FR2532694A1 - HYDROSTATIC DRIVE COMPRISING, IN PARTICULAR, AN ADJUSTABLE PALLET PUMP - Google Patents

Abstract

THE INVENTION CONCERNS HYDROSTATIC DRIVES INCLUDING IN PARTICULAR AN ADJUSTABLE VANE PUMP, A PRESSURE LIMITER DEVICE AND AN ADJUSTING ELEMENT MOVED BY A CONTROL DEVICE AND INFLUENCING THE FLOW OF THE PUMP. ACCORDING TO THE INVENTION, THE ADJUSTING ELEMENT 3 IS A CAM RING ATTACKED ON EACH OTHER BY THE CONTROL DEVICE 9 AND THE PRESSURE LIMITER 10.

Description

The present invention relates to a hydrostatic drive

  that, comprising: a pressure relief device and a displacement pump;

  adjustable positive setting, in particular an adjustable vane pump; a control element influencing the flow rate that can be displaced by a control device between a position for which the flow rate is maximum and a zero stroke position for which the flow rate

is substantially zero.

  Hydrostatic drives are mechanical systems

  consisting of a hydraulic pump and one or more hydraulic motors, the pump and the motor (s) can be connected in open or closed circuit. When the drive speed is to vary continuously, positive displacement pumps are used.

  The pump and the motor must be equipped with a

  tif limiting the working pressure.

  In known hydrostatic drives, with variable drive speed, the pressure relief device is realized

  in the form of a separate and complicated valve arrangement.

  The present invention aims to provide, in the case of a hydrostatic drive with adjustable positive displacement pump,

  an inexpensive pressure limiting device having a construction

simple way.

  According to the invention, this object is achieved by the fact that the

  control device and the pressure relief device

  the pump control element while being located at the opposite

  The pressure limiting device is then advantageously

  an integrable module in the volumetric pump There is no need

  additional pipes and fittings, so that at the same time a simplification of the installation and a reduction

the risk of flight.

  In an advantageous embodiment, it is provided that

  the adjusting member is a cam ring against the outer periphery

  of which the control device and the

  pressure limiting devices which are arranged in opposition and in

mutual management.

  It is advantageous for the pressure-limiting device to be a spring device arranged between the cam ring and the pump body, and against the force of this spring device.

  that the cam ring can be driven to the zero stroke position.

  A mechanically displaceable control module, for example

  by means of a screw system, or with the assistance of

  an auxiliary force, is particularly simple and inexpensive.

  Hydraulically or electrically actuatable control devices

  able to remotely control the throughput and perform

  the adjustment according to predetermined reference quantities.

253,269.4

  The different objects and characteristics of the invention

  will now be detailed in the description that follows, made

  By way of non-limiting example, the invention refers to the attached figure which represents an adjustable pump, dut-ype vane, -destinine to be mounted in a hydrostatic drive with means of

  mechanical control assisted by an auxiliary force.

  In a pump housing 1 are arranged a rotor 2 and a cam ring surrounding the rotor 2 Slots 4 occupying the axial length of the rotor 2 are arranged radially therein, and

  pallets 5 are arranged in these slots, with possibility of

  With their radially outer end, the pallets are in contact with the inner periphery of the cam ring 3 and, in cooperation with the latter and with two lateral disks,

  delimit variable-volume work rooms.

  intake 6 and an outlet opening 7, for admission

  and the outlet of the pressure medium are arranged in the dis-

side issues.

  The cam ring 3 can, while receiving a lateral support

  by means of support 8, to be displaced with respect to the

  tor 2, a position of maximum eccentricity at a position where it is substantially coaxial with the rotor 2 The substantially coaxial position is called the zero position of travel On the one hand, the displacement of the cam ring 3 s' pressure depends on the pressure conditions established inside the working chambers. On the other hand, this movement can at the same time be

  caused by a control device 9.

  The displacement of the cam ring 3 as a function of the pressure is effected against the force of a spring device op 4 rant as

  pressure-limiting system, the spring-loaded device

  carries a compensating spring 11 which is supported on the one hand by

  through a set screw 12, against a housing 13 bolt-

  born on the pump body, 1, and secondly against the cam ring 3, this via an intermediate member 14 When the pressure increases, the cam ring 3 moves to the zero stroke position, while the flow decreases and the pressure increases to its maximum value

  Preset delimiting the pressure range.

  The maximum position can be adjusted by adjusting the preload of the compensating spring 11, which can be established by means of the

adjusting screw 12.

  The control device 9 for moving the cam ring 3 and thus adjust the flow is arranged diametrically in front of the spring pressure limiting device A casing 15 fixed to the body 1 of the pump has a bore 16 in which a control piston 17 is slidably arranged.

  an extension 18 by which it is applied against the cam ring 3.

  In the adjusting piston 17 is arranged a stepped bore 30 which starts from the end facing the extension 18 The initial median and end portions of the stepped bore 30 have the same diameter and guide a control spool 19 between the initial and median, as well as between the middle and end portions, the stepped bore 30 has two larger diameter regions which

  channels 22 and 23 are connected to the end faces of the adjusting piston 17.

  A fluid connection, 24, opens into the median portion of the

  The control spool 19 has an annular thinned portion, the axial length of which corresponds to that of the portion

  median, so that two "control edges" 25 and 26 are

  By connections not shown, the end faces of the adjusting piston 17 are connected to a source of pressure fluid,

  while the middle portion has a pressure fluid connection

  24, to a return tank When the control spool 19 is moved in one of the two directions indicated by

  the arrows, the adjusting piston 17 moves) under the effect of

  pressure, at the desired position. Under-effect of displacement

  cement, thus caused, the cam ring 3, the flow is changed.

  The control device 9 is the device

  10 can be adjusted so that the displaced volume is

Q 2532694

  that which is necessary, while constantly maintaining the effectiveness

  cacity of the pressure limiting device.

Claims (4)

  Hydrostatic drive comprising a pressure-limiting device and an adjustable positive-displacement pump, in particular an adjustable vane pump and an adjusting element influencing the flow rate and which, by a control device, can itself be moved between a position for which the flow rate is maximum and a zero stroke position for which the   flow rate is substantially zero, this training being   characterized in that the control device (9) and the pressure-limiting device (10) aligned and situated in opposition to one another, both attack said adjustment element (3) of the pump.   Drive according to claim 1, characterized in that   the adjusting element is a cam ring (3) against the periphery   outside of which the control device (9)   and the pressure relief device (10) which are arranged oppositio sition and alignment.   3 Drive according to claim 2, characterized in that the pressure limiting device (O) is a spring device arranged between the cam ring (3) and the pump body (1), and   what it is against the strength of this spring device that the ring-   cam (3) can be brought to the zero stroke position.   4 Drive according to one or more of the claims   previous, characterized in that the control device (9)   is operable mechanically, hydraulically or electrically.