Hydraulic distributor with screw drive

Description of the invention

The subject of the invention is a hydraulic distributor with a screw drive intended for control in hydraulic systems particularly exposed to the influence of external mechanical vibrations occurring in mobile devices, work machines and special vehicles.

With the use of previously known hydraulic directional control valves, the effects of external mechanical vibrations on the directional control valve body are known, primarily in the directional control valve slide axis. In a typical hydraulic directional control valve, the return springs and the directional control valve's electromagnetic drive also cause the directional control valve slide to vibrate. This manifests itself through an unstable directional control valve position and pulsating flow and pressure in the hydraulic system.

Polish patent description PL210528 describes the use of a screw mechanism in the spool of a hydraulic distributor valve. The mechanism is primarily used to connect the piston-valve assemblies to the spool, allowing hydraulic fluid to flow through the interconnected narrow channels in the spool assemblies. The mechanism is not used to move the spool in the distributor valve.

US patent application US4493474 describes a valve controlled by an electric motor. This two-way valve allows only one channel to be closed or opened. The valve element is coupled to the motor shaft via a yoke mechanism connecting the motor housing to its rotor. As the motor rotates, the shaft located within the electric motor rotor is axially displaced. By moving the shaft connected to the valve element, the channel connecting the two valve paths is closed or opened.

A hydraulic distributor with a screw drive is known from Polish patent application P.422547. The hydraulic distributor consists of a body with a slider located inside. The screw drive is in the form of an electric motor coaxially assembled with a hydraulic distributor, the shaft of which is a nut mounted in the rear cover and the front cover of the electric motor, in which a screw is mounted, which has a self-locking thread and which is coaxially coupled with the slider of the hydraulic distributor.

In the above design there is a problem of clearance between the bolt and the nut.

The purpose of the solution according to the invention is to develop the above structure in a way that allows eliminating the play between the nut constituting the shaft of the electric motor and the screw moving the slide of the hydraulic distributor.

A hydraulic distributor with a screw drive, wherein the hydraulic distributor is made of a body inside which a slider is located, and wherein the screw drive is in the form of an electric motor connected to the hydraulic distributor, the shaft of which is a nut mounted in the rear cover and the front cover of the electric motor, in which a screw is mounted, which has a self-locking thread and which is coaxially coupled with the slider of the hydraulic distributor, according to the invention is characterized in that the nut forming the shaft of the electric motor is a unit consisting of a guide sleeve in which a rear nut mounted in the rear cover and, at a distance therefrom, a front nut mounted in the front cover are mounted, wherein the front nut is permanently coupled to the guide sleeve and the rear nut is rotationally coupled to the guide sleeve and, to compensate for the play in the screw connected to the hydraulic distributor slide, adjustable along its axis. The rotor winding is mounted on a guide sleeve.

Preferably, the guide sleeve and the rear nut are connected by a keyway connection.

Preferably, the rear nut is assembled with a central cover which tightens it to compensate for the play of the screw assembled with the hydraulic distributor slider and which is bolted to the rear cover.

The essence of the developed hydraulic directional control valve with a screw-type spool drive is the use of a split, rotating nut mounted inside the drive motor. The nut cooperates with a screw that moves axially and is permanently connected to the spool of the directional control valve. Rotation of the electric motor causes the nut to rotate, which in turn causes the spool to move. This in turn allows the directional control valve to be overridden. To eliminate play between the screw and the nut, the nut is made of two nuts: a rear movable nut and a front fixed nut. Thus, one is fixed, and the other is sliding and pressed by a cover. The invention's screw mechanism uses a self-locking thread to prevent external force acting on the slider from rotating the nut, and thus causing the slider to move.

The subject of the invention is shown in the drawing, in which Fig. 1 shows the distributor in cross-section.

In an embodiment of the invention, a hydraulic distributor with a screw drive is formed from a hydraulic distributor 1 and a coaxially connected screw drive. The hydraulic distributor 1 is formed from a body 1a, within which a slide 1b is located and flow channels 1c are formed. The hydraulic distributor 1 is closed on the side not connected to the screw drive with a cover 1e screwed to it with screws 1d, in front of which a splined insert 1f is located inside the body 1a. The screw drive is formed by an electric motor 2, the shaft of which is a nut assembly consisting of a guide sleeve 2a in which a rear nut 2c mounted in the rear cover 2b of the electric motor 2 and, at a distance therefrom, a front nut 2e mounted in the front cover 2d of the electric motor 2 are mounted. A screw 2f is screwed into the nut assembly, specifically into its front nut 2e and rear nut 2c, which is then coaxially connected to the slider 1b of the hydraulic distributor 1. The front nut 2e is permanently coupled to the guide sleeve 2a. The rear nut 2c is rotatably coupled to the guide sleeve 2a and, to compensate for the play of the screw 2f connected to the slider 1b of the hydraulic distributor 1, adjustable (slidable) along its axis. The guide sleeve 2a and the rear nut 2c are connected by a keyed connection 2g or a multi-spline connection. The electric motor 2 is bolted to the hydraulic distributor 1 with screws 2h that are supported by its rear cover 2b. The rotor winding 2i is mounted on the guide sleeve 2a. The rear nut 2c is assembled with a central cover 2j, which compresses it to compensate for the play of the screw 2f assembled with the slide 1b of the hydraulic distributor 1, and is a part of the rear cover 2b to which it is screwed with screws 2k. The electric motor 2 of the screw drive is equipped with an electrical connector 21. The ring seal 1g of the slide 1b of the hydraulic distributor 1 is located in the front cover 2d of the electric motor 2. The screw 2f that moves the slider 1b of the hydraulic distributor 1 has a self-locking thread. The rear nut 2c in the rear cover 2b is secured against axial movement by a circlip 2m. The electric motor 2 is a squirrel-cage stepper motor. The front nut 2e and rear nut 2c are mounted in bearings 2n.

The main advantage of the introduced self-locking screw mechanism is that it prevents the movement of the slider 1b of the hydraulic distributor 1 under the influence of external vibrations on the body 1a of the hydraulic distributor 1, in particular in the axis of the slider 1b of the hydraulic distributor 1. This leads to improved stability of the operation of the hydraulic distributor 1, elimination of vibrations of its slider 1b and reduction of efficiency and pressure pulsations in the hydraulic system. Another advantage of the given solution is the accuracy of regulation resulting from the use of a stepper motor, because the high accuracy of the electric motor 2 rotation through the transmission of the screw mechanism results in a very high accuracy of the linear displacement of the slide 1b of the hydraulic directional control valve 1. Thanks to this, the structure according to the invention can also be used as a proportional directional control valve with very high accuracy. An additional benefit of the aforementioned design is energy savings, as the electrical energy to drive electric motor 2 is drawn only when hydraulic distributor 1 is overridden. In a traditional distributor, electrical energy is drawn by an electromagnet throughout the entire operating range of the distributor. In both the traditional and the above-described design, electrical energy is not drawn when the distributor is in neutral.