first valve element is the closed position.

3. A pulse-width-regulating valve configured to regulate at least one of a fluid flow and a fluid pressure, the pulse-width-regulating valve comprising: a valve housing comprising an inlet port, an outlet port, and an intermediate-passage port disposed between the inlet port and the outlet port; a cut-off valve comprising a first valve element having a first through-going fluid passage, the first valve element being movable into and between an open position in which fluid flow from the inflow port to the intermediate-passage port is allowed via the first through-going fluid passage and a closed position in which fluid flow from the inflow port to the intermediate-passage port is prevented; an inflow valve connected in series with the cut-off valve, the inflow valve comprising a second valve element having a second through-going fluid passage, the second valve element being movable into and between an open position in which a fluid flow from the intermediate-passage port to the outlet port is allowed via the second through-going fluid passage and a closed position in which fluid flow from the intermediate-passage port to the outlet port is prevented; and wherein the cut-off valve and the inflow valve each comprise a gliding port transition that is configured such that the first valve element and second valve element can be accelerated prior to reaching their respective open and closed positions, thereby enabling opening and closing of the cut-off valve and the inflow valve at a highest possible displacement speed of the respective first and second valve elements, wherein the first and second valve elements comprise first and second end faces, respectively, that are perpendicular to respective center axes of the first and second valve elements, and further comprise valve axles that project through respective valve seals in the valve housing.

4. The pulse-width regulating valve according to claim 3, wherein the gliding port transition of the cut-off valve is defined by: the first valve element of the cut-off valve being further movable into a first starting position in which the fluid flow from the inlet port to the intermediate-passage port is prevented, wherein the open position is located between the first starting position and the closed position, and the first valve element of the cut-off valve being further movable into a second starting position in which the fluid flow from the inlet port to the intermediate-passage port is prevented, wherein the closed position is located between the second starting position and the open position.

5. The pulse-width regulating valve according to claim 3, wherein the gliding port transition of the inflow valve is defined by: the second valve element of the inflow valve being movable into a first starting position in which the fluid flow from the intermediate-passage port to the outlet port is prevented, wherein the open position is located between the first starting position and the closed position; and the second valve element of the inflow valve being movable into a second starting position in which fluid flow from the intermediate-passage port to the outlet port is prevented, wherein the closed position is located between the second inflow valve staring position and the open position.

6. The pulse-width-regulating valve according to claim 3, wherein at least one of the first and second valve elements is axially displaceable.

7. The pulse-width-regulating valve according to claim 3, wherein at least one of the first and second valve elements is rotatable.

8. The pulse-width-regulating valve according to claim 3, wherein at least one of the inflow valve and the cut-off valve are selected from the group consisting of a shell valve, a slide valve, and a rotating valve.

9. The pulse-width-regulating valve according to claim 3, further comprising a valve gear device that is configured to move at least one of the cut-off valve and the inflow valve into and between the respective open and closed positions.

10. The pulse-width-regulating valve according to claim 9, wherein the valve gear device is configured to move the cut-off valve at a first opening speed towards the open position, wherein the valve gear device is configured to move the cut-off valve at a first closing speed towards the closed position, wherein the first opening speed is greater than the first closing speed, and wherein the valve gear device is configured to move the inflow valve at a second opening speed towards the open position, wherein the valve gear device is configured to move the inflow valve at a second closing speed towards the closed position, wherein the second closing speed is greater than a second opening speed.

11. The pulse-width regulating valve according to claim 9, wherein the valve gear device is configured to accelerate the first and second valve elements in advance of transitional phases during which the first and second valve elements are being moved into or out of the open and closed positions.

12. The pulse-width-regulating valve according to claim 9, wherein the valve gear device comprises at least one actuator selected from the group consisting of a mechanical valve actuator, a hydraulic valve actuator, a pneumatic valve actuator, an electromechanical valve actuator, an electrohydraulic valve actuator, and an electro-pneumatic valve actuator.

13. The pulse-width-regulating valve according to claim 9, further comprising a valve synchronizer that is operably connected to the valve gear device.

14. The pulse-width-regulating valve according to claim 13, wherein the valve synchronizer is configured to adjust an operational phase relationship between opening and closing movements of the inflow and cut-off valves.

15. The pulse-width-regulating valve according to claim 3, wherein the valve housing comprises at least one leak port.

16. The pulse-width-regulating valve according to claim 3, wherein at least one of the first and second valve elements has an aperture, wherein at least one of the inlet port, the outlet port and the intermediate-passage port has an aperture that is sized differently than the aperture of the at least one of the first and second valve elements so as to achieve a valve opening over an extended area of the at least one of the first and second valve elements.

17. The pulse-width-regulating valve according to claim 3, further comprising a driving flow channel formed through the first valve element, wherein the driving flow channel is in fluid communication with the second valve element when the first valve element is the closed position.

18. The pulse-width-regulating valve according to 3, wherein the first and second end faces define axial-pressure faces having equal dimensions.

19. A pulse-width-regulating valve configured to regulate at least one of a fluid flow and a fluid pressure, the pulse-width-regulating valve comprising: a valve housing comprising an inlet port, an outlet port, and an intermediate-passage port disposed between the inlet port and the outlet port; a cut-off valve comprising a first valve element having a first through-going fluid passage, the first valve element being movable into and between an open position in which fluid flow from the inflow port to the intermediate-passage port is allowed via the first through-going fluid passage and a closed position in which fluid flow from the inflow port to the intermediate-passage port is prevented; an inflow valve connected in series with the cut-off valve, the inflow valve comprising a second valve element having a second through-going fluid passage, the second valve element being movable into and between an open position in which a fluid flow from the intermediate-passage port to the outlet port is allowed via the second through-going fluid passage and a closed position in which fluid flow from the intermediate-passage port to the outlet port is prevented; and wherein the cut-off valve and the inflow valve each comprise a gliding port transition that is configured such that the first valve element and second valve element can be accelerated prior to reaching their respective open and closed positions, thereby enabling opening and closing of the cut-off valve and the inflow valve at a highest possible displacement speed of the respective first and second valve elements, wherein the first and second valve elements comprise first and second end faces, respectively, that are perpendicular to respective center axes of the first and second valve elements, and further comprise valve axles that project through respective valve seals in the valve housing, and wherein the first and second end faces define axial-pressure faces having equal dimensions.

20. A pulse-width-regulating valve configured to regulate at least one of a fluid flow and a fluid pressure, the pulse-width-regulating valve comprising: a valve housing comprising an inlet port, an outlet port, and an intermediate-passage port disposed between the inlet port and the outlet port; a cut-off valve comprising a first valve element having a first through-going fluid passage, the first valve element being movable into and between an open position in which fluid flow from the inflow port to the intermediate-passage port is allowed via the first through-going fluid passage and a closed position in which fluid flow from the inflow port to the intermediate-passage port is prevented; an inflow valve connected in series with the cut-off valve, the inflow valve comprising a second valve element having a second through-going fluid passage, the second valve element being movable into and between an open position in which a fluid flow from the intermediate-passage port to the outlet port is allowed via the second through-going fluid passage and a closed position in which fluid flow from the intermediate-passage port to the outlet port is prevented; and wherein the cut-off valve and the inflow valve each comprise a gliding port transition that is configured such that the first valve element and second valve element can be accelerated prior to reaching their respective open and closed positions, thereby enabling opening and closing of the cut-off valve and the inflow valve at a highest possible displacement speed of the respective first and second valve elements; wherein the first and second valve elements comprise first and second end faces, respectively, that are perpendicular to respective center axes of the first and second valve elements, and further comprise valve axles that project through respective valve seals in the valve housing, and the pulse-width-regulating valve further comprising a preloading element that axially preloads the first and second valve elements so as to provide a compressive force against the first and second end faces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which:

(2) FIG. 1 shows a function diagram for a pulse-width-regulated device, in which the pulse-width period is shown as 15, 30, 45, 60, 75 and 90%, respectively;

(3) FIG. 2 shows a principle drawing of a pulse-width-regulating valve in which the valve elements are connected to a first embodiment of a valve gear;

(4) FIG. 3 shows a principle drawing of a pulse-width-regulating valve with a second embodiment of a valve gear;

(5) FIG. 4 shows a partially cut away view of a pulse-width-regulating valve based on slide or piston valves;

(6) FIG. 5 shows a function diagram for a pulse-width-regulating valve with associated phase-shift curves;

(7) FIG. 6 shows diagrammatically a flow sequence of a pulse-width-regulating valve used as an injector;

(8) FIG. 7 shows a principle drawing of the mechanical elements of a pulse-width-regulating valve;

(9) FIG. 8 shows a principle drawing corresponding to the one shown in FIG. 7, but in which one element also has a driving-flow channel;

(10) FIG. 9 shows a principle drawing of the function of the pulse-width-regulating valve during the operation over two full cycles;

(11) FIG. 10 shows a principle drawing of the pulse-width-regulating valve used for a thermodynamic engine, and more particularly a piston engine;

(12) FIG. 11 shows a principle drawing of the pulse-width-regulating valve used for a multiple-expansion engine, and in this case, a compound engine;

(13) FIG. 12 shows a typical PV diagram for a steam engine or equivalents thereto;

(14) FIG. 13 shows a sketch of the pulse-width-regulating valve with a driving-flow port (leak-flow port)

(15) FIG. 14 shows the pulse-width-regulating valve according to FIG. 13 in which a fluid flow is carried into a cyclone;

(16) FIG. 15 shows the pulse-width-regulating valve of FIG. 13 used as a working-fluid injector at a thermodynamic engine with an internal heat exchanger, wherein the working fluid may be injected cyclonically into the work chamber of the thermodynamic engine;

(17) FIG. 16a shows a radial section through a pulse-width-regulating valve implemented with rotatable valve elements;

(18) FIG. 16b shows an axial section through the valve according to FIG. 16a, but in which the valve elements have been rotated 90 degrees in relation to the representation in FIG. 16a; and

(19) FIGS. 17a and 17b show principle drawings of different embodiments of rotation mechanisms for the rotatable valve elements.

DETAILED DESCRIPTION OF THE DRAWINGS

(20) In the function diagrams of FIGS. 1, 5 and 9, the references a and b indicate, respectively, an open and a closed pulse-width-modulated flow circuit. In the phase-shift curves in FIGS. 5 and 9, the references O and C indicate, respectively, an open and a closed valve element. D indicates the relationship between the time in the open state and the time in the closed state of the valve, also called a duty cycle.

(21) q, in FIGS. 2, 3, 4, 6, 10 and 11, indicates a fluid flow.

(22) , in FIG. 6, indicates an angle of rotation for a crank shaft, valve drive shaft or equivalents thereto.

(23) m, in FIG. 15, indicates a specific amount of working fluid, Q.sub.i1 indicates the specific supply of thermal energy to the working fluid from an external heat source, and Q.sub.i2 indicates the specific supply of thermal energy to the working fluid from an internal heat exchanger in the expansion chamber.

(24) Reference is first made to FIG. 2, in which a pulse-width-regulating valve 1 includes a valve unit 10 provided with first and second valve elements 10a, 10b. A valve gear 2 is arranged for the valve unit 10. The first valve element 10a is also called a cut-off valve element as it is it used to cut off the supply of the fluid flow q. The second valve element 10b is also called an inflow valve element as it is used to open to the supply of the fluid flow q to a downstream consumer, for example a heat engine 100 (see FIGS. 10, 11 and 15). The cut-off valve element 10a and the inflow valve element 10b may incidentally be arranged in the opposite order in terms of fluid flow. The valve gear 2 includes first and second valve actuators 20, 20 and is shown here as a double camshaft, a driven valve drive shaft 2a providing synchronized rotation of first and second camshafts 22a, 22b, and a valve synchronizer 23 providing for the valve actuators 20, 20 to work with a desired phase shift. The valve actuators 20, 20 are connected to the valve elements 10a, 10b by means of a valve-actuator connection 20a each, for example a rod.

(25) In FIG. 3, the valve gear 2 is shown with valve actuators 20, 20 in the form of electromechanical, hydraulic or pneumatic actuators synchronized and phase-shifted by means of a valve synchronizer 23. Servos could typically also be used as valve actuators 20, 20.

(26) Reference is now made to FIG. 4, in which a pulse-width-regulating valve 1 is shown in greater detail with two valve elements 10a, 10b of a slide type arranged in, respectively, a first and a second portion 19a of a valve housing 19. The valve elements 10a, 10b are connected to a valve gear 2 as described above. The valve housing 19 includes an inlet port 12 connected to the first valve element 10a, an outlet port 13 connected to the second valve element 10b and an intermediate-passage port 14 forming a connection between the first and the second portion 19a, 19b of the valve housing 19. The inlet, outlet and intermediate-passage ports 12, 13, 14 are closed and opened by the displacement of the valve elements 10a, 10b. The valve elements 10a, 10b are provided with fluid passages 11a and 11b, respectively.

(27) The valve housing 19 is also provided with leak ports 16 to prevent pressure build-up due to unintentional leakage past the valve elements 10a, 10b.

(28) It is worth noting that the outlet port 13 in this embodiment has a large cross section in relation to the fluid passages 11a, 11b of the valve elements 10a, 10b. It is also worth noting that the valve elements 10a, 10b switches between the open and closed positions when exhibiting the highest displacement speed. This reduces the flow losses connected with opening and closing.

(29) FIG. 5 shows the effect of different phase shifts between the valve elements 10a, 10b. A displacement curve 9a for the cut-off valve element 10a is shown in a broken line, and a displacement curve 9b for the inflow valve element 10b is shown in a solid line. A resulting valve-function curve 8 shows the switching of the pulse-width-regulating valve 1 between the open and closed states a and b, respectively. Curves are shown for duty cycles of 35% and 6%.

(30) FIG. 6 shows a resulting valve-function curve 8 for a pulse-width-regulating valve 1, in which the cut-off valve element 10a is provided with a driving-flow channel which provides a driving fluid flow q.sub.2 as long as the inflow valve element 10b is in its open position. The driving-flow channel and the effect thereof are described below. As long as both the cut-off valve element 10a and the inflow valve element 10b are open, the valve 1 outputs a main fluid flow q.sub.1. Correspondingly, the effect of a driving-fluid channel in the inflow valve element 10b will provide a driving fluid flow q.sub.2 which is followed by the main fluid flow q.sub.1.

(31) Reference is now made to FIG. 7, which shows a principle drawing of the pulse-width-regulating valve 1, and to FIG. 8, which shows its equivalent, but in which the cut-off valve element 10a is provided with a driving-flow channel 11c. It may be favourable to provide a certain amount of convection/forced flow in an expansion chamber provided with a heat exchanger. This may be provided by the use of the driving-flow channel 11c which is in fluid communication with said expansion chamber. This principle is also shown schematically in the FIGS. 13 and 14, in which the driving-flow channel 11c includes a driving-flow port 15, which is provided with a throttling. The driving-flow channel 11c may be routed to a fluid receiver, shown schematically as a cyclone 101 in FIG. 14, in many different ways, for example via the inflow valve element 10b or in the material of the valve housing 19. The driving-flow port 11c may be formed in the cut-off valve element 10a itself, as it is indicated in FIG. 8, or as a separate port into an intermediate valve volume (not shown).

(32) FIG. 9 shows the cut-off and inflow valve elements 10a and 10b, respectively, in different positions in the course of two complete duty cycles with corresponding displacement curves 9a, 9b and the valve function curve 8 for a duty cycle of 35%.

(33) FIG. 10 shows an exemplary embodiment of a pulse-width-regulating valve 1 arranged for a piston engine 100.

(34) FIG. 11 correspondingly shows first and second pulse-width-regulating valves 1, 1 arranged for first and second expansion chambers 101, 102 in a piston engine 100 (multiple-expansion engine).

(35) FIG. 12 shows a typical PV diagram 1100 for a steam engine or equivalents thereto, in which 1110 indicates a work stroke, and in which 1110a indicates an inflow course, 1110a indicates the effect of an improved inflow course which can be achieved by means of the invention, 1110b shows a near-adiabatic expansion course and 1110c indicates the start of outflow (exhaust). Further, 1110d indicates an outflow course, 1110e a pre-compression and 1110f an initial inflow course/preliminary inflow.

(36) FIG. 15 shows how, in principle, a pulse-width-regulating valve 1 is arranged in a working-fluid circuit in a heat engine.

(37) Reference is now made to FIGS. 16a and 16b in which the pulse-width-regulating valve 1 is provided with rotatable valve elements 10a, 10b where the fluid passages 11a and 11b, respectively, extend in a radial direction with apertures 11a and 11b, respectively, decreasing towards the centre axis of the valve element. The aperture of the inlet port 12 is indicated by the reference numeral 12. The aperture of the intermediate-passage port 14 is indicated by the reference numeral 14. The aperture of the outlet port 13 is indicated by the reference numeral 13.

(38) FIGS. 17a and 17b show different principles for converting the oscillating motion of a valve actuator 20 via a valve-actuator connection 20a into a rotary motion of the valve elements 10a, 10b, shown here with a rotating camshaft 22a, 22b of a kind known per se; in a first embodiment (see FIG. 17a), by transmitting the oscillating motion of a push rod 20a via a pitch-rack portion 20a to a toothed wheel 103 arranged on one valve stem 10c, possibly 10d, of the valve element 10a, 10b, and in a second embodiment (see FIG. 17b), by transmitting the oscillating motion of a push rod 20a to a valve arm 103 arranged on one valve stem 10c, possibly 10d, of the valve element 10a, 10b.

(39) A valve synchronizer 23, which is shown schematically, is arranged for the valve gear 2 in such a way that the rotation of the camshafts 22a, 22b can be phase-shifted.

(40) The symmetry of the valve elements 10a, 10b, that is to say the fact that both ends of the valve elements 10a, 10b form the valve stems 10c, 10d, each projecting through a respective valve seal 18, gives a balanced axial pressure load on the valve elements 10a, 10b, by the very fact of first and second end faces 104, 104 facing the valve seals 18 being equally large. Thereby the frictional forces between the valve element 10a, 10b and the valve seals 18 are reduced. Little power is thereby required to move the valve elements 10a, 10b. The valve 1 will normally be provided with end plates (not shown) that hold the valve seals 18 in place. Also, more than one valve seal 18 may be arranged for each valve stem 10c, 10d, and in that case, it will be natural for the valve 1 to be provided with a corresponding number of extra end plates (not shown).

(41) The switching of the valve elements 10a, 10b between the open and closed positions with an adjustable phase shift, provides a fully variable valve function from a minimum level determined by the intermediate valve volume formed by the intermediate-passage port 14, which will constantly be filled with fluid.

(42) Even though, in the above embodiments, rotating valve elements have been described and shown, the described effect will be achieved also by the use of slide valves that exhibit their open positions between their end positions.

(43) The use of valve element bushings 17 in the valve housing 19 may be of vital importance to the function and lifetime of the valve 1, which, for this type of device, should be at least 10 000 hours.

(44) It may be an advantage to use an accumulator (not shown) right in front of the first valve unit 1a, especially in water injection, but it may also be important in gas injection, that is to say when the valve 1 is used in ORC (Organic Rankine Cycle) engines. The accumulator reduces the risk of pressure peaks when liquid is injected, and it reduces the pressure drop during the initial injection. A preferred type of accumulator is a metal-bellows accumulator, which can withstand high temperatures, for example 180 C. or more.

(45) The valve elements 10a, 10b advantageously exhibit a relatively large diameter, typically about 24 mm when the circumferential width of the valve element opening 11a, 11b is about 6 mm. A large diameter entails a greater circumferential speed than a small diameter at a given rotation speed and a high switching speed is thereby achieved when the valve goes from open to dosed and vice versa, which is important to avoid large pressure drops and thereby losses in the switching phases. The diameter of the valve stems 10c, 10d, on the other hand, is relatively small, typically about 8-10 mm for a valve element diameter of 24 mm.

(46) The valve element openings 11a, 11b preferably exhibit a small width (that is to say the extent in the moving direction of the valve element 10a, 10b) in relation to its height, for example in the range of 2/10-4/10. In a valve element 10a, 10b of the dimensions mentioned in the preceding paragraph, the width/height ratio is typically about 4/14. This provides faster opening or closing than with a large width.

(47) Even though, in the exemplary embodiment, a valve gear 2 with a camshaft 22 (see FIGS. 17a and 17b) is shown, a fully rotating, mechanical valve gear may also be usable for practical purposes. A fully rotating valve gear has the advantage of being very simple and inexpensive. A valve gear 2 with a camshaft 22, on the other hand, gives the advantage of the speed profile of the valve being manipulatable within certain frames. With a cam gear, great speed can be achieved in the switching phase, that is to say when the valve element 10a, 10b goes from open to closed or vice versa. At the same time, it could be approximately at rest when it has reached the fully open position. This may have a favourable effect on the pressure drop across the valve 1, thereby giving reduced losses. For a fully rotating valve gear it is correspondingly conceivable that the ports 12, 13 of the valve 1 are overdimensioned so that the pressure drop will, in any case, be relatively low, and in that case, a good, but still simple compromise may be achieved.

(48) In liquid injection, a situation will arise in the intermediate valve volume, represented by the intermediate-passage port 14, wherein the inflow valve 1b is closed and the cut-off valve 1a opens and the intermediate valve volume fills with liquid. This could lead to undesired pressure peaks (cavitation). A soft opening of the cut-off valve 1a is therefore beneficial, which may be implemented through a cam gear, but correspondingly, the closing of the cut-off valve 1a should be fast to reduce the throttling loss. This combination may be satisfied by means of an adapted cam profile. This effect is difficult to achieve with a fully rotating valve gear with fixed speed.

(49) The elements of the valve 1, that is to say the elements 10a, 10b, the valve element bushings 17 and so on, should have nearly the same temperature as the maximum temperature of the working fluid in order that no power be lost through the injector. This is also favourable in order to reduce the risk of increased friction, possibly seize-up, between moving and static parts. This may be solved by good thermal connection to an existing heat exchanger being established, or possibly by the valve housing 19 being provided with channels for the circulation of a heated thermofluid. The valve housing 19 may possibly be insulated.

(50) The rotatable valve elements 10a, 10b according to the exemplary embodiment shown in FIG. 16b are preloaded in the axial direction to determine the axial position of the valve elements 10a, 10b. Preloading elements 18b, typically in the form of O-rings, are arranged between the valve seal 18 and a slide disc 18a formed out of a high-temperature-resistant plastic material which minimizes the frictional forces that arise between the valve element 10a, 10b and the slide disc 18a in consequence of the preloading.

(51) The pulse-width-regulating valve 1 is in fluid communication with one or more work chambers 101, 102 in a heat engine 100, or more generally a displacement engine, as is shown in the FIGS. 10 and 11 among others. The displacement engine may typically be a piston engine, a scroll engine (spiral engine), a wing engine, a gear engine or a screw engine. For a person skilled in the art, it will be obvious that by a piston engine is meant a hydraulic cylinder as well.