FR2925624A1 - Hydraulic control valve system for use in e.g. material handling equipment, has actuators arranged in juxtaposed manner, where each actuator has electric motor connected to valve rod using coupling mechanism - Google Patents

Abstract

The system has hydraulic valve blocks with several control valve segments (4) arranged in a juxtaposed manner. Each segment includes a pumping duct (12), a return duct (14) and a valve rod (22) displaceable to open and close the duct (12) and to close and open the duct (14) at variable degrees according to a position of the rod. Actuators are arranged in a juxtaposed manner, where each actuator has an electric motor connected to the rod using a coupling mechanism (33).

Description

Hydraulic control valve system

The present invention relates to a valve system for controlling a hydraulic drive system.

Hydraulic drive systems are used in many mechanical loading applications, for example in construction equipment, agricultural equipment, forklifts, cranes and other hydraulically driven work systems. Hydraulic pistons driving an associated mechanical member are controlled by valves that control the flow of hydraulic fluid through a pump line and a return line to fill or empty the hydraulic piston. The degree of opening and closing of the pumping line, respectively of the return line control valves, determines the speed of movement and the position of the associated mechanical loading member. It is therefore important to ensure a certain accuracy in the opening and closing of the control valves and to reduce the sensitivity of the control valve opening to a pressure in the hydraulic system. In some conventional systems, the hydraulic valves are controlled by electromagnetic actuators in combination with a hydraulic amplifier to provide the force required to move and hold the valve stem. However, it is difficult to obtain, with these control systems, precise and rigid control of the valves. Another known means of controlling the valves is via an actuator comprising an electric motor which drives the valve control rod, as described in DE 19 948 379 or US 4,650,159.

The use of a stepper motor to actuate a valve stem is advantageous because of the high stiffness it provides to the hydraulic valve control system in addition to allowing high accuracy of opening and closing. valves via stepper motor control. However, a major disadvantage of these systems is the size of the stepper motor and the number of hydraulic valve units that can be arranged in a juxtaposed manner. In DE 19 948 379 for example, the hydraulic block has four pairs of control valves mounted in a juxtaposed manner, each control valve being actuated by an electric stepper motor connected to the valve stem via a control arm. link, each of the motors being arranged in a different orientation. In this configuration, additional valves can not be added to the valve block and the various arrangements of the various electric motors increase manufacturing and assembly costs. In view of the foregoing, an object of the invention is to provide a hydraulic control valve system with a plurality of juxtaposed valves, which is compact, economical from the point of view of the manufacture of the assembly, and which provides a precise and rigid control of the opening and closing of the hydraulic valves. A further object of the present invention is to provide a hydraulic control valve system which can be easily enlarged to include more control valves in a juxtaposed manner in a compact block.

The objectives of the present invention have been achieved through the provision of a hydraulic control valve system comprising a hydraulic valve block with a plurality of control valve segments arranged in a juxtaposed manner, each valve segment. controller comprising a first conduit, for example a pump line, a second conduit, for example a return line, and a movable valve stem adapted to open and close the first conduit, respectively close and open the second conduit at degrees variables according to a position of the valve stem, the valve system further comprising a plurality of actuators arranged in a juxtaposed manner, an actuator for each valve segment, each actuator comprising an electric motor connected to said rod respective valve valves via a coupling mechanism, each motor having a rotational and a stator having a plurality of coils positioned around the rotor, coarse midpoints of the coils defining a virtual circle around the rotor, whereby a DS / HS ratio of a DS diameter of the virtual circle defined by the midpoints of the coils of the stator divided by a total height HS of the coils in a direction parallel to an axis of rotation of the rotor is greater than 1.6. Advantageously, the actuator has a width equal to or smaller than each hydraulic valve segment so that a plurality of identical actuators can be assembled in a juxtaposed manner to actuate a plurality of respective hydraulic valves in a block of valves. compact valves while benefiting from the positional rigidity and control precision of the electric motor.

The coupling mechanism of the actuator may advantageously include a rack and a pinion, the rack being directly attached to the valve stem or forming an extension thereof.

The electric motor may advantageously be a stepping motor, the stator comprising a plurality of coils positioned around arms extending radially from the stator. The stator preferably comprises at least six coils, preferably eight. In order to obtain high precision and rigidity when moving the valve stem, the motor preferably has a large number of steps per revolution, preferably more than 100, for example around 200 steps. The large number of steps is also particularly advantageous in that it provides a very low positional hysteresis during a change of driving direction. In the embodiment shown, the rotor has about 50 teeth. Other objects and advantageous features of the invention will become apparent from the claims and the description and the following detailed figures. Figure 1a is a view of a hydraulic control valve system according to this invention; Figure 1b is a view in the direction of the arrow 1b of Figure 1; Figure 1c is a view in the direction of the arrow 1c of Figure 1b; Figure 2a is a cross-sectional view through a line 2a-2a of Figure 1; Figure 2b is a cross-sectional view through a line 2b-2b of Figure 2a; Fig. 3a is a cross-sectional view similar to Fig. 2a, except that it represents a variant of the electric actuator; Fig. 3b is a cross-sectional view through a line 3b-3b of Fig. 3a; Fig. 4a is a cross-sectional view similar to Fig. 2a except that it still represents another variant of a hydraulic actuator; Fig. 4b is a cross-sectional view through line 4b-4b of Fig. 4a; Fig. 5a is a cross-sectional view of a portion of an alternative of the hydraulic control valve system of Fig. 2a; and Figure 5b is a cross-sectional view through a line 5b-5b of Figure 5a. Referring to the figures in which a hydraulic control valve system 2 comprises a plurality of juxtaposed hydraulic control valve segments 4, each segment comprising a hydraulic valve device 6 and an actuator 8, 8 ', 8 ", 8 ". The hydraulic valve devices of the control valve segments can be provided as separate components assembled together to form a single block or alternatively can be made from a single block or from a number of of components assembled together as a single block. Each hydraulic valve device comprises a body portion 10 within which the channels 12, 14, 16, 17, 19 are disposed through which a hydraulic fluid flows. The channels comprise a first channel 12 and a second channel 14 which are intended to be connected to the hydraulic lines leading to a hydraulic piston for driving a mechanical load. The channels further include input channels 17, 19 for connection to a hydraulic pump system that provides the hydraulic pressure, and a discharge channel 16 for the hydraulic fluid return. The first and second channels 12, 14 may be respectively connected to a first line (such as a pump line) and a second line (such as a return line). The hydraulic valve further comprises a valve stem 22 slidably mounted in a valve stem cavity 28 which communicates with the channels 12, 14, 16, 17, 19. The valve stem is movable in a linear direction T along an axis 13 of the valve stem. The valve stem has reduced cross-sectional portions 24, 26 for interconnecting or disconnecting the first conduit, respectively the second conduit, with the inlet channels 17, 19 so as to open and close the first conduit 12 or the second conduit 14, for a forward or reverse movement of the hydraulic piston connected thereto. The translational position of the valve stem in the cavity determines the degree of opening or closing of the valves which in turn varies the pressure and flow of hydraulic fluid to and from the hydraulic drive system connected to the valve. valve. It is therefore important to have precise displacement and positioning of the valve stem, as well as high rigidity in maintaining and stabilizing the valve stem in any given position. This precise positioning and rigid holding of the valve stem is provided by the actuator 8, 8 ', 8 ", 8"' mounted on an actuator mounting face 21a of the hydraulic valve body 10 through which extends one end 23 of the valve stem 22. The actuator comprises a housing 30, an electric motor mounted in the housing coupled to the valve stem 22 via a coupling mechanism 33. The motor comprises a stator 32, 32 ', 32 ", 32"' rigidly fixed at the housing 30, and a rotor 36, 36 ', 36 ", 36"' rotatably mounted via bearings 41 on the stator or housing. The axis R of the rotation of the rotor extends in an axial direction A, orthogonal to the valve stem axis 13 and a major plane generally defined by the valve stem 22 and the first and second channels. hydraulic 12,14. The coupling mechanism 33 comprises a rotor gear 38 rigidly attached to the rotor as soon as it engages with a reduction gear 25 having a large gear wheel 37 and a pinion 39 mounted so as to be able to perform a gearing. rotation on an axis 43 fixed to the housing. Instead of the reduction gear, it is also possible to have a transmission belt around the rotor gear 38 and the pinion 39. The gear pinion 39 gear reducer engages a toothed rack 40 which is coupled to and aligned with the end 23 of the valve stem 22. Alternatively, the toothed rack may be integrally formed with the valve stem. Other coupling mechanisms known in the art that translate rotational movement of the rotor into a linear translation movement of the valve stem can also be used without departing from the scope of the present invention. The toothed rack 40 is supported and guided by a roller 27 bearing against a face 29 of the toothed rack opposite the pinion 39.

The actuator housing 30 generally has a parallelepipedal shape defined by opposite major faces 53a, 53b and narrow minor faces 53c, 53d, 53e, 53f, one of which is a mounting face. The housing comprises a base portion 35a, preferably a cast nonmagnetic metal alloy and a lid portion 35b. The base part comprises a cavity 52 intended to receive the stator 32 of the motor, and cavities 55a, 55b, 55c intended to accommodate the bearing 41 of the rotor and the axes 43a, 45a of the reduction gear 25 and the support roller 27 respectively. The lid part 35b can also be provided with cavities 54a, 54b corresponding to accommodate the corresponding rotor bearing 41 and the reduction gear pin 43 in a compact manner while advantageously allowing an axial assembly of the motor and the mechanism coupling with housing portions 35a, 35b. The narrow mounting face 53c of the actuator housing 30, for mounting against the mounting face 21a of the hydraulic valve body, includes a passage 56 for the valve stem 22 coupled to the toothed rack 40, the passage 56 being formed by a tubular extension 57 adapted to be received in a corresponding cavity 58 of the hydraulic valve body portion. The tubular extension 57 allows the actuator to be positioned precisely with respect to the hydraulic valve body portion and further guides and positions the valve stem end 23 accurately in the actuator.

Electrical connectors 59, 59 'extend out of the housing 30 on a narrow minor face 53e (see FIG. 2a) on the side where the first and second hydraulic channels 12 to 14 are connected, or on the minor minor face 53d opposite the mounting face 53c (see Figure 5a).

The stator of the electric motor comprises a plurality of coils 42 mounted on a magnetic circuit structure with radially and inwardly extending stator arms 34, preferably formed from laminated sheets stacked with a ferromagnetic material, for generate a variable magnetic field that drives the rotor. In the embodiment shown in Figures 2a, 2b, and 5a, 5b, the motor is a stepper motor. The rotor comprises a permanent magnet 44 in the form of a disc stuck between a pair of magnetic flux conductive discs 46, for example discs made from a stacked laminated ferromagnetic material. The stator preferably comprises at least six coils 42 arranged around the circumference of the rotor, mounted on the radially extending stator arms 34. In order to obtain high accuracy and rigidity in moving the valve stem, the stepping motor preferably has a large number of steps per revolution, preferably more than 100, for example about 200 steps. The large number of steps is also particularly advantageous in that it provides a very low positional hysteresis during a drive direction change, and a high resolution. Both the rotor and stator of the stepper motor preferably have a large number of teeth 47, preferably more than 40. The stator of the stepper motor embodiment preferably has at least six coils, but preferably eight or more.

The DS / HS ratio of the average diameter DS of a virtual circle defined by the approximate centers of the stator coils, with respect to the total height HS of block, is advantageously greater than 1.6, preferably greater than 1.7, or even greater than 2. The ratio DR / HR of the outer diameter DR of the rotor with respect to the total axial height HR of the rotor disc, the axial height being measured in the direction of the axis of rotation R, is preferably greater at 2.5 and preferably 3 or more.

In the variant of FIGS. 5a, 5b, the ratio DS / HS is approximately 1.7 while in the variant of FIGS. 2a, 2b the ratio DS / HS is approximately equal to 2.2.

The aforementioned ratios allow the actuator to have the thickness H the same or smaller than the width of the conventional hydraulic valve segments, which are usually about 40 mm wide, while providing the required torque and stability for moving the valve stem to typical pressures found in valve control systems for agricultural equipment, forklifts, construction equipment and the like. The electric actuators can thus be assembled identically and juxtaposed on any plurality of hydraulic valve segments of a hydraulic valve block. In the embodiment shown in FIGS. 3a and 3b, the motor of the electric actuator is a brushless DC motor comprising a ferromagnetic stator 32 'with a plurality of stator arms or poles 34' directed radially and inwardly. . The coils 42 'are mounted spaced around the periphery of the rotor on some of the poles 34'. The rotor 36 'comprises an annular permanent magnet 44' which has a plurality of adjacent alternately polarized segments. The brushless DC motor generates a lower torque than the stepper motor variant illustrated in Figs. 2a, 2b, but the rotor 36 'rotates at a higher speed such that the gear ratio of the gear system acting on the rack 40 is greater than the gear ratio of the coupling mechanism of the stepper motor actuator. In view of the higher gear ratio, the reversibility of the hydraulic system (in situations where the electric motor is stopped) is not as good as with the stepper motor. Some applications, however, do not require reversibility in the event of a power failure or for other reasons, and in some applications reversibility may not be desired. Referring now to Figures 4a and 4b on which there is shown another embodiment in which the electric actuator comprises a variable reluctance motor comprising a ferromagnetic stator 32 "having a plurality of stator arms or poles 34" directed radially and 42 "coils are mounted in. In the case of a variable reluctance motor, the rotor 36" comprises a ferromagnetic body with a plurality of radially and outwardly directed poles 48, the number of poles. rotor being smaller than the number of stator poles. The stator coils generate a variable magnetic field that generates the equivalent of a rotating magnetic field attracting the rotor poles 48. In view of the fact that the variable reluctance motor generates no magnetic resistance when the power supply is stopped, the motor has a high reversibility and can therefore advantageously be used in applications where reversibility is desired. The height L of the actuator (i.e., the distance between the minor faces 53e and 53f) may advantageously be approximately equal to the height of the hydraulic valve body, so that the opposite minor faces 53e, 53f of the actuator do not extend substantially beyond the corresponding faces 21b, 21c of the hydraulic valve body. In the variant of FIGS. 5a, 5b, the hydraulic connector 59 ', for the connection of a drive and external power supply unit to the motor, projects from the minor face 53d, opposite to the mounting face 53c, allowing easy and convenient access to the connectors.

Advantageously, the electric motor actuators, which provide positional stiffness and control precision, have thicknesses equal to or less than those of each hydraulic valve segment so that a plurality of identical actuators can be assembled from each other. in a juxtaposed manner for actuating a plurality of respective hydraulic valves, thereby forming a compact but still efficient hydraulic valve block system. Of course, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without departing from the scope of the invention. .

Claims (14)

A hydraulic control valve system (2) comprising a block of hydraulic valves with a plurality of control valve segments (4) arranged in a juxtaposed manner, each control valve segment (4) comprising a first pipe ( 12), a second pipe (14), and a displaceable valve stem adapted to open and close the pipe (12), respectively closing and opening the second pipe (14) to varying degrees depending on a position of the rod (28), the valve system (2) further comprising a plurality of actuators (8, 8 ', 8 ", 8"') arranged in a juxtaposed manner, an actuator (8, 8 ', 8) ", 8" ') for each valve segment (4), each actuator (8) comprising an electric motor connected to a respective said valve stem (22) via a coupling mechanism (33), each motor having a rotor (36, 36 ', 36 ", 36"') and a stator (32, 32 ', 32 ", 32"'), whereby a rotor rt DS / HS, DS '/ HS', DS "/ HS", DS "'/ HS"' of mean diameter DS, DS ', DS ", DS"' of a virtual circle through midpoints of coils (42) of the stator (32, 32 ', 32 ", 32"') divided by a total height HS, HS ', HS ", HS"' of the coils (42) in a direction parallel to an axis rotor rotation (36, 36 ', 36 ", 36"') is greater than 1.6. 2. Hydraulic control valve system (2) according to claim 1, characterized in that the ratio DS / HS, DS '/ HS', DS "/ HS", DS '' / HS "'is greater than 1 7. Hydraulic control valve system (2) according to claim 1, characterized in that the ratio DS / HS, DS '/ HS', DS "/ HS '', DS '' / HS '' is greater than 2 . Hydraulic control valve system (2) according to claim 1, characterized in that the coupling mechanism (33) comprises a rack (40) connected to and extending from one end (23). of the valve stem (22) engaging a pinion mounted in the actuator and driven by the rotor. Hydraulic control valve system (2) according to claim 1, characterized in that the hydraulic valve block comprises more than four segments (4) of juxtaposed hydraulic control valves and associated actuators. Hydraulic control valve system (2) according to claim 1, characterized in that the motor is a stepper motor and the stator comprises six or more coils (42) arranged on radially extending arms (34). of the stator. Hydraulic control valve system (2) according to claim 6, characterized in that the stator comprises at least eight coils. Hydraulic control valve system (2) according to claim 6, characterized in that the motor has more than 100 steps per revolution. Hydraulic control valve system (2) according to claim 1, characterized in that the motor is a brushless DC motor. Hydraulic control valve system (2) according to claim 1, characterized in that the motor is a variable reluctance motor. Hydraulic control valve system (2) according to claim 1, characterized in that the actuators are mounted against a mounting face of each hydraulic valve block control valve segment (4) through which one end (23) of the respective valve stem (22). Hydraulic control valve system (2) according to claim 1, characterized in that the control valve segment (4) and the corresponding actuators have a width of less than or equal to 40 mm. Hydraulic control valve system (2) according to claim 1, characterized in that each actuator comprises a housing (30) having a base portion (35a) and a lid portion (35b), the base portion ( 35a) being cast from a non-magnetic alloy and including cavities (52) for receiving the stator and pins (43) supporting a reduction gear (25) of the coupling mechanism (33). Hydraulic control valve system (2) according to claim 13, characterized in that the actuator housing (30) comprises a tubular extension (57) extending from a narrow mounting face (21a), extension that can be received in a corresponding cavity (52) in the hydraulic valve segment (4) through which the valve stem (22) extends.