Technical field The present invention relates to a hydraulic motor with radial cylinders provided with rotation speed detection, or rather, a hydraulic motor where several parts of it are designed to carry out precise detection of the rotation speed in order to obtain data to check the management and use of the motor itself and/or the machine or transmission in which the motor is located.

Prior art

The prior art already includes the use of detectors for the rotation speed of hydraulic machines with radial cylinders, motors or pumps, which use proximity sensors associated with the rotation of a component connected to the drive shaft of the hydraulic machine itself. With the rotation of the said component, which is advantageously toothed, an impulse frequency is generated in the sensor which, detected by a special electrical circuit, is directly proportional to the rotation speed of the shaft: by using the analogical or digital signal obtained it is then possible to send the "effective rotation speed" data item to the control unit of the machine or transmission in which the hydraulic machine is located.

It is common in the prior art to use the said associated sensor, but outside the hydraulic machine, so the detection is carried out correctly; the detector, being applied to the outside of the body of the machine, creates encumbrance and adds to the overall dimensions of the hydraulic machine unit, with rotation speed detection device. The detection of the rotation speed of the hydraulic machine in question is also often carried out in the mechanical transmission of movement output by a motor or input by a pump, obliging the manufacturer of the machine or transmission to provide for the insertion of a detection device, especially when the capacity of the hydraulic machine, motor or pump is varied and controlled, in order to check also the rotation speed, over and above the actual capacity achieved by the hydraulic machine, in the ways that are known in the prior art.

However, a similar external solution to the need for detecting and transmitting a signal regarding the rotation speed is governed by the necessity to reduce the encumbrance and bulk of hydraulic machines, in particular ones with radial cylinders, which are often the bulkiest and heaviest.

This prior art is subject to considerable improvement with regard to the possibility of producing a hydraulic motor with radial cylinders provided with detection of rotation speed which eliminates the said drawbacks and, maintaining the current overall dimensions, enables the detection of the speed by means of the internal rotating parts.

Therefore, the technical problem on which the present invention is based is to produce a hydraulic motor with radial cylinders provided with rotation speed detection where the said detection may take place without substantially modifying the composition of the motor and that uses the internal parts to make the detection of the drive shaft rotation speed safe and precise.

Summary of the invention

The present invention solves the above-mentioned technical problem, by using a hydraulic motor with radial cylinders provided with rotation speed detection, comprising: radial cylinders inside which the pistons are positioned in alternate movement by means of a drive shaft; a rotating distributor for sending the hydraulic fluid to the said cylinders, to connect the fluid input and output pipes under pressure alternately by means of the respective input pipe of each cylinder, a rotating connector pin between the drive shaft and the said distributor; characterised by the fact that the said pin is connected to and rotates together with a series of protuberances distributed regularly around the circumference; a proximity sensor is positioned near the said body, so as to come into graze against the said protuberances and provide an electrical/electronic signal to a detection and handling circuit for the signal with regard to the instantaneous rotation speed of the drive shaft.

Furthermore, in a specific embodiment, the series of protuberances is produced on a rotating body connected to the pin and, more advantageously, composed of a wheel and toothed protuberances. Besides, in a further embodiment, the rotating body or toothed wheel is fitted together with negative allowance on assembly to the cylindrical body of the pin.

Yet furthermore, in a specific embodiment, the pin is advantageously provided with axial backing against which the rotating body or toothed wheel is placed.

Furthermore, in a further and preferred embodiment, the axial backing is produced with an axial stop ring housed on the cylindrical body of the pin.

Finally, in a further embodiment, the proximity sensor is housed in a special seat in the lid of the motor housing.

Further characteristics and advantages of the present invention, in the manufacture of a hydraulic motor with radial cylinders provided with rotation speed detection, are included in the following description of an embodiment given as an indicative and non-limiting example with reference to the two drawings enclosed.

Brief description of the drawings

Figure 1 shows a schematic section view of a hydraulic motor with radial cylinders which contains the rotation speed detector in accordance with the invention;

- Figure 2 shows a schematic enlarged section view, which is similar to Figure 1 , of just the parts around the rotation speed detector;

- Figure 3 shows a schematic enlarged section view that is similar to Figure 2 but on a diametral plane and rotated by 90 degrees.

Detailed description of a preferred embodiment The figures show a hydraulic motor 1 provided with radial cylinders 2, in this case oscillating on the spigots 3 and 4, which in turn are respectively supported by the motor housing 5 and the relevant lid 6. A drive shaft 7 with a crank 8 is supported by the said housing and lid with rolling bearings 9 and 10, respectively on the housing and lid. The crank starts the alternate motion of the pistons 1 1 inside the relevant radial cylinders 2. A rotating distributor 12, connected in synchronous rotation to the drive shaft 7, connects the pipes 13, one for each single cylinder, each time with the input 14 and return 15 lights on the body 16 of the distributor, depending on the rotation direction of the drive shaft. The synchronous connection, between the drive shaft and the distributor, is achieved by means of a rotating pin 17 connected with prismatic couplings 18 with the drive shaft 7 and 19 with the distributor 12.

Figure 1 also shows the rotating pin 17 on which a wheel 20 with teeth 21 is fitted with negative allowance onto the cylindrical body 22 of the pin. The correct axial position of the wheel 20, on the rotating pin 17, is determined with an axial end-stroke 23, which is made of an axial stop ring for shafts in the embodiment shown.

The wheel 20 with teeth 21 is housed in a circular seat 24, which radially gives onto a proximity sensor 25 to detect the passage of the teeth during the rotation of the pin 17. The rotation of the drive shaft 7, the pin 17 and subsequently the distributor 12 takes place in synchrony for the correct functioning of the motor. As a result of the fitting on the pin 17, the rotation of the wheel 20 with teeth 21 , by means of the sensor 25, produces an analogical or digital signal, depending on the type of sensor and reading circuit, which is directly proportional to the rotation speed of the drive shaft. The sensor 25 is placed into the required position through a hole 26, radial to the said circular seat 24, and fixed using a hermetic flange 27 to avoid leakage, even if there is no fluid under pressure in the said circular seat 24..

To complete the proposed solution, in the case of a hydraulic motor with radial cylinders, in accordance with the invention, provided with rotation speed detection, the detection takes place in a precise way at all rotation speeds, whether these speeds are at a very low or extremely high rpm. The detection using a wheel 20 with teeth 21 enables a greater number of impulses per revolution of the drive shaft, at least as high as the number of teeth on the wheel, with respect to the prior art where proximity sensors were used to detect the position of one or more oscillating cylinder(s) and, therefore, with limits to correct detection, especially at low rpm speeds.