CN102121491A - Hydraulic cylinder with position sensing device - Google Patents

Abstract

A hydraulic cylinder with a position sensing device relates to a hydraulic cylinder. The invention provides a hydraulic cylinder with a position sensing device which can convert the linear displacement of a piston rod into an angular displacement, and realize accurate measurement of the extension of the piston rod. It includes a piston, a piston rod, a cylinder body and a position sensing device. The cylinder body is composed of a cylinder liner and sealing covers arranged at the front and rear ends of the cylinder liner; its characteristic is that both the front end sealing cover and the rear end sealing cover are provided with a central through hole; The piston rod is provided with a central hole; the position sensing device is provided with a screw rod, a screw sleeve and an angular displacement sensor. Connected, the screw sleeve is sleeved on the screw rod and is threadedly connected with the screw rod; the angular displacement sensor is arranged outside the cylinder body and connected with the rear end of the screw rod.

Description

A hydraulic cylinder with a position sensor

technical field

The invention relates to a hydraulic cylinder, in particular to a hydraulic cylinder with a position sensing device.

Background technique

Existing hydraulic cylinders generally control the extension of the piston rod through a travel switch. This control method is relatively rigid and the accuracy is not high. The extension of the piston rod cannot be changed casually. The travel switch must be repositioned manually. , so that the production efficiency is low. When the travel switch fails, it is very likely to damage the hydraulic cylinder. With the development of electronic components, potentiometer, capacitive, electromagnetic, optical and other sensing and measuring methods are becoming more and more mature. Controlling the extension of the hydraulic cylinder by measuring the real-time position can not only greatly facilitate production and significantly improve Productivity, and more importantly, the improvement of the precision of the actuator has greatly promoted the improvement of product precision. At present, there are some position measuring devices for measuring the extension of the piston rod of the hydraulic cylinder, which are used to control the extension of the piston rod, and they have their own characteristics.

Chinese patent CN201021684 discloses a hydraulic cylinder stroke measuring device configured for use with a hydraulic cylinder. An encoder is provided. A gear is connected to the input end of the encoder, and the gear meshes with a rack. The rack and the measured hydraulic cylinder The piston rods are parallel, and one end of the rack is fixedly connected with the front end of the piston rod protruding from the front end cover of the measured hydraulic cylinder through a connecting piece.

Chinese patent CN101144495 discloses a position measurement system for a hydraulic cylinder, which includes at least one sensor, a magnet and a piston rod, the piston rod has a metal rod core with high magnetic susceptibility and a groove structure along the approximate axial direction, wherein the concave The groove structure is filled with a metal with a magnetic susceptibility lower than that of the rod core, so that the sensor measures the magnetic field of the rod core as it follows the groove structure, from which the relative and absolute position of the piston rod can be determined.

Contents of the invention

The object of the present invention is to provide a hydraulic cylinder with a position sensing device which can convert the linear displacement of the piston rod into angular displacement and realize accurate measurement of the extension of the piston rod.

To achieve the above object, the present invention adopts the following technical solutions:

The invention includes a piston, a piston rod, a cylinder body and a position sensing device. The cylinder body is composed of a cylinder liner and sealing covers arranged at the front and rear ends of the cylinder liner; hole; the piston rod is provided with a central hole; the position sensing device is provided with a screw rod, a screw sleeve and an angular displacement sensor, the screw rod is located in the central hole of the piston rod, the rear end of the screw rod is exposed to the sealing cover at the rear end of the cylinder body, and the rear end of the screw sleeve and the piston rod The end is fixedly connected, the screw sleeve is sleeved on the screw rod and connected with the screw rod; the angular displacement sensor is arranged outside the cylinder body and connected with the rear end of the screw rod.

The piston rod is preferably in sliding fit with the front end sealing cover of the cylinder body.

A radial clearance is preferably provided between the screw rod and the central hole of the piston rod.

It is better to have a thrust step at the rear of the screw. The thrust step is in contact with the rear end sealing cover of the cylinder body. It is better to set a tension cover on the inner wall of the rear end sealing cover. The tension cover is sleeved on the rear of the screw rod and pressed Above the thrust step, this prevents the screw from moving axially.

The rear end of the screw rod is preferably provided with a lock nut.

The angular displacement sensor is preferably an existing optical encoding angular displacement sensor or a magnetic encoding angular displacement sensor.

The cylinder liner, the front end sealing cover, the rear end sealing cover, the piston rod and the screw rod are preferably coaxial centerlines.

Compared with the prior art, the present invention has the following outstanding advantages:

The invention converts the linear displacement of the piston rod into the angular displacement of the screw rod, and obtains the protruding amount of the piston rod by measuring the angular displacement of the screw rod, and can design relevant structural parameters according to the requirement of measurement accuracy. When the piston rod moves axially, the screw sleeve connected with the piston rod must drive the screw to rotate, which converts the linear displacement of the piston rod into the angular displacement of the screw. The signal can be transmitted to the external measuring instrument through the sensor, so as to realize the real-time measurement of the extension of the piston rod.

The calculation method is as follows:

Assuming that the pitch P is 50mm, the number of thread starts n is 2, the lead is 100mm, and the screw diameter _d2 is 40mm, then

为38.50°。当活塞杆往右移动一个导程时，则螺杆转过360°，即活塞杆要轴向移动

螺杆就转过1°。测出螺杆转过的角度，即可得到活塞杆轴向移动数值(即活塞杆伸出量)。若要求活塞杆轴向移动的距离精确到0.01mm，则角度的测量需要精确到0.0277°。若采用磁编码传感器，当磁编码传感器的磁鼓的直径为200mm时，则其周长为628.32mm，0.0277°所对应的弧长为0.048mm，也就是说磁鼓上的磁栅刻度要达到10-2mm数量级的精度。由上可知，可以根据所需要的测量精度设计出螺杆的螺距、升角以及磁鼓直径等参数，这样就可实现所需要的测量精度。由于实时工况中活塞杆伸出量的直线位移测量较难，本发明通过将活塞杆伸出量转换为角位移进行测量，可以大大减小测量装置的尺寸，从而方便测量转置的安装和维护。本发明能实现自动控制，抗干扰能力强，可以实现活塞杆伸出量绝对位置的测量。通过对活塞杆伸出量的测量，就可实现自动控制液压缸的行程。lift angle can be obtained

is 38.50°. When the piston rod moves one lead to the right, the screw rotates 360°, that is, the piston rod moves axially

The screw rod just turns over 1°. Measure the angle of rotation of the screw rod to obtain the value of the axial movement of the piston rod (that is, the amount of extension of the piston rod). If the axial movement distance of the piston rod is required to be accurate to 0.01mm, the angle measurement needs to be accurate to 0.0277°. If a magnetically encoded sensor is used, when the diameter of the magnetic drum of the magnetically encoded sensor is 200mm, its circumference is 628.32mm, and the arc length corresponding to 0.0277° is 0.048mm, which means that the magnetic scale on the magnetic drum must reach Accuracy of the order of 10-2mm. It can be seen from the above that parameters such as the pitch, lift angle, and drum diameter of the screw can be designed according to the required measurement accuracy, so that the required measurement accuracy can be achieved. Since it is difficult to measure the linear displacement of the piston rod extension in real-time working conditions, the present invention can greatly reduce the size of the measuring device by converting the piston rod extension into angular displacement for measurement, thereby facilitating the installation and installation of the measurement transposition maintain. The invention can realize automatic control, has strong anti-interference ability, and can realize the measurement of the absolute position of the protruding amount of the piston rod. By measuring the extension of the piston rod, the stroke of the hydraulic cylinder can be automatically controlled.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

Detailed ways

Referring to Fig. 1, the present invention includes a piston 6, a piston rod 23, a cylinder body 4, a front end sealing cover 9, a rear end sealing cover 1 and a position sensing device. Both the front end sealing cover 9 and the rear end sealing cover 1 are provided with a central through hole, and are locked on the port of the cylinder liner 4 by bolts. The piston rod is provided with a central hole. The piston rod 23 is slidingly fitted with the front end sealing cover 9 . The position sensing device is provided with a screw rod 7, a screw sleeve 5 and an angular displacement sensor (selecting a magnetically encoded angular displacement sensor, including a marker body 17 and a sensor probe 20), 18, and the screw rod 7 is located in the central hole 10 of the piston rod 23, and the screw rod 7 There is a radial clearance to the central bore 10 of the piston rod 23 . The rear end of the screw rod 5 exposes the rear end sealing cover 1, and the rear end of the screw rod 7 is provided with a locking nut 18. The screw sleeve 5 is fastened on the rear end of the piston rod 23 , and the screw sleeve 5 is sleeved on the screw rod 7 and is threadedly connected with the screw rod 7 . The rear part of the screw rod 7 is provided with a thrust step 71, and the thrust step 71 is in contact with the inner wall of the rear end sealing cover 1, and the rear end sealing cover 1 is fastened with a tension cover 13, which is sleeved on the rear part of the screw rod 7 and Press on the thrust step 71, which can prevent the screw rod 7 from moving axially. Cylinder liner 4, front end sealing cover 9, rear end sealing cover 1, piston rod 23, screw rod 7 and tension cover 13 are all coaxial center lines. The angular displacement sensor is located outside the cylinder body and is connected with the rear end of the screw rod 7 . Angular displacement sensor selects existing magnetic coded angular displacement sensor (also can be photoelectric coded angular displacement sensor etc.) The signal output line of the sensor probe 20 is connected to an external measuring instrument, and the measuring instrument adopts an existing measuring instrument. The number 11 is the front end connector of the piston rod 23, the number 19 is the peripheral connector of the rear sealing cover 1, the numbers 3 and 8 are the liquid inlet and outlet respectively, the numbers 12 and 26 are sealing rings, and the number 15 is a labyrinth seal, The function of the labyrinth seal 15 is to allow the pressure head of the hydraulic cylinder to drop before reaching the sealing ring 26, so as to prevent the pressure in the inner cavity of the hydraulic cylinder from being too high so that the sealing ring 26 is pressed tightly on the screw rod 7, thereby preventing the rotation of the screw rod 7 from being greatly affected. The large resistance can effectively prevent the severe wear of the sealing ring 26 and the large deformation of the screw rod 7 due to the torsional force.

Claims (7)

1. A hydraulic cylinder with a position sensing device, comprising a piston, a piston rod, a cylinder body and a position sensing device, the cylinder body is composed of a cylinder liner and sealing covers located at the front and rear ends of the liner; it is characterized in that: the front end seal Both the cover and the rear end sealing cover are provided with a central through hole; the piston rod is provided with a central hole; the position sensing device is provided with a screw, a screw sleeve and an angular displacement sensor, the screw is located in the central hole of the piston rod, and the rear end of the screw is exposed from the cylinder The rear sealing cover is fixedly connected with the screw sleeve with the rear end of the piston rod, and the screw sleeve is sleeved on the screw rod and threadedly connected with the screw rod; the angular displacement sensor is arranged outside the cylinder body and connected with the rear end of the screw rod. 2. A hydraulic cylinder with a position sensing device according to claim 1, characterized in that the piston rod is in sliding fit with the front end sealing cover of the cylinder body. 3. A hydraulic cylinder with a position sensing device according to claim 1, characterized in that there is a radial gap between the screw rod and the central hole of the piston rod. 4. A hydraulic cylinder with a position sensing device as claimed in claim 1, wherein a thrust step is provided at the rear of the screw rod, and the thrust step interferes with the sealing cover at the rear end of the cylinder body, and the inner wall of the sealing cover at the rear end A tightening cover is fixed on the top, and the tightening cover is sleeved on the rear part of the screw rod and pressed against the thrust step. 5. A hydraulic cylinder with a position sensing device as claimed in claim 1, characterized in that a lock nut is provided at the rear end of the screw rod. 6. A hydraulic cylinder with a position sensing device as claimed in claim 1, wherein the angular displacement sensor is an optically encoded angular displacement sensor or a magnetically encoded angular displacement sensor. 7. A hydraulic cylinder with a position sensing device as claimed in claim 1, characterized in that the cylinder liner, the front end seal cover, the rear end seal cover, the piston rod and the screw rod are coaxial centers.