JPH11336714A - Stroke position detector for fluid pressure cylinder and lift cylinder for fork lift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce man-hour required to mount a detector inside a fluid pressure cylinder without mounting the detector outside the fluid pressure cylinder. SOLUTION: A wire winding part 19 is mounted on a detecting chamber 18 in a cylinder tube 12, and a supporting shaft 22 rotatably-supported on a spool supporting part 20 is energized so as to rotate in such a direction that wire 26 is wound by a spiral spring 23. The wire 26 is wound around a spool 21 fixed to the supporting shaft 22 so that it may be incapable of relative rotation, and the end of the wire 26 is connected to a piston 14. A flange 25b of the spool 21 is provided with a plurality of parts 27 to be detected on the identical circumference, and a magnetic sensor 28 capable of detecting the respective parts to be detected is mounted on the cylinder tube 12. A magnetic sensor 29 detecting the piston 14 disposed at the initial position is mounted on the cylinder tube 12. A stroke detecting unit 30 determines the stroke position of the piston 14 based on the number of the parts 27 to be detected for the amount of stroke of the piston 14 in the initial position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stroke position detecting device for a hydraulic cylinder having a function of detecting a stroke position of a piston or the like, and a lift cylinder for a forklift provided with the stroke position detecting device. .

[0002]

2. Description of the Related Art Conventionally, forklifts detect the lift of a fork moved up and down by a lift cylinder in order to automatically control the lift of the fork and to detect the vertical position of the center of gravity. The lift of the fork is detected by a wire winding type lift detector as shown in FIG. This wire winding type lifting height detecting device includes a wire winding device 81 at a lower portion of the outer surface of the outer mast 80. This wire winder 8
Reference numeral 1 denotes a wire 82 wound around a reel 83 by a built-in spiral spring mechanism (not shown). The tip of the wire 82 is connected to a lift bracket 84. or,
The wire winder 81 includes a potentiometer (not shown) having the rotation axis of the winder 81 as an input shaft. Then, when the fork 86 rises with the extension of the lift cylinder 85, the wire 82 is fed out from the wire winder 81, and the potentiometer rotates by a rotation amount corresponding to the lifting height of the fork 86. Therefore, the lift of the fork 86, that is, the stroke position of the lift cylinder 85 is detected by the potentiometer.

However, in this lift detecting device, a detecting portion for detecting a stroke position and outputting a detected value, that is, a wire 82, a wire winder 81, a potentiometer, and the like are provided outside the lift cylinder 85. There is a possibility that the function of the detection unit may be impaired due to collision with an object, and there is a possibility that high reliability cannot be ensured.

Therefore, in order to solve such a problem,
It is conceivable that the lift is detected by a stroke position detection device having a configuration in which the detection unit is provided inside the lift cylinder 85. For example, as shown in FIG. 9, a plurality of non-magnetic portions 88 are provided at equal intervals in the length direction on the outer peripheral surface of a piston rod 87 which is a magnetic material. Also, the cylinder tube 89
Is provided with a magnetic sensor 90 capable of detecting a magnetic portion between adjacent non-magnetic portions 88. And the piston rod 87
The relative stroke position of the piston rod 87 is sequentially detected based on the presence or absence of the non-magnetic portion 88 facing the magnetic sensor 90 with the expansion and contraction of the magnetic sensor 90. Therefore, since the lift detecting device is provided inside the cylinder tube 89, there is no possibility of collision with an object, and high reliability can be secured.

[0005]

However, in order to provide a large number of non-magnetic portions 88 on the piston rod 87, a plurality of holes are formed in the outer peripheral surface of the piston rod 87 by cutting along the length direction. A non-magnetic material processed into the shape of the hole must be embedded in the hole. For example,
In order to detect the stroke position of the lift cylinder 85 in units of 1 cm, it is necessary to provide the piston rod 87 with nonmagnetic portions 88 at 1 cm intervals. Therefore, there is a problem that the number of processing steps and the number of assembling steps for providing the nonmagnetic portion 88 are significantly increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a detection unit for outputting a detection value of a state quantity corresponding to a stroke position outside a fluid pressure cylinder. And a stroke position detecting device for a hydraulic cylinder capable of reducing the number of processing steps for providing a detection unit inside as compared with a conventional hydraulic cylinder. The object of the present invention is to provide a lift cylinder for a forklift equipped with a lift cylinder.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a cylinder tube and a part thereof are housed in the cylinder tube so as to be movable within a predetermined stroke range, and a part of the cylinder tube is provided. A moving body extending from the cylinder tube to the outside and being relatively moved with respect to the cylinder tube by supply / discharge of fluid to / from the cylinder tube, wherein the moving body interferes with the moving body in the cylinder tube. A winding transmission member rotatably provided at a position not to be rotated and having a leading end connected to the moving body is wound so as to be able to be fed or wound up with the movement of the moving body in the cylinder tube. A winding part, provided at a position in the cylinder tube that does not interfere with the moving body, and the winding is performed in accordance with the movement of the moving body in a direction away from the winding part. While allowing the winding transmission member wound around the winding unit to be unwound, and the winding being unwound from the winding unit along with the movement of the moving body in a direction approaching the winding unit. Biasing means for biasing the winding part to rotate so that the transmission member is wound around the winding part; and a stroke position of the moving body or a change amount of the stroke position within the stroke range. State quantity detecting means for detecting a state quantity based on a corresponding rotation state of the winding portion.

According to a second aspect of the present invention, in the first aspect of the present invention, the state amount is a rotation amount of the winding portion accompanying the movement of the moving body, and the state amount detecting means is And rotation amount detection means provided in the cylinder tube to detect the rotation amount of the winding portion.

According to a third aspect of the present invention, in the second aspect of the invention, the rotation amount detecting means is provided so as to be integrally rotatable with the winding portion, and has the same circle about a rotation axis. A rotating part having a plurality of detected parts provided at equal angular intervals on the circumference, and a detecting part is provided so as to be able to be relatively to each of the detected parts, and with the rotation of the winding part, And a sensor for sequentially detecting the presence or absence of each of the detected parts.

According to a fourth aspect of the present invention, in the second or third aspect, the winding portion is formed so as to wind the winding transmission member in an overlapping state, and A reference state detecting means for detecting that the body is located at a reference position set at a predetermined stroke position within the stroke range, and a movement of the moving body from the reference position by the reference state detecting means. And a stroke position calculating means for obtaining a stroke position of the moving body based on the rotation amount detected by the rotation amount detecting means.

According to a fifth aspect of the present invention, in the first aspect of the invention, the winding portion is formed so as to be wound in a state where the winding transmission member is overlapped, and the state amount is set to The amount of rotation of the winding part associated with the movement of the moving body, and the diameter of the winding of the winding transmission member wound around the winding part, wherein the state quantity detecting means is provided in the cylinder tube. And a winding diameter detecting means provided in the cylinder tube and detecting a winding diameter of the winding part.

According to a sixth aspect of the present invention, in the invention according to the fifth aspect, the rotation amount detected by the rotation amount detecting means and the winding amount detected by the winding diameter detecting means are provided. A stroke position calculating means for obtaining a stroke position of the moving body from a diameter;

According to a seventh aspect of the present invention, in the first aspect of the present invention, the speed reducing mechanism for reducing the amount of rotation of the winding portion with respect to the entire moving range of the moving body to a predetermined amount of rotation of less than one rotation. And a plate cam having a cam surface which is rotated by an output shaft of the speed reduction mechanism and a distance from a rotation center gradually changes from a minimum to a maximum within a range of the predetermined rotation amount,
The state quantity is a distance from a predetermined position separated from the cam surface to the cam surface in a radial direction of the rotation axis of the plate cam. Supported in the cylinder tube so that
And a distance detecting means for detecting the distance from the detecting section to the cam surface.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the plate cam is formed of a good conductor, and the distance detecting means corresponds to a distance to the cam surface in a non-contact state. An eddy current displacement sensor that outputs an output voltage is provided.

According to a ninth aspect of the present invention, in accordance with the seventh or eighth aspect of the invention, there is provided a stroke position calculating means for obtaining a stroke position of the moving body from the distance detected by the distance detecting means. Equipped.

According to a tenth aspect of the present invention, a lift cylinder for a forklift has the function of any one of the first to ninth aspects. (Operation) According to the first aspect of the present invention, the stroke position of the moving body or the amount of change in the stroke position is fed out from the winding portion provided in the cylinder tube and connected to the moving body. It is converted into a state quantity based on the rotation state of the winding part via the winding transmission member. This state quantity is detected by state quantity detection means provided in the cylinder tube.

According to the invention described in claim 2, according to claim 1
In addition to the effect of the invention described in (1), the amount of rotation of the winding portion according to the change in the stroke position of the moving body is detected as the rotation state.

According to the invention described in claim 3, according to claim 2,
In addition to the effect of the invention described in the above, the amount of rotation of the winding portion is detected by the number of detected portions provided in the rotating portion.

According to the invention described in claim 4, according to claim 2,
Alternatively, in addition to the effect of the invention described in claim 3, when the winding diameter of the winding transmission member wound around the winding portion changes with the movement of the moving body, the stroke of the moving body depends on the stroke position. The amount of rotation of the winding unit per unit moving amount of the moving body changes. Then, the stroke position is obtained from the amount of rotation of the winding part from the state where the moving body is at the reference position. Note that the calculation refers to the case where the stroke position is obtained using a predetermined map in which the stroke position is associated with the relative movement amount from the reference position, and the case where the stroke position is calculated from the relative movement amount from the reference position using a predetermined calculation formula And calculating the stroke position.

According to the invention described in claim 5, according to claim 1,
In addition to the operation of the invention described in the above, when the winding diameter of the winding transmission member wound around the winding portion with the movement of the moving body changes, the unit of the moving body according to the stroke position of the moving body The amount of rotation of the winding part per movement amount changes. Then, the winding diameter and the amount of rotation from which the length of the winding transmission member corresponding to the change in the stroke position of the moving body can be determined are detected.

According to the invention of claim 6, according to claim 5,
In addition to the operation of the invention described in (1), the length of the winding transmission member corresponding to the stroke position of the moving body is calculated from the winding diameter and the amount of rotation, and the stroke position is obtained from this length.

According to the invention of claim 7, according to claim 1,
In addition to the effect of the invention described in (1), the stroke position of the moving body is converted into a distance from the detection unit to the cam surface, and this distance is detected by the distance detection means.

According to the invention described in claim 8, according to claim 7,
In addition to the effect of the invention described in the above, the distance from the detection section to the cam surface is detected in a non-contact manner. According to the ninth aspect, in addition to the operation of the seventh or eighth aspect, the stroke position is obtained from the detected distance.

According to the tenth aspect, the lift cylinder provided in the forklift is the first to ninth aspects.
The function of the invention described in any one of the above is provided.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view showing a part of a lift cylinder 10 as a fluid pressure cylinder of a forklift (not shown). The lift cylinder 10 is a cylinder tube 1 to which hydraulic oil is supplied / discharged from outside via a supply / discharge port 11.
2 is provided. A piston 14 that defines an oil chamber 13 into which hydraulic oil is supplied and discharged is movably accommodated in the cylinder tube 12 within a predetermined stroke range.
4, the tip side is the cylinder tube 12
A piston rod 15 extending outward from the upper end of the piston rod is provided. In the present embodiment, a moving body is constituted by the piston 14 and the piston rod 15. The cylinder tube 12 is fixed to an outer mast (not shown), and the tip of the piston rod 15 is fixed to an inner mast (not shown).

At the lower portion of the cylinder tube 12, a flange portion 1 which contacts the piston 14 and restricts downward movement.
6 is provided, and a detection section chamber 18 having a bottom surface formed by a bottom piece 17 of the cylinder tube 12 is provided below the flange section 16. The piston 14 is configured to move to a predetermined stroke end provided above as an initial position as a reference position where the movement of the piston 14 is restricted.

In the detection section chamber 18, a wire winding section 19 is fixed on the bottom piece 17. Wire winding section 19
Is mounted on the cylinder tube 12 together with the bottom piece 17. The wire winding section 19 includes a spool support section 20 fixed to the bottom surface, and a spool 21 as a winding section supported by the spool support section 20.
The spool support 20 includes a support shaft 22 extending in the lateral direction.
Spring 2 as a biasing means for rotatably supporting the support shaft 22 and biasing the support shaft 22 to rotate to one side.
3 is provided. The spool 21 is supported so as not to rotate relative to the support shaft 22.

The spool 21 is integrally formed of a synthetic resin. The spool 21 has a cylindrical body portion 24 and a pair of flange portions 25a, 2 provided on both sides of the body portion 24.
5b. The body 24 has two flanges 25.
A wire 26 as a winding transmission member is wound in a range where the outer diameter does not become larger than a and 25b. Wire 26
Has one end fixed to the body portion 24 and the other end
And is connected to the lower surface of the piston 14. still,
The winding transmission member may be any member that can be wound around the spool 21 so as to be able to be fed and wound up.
In the present embodiment, a wire having a relatively small outer diameter having high tensile strength and flexibility is used.

As the piston 14 moves from the stroke end to the initial position, the spool 21
6 is wound a predetermined number of turns around the body 24 in a non-overlapping state to form a first layer, and then is further overlapped by the same predetermined number of turns without overlapping the wound first-layer wire 26. It is formed so as to be wound to form a second layer.
Further, the wire 26 is wound by a smaller number of turns than a predetermined number of turns without overlapping the formed second layer to form an incomplete third layer that does not fill the trunk 24. ing.

The spiral spring 23 allows the wire 26 wound on the spool 21 to be unwound as the piston 14 moves up and separates from the wire winding section 19, and the piston 14 moves down to allow the wire winding. The spool 21 is formed so as to bias the spool 21 so as to wind up the wire 26 that has been drawn out of the spool 21 as it approaches the take-up portion 19.

As shown in FIG. 2, a plurality of detected parts 2 are formed on the same end surface at equal angular intervals on a flange 25b as a rotating part on the opposite side of the spool supporting part 20.
7 are provided. Each detected part 27 is formed by embedding a magnetic material.

As shown in FIG. 1, a magnetic sensor 28 serving as a sensor is provided in the detection section chamber 18 of the cylinder tube 12 in a state where the detection section can be made to correspond to each detection section 27 provided on the flange section 25b. Is provided. Magnetic sensor 2
8 is screwed into a hole provided in the cylinder tube 12 and assembled. The magnetic sensor 28 is provided so as to detect the presence / absence of each of the detected parts 27 sequentially facing with the rotation of the spool 21. The magnetic sensor 28 is made up of a magnetic detecting element such as a magnetoresistive element and a Hall element. In the present embodiment, the state amount detecting means and the rotation amount detecting means are constituted by the flange portion 25b and the magnetic sensor 28.

Also, on the outer peripheral surface of the cylinder tube 12,
A magnetic sensor 29 is provided at a position opposite to the piston 14 arranged at the initial position in contact with the flange portion 16 as a reference state detecting means capable of detecting the presence or absence of the piston 14 at the initial position. The magnetic sensor 29 is fixed to the outer peripheral surface of the cylinder tube 12. The magnetic sensor 29 also includes a magnetic detection element such as a magnetoresistive element and a Hall element.

The lift lever 30 provided at the driver's seat (not shown) is provided with an operation detecting section 31 for detecting the operation direction. The operation detecting unit includes the lift lever 3
It has a limit switch (not shown) for detecting that 0 has been operated on the ascending side, and a limit switch (not shown) for detecting that it has been operated on the descending side.

On the machine base side, there is provided a stroke position detecting unit 32 as a stroke position calculating means to which the magnetic sensors 28 and 29 are electrically connected. The stroke position detection unit 32 includes the microcomputer 3
3 is provided. The magnetic sensor 28 outputs a pulse signal to the microcomputer 33 based on the presence / absence of each of the parts to be detected 27 sequentially facing with the rotation of the spool 21. The magnetic sensor 29 outputs an on / off signal to the microcomputer 33 based on the presence or absence of the piston 14 at the initial position. The operation detection unit 31 detects whether the lift lever 30 has been operated upward from the neutral state or whether it has been operated downward.

The microcomputer 33 determines whether the stroke position of the piston 14 is the initial position based on the ON / OFF signal. Microcomputer 3
3 stores a map M shown in FIG. The map M is formed so that the stroke position of the piston 14 can be obtained from the number of pulse signals input when the piston 14 moves from the initial position to the stroke end side. In the stroke position detecting device of the present embodiment, the wire 26 is wound around the spool 21 in a maximum of three layers according to the stroke position of the piston 14. Therefore, the winding diameter changes according to the stroke position of the piston 14, and the amount of rotation of the spool 21 per unit stroke amount changes. That is, the number of turns of the spool 21 per unit stroke amount is greater when the wire 26 is wound on the second and third layers than when the wire 26 is wound on the first layer. The momentum is reduced. That is, in the case of the second layer than the first layer, the piston 1 with respect to the interval at which the pulse signal is input is greater in the third layer than in the second layer.
The stroke amount of No. 4 increases. Therefore, the map M
When the wound state of the wire 26 is the second layer, compared to the state where the piston 14 moves from the initial position to the stroke end side in the state where the winding state of the wire 26 is the third layer,
Further, when the winding state is the first layer state, the graph is set as a graph in which the amount of change in the stroke position with respect to the pulse signal input interval decreases stepwise. The microcomputer uses the map M to determine the stroke position of the piston 14 based on the number of pulses from the initial position.

Further, the microcomputer 33 determines whether the lift cylinder 10 is in the up state or the down state based on the output from the operation detecting section 31. Then, the microcomputer 33 sets the current pulse number to a value obtained by adding the newly input pulse number to the previous pulse number when the new operation is rising, and calculates the current pulse number from the previous pulse number when the new operation is falling. A new stroke position is obtained by using the map M with the current pulse number obtained by subtracting the newly input pulse number.

Next, the operation of the stroke position detecting device for a hydraulic cylinder constructed as described above will be described. When the hydraulic oil is discharged from the oil chamber 13, the piston 1
4 is in the initial position and most of the wire 26 is
It is wound around. At this time, the piston 14 at the initial position is detected by the magnetic sensor 29, and based on the on / off signal, the microcomputer determines that the stroke position is the initial position.

When the lift lever 30 is moved upward,
Hydraulic oil is supplied to the oil chamber 13, and the piston 14 moves from the initial position to the stroke end side by a stroke amount corresponding to the supply amount and stops at a predetermined stroke position. At this time, the wire 26 is fed out of the spool 21 against the urging force of the spiral spring 23 with the movement of the piston 14, and the spool 21 rotates by a rotation amount corresponding to the stroke amount. Then, each detected part 27 moves so as to sequentially face the detecting part of the magnetic sensor 28, and the magnetic sensor 2
From 8, pulse signals corresponding to the stroke amount are output to the microcomputer 33 of the stroke detection unit 30. Since the piston 14 has risen from the initial position, the microcomputer 33 determines the stroke position of the piston 14 using the map M from the number of input pulse signals.

Next, when the lift lever 30 is operated downward, hydraulic oil is discharged from the oil chamber 13, and the piston 14 moves from the predetermined stroke position to the initial position by a stroke amount corresponding to the discharged amount. Stop at the new stroke position. At this time, with the movement of the piston 14, the wire 26 is wound around the spool 21 without being loosened by the urging force of the spiral spring 23, and the spool 21 rotates by a rotation amount corresponding to the stroke amount. Then, each detected part 27 moves so as to sequentially face the detection part of the magnetic sensor 28, and the microcomputer 3
The number of pulse signals corresponding to the stroke amount is output to 3. The microcomputer 33 uses the map M to calculate a new stroke of the piston 14 from the number of pulses obtained by subtracting the number of newly input pulse signals from the number of previous pulses since the piston 14 has descended from the stroke position previously obtained. Find the position.

As described in detail above, according to the stroke position detecting device for a fluid pressure cylinder of the present embodiment, the following effects can be obtained. (1) The stroke position of the moving body (piston 14)
A winding portion (spool 2) provided in the cylinder tube 12
It is fed out from 1) and is converted into a state quantity based on the turning state of the winding portion corresponding to the stroke position via a winding transmission member (wire 26) connected to the piston 14. This state quantity is detected by state quantity detection means (the winding part (spool 21) and the physical quantity sensor (magnetic sensor 28)) provided in the cylinder tube 12.

Accordingly, it is possible to avoid providing a detection unit for outputting a detection value of the rotation state of the winding unit corresponding to the stroke position outside the hydraulic cylinder (lift cylinder 10). The number of processing steps for providing the detection unit inside the cylinder can be reduced as compared with the fluid pressure cylinder.

(2) The amount of rotation of the winding part (spool 21) which is rotated by the winding transmission member (wire 26) with the movement of the moving body (piston 14) is detected. This rotation amount corresponds to the stroke amount of the moving body. Therefore, the stroke position can be obtained from the reference position and the stroke amount.

(3) The presence or absence of a plurality of detected parts 27 provided at equal angular intervals on the same circumference is detected by a rotation part (flange part 25) which rotates integrally with the winding part (spool 21). (Magnetic sensor 28), and the amount of rotation of the winding part is detected from the detected number. Therefore, the rotation amount of the winding portion can be detected without being affected by the detection error of the detection amount or the secular change due to wear of the detected portion or the detection portion, and the stroke position can be detected with high accuracy.

(4) The reference state detection means (magnetic sensor 29) detects that the moving body is at the reference position (initial position), and detects the turn of the winding portion when the moving body moves from the reference position. The stroke position (absolute value) of the moving body is obtained from the moving amount. Therefore, once the state at the reference position is detected, the stroke position can be detected only by detecting the amount of rotation that can be easily detected.

(5) The winding transmission member (wire 26) is wound around the winding portion (spool 26) so that the winding transmission member (wire 26) is sequentially layered when the moving body (piston 14) moves toward the winding portion. . Therefore, when the winding member is wound on the second or third layer, it is smaller than the amount of rotation per unit stroke amount of the moving body when the winding transmission member is wound on the winding portion on the first layer. The amount of rotation per unit stroke is smaller.
Then, the stroke position calculating means obtains the stroke position from the number of pulses using the map M formed according to the winding state of the winding transmission member. As a result, even when the winding transmission member is wound around the winding portion, the stroke position can be detected without any detection error due to the stroke position.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment only in that the wire winding section 19 and the magnetic sensor 28 of the first embodiment are changed to a wire winding section 40 and an eddy current displacement sensor 49. And different. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
Only the wire winding section 40 and the eddy current displacement sensor 49 will be described in detail.

In the detection section chamber 18 of the lift cylinder 10 according to the present embodiment, a wire winding section 40 is provided instead of the wire winding section 19. The wire winding section 40 includes a spool support section 41 fixed to the bottom surface of the detection section chamber 18,
And a spool 42 supported by the spool support portion 41. The spool support portion 41 rotatably supports the support shaft 43 extending in the lateral direction, and the support shaft 43.
Is provided with a spiral spring 44 for urging the one to rotate to one side. Further, the spool support portion 41 includes a speed reduction mechanism 45 that reduces the rotation amount of the support shaft 43 to a predetermined rotation amount of less than one rotation with respect to the entire movement range of the piston. The speed reduction mechanism 45 is a well-known mechanism constituted by a planetary gear, is a gear mechanism, and includes an output shaft 46 that outputs reduced rotation. The spool 42 is supported so as not to rotate relative to the support shaft 43.

The spool 42 has the same structure as the spool 21 and includes a body 24 and flanges 25a and 25b. A wire 26 is wound around the body 24, and its end is connected to the lower surface of the piston 14.

As the piston 14 moves from the stroke end to the initial position, the spool 42
6 is wound a predetermined number of turns around the body 24 in a non-overlapping state to form a first layer, and then is further overlapped by the same predetermined number of turns without overlapping the wound first-layer wire 26. It is formed so as to be wound to form a second layer.
Further, the wire 26 is wound by a smaller number of turns than a predetermined number of turns without overlapping the formed second layer to form an incomplete third layer that does not fill the trunk 24. ing.

The spiral spring 44 allows the wire 26 wound on the spool 42 to be unwound as the piston 14 moves up and separates from the wire winding section 40, and the piston 14 moves down to allow the wire winding. It is formed so as to bias the spool 42 so as to wind up the wire 26 being unreeled from the spool 42 as it approaches the take-up section 40.

An output shaft 46 of a speed reduction mechanism 45 extends from the wire winding section 40 to the opposite side of the spool 42.
A plate cam 47 is supported on the output shaft 46 so as not to rotate relatively. The plate cam 47 has a cam surface 48 whose distance from the center of rotation gradually changes from a minimum to a maximum with a predetermined rotation amount of the output shaft 46. The plate cam 47 is a good conductor, for example,
It is formed of aluminum, copper, or the like.

In this embodiment, the cam surface 4 of the plate cam 47 is
8, the distance from the outer peripheral side of the cam surface 48, that is, a predetermined position separated from the cam surface 48 to the cam surface 48 is proportional to the stroke position when the piston 14 moves from the initial position to the stroke end. It is formed so that it becomes. More specifically, when the wound state of the wire 26 corresponding to the predetermined stroke position of the piston 14 is the second and third layers, than when the wound state of the wire 26 is the first layer. , Wire 26 wound around body 24
Becomes larger. Therefore, the distance from the predetermined position to the cam surface 48 is relative to the absolute rotation position when the piston 14 is at the initial position as the reference position and when the piston 14 is at the stroke end as the maximum value.
The shape of the cam surface 48 is formed so that the rate of change gradually increases as the number of winding steps of the wire 26 around the spool 21 increases. As a result, the shape of the cam surface 48 is formed such that the distance from the predetermined position to the cam surface 48 is proportional to the stroke position of the piston 14.

An eddy current type displacement sensor (hereinafter, displacement sensor) 49 as a state quantity detecting means and a distance detecting means is supported at the bottom of the detecting section chamber 18. Displacement sensor 4
Reference numeral 9 is provided so that the detection unit 50 is opposed to the cam surface 48 of the plate cam 47, and detects the distance from the detection unit 50 to the cam surface 48 in a non-contact state. Displacement sensor 49
Are used in a state where an output voltage having a magnitude proportional to the distance to the cam surface 48 is output. Accordingly, the displacement sensor 49 outputs an output voltage having a magnitude proportional to the stroke position of the piston 14, as shown in FIG.

Outside the lift cylinder 10, a stroke detection unit 5 to which a displacement sensor 49 is electrically connected is provided.
1 is provided. The displacement sensor 49 outputs an output voltage of a magnitude corresponding to the stroke position of the piston 14 to the stroke detection unit 51 based on the distance from the detection unit 50 to the cam surface 48. Stroke detection unit 5
1 outputs an output voltage obtained by amplifying the output voltage with a predetermined amplification degree as a stroke position of the piston 14.

Next, the operation of the lift cylinder stroke position detecting device configured as described above will be described. When the lift lever 30 is changed from a state in which the lift lever 30 is raised or lowered to a neutral state, the supply and discharge of the hydraulic oil to the oil chamber 13 is stopped, and the piston 14 is stopped at a predetermined stroke position. At this time, the displacement sensor 49 outputs an output voltage having a magnitude corresponding to the distance from the detection unit 50 to the cam surface 48. The stroke detection unit 51 outputs the amplified output voltage as the stroke position of the piston 14.

As described in detail above, according to the lift cylinder stroke position detecting device of the present embodiment, the following effects can be obtained in addition to the effects described in (1) of the first embodiment. be able to.

(6) The stroke position of the piston 14 is converted by the speed reduction mechanism 45 into a distance from the predetermined position to the cam surface 48, and this distance is detected by the distance detecting means as an amount corresponding to the stroke position.

Accordingly, it is possible to detect the stroke position as an absolute value without detecting the state where the piston 14 is at the reference position, and it becomes unnecessary to return to the origin, which requires extra time. Further, unlike the conventional example or the first embodiment, there is no need to provide a detecting means for detecting the origin return, and the configuration can be simplified.

(7) The shape of the cam surface 48 of the plate cam 47 is determined according to the distance from the detection section to the cam surface 48.
4 was formed so as to be proportional to the stroke position. Therefore, the distance detecting means (the eddy current type displacement sensor 4
By setting 9) to output the output voltage proportional to the distance, an output voltage proportional to the stroke position can be obtained, and a process of converting the output voltage to the stroke position using the map M or a relational expression is performed. Means (microcomputer etc.) can be made unnecessary.

(8) A plate cam 47 formed of a good conductor
Is detected by an eddy current displacement sensor 49 in a non-contact manner. Therefore, the distance corresponding to the stroke position can be detected without the influence of aging due to wear of the detected portion or the detection portion, and the stroke position can be detected with high accuracy.

The embodiment is not limited to the above embodiment, but may be modified as follows. In the first embodiment, instead of detecting the detection target 27 formed of a magnetic material with the magnetic sensor 28, a proximity switch for detecting a predetermined detection target, or a reflection reflected by the detection target. A photoelectric switch for detecting light may be used.

In the first embodiment, the rotation amount of the spool 21 may be detected by a rotational displacement detector such as a potentiometer, a rotary encoder, or a magnetic rotation sensor. When using an absolute encoder,
The stroke position can be directly detected and the piston 1
The magnetic sensor 29 for detecting that 4 is at the initial position can be omitted.

In the first embodiment, the stroke detection unit 30 may calculate the stroke position from the output voltage using a predetermined formula instead of the map M.

In the first embodiment, the flange 25
b, two magnetic sensors 28 capable of detecting each of the detected portions 27 are provided at intervals smaller than the interval between the detected portions 27.
Then, the microcomputer 33 determines whether the lift cylinder 10 is in the up state or the down state according to which of the magnetic sensors 28 has detected the detected portion 27 first. In the stroke position detecting device, it is not necessary to provide the operation detecting unit 31 for detecting the operation direction of the lift lever 30.

In the first embodiment, the reference position is not limited to the initial position, but may be a stroke end, or may be a predetermined stroke position between the initial position and the stroke end.

In the second embodiment, the distance from the cam surface is detected by various displacement sensors other than the eddy current displacement sensor, for example, a variable displacement displacement sensor, a magnetoresistive displacement sensor, or the like. Is also good.

The detection may be performed by an ultrasonic distance sensor. In the second embodiment, the speed reduction mechanism is not limited to the planetary gear type, and may be, for example, a speed reduction mechanism composed of a combination of a pinion and a gear wheel.

In the second embodiment, the plate cam 47
A front cam (end face cam, Fac
e Cam). In the second embodiment, the shape of the cam surface 48 of the plate cam 47 has a shape in which the distance is not proportional to the stroke position, and a microcomputer as stroke position calculating means provided in the stroke position detection unit 51 is prepared in advance. The stroke position may be obtained from the distance by using a set map or a calculation formula. As shown in FIG. 6, biasing means (tension coil spring 61) such that the winding diameter of the spool 21 on which the wire 26 is superimposed and wound is brought into contact with the outer peripheral surface of the wound wire 26.
May be detected by a rotational displacement sensor (potentiometer 64) fixed to the input shaft 63. Then, the winding diameter is obtained from the detection value of the potentiometer 64 by the winding diameter calculation means (detection unit 65). On the other hand, the amount of rotation of the spool 21 corresponding to the change in the stroke position of the piston is detected by the flange 25b and the magnetic sensor 28. And
The detection unit 65 as a stroke calculation means obtains the length of the wire 26 from the winding diameter and the amount of rotation,
The stroke position may be obtained from the obtained length. Also in this case, the stroke position of the hydraulic cylinder having a large stroke range can be detected.

As shown in FIG. 7, the winding diameter of the spool 21 on which the wire 26 is superimposed and wound is detected by an ultrasonic distance detecting device including a transmitter 70 and a receiver 71. That is, the elapsed time until the ultrasonic pulse signal transmitted from the transmitter 70 is received by the receiver 71 is measured by the detection unit 72, and the distance over which the ultrasonic pulse signal is transmitted is calculated from the measured time. Then, the detection unit 72 as the winding diameter calculating means obtains the winding diameter from the distance. On the other hand, the amount of rotation of the spool 21 corresponding to the change in the stroke position of the piston is detected by the flange 25b and the magnetic sensor 28. Then, the detection unit 72 as the stroke position calculation means may obtain the length of the wire 26 corresponding to the stroke position of the piston from the winding diameter and the rotation amount, and may obtain the stroke position from the obtained length. Good. Also in this case, the stroke position of the hydraulic cylinder having a large stroke range can be detected. Further, since the winding diameter can be detected in a non-contact state with the wire 26, there is no portion that changes over time, and high reliability can be obtained.

In the first embodiment, only one layer may be wound around the body 24 without the wire 26 overlapping the spool 21. In this case, it is not necessary to perform a process of converting the number of pulses into a stroke position, and the stroke position can be calculated not only by the microcomputer but also by a logic circuit.

Similarly, in the second embodiment, the spool 4
Alternatively, only one layer may be wound in a state where the wire 26 does not overlap with the layer 2. In this case, since the winding diameter is the same regardless of the stroke position of the piston 14, the cam 47 may be formed so that the distance from the detection unit to the cam surface 48 increases at a constant rate of change. Becomes easier.

In the first or second embodiment, the belt-shaped winding transmission member may be wound around the reel-shaped winding portion so as to be sequentially overlapped. The winding transmission member is not limited to a wire made of various alloys, and may be a thin band-shaped member as long as it can be wound around a winding portion so as to be able to be wound out and wound up. You may. Further, the synthetic fiber is not limited to a metal and may be a synthetic fiber having a high tensile strength (for example, polyaramid fiber), or a belt-like body formed by knitting the synthetic fiber into a band.

The stroke position detecting device for a hydraulic cylinder which needs to detect a stroke position is not limited to a lift cylinder of a forklift. The hydraulic cylinder is not limited to a piston-type single-acting cylinder, but may be a ram-type cylinder.

The present invention is not limited to a single-acting cylinder, but may be applied to a single-rod or double-rod double-acting cylinder. Alternatively, the present invention may be applied to a single-acting or double-acting telescopic multi-stage cylinder.

The present invention is not limited to the hydraulic cylinder, but may be applied to other hydraulic cylinders. Further, the present invention is not limited to the liquid pressure cylinder but may be applied to a gas pressure cylinder. Hereinafter, technical ideas other than the claims that can be grasped from the embodiment will be described together with their effects.

(1) In the stroke position detecting device for a hydraulic cylinder according to claim 3, the detected portion is a magnetic portion, and the sensor is a magnetic sensor. According to such a configuration, the detected portion can be reliably detected even in the oil of the hydraulic cylinder.

(2) In the stroke position detecting device for a hydraulic cylinder according to claim 5, the winding diameter detecting means is provided such that an input shaft is parallel to a rotation axis of the winding portion. A rotational displacement sensor, fixed to the input shaft so as to extend in the radial direction from the input shaft, and having a distal end disposed at a position facing an outer peripheral surface of the winding transmission member wound around the winding portion; Arm, urging means for urging the arm so that the tip end of the arm comes into contact with the outer peripheral surface of the winding transmission member, and winding of the winding member wound around the winding portion A winding diameter calculating means for calculating a winding diameter of the winding transmission member from a detection value of the rotation displacement sensor with respect to a rotation position about the input shaft of the arm corresponding to a diameter. According to such a configuration, even when the winding transmission member is superimposed on the winding portion and wound, the stroke position can be detected without a detection error due to the stroke position.

(3) In the apparatus for detecting a stroke position of a hydraulic cylinder according to claim 5, the winding diameter detecting means includes an ultrasonic wave on an outer peripheral surface of the winding transmitting member wound around the winding portion. A transmitter that transmits a pulse signal, a receiver that receives an ultrasonic pulse reflected from the outer peripheral surface of the winding transmission member, and a transmitter that transmits an ultrasonic pulse signal and receives a reflected wave The distance that the ultrasonic pulse signal was transmitted was obtained from the elapsed time from the point at which the transmitter transmitted the ultrasonic pulse signal to the point at which the receiver received the reflected wave, and the distance was determined. And a winding diameter calculating means for obtaining a winding diameter of the winding transmission member from the distance. According to such a configuration, even when the winding transmission member is superimposed on the winding portion and wound, the stroke position can be detected without a detection error due to the stroke position. Further, the winding diameter can be detected without being affected by aging due to wear of the detected portion or the detecting portion, and the stroke position can be detected with high accuracy.

(4) In the stroke position detecting device for a fluid pressure cylinder according to any one of claims 7 to 9, the winding portion is provided when the moving body moves toward the winding portion. The plate cam is formed so that the distance between the cam surface and the detection unit is proportional to the stroke position of the moving body. Was. According to such a configuration, the output voltage proportional to the stroke position can be obtained even in the case of a hydraulic cylinder having a large stroke range by setting the distance detecting means to output an output voltage proportional to the distance. A means for converting the output voltage to the stroke position using a map or a relational expression can be omitted.

(5) A forklift equipped with the forklift lift cylinder according to claim 10. According to such a configuration, there is no possibility that the detection unit that detects the stroke position of the lift cylinder is broken, and the lift of the fork can be detected with high reliability.

[0083]

According to the first to ninth aspects of the present invention, it is possible to avoid providing a detection unit for detecting a state quantity corresponding to a stroke position outside the hydraulic cylinder. The number of processing steps for providing the detection unit inside can be reduced as compared with a conventional hydraulic cylinder.

According to the third aspect of the present invention, since only the presence or absence of the detected portion is detected, high reliability can be obtained without detecting errors or aging due to wear of the detected portion or the detecting portion.

According to the invention as set forth in claims 4 to 6, even when the winding transmission member is wound on the winding portion in a state where there is no detection error due to the stroke position. The stroke position of the fluid pressure cylinder can be detected.

According to the seventh aspect of the present invention, the stroke position can be detected by the absolute value without detecting the reference position, and troublesome return to origin can be eliminated. According to the invention described in claim 8 or claim 9, since the detected portion or the detecting portion does not wear and is not affected by aging, detection can be performed with high detection accuracy.

According to the tenth aspect of the present invention, it is possible to easily assemble a forklift having only a small installation space, and to detect the height with high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a stroke position detecting device provided in a lift cylinder for a forklift.

FIG. 2 is a front view of a france portion of the spool.

FIG. 3 is a graph showing a relationship between the number of pulses and a stroke position.

4A is a schematic front view illustrating a stroke position detecting device according to a second embodiment, and FIG. 4B is a schematic side view of the same.

FIG. 5 is a graph showing a relationship between an output voltage and a stroke position.

FIG. 6 is a schematic diagram showing another example of a stroke position detection device.

FIG. 7 is a schematic view showing another example of a stroke position detecting device.

FIG. 8 is a schematic view showing a conventional height detecting apparatus.

FIG. 9 is a schematic diagram showing a conventional stroke position detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Cylinder tube, 14 ... Piston which comprises a moving body, 15 ... Similarly a piston rod, 21 ... Spool as a winding part, 23 ... Spiral spring as urging means, 2
5b: a flange portion as a rotating portion constituting the state amount detecting means and the rotating amount detecting means; 26, a wire as a winding transmission member; 27, a detected portion; 28, a state amount detecting means and a rotating amount detecting means. Magnetic sensor as a constituent sensor, 2
9: a magnetic sensor as reference state detecting means; 30: a stroke detecting unit as stroke position calculating means;
45: speed reduction mechanism, 46: output shaft, 47: plate cam, 48:
Cam surface, 49: eddy current displacement sensor as state quantity detecting means and distance detecting means; 62, tension coil spring as urging means constituting winding diameter detecting means; 63, winding diameter detecting means Arm, 64: input shaft; 65, potentiometer as a rotational displacement sensor constituting winding diameter detecting means; 66, detecting unit as winding diameter calculating means and stroke position calculating means constituting winding diameter detecting means;
0: a transmission element constituting the winding diameter detection means; 71: a reception element; 72: a detection unit serving as a winding diameter calculation means and a stroke position calculation means constituting the winding diameter detection means;

Claims (10)

[Claims] 1. A cylinder tube, which is movably accommodated within a predetermined stroke range within the cylinder tube and partially extends outside from the cylinder tube. A fluid cylinder having a moving body that is relatively moved with respect to a tube; a winding that is rotatably provided at a position in the cylinder tube that does not interfere with the moving body, and that has a tip connected to the moving body. A transmission member is provided at a position where the moving body is wound so as to be able to be fed or wound with the movement of the moving body in the cylinder tube and does not interfere with the moving body in the cylinder tube. When the winding transmission member wound around the winding portion is allowed to be unreeled with the movement of the moving body in a direction away from the winding portion. In both cases, the winding portion is wound so that the winding transmission member that is being fed from the winding portion along with the movement of the moving body in a direction approaching the winding portion is wound around the winding portion. An urging means for urging to rotate, and a state for detecting a stroke position of the moving body within the stroke range or a state amount based on a rotation state of the winding portion corresponding to a change amount of the stroke position. An apparatus for detecting a stroke position of a fluid pressure cylinder, comprising a quantity detecting means. 2. The state amount is the amount of rotation of the winding part accompanying the movement of the moving body, and the state amount detection means is provided in the cylinder tube and determines the amount of rotation of the winding part. 2. The stroke position detecting device for a fluid pressure cylinder according to claim 1, which is a rotation amount detecting means for detecting. 3. The rotation amount detection means includes a plurality of detection portions provided so as to be integrally rotatable with the winding portion and provided at equal angular intervals on the same circumference around a rotation axis. And a sensor for detecting the presence or absence of each of the detected portions sequentially provided with the rotation of the winding portion and a detection portion provided in a state in which the detection portion is provided relative to each of the detected portions. The stroke position detecting device for a hydraulic cylinder according to claim 2. 4. The winding part is formed so as to wind the winding transmission member in an overlapping state, and the moving body is disposed at a reference position set at a predetermined stroke position within the stroke range. Reference state detecting means for detecting that the movable body has been moved from the reference position by the reference state detecting means. The stroke position detecting device for a fluid pressure cylinder according to claim 2 or 3, further comprising a stroke position calculating means for determining a stroke position of the hydraulic cylinder. 5. The winding part is formed so as to wind the winding transmission member in an overlapping state, and the state amount is a rotation amount of the winding part accompanying movement of the moving body, and A winding diameter of the winding transmission member wound around the winding portion, wherein the state amount detection means is provided in the cylinder tube and detects a rotation amount of the winding portion. Means,
The stroke position detecting device for a fluid pressure cylinder according to claim 1, further comprising a winding diameter detecting means provided in the cylinder tube and detecting a winding diameter of the winding portion. 6. A stroke position calculating means for obtaining a stroke position of the moving body from the turning amount detected by the turning amount detecting means and the winding diameter detected by the winding diameter detecting means. The stroke position detecting device for a hydraulic cylinder according to claim 5, further comprising: 7. A deceleration mechanism for decelerating the amount of rotation of the winding portion to a predetermined amount of rotation less than one rotation with respect to the entire moving range of the moving body; And a plate cam having a cam surface whose distance from the center of rotation gradually changes from a minimum to a maximum within a range of the amount of rotation of the plate cam. The state amount is determined by rotating the plate cam from a predetermined position separated from the cam surface. A distance from the cam surface in the radial direction of the dynamic shaft, wherein the state quantity detection means is supported in the cylinder tube such that a detection unit is opposed to the cam surface, and 2. A stroke position detecting device for a hydraulic cylinder according to claim 1, further comprising a distance detecting means for detecting said distance. 8. The plate cam is formed of a good conductor, and the distance detecting means includes an eddy current type displacement sensor which outputs an output voltage according to a distance to the cam surface in a non-contact state. 4. The stroke position detecting device for a hydraulic cylinder according to claim 1. 9. A stroke position detecting device for a fluid pressure cylinder according to claim 7, further comprising a stroke position calculating means for obtaining a stroke position of said moving body from said distance detected by said distance detecting means. . 10. A lift cylinder for a forklift, comprising the hydraulic cylinder stroke position detecting device according to claim 1. Description: