DE3224189A1 - HYDRAULIC SYSTEM WITH ELECTRICAL PROPORTIONAL CONTROL - Google Patents

Description

Patent Attorneys 322-189

Dipl. Ing. H. Weidmann, Dipl. Phys. Dr. K. Rod » June 2, 1982

Dipl. Ing. F. A. Weidmann, Dipl. Chetn. B. Hubor

Dr.-Ing. H. Liska Mßhlstrafc 22, MOO MHidien Se

CENTRO RICSROHS PIAT S.p.A.

Strada Torino 50 WA

Orbassano (Torino) / Italy

Hydraulic system with electrical proportional control

The invention relates to a hydraulic system with electrical proportional control

with a hydraulic servo valve that has a control chamber and a hydraulic control valve for the modulation of the pressure in the control chamber, the control valve comprising the following parts

- a valve body with

A line which communicates with the control chamber and is connected to a fluid pressure source via a throttle opening is,

- An outlet opening which can be connected to a drainage container is

- and a passage for connecting said line to the outlet opening,

- A closure member with one in the valve body the seat formed in the area of said passage cooperates,

- an electromagnet with

- an armature that is firmly connected to the valve body,

- one winding

- And a movable core, which the closure member with one of the intensity of the flowing through the winding Current pushes proportional force in its closed position against the seat.

Such control valves are used in devices of various types, e.g. in presses, machine tools, machines for rubber processing, metallurgical plants, machines for plastic processing and in general in all Cases where pressure modulation in a hydraulic circuit is desired.

With control valves of the type described, by changing the intensity of the feed current of the winding of the Electromagnets achieve a proportional change in pressure in the control chamber of the servo valve. The change namely, the current intensity causes a proportional change in the force with which the closure member that the Connection of said line to the drainage tank controls, is pressed against his seat.

The known control valves for pressure modulation, however, have a comparatively complicated construction expensive, heavy and bulky. They are therefore poorly suited for use in automotive technology and in particular, for example, in braking systems, in power transmission systems and in feed systems for vehicle engines.

The invention is based on the object of creating a hydraulic system with electrical proportional control, in which the aforementioned disadvantages are eliminated.

Based on a system of the type described above this task is solved by

- That the seat cooperating with the closure member lies in a zone of the valve body which is in the interior of the armature of the electromagnet is located,

- and that the valve member is driven directly by the movable core of the electromagnet.

A valve with these characteristics has a simpler one Structure, consists of fewer individual parts, can be

Produce cheaper, is less bulky and lighter compared to known valves of this type. In these known valves is namely the seat for the closure member that connects to the drainage container controls, in a zone of the valve body, which is located outside of the armature of the electromagnet, and that with the seat cooperating closure member is from the movable core of the electromagnet indirectly via elements controlled axially between the movable core and the closure member.

Advantageous refinements and developments of the invention are the subject matter of the subclaims, to which herewith express reference is made to shorten the description.

According to one of these developments, the part of the valve body that protrudes from the electromagnet is located in a seat formed in the body of the hydraulic servo valve and thus forms the connection of the servo valve with the control valve.

As a result of the properties mentioned, the valve body fulfills of the control valve has several functions at the same time: It forms both the actual valve body (in which the named line and the seat for the closure member are formed), as well as the connecting element with the Servo valve. In addition, the valve body of the control valve is preferably made of ferromagnetic material and thus attracts the moving core of the electromagnet when the winding is excited.

The invention is explained in more detail below with reference to the drawings:

Fig. 1 shows a partial section of a first embodiment of the hydraulic system according to the

finding,

Fig. 2 shows a partial section of a second embodiment of the system according to the invention,

Fig. 3 shows a diagram showing the pressure-current characteristic reproduces a practical embodiment of the control valve.

In Fig. 1, the body of a hydraulic servo valve is denoted by 1. It has a cylindrical seat 2 in which part of the valve body 3 of a control valve is mounted. The valve body 3 has a cylindrical shape and is made of ferromagnetic material. The control valve also comprises an electromagnet k with a winding 5 carried by a tubular bobbin 6. This bobbin 6, which consists of non-ferromagnetic material, is located inside an armature made of ferromagnetic material which comprises a cup-shaped element 8 with a bottom wall 8a, which is provided in the region of its open side with a plate 9 which has a central opening. Between the end of the bobbin 6 and the bottom 8a on the one hand and the plate 9 on the other hand there are annular plates 10. Both the cup-shaped element 8 and the plates 9 and 10 are made of ferromagnetic material.

Inside the bobbin 6 is a socket 11 made of niehtferromagnetisehem material with the interposition of a bushing ferromagnetic core 12 slidably mounted.

That end region of the valve body 3 which is the end region inserted into the seat 2 of the body 1 of the servo valve opposite is in the interior of the plate 9, the plate 10 adjacent to it and the corresponding end region the sleeve 11 is mounted.

The valve body 3 of the control valve is axially penetrated by a line 18, which with one of its ends

Λ-

a control chamber 14 is in communication, the pressure of which is to be modulated with the aid of the control valve. The administration 18 protrudes through an opening 23 with a narrow cross-section and small axial extent with a radial opening 21 in FIG Compound that is worked out of the valve body 3. This opening 21 is in turn connected to one in the body 1 of the hydraulic servo valve formed opening 22 in communication, which is connectable to a fluid pressure source.

The valve body 3 also has an opening 15 which Via an annular chamber 16 which is delimited in the interior of the seat 2 by a circumferential groove in the valve body 3 is in communication with an opening 17 of the body 1 of the servo valve, which in turn is connected to a drainage container connected is.

The valve body 3 also includes a passage for connecting the line 17 to the outlet opening 15. This Passage comprises a main chamber 19 (which is inside the socket 11 from the two opposite end regions the body 3 and the movable core 12 is limited), in the interior of which that end of the line 18 opens, which faces away from the control chamber 14, as well as at least one auxiliary line 20, which the main chamber 19 connects to the outlet opening 15.

The valve body 3 is mounted inside the seat with the interposition of a series of annular seals 24, which are inserted in similar peripheral grooves of the valve body 3. The latter also owns outside of the Body 1 has a peripheral groove 25 in which a bracket 26 fastened to the body 1 with screws 27 engages which the valve body 3 of the control valve is fixed to the body of the servo valve.

In that end of the line 18 which opens into the main chamber 19, a sealing sleeve 28 is mounted, which

with its inner edge facing the chamber 19 forms a seat for a closure member in the form of a ball 29. That Closure member 29 is pressed by the movable core 12 of the elec tromagneten against its seat when the winding is excited.

In the end of the bush 11 opposite the valve body 3, a sealing plug 30 is inserted with an oversize. This closure plug 30 is provided with a peripheral groove in which a retaining ring 31 engages, the one Spacer ring 32 touches.

The closure plug 30 limits together with the one facing it End of the movable core 12 an auxiliary chamber 33 inside the socket 11. This auxiliary chamber 33 is with the Main chamber 19 connected by a series of axial grooves 3 ^, which are formed on the periphery of the movable core 12. The latter also has a middle section of reduced diameter, which has an annular chamber

35 determined. As a result of the structure described above, forms in the area of the chamber during operation 35 from a fluid film, which acts as a cushion and the sliding of the core 12 in the interior of the sleeve 11 favors.

The body of the movable core 12 is penetrated by an axial bore into which a mandrel 36 is inserted with an oversize which protrudes from the body of the core 12 at both ends. That portion of the mandrel 36 from the end of the core 12 facing the chamber 33 protrudes, prevents the opposing surfaces of the core 12 and the plug 30 can touch each other, so that the risk of hydraulic sticking these surfaces is avoided. The thorn

36 is made of non-ferromagnetic material with a Hardness much greater than that of the movable core 12.

In the area of that end of the mandrel 36 that comes out of the body of the movable core 12 protrudes in the direction of the main chamber 19, the core 12 has a recess 37 for receiving the spherical locking member 29.

Between the opposite ends of the plug 30 and the movable core 12 is a coil spring 38, whose function from the later Description is evident.

In the area of the end of the line 18 opening into the control chamber 14 there is a perforated diaphragm 39 which prevents that possible pressure oscillations in the line 18 are transmitted into the chamber 14 and vice versa.

is

With 40 denotes an element firmly connected to the movable member of the servo valve. This element 40 is the in the chamber 14 is exposed to the pressure prevailing, so that its position changes when the pressure in this chamber 14 varies. In Fig. 1, the designated 41 inlet port of the servo valve is also shown, which with an outlet opening (not shown) via one controlled by said movable member of the servo valve Passage communicates.

The function of the hydraulic system shown in Fig. 1 is explained below:

The position of the element 40 connected to the movable member of the servo valve is a function of the figure shown in FIG the control chamber 14 pressure prevailing. This pressure is above that developed in the body 1 of the servo valve Opening 22, the narrow cross-section 23 of the opening 21 formed in the body 3 of the control valve and the conduit 28 transferred to the chamber 14.

The closure member 29 designed as a ball is of the

movable core 12 of the electromagnet 4 against its seat printed when winding 5 is energized.

If the pressure in the line 18 becomes large enough to the To overcome force exerted by the movable core 12 on the shutter member 29, the shutter member moves 29 together with the movable core 12 upwards (with reference to FIG. 1) and places the conduit 18 over the main chamber 19 and the auxiliary line 20 with the opening 15 leading to the drainage container in connection.

The pressure prevailing in the line 18 (and consequently in the chamber 14) is consequently a function of that of the movable core 12 exerted on the shutter member 29.

By changing the intensity of the current supplied to the winding 5, the current in the chamber 14 can be changed Modulate pressure (which changes the position of the moving part of the servo valve).

The structure described above and in particular the fact that the seat for the closure member formed as a ball 29 is formed in a zone of the body of the control valve which is inside the winding 5 of the electromagnet 4 lies, as well as the fact that this shutter member 29 is directly from the movable core 12 of the electromagnet controlled without the help of elements axially between them allow the creation of a valve, which is simpler, cheaper and less bulky than known control valves with electrical proportional control.

FIG. 2 (in which the parts common to FIG. 1 are provided with the same reference numerals as there) shows a second embodiment of the invention, which differs from the embodiment shown in Fig. 1 only there-

differs by the fact that the throttle opening, via which the line 18 is in communication with the fluid pressure source, is not formed in the body 3 of the control valve but in the servo valve. In addition, it is omitted in this exemplary embodiment the pinhole 39-

The throttle opening, which is shown in Fig. 2 with the reference number 42 is provided, is formed in the wall of the element 40 in such an area that the control chamber 14 is located between the opening 42 and the line 18. The opening 42 communicates with an opening 43 of the body 1 of the servo valve in connection to which the fluid pressure source can be connected.

The function of the valve shown in FIG. 2 corresponds to that of the valve according to FIG. 1.

A theoretical analysis of the function of the hydraulic system according to the invention in the embodiment according to FIG Fig. 1 allows the determination of the criteria for the dimensioning of the control valve, which is a reversible unambiguous Relationship between the intensity of the current flowing through the winding 5 and the pressure in the line 18 (a unique pressure value must correspond to each current value) and ensure the stability of the system.

First of all, the following parameters must be set:

P = feed pressure of the control valve (at the inlet opening 22), Q = ideal maximum flow rate for the control (ideal condition results when the pressure in line 18 becomes zero),
ξ = density of the fluid,

E = P '/ P, where P ^{1 is} the max max max on which the design is based

te maximum pressure in the area of the line 18, = ^pI _m - _n / ^p j where P ¹ . the design is based on the minimum pressure in the area of the line 18,

I = current corresponding to the pressure P ' _ax (the action of the spring 38 is neglected),

R = inner radius of the bush 11,

t = wall thickness of the bush 11,

w = wall thickness of the anchor in the area opposite the core 18 (thickness of the plate 10 + thickness of the bottom 8a),

/ 9 2

O = I / 1 - d / D, where d and D are the diameter of the ocs s

tion of the socket 28 or the diameter of the closure member 29 designed as a ball.

In addition, the experimentally determined values of the following coefficients are required:

V = scattering coefficient of the electromagnets, μ - permeability in air,

c = discharge coefficient for the narrow cross-section 23, c = outflow coefficient for the from the closure member 29

controlled passage as well

Discharge:

Socket 28.

c '= coefficient of discharge for the passage inside the

Once the parameters specified above are fixed, leave the characteristic dimensions of the valve in the following way:

(d "= diameter of opening 23)

D = d _s /

s' d _s

(1 - maximum distance of the core 12 from

11 '£

* s valve body 3),

NI R - 's ° * i / -JL. ^{1 +}

I RjCtA V 32 ^

max S

where N is the number of turns of the winding 5 of the electromagnet 4.

The relationship last mentioned is the value of a product of three sizes, so that it is always possible select any two values of these quantities and determine the third.

1 + \ l E
h Yw ^m ift If max V Rt

⁼ H ' f - Vx " ^2w '

where h is the distance between the movable core of the solenoid and the valve body when the shutter member 29 is pressed against its seat.

In the case of the last relationship I wrote, it goes without saying It is necessary to choose values for t and w such that no negative values for h result.

Finally, I_ also applies. = 1

'.min "' max» - ■ = - ... - E

(1 - l / E) (1 - / E.) ^V ι max ι mm '

min y ¹ "" max "1 + \ ΓΈ

Max

where I. is the value of the current corresponding to the pressure P '. mm min

is equivalent to.

In practice, it is advisable to choose a value for the maximum stroke X of the movable core of the electromagnet, which is greater than the value given by the above relationship in order to take account of the working tolerances wear and gain greater flexibility in the use of the control valve in the event that larger feed pressures occur as they are based on the design.

The assumption of a value for the maximum stroke X, the largest

This is more than the theoretical value, on the other hand, can lead to a reduction in the electromagnetic force for a given Current, so that there is a risk that the moving core will not be able to do so due to the friction in the system is to get moving. It would be a mistake to solve this problem by increasing the intensity of the supply current want to solve, as this would lead to a sharp increase in pressure oscillations in the line 18 is accompanied.

The solution to this problem is the task that between the plug 30 and the movable core 12 arranged coil spring 38. When the distance between the movable core 12 and the body 3 of the valve is the largest, this coil spring forms a sufficiently large Load to equalize the minimum pressure in line 18.

As a result, when the minimum design pressure is in line 18, it will be controlled by the Spring 38 is fully balanced and the intensity of the current supplied to the coil of the solenoid is essentially equal to zero,

The use of the spring 38 also results in shorter consultation times and increases the stability of the system. The valve body 3 can also consist of non-ferromagnetic Material. In this case, however, it is essential that the movable core 12 not be in the central Position is located inside the winding 5 when the closure member 29 presses against the seat.

The following is a dimensioning example for the embodiment of the control valve shown in FIG. 1 specified:

Design data:

^J min

Max

^Ε π R tw

Max

200 Nw / cm 20 cm / sec;

9.10 " ⁶ Nw sec ² / cm ⁴ ; 0.02; 0.99; 0.7 cm; 0.1 cm; 0.3; 1 Amp.; 0.8.

Experimentally determined sizes:

C s

1.26.10 ⁶ Nw / (AW value) ² 1.3; 0.78; 0.55; 0.66.

The following characteristic quantities result:

^d s D 1 N h

min

P 'max

P 'mm

0.07 cm; 0.2 cm; 0.33 cm; 0.075 cm; 554 0.063 cm; 0.094 amps;

198 Nw / cm ² ;

2 4 Nw / cm

Fig. 3 illustrates the pressure-current characteristic of the practical tables embodiment of the shown in FIG Valve.

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Claims (16)

Claims O Hydraulic system with electric proportional control with a hydraulic servo valve which has a control chamber (14) and a hydraulic control valve for the Modulating the pressure in the control chamber (14), the control valve comprising the following parts - A valve body (3) with - A line (18) which communicates with the control chamber (14) and is connected to a fluid pressure source via a throttle opening (23; 42), - An outlet opening (15) connected to a drainage container is connectable, - and a passage (19, 20) for connecting said line (18) to the outlet opening (15), - A closure member (29) which is connected to a valve body (3) in the area of said passage (19, 20) trained seat cooperates, - An electromagnet (4) with - An armature (7), which with the valve body (3) of the Control valve is firmly connected, - a winding (5) - And a movable core (12) which the closure member (29) with one of the intensity of the through Winding (5) pushes the current proportional force into its closed position against the seat, characterized, - That the seat cooperating with the closure member (29) lies in a zone of the valve body (3) which is inside the armature (7) of the electromagnet (4) - and that the closure member (29) is driven directly by the movable core (12) of the electromagnet (4) is. 2. System according to claim 1, characterized in that that the throttle opening (23) provided for connecting the line (18) to the fluid pressure source in the Body (3) of the control valve is formed. 3. System according to claim 1, characterized in that - That the throttle opening (42) provided for connecting the line (18) to the fluid pressure source in the hydraulic servo valve is formed - and that the control chamber (14) lies between said line (18) and the throttle opening (42). 4. System according to claim 1, characterized in that that the throttle opening (23; 42) is a relatively limited has axial extension. 5. System according to claim 1, characterized in that - That the movable core (12) of the electromagnet (4) is slidable inside one of the winding (5) carrying tubular bobbin (6) is mounted, - That the body (3) of the control valve is essentially cylindrical and has an end region is located in the interior of an end area of the coil former (6), - That this end region of the body (3) of the control valve together with the opposite end of the movable core (12) inside the bobbin (6) delimits a main chamber (19), - That the line (18) formed in the body (3) of the control valve opens into the main chamber (19), - That said passage connecting the line (18) to the outlet opening (15) from the main chamber (19) and at least one auxiliary line (20) is formed, which the main chamber (19) with the outlet opening (15) connects, - and that the seat for the closure member from the end region of the line (18) opening into the main chamber (19) is formed. - 16 - 6. System according to claim 5, characterized in that the body (3) of the control valve made of ferromagnetic Material. 7. System according to claim 5, characterized in that the movable core (12) with the interposition of a Socket (11) is slidably mounted in the interior of the bobbin (6) of the winding (5). 8. System according to claim 7, characterized in that - That the valve has a closure element (30) which faces away from the body (3) of the control valve End of the socket (11) and together with the the opposite end of the movable core (12) delimits an auxiliary chamber (33) inside the bushing (11), - and that the movable core (12) has on its periphery a series of axial grooves (34) which form the main chamber Connect (19) to the auxiliary chamber (33). 9. System according to claim 8, characterized in that a central section on the movable core (12) is formed with a reduced diameter, which inside the bushing (11) has a peripheral annular chamber (35) limited. 10. System according to claim 8, characterized in that between the closure element (39) and the opposite of it End of the movable core (12) elastic means (38) are arranged. 11. System according to claim 8, characterized in that the end of the path determining means (36) for limiting the end position of the movable core (12) when it moves in the direction of the closure element (30) are and that in this end position the opposite ends of the movable core (12) and the Closing element (30) have a distance from each other. 12. System according to claim 11, characterized in that that the means for limiting the travel consist of an axial mandrel (36) which is press-fitted into the movable Core (12) is used. 13. System according to claim 5, characterized in that the seat for the closure member (29) is determined by the inner edge of a bushing (28) which is mounted on the body (3) of the valve in the end region of the line (18 f which opens into the main chamber (19). 14. System according to claim 5, characterized in that the part of the body (3) of the control valve which consists of the electromagnet (4) protrudes outwards, inserted into a seat (2) of the body (1) of the hydraulic servo valve is and thus forms a connection between the servo valve and the control valve. 15. System according to claim 5, characterized in that the line (18) consists of a bore which the The body (3) of the control valve penetrates axially. 16. System according to claim 5, characterized in that the end of the line (18) which with the control chamber (14) is connected, is provided with a perforated diaphragm (19), which the transmission of any pressure oscillations from the line (18) in the control chamber (14) and reversed prevented.