US2877787A

US2877787A - Hydraulic servo-action system

Info

Publication number: US2877787A
Authority: US
Inventors: Brueder Antoine
Original assignee: Andre Citroen SA
Current assignee: Automobiles Citroen SA
Priority date: 1956-09-14
Filing date: 1957-02-01
Publication date: 1959-03-17
Anticipated expiration: 1976-03-17
Also published as: BE553338A; NL94627C; FR1158559A; LU34822A1; NL212944A; DE1083127B; GB811247A

Description

March 17, 1959 A. BRUEDER 2,877,787

HYDRAULIC SERVO-ACTION SYSTEM Filed Fba 1, 1957 3 Sheets-Sheet 1 ZZB March 17, 1959 A. BRUEDER HYDRAULIC SERVO-ACTION SYSTEM 5 Sheets-Sheet 2 Filed Feb. 1, 1957 T 'l fif.

United States atent HYDRAULIC SERVO-ACTION SYSTEM,

Antoine Brueder, Paris, France, assiguor to Soeiete Anonyme Andre Citroen, Paris, France Application February 1, 1957, Serial No. 637,772

Claims priority, application France September 14, 1956 2 Claims. (Cl. 137-118) The present invention relates to improvements in or relating to hydraulic servo-action circuits of the type adapted to be associated with or incorporated in hydraulic systems, notably hydraulic suspension systems of automotive vehicles.

In a hydraulic servo-action installation or circuit it is necessary to provide in conjunction. with the pump an accumulator for the fluid under pressure; therefore, meansmust be provided for controlling the pump output to keep the accumulator pressure within predetermined limits and permitting during the inoperative periods a zeropressure pump output.

An installation without accumulator may be contemplated if the pump is capable of delivering the necessary instantaneous load output; nevertheless, an apparatus of generally delicate design is necessary for controlling the pressure.

In certain cases, circulation systems may be used and this solution is extremely simple when only one apparatus is to be actuated, but special and costly arrangement must be provided when two or more receivers are used.

Now it is the essential object of this invention to provide a hydraulic servo-action system of the fluid-circulation type which comprises a reservoir, a feed pump and two distributors each adapted to control the operation of one receiver and to be controlled separately, this arrangement being characterized in that a selector is interposed in the feed circuit between the pump and the distributors for automatically stopping the supply of fluid to the first distributor when the other distributor is operative and the first one is inoperative, and restoring the supply of fluid to the first distributor if the latter is operated whereas the other distributor is already operative, the functions of both distributors being reversible.

With this purpose in view, the selector incorporated in the system according to this invention comprises a body having formed therein a plurality of ducts, i. e. one inlet duct and two outlet ducts, these three ducts leading into a cylindrical cavity formed in said body and provided with a distributing member of the slide valve type; the two ends of this slide valve are shouldered to a smaller diameter than the bore of said cavity and project in two side chambers each containing a calibrated compression spring urging the slide valve in its intermediate position; moreover, a selection duct leads into each of these side chambers.

Each distributor comprises essentially a body having formed therethrough a plurality of passages leading into a cylindrical axial cavity provided with a distributor of the slide valve type; these passages constitute the inlet, pump by-pass, selection, load. and exhaust ducts, respectively. Moreover, the distributor comprises a retarding passage of gauged diameter interconnecting two cavities in which the two ends of the slide valve are slidably fitted.

The inlet, outlet and selection ducts are connected to the pump, and to the corresponding inlet and selection ducts of the distributor. Finally, the pump by-pass duct provided in each distributor is connected to the fluid reservoir.

In order to afford a clearer understanding of the present invention and of the manner in which. the same may be carried out in the practice, reference will now be made to the accompanying drawings forming part ofthis specification and illustrating diagrammatically by way of ex:- ample a typical embodiment of the invention. In the drawings:

Figure 1 is a diagram illustrating the hydraulic servoaction system according to this invention, the diiferent component members thereof being shown in their inoperative positions.

Figure la is a diagram showing a distributor in its operative position.

Figure 2 is a longitudinal section taken along the axis of a distributor.

Figure 3 is a cross-section taken upon the line III--III of Fig. 2.

Figures 4, 5, 6 and 7 are simplified, fragmentary cross sections illustrating the positions of the different ducts, the sections being taken upon the lines IV--IV, V-V, Vl-Vl and VII-VII of Fig. 2.

Figure 8 is a plan view of a distributor, and

Figure 9 is a longitudinal section illustrating the selector arrangement.

In Fig. l, which constitutes a condensed, diagrammatic view of a hydraulic servo-action system according to this invention, a pump P is connected to a fluid reservoir R through a pipe line 1 and to a selector device S through another pipe line 2 in which a safety valve 3 may be interposed, if desired. The outlet ducts of selector S are respectively connected through other pipe lines 4, 5 to the inlet ducts of distributors D and D the delivery ports 26A and 26B of these distributors being connected through

corresponding pipe lines

39, 40 respectively to two

receivers

41 and 42.

The selector S (Fig. 9) comprises a. body 6 in which.

a cylindrical bore 7 adapted to receive a slide-valve distributor 8 is formed. This valve comprises two end portions 8a, 8b of a diameter smaller than that of the bore 7, two portions 80, 8d of same diameter as the bore 7, and an intermediate portion 8ev of same diameter as the end portions 812, 812. An inlet duct 9 connected through the pipe line 2 to the pump P leads into the bore 7 and its axis is coincident with the central trans verse plane of this bore, as shown.

Other ducts

10 and 11 connected through the pipe lines 4 and 5 to the inlet ducts of distributors D and D respectively lead into the intermediate portion of the cavity 7. Each

duct

10, 11 is chambered and adapted to receive a ball 10a, 11:: acting as a non-return valve as will be made clear presently. The end portions 8a, 8b of the slide valve emerge in

chambers

12 and 13 respectively. Calibrated springs 14, 35 hearing against the outer bottoms of these chambers tend to keep the slide valve 8 in its central or intermediate position as shown in Fig. 9 by

engaging discs

16, 17 bearing on the outer faces of portions and 8d of the slide valve, respectively. The

chambers

12, 13 communicate with selection ducts l8, 19 respectively, and the latter are connected through pipe lines 20, 21 (Fig. l) to the selection ducts of distributors D and D respectively- As illustrated in Fig. 9, the safety valve 3 may be. mounted on the. body 6 instead of being inserted in the line leading from the pump P.

The distributors D and D are identical and their in ternal structure will now be described with reference to Figs. 2 to 8.

The distributor comprises essentially a body 22 havi ng.

gowns":

formed therein an axial cylindrical cavity 23 in which a slide valve 24 is slidably mounted, as shown. This slide valve 24 comprises two end portions 24a, 24b and two

intermediate portions

24c, 24d all of which have a smaller diameter than the bore of the cavity 23, and three

portions

24e, 24f, 24g of same diameter as the aforesaid bore. A number of ducts lead into or from the cavity 23, i. e. the exhaust duct 25 (Fig. 3), the load duct 26 connected to the receiver, the selection duct 27 connected to the corresponding pipe line 20 or 21 (Fig. and the pump by-pass duct 28 leading to the reservoir R (Fig. 6). The inlet duct 29 communicates with the cavity 23 through an annular channel 30 and a duct 31 (Fig. 7) and through a longitudinal channel 32 and an annular channel 33 with the selection duct 27 in the inoperative position of the slide valve 24 (Fig. 1), and also with the axial cavity 23 through the duct 31a (Fig. 5). The distributor body has also formed therein a duct 34 of gauged diameter for interconnecting the end chambers 35 and 36. The purpose of this duct 34 is to retard the circulation of fluid between these chambers 35 and 36 when the slide valve 24 is moved within the bore 23 by adequate means (not shown).

The operation of the hydraulic servo-action system according to this invention will now be described with reference to the diagram of Fig. 1.

The

receivers

41 and 42 fed with fluid through the distributors D and D may constitute, as shown diagrammatically in Fig. 1, the front and rear correctors respecti vely of a hydraulic or hydro-pneumatic suspension system of a vehicle. These correctors are designed to modify the level of the suspension as a function of the load so as to keep this level to a constant value.

' Under normal conditions the different slide valves 8 of the selector S, 24a of distributor D and 24b of distributor D are in their inoperative positions as illustrated in Fig. 1. Thus, the fluid circulates normally through the following circuit, in the case of the distributor D,: reservoir R, pipe line 1, pump P, pipe line 2, cavity 7, valve a, duct 10, pipe line 4, duct 29 (Fig. 7), channel 30, duct 31, axial cavity 23, duct 28, return pipe line 37. Through the channel 32, annular channel 33, duct 27 and pipe line 21, the chamber 13 of selector S is then at low pressure. A similar circuit is established through the pipe line 5, distributor D and return pipe line 38; the pressure in the chamber 12 of selector S is the same as in chamber 13. If the distributor D is actuated, that is, if the slide valve 24a is moved to the lefthand side of Fig. 1 (for example to correct the rear suspension) the circuit passing through the distributor D will be established as follows (Fig. 1a): inlet duct 29, annular channel 30, channel 32, cavity 23 and load duct 26. Under these conditions, the fluid pressure increases to overcome the resistance of the load device or receiver. However, if the selector device S were not provided, the fluid pressure could not rise due to the low-resistance circuit remaining open through the distributor D as the latter is not actuated. Now, as the piston 24a was moved to the left the pump by-pass duct 28 was thus closed, the pressure in the cavity 23 rises instantaneously due to the resistance offered by the receiver 41 thus inserted in the circuit. This brief increase in the hydraulic pressure is transmitted immediately through the pipe line 21 to the chamber 13 of selector S; as a result, the slide valve 8 is moved quickly to the left and its portion 8d closes the duct 11. Consequently, the supply of fluid to the distributor D is discontinued and the pressure may continue to rise in the load duct 26 and the receiver may be actuated, until the slide valve 24a resumes its inoperative position. This operation may be comprised by the incomplete closing of the duct 31a which would permit an escape of fluid under no-pressure conditions through the

circuit

32, 30, 31, 29, 4, 7, and 5 and distributor D now in its exhaust position; thus, the ball valve 10a inserted in the duct 4 will close the passage and enable the fluid pressure to be set up in the aforesaid circuit and therefore also in the

elements

27, 21 and chamber 13; consequently, the piston 8 is forced to the left and the distributor D isolated from the operative circuit. As the fluid under pressure delivered from the pump P cannot flow directly towards D the pressure rises in the cavity 7 and may be transmitted through the pipe line 4 and the other distributor D to the receiver to be actuated. The fluid from the pump may flow without difficulty by lifting the previously seated ball valve 10a. As the slide valve resumes its inoperative position, the pressure in the pipe line 21, and therefore in chamber 13, drops to the initial value due to the communication established with the reservoir R through the following circuit: duct 27, annular channel 33, channel 32, duct 31, cavity 23, duct 28, pipe line 37. Thus, the slide valve 8 of selector S resumes its initial or inoperative position.

The distributor D operates in a similar manner.

Let us assume that the distributor D is already operated, so that its slide valve 24a is moved to the left, and that under these conditions the other distributor D; is also actuated. In this case the slide valve 8 of selector S has already been moved to the left and the pipe line 5 is not fed from the pump P. Consequently, the movement of the slide-valve portion 24b to the left causes the load duct 26b to communicate with the selection duct 27b. The counter-pressure exerted by the load device or receiver is transmitted through the pipe line 20 to the chamber '12 of selector S. This counter-pressure acts upon the end 811 of slide valve 8 to restore the latter in its inoperative position in which both distributors D D are fed with fluid under pressure. The fluid circulating in the pipe line 5 is then transmitted through the distributor D the load duct 26b and the pipe line 40 to the receiver 42 controlled by the distributor D The rapidity of the return movement of the slide valve 8 depends at the same time on the pressure drops in the installation, on the calibration of the various springs therein and on the pressure differential between the pump and the load or like devices associated with and controlled by this installation. In all cases, the correction times may be adjusted to be very short and the two actions may take place in succession without any inconvenience.

Although the attached drawings and the above description refer to only one typical embodiment of the inven tion, it will be readily understood by anybody conversant with the art that many modifications and alterations may be brought thereto without departing from the spirit and scope of the invention, as set forth in the appended claims.

What I claim is:

l. A hydraulic servo-action system with fluid circulation, comprising a reservoir, a pump connected to said reservoir, a first distributor and a second distributor connected in parallel to the delivery side of said pump, each of said distributors comprising a cylindrical body, an axial cavity formed therethrough, a distributor valve slidably movable in said cavity, a pump by-pass duct connected to said reservoir, an exhaust duct, an inlet duct, a selection duct, a load duct, all these ducts being disposed radially and leading into said axial cavity, a first receiver and a second receiver connected to the load ducts of the first distributor and second distributor respectively, a selection member comprising a body, a cylindrical cavity formed therethrough, an inlet duct connected to said pump, a first outlet duct and a second outlet duct connected to the inlet ducts of said first and second distributors respectively, a non-return valve inserted in each of said outlet duets, said outlet ducts being formed in said body and leading into said cylindrical cavity of said selector, a slide valve movable within said selector cavity, two widened side chambers in which the two end portions of said slide valve project, a calibrated spring in each of said chambers for keeping said selector slide valve in its intermediate position by acting on said projecting end portions, a first selection duct and a second selection duct leading into each of said chambers, respectively, and connected to the selection ducts of said first distributor and second distributor, respectively, the pressure increase occurring in the selection duct of the first distributor when the latter is actuated to feed the first receiver being transmitted to the first selection duct of the selector and producing a movement of the selector slide valve to control the closing of the second outlet duct of the selector which is connected to the inlet duct of the second distributor, the counter-pressure produced subsequently in the selection duct of the second distributor when the latter is controlled to feed the second receiver while the first receiver is already fed being transmitted in this case to the first selection duct of the selector and causing the slide valve to resume its intermediate position, the opening of the second outlet duct, and therefore, the supply of fluid to the second distributor.

2. A hydraulic servo-action system with fluid circulation, comprising a reservoir, a pump connected to said reservoir, 21 first distributor and a second distributor connected in parallel to the delivery side of said pump, each of said distributors comprising a cylindrical body, an axial cavity formed therethrough, a distributor valve slidably movable in said cavity, a pump by-pass duct connected to said reservoir, an exhaust duct, an inlet duct, a selection duct, a load duct, all these ducts being disposed radially and leading into said axial cavity, a first receiver and a second receiver connected to the load ducts of the first distributor and second distributor respectively, a selection member comprising a body, a cylindrical cavity formed therethrough, an inlet duct connected to said pump, a first outlet duct and a second outlet duct connected to the inlet ducts of said first and second distributors respectively, said outlet ducts being formed in said body and leading into said cylindrical cavity of said selector, a slide valve movable Within said selector cavity, two widened side chambers in which the two end portions of said slide valve project, a calibrated spring in each of said chambers for keeping said selector slide valve in its intermediate position by acting on said pro jecting end portions, a first selection duct and a second selection duct leading into each of said chambers, respectively, and connected to the selection ducts of said first distributor and second distributor respectively, the pressure increase occurring in the selection duct of the first distributor when the latter is actuated to feed the first receiver being transmitted to the first selection duct of the selector and producing a movement of the selector slide valve to control the closing of the second outlet duct of the selector which is connected to the inlet duct of the second distributor, the counter-pressure produced subsequently in the selection duct of the second distributor when the latter is controlled to feed the second receiver While the first receiver is already fed being transmitted in this case to the first selection duct of the selector and causing the slide valve to resume its intermediate position, the opening of the second outlet duct, and therefore, the supply of fluid to the second distributor.

References Cited in the file of this patent UNITED STATES PATENTS 1,999,834 Ernst Apr. 30, 1935 2,624,361 Brown Jan. 6, 1953 2,799,996 Van Meter July 23, 1957