JPH10238513A - Hydraulic cylinder, position detecting device for moving body, speed detecting device for moving body, and industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic cylinder to eliminate a fear of damage occurring due to contact with an obstacle, be hardly influenced by using environment, and besides continuously detect the position of the piston. SOLUTION: A lift cylinder 5 comprises a cylinder tube 8; a bottom block 9; a rod cover 10; a piston rod 6; and a piston 11 formed movably integrally with the piston rod 6. An ultrasonic sensor 19 is disposed in the chamber 20 of the bottom block 9 such that the transmission side is positioned opposite to the piston 11. The ultrasonic sensor 19 is electrically connected to a transmission and receipt circuit 33 and the transmission and receipt circuit 33 to a control device 34. Based on a control signal from the control device 34, the transmission and receipt circuit 33 transmits an ultrasonic transmission signal of a given frequency to the ultrasonic sensor 19 and an analogue electric signal outputted from the ultrasonic sensor 19 is converted into a pulse signal, which is outputted to the control device 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic cylinder,
The present invention relates to an industrial vehicle such as a forklift equipped with a moving body position detecting device, a moving body speed detecting device, and a moving body position detecting device.

[0002]

2. Description of the Related Art In a forklift, a lift cylinder is provided behind a mast, and the fork is moved up and down by driving the lift cylinder. Conventionally, in order to easily raise the fork to the loading position of the predetermined height, apart from raising and lowering the fork by operating the operation lever,
A forklift equipped with an automatic lifting device for automatically lifting a fork by operating an operation panel has been proposed (for example, Japanese Patent Application Laid-Open No. Hei 7-2496). In this device, the cargo handling controller that controls the drive of the lift cylinder grasps the position of the fork based on the detection signal of the lift sensor and stops the operation of the lift cylinder when the fork reaches the target position. Also, in order to prevent damage to the ceiling etc. due to masts due to careless lifting operations in indoor work where the height of the ceiling etc. is limited, the position of the fork is grasped by the detection signal of the height sensor, and the height is raised. Forklifts having a lift restriction function of restricting the height from becoming higher than a predetermined height have also been implemented.

Conventionally, a reel type sensor has been used as a lift sensor. The reel type height sensor includes a wire having one end connected to a fork, a reel around which the wire is wound, and a rotation detector (potentiometer) for detecting a rotation amount of the reel.

[0004]

However, since the conventional height sensor is equipped with a reel around which a wire is wound, there is a problem that the sensor is relatively large and requires a large installation space. . Further, there is a possibility that the wire exposed to the outside may be cut by contact with foreign matter. Further, there is also a problem that the dust easily enters due to the entry of dust and the like from the opening of the potentiometer, and the maintenance is troublesome. In particular, when working near the seashore or in an environment where salt water is used, breakdown is likely.

Instead of a reel-type lift sensor, a rack is provided on the mast, and a pinion meshing with the rack is provided so as to be able to move up and down integrally with the fork, and the rotation of the pinion is detected by a potentiometer. It is also conceivable to detect the lift height via a magnet embedded in the piston of the lift cylinder provided. However, in the case of a forklift, the mast has a large play, and it is difficult to detect with high accuracy by these detection methods, and the reliability is low. It is also conceivable to provide an optical sensor or an ultrasonic sensor to detect the position of the fork. However, in this case, there is a case where the path of light or ultrasonic waves is blocked and detection becomes impossible, and in the case of an optical sensor, there is a problem that detection accuracy is reduced due to dirt and reliability is lacking.

In an industrial vehicle such as a forklift,
In order to stabilize the vehicle during traveling, an axle supporting the rear wheels is swingably attached to the vehicle body. However, depending on the operating condition of the forklift, running stability may be reduced by allowing the axle to swing. To solve this inconvenience, Japanese Patent Laid-Open Publication No. 58-1672
Japanese Patent Publication No. 15 includes load detecting means for detecting that the load of the load on the fork has exceeded a predetermined weight, and lifting detecting means for detecting that the fork has risen to a predetermined height or more. There is disclosed a technique for fixing an axle when a heavy load and a high lift in which both means are in a detection state. In this case, since the lift used as a criterion for determining whether or not to fix the axle is a single height set in advance, it is necessary to set the height when the load of the load is heavy. However, the axle is fixed even in the case of a light load that does not need to be used, so that there is a problem that the slip of the front wheels easily occurs and the traveling performance is deteriorated. In order to solve this inconvenience, the applicant of the present invention continuously changes the lift, which is a criterion for determining whether to fix the axle, and fixes the axle with a combination of the lift and the load of the load or other conditions. The invention has invented a vehicle body swing control device for an industrial vehicle that determines whether or not to perform the determination. In this case, a lift sensor capable of continuously detecting the lift is required.

In a forklift, it is preferable that the moving speed of the fork is high in order to increase the working efficiency.
On the other hand, when stopping the fork at a predetermined position, it is desirable to stop the fork in a state where the impact is reduced as much as possible. If the fork is suddenly stopped with a high moving speed, the impact at the time of stopping becomes large. Therefore, a control is possible in which the fork is moved at a high speed to near the target position and then stopped after deceleration. In that case, it is necessary to detect the moving speed of the fork. To detect the moving speed, it is necessary to detect a position change per unit time.

Further, not only forklifts, but also industrial vehicles such as aerial work vehicles and backhoes equipped with a moving body that is moved by a cylinder, if the position and moving speed of the moving body can be easily detected, various controls are required. Can be easily performed. However, since the conventional sensor is disposed outside the moving body or the cylinder, it is difficult to secure the installation location, and the sensor is easily affected by the use environment. In addition, the sensor may be damaged by contact with an obstacle.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is that there is no possibility of damage due to contact with an obstacle, and it is hardly affected by a use environment. It is to provide a continuously detectable hydraulic cylinder. A second object is to provide a moving body position detecting device capable of continuously and easily detecting the position of a moving body moved by a hydraulic cylinder. It is an object of the present invention to provide a moving body speed detecting device capable of continuously and easily detecting the speed of a moving body. A fourth object is to provide an industrial vehicle provided with the position detecting device.

[0010]

According to a first aspect of the present invention, there is provided a hydraulic cylinder for transmitting an ultrasonic wave and receiving a reflected wave reflected by a piston. It is equipped with an ultrasonic sensor that outputs a converted electric signal.

According to a second aspect of the present invention, in the first aspect of the present invention, the ultrasonic sensor is provided on a side surface of the cylinder on a head cover side of the cylinder from a movement range of the piston, and is provided at a position facing the piston on the head cover. A reflecting member is provided for reflecting the ultrasonic waves transmitted from the ultrasonic sensor toward the piston and for reflecting the reflected waves from the piston toward the ultrasonic sensor.

According to a third aspect of the present invention, in the first or second aspect, the power medium is hydraulic oil. According to a fourth aspect of the present invention, there is provided a fluid pressure cylinder according to the third aspect, a control unit for controlling a transmission timing of ultrasonic waves from the ultrasonic sensor, and a transmission timing thereof. Calculating means for calculating the position of the moving body or the piston moved by the fluid pressure cylinder based on the input timing of the reflected wave.

According to a fifth aspect of the present invention, there is provided a fluid pressure cylinder according to the third aspect, and control means for controlling a timing of transmitting ultrasonic waves from the ultrasonic sensor; Calculating means for calculating the moving speed of the moving body or the piston moved by the fluid pressure cylinder based on the transmission time and the input time of the reflected wave.

In order to achieve a fourth object, an industrial vehicle according to a sixth aspect of the present invention includes the position detecting device according to the fourth aspect. In the invention described in claim 7, in the industrial vehicle described in claim 6, the fluid pressure cylinder is a lift cylinder of a forklift.

Therefore, according to the first aspect of the present invention, the ultrasonic wave transmitted from the ultrasonic sensor mounted on the hydraulic cylinder is reflected by the bottom surface of the piston and received by the ultrasonic sensor. Therefore, by connecting the ultrasonic sensor to the control device,
By measuring the time from when the ultrasonic wave is transmitted to when it is received, distance information to the piston can be obtained. In addition, since the ultrasonic sensor is provided in the fluid pressure cylinder, there is no possibility that the sensor may be damaged by contact with an obstacle, and the sensor is hardly affected by the use environment.

According to a second aspect of the present invention, in the first aspect of the invention, the ultrasonic sensor is provided on a side surface of the cylinder on a head cover side of the cylinder with respect to a movement range of the piston. Therefore, even if the arrangement position of the fluid pressure cylinder has little margin on the end face side of the head cover,
Maintenance of the ultrasonic sensor becomes easy.

According to the third aspect of the present invention, since hydraulic oil is used as the power medium of the fluid pressure cylinder, the transmission efficiency of ultrasonic waves is higher than when gas (for example, air) is used as the fluid. And the measurement conditions are stabilized.

In the position detecting device according to the fourth aspect of the present invention, the control unit controls the transmission timing of the ultrasonic wave from the ultrasonic sensor. Further, the position of the moving body or the piston moved by the fluid pressure cylinder is calculated by the calculating means based on the transmission time of the ultrasonic wave and the input time of the reflected wave from the piston.

In the speed detecting device according to the fifth aspect of the present invention, the control unit controls the transmission timing of the ultrasonic wave from the ultrasonic sensor. Further, the moving speed of the moving body or the piston moved by the hydraulic cylinder is calculated by the calculating means based on the transmission time of the ultrasonic wave and the input time of the reflected wave from the piston. The moving speed is calculated, for example, by measuring the position of the piston twice at a predetermined time interval and calculating the change over time, or by the Doppler method.

In the industrial vehicle according to the sixth aspect of the present invention, since the position detecting device according to the fourth aspect is provided, the position of the moving body or the piston moved by the hydraulic cylinder is calculated by the calculating means. .

In the industrial vehicle according to the seventh aspect of the present invention, the position of the fork can be continuously and easily detected, so that the stop position control or the like that requires the detection of the fork position is facilitated.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 3, a pair of left and right masts 3 are provided at the front of a vehicle body 2 of a forklift 1 as an industrial vehicle.
Is provided. The mast 3 includes an outer mast 3a and an inner mast 3b mounted inside the inner mast 3b so as to be able to move up and down. A lift bracket 4 having a fork 4a as a moving body is supported inside the inner mast 3b so as to be able to move up and down. A lift cylinder 5 as a fluid pressure cylinder is disposed behind each mast 3, and a tip of a piston rod 6 is connected to an upper portion of the inner mast 3b. A chain wheel (not shown) is supported on an upper portion of the inner mast 3b, and a chain (not shown) having one end connected to the lift bracket 4 and the other end connected to the upper portion of the lift cylinder 5 is hung on the chain wheel. Is equipped. The cargo handling lever 7 provided in the cab R
The fork 4a moves up and down along the mast 3 together with the lift bracket 4 by the expansion and contraction drive of the lift cylinder 5 by the above operation. A hydraulic cylinder that uses hydraulic oil as a power medium is used for the fluid pressure cylinder.

As shown in FIG. 1, a single-acting cylinder is used for the lift cylinder 5, and the cylinder cylinder 8, the bottom block 9 as a head cover, the rod cover 10, the piston rod 6, and the piston rod 6 move integrally. It is provided with a piston 11 formed so as to be able to be used with the bottom block 9 side facing down. The bottom block 9 is fixed to the cylinder tube 8 by welding, and the rod cover 10 is fixed to the cylinder tube 8 by screwing. The piston rod 6 penetrates through the insertion port 10a of the rod cover 10 and is inserted into the cylinder tube 8, and a seal member 12 is interposed in the insertion port 10a. An O-ring 13 is interposed between the outer peripheral surface of the distal end of the cylinder tube 8 and the inner surface of the rod cover 10. A substantially cylindrical restricting member 14 for restricting the protrusion of the piston rod 6 is fitted on the inner peripheral side of the upper end of the cylinder tube 8.
The position where the piston 11 contacts the lower surface of the regulating member 14 is the top dead center of the piston 11.

An exhaust port 15 is formed near the regulating member 14 in the cylinder tube 8. An overflow pipe 16 is fixed to the exhaust port 15, and air compressed by the piston 11 when the piston rod 6 protrudes (moves upward) is exhausted to a hose 17 through the overflow pipe 16.

The piston 11 is located above the bottom block 9.
A restricting surface 18 is formed in contact with the lower surface of the. In the bottom block 9, a chamber 20 for accommodating the ultrasonic sensor 19 is formed, and a port 21 for supplying and discharging hydraulic oil to and from the lift cylinder 5 is formed so as to open the chamber 20 to the side. . The port 21 is connected to a control valve 23 via a pipe 22. The control valve 23 is connected to an oil pump 24 via a pipe 25a and to an oil tank 26 via a pipe 25b. Further, a temperature sensor 27 is disposed in the chamber 20 as temperature detecting means for detecting the temperature of the hydraulic oil. The conduit 22 is connected to the port 21 via a flow regulator valve (not shown).

As shown in FIGS. 1 and 2, the ultrasonic sensor 19 is fixed to the bottom block 9 such that the transmitting side faces the piston 11. The ultrasonic sensor 19 includes a sensor vibrator 28 and a case 29 that supports the sensor vibrator 28.
And a cap 30 that covers the sensor vibrator 28. The sensor vibrator is generally called an ultrasonic transducer, and transmits (transmits) an ultrasonic wave by vibrating with an electric signal, and receives (receives) an ultrasonic wave reflected from an object to be detected and converts it into an electric signal. Works. The sensor vibrator 28 is attached to the cap 30 with an adhesive. The cap 30 is press-fitted and fixed to the case 29, and an O-ring 31 a is interposed between the inner peripheral surface of the end of the cap 30 and the outer peripheral surface of the case 29. A backing material (sound absorbing material) 32 is provided on the surface (back surface) of the sensor vibrator 28 opposite to the cap 30. A male screw portion 29a is formed in the case 29, and the male screw portion 29a is fixed to the bottom block 9 while being screwed into a mounting hole 9a formed in the bottom wall of the bottom block 9. An O-ring 31b is interposed between the bottom block 9 and the case 29. That is, in this embodiment, the ultrasonic sensor 1
9 is provided in a state of being built in the lift cylinder 5.

The material of the cap 30 is not particularly limited. However, since the quality of the frequency matching (acoustic impedance) changes depending on the material and thickness of the cap 30, an appropriate thickness is set according to the material. As the metal, iron and aluminum are preferable from the viewpoint of workability, strength and the like. In this embodiment, a metal cap 30 is used, and aluminum is used as its material. The case 29 is also made of metal.

The ultrasonic sensor 19 is electrically connected to the transmission / reception circuit 33. The transmission / reception circuit 33 is electrically connected to the control device. The transmission / reception circuit 33 includes an ultrasonic oscillator (not shown), and transmits (outputs) an ultrasonic transmission signal of a predetermined frequency to the ultrasonic sensor 19 based on a control signal from the control device 34. In addition, the transmission / reception circuit 33
Includes an amplifier and a detector (both not shown), and amplifies the analog electric signal output from the ultrasonic sensor 19, converts the analog electric signal into a pulse signal, and outputs the pulse signal to the controller 34.

The control unit 34 includes a CPU (central processing unit) 35 as a control unit and a calculation unit, and a counter 36 as a time counting unit that measures the time from outputting the ultrasonic transmission signal to receiving the reflected wave. And a storage device 37 for storing a control program, data necessary for calculating the position of the fork, and the like. The storage device 37 stores, for example, a relational expression or a map indicating the relationship between the temperature of the hydraulic oil and the speed of sound as the data. The temperature sensor 27 is provided in the chamber 20 and does not always coincide with the temperature of the hydraulic oil at a location on the path of the ultrasonic wave transmitted from the ultrasonic sensor 19. Therefore, the storage device 37 stores data based on a result of a test between the temperature detected by the temperature sensor 27 and the speed of sound, which is previously obtained on a trial basis. Control device 3
4 constitutes a position detecting device (lift detecting device) together with the ultrasonic sensor 19 and the transmitting / receiving circuit 33.

The temperature sensor 27 is electrically connected to the control device 34, and the CPU 35 calculates the temperature of the hydraulic oil in the lift cylinder 5 based on the detection signal of the temperature sensor 27.
The CPU 35 calculates the distance L from the ultrasonic sensor 19 to the bottom surface of the piston 11 based on the time t from the transmission of the ultrasonic wave to the reception of the reflected wave and the sound speed c in the hydraulic oil. Then, the position of the fork 4a is calculated from the value. Note that the time t is expressed by equation (1).

T = 2L / c (1) Next, the operation of the device configured as described above will be described. When the loading lever 7 is located at the neutral position, the pipeline 22
Is in a state in which communication with both pipe lines 25a and 25b is interrupted, neither supply nor discharge of hydraulic oil via the pipe line 22 is performed, and the piston rod 6 is held in a stopped state.

When the cargo handling lever 7 is operated to the raised position,
The control valve 23 is switched to a supply position where the pipe 22 and the pipe 25 a communicate with each other, and the hydraulic oil discharged from the oil pump 24 is supplied into the lift cylinder 5 through the pipe 22. As a result, the piston rod 6 is pushed up together with the piston 11 by the hydraulic oil supplied into the lift cylinder 5, and the fork 4a is raised.

On the other hand, when the cargo handling lever 7 is operated to the lowered position, the control valve 23 is switched to the discharge position for communicating the pipe 22 with the pipe 25b. As a result, the piston 11
The pressure due to the weight of the piston rod 6 and the weight of the fork becomes greater than the pressure of the hydraulic oil acting on the piston rod 6, the piston rod 6 descends together with the piston 11, and the hydraulic oil in the cylinder tube 8 is discharged. At this time, due to the action of the flow regulator valve, the lowering speed of the piston rod 6 is maintained substantially constant regardless of the difference in load such as the presence or absence of a load on the fork 4a.

When detecting the position of the fork 4a, the CPU 35 outputs a measurement request signal to the transmission / reception circuit 33 at predetermined time intervals longer than the maximum time required for reciprocation of ultrasonic waves.
The transmission / reception circuit 33 outputs an electric signal of a predetermined frequency to the ultrasonic sensor 19 based on the measurement request signal, and the ultrasonic sensor 19 outputs an ultrasonic wave of a predetermined frequency in response thereto. The ultrasonic wave output from the ultrasonic sensor 19 travels in the hydraulic oil. When the reflected wave (echo) reflected on the bottom surface of the piston 11 reaches the ultrasonic sensor 19, the ultrasonic sensor 19 outputs an electric signal corresponding to the received ultrasonic wave to the transmitting / receiving circuit 33. The transmission / reception circuit 33 amplifies the analog signal input from the ultrasonic sensor 19, converts the analog signal into a pulse signal, and outputs the pulse signal to the control device.

The sound velocity in the hydraulic oil is about 1400 m / sec, and the distance L from the ultrasonic sensor 19 to the lower surface of the piston 11 when the fork 4a is located at the highest elevation position is about 1.5 m. The maximum time required for the reciprocation of the ultrasonic wave is about 2.2 msec. Therefore, when continuously detecting the position of the fork 4a, the measurement request signal is output at intervals longer than this time. The frequency output from the ultrasonic oscillator depends on the type of hydraulic oil and the ultrasonic sensor 19.
Is set as appropriate depending on the type of, for example, 0.1 to 5 MH
A value on the order of z (megahertz) is used.

The CPU 35 transmits the measurement request signal to the transmission / reception circuit 3
The elapsed time from the point of time when the pulse signal is output to 3 is measured by the counter 36, and the measurement is terminated when the pulse signal is input from the transmission / reception circuit 33. The clock of a clock oscillator (not shown) is input to the counter 36 via a gate that functions so as to open only during the period from the output of the measurement request signal by the CPU 35 to the input of the pulse signal. And CPU3
5 calculates the time t from the transmission of the ultrasonic wave to the reception of the reflected wave based on the count value of the counter 36. Also, C
The PU 35 calculates the temperature of the hydraulic oil from the detection signal of the temperature sensor 27, and calculates the sound speed c at that temperature based on the data stored in the storage device 37. Next CPU35
Calculates the distance L from the ultrasonic sensor 19 to the bottom surface of the piston 11 from the equation (2) based on the time t and the sound speed c.

L = ct / 2 (2) The CPU 35 calculates the position H of the fork 4a from the relational expression between the distance L stored in the storage device 37 and the position (lift) H of the fork 4a. I do. The obtained position data of the fork 4a is used for, for example, forklift swing control.

Ultrasonic waves are output not only on the side facing the piston 11 but also on the opposite side by the vibration of the sensor vibrator 28. If the output of the ultrasonic wave to the side opposite to the piston 11 is left, the reflected wave becomes noise and the position detection accuracy of the fork 4a is reduced. However, the ultrasonic wave output from the sensor vibrator 28 to the side opposite to the piston 11 is absorbed by the backing material 32 provided on the back surface of the sensor vibrator 28. Accordingly, noise is reduced in the output signal from the ultrasonic sensor 19 to the transmission / reception circuit 33, and the position detection accuracy is improved.

When the ultrasonic sensor 19 is provided outside the lift cylinder 5 and the ultrasonic wave is transmitted to the reflecting member which moves up and down integrally with the fork 4a, the ultrasonic sensor 19 may generate a disturbance other than the reflected wave from the reflecting member. Ultrasonic waves are easily input directly to the ultrasonic sensor 19. In addition, there is a possibility that an ultrasonic wave or a reflected wave transmitted when an obstacle enters between the ultrasonic sensor 19 and the reflecting member is interrupted and erroneous detection or detection becomes impossible. However, when the lift cylinder 5 is equipped with the ultrasonic sensor 19, the ultrasonic sensor 19
However, even if there is an ultrasonic wave directed to, most of the ultrasonic wave is reflected by the lift cylinder 5, and there is almost no possibility that the external ultrasonic wave acts as a disturbance. Further, there is no possibility that the ultrasonic wave or the reflected wave transmitted from the ultrasonic sensor 19 is interrupted and erroneous detection or detection becomes impossible.

Further, since the ultrasonic sensor 19 is mounted on the lift cylinder 5, it is ensured that the ultrasonic sensor 19 is exposed to the atmosphere even in a bad environment such as near the coast or when using a saline solution. Avoided and less susceptible to use environment.

This embodiment has the following effects. (A) The position of the fork 4a is detected by using the ultrasonic sensor 19 mounted on the lift cylinder 5. Therefore, unlike a reel-type sensor or the like used in the prior art, there is no possibility of damage due to contact with an obstacle, and there is no need to secure a mounting space for the sensor. In addition, it is hardly affected by the use environment, and the reliability is improved even when working in a bad environment. Further, the device is less susceptible to disturbance and reliability is further improved.

(B) Since the transmission medium of the ultrasonic wave transmitted from the ultrasonic sensor 19 is hydraulic oil, the transmission efficiency of the ultrasonic wave is better than that when air is used as the medium, that is, the attenuation of the ultrasonic wave is small. And the measurement conditions are stabilized.

(C) Since the bottom surface of the piston 11 serves as an ultrasonic reflecting surface, there is no need to provide a separate reflecting member. (D) The CPU 35 detects the temperature of the hydraulic oil and calculates the distance from the ultrasonic sensor 19 to the piston 11 using the sound speed value in the hydraulic oil whose temperature has been corrected. Will be higher.

(E) The chamber 20 detected by the temperature sensor 27
The temperature of the sonic velocity is corrected based on the temperature in the chamber, and the correction data based on the result of the test of the temperature in the chamber 20 and the sonic velocity data in the hydraulic oil in the cylinder tube 8 is used.
Therefore, the correction can be performed favorably even when the detected temperature at a location other than the traveling path of the ultrasonic wave is used.

(F) Since the temperature sensor 27 is provided in the chamber 20, it is easy to secure the mounting position of the temperature sensor 27. (G) Since the backing material 32 is provided on the back surface of the sensor vibrator 28, noise is reduced in the output signal from the ultrasonic sensor 19 to the transmission / reception circuit 33.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. This embodiment differs greatly from the previous embodiment in that the traveling path of the ultrasonic wave between the ultrasonic sensor 19 and the bottom surface of the piston 11 is not straight but bent. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The bottom block 9 has two chambers 38 and 39.
Are formed, and both chambers 38, 39 are connected to a passage 40.
Are communicated through. The ultrasonic sensor 19 is screwed into a mounting hole 9a formed in the bottom block 9 so as to open the upper chamber 38 to the side. Ultrasonic sensor 19
Is fixed to the bottom block 9 in a state of transmitting ultrasonic waves in a direction orthogonal to the axial direction of the lift cylinder 5.
A reflection member 41 is provided in the chamber 38. The reflecting member 41 reflects the ultrasonic wave transmitted from the ultrasonic sensor 19 toward the piston 11 and
This serves to reflect the reflected wave from 1 toward the ultrasonic sensor 19. The reflecting member 41 is provided at the center of the chamber 38, and is disposed such that the planar reflecting surface forms an angle of 45 °. The reflection member 41 is formed of, for example, a metal plate. A flow regulator valve 42 is provided in a chamber 39 provided below the chamber 38, and the pipe 22 is connected to the flow regulator valve 42.

In this embodiment, the lift cylinder 5 is driven in the same manner as in the above embodiment, and the lift is detected by the position detecting device. From the ultrasonic sensor 19,
The ultrasonic wave is transmitted in a direction orthogonal to the longitudinal direction of the lift cylinder 5, but is reflected by the reflection member 41, the traveling direction is changed by 90 °, and the ultrasonic wave is directed to the piston 11. The reflected wave reflected by the lower surface of the piston 11 travels along the longitudinal direction of the lift cylinder toward the reflecting member 41 and is reflected by the reflecting member 41, so that the ultrasonic sensor 19
Is received. Therefore, this embodiment also has the same effects as (a), (b), (d) to (g) of the above embodiment.

When the ultrasonic sensor 19 is mounted on the bottom of the bottom block 9, the ultrasonic sensor 19 is mounted when the lift cylinder 5 is mounted on the forklift 1.
Is difficult to remove and maintenance work is troublesome. However, when the ultrasonic sensor 19 is provided on the side surface of the lift cylinder 5, the ultrasonic sensor 19 can be easily removed, so that maintenance of the ultrasonic sensor 19 becomes easy.

The embodiment is not limited to the above, and may be modified as follows, for example. In the first and second embodiments, the CPU 35 as the calculating means calculates the moving speed of the piston 11. For example, a program for calculating the moving speed is stored in the storage device 37. As a calculation method, for example, there is a method in which the position of the piston is measured twice after a predetermined time, and the difference between the measured positions, that is, the movement amount of the piston 11 is divided by the predetermined time. The measurement of the position of the piston 11 is performed in the same manner as in the first embodiment. In this case, the control device 34 constitutes a position detecting device and a moving speed detecting device of the moving body (fork 4a) together with the ultrasonic sensor 19 and the transmitting / receiving circuit 33.

When the so-called Doppler method is used, the moving speed V of the piston 11 can be calculated by one measurement based on the equation (3). Δf = 2Vf / c (3) where f is the frequency of the transmitted ultrasonic wave, Δf is the difference between the transmission frequency and the reception frequency, and c is the sound speed in the hydraulic oil.

In this case, the control device 34 is provided with a circuit for detecting the reception frequency. The CPU 35 calculates the frequency of the received signal instead of measuring the position of the piston 11, and calculates the difference Δf between the frequency of the transmitted ultrasonic wave and the received frequency. Then, the CPU 35 calculates the moving speed V of the piston 11 from Expression (4) obtained by modifying Expression (3).

V = (Δf / f) c / 2 (4) The obtained moving speed of the piston 11 is the same as the moving speed (elevation speed) of the fork 4a. For example, when the stop position control of the fork 4a is performed. Available to In this case, since position detection is not required, the control device 34 constitutes a moving speed detection device together with the ultrasonic sensor 19 and the transmission / reception circuit 33. The temperature sensor 27 may be mounted at a position other than inside the chambers 20 and 38. For example, it may be provided so as to be integrally movable with the piston 11 or may be embedded in the cylinder tube 8. Further, the temperature sensor 27 may be provided at a plurality of locations, and the temperature of the sound speed may be corrected based on the detected values. When a plurality of temperature sensors 27 are provided, the correction accuracy is improved, and the position detection accuracy of the piston 11 and the moving speed detection accuracy of the piston 11 are improved. The temperature correction may be performed without providing the temperature sensor 27. For example, the position of the piston 11 is measured in a state where the fork 4a is disposed at the lowest position or the highest position, that is, in a state where the position of the fork 4a is known in advance. Then, the sound speed c is calculated from the reciprocating time t of the ultrasonic wave at that time and the distance L to the bottom surface of the piston 11, and the sound speed c is used for the subsequent position calculation. By appropriately calculating the sound speed c, the position detection accuracy is improved. in this case,
Even without the temperature sensor 27, the temperature can be substantially corrected. A damping material is provided inside the case 29 in order to prevent vibrations and the like caused by lifting and lowering of the fork 4a from being input as noise to the sensor vibrator 28 via the lift cylinder 5 and the case 29. For example, urethane rubber, butyl rubber, or the like is used as the damping material. in this case,
The ultrasonic sensor 19 is less likely to be affected by disturbance, and the position detection accuracy and the moving speed detection accuracy are improved. The position data of the fork 4a and the piston 11 may be used not only for the swing regulation control but also for other controls such as the elevation regulation control and the automatic elevation stop control. The ultrasonic sensor 1 in a state where the lower surface (reflection surface of ultrasonic waves) of the piston 11 is arranged at the top dead center.
9 is formed on a curved surface having a radius of curvature. In this case, compared with the case where the reflection surface is a flat surface, the ultrasonic sensor 19
The reflected wave of the ultrasonic wave transmitted from is returned to the ultrasonic sensor 19 more efficiently. The mounting position of the ultrasonic sensor 19 may be the rod cover 10. In this case, the transmission medium of the ultrasonic wave transmitted from the ultrasonic sensor 19 is air, and the transmission efficiency of the ultrasonic wave is deteriorated. However, even if the ultrasonic sensor 19 is provided at a position facing the piston 11, attachment and detachment are easy. Thus, maintenance becomes easy.
However, it is necessary to increase the difference between the outer diameter of the piston rod 6 and the outer diameter of the piston 11 to secure the mounting position of the ultrasonic sensor 19 and the ultrasonic transmission space. ○ When the ultrasonic sensor 19 is mounted on the side of the cylinder, the ultrasonic sensor 19 is not limited to transmitting ultrasonic waves in the direction orthogonal to the direction of movement of the piston, but is mounted diagonally to intersect. Alternatively, the position of the reflection member may be changed. The lift cylinder 5 may be a single-acting cylinder instead of a single-acting cylinder. The invention is not limited to the lift cylinder 5 of the forklift 1, and may be applied to a hydraulic cylinder such as a tilt cylinder, a side shift cylinder, or a power steering cylinder. The ultrasonic sensor 19 may be provided in a state where the transmitted ultrasonic wave travels in the cylinder tube 8 toward the piston 11. The ultrasonic sensor 19 is not limited to the state arranged in the chamber 20. Piston 1 on the outer surface of the
It may be fixed at a position facing 1. In place of a configuration in which transmission and reception of ultrasonic waves are performed by one device, a configuration in which a transmission device and a reception device are separately configured may be used as the ultrasonic sensor. ○ Not only forklifts but also hydraulic cylinders used in industrial vehicles such as aerial work vehicles, backhoe vehicles and concrete pump vehicles equipped with moving bodies moved by cylinders (hydraulic cylinders) equipped with ultrasonic sensors. I do. Then, a position detecting device or a speed detecting device having the above-described configuration for detecting the position or the moving speed of the moving body or the piston using an ultrasonic sensor may be provided. In this case, various controls can be easily performed even on an industrial vehicle such as an aerial work vehicle and a backhoe vehicle. Further, the present invention is not limited to an industrial vehicle, and may be applied to a hydraulic cylinder used in another vehicle or a hydraulic device other than the vehicle. The present invention is not limited to the hydraulic cylinder, and may be applied to other hydraulic cylinders such as a pneumatic cylinder. ○ The flow regulator valve may be omitted.

The “industrial vehicle” referred to in this specification is:
A vehicle having a hydraulic cylinder and a moving body that is reciprocated by driving the hydraulic cylinder means not only a forklift but also an aerial work vehicle, a concrete pump vehicle, a backhoe vehicle, a dump truck, and the like.

The inventions other than those described in the claims that can be understood from the above embodiments will be described below together with their effects. (1) The fluid pressure cylinder according to any one of claims 1 to 3, further comprising a hydraulic oil temperature detecting unit. In this case, the temperature of the sound speed in the hydraulic oil can be easily corrected based on the detection signal of the temperature detection unit.

(2) In the invention as set forth in claim 4 or claim 5, the calculating means calculates the position or moving speed of the moving body or the piston by correcting the temperature of the sound speed in the hydraulic oil. In this case, the accuracy of the position or moving speed of the moving body or the piston is improved.

(3) An industrial vehicle provided with the speed detecting device according to claim 5. In this case, various controls that require the moving speed detection data of the moving body are facilitated. (4) An industrial vehicle provided with the position detecting device according to claim 4 and the speed detecting device according to claim 5. In this case, various controls that require the position detection data and the moving speed detection data of the moving body are facilitated.

(5) In the invention according to claim 4,
The position of the piston is detected with the piston moved to the top dead center or the bottom dead center, and the position of the moving body or the piston is calculated using the sound speed calculated based on the detection result.
In this case, the position can be detected in consideration of the temperature correction of the sound speed without measuring the temperature of the hydraulic oil.

[0060]

As described in detail above, claims 1 to 7 are provided.
According to the invention described in (1), since the ultrasonic sensor is mounted on the fluid pressure cylinder, there is no possibility that the sensor comes into contact with an obstacle and is damaged, and there is no need to secure a mounting space for the sensor. In addition, it is hardly affected by the use environment and disturbance, and the reliability is improved even when working in a bad environment.

According to the second aspect of the present invention, since the ultrasonic sensor is provided on the side surface of the cylinder, even if the arrangement position of the fluid pressure cylinder has almost no margin on the end face side of the head cover. In addition, maintenance of the ultrasonic sensor is facilitated.

According to the third aspect of the present invention, since the transmission medium of the ultrasonic wave transmitted from the ultrasonic sensor is hydraulic oil,
The transmission efficiency of the ultrasonic waves is better and the measurement conditions are more stable than when air is used as the medium.

According to the fourth aspect of the present invention, it is hardly affected by the use environment and disturbance, and the reliability of the position detection of the moving body is improved. According to the fifth aspect of the present invention, it is hard to be affected by the use environment and disturbance, and the reliability of detecting the moving speed of the moving body is improved.

According to the invention described in claim 6, various controls that require the position detection data of the moving body are facilitated.
According to the invention as set forth in claim 7, control such as forklift swing control and lift position control based on the position detection data of the moving body becomes easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lift cylinder according to a first embodiment.

FIG. 2 is a sectional side view of a main part of the same.

FIG. 3 is a side view of the forklift.

FIG. 4 is a sectional view of a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Forklift as an industrial vehicle, 4a ... Fork as a moving body, 5 ... Lift cylinder as a fluid pressure cylinder, 9 ... Bottom block as a cylinder cover,
11 ... Piston, 19 ... Ultrasonic sensor, 27 ... Temperature sensor, 28 ... Sensor vibrator, 33 ... Transceiver circuit, 34 ... Control device constituting control means, 35 ... CPU constituting control means and arithmetic means, 41 ... Reflective member.

Claims (7)

[Claims] 1. A fluid pressure cylinder equipped with an ultrasonic sensor that transmits an ultrasonic wave, receives a reflected wave reflected by a piston, and outputs an electric signal corresponding thereto. 2. An ultrasonic sensor is provided on a side surface of a cylinder on a side of a cylinder head cover from a movement range of a piston, and an ultrasonic wave transmitted from the ultrasonic sensor is directed to the piston at a position opposed to the piston of the head cover. 2. The fluid pressure cylinder according to claim 1, further comprising a reflecting member that reflects the reflected wave from the piston toward the ultrasonic sensor while reflecting the reflected wave. 3. The hydraulic cylinder according to claim 1, wherein the power medium is hydraulic oil. 4. A fluid pressure cylinder according to claim 3, control means for controlling a transmission timing of the ultrasonic wave from said ultrasonic sensor, and a hydraulic pressure based on the transmission timing and the input timing of said reflected wave. A calculating means for calculating the position of the moving body or the piston moved by the cylinder; 5. A fluid pressure cylinder according to claim 3, a control means for controlling a transmission timing of the ultrasonic wave from said ultrasonic sensor, and a hydraulic pressure based on the transmission timing and the input timing of said reflected wave. A moving unit for calculating a moving speed of the moving body or the piston moved by the cylinder; 6. An industrial vehicle comprising the position detecting device according to claim 4. 7. The industrial vehicle according to claim 6, wherein the fluid pressure cylinder is a lift cylinder of a forklift.