Hydraulic apparatus having an additional thrust section

The invention relates to a valve assembly (50) of a radial piston hydraulic apparatus (1). Said apparatus includes a cylinder block (4) insertable onto a shaft (2) by translation. Said assembly (50) includes: a valve (51) in contact with said cylinder block (4); a valve train cover (52); and a first (541) and second (542) chamber that are defined, respectively, by a first (511, 521) and second (512, 522) space that are located at the interface between said valve (51) and said valve train cover (52), and are intended for the pressurized fluids that enable the conversion of pressure and/or mechanical stress. Said assembly (50) includes an additional section (54) defined by a third space (541, 542) located at the interface between said valve (51) and said valve train cover (52). Said section (54) is intended for receiving a pressurized fluid such as to enable the cylinder block (4) to be inserted onto the shaft (2).

GENERAL TECHNICAL FIELD

The present invention relates to the field of hydraulic devices.

In particular, it relates to associated means for allowing the coupling of such hydraulic devices.

PRIOR ART

In all of the present text, a device capable of operating as a motor or as a hydraulic pump will be designated a hydraulic device. As shown inFIGS. 1aand 1b, a hydraulic device1comprises a shaft2, a cam3, typically a multilobe cam, a cylinder block4, a valve plate or distribution assembly5comprising a distributor51and a distributor cover52, and a casing6.

The cylinder block4is placed inside the annulus forming the cam3. It defines a plurality of cylinders41oriented radially with respect to an axis X-X′ of rotation (seeFIGS. 1aand 1b) and leading to the outer peripheral face of the cylinder block4facing the cam3.

A piston42is mounted with radial sliding respectively in each of the cylinders41. Each piston42is supported by the radially inner surface of the cam3.

The cylinder block4has a central bore by which it can be engaged on the end of the shaft2of the hydraulic device1.

The valve plate or distribution assembly50is formed from a distributor51and a distributor cover52which are adapted to apply in a controlled manner a fluid under pressure successively to each of the pistons42, more precisely in the inner chamber of the cylinders41adjacent to the pistons, so that the successive thrust of the pistons42on the lobes of the cam3drives the relative rotation of the cylinder block4and of the elements which are linked to it with respect to the cam3. The distributor51is movable in rotation along an axis co-linear with X-X′, which is the axis of the shaft2.

The valve plate or distribution assembly50comprises in particular two chambers511,521and512,522receiving a fluid under high or low-pressure depending on the mode of operation of the device.

Hydraulic devices are known which have a clutch release and clutch mechanism8based on thrust, thus allowing a free wheel configuration, i.e. the hydraulic device1operates without pressure (the pistons42therefore not carrying out reciprocating movements in contact with the cam3) and an operating configuration, i.e. a configuration in which the hydraulic device operates with fluid pressure and flow, the pistons42carrying out a reciprocating movement in contact with the cam.

When the clutch8is engaged, it is necessary to engage the cylinder block4on the shaft2so that said block4can transmit its torque. This engagement is accomplished in particular by the valve plate or distribution assembly50. In addition, the distribution assembly50supplies the cylinder block4with fluids under pressure. The sealing between said cylinder block4and said distribution assembly50is possible without a gasket thanks to permanent contact between the two.

To transmit torque without allowing the clutch8to slip, it is necessary to have considerable thrust by the distribution assembly50on the cylinder block4. Until now, this thrust is exerted by the fluids under pressure in the two chambers511,521and512,522of the distribution assembly50, so-called high-pressure chamber and low-pressure chamber depending on the mode of operation of the device.

Thus the fluids under pressure exert on the distributor51, via these chambers511,521and512,522, a force along the axis X-X′ of the shaft2, the distributor51then pressing against the cylinder block4and thus allowing the cylinder block4to engage on the shaft2. The high pressure is typically comprised between 400 and 500 bars.

More precisely, the chambers511,521, and512,522comprise two grooves511and512at the interface between the distributor51and the cover52for conveying the fluid, which cooperate with two complementary grooves521and522provided in the cover of the distributor52so as to form chambers or channels. Depending on the mode of operation of the hydraulic device1, each channel can be low or high pressure and is adapted to be respectively coupled to a hydraulic supply circuit71,72(seeFIGS. 3aand 3b). Each circuit can be low or high pressure depending on the operating mode.

The grooves511and512provided in the distributor51each have a side wall on the side in the direction of the cylinder block4.

Thus, as mentioned previously, the supply of fluid under high or low-pressure will tend to displace the distributor51toward the cylinder block4under the influence of the force resulting from the pressure applied to its side walls.

In this manner, the level of engagement of the cylinder block4on the shaft2depends directly on pressure, said pressure itself being correlated to the torque of the device1.

The pressure applied to engage the cylinder block4on the shaft2is therefore not constant, which is not desirable for a clutch. In particular, at starting, in order to obtain a satisfactory level of engagement, it is necessary to have a rather high minimum pressure, which implies in any case a strong boost level, the boost being supplied by a pump9so-called a booster pump, which ensures a minimum pressurization of the hydraulic circuits71,72. The boost pressure is on the order of the lower pressure, that is to say typically about ten bars.

The objective is therefore to provide a new device allowing the engagement of the cylinder block4on the shaft2to be improved.

PRESENTATION OF THE INVENTION

The present invention aims to propose a system not having such disadvantages.

To that end, the invention relates to a distribution assembly of a hydraulic device with radial pistons, said device comprising a cylinder block which can be engaged on a shaft by translation, said assembly comprising:A distributor, in contact with said cylinder block,A distribution cover,A first and a second chambers defined respectively by a first and a second volumes located at the interface between said distributor and said distribution cover, and intended for fluids under pressure allowing mechanical-pressure conversion,
said assembly being characterized in that it further comprises an additional section defined by a third volume located at the interface between said distributor and said distribution cover, said section being intended to receive a fluid under pressure to allow the engagement of the cylinder block on the shaft.

In addition, the invention can comprise the following features, taken alone or in combination:the additional section is entirely or partly located radially outside the first and second chambers, so that the surface of said additional section is greater.the supplying of the additional section is accomplished by selection of the lowest pressure between the two pressures relating to the first and second chambers.the distribution assembly comprises a low-pressure selector with an open center adapted to carry out the selection of the lowest pressure between the two pressures relating to the first and second chambers.the additional section is not radially rectilinear, but is typically S or Z-shaped, so as to optimize the volume and the sealing.

Another object of the invention relates to a hydraulic device including a distribution assembly as previously described, said assembly allowing in particular the engagement of said cylinder block on said shaft.

In addition, the invention can comprise the following features, taken alone or in combination:the distributor cover and the casing are integral or form one and the same part.the engagement of the cylinder block on the shaft is part of a clutch and clutch release system.

Finally, a final object of the invention relates to an engagement method of a cylinder block of a hydraulic device on a shaft, by means of a distribution assembly previously described in which:The additional section is pressurized by a fluid,The distributor is biased consecutively to the pressurization by a fluid of the additional section,The distributor biases by contact the cylinder block for engagement of said cylinder block on the shaft.

In all the figures, the common elements are labeled with identical numerical references.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

FIG. 2ashows a partial section view of a hydraulic device and of a distribution assembly according to one embodiment of the invention. As forFIGS. 1aand 1b, the axis of rotation X-X′ of the hydraulic device and a radial extension axis Y-Y′ are shown inFIGS. 2aand2b.

The common elements with the prior art previously described have the same denominations and alphanumeric references.

The general operation of the hydraulic device has been broadly described in documents FR 2955903 A1 and FR 2651836 A1, among others.

As mentioned previously, one of the embodiments of the clutch system consists of engaging by translation the cylinder block4on the shaft2.

A distribution plane53is defined between the distributor51and the cylinder block4, corresponding to the faces of the distributor51and of the cylinder block4adapted to be put in contact with one another.

In addition, sealing is provided by the particular configuration of the grooves511and512which provide for self-locking between the cylinder block4the distributor51.

The distributor cover52is typically fixed and integral with the casing6, and in particular fixed in translation along the axis X-X′. Alternatively, the distributor cover52can form one and the same part with the casing6.

An additional section54is added between the distributor51and the cover52. This additional section54is a volume in which a fluid under pressure can circulate. A first internal wall541of said additional section is constituted by the distributor51and a second internal wall542is constituted by the cover52.

In a broadly preferred manner, the surface of the first wall541is substantially perpendicular to the shaft2and is as large as possible.

The additional section54is preferably entirely or partly located radially outside the channels511,521and512,522along axis Y-Y′. In fact, the assembly being generally a cylinder of revolution around the axis X-X′, the more the additional section54is located radially outward, the greater the surface of the first wall541of the additional section54can be.

Preferably, the additional section is preferably located longitudinally between the cylinder block4and the two chambers511,521,512,522. Sealing means543are also provided, such as gaskets, to seal the additional section54intended to receive a fluid under pressure.

According to a preferred embodiment, the additional section54has an S or Z shape. Such a shape makes it possible to optimize the volume gain and allows the gaskets543to be housed by axial sliding. Alternatively, the additional section54is rectilinear.

The additional section54is intended to be supplied with a fluid under pressure via a supply channel55positioned in the cover of the distributor. Thanks to the surface area of the first wall541, the fluid under pressure exerts a force co-linear with the axis X-X′ on the distributor51. The distributor51being in contact with the cylinder block4through the contact surface53, the force is transmitted to the cylinder block4which engages itself on the shaft2.

The force induced by the fluid under pressure on the distributor51, indirectly on the cylinder block4, being proportional to the surface area of the first wall541, the maximization of this surface area allows the minimization of the pressure of the fluid, with a constant force.

According to a first embodiment (FIGS. 2band 3a), the additional section is supplied by the lowest pressure of the two hydraulic supply circuits71,72. As previously mentioned, the two hydraulic circuits71,72can be low or high pressure depending on the operating mode of the hydraulic device1. The two hydraulic supply circuits71,72are coupled to a selector9, said selector9being coupled to the additional section54through the supply channel55. The selector9is adapted to select the lowest pressure between the two hydraulic supply circuits71,72. The inputs to the selector9are connected to the two hydraulic circuits71,72, each of which can be high pressure or low-pressure. The output of the selector9is connected to the supply channel55.

Preferably, the selector9is a selector with an open center: in fact, in particular during starting of the hydraulic device, the two hydraulic circuits71,72are brought to a boost pressure by the pump7so-called a booster pump, shown schematically (FIGS. 3aand 3b) as a hydraulic pump. The pressures in the two hydraulic circuits71,72being at that moment almost equivalent, the selector9with an open center will allow the supplying of the additional section54immediately upon starting of the hydraulic device1.

The supply channel55links the selector9to the additional section54. For reasons of use of space, said supply channel55is located advantageously entirely or at least in part in another plane than the additional section54(supply channel55shown in dashes inFIG. 2b).

According to a second embodiment (FIG. 3b), the additional section54is directly supplied by the booster pump7via the supply channel55.

The concerned hydraulic devices1typically have radial pistons42and multilobe cams3. In particular, when the device1is in the free wheel configuration, the pistons42are held in contact with the cam3by compression springs.