Patent Description:
Automotive vehicles, such as trucks, are equipped with air compressors for feeding some auxiliary systems, such as braking systems, with compressed air. To increase the air delivery and reduce the power consumption of the air compressors, it is known to feed the air compressor with compressed air produced by a turbocompressor of the vehicle. This allows operating the air compressor at a lower compression rate. Such technique is for instance described in <CIT>, in which compressed air is delivered to the air compressor from the turbocompressor if enough compressed air is available.

Air compressors are designed to work in a predetermined air pressure range. The compressed air delivered by the turbocompressor may have pressure peaks depending on the operation conditions of the internal combustion engine of the vehicle. If the air compressor is fed with air pressures that are above the maximal pressure value of the pressure range, the air compressor may be damaged.

To withstand pressure peaks, the compression ratio of the air compressor should be reduced, and internal component be reinforced to accept addition constraint. If the turbocompressor does not deliver enough pressured air (for example when the engine is idle) to the air compressor with reduces compression ratio, the compression efficiency may be low, leading to increased filling time of the air tanks and fuel overconsumption.

<CIT> discloses a system for operating a compressor powered by an internal combustion engine for compressing air, wherein a first turbocharger for supplying pre-compressed air to the internal combustion engine is disposed in an exhaust flow of the internal combustion engine. Furthermore, a second turbocharger for pre-compression of the air to be compressed by the compressor is disposed in the exhaust flow of the internal combustion engine. The pressure of the pre-compressed air generated by the first turbocharger is monitored during an operating state of the compressor, and the operating state is termined as soon as the monitored pressure falls below a previously determined value.

The aim of the invention is to provide a compressed air generation system in which the operation of the air compressor is optimized to withstand overpressure peaks in the compressed air delivered by the turbocompressor and avoid power overconsumption.

To this end, the invention concerns a compressed air generation system according to the appended set of claims.

The invention also concerns an automotive vehicle comprising a compressed air generation system as defined in claim <NUM>.

The invention will now be explained in reference to the annexed drawings, as an illustrative example. In the annexed drawings:.

An automotive vehicle V, such as a truck, represented on <FIG> comprises an internal combustion engine <NUM> adapted to be fed with compressed air produced by a turbocompressor <NUM>. The turbocompressor <NUM> produces compressed air from air at atmospheric pressure thanks to a compressor <NUM> which is driven by a turbine <NUM>, the latter using the energy of exhaust gases flowing in an exhaust line <NUM> of the vehicle V. Air at atmospheric pressure is extracted from the outside of the vehicle V with an air filter <NUM>. Compressed air is driven, as shown by arrows A1 , from the turbocompressor <NUM> to the engine <NUM> through an air intake pipe <NUM>.

The vehicle V comprises an air compressor <NUM>. For example, the air compressor <NUM> can be a piston compressor.

The air compressor <NUM> is adapted to feed a compressed air tank <NUM> in which compressed air is stored in order to feed one or several pneumatically driven sub-systems of the vehicle V, such as a non-shown braking system.

The air compressor <NUM> is adapted to compress air provided by the turbocompressor <NUM>.

The air compressor <NUM> is fed by an inlet pipe <NUM> which originates from the air intake pipe <NUM>. Compressed air is fed to the tank <NUM> via an outlet pipe <NUM> of the air compressor <NUM>.

The air compressor <NUM>, the turbocompressor <NUM> and the air tank <NUM> form together a compressed air generation system <NUM>.

The compressed air generation system <NUM> comprises a pressure regulator <NUM> connected upstream the air compressor <NUM> and which limits the pressure P4 of the compressed air fed from the turbocompressor <NUM> to the air compressor <NUM>. As represented on <FIG>, this allows limiting the intake pressure P8 of the air compressor <NUM> below a first threshold T1 corresponding to a maximal intake pressure of the air compressor <NUM>, which is a data inherent to the design of the air compressor <NUM>. For example, the air compressor <NUM> may be designed to compress air at a pressure of <NUM>,<NUM> bar from air at a pressure between <NUM> to <NUM> bar. If the air compressor <NUM> was fed with an intake pressure of <NUM> bar superior to this maximal intake pressure of <NUM> bar, the air compressor <NUM> would risk damages. Pressure peaks in the compressed air delivered by the turbocompressor <NUM>, shown on <FIG>, are therefore not able to damage the air compressor <NUM>, and the air compressor <NUM> does not need to be designed with a lower compression ratio that would incur higher power consumption and reduced performance.

The pressure regulator <NUM> is represented on <FIG> and <FIG>. The pressure regulator <NUM> comprises a valve body <NUM> on which are provided an intake port <NUM> connected to a first section 80a of the inlet pipe <NUM>, and an outlet port <NUM> connected to a second section 80b of the inlet pipe <NUM>. The pressure regulator <NUM> comprises a central chamber <NUM> in which is mounted a piston <NUM>. The piston <NUM> is movable in translation along a central longitudinal axis X24, which also forms a central longitudinal axis of the central chamber <NUM>.

The piston <NUM> comprises a collar <NUM> adapted to make contact with a valve seat <NUM> of the valve body <NUM> to close passage of air from the intake port <NUM> towards the outlet port <NUM>. Non-shown sealing gaskets may be provided on the collar <NUM> to tighten contact with the seat <NUM>.

When the pressure regulator <NUM> is open (<FIG>), air flows around the collar <NUM> towards the outlet port <NUM>, as shown by arrows A2. Near the outlet port <NUM>, the valve body <NUM> comprises a calibrated hole <NUM> which puts into fluid communication the chamber <NUM> with the outlet port <NUM> at a defined flow. The pressure in the outlet port <NUM> therefore exerts a force on an active surface <NUM> of the piston <NUM>, against the biasing force of a spring <NUM> of the pressure regulator <NUM>, which urges the piston <NUM> upwards so that the collar <NUM> is driven away from the seat <NUM>. The force of the spring <NUM> can be modified using a screw <NUM>.

Depending on the air pressure, equal to the pressure P4, in the intake port <NUM>, which communicates with the chamber <NUM> via the outlet port <NUM> and the hole <NUM>, the piston <NUM> is driven downwards along arrow A3, resulting in the collar <NUM> getting closer to the seat <NUM> and limiting the air pressure that flows into the outlet port <NUM>, equal to the intake pressure P8 of the air compressor <NUM>.

The compressed air generation system <NUM> comprises a tank sensor <NUM> adapted to detect the quantity of compressed air contained in the air tank <NUM>, and a controlled valve adapted to close the feeding of the inlet pipe <NUM> of the air compressor <NUM> with the turbocompressor <NUM> if the tank sensor <NUM> detects that the air tank <NUM> is full. The tank sensor <NUM> may be a pressure sensor adapted to measure the air pressure P10 in the tank <NUM>. During filling of the air tank <NUM>, the air pressure P10 of the air tank <NUM> progressively increases up to a maximal pressure Pmax.

The controlled valve is formed by the pressure regulator <NUM> that can be closed. The pressure regulator <NUM> comprises a controllable actuator adapted to close the pressure regulator <NUM> whatever the respective pressures P4 and P8 in the inlet port <NUM> and the outlet port <NUM>.

The controllable actuator is a pressure-controlled piston <NUM> which closes the pressure regulator <NUM> by acting to move the piston <NUM> towards a closed position shown on <FIG> ("Mode closed" on <FIG>). The piston <NUM> is housed in an auxiliary chamber <NUM> of the valve body <NUM>. The auxiliary chamber <NUM> comprises a hole 164a through which a control air pressure is injected in the chamber <NUM> to urge the piston <NUM> downwards to act, with a rod <NUM> of the piston <NUM> extending along the central axis X24, on the piston <NUM>, as shown by arrow A4. In such a case, the piston <NUM> directly acts on the piston <NUM> to close the pressure regulator <NUM>.

In the absence of control pressure acting on the pressure controlled piston <NUM>, the pressure controlled piston <NUM> is urged upwards, towards its position of <FIG>, by a spring <NUM>. The piston <NUM> does therefore not act on the piston <NUM>, and the pressure regulator <NUM> is therefore not closed by the piston <NUM>. The pressure regulator <NUM> is still able to be closed depending on the air pressures in the inlet and outlet ports <NUM> and <NUM>.

The closing of the pressure regulator <NUM> if the air tank <NUM> is full avoids operation of the air compressor <NUM> while air compression is not useful. The closing of compressed air feeding of the air compressor <NUM> from the turbocompressor <NUM> avoids operation of the air compressor <NUM> while it is not desired. From the closing of the pressure regulator, the pressure P10 remains steady at value Pmax.

The compressed air generation system <NUM> comprises a control unit <NUM> able to receive signals from the tank sensor <NUM>, and to control the pressure regulator <NUM> via a pneumatic control pipe <NUM> connected to the hole 164a. The control unit <NUM> may include electronic and/or pneumatic components.

In order to guarantee that the air compressor <NUM> does not operate while the air tank <NUM> is full, the air compressor <NUM> is able to be stopped or placed in a rest mode when the tank sensor <NUM> detects that the air tank <NUM> is full. This control of the air compressor <NUM> is operated with the control unit <NUM> via an electric signal. The control unit <NUM> may also be able to control any other working parameter of the air compressor <NUM>.

According to an embodiment, not in accordance with the appended claims, the controlled valve may be distinct from the pressure regulator <NUM> and be formed by a valve <NUM>, for example a three-way valve, connected on the first section 80a of the inlet pipe <NUM>, upstream the pressure regulator <NUM>. The valve <NUM> may be controlled by the control unit <NUM>.

The pressure regulator <NUM> comprises a pressure relief valve adapted to release to the atmosphere compressed air accumulated between the pressure regulator <NUM> and the air compressor <NUM>, in other words, in the second section 80b of the inlet pipe <NUM>.

For example, as represented on <FIG> and <FIG>, the pressure regulator <NUM> may comprise a movable shutter <NUM> housed in another chamber <NUM> of the valve body <NUM>, which is in fluid communication with the inlet port <NUM> and the outlet port <NUM>, with the chamber <NUM>, and with a central channel <NUM> of the piston <NUM>. The shutter <NUM> is movable with respect to the piston <NUM> along the central axis X24. The central channel <NUM> extends around the central axis X24 and provides a fluid communication between the chamber <NUM> and the chamber <NUM>. The pressure regulator <NUM> comprises a spring <NUM> that pushes the shutter <NUM> to close the central channel <NUM> unless the pressure between the pressure regulator <NUM> and the air compressor <NUM> becomes superior to the first threshold T <NUM>.

When the air tank <NUM> is full, the piston <NUM> is moved towards the closed position of the pressure regulator <NUM>, as shown on <FIG>. In this configuration, the collar <NUM> is in contact with the seat <NUM>, and the shutter <NUM> is pushed against the collar <NUM>, preventing fluid communication between the chamber <NUM> and the chamber <NUM>. If the intake pressure P8, which exists in the outlet port <NUM>, increases above the first threshold T1 , the piston <NUM> goes further downwards along arrow A3 thanks to a freedom in translation along the axis X24 of a central tubular portion <NUM> of the piston <NUM>, which surrounds the central channel <NUM>, with respect to the collar <NUM>. The piston <NUM> is pushed further in the chamber <NUM> to such a point that the tubular portion <NUM> is driven away from the shutter <NUM>. This creates a fluid communication between the outlet port <NUM> and the central channel <NUM>. Excess air pressure can therefore flow in the central channel <NUM> from the outlet port <NUM>, as shown by arrow A5. Excess air pressure is also returned to the outlet port <NUM> via the calibrated hole <NUM> under action of the spring <NUM>.

Compressed air flowing in the central channel <NUM> flows in the chamber <NUM>, which comprises air vents <NUM> allowing release of the air contained in the chamber <NUM> to the atmosphere, as shown by arrows A6. The portion of the chamber <NUM> located on the side of the active surface <NUM> is sealed from the atmosphere by a sealing gasket <NUM>.

A second embodiment of the invention is represented on <FIG>, the pressure relief valve of the pressure regulator may be adapted to open when the pressure regulator <NUM> is closed, and when the intake pressure P8 between the pressure regulator <NUM> and the air compressor <NUM> becomes superior to a second threshold T2 inferior to the first threshold T1. The second threshold T2 may be, for example, <NUM> bar. The features common with the pressure regulator of the first embodiment have the same references and work in the same way.

In the pressure regulator of <FIG>, there is no pressure controlled piston <NUM> on the upper side of the valve body <NUM>. Instead the pressure regulator <NUM> comprises a pressure controlled piston <NUM> located within a lower side <NUM> of the pressure chamber <NUM>. The piston <NUM> comprises an upper plate <NUM> which is put into contact with the piston <NUM> by the spring <NUM>. In this case, there is no screw <NUM> represented, however the pressure regulator may comprise such a screw. The plate <NUM> closes the central channel <NUM>.

The piston <NUM> comprises a rod <NUM> which is partially inserted into an auxiliary chamber <NUM> located inside the lower side <NUM> of the chamber <NUM>. In the auxiliary chamber <NUM>, the piston <NUM> is terminated by a head <NUM>, comprising a sealing gasket <NUM>. Another sealing gasket <NUM> is provided around the rod <NUM> to tighten the auxiliary chamber <NUM>.

The pressure regulator <NUM> comprises a duct <NUM> which provides fluid communication between the auxiliary chamber <NUM> and the outside of the pressure regulator <NUM>, allowing a control pressure to be exerted in the auxiliary chamber <NUM>.

In the embodiment of <FIG>, the piston <NUM> comprises a peripheral wall <NUM> which extends downwards, and which is located radially outwards with respect to the spring <NUM>.

The working principle of the pressure regulator <NUM> is described on <FIG>. On <FIG>, the pressure regulator <NUM> functions in a pressure regulation only mode: pressure peaks in the inlet port <NUM> induce downwards movements of the piston <NUM>, reducing the fluid passage between the collar <NUM> and the seat <NUM>. In this configuration, the peripheral wall <NUM> is raised with respect to a bottom wall <NUM> of the chamber <NUM>.

On <FIG>, a control pressure PC is applied in the duct <NUM>. The pressure increase in the auxiliary chamber <NUM> induces a downward movement, along arrow A7, of the piston <NUM>, against the force of the spring <NUM>. The plate <NUM> is not anymore in contact with the piston <NUM>. The piston <NUM> is therefore free to be pushed downwards by the spring <NUM>, via the shutter <NUM>. Under action of the spring <NUM>, the shutter <NUM> and the piston <NUM>, the collar <NUM> is pushed against the seat <NUM> to achieve forced closure of the pressure regulator <NUM> (Mode closed). In such a case, the pressure-controlled piston <NUM> closes the pressure regulator <NUM> in an indirect way using the force of the spring <NUM>.

In this configuration, the peripheral wall <NUM> has been moved closer to the bottom wall <NUM>, but the piston <NUM> is still free to move downwards.

On <FIG>, a pressure peak occurs in the outlet port <NUM> whereas the valve is forced in a closed position (Mode closed on <FIG>). Through the hole <NUM>, the pressure is exerted on the surface <NUM> of the piston <NUM>. Due to the fact that the spring <NUM> does not push the piston <NUM> upwards anymore, the piston <NUM> can be moved downward at a pressure threshold T2 inferior to T1 , provoking opening of the central channel <NUM> and purging of fluid through the channel <NUM> and the air vents <NUM>. The piston <NUM> may move downwards until the peripheral wall <NUM> comes into abutment with the bottom wall <NUM>.

The travel of the piston <NUM> from its position of <FIG> towards its position of <FIG> is allowed by the fact that the piston <NUM> has a running distance D50 superior to the running distance D24 of the piston <NUM>. The plate <NUM> of the piston <NUM> does therefore not limit the piston <NUM> when the piston <NUM> move further downwards to open the pressure relief valve.

The pressure control of the piston <NUM> may also be controlled via the control unit <NUM>.

The intake pressure P8 therefore remains steady at the value T2. This pressure relief valve allows reducing the pressure between the pressure regulator <NUM> and the air compressor <NUM>, to avoid creation by the air compressor <NUM> a resisting couple on the crankshaft of the engine <NUM>.

According to a variant represented on <FIG>, the spring <NUM> may be housed in the auxiliary chamber <NUM> instead of being housed within the low side <NUM> of the chamber <NUM>. In such a case the plate <NUM> of the piston <NUM> has a reduced width with respect to the axis X24. The spring <NUM> is mounted between the head <NUM> and the bottom wall <NUM>.

According to an embodiment, the pressure relief valve may be distinct from the pressure regulator <NUM>, and formed by a valve <NUM> connected on the second section 80b, for example a three-way valve.

According to an optional embodiment, the vehicle V may comprise an exhaust aftertreatment system (EATS) <NUM> provided on the exhaust line <NUM> and adapted to reduce particulates in the exhaust gases. To operate properly, the EATS <NUM> must be cleaned from times to times by warming up at a temperature around <NUM>. To obtain this temperature, the exhaust gases can be warmed up by reducing the quantity of fresh air provided by the turbocompressor <NUM> in the air intake pipe <NUM>. This can be done by opening the pressure regulator <NUM> at a time when it is closed so that compressed air delivered by the turbocompressor <NUM> will not be delivered to the engine <NUM>, provoking an increase of the exhaust gases temperature. The compressed air tanks generally have a pressure varying between a cut-in threshold and a cut-off threshold (corresponding to the maximal pressure Pmax), which can be for example <NUM><NUM> bar and <NUM> bar. These thresholds can be changed during operation of the air tank <NUM>, for example increased by <NUM>,<NUM> bar during an operation period when energy is free because the vehicle V is braking. By setting the cut-in and cut off thresholds to higher values, the air compressor <NUM> becomes able to compress more air in the air tank <NUM>, and compressed air is therefore drawn from the air intake pipe <NUM>. This reduces the quantity of fresh air in the intake side of the engine <NUM>, thereby increasing the temperature of the exhaust gases and reducing the warming time of the EATS <NUM>.

The compressed air generation system <NUM> may also comprise a discharge valve <NUM>, connected on the outlet pipe <NUM>, and allowing evacuating air pressure downstream the air compressor <NUM> to avoid an overpressure in the air tank <NUM>. This may avoid having to act on the operating parameters of the air tank <NUM>. The discharge valve <NUM> may be controlled by the control unit <NUM>.

Claim 1:
Compressed air generation system (<NUM>) for an automotive vehicle (V), comprising:
- a turbocompressor (<NUM>) suitable for feeding an internal combustion engine (<NUM>) of the automotive vehicle (V) with compressed air,
- an air compressor (<NUM>),
- at least one compressed air tank (<NUM>) connected to an outlet pipe (<NUM>) of the air compressor (<NUM>),
the air compressor (<NUM>) comprising an inlet pipe (<NUM>) fed with compressed air from the turbocompressor (<NUM>),
wherein the compressed air generation system (<NUM>) comprises a pressure regulator (<NUM>) placed downstream the turbocompressor (<NUM>) and upstream the air compressor (<NUM>) and which limits the pressure (P8) of the compressed air fed from the turbocompressor (<NUM>) to the air compressor (<NUM>) to a first threshold (T1), wherein the compressed air generation system (<NUM>) comprises a tank sensor (<NUM>) adapted to detect the quantity of compressed air contained in the air tank (<NUM>), a control unit (<NUM>) which receives signals from the tank sensor (<NUM>) and controls the pressure regulator (<NUM>), and a controlled valve (<NUM>) adapted to close the feeding of the inlet pipe (<NUM>) of the air compressor (<NUM>) with the turbocompressor (<NUM>) if the tank sensor (<NUM>) detects that the air tank (<NUM>) is full, wherein the controlled valve is formed by the pressure regulator (<NUM>) that can be closed, and wherein the pressure regulator (<NUM>) comprises a controllable actuator (<NUM>; <NUM>) adapted to close the pressure regulator (<NUM>) whatever the pressure (P4) upstream the pressure regulator (<NUM>) and the pressure (P8) downstream the pressure regulator (<NUM>).