TWI771572B - Fluid pressure cylinder with detection mechanism - Google Patents

Abstract

A fluid pressure cylinder with detection mechanism, having a piston (40) slidably arranged inside a cylinder hole (14) of a cylinder body (12). A screw hole (46) formed at the center of the piston is screw-engaged with a threaded shaft (60) for position detection. The piston is supported by the cylinder body so as to be limited in rotation about the shaft center, whereas the threaded shaft for position detection is supported by an end cover (20) provided at an end of the cylinder body so as to be rotatable around the shaft center and limited in displacement along the shaft center. A sensor (84) is arranged to face an end of the threaded shaft for position detection extending outward from the end cover.

Description

Fluid pressure cylinder with detection mechanism

The present invention relates to a fluid pressure cylinder provided with a detection mechanism for detecting the position of a piston.

Conventionally, in order to detect the position of the piston moving in the cylinder hole, it is known to install a magnet on the piston, and to install a magnetic sensor for detecting the magnetic flux of the magnet on the side surface of the fluid pressure cylinder. The magnetic sensor detects that the piston is at a predetermined position by utilizing the change in the magnetic flux at the position where the magnetic sensor is installed along with the movement of the piston.

In the above-mentioned fluid pressure cylinder, the installation position of the magnetic sensor must be adjusted so that the magnetic sensor can respond when the piston is at a predetermined position. Therefore, a mounting groove extending in the axial direction is provided on the side surface of the fluid pressure cylinder, and the magnetic sensor can be mounted at any position in the longitudinal direction of the mounting groove (see, for example, Japanese Patent Application Laid-Open No. 2009-30674).

However, when detecting the magnetic flux of the magnet installed in the piston, there is a limitation that a magnetic sensor must be installed in the vicinity of the space through which the piston passes. In addition, it is not easy to adjust the installation position of the magnetic sensor. Furthermore, in order to detect a plurality of positions of the piston, a corresponding number of magnetic sensors must be provided.

The present disclosure has been developed to solve the above-mentioned problems, and its object is to provide a fluid pressure cylinder with a detection mechanism, which can be equipped with a sensor at the part separated from the piston, and the installation position of the sensor does not need to be adjusted, and can The position of the piston is precisely detected.

In the fluid pressure cylinder with detection mechanism of the present invention, the piston is arranged so that the piston can slide freely in the cylinder hole of the cylinder body. Supported so that the rotation around the axis is restricted, the position detection threaded shaft system can rotate around the axis, and is supported by the end cover provided at the end of the cylinder so that the displacement in the direction of the axis is restricted, and, with Sensors are disposed on the ends of the threaded shaft for position detection that extends outward from the end cover so as to face each other.

According to the above-mentioned fluid pressure cylinder with detection mechanism, since the linear motion of the piston is converted into the rotational motion of the threaded shaft for position detection, and the sensor is disposed on the end side of the threaded shaft for position detection, it is possible to detect the movement of the piston. The position sensor is arranged at a part separated from the piston. Moreover, there is no need to adjust the installation position of the sensor specially, and the position of the piston can be detected finely.

In the above-mentioned fluid pressure cylinder with detection mechanism, preferably, the piston rod connected with the piston has a hollow structure, and the threaded shaft for position detection enters the interior of the piston rod. Thereby, the space required for arrangement|positioning of the screw shaft for position detection can be reduced.

In addition, it is preferable that the cross-sectional shape of the piston and the cylinder hole is polygonal to restrict the rotation of the piston. Thereby, the rotation of the piston can be surely restricted.

Moreover, it is preferable that the threaded shaft system for position detection is rotatably supported by a bearing provided in the end cover, and the bearing is clamped at the step portion formed on the threaded shaft for position detection and mounted on the threaded shaft for position detection. Between the nuts, the displacement in the axial direction of the threaded shaft for position detection is limited. Thereby, the structure for restricting the axial displacement of the screw shaft for position detection can be simplified.

Furthermore, a magnet is preferably installed at the end of the threaded shaft for position detection, and a magnetic sensor is provided opposite to the magnet. In this case, a cover member covering the magnetic sensor and the magnet is preferably provided. Thereby, the position of the piston can be accurately detected without being affected by an external magnetic field.

Moreover, it is preferable that a ball is interposed between the threaded hole and the threaded shaft for position detection. Thereby, it becomes easy to detect the position of the piston finely.

Furthermore, the sensor can also be an optical sensor.

In the fluid pressure cylinder with the detection mechanism of the present invention, a sensor for detecting the position of the piston can be arranged at a part separated from the piston. Moreover, there is no need to adjust the installation position of the sensor specially, and the position of the piston can be detected finely.

The above-mentioned objects, features, and advantages will become more apparent from the description of the preferred embodiments described later with reference to the accompanying drawings.

10‧‧‧Fluid pressure cylinder

12‧‧‧Cylinder block

14‧‧‧Cylinder bore

16‧‧‧First port

18‧‧‧Second port

20‧‧‧End shield

22‧‧‧Flange

24‧‧‧Through hole

24a‧‧‧First Diameter

24b‧‧‧Second diameter

24c‧‧‧The third diameter

24d‧‧‧4th diameter

26‧‧‧Rod Cover

28‧‧‧Lock ring

30‧‧‧Through hole

32‧‧‧Rod liners

34‧‧‧First sealing ring

36‧‧‧Recess

38‧‧‧First damper

40‧‧‧Piston

42‧‧‧Main body

44‧‧‧Connections

46‧‧‧Threaded hole

48‧‧‧Piston seals

50‧‧‧Recess

52‧‧‧Second damper

54‧‧‧Piston rod

56‧‧‧Socket

58‧‧‧Second sealing ring

60‧‧‧Threaded shaft for position detection

62‧‧‧Threaded part

64‧‧‧Support

64a‧‧‧Large diameter

64b‧‧‧Middle diameter part

64c‧‧‧Small diameter

66‧‧‧Third sealing ring

68‧‧‧Bearing

70‧‧‧Bearing Press

72‧‧‧Locking Nuts

74‧‧‧Magnet

76‧‧‧Magnet holder

78‧‧‧Substrate

80‧‧‧Base member

82‧‧‧cylindrical protrusion

84‧‧‧Magnetic sensor

86‧‧‧Cover components

88‧‧‧First pressure chamber

90‧‧‧Second pressure chamber

Fig. 1 is a plan view of a fluid pressure cylinder with a detection mechanism according to an embodiment of the present invention.

FIG. 2 is a front view of the fluid pressure cylinder of FIG. 1. FIG.

FIG. 3 is a cross-sectional view taken along line III-III of the fluid pressure cylinder of FIG. 1 .

Fig. 4 is a cross-sectional view taken along the line IV-IV of the fluid pressure cylinder of Fig. 2 .

FIG. 5 is a side view of the fluid pressure cylinder of FIG. 1. FIG.

Fig. 6 is a cross-sectional view corresponding to Fig. 3 when the fluid pressure cylinder of Fig. 1 is in another operating state.

Hereinafter, the preferred embodiments of the fluid pressure cylinder with the detection mechanism of the present invention will be listed and described with reference to the drawings.

The fluid pressure cylinder 10 includes a cylinder block 12 , an end cover 20 , a rod cover 26 , a piston 40 , a piston rod 54 , a position detection threaded shaft 60 , a magnet 74 , and a magnetic sensor 84 . The fluid pressure cylinder 10 is attached to, for example, a workpiece clamping device not shown.

As shown in FIG. 4, the cylinder block 12 has a rectangular shape in cross section perpendicular to its axis, and has four sides. In the cylinder block 12, a cylinder hole 14 is penetrated in the axial direction thereof. The cross-sectional shape of the sliding area of the piston 40 of the cylinder bore 14 is a regular octagon. As shown in FIG. 1 , one side surface of the cylinder block 12 is provided with a first orifice 16 and a second orifice 18 for air supply and exhaust which communicate with the cylinder hole 14 .

The end cap 20 is formed into a cylindrical shape from an aluminum alloy. The end cover 20 has a flange portion 22 extending radially outward. After the flange portion 22 is fitted to one end side of the cylinder hole 14, a part of the cylinder block 12 is riveted to the flange portion 22, whereby the end cover is attached. 20 is fixed to the cylinder block 12 . The center of the end cover 20 is provided with a through hole 24 through which a position detection threaded shaft 60 is inserted. The diameter of the through hole 24 is gradually enlarged from the end on the side facing the piston 40 to the end on the side facing the magnetic sensor 84 , and these are referred to as the first diameter portion 24 a and the second diameter portion in this order. Diameter portion 24b, third diameter portion 24c, and fourth diameter portion 24d.

The rod cover 26 is fitted into the cylinder hole 14 from the other end side of the cylinder hole 14 , and is fixed to the cylinder block 12 by a locking ring 28 . The center of the rod cover 26 is provided with a through hole 30 through which the piston rod 54 is inserted. The inner circumference of the rod cover 26 is provided with rod spacers 32 through the grooves. The rod packing 32 is slidably connected to the outer peripheral surface of the piston rod 54 and seals the space between the piston rod 54 and the rod cover 26 . The outer periphery of the rod cover 26 is provided with a first sealing ring 34 through the groove. The first sealing ring 34 is in contact with the wall surface of the cylinder hole 14 and seals the space between the cylinder block 12 and the rod cover 26 .

The surface of the rod cover 26 facing the piston 40 is provided with an annular concave portion 36 , and an annular first damper 38 is installed in the concave portion 36 . The first damper 38 abuts against the rod cover 26 at the end position when the piston 40 moves toward the rod cover 26 side, and has a function of reducing the shock of the piston 40 .

The piston 40 includes: a main body part 42; and a cylindrical connecting part 44 provided to protrude from the main body part 42 toward the rod cover 26 side. The screw hole 46 for the screw shaft 60 for screwing position detection is provided in the center of the piston 40 so as to penetrate in the axial direction.

As shown in FIG. 4 , the body portion 42 of the piston 40 has a regular octagonal cross-section integrated with the cross-section of the cylinder hole 14 , and is fitted into the cylinder hole 14 . Thereby, the piston 40 can move in the cylinder hole 14 in the axial center direction in a state where the rotation around the axial center is restricted. In the present embodiment, the cross-sectional shape of the cylinder hole 14 and the cross-sectional shape of the piston 40 fitted into the cylinder hole 14 are regular octagons, but they may be polygonal shapes which are integrated with each other.

The outer periphery of the body portion 42 of the piston 40 is fitted with a piston seal 48 through the groove. The piston seal 48 is slidably connected to the wall surface of the cylinder bore 14 and divides the space inside the cylinder 12 into a first pressure chamber 88 on the end cover 20 side and a second pressure chamber 90 on the rod cover 26 side.

The surface of the body portion 42 of the piston 40 facing the end cover 20 is provided with an annular recess 50 , and an annular second damper 52 is installed in the recess 50 . The second damper 52 is in contact with the end cover 20 at the end position when the piston 40 moves toward the end cover 20 , and has a function of reducing the shock of the piston 40 .

The piston rod 54 is formed into a thin cylindrical shape, and one end of the piston rod 54 covers the connecting portion 44 of the piston 40 and is fixed in a state without a gap with the main body portion 42 . The other end of the piston rod 54 extends to the outside through the through hole 30 of the rod cover 26 , and a socket 56 is fixed at the end of the piston rod 54 by screwing. A part of the socket 56 is embedded in the piston rod 54 including the threaded portion, and a second sealing ring 58 is installed on the outer periphery of the socket 56 through the groove. The second sealing ring 58 is in contact with the inner peripheral surface of the piston rod 54 and seals the space between the piston rod 54 and the socket 56 .

The threaded shaft 60 for position detection includes a threaded portion 62 screwed into the threaded hole 46 of the piston 40 , and a support portion 64 supported by the end cap 20 . A portion of the threaded portion 62 enters the interior of the piston rod 54 . As will be described later, the displacement in the axial direction of the position detection screw shaft 60 is restricted.

The female thread formed in the threaded hole 46 of the piston 40 and the male thread formed in the threaded portion 62 of the threaded shaft 60 for position detection are designed to convert the linear motion (displacement in the axial direction) of the piston 40 into the thread for position detection. Rotational movement of the shaft 60 . That is, the lead angle between the female thread and the male thread for these motion transformations is set to be larger than the friction angle, so that the thrust load acting on the piston 40 does not cause self-locking.

The support portion 64 of the threaded shaft 60 for position detection is composed of a large-diameter portion 64a connected to the threaded portion 62, a middle-diameter portion 64b connected to the large-diameter portion 64a, and a position-detecting threaded shaft connected to the middle-diameter portion 64b. The small diameter portion 64c at the end of the 60 is constituted. The first diameter portion 24a of the through hole 24 of the end cap 20 is provided with a third sealing ring 66 through the groove. The third seal ring 66 is in contact with the large-diameter portion 64 a of the support portion 64 , and seals the space between the end cap 20 and the position detection threaded shaft 60 .

The first pressure chamber 88 communicates with the inner space of the piston rod 54 , and is kept airtight to the outside by the second seal ring 58 and the third seal ring 66 . The second pressure chamber 90 is kept airtight to the outside by the rod packing 32 and the first seal ring 34 .

A bearing 68 that rotatably supports the threaded shaft 60 for position detection is disposed in the through hole 24 of the end cover 20 . After the bearing 68 is fitted into the second diameter portion 24b of the through hole 24, it is axially positioned by the bearing presser 70 fixed to the third diameter portion 24c by press fitting.

The inner diameter portion 64b of the threaded shaft 60 for position detection is provided with a male thread, and the male thread is screwed with a locking nut 72 . One axial end of the bearing 68 is in contact with the locking nut 72, and the other axial end of the bearing 68 is in contact with the step surface (step difference) between the large diameter portion 64a and the middle diameter portion 64b of the threaded shaft 60 for position detection. department). Thereby, the displacement in the axial center direction of the screw shaft 60 for position detection is restricted.

A magnet holder 76 for supporting the magnet 74 is attached to the small diameter portion 64c of the threaded shaft 60 for position detection. The magnet holder 76 is made of an aluminum alloy such as duralumin. The magnet 74 is made of neodymium and has a disk shape, and when it is divided into two parts by a plane including the axis, one part and the other part are magnetically N pole and S pole, respectively.

The end cap 20 is attached to the base member 80 supporting the substrate 78 by means of press fitting or the like. The base member 80 is formed of a resin material such as PBT and has a cylindrical shape, and has a cylindrical protruding portion 82 that fits into the fourth diameter portion 24 d of the through hole 24 of the end cap 20 . The base plate 78 is fixed to the end face of the base member 80 on the opposite side to the end cap 20 .

The substrate 78 is mounted with a magnetic sensor 84 that detects the magnetic flux of the magnet 74 . The magnet 74 and the magnetic sensor 84 are arranged inside the base member 80 so as to face each other on the central axis of the position detection screw shaft 60 . The magnetic sensor 84 is configured to include at least one pair of Hall elements (not shown), and detect the magnetic flux of the magnet 74 that rotates with the position detection threaded shaft 60 to detect the position detection threaded shaft 60 . Rotation position. The detection of the rotational position of the magnet by a pair of Hall elements disposed opposite to the disk-shaped magnet is a conventional technique, so detailed descriptions are omitted.

The base member 80 is attached with a cover member 86 covering the base plate 78 . The cover member 86 is made of a steel material such as a ferromagnetic cold-rolled coil (SPCC), and has a function of shielding the magnetism of the magnet 74 . Thereby, malfunction of the magnetic sensor 84 caused by the external magnetic field is prevented.

The fluid pressure cylinder 10 with the detection mechanism of the present embodiment is basically constructed as described above, and its function will be described below. Further, as shown in FIG. 3 , the state where the second damper 52 of the piston 40 is in contact with the end cover 20 and the piston 40 is located at the stroke end of the end cover 20 side is set as the initial position.

In the above initial position, the switching valve (not shown) operates to supply air from the first orifice 16 to the first pressure chamber 88 , and the air in the second pressure chamber 90 is discharged from the second orifice 18 . Thereby, the piston 40 receives the thrust in the direction of the rod cover 26 . Since the rotation of the piston 40 about the axis is restricted, the screw shaft 60 for position detection advances toward the rod cover 26 while rotating, and the piston rod 54 integrated with the piston 40 also advances and protrudes from the rod cover 26.

Displacement in the axial center direction of the position detection screw shaft 60 is restricted, and the piston 40 is further rotated in a predetermined direction as the piston 40 moves forward. The magnet 74 fixed to the end side of the position detection screw shaft 60 rotates on the spot together with the position detection screw shaft 60 so that the position where the magnetic flux exists on the Hall element is changed at one of the opposing positions of the magnet 74 . The rotational position of the screw shaft 60 for position detection is detected based on the change of this magnetic flux. That is, the advance position of the piston 40 is detected immediately. In addition, as the piston 40 advances, the length of the position detection threaded shaft 60 that enters the inside of the piston rod 54 decreases.

Finally, the piston 40 comes into contact with the first damper 38 provided in the rod cover 26 and reaches the stroke end (see FIG. 6 ). Of course, the magnetic sensor 84 can detect the stroke end of the piston 40 reaching the rod cover 26 side.

After the work such as clamping the workpiece is performed by the extension of the piston rod 54, the switching valve (not shown) is actuated to supply air from the second port 18 to the second pressure chamber 90, and the air in the first pressure chamber 88 Discharge from the first orifice 16 . Thereby, the piston 40 receives the thrust in the direction toward the end shield 20 . Since the rotation of the piston 40 around the axis is restricted, the piston rod 54 integrated with the piston 40 is retracted in the direction away from the rod cover 26 while rotating the position detection screw shaft 60 in the opposite direction to the above. into the cylinder 12.

As the piston 40 retreats, the position detection screw shaft 60 rotates in the opposite direction to the forward movement of the piston 40 , and the magnet 74 fixed to the end of the position detection screw shaft 60 also faces the position detection screw shaft 60 . rotate in the same direction. Then, the magnetic flux system changes in the position where the pair of Hall elements is present opposite to the magnet 74, and the rotational position of the screw shaft 60 for position detection is detected accordingly. That is, the retracted position of the piston 40 is detected immediately. In addition, as the piston 40 retreats, the length of the position detection threaded shaft 60 that enters the inside of the piston rod 54 increases.

Finally, the second damper 52 provided on the piston 40 abuts against the end cap 20 and reaches the end of the stroke, returning to the initial position. Of course, the magnetic sensor 84 can also be used to detect that the piston 40 reaches the end of the stroke of the end cap 20 .

According to the present embodiment, the linear motion of the piston 40 is converted into the rotational motion of the position detection screw shaft 60, and the magnetic sensor 84 is disposed on the end of the position detection screw shaft 60, so that the piston 40 can be detected by the magnetic sensor 84. The magnetic sensor 84 of this position is arranged at a part separated from the piston 40 . Furthermore, the position of the piston 40 can be detected finely. Furthermore, since the screw shaft 60 for position detection is arrange|positioned so that it can enter into the inside of the piston rod 54, the whole structure can be reduced in size.

In this embodiment, balls are not interposed between the female thread formed in the threaded hole 46 of the piston 40 and the male thread formed in the threaded portion 62 of the threaded shaft 60 for position detection, but a ball interposed therebetween may be used. Threaded shaft. When using a ball screw shaft, the lead angle of the thread can be reduced because it is not easy to cause self-locking. Thereby, the ratio of the rotation amount of the threaded shaft 60 for position detection with respect to the movement amount of the piston 40 can be increased, and the position of the piston 40 can be easily and precisely detected.

In this embodiment, the magnet 74 and the magnetic sensor 84 are used as means for detecting the rotational position of the position detection screw shaft 60, but an optical sensor may be used instead. For example, a light-shielding plate having a slit may be provided at the end of the position detection screw shaft 60, and a light-emitting portion and a light-receiving portion may be provided to sandwich the light-shielding plate therebetween.

The fluid pressure cylinder with the detection mechanism of the present invention is not limited to the above-described embodiment, and of course various forms can be adopted within the scope of not departing from the gist of the present invention.

10‧‧‧Fluid pressure cylinder

12‧‧‧Cylinder block

14‧‧‧Cylinder bore

16‧‧‧First port

18‧‧‧Second port

20‧‧‧End shield

22‧‧‧Flange

24‧‧‧Through hole

24a‧‧‧First Diameter

24b‧‧‧Second diameter

24c‧‧‧The third diameter

24d‧‧‧4th diameter

26‧‧‧Rod Cover

28‧‧‧Lock ring

30‧‧‧Through hole

32‧‧‧Rod liners

34‧‧‧First sealing ring

36‧‧‧Recess

38‧‧‧First damper

40‧‧‧Piston

42‧‧‧Main body

44‧‧‧Connections

46‧‧‧Threaded hole

48‧‧‧Piston seals

50‧‧‧Recess

52‧‧‧Second damper

54‧‧‧Piston rod

56‧‧‧Socket

58‧‧‧Second sealing ring

60‧‧‧Threaded shaft for position detection

62‧‧‧Threaded part

64‧‧‧Support

64a‧‧‧Large diameter

64b‧‧‧Middle diameter part

64c‧‧‧Small diameter

66‧‧‧Third sealing ring

68‧‧‧Bearing

70‧‧‧Bearing Press

72‧‧‧Locking Nuts

74‧‧‧Magnet

76‧‧‧Magnet holder

78‧‧‧Substrate

80‧‧‧Base member

82‧‧‧cylindrical protrusion

84‧‧‧Magnetic sensor

86‧‧‧Cover components

88‧‧‧First pressure chamber

90‧‧‧Second pressure chamber

Claims (6)

A fluid pressure cylinder with a detection mechanism is provided with a piston configured to slide freely in a cylinder hole of a cylinder body, a threaded hole provided in the center of the piston is screwed with a threaded shaft for position detection, and the piston is made of the The cylinder is supported so that its rotation around the axis is restricted, the position detection threaded shaft can rotate around the axis, and is supported by an end cover provided at the end of the cylinder so that the displacement in the direction of the axis is restricted. , and a sensor is arranged opposite to the end of the threaded shaft for position detection that extends outward from the end cover, and the threaded shaft system for position detection has a thread that is screwed into the threaded hole of the piston. part; and a support part supported on the end cap, the support part of the threaded shaft for position detection is composed of a large diameter part connected to the threaded part, a middle diameter part connected to the large diameter part, and a middle diameter part connected to the middle diameter part. The diameter portion is connected to a small diameter portion constituting the end portion of the position detection threaded shaft, and the position detection threaded shaft is rotatably supported by a bearing provided in the end cover, and the bearing is clamped in the A step portion is formed between the large-diameter portion and the middle-diameter portion and a nut installed on the middle-diameter portion, so as to limit the displacement in the axial direction of the threaded shaft for position detection, and the piston and the The cross-sectional shape of the cylinder hole is polygonal, thereby restricting the rotation of the aforementioned piston. The fluid pressure cylinder with detection mechanism according to claim 1, wherein the piston rod connected to the piston has a hollow structure, and the position detection threaded shaft enters the interior of the piston rod. The fluid pressure cylinder with detection mechanism according to claim 1, wherein a magnet is attached to the end of the threaded shaft for position detection, and a magnetic sensor is provided facing the magnet. The fluid pressure cylinder with detection mechanism as described in claim 3 of the claimed scope is provided with a cover member covering the magnetic sensor and the magnet. The fluid pressure cylinder with a detection mechanism according to claim 1, wherein a ball is interposed between the threaded hole and the threaded shaft for position detection. The fluid pressure cylinder with detection mechanism according to claim 1, wherein the sensor is an optical sensor.

Images