Injection device for a compressed-air engine, compressed-air engine provided with such a device and hybrid drive train comprising such an engine

Abstract

The invention relates to a mechanical compressed-air injection device for a compressed-air piston engine having optimized consumption and power. The device comprises a compressed-air intake valve (S) comprising a first part (20) and a second part (30) which are mounted so as to slide relative to one another in the direction of movement of the piston, the movement of the first part (20) being controlled mechanically by the piston, and the injection device also comprising a means (40) for temporarily retaining the second part (30) relative to the first part (20) so as to cause the movements of the second part (30) of the valve and of the piston (1) to become desynchronized.

Description

Injection device for compressed air engine, compressed air engine equipped with such a device and hybrid drive train comprising such an engine.

[0001] The present invention relates to a compressed air engine with low air consumption, and a compressed air injection cycle in this engine, designed according to the known principle of so-called "two-stroke" or "four-stroke" internal combustion engines of "diesel" engines.

[0002] It also relates to an injection device for such an engine, a cylinder head incorporating this injection device and a hybrid powertrain comprising such an engine.

[0003] The invention finds a particularly important, although not exclusive, application in the field of motorization of land vehicles (such as cars or utility vehicles) or marine vehicles (such as boats), but also for motorization used in industry or for craft activities such as, for example, generator sets.

[0004] A particularly interesting application of the motor according to the present invention, given solely by way of non-limiting example, is found in the integration of this motor in a drive chain comprising an electric generator engaged with the shaft of the motor, the generator being connected to an electric motor.

[0005] Indeed, there are many powertrain solutions based on thermal engines, electric motors or a combination of the two (called hybrid powertrain).

[0006] So-called "thermal" vehicles require the use of polluting fossil fuels, which has led authorities in many countries to favor other, less polluting types of powertrains. Their main advantage comes from their autonomy and the speed at which the fuel tank can be refilled.

[0007] So-called "electric" vehicles have a drive train composed of a power battery capable of supplying the electric motor(s) capable of driving a transmission connected to a moving part (the wheels of a car or the propeller of a boat, for example).

[0008] A power battery is distinguished from a vehicle's starter battery by its power, capacity, and ability to drive a vehicle's wheels or propeller.

[0009] The power batteries used in electric vehicles are currently lithium-ion batteries, because only this type of battery provides the power and autonomy suitable for this use.

[0010] The major disadvantage of the electric drive train lies precisely in the battery.

[0011] Indeed, its manufacture and end of life are ecologically problematic: lithium reserves are theoretically insufficient to equip all the vehicles in the world, and the recycling process is currently unknown.

[0012] In addition, lithium-ion batteries have a definite tendency to heat up during charging, or even during use, and many incidents have been recorded in which batteries have caught fire due to this overheating.

[0013] Hybrid powertrains have also been proposed, in which a thermal engine either assists the electric motor, recharges the power battery, or both.

[0014] These hybrid vehicles, however, have all the drawbacks of both technologies: pollution, risk of fire, complex or even impossible recycling, etc.

[0015] There is therefore a need to offer an engine and a drive train that reduce the pollution generated and operating risks.

[0016] A classic two-stroke air-powered piston engine is already known, and illustrated in.

[0017] The engine comprises a cylinder block A comprising at least one piston 1 connected to a drive shaft 2 by means of a connecting rod 3 rotatably attached to a counterweight 4. The piston 1 is mounted to move in translation (arrow F1) in a compression / extension chamber 5, the upper end of which is closed by a cylinder head B. In the lower part, the chamber 5 comprises an opening 6 for admitting outside air (arrow F2), as well as a channel 7 for conducting outside air (arrows F3 and F4) opening into the chamber 5 above the piston 1 when the latter is at bottom dead center. The chamber 5 also comprises an exhaust outlet 12 for discharging the expanded compressed air when the piston descends and is located close to its bottom dead center.

[0018] In the upper part, hermetically closing the chamber 5, the cylinder head B comprises at least one compressed air intake valve 8 from (arrow F5) a high-pressure compressed air reserve 9 via a pressure reducer 10 (aimed at reducing the air pressure from 300 bars coming from the reserve to a pressure of 30 to 50 bars at the outlet towards the compressed air intake chamber 11 located upstream of the intake valve 8). The compressed air intake valve 8 comprises a valve stem 8a, movable in translation (arrow F6) relative to the cylinder head B, and provided with a valve head 8b carrying a contact surface 8c with a valve seat 8d located in the cylinder head B.

[0019] The valve head 8b protrudes into the chamber 5 by a determined length, so that the piston 1 pushes the valve stem upwards. However, for the injected compressed air volume to be sufficient to generate the required engine work, this opening must last a sufficiently long time. Consequently, the valve head must protrude into the chamber by a significant length which, in turn, controls the opening of the valve well before the top dead center of the piston.

[0020] Furthermore, in this type of engine, a volume of outside air, taken at atmospheric pressure when the piston is in the low position (bottom dead center or BDC), is compressed by the piston in the piston chamber when the latter rises. The compressed air heats the walls of the chamber. It is then possible to inject compressed air from the compressed air reserve into this heated chamber via the intake valve. The compressed air then expands due to the pressure difference and the high temperature of the chamber, which forcibly pushes the piston downwards, generating mechanical work and allowing the expanded air to be expelled. Then the cycle resumes: intake of outside air, compression of the air in the chamber by the rising piston and heating of the chamber, injection of compressed air into the chamber, generation of mechanical work, expulsion of the air to the outside.

[0021] By heating chamber 5, this device therefore improves the efficiency of the compressed air by promoting greater and faster expansion, but it still has many defects, particularly when the piston rises.

[0022] Indeed, a first problem lies in the fact that depending on the adiabatic compression ratio of the air, the temperature of the cylinder, when the piston is in the upper position, can exceed 600 degrees Celsius and the pressure several tens of bars. The external air thus compressed therefore opposes the rise of the piston in the last millimeters, so that the engine loses power.

[0023] Furthermore, compressed air must always be injected at a pressure higher than that of the compressed air in the piston chamber, to allow for expansion and engine work. The compression ratio of the air compressed by the piston, coming from outside, therefore defines the minimum pressure to be injected into the cylinder, which therefore does not allow for fine control, and therefore optimization, of air consumption.

[0024] Thus, a significant part of the piston's rise is opposed by the thrust of the valve and by the pressure of the ambient air compressed by the piston.

[0025] This is all the more true since a compressed air engine differs from a combustion engine in particular by a much larger volume of injected air than the volume of injected fuel, to generate comparable engine work. It is therefore necessary to play on the air passage section, but also on the duration of opening of the intake valve in order to ensure the injection of a sufficient volume of compressed air compatible with the desired use.

[0026] For comparison, with a comparable opening time, the diameter of diesel injectors is 0.1 millimeters, while the opening of the passage for compressed air is about 7 millimeters, i.e. seventy times larger.

[0027] For this reason, in the prior art, it is necessary to start the air injection before the piston has reached its top dead center.

[0028] We therefore understand that this compressed air added to the external air already compressed by the piston very strongly opposes the end of the piston's rise, which causes a loss of engine power.

[0029] A second problem is that the valve head is struck by the piston at a time when it is at a very high speed since this happens well before the top dead center of the piston, which leads to rapid fatigue of the parts and therefore unsatisfactory reliability of the engine.

[0030] Document FR3115313 attempts to solve this second problem. In particular, it describes a modified compressed air injection valve, in which the valve is integral with the piston (no impact of the parts) and is provided with a groove of a determined length to allow the air to pass sequentially.

[0031] However, this groove must be of significant length to allow the injection of sufficient compressed air to generate the required engine work. Consequently, air begins to enter the chamber well before the piston has reached top dead center. This does not solve, or even amplifies, the first problem.

[0032] This is why it has already been proposed to add an ejection valve allowing the compressed air from the piston to escape just before injecting compressed air from the reserve into the chamber, in order to reduce the pressure in the chamber. It has also been proposed to circulate this ejected air in a volume surrounding the chamber to further heat the chamber, but this arrangement makes the engine design very complex, without bringing a notable improvement. In addition, the opening of the intake and ejection valves is controlled by two camshafts, as in thermal engines, which makes the design complex and increases the weight of the assembly.

[0033] The objective of the present invention is therefore to propose a mechanical solution making it possible to improve the reliability of the engine.

[0034] Another objective of the present invention is to propose a compressed air engine having lower consumption for equal generated motor power, so as to increase the autonomy and efficiency of the device equipped with said engine: vehicle or generator set.

[0035] In other words, one of the objectives of the invention is to increase the efficiency of the engine, that is to say to increase the driving power for an identical quantity of injected air, or to reduce the quantity of injected air for an identical driving power.

[0036] However, the inventor had the idea that an injection which would take place closer to top dead center would make it possible to reduce the negative work consumed by the piston rising.

[0037] The idea behind the invention is to provide delayed air injection, while ensuring a sufficient volume of injected air to obtain a driving power compatible with the desired use. This will improve engine efficiency.

[0038] The present invention provides a mechanical type solution, in the sense that it does not require any sensor or electronic control of the opening of the air intake valve. This solution has the advantages of low or even non-existent power consumption, the absence of a sensor and therefore high reliability.

[0039] An engine covered by the invention is similar to that illustrated in, but is distinguished therefrom by the particular design of the compressed air injection device.

[0040] Thus, the invention provides a mechanical compressed air injection device designed to equip a compressed air engine comprising at least one piston intended to move in a chamber, said device comprising at least one compressed air intake valve, each valve being adapted to operate with a piston of the engine when the device is in the position of use in the engine, this valve comprising a first part and a second part mounted to slide in the direction of movement of the piston, the movement of the first part being, in operation, mechanically controlled by the piston, characterized in that the first part and the second part are mounted to slide relative to each other in the direction of movement of the piston and in that the injection device further comprising, for each valve, a means for temporarily retaining the second part relative to the first part so as to impose,in operation, a delayed, i.e. desynchronized, movement between the second part of the valve and the piston.

[0041] More specifically, the first part of the valve of the compressed air injection device according to the invention has its movement controlled solely by the piston, while the second part, which surrounds the first part so that the first part can slide inside the second part, has its movement controlled by the piston and by the temporary retaining means.

[0042] In particular and / or advantageous embodiments, this device may include one and / or other of the following characteristics:

[0043] The first part comprises a rod and a support washer and the second part comprises: * a chamber provided with a bottom and a washer seat, in which the first part slides, and * an end provided with a valve head intended to cooperate with a valve seat carried by a cylinder head of the engine in the position of use;

[0044] The temporary retaining means consists of a spring, the first part comprising the support washer at its end intended to be arranged opposite the piston, the spring extending between the bottom of the chamber of the second part and the support washer of the first part, the stem of the first part projecting by a determined length L2 from the end of the valve head of the second part when the support washer is in contact with the washer seat.

[0045] The end of the valve head protrudes by a non-zero length L1 into the piston chamber when the device is in the operating position in the engine and the valve is in the closed position.

[0046] The valve head has a truncated cone shape.

[0047] The invention also relates to a compressed air engine cylinder head provided with an injection device according to the invention, the cylinder head being shaped to fit an existing compressed air engine.

[0048] The invention also relates to a compressed air engine incorporating a cylinder head according to the invention.

[0049] The invention also relates to a hybrid powertrain intended to equip a vehicle comprising a high-pressure compressed air reservoir connected to a compressed air piston engine according to the invention engaged with an electric generator for generating electricity when it is driven by the compressed air piston engine, the electric generator being connected to at least one electric motor connected to a transmission engaged with a moving member of the vehicle.

[0050] Preferably, the generator and said at least one electric motor are connected via a relay electrical reserve with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh / kg of vehicle).

[0051] Preferably, the drive chain further comprises an accelerator control movable between a stop position and a maximum acceleration position and connected to an electronic control circuit comprising a controller programmed to power the electric motor from the relay electrical reserve as a function of a signal captured by at least one sensor fitted to the vehicle.

[0052] The invention finally relates to a generator set comprising or intended to be associated with a high-pressure compressed air tank. The generator set comprises a compressed air piston engine according to the invention engaged with an electric generator to generate electricity when driven by the compressed air piston engine.

[0053] Thus, the invention relates to a compressed air engine comprising:– an engine block comprising at least one cylinder having a chamber and a piston, said piston being mounted to move in translation in said chamber, and– a cylinder head associated with the engine block and capable of closing the or each chamber, the cylinder head comprising a mechanical compressed air injection device comprising at least one compressed air intake valve (S) opening into the or each chamber, such that each valve is adapted to operate with a piston of the engine when the device is in the position of use in the engine, this valve comprising a first part and a second part mounted to slide in the direction of movement of the piston, the movement of the first part being, in operation, mechanically controlled by the piston,characterized in that the first part and the second part are mounted to slide relative to each other in the direction of movement of the piston and in that the injection device also comprises, for each valve, a means for temporarily retaining the second part relative to the first part so as to impose, in operation, a desynchronized movement between the second part of the valve and the piston.,

[0054] In particular and / or advantageous modes, this engine may include one and / or other of the following characteristics:

[0055] The movement of the first part of the valve is controlled only by the piston, while the second part surrounds the first part so that the first part can slide inside the second part.

[0056] The first part comprises a stem and a support washer and the second part comprises:* a chamber provided with a bottom and a washer seat, in which the first part slides, and* an end provided with a valve head intended to cooperate with a valve seat carried by a cylinder head of the engine in the position of use;

[0057] The temporary retaining means consists of a spring, the first part comprising the support washer at its end intended to be arranged opposite the piston, the spring extending between the bottom of the chamber of the second part and the support washer of the first part, the stem of the first part projecting by a determined length L2 from the end of the valve head of the second part when the support washer is in contact with the washer seat.

[0058] The end of the valve head protrudes by a non-zero length L1 into the piston chamber when the device is in the operating position in the engine and the valve is in the closed position.

[0059] The valve head has a truncated cone shape.

[0060] The invention also relates to a cylinder head designed to equip a compressed air engine according to the invention, provided with an injection device according to the invention.

[0061] The invention also relates to an injection device intended to equip a compressed air engine and / or a cylinder head according to the invention, this device comprising the characteristics previously described.

[0062] Thus, the injection device according to the invention comprises as many valves as pistons present in the engine equipped with the device and as many retaining means as valves.

[0063] The invention will be better understood and other aims, advantages and characteristics thereof will appear more clearly on reading the description which follows and which is made with reference to the appended drawings, in which:

[0064] is a sectional view of a conventional two-stroke air-powered engine which has been previously described;

[0065] is a sectional view of an embodiment of an injection device according to the invention, the device being in the closed position;

[0066] represents six sectional views of the injection device illustrated in, representing different stages 3a to 3f of the operating cycle of the engine and the injection device;

[0067] is a Clapeyron diagram of a conventional compressed air engine, shown in; and

[0068] is a Clapeyron diagram of a compressed air engine according to the invention, illustrated in.

[0069] Elements common to the different figures are designated by the same references.

[0070] It represents a compressed air engine with valve S in the closed position, while piston 1 is between top dead center and bottom dead center. Reference A designates the engine's cylinder block, reference B its cylinder head, and reference 5 the compression / extension chamber of the engine block or cylinder block in which piston 1 is mounted in translation.

[0071] The first part 20 of the valve according to the invention comprises a rod 21 and, at its end intended to be arranged opposite the piston 1, a support washer 22. The first part forms a pin and is slidably mounted in a second part 30. The latter therefore comprises a hollow body provided with a chamber 31 having side walls 310, a first chamber end closed by a bottom 311 and a second chamber end carrying a washer seat 312. This chamber forms a blind hole and is intended to receive the first part 20 of the valve in a sliding manner. The hollow body of the second part 30 also comprises an end provided with the valve head 32 and the surface 33 intended to be in contact with the valve seat 34 carried by the cylinder head B. The head 32 has a frustoconical shape and the seat 34 a complementary shape.

[0072] The end 35 of the valve head 32 of the second part protrudes by a first length L1 (see; taken between the cylinder head and the end of the second part in the piston chamber, or the end 35 of the head 32) into the piston chamber, so as to be pushed back by the piston when the latter rises, this length L1 being non-zero.

[0073] The means for temporarily retaining the second part relative to the first part is constituted by a spring 40 interposed between the support washer 22 of the first part and the bottom 311 of the chamber 31 of the second part.

[0074] Furthermore, the rod 21 of the first part protrudes from the end of the second part in the piston chamber (or from the end 35 of the head 32) by a second length L2 (see), in the low position or extended position of the first part, that is to say when the support washer 22 is in abutment against the washer seat 312, corresponding to the relaxed state of the spring, this length L2 being non-zero. The rod 21 can thus be pushed back by the piston, before the valve head 32, when the latter rises.

[0075] The kinetics are explained in Figures 3a to 3f of the, and the relative movements of the different parts will thus appear more clearly.

[0076] Figure 3a illustrates, like the, the valve S in the closed position at the start of the operating cycle.

[0077] Thus, in this first step, the second part 30 of the valve is in the low position B30, resting on the cylinder head B and the valve head 32 is in contact with the valve seat 34 by its contact surface 33. The first part 20 of the valve is in the low position B20 and the spring 40 is relaxed. The valve is closed and prevents the arrival of compressed air in the chamber 5.

[0078] Piston 1 rises in chamber 5 (arrow F7) while the ambient air contained in the chamber is compressed and rises in temperature.

[0079] In the second step illustrated in Figure 3b, the piston has come into contact with the rod 21 of the first part 20, which causes it to translate in the same direction of movement as the piston (arrow 7). The rod 21 slides (arrow F8) in the chamber 31 and then compresses the spring 40. The first part 20 is then in its high position H20.

[0080] At the end of this second stage, the rod 21 no longer protrudes from the valve head 32 (in the retracted position), while the second part 30 is still resting on the cylinder head and closes the air intake.

[0081] The air in chamber 5 is compressed and hot.

[0082] Figure 3c illustrates a third step in which the piston continues its upward translational movement (arrow F7) and then comes into contact with the valve head 32 of the second part 30 (it of course remains in contact with the rod 21).

[0083] The rod 21 is still in the retracted position in the second part 20 and the spring 40 is still compressed.

[0084] On the other hand, the head 32 is struck by the piston 1 and the part 30 lifts (arrow F9) from the seat 34 until the piston is at its top dead center, which places the valve in the partially open position.

[0085] The fourth step illustrated in Figure 3d shows that, with the rod 21 still resting against the piston, the upward movement of the head 32 of the second part continues (arrow F10) thanks to the relaxation of the spring 40, which places the second part 30 in the high position H30 in which the valve S is in the fully open position and allows the complete arrival of compressed air in the chamber 5. The valve head 32 is then completely lifted from its seat 33. In other words, the valve S is fully open (stroke equal to the sum of the overhang heights L1 and L2), which allows a passage section and a passage opening time sufficient to inject the volume of compressed air necessary to push the piston 1 towards its bottom dead center, generating the required engine work.

[0086] As illustrated in Figure 3d, the piston then begins its downward translational movement (arrow F11). The rod 21 and the valve head 32 can then descend (arrow F12) by gravity and by the pressure exerted upstream of the valve head by the compressed air until the head 32 is applied against the seat 33, as illustrated in Figure 3e.

[0087] The spring remains relaxed and the valve remains partially open as long as the rod 21 is in contact with the piston.

[0088] In Figure 3f, the piston 1 continues its downward movement (arrow F11) so that the rod 21 is no longer in contact with the piston 1. The valve head 32 is in position on the seat 34, the valve then being in the closed position and the compressed air supply being closed.

[0089] The piston continues its downward movement (arrow F11) to bottom dead center (BDC) then rises for a new cycle.

[0090] The foregoing description shows that the first part 20 provides control of the opening of the passage and guidance and is, from a functional point of view, similar to a valve stem.

[0091] Furthermore, the second part 30 of the valve acts as a shutter by cooperating with the valve seat 34 to close or open the passage, and is therefore, from a functional point of view, similar to a valve head.

[0092] It is understood that the spring 40 makes it possible to increase the axial displacement of the second part 30 beyond the position in which this second part would be if only the piston 1 pushed it back.

[0093] This additional displacement, obtained "late", that is to say after the piston has reached TDC, increases the section of the passage for the injection of compressed air, and ensures that a sufficient volume of compressed air is injected to obtain the desired engine work, even though this injection only occurs when piston 1 has actually reached top dead center.

[0094] In fact, the compressed air injection can be done as close as possible to the TDC of the piston. As a result, the injection device according to the invention loses little or no power when the piston rises.

[0095] In addition, the piston hits the valve head closest to its top dead center, at a time when its speed is lower, which reduces the stress on this part and therefore increases the reliability of the engine.

[0096] So with the same injected compressed air volume as a standard engine, the driving power is much higher, and the engine is subjected to less stress and fatigues less.

[0097] As a corollary, at equal engine power with a standard engine, the injection device according to the invention injects less compressed air, so that the engine is more economical and allows better autonomy with the same air tank.

[0098] We therefore understand that the ratio between the lengths L1 and L2 determines the section and the opening time of the air passage.

[0099] The person skilled in the art will adapt the lengths L1 and L2 to the performance required for the engine, between maximum power, maximum autonomy, or a balance between the two.

[0100] In an exemplary embodiment, the length L2 is 4.2 millimeters, and the length L1 is 2.2 millimeters.

[0101] For comparison, the length L1+L2 is similar to the length by which the valve head protrudes into chamber 5 of the.

[0102] In the embodiment, the valve head 32 carried by the second part only protrudes into the chamber 5 by 2.2 millimeters, which makes it possible to gain almost 47% of piston travel before contact with the valve head.

[0103] The resistance encountered during contact between the piston 1 and the rod 21 of the first part is negligible and essentially determined by the stiffness of the spring 40 and the weight of the second part 30.

[0104] In fact, the stiffness of the spring is determined according to this weight, so as to ensure the rise of the second part when the spring relaxes (figure 3d; the weight of the first part does not intervene since the latter is pressed against the piston. The force of the spring is therefore fully transmitted to the second part which rises). It should also be noted that the spring is calibrated according to the power range targeted by the applications of the engines in which the injection device is used.

[0105] The valve therefore opens with a delay compared to the prior art, since it occurs, for example, 2 millimeters further in the piston stroke, only when the piston 1 encounters the valve head 32 carried by the second part 30.

[0106] Similarly, the valve also closes with a delay compared to the prior art, since it only occurs when the piston is lower than the first part, and not when the piston is lower than the valve head carried by the second part.

[0107] By choosing the lengths L1 and L2 of the first and second parts extending into the piston chamber, the injection of an optimal volume of air is ensured, at an optimal position of the piston.

[0108] Once the L1-L2 dimensions are chosen, the injected volume remains constant.

[0109] Generally speaking, the different embodiments of the invention make it possible to generate 15 to 25% more mechanical work.

[0110] Thus, figures 4 and 5 illustrate the Clapeyron diagrams of a conventional device and of a device according to the invention.

[0111] More precisely, the illustrates the Clapeyron diagram of a classic piston engine, shown in. In this figure as in the, the Volume variable, classically used in a Clapeyron diagram, is replaced by the Height of the chamber between the cylinder head and the piston, since the section of the piston chamber is constant.

[0112] This diagram reads as follows:

[0113] At point 1, the piston is in the bottom position (BDC), so the chamber height is at its maximum. Outside air is admitted into the chamber at atmospheric pressure.

[0114] As the piston moves up, the height of the chamber decreases and the pressure of the air inside the chamber increases to reach point 2.

[0115] At this height, the piston meets the valve head, lifts it, and opens the valve. The injection of compressed air immediately increases the pressure to reach point 3. The piston continues to rise to top dead center, against the air pressure, so that the system consumes work from point 3 to point 3*. Then the piston begins to descend again, until the valve closes (passing from point 3* to point 3), generating work that compensates for the work consumed by the piston to reach its top dead center (passing from point 3 to point 3*). This compensation of work consumed / work created is symbolized in the figure by a horizontal line between point 3 and point 3* which illustrates zero work.

[0116] From point 3, the compressed air continues to expand, pushing back the piston and generating work (area under the curve corresponding to the integral of the curve P=f(H)). The height of the chamber therefore increases again and the pressure inside the chamber drops until the air escapes, at point 4, through the exhaust outlet 12 of the chamber (see).

[0117] The pressure therefore immediately decreases to atmospheric pressure (point 5). The piston drops further to its bottom dead center (point 1 of the diagram), allowing the admission of outside air for a new cycle towards point 2.

[0118] Illustrates the Clapeyron diagram of an engine with desynchronized mechanical injection according to the invention, illustrated in. This diagram reads as follows:

[0119] At point 1a, the piston is in the bottom position (BDC), so the chamber height is at its maximum. Outside air is admitted into the chamber at atmospheric pressure.

[0120] As the piston rises, the height of the chamber decreases and the pressure of the air in the chamber increases. As it rises, the piston encounters the first part 20 and pushes it upwards, which does not open the valve, but arms the desynchronization system by compressing the spring 40. The mass of the part 20 and the stiffness of the spring 40 are such that they do not impact the rise of the piston, which therefore consumes only very negligible work.

[0121] The piston therefore continues its rise until it meets the second part 30 at point 2a of the diagram.

[0122] At this height, the piston is very close to its top dead center and the valve is open. The height of point 2a is therefore greater than the height of point 2 in the diagram of the conventional device. The injection of compressed air immediately increases the pressure to reach point 3a*.

[0123] Then the piston begins to descend again until the valve closes when the second part presses against the valve seat 34 (point 3a). While the height of the piston in the chamber decreases, the passage from point 3a* to point 3a is made at constant compressed air pressure and equal to the compressed air pressure since the compressed air passage remains open thanks to the lifting of the second part relative to the piston thanks to the spring 40 and the first part 20 pressing against the piston, which generates mechanical work by pushing the piston back.

[0124] When the valve closes (point 3a), the compressed air expands, continuing to push the piston back and generate work. The height of the chamber therefore increases again and the pressure inside the chamber drops until the air escapes, at point 4a, through the chamber's exhaust outlet (identical to outlet 12 of the).

[0125] The pressure therefore immediately decreases to atmospheric pressure (point 5a). The piston drops further to its bottom dead center (point 1 of the diagram), allowing the admission of outside air for a new cycle towards point 2.

[0126] On the, the white surface W1 represents the common work of the conventional device and the desynchronized injection device according to the invention. The hatched surface W3 represents the additional work generated by the device according to the invention of the.

[0127] In the case of an injection system according to the invention, it is noted that the total work, W2=W1+W3, generated by a device according to the invention is 15 to 25% greater than the work W1 generated by a conventional device.

[0128] By shifting the start of the intake towards TDC (so we align points 2a and 3a*), we increase the work / power recoverable at the engine output, because the engine will work as a producer at constant pressure from TDC until the intake valve closes (point 3a* towards point 3a) before expanding the air from the intake valve closes (point 3a) until it passes the exhaust port (point 4a).

[0129] The whole process and device can be used for exhaust in a conventional cylinder.

[0130] The invention also relates to a cylinder head incorporating an injection device as described as well as a compressed air engine incorporating an injection device as described.

[0131] A particularly interesting application of the engine according to the invention is to integrate it into a hybrid powertrain intended to equip a vehicle comprising a high-pressure compressed air tank connected to a compressed air piston engine according to the invention engaged with an electric generator to generate electricity when it is driven by the air piston engine.

[0132] The vehicle also includes at least one electric motor connected to a transmission engaged with a moving member of the vehicle.

[0133] The generator and said at least one electric motor are connected via a relay electrical reserve with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh / kg of vehicle), i.e. much lower than a power battery conventionally used in electric vehicles.

[0134] The drive train further comprises an accelerator control movable between a stop position and a maximum acceleration position and connected to an electronic control circuit comprising a controller programmed to power the electric motor from the relay electrical reserve according to a signal captured by at least one sensor fitted to the vehicle.

[0135] Using a more efficient compressed air piston engine, i.e. one that consumes less air for equivalent power than a conventional compressed air engine, therefore presents an essential advantage for developing this type of hybrid powertrain.

[0136] It is therefore also possible to control the exhaust in the same way, with the same type of valve according to the invention, but positioned at the air exhaust outlet, for example in a 4-stroke cycle.

[0137] The injection devices (and exhaust devices when used at the exhaust outlet to control the exhaust) according to the invention have been described with a two-stroke engine.

[0138] It is of course possible to adapt them to a four-stroke engine.

Claims

Mechanical compressed air injection device designed to equip a compressed air engine comprising at least one piston (1) intended to move in a chamber (5), said device comprising at least one compressed air intake valve (S), each valve being adapted to operate with a piston of the engine when the device is in the position of use in the engine, this valve comprising a first part (20) and a second part (30) mounted to slide in the direction of movement of the piston, the movement of the first part (20) being, in operation, mechanically controlled by the piston, characterized in that the first part (20) and the second part (30) are mounted to slide relative to each other in the direction of movement of the piston and in that the injection device also comprises, for each valve,a means (40) for temporarily retaining the second part (30) relative to the first part (20) so as to impose, in operation, a desynchronized movement between the second part (30) of the valve and the piston (1)., Device according to claim 1 wherein the movement of the first part (20) of the valve is controlled solely by the piston (1), while the second part (30) surrounds the first part (20) so that the first part (20) can slide inside the second part (30). Device according to claim 1 or 2 in which the first part (20) comprises a rod (21) and a support washer (22), and the second part (30) comprises:- a chamber (31) provided with a bottom (311) and a washer seat (312), in which the first part (20) slides, and- an end (35) provided with a valve head (32). Device according to claim 3 in which the temporary retaining means is constituted by a spring (40), the first part (20) comprising, at its end intended to be arranged opposite the piston (1), the support washer (22), the spring extending between the bottom (311) of the chamber (31) and the support washer (22), the rod (21) protruding by a determined length (L2) from the end (35) of the valve head (32) when the support washer (22) is in abutment against the washer seat (312). Device according to claim 3 or 4 in which the head (32) of the valve is configured to protrude by a non-zero length (L1) into the chamber (5) of the piston (1) when the device is in the position of use in the engine and the valve is in the closed position. Device according to one of claims 3 to 5 in which the valve head (32) has a truncated cone shape. Cylinder head intended for a compressed air engine equipped with a device according to one of claims 1 to 6. Compressed air engine comprising a cylinder head according to claim 7. Hybrid powertrain for equipping a vehicle comprising a high-pressure compressed air reservoir connected to a compressed air piston engine according to claim 8, engaged with an electric generator for generating electricity when driven by the compressed air piston engine, the generator being connected to at least one electric motor connected to a transmission engaged with a moving member of the vehicle. Powertrain according to claim 9, in which the generator and said at least one electric motor are connected via a relay electrical reserve with a capacity of between 0.2 and 2.2 Watt-hours per kilo of vehicle to be equipped (Wh / kg of vehicle). Powertrain according to claim 9 or 10, further comprising an accelerator control movable between a stop position and a maximum acceleration position and connected to an electronic control circuit comprising a controller programmed to power the electric motor from the relay electrical reserve as a function of a signal captured by at least one sensor fitted to the vehicle. A generator set comprising a high pressure compressed air reservoir connected to a compressed air piston engine according to claim 8, engaged with an electric generator for generating electricity when driven by the compressed air piston engine.

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