Technical Sector

The present invention relates to a multi-purpose hydraulic system comprising an electrically powered hydraulic pump and to a method of operating said system.

The multi-purpose hydraulic system has a particular application in the motor-vehicle sector.

Prior Art

Hydraulic systems for motor vehicles are known where a hydraulic pump actuated by means of an electric motor (electric pump) supplies a liquid to a using device.

For example, in hybrid vehicles hydraulic systems are used where an electric hydraulic pump is actuated, generally when the internal combustion engine is inactive, in order to supply the cooling liquid to the gear box and/or liquid for selection of the gear ratios. The document JP2014213635 A describes, for example, a lubricating system for a hybrid vehicle in which a primary oil pump mechanically actuated by the internal combustion engine of the vehicle feeds a hydraulic circuit in order to lubricate the internal combustion engine, while a secondary electric oil pump is actuated by an electronic control unit when the internal combustion engine - and therefore the primary oil pump - are inactive, in order to lubricate the power transducers of the hybrid population system of the vehicle.

Another known application envisages the use of electric hydraulic pumps for lubrication of an internal combustion engine, said pumps assisting a main pump mechanically actuated by the same internal combustion engine. The document US2013319366 A1 describes, for example, a system comprising a primary oil pump actuated mechanically by an internal combustion engine, a secondary electric oil pump and a non-return valve designed to prevent the flow of oil from the outlet of the primary pump to the outlet of the secondary electric pump. An electronic control device is configured to actuate the secondary electric pump when the primary pump is inactive. This system is used as a hydraulic pressure generator or also to supply lubricating liquid.

A further known application is illustrated in EP3150811 Al, which describes a system for lubricating and cooling an internal combustion engine, which comprises hydraulic actuating members actuated by means of the pressurized oil of the lubrication and cooling system. The system comprises a mechanical pump mechanically actuated by the internal combustion engine and connected to the hydraulic actuating members, and an auxiliary electric pump which feeds a nozzle of an oil jet cooling system for cooling the pistons of the internal combustion engine. The flow exiting the auxiliary electric pump may be diverted from the nozzle and directed towards the electrical actuating members by means of an electric valve controlled by an electronic control unit, in order to increase the pressure supplied to the actuating members.

A further example of an application of electric hydraulic pumps relates to vehicles provided with a start-stop system, namely a system for automatically switching off and switching on again the internal combustion engine in order to reduce the time for which the engine remains active when the vehicle is at a standstill, or with a "sailing" function, namely for disengaging the transmission from the internal combustion engine when the foot is raised from the accelerator pedal so that more efficient use is made of the kinetic energy stored by the vehicle. In both the aforementioned cases, the electric hydraulic pump is actuated so as to take over from the mechanical pump which is no longer in operation owing to deactivation of the internal combustion engine.

The hydraulic systems for motor vehicles equipped with a secondary or auxiliary hydraulic pump actuated by means of an electric motor have the problem associated with the complex management of the various applications, which envisages (depending on the number and complexity thereof) at least an electric valve controlled by an electronic control unit and/or the need for further pumps electrically controlled for the various applications, something which results in a greater energy consumption and therefore higher costs and greater polluting emissions.

The object of the present invention is to overcome the problems and limitations of the prior art by providing a hydraulic system able to manage several circuits with various applications without the aid of additional electrical components, allowing savings in cost, while optimizing the consumption levels and reducing the harmful emissions.

This object as well as other objects are achieved with the multi-purpose hydraulic system as claimed in the attached claims.

Description of the Invention

The multi-purpose hydraulic system for motor vehicles according to the present invention comprises a primary hydraulic circuit and a secondary hydraulic circuit. The primary hydraulic circuit comprises a primary hydraulic pump and at least one primary using device communicating with a delivery duct of the primary hydraulic pump. The secondary hydraulic circuit comprises an electrically actuated secondary hydraulic pump and at least one secondary using device.

In accordance with a preferred characteristic feature of the present invention, the multi purpose hydraulic system comprises a diverter valve applied to the delivery duct of the secondary hydraulic pump, for example directly downstream of the secondary hydraulic pump. This diverter valve is designed to connect selectively and alternately the delivery duct of the secondary hydraulic pump to the at least one secondary using device or to the at least one primary using device depending on the operation status of the primary hydraulic pump, namely depending on whether the primary hydraulic pump is in operation or not.

The diverter valve is preferably an automatic hydraulic valve, i.e. a valve which is operated automatically as a result of hydraulic pressures produced by the primary hydraulic pump and the secondary hydraulic pump. In particular, the diverter valve, which is preferably normally open towards the at least one primary using device, is configured to open towards the at least one secondary using device when the primary hydraulic pump is in operation, by means of a hydraulic pressure generated by the primary hydraulic pump.

Advantageously, owing to the fact that the diverter valve is an automatic hydraulic valve, the multi-purpose hydraulic system according to the present invention allows at least two functions performed by an electric hydraulic pump in a motor vehicle to be combined without the aid of additional electrical components, by feeding two hydraulic circuits alternately. This allows cost savings to be obtained, while optimizing consumption and reducing harmful emissions.

Preferably, the diverter valve is a three-way and two-position valve, in which a first way is a first outlet selectively connected to the at least one primary using device, a second way is a second outlet selectively connected to the at least one secondary using device, and a third way is an inlet connected to the delivery duct of the secondary hydraulic pump. The diverter valve is normally in a first one of the two positions, in which the inlet is connected solely to the first outlet and is able to switch, by means of suitable actuating elements, from the first one of the two positions to a second one of the two positions, in which the inlet is connected solely to the second outlet.

Preferably, the actuating elements comprise a first actuating surface acted upon by the liquid exiting the primary hydraulic pump, a second actuating surface acted upon by the liquid exiting the secondary hydraulic pump, and a spring, wherein the second actuating surface and the spring act in order to switch the diverter valve to the first one of the two positions, while the first actuating surface acts in order to switch the diverter valve to the second one of the two positions.

The multi-purpose hydraulic system further comprises preferably a connecting duct between the primary circuit and the secondary circuit, comprising an overpressure hydraulic valve of the non-return type, designed to allow a liquid flow only from the primary circuit towards the secondary circuit when a predetermined pressure threshold is exceeded. Advantageously, this is useful in the case of cold operation of the hydraulic system, when the secondary hydraulic pump is not in operation. In this situation, in fact, the connecting duct and the overpressure valve allow part of the liquid exiting the primary hydraulic pump to be conveyed towards the secondary circuit and therefore towards the at least one secondary using device. The operation of the multi-purpose hydraulic system according to the present invention comprises the steps of:

- hydraulically connecting the primary hydraulic pump to the at least one primary using device;

- hydraulically connecting, selectively and alternately, by means of the diverter valve, the secondary hydraulic pump to the at least one primary using device or to the at least one secondary using device, depending on the operation status of the primary hydraulic pump.

The step of selectively and alternately connecting the secondary hydraulic pump to the at least one primary using device or to the at least one secondary using device comprises the steps of:

- switching the diverter valve so as to connect the secondary hydraulic pump to the at least one secondary using device when the primary hydraulic pump is in operation, by means of the hydraulic pressure generated by the primary hydraulic pump in the primary hydraulic circuit;

- switching the diverter valve so as to connect the secondary hydraulic pump to the at least one primary using device when the primary hydraulic pump is not in operation. The method of operating the multi-purpose hydraulic circuit further comprises the step of hydraulically connecting the primary hydraulic pump to the at least one secondary using device when the primary hydraulic pump is in operation and the secondary hydraulic pump is not in operation, by means of the aforementioned connecting duct and the overpressure valve.

In accordance with an example of application of the multi-purpose hydraulic system according to the present invention, the at least one primary using device is an internal combustion engine, the primary hydraulic circuit is a lubrication circuit for the internal combustion engine and the primary hydraulic pump is mechanically actuated by the internal combustion engine. Furthermore, the secondary hydraulic pump feeds the secondary hydraulic circuit which is able to cool the pistons of the internal combustion engine when the internal combustion engine is active, and therefore the primary hydraulic pump is in operation, while it feeds the primary hydraulic circuit when the internal combustion engine is inactive, and therefore the primary hydraulic pump is not in operation. This latter condition occurs, for example, when vehicles provided with a start-stop system stop, or when the engine is disengaged from the transmission following release of the accelerator pedal of vehicles provided with the "sailing" function.

In accordance with a further example of application of the multi-purpose hydraulic system according to the present invention, the at least one primary using device is a gear box, the primary hydraulic circuit is designed to supply pressurized liquid for actuating the gear box, and the primary hydraulic pump is mechanically actuated by a propulsion member of the vehicle, such as an internal combustion engine, an electric motor or an eAxle. Moreover, the secondary hydraulic pump feeds the secondary hydraulic circuit for cooling and lubricating the gear box when the propulsion member is active, and therefore the primary hydraulic pump is in operation, and feeds the primary hydraulic circuit when the propulsion member is inactive, and therefore the primary hydraulic pump is not in operation. This conditions occurs, for example, when vehicles provided with a start-stop system stop, or when the engine is disengaged from the transmission following release of the accelerator pedal of vehicles provided with the "sailing" function.

Brief Description of the Figures

These and other characteristic features and advantages of the present invention will emerge more clearly from the following description of preferred embodiments provided by way of a non-limiting example with reference to the attached drawings in which:

- Figure 1 shows a schematic view of the multi-purpose hydraulic system according to an embodiment of the present invention;

-Figure 2 shows a schematic view of the multi-purpose hydraulic system according to a further embodiment of the present invention.

Description of some Preferred Embodiments of the Invention

With reference to Figure 1, a multi-purpose hydraulic system 10 for motor vehicles according to a preferred embodiment of the invention comprises a primary hydraulic circuit and a secondary hydraulic circuit.

The primary hydraulic circuit comprises a tank 8 containing a liquid 9, a primary hydraulic pump 1, which is typically mechanically actuated by the propulsion member of the vehicle, such as an electric combustion engine, an electric motor or an eAxle, communicating with the tank 8 via an intake duct la of the pump and designed to pump the liquid contained in the tank 8, and at least one primary using device 3

communicating with a delivery duct lb of the primary pump 1, from which it receives the pumped liquid and is connected downstream to the tank 8. Preferably a filter 2 is present upstream of the at least one using device 3.

The secondary hydraulic circuit comprises the tank 8, a secondary hydraulic pump 4, typically a pump actuated by an electric motor (not shown) driven by an electronic control unit ECU (not shown). The secondary hydraulic pump 4 communicates, via an intake duct 4a, with the tank 8 and, via a delivery duct 4b, with at least one secondary using device 6 designed to receive the liquid pumped by the said pump 4.

In accordance with the present invention, a diverter valve 5 is present along the delivery duct 4a of the secondary hydraulic pump 4, for example directly downstream of the secondary hydraulic pump 4, and is able to connect selectively and alternately the delivery duct 4b of the secondary hydraulic pump 4 to the at least one secondary using device 6 or to the at least one primary using device 3, which is preferably branched off upstream of the filter 2, depending on the operation status of the primary hydraulic pump 1, namely depending on whether the primary hydraulic pump is in operation or not.

The diverter valve 5 is preferably an automatic hydraulic valve, i.e. a valve, operation of which occurs automatically as a result of hydraulic pressures, in particular hydraulic pressures produced by the primary hydraulic pump 1 and by the secondary hydraulic pump 4. The diverter valve 5 is, for example, a valve of the known three-way and two- position type, in which a first way is a first outlet 5a, connected selectively upstream of the at least one primary using device 3 and preferably upstream of the filter 2, a second way is a second outlet 5b, connected selectively upstream of the at least one secondary using device 6, and a third way is an inlet 5c, connected to the delivery duct 4b of the secondary hydraulic pump 4. The diverter valve 5 is able to switch between a first one of the two positions, in which the inlet 5c is solely connected to the first outlet 5a, and a second one of the two positions, in which the inlet 5c is solely connected to the second outlet 5b. This switching is performed by means of actuating elements of the valve, of the known type, which comprise preferably a first actuating surface (not shown) acted upon by the pumped liquid exiting the primary hydraulic pump 1 via a first duct 16, a second actuating surface (not shown) acted upon by the liquid exiting the secondary pump 4 via a second duct 17, and a spring 5d. In particular, the diverter valve 5, which is normally in the first position, i.e. is normally open towards the at least one primary using device 3, is configured to open towards the at least one secondary using device 6, i.e. to switch towards the second position, when the primary hydraulic pump 1 is in operation, owing to the force generated by the liquid acting on the first actuating surface, said force overcoming the opposing force generated by the spring 5d and the liquid acting on the second actuating surface.

Preferably, the diverter valve 5 is configured to remain open towards the at least one secondary using device 6 also when the propulsion member which operates the primary hydraulic pump 1 is operating at a minimum, namely when the pressure of the liquid exiting the primary hydraulic pump 1 is approximately equal to the pressure of the liquid exiting the secondary hydraulic pump 4. This is obtained, for example, by designing the first actuating surface of the diverter valve 5 so as to have dimensions larger than those of the second actuating surface.

It should be noted that the illustration of the diverter valve 5 shown in the figures is only a schematic illustration and is not intended to illustrate constructional details of the said valve.

The first duct 16 and the second duct 17 also act, preferably, as pressure detection ducts for detecting, respectively, the pressure in the primary circuit, for example upstream of the filter 2, and the pressure in the delivery duct 4b of the secondary hydraulic pump 4.

Optionally, a non-return valve 7 is present downstream of the primary hydraulic pump 1 and is designed to prevent a backflow of liquid from the delivery duct 4b of the secondary hydraulic pump 4 towards the delivery duct lb of the primary hydraulic pump 1. In accordance with a further embodiment, the multi-purpose hydraulic system 10 comprises, in addition to the elements described hitherto, a connecting duct 14 between the primary circuit, branched off downstream of the primary hydraulic pump 1 and upstream of the filter 2, and the secondary circuit, branched off downstream of the diverter valve 5 and upstream of the at least one secondary using device 6. The connecting duct 14 comprises a hydraulic overpressure valve 15, of the non-return type, designed to allow a liquid flow only from the primary circuit towards the secondary circuit when a given threshold pressure is exceeded. Preferably, the hydraulic overpressure valve 15 is calibrated so that the threshold pressure is lower than the operating pressure of the primary hydraulic pump 1 and higher than the operating pressure of the secondary pump 4. In this way, the flow of liquid from the primary circuit to the secondary circuit occurs when only the primary hydraulic pump 1 is in operation, but does not occur when only the secondary hydraulic pump 4 is in operation.

Advantageously, the aforementioned embodiment is useful in the case of cold operation of the system, when the secondary hydraulic pump 4 is not in operation. In this situation, in fact, the connecting duct 14 and the overpressure valve 15 allow part of the liquid exiting the primary hydraulic pump 1 to be conveyed towards the secondary circuit and therefore towards the at least one secondary using device 6. Operation of the hydraulic system 10 is now described.

Under normal running conditions, both the hydraulic pumps are in operation. The primary hydraulic pump 1 sends the pumped liquid to the at least one primary using device 3 and at the same time causes switching of the diverter valve 5 towards its second position, such that the secondary hydraulic pump 4 sends the liquid pumped to the at least one secondary using device 6, thus satisfying the flowrate and pressure requirements of the secondary hydraulic circuit.

Preferably, the diverter valve 5 remains switched in the second position also when the propulsion member which actuates the primary hydraulic pump 1 is operating at a minimum.

When, instead, the primary hydraulic pump 1 is not in operation, the diverter valve 5 switches towards its first operating position such that the secondary hydraulic pump 4 sends the liquid 9 to the at least one primary using device 3, feeding the primary hydraulic circuit as required during this phase. Optionally, during this phase, the backflow of fluid from the delivery duct 4b of the secondary hydraulic pump 4 towards the delivery duct lb of the primary hydraulic pump 1 is prevented owing to the non return valve 7.

Finally, in accordance with the embodiment where the connecting duct 14 is provided between the primary circuit and the secondary circuit, when only the primary hydraulic pump 1 is in operation, for example in the case of cold operation as described above, the primary hydraulic pump 1 feeds both the primary circuit and the secondary circuit. Some examples of application of the multi-purpose hydraulic system 10 described above are illustrated below.

According to a first example of application a primary using device is an internal combustion engine, the primary hydraulic circuit is a lubrication circuit for the internal combustion engine and the primary hydraulic pump is actuated mechanically by the internal combustion engine. The secondary hydraulic circuit, comprising an electrically actuated secondary hydraulic pump, is instead used to feed an oil jet cooling system for cooling the pistons of the internal combustion engine.

In accordance with this example of embodiment, when the internal combustion engine is inactive, for example in the case of inactivity due to stoppage of vehicles provided with a start-stop system, or when the engine is disengaged from the transmission following release of the accelerator pedal of vehicles provided with the "sailing" function, the secondary hydraulic pump feeds the primary hydraulic circuit, namely the circuit lubricating the internal combustion engine, so as to prevent wear of parts of the said engine upon restarting thereof.

According to a second example of application the hydraulic system is used in hybrid vehicles or vehicles with eAxles. In this case, the primary using device is the gear box and the primary hydraulic circuit is used to supply pressurized liquid for actuation of the gear box by means of the primary hydraulic pump actuated mechanically by a propulsion member of the vehicle, such as an internal combustion engine, an electric motor or an eAxle. The secondary hydraulic circuit, owing to the electrically actuated secondary hydraulic pump, is instead used for cooling and lubrication of the gear box. With the multi-purpose hydraulic system 10 therefore both the gear box function, which typically requires a higher pressure, and the cooling and lubrication function, which typically requires a lower pressure, may be provided.

In accordance with the aforementioned example of embodiment, when the propulsion system of the vehicle is active, the primary hydraulic pump operates so as to supply liquid at high pressure for actuation of the gear box, while the secondary hydraulic pump supplies liquid at a lower pressure in order to cool and lubricate the gear box. When the propulsion member of the vehicle is inactive, for example in the case of inactivity due to stoppage of vehicles provided with a start-stop system or when the propulsion member is disengaged from the transmission following release of the accelerator pedal of vehicles provided with the "sailing" function, the secondary hydraulic pump feeds the primary hydraulic circuit, performing the function of prefilling the actuating members of the transmission so as to speed up the actuating function performed upon restarting of the primary hydraulic pump.

Advantageously, owing to the presence of the diverter valve, the multi-purpose hydraulic system according to the present invention allows at least two functions performed by an electric hydraulic pump in a motor vehicle to be combined without the aid of additional electrical components, feeding two hydraulic circuits alternately. This allows cost savings to be obtained along with optimum consumption levels and a reduction in harmful emissions.

In accordance with further embodiments a multi-purpose hydraulic system comprising more than two hydraulic circuits may be provided.

The multi-purpose hydraulic system as described and illustrated may be subject to further variations and modifications, falling within the scope of the same inventive idea.