JP5267896B2 - Hydraulic system and forklift equipped with the hydraulic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic system which enables an easy return to a predetermined ordered operation even if the predetermined ordered operation is lost, and a forklift including the hydraulic system. <P>SOLUTION: The hydraulic system includes: first piping 11 which connects a first hydraulic cylinder 5 and second hydraulic cylinder 6A; second piping 12A which connects the second hydraulic cylinder 6A and a hydraulic device 10A; third piping 12B which connects the hydraulic device 10A and the second hydraulic cylinder 6A together via a regulation means 9; and a control unit 19 which controls the regulation means 9. The control unit 19 regulates a flow rate of hydraulic oil by controlling the regulation means 9 when the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B do not operate in predetermined order. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a hydraulic system that raises and lowers a fork guided by a plurality of masts in stages, and a forklift including the hydraulic system.

  As shown in FIG. 4A, a conventional hydraulic system that raises and lowers a fork guided by a plurality of masts in stages is composed of an outer mast 3, a middle mast 23, and an inner mast 4 attached to the front of the vehicle body. A hydraulic system 1B including a stepped mast is known (see, for example, Patent Document 1).

  In the hydraulic system 1B having such a three-stage mast, the inner mast 4 is provided with a first hydraulic cylinder 5 that lifts and lowers the lift bracket 7 with the fork 8 via the chain 21. A chain wheel 20 for hanging the chain 21 on the upper side is provided. In addition, in the hydraulic system 1B, a chain wheel 24 for applying a chain 25 having one end fixed to the outer mast 3 and the other end fixed to the inner mast 4 is provided on the middle mast 23, and further, the upper end is the middle mast 23. A pair of left and right second hydraulic cylinders 6 </ b> A and 6 </ b> B connected to the upper beam 23 a is provided on the outer mast 3.

  As shown in FIG. 5, the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B include hydraulic cylinder bodies 5a and 6a, and hydraulic chambers 5b and 6b formed in the hydraulic cylinder bodies 5a and 6a, respectively. Piston rods 5c and 6c extending from the hydraulic cylinder bodies 5a and 6a are provided. The piston rod 6c of the second hydraulic cylinder 6A is formed with a flow path 6d through which hydraulic oil flows.

  The hydraulic chamber 5b of the first hydraulic cylinder 5 is connected to the piston rod 6c of the second hydraulic cylinder 6A through the first pipe 11. The hydraulic chamber 6b of the second hydraulic cylinder 6A is connected to the hydraulic device 10B via the second pipe 12A. The hydraulic chamber 6b of the second hydraulic cylinder 6B is connected to the hydraulic device 10B via the third pipe 12B.

  The hydraulic device 10B includes a control valve 13 that controls the flow of hydraulic oil, a hydraulic oil tank 14 that stores hydraulic oil, a hydraulic pump 15 that sucks and discharges hydraulic oil in the hydraulic oil tank 14, and a hydraulic pump 15 And a hydraulic motor 16 for driving the motor.

  In this hydraulic system 1B, the pressure in the hydraulic chamber 5b (hereinafter referred to as “the operating pressure of the first hydraulic cylinder”) necessary for extending the piston rod 5c of the first hydraulic cylinder 5 is usually set to the second hydraulic cylinder 6A, The pressure is set to be smaller than the pressure in the hydraulic chamber 6b necessary for extending the 6B piston rod 6c (hereinafter referred to as “the operating pressure of the second hydraulic cylinder”). Specifically, the inner diameter of the first hydraulic cylinder 5 is made larger than the inner diameters of the second hydraulic cylinders 6A and 6B, and the pressure receiving area of the piston rod 5c is made larger than the pressure receiving area of the piston rod 6c. Thus, in the hydraulic system 1B, when hydraulic oil is supplied from the hydraulic device 10B, the piston rod 5c of the first hydraulic cylinder 5 first extends (see FIG. 4B), and then the second hydraulic cylinder. A predetermined sequential operation in which the piston rods 6c of 6A and 6B extend (see FIG. 4C) is secured.

Japanese Patent Laid-Open No. 11-228094

  However, in the conventional hydraulic system 1 </ b> B, the first hydraulic cylinder 5 is connected to the second hydraulic cylinder 6 </ b> A via the first pipe 11, so that it is affected by the flow resistance of the hydraulic oil in the first pipe 11. The operating pressure of the first hydraulic cylinder 5 is apparently increased.

  For example, the flow resistance tends to increase as the average flow speed of the hydraulic oil increases. For this reason, in the conventional hydraulic system 1B, when the lift lever is largely tilted (when the lift lever is operated in a large amount), the number of rotations of the hydraulic motor 16 increases and the average flow speed of the hydraulic oil increases. The magnitude relationship between the operating pressure of the hydraulic cylinder 5 and the operating pressure of the second hydraulic cylinders 6A and 6B is easily reversed.

  When the magnitude relationship between the operating pressure of the first hydraulic cylinder 5 and the operating pressure of the second hydraulic cylinders 6A and 6B is reversed and a predetermined sequential operation is lost, the operating oil is manually adjusted by adjusting the operation amount of the lift lever. It is necessary to adjust the average flow rate. For this reason, the conventional hydraulic system 1B has a problem that once the predetermined sequential operation is lost, it takes time to restore the predetermined sequential operation.

  Although this problem seems to be avoided by further increasing the inner diameter of the first hydraulic cylinder 5 and reducing the operating pressure of the first hydraulic cylinder 5 in advance, the inner diameter of the first hydraulic cylinder 5 can be avoided. If the value is increased too much, the first hydraulic cylinder 5 is increased in size, which causes new problems such as deterioration of the forward field of view and cost increase. Further, if the inner diameters of the second hydraulic cylinders 6A and 6B are reduced instead of increasing the inner diameter of the first hydraulic cylinder 5, a problem of durability arises.

  The present invention has been made in view of the above circumstances, and the problem is that the hydraulic system can easily return to the predetermined sequential operation even when the predetermined sequential operation is lost. And providing a forklift having the hydraulic system.

In order to solve the above-described problems, a hydraulic system according to the present invention includes a first hydraulic cylinder that raises and lowers a lift bracket with a fork, an inner mast provided with the first hydraulic cylinder, and a pair of second hydraulic pressures that raise and lower the inner mast. A cylinder, an outer mast provided with a pair of second hydraulic cylinders, a plurality of pipes connecting the first hydraulic cylinder and the pair of second hydraulic cylinders, and the first and second hydraulic cylinders via the plurality of pipes A hydraulic system comprising a hydraulic device for supplying hydraulic oil,
The plurality of pipes are a first pipe that connects one second hydraulic cylinder and the first hydraulic cylinder of the pair of second hydraulic cylinders, and a second pipe that connects one second hydraulic cylinder and the hydraulic device. And a third pipe connecting the other second hydraulic cylinder of the pair of second hydraulic cylinders and the hydraulic device via a regulating means for regulating the flow rate of the hydraulic oil,
The hydraulic device includes a first detection unit that detects whether or not the operation amount of the first hydraulic cylinder has reached an upper limit, a second detection unit that detects the operation of the second hydraulic cylinder, and a first detection unit and a second detection unit. An order determination unit that determines whether or not the first and second hydraulic cylinders are operating in a predetermined order based on the detection result; and a control unit that controls the restricting unit based on the determination result of the order determination unit. And
The control unit is configured to restrict the flow rate of the hydraulic oil when the order determination unit determines that the first and second hydraulic cylinders are not operating in a predetermined order.

  According to this configuration, even if the operating pressure of the first hydraulic cylinder and the operating pressure of the second hydraulic cylinder are reversed for some reason, the control unit controls the regulating means and supplies it to the other second hydraulic cylinder. Therefore, the operating pressure of the second hydraulic cylinder increases and the magnitude relationship of the operating pressure is restored. Therefore, according to this configuration, even if the predetermined sequential operation is lost, it is possible to easily return to the predetermined sequential operation.

  Further, the hydraulic system is an encoder in which the second detection means detects the operation amount of the second hydraulic cylinder by detecting the raising and lowering of the inner mast with respect to the outer mast, and the control unit has an upper limit on the operation amount of the first hydraulic cylinder. If the operation amount of the second hydraulic cylinder exceeding the predetermined threshold is detected by the second detection means before reaching the value, the flow rate of the hydraulic oil is regulated so that the operation amount of the second hydraulic cylinder is less than the threshold. It is preferable to make it.

  According to this configuration, the control unit regulates the flow rate of the hydraulic oil so that the operation amount of the second hydraulic cylinder is equal to or less than a predetermined threshold value, so that the operating pressure of the second hydraulic cylinder is appropriately increased. Therefore, it is possible to return to the predetermined sequence operation more reliably.

  In order to solve the above problems, a forklift according to the present invention includes any one of the above hydraulic systems.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where predetermined | prescribed order operation | movement is lost, the forklift provided with the hydraulic system which can be easily returned to predetermined | prescribed order operation | movement, and this hydraulic system can be provided.

It is a side view of the forklift provided with the hydraulic system concerning the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic side view which shows sequential operation | movement of the hydraulic system which concerns on this invention, (A) is a figure which shows the state which the 1st and 2nd hydraulic cylinder contracted, (B) is the state which only the 1st hydraulic cylinder expanded. FIG. 8C is a diagram showing a state in which the first and second hydraulic cylinders are extended. 1 is a schematic configuration diagram of a hydraulic system according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic side view which shows the sequential operation | movement of the conventional hydraulic system, (A) is a figure which shows the state which the 1st and 2nd hydraulic cylinder contracted, (B) shows the state which only the 1st hydraulic cylinder expanded. FIG. 4C is a view showing a state where the first and second hydraulic cylinders are extended. It is a schematic block diagram of the conventional hydraulic system.

  Hereinafter, preferred embodiments of a hydraulic system and a forklift according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a side view of a forklift 1 provided with a hydraulic system 1A according to an embodiment of the present invention. As shown in the figure, the hydraulic system 1A according to the present embodiment includes a two-stage mast including an outer mast 3 attached to the front portion of the vehicle body 2 and an inner mast 4 provided inside the outer mast 3. ing.

  As shown in FIG. 2 (A), the inner mast 4 is provided with a first hydraulic cylinder 5 for raising and lowering a lift bracket 7 with a fork 8 via a chain 21, above the first hydraulic cylinder 5. A chain wheel 20 for hanging the chain 21 is provided.

  The first hydraulic cylinder 5 includes a sensor 17a ("first detection means" of the present invention) for detecting whether the operation amount of the first hydraulic cylinder 5 has reached the upper limit (whether the piston rod 5c has been fully extended). Is equivalent).

  The outer mast 3 is provided with a pair of left and right second hydraulic cylinders 6A and 6B whose upper ends are connected to the upper beam 4a of the inner mast 4.

  Further, the inner mast 4 includes a rotary encoder 17b (the “second detection” of the present invention) for detecting the operation amount of the second hydraulic cylinders 6A and 6B (the operation amount of the piston rod 6c) from the rising amount of the inner mast 4 with respect to the outer mast 3. Equivalent to the means ”is provided so as to be sandwiched between the inner mast 4 and the outer mast 3. The rotary encoder 17b and the sensor 17a are included in a hydraulic device 10A described later.

  As shown in FIG. 3, the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B include hydraulic cylinder bodies 5a and 6a, and hydraulic chambers 5b and 6b formed in the hydraulic cylinder bodies 5a and 6a, respectively. Piston rods 5c and 6c extending from the hydraulic cylinder bodies 5a and 6a are provided. The piston rod 6c of the second hydraulic cylinder 6A is formed with a flow path 6d for flowing hydraulic oil.

  The inner diameter of the first hydraulic cylinder 5 is larger than the inner diameters of the second hydraulic cylinders 6A and 6B, and the pressure receiving area of the piston rod 5c is larger than the pressure receiving area of the piston rod 6c. For this reason, the operating pressure of the first hydraulic cylinder 5 is smaller than the operating pressure of the second hydraulic cylinders 6A and 6B. The operating pressure of the second hydraulic cylinder 6A and the operating pressure of the second hydraulic cylinder 6B are substantially the same.

  The hydraulic chamber 5b of the first hydraulic cylinder 5 is connected to the piston rod 6c of the second hydraulic cylinder 6A through the first pipe 11. The hydraulic chamber 6b of the second hydraulic cylinder 6A is connected to the hydraulic device 10A via the second pipe 12A. The hydraulic chamber 6b of the second hydraulic cylinder 6B is connected to the hydraulic apparatus 10A via the third pipe 12B.

  The third pipe 12B is provided with a regulating means 9 that regulates the flow rate of the hydraulic oil. As the restricting means 9, a flow control valve that restricts the flow rate of the hydraulic oil between 0 to 100% by restricting the valve is used.

  The hydraulic device 10A supplies hydraulic oil to the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B. In addition to the sensor 17a and the rotary encoder 17b, a control valve 13 that controls the flow of hydraulic oil, The hydraulic oil tank 14 in which the hydraulic oil is stored, the hydraulic pump 15 that sucks and discharges the hydraulic oil in the hydraulic oil tank 14, the hydraulic motor 16 that drives the hydraulic pump 15, the first hydraulic cylinder 5, and the second hydraulic pressure It is determined whether or not the cylinders 6A and 6B are operating in a predetermined order (the order in which the piston rod 6c of the second hydraulic cylinders 6A and 6B extends after the piston rod 5c of the first hydraulic cylinder 5 extends to the upper limit). An order determination unit 18 and a control unit 19 that controls the restricting means 9 based on the determination result of the order determination unit 18 are provided.

  The order determination unit 18 receives detection results transmitted from the sensor 17a and the rotary encoder 17b at regular intervals, and determines whether the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are operating in a predetermined order. Determine. Specifically, the second hydraulic cylinder 6A, which detects that the operation amount of the first hydraulic cylinder 5 has not reached the upper limit by the sensor 17a and exceeds a predetermined threshold (preferably zero) by the rotary encoder 17b, When the operation amount of 6B is detected, it is determined that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are not operating in a predetermined order. Otherwise, the first hydraulic cylinder 5 and the second hydraulic cylinder 5 2 It is determined that the hydraulic cylinders 6A and 6B are operating in a predetermined order.

  When it is determined that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are operating in a predetermined order, the control unit 19 puts the valve of the regulating means 9 in a fully open state (flow rate 100%). Control to be. On the other hand, when it is determined that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are not operating in a predetermined order, the control unit 19 causes the operation amounts of the second hydraulic cylinders 6A and 6B to be equal to or less than a threshold value. In this manner, the valve of the regulating means 9 is throttled to regulate the flow rate of the hydraulic oil supplied to the hydraulic chamber 6b of the second hydraulic cylinder 6B.

  As shown in FIG. 3, the first hydraulic cylinder 5 is connected to the second hydraulic cylinder 6 </ b> A via the first pipe 11, and therefore is affected by the flow resistance of the hydraulic oil in the first pipe 11. The operating pressure of the first hydraulic cylinder 5 is apparently increased.

また、作動油の摩擦係数λ（作動油の動粘度）は、作動油の温度と反比例の関係を有しており、作動油の平均流速Ｖは、油圧モータの回転数と正比例の関係を有している。したがって、上式から、作動油の温度が低下した場合や油圧モータの回転数が上昇した場合に、作動油の通流抵抗が増加してしまうことが分かる。作動油の通流抵抗が増加すると、所定の作動圧力の関係（第１油圧シリンダ５の作動圧力＜第２油圧シリンダ６Ａ、６Ｂの作動圧力）が逆転する場合がある。 Here, the flow resistance of hydraulic oil (pressure loss due to friction) Δp [MPa] in the pipe is a friction coefficient λ that is directly proportional to the kinematic viscosity of the hydraulic oil, the density ρ [kg / cm ³ ] of the hydraulic oil, Based on the inner diameter d [cm], the length L [cm] of the pipe, and the average flow velocity V [cm / sec] of the hydraulic oil, it can be calculated by the following equation.

The friction coefficient λ of hydraulic fluid (dynamic viscosity of hydraulic fluid) is inversely proportional to the temperature of hydraulic fluid, and the average hydraulic fluid flow velocity V is directly proportional to the rotational speed of the hydraulic motor. doing. Therefore, it can be seen from the above formula that the flow resistance of the hydraulic oil increases when the temperature of the hydraulic oil decreases or when the rotational speed of the hydraulic motor increases. When the flow resistance of the hydraulic oil increases, the relationship of a predetermined operating pressure (the operating pressure of the first hydraulic cylinder 5 <the operating pressure of the second hydraulic cylinders 6A and 6B) may be reversed.

  Specifically, when the increase in the flow resistance of the hydraulic oil exceeds the difference between the operating pressure of the second hydraulic cylinders 6A and 6B and the operating pressure of the first hydraulic cylinder 5, the relationship between the predetermined operating pressures is reversed. Resulting in. In this case, in order to recover the relationship between the predetermined operating pressures, it is necessary to decrease the flow resistance of the operating oil and the operating pressure of the first hydraulic cylinder 5 or increase the operating pressure of the second hydraulic cylinders 6A and 6B. There is.

  In this regard, in the forklift 1 provided with the hydraulic system 1A according to the present embodiment, when the magnitude relation of the predetermined operating pressure is reversed, the control unit 19 throttles the valve of the regulating means 9 and is supplied to the second hydraulic cylinder 6B. The flow rate of hydraulic oil is regulated. As a result, the operating pressure of the second hydraulic cylinder 6B increases, and the magnitude relationship of the predetermined operating pressure is restored. Therefore, according to the forklift 1 provided with the hydraulic system 1A according to the present embodiment, even if the predetermined sequential operations in the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are lost, it is easily determined. The sequence operation can be restored.

  Next, a predetermined sequential operation in the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B will be described with reference to FIGS. 2 (A) to (C) and FIG.

  In the forklift 1 equipped with the hydraulic system 1A according to the present embodiment, when the lift lever of the driver's seat is operated in the state of FIG. 2A, the control valve 13 is opened, and the first hydraulic cylinder 5 and the second hydraulic cylinder 5 The hydraulic oil can be supplied to the hydraulic cylinders 6A and 6B. At this time, the valve of the regulating means 9 is completely open (flow rate 100%).

  The hydraulic motor 16 rotates according to the operation amount of the lift lever, and the hydraulic pump 15 sucks and discharges the hydraulic oil in the hydraulic oil tank 14. The hydraulic oil discharged from the hydraulic pump 15 is supplied to the hydraulic chambers 6b of the second hydraulic cylinders 6A and 6B through the second pipe 12A and the third pipe 12B at an average flow velocity corresponding to the rotational speed of the hydraulic motor 16. And is supplied to the hydraulic chamber 5b of the first hydraulic cylinder 5 through the flow path 6d of the second hydraulic cylinder 6A and the first pipe 11.

  While at least the hydraulic oil is being supplied to the hydraulic chambers 5b and 6b, it is detected by the sensor 17a whether the operation amount of the piston rod 5c of the first hydraulic cylinder 5 has reached the upper limit, and the rotary encoder 17b The movement amount of the piston rod 6c of the hydraulic cylinders 6A and 6B is detected. These detection results are transmitted to the order determination unit 18 at regular intervals.

  When the operation amount detected by the rotary encoder 17b is equal to or less than a predetermined threshold, the order determination unit 18 determines that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are operating in a predetermined order. The control unit 19 performs control so that the state of the regulating means 9 (flow rate 100%) is maintained. As a result, as shown in FIG. 2B, only the piston rod 5c of the first hydraulic cylinder 5 extends, and the fork 8 rises.

  On the other hand, if the operation amount detected by the rotary encoder 17b exceeds a predetermined threshold value, that is, the relationship between the predetermined operating pressure is broken and the piston rod 5c of the first hydraulic cylinder 5 is fully extended. When the piston rod 6c of the hydraulic cylinders 6A and 6B starts to extend, the order determination unit 18 determines that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are not operating in a predetermined order, and the control unit 19 performs feedback control so that the operation amount detected by the rotary encoder 17b is equal to or less than the threshold value, throttles the valve of the regulating means 9, and reduces the flow rate of the hydraulic oil supplied to the hydraulic chamber 6b of the second hydraulic cylinder 6B. Let it be regulated.

  When the flow rate of the hydraulic oil is restricted, the operating pressure of the second hydraulic cylinder 6B increases and the piston rod 6c of the second hydraulic cylinder 6B starts to contract. As a result, the inner mast 4 is supported only by the piston rod 6c of the second hydraulic cylinder 6A, so that the operating pressure of the second hydraulic cylinder 6A also increases apparently, and the piston rod 6c of the second hydraulic cylinder 6A also contracts. Begin to. That is, since the pressure relationship is restored by restricting the flow rate of the hydraulic oil, the piston rods 6c of the second hydraulic cylinders 6A and 6B are contracted, and the first hydraulic pressure as shown in FIG. Only the piston rod 5c of the cylinder 5 extends, and the fork 8 rises.

  Then, after the operation amount of the piston rod 5c of the first hydraulic cylinder 5 reaches the upper limit, the hydraulic oil is further supplied to the hydraulic chamber 6b of the second hydraulic cylinder 6A, 6B, and the hydraulic chamber of the second hydraulic cylinder 6A, 6B. When the pressure of 6b rises and reaches the operating pressure of the second hydraulic cylinders 6A and 6B, the piston rod 6c of the second hydraulic cylinders 6A and 6B extends as shown in FIG. It rises further.

  At this time, the operation amount exceeding the threshold is detected by the rotary encoder 17b, but it is also detected by the sensor 17a that the operation amount of the piston rod 5c of the first hydraulic cylinder 5 has reached the upper limit. 18 determines that the first hydraulic cylinder 5 and the second hydraulic cylinders 6A and 6B are operating in a predetermined order, and the control unit 19 is in a state in which the valve of the regulating means 9 is completely opened (flow rate 100%). Control to become.

  Eventually, in the hydraulic system 1A and the forklift 1 according to the present embodiment, the flow rate of the hydraulic oil supplied to the second hydraulic cylinder 6B by the control unit 19 is controlled by the control unit 19 even if the relationship between the predetermined operating pressures collapses. Therefore, the operating pressure of the second hydraulic cylinder 6B can be increased, and the predetermined operating pressure relationship can be recovered. Therefore, according to the hydraulic system 1A and the forklift 1 according to the present embodiment, even if the predetermined sequential operation is lost, it is possible to easily return to the predetermined sequential operation.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to the said structure, Various modifications can be considered.

  For example, in the above embodiment, the hydraulic system 1A including a two-stage mast including the outer mast 3 and the inner mast 4 has been described as an example. However, a three-stage as shown in FIG. A mast of the formula may be provided. In this case, the rotary encoder 17b can detect the operation amount of the second hydraulic cylinders 6A and 6B (the operation amount of the piston rod 6c) indirectly from the rising amount of the middle mast 23 with respect to the outer mast 3. And the middle mast 23 are preferably provided.

  Moreover, in the said embodiment, although the rotary encoder 17b which detects the operation amount of 2nd hydraulic cylinder 6A, 6B is used as a 2nd detection means, it replaces with this and other encoders, or simply 2nd hydraulic cylinder 6A. A sensor such as a limit switch for detecting the operation of 6B may be used. When the flow rate of the hydraulic oil is regulated using the limit switch, the control unit 19 regulates the flow rate of the hydraulic oil supplied to the hydraulic chamber 6b of the second hydraulic cylinder 6B by a preset ratio (for example, 50%). The valve of the restricting means 9 may be throttled so that the flow rate of the hydraulic oil is 0%, or the valve of the restricting means 9 may be completely closed.

  Furthermore, in the said embodiment, although the sensor 17a is used as a 1st detection means, if it can detect whether the operation amount of the 1st hydraulic cylinder 5 reached the upper limit, it can change arbitrarily.

  Further, the position where the first detection means such as the sensor 17a and the second detection means such as the rotary encoder 17b are provided can be arbitrarily changed.

  Furthermore, in the said embodiment, although the flow control valve is used as the control means 9, if it can control the flow volume of hydraulic fluid, it can change arbitrarily. For example, a valve capable of switching only ON (flow rate 100%) / OFF (flow rate 0%) may be used as the regulating means 9.

DESCRIPTION OF SYMBOLS 1 Forklift 1A Hydraulic system 2 Car body 3 Outer mast 4 Inner mast 5 1st hydraulic cylinder 6A, 6B 2nd hydraulic cylinder 7 Lift bracket 8 Fork 9 Restriction means 10A Hydraulic device 11 1st piping 12A 2nd piping 12B 3rd piping 13 Control valve 14 Hydraulic oil tank 15 Hydraulic pump 16 Hydraulic motor 17a Sensor (first detection means)
17b Rotary encoder (second detection means)
18 Order determination unit 19 Control unit

Claims (3)

A first hydraulic cylinder for raising and lowering a lift bracket with a fork, an inner mast provided with the first hydraulic cylinder, a pair of second hydraulic cylinders for raising and lowering the inner mast, and the pair of second hydraulic cylinders are provided. An outer mast; a plurality of pipes connecting the first hydraulic cylinder and the pair of second hydraulic cylinders; and a hydraulic device that supplies hydraulic oil to the first and second hydraulic cylinders via the plurality of pipes. Hydraulic system,
The plurality of pipes are
A first pipe connecting the second hydraulic cylinder of one of the pair of second hydraulic cylinders and the first hydraulic cylinder;
A second pipe connecting the one second hydraulic cylinder and the hydraulic device;
A third pipe connecting the other second hydraulic cylinder of the pair of second hydraulic cylinders and the hydraulic device via a regulating means for regulating the flow rate of the hydraulic oil;
Have
The hydraulic device is
First detection means for detecting whether or not the operation amount of the first hydraulic cylinder has reached an upper limit;
Second detection means for detecting the operation of the second hydraulic cylinder;
An order determination unit that determines whether the first and second hydraulic cylinders are operating in a predetermined order based on detection results of the first and second detection means;
A control unit that controls the restricting means based on a determination result of the order determination unit;
Have
The control unit restricts the flow rate of the hydraulic oil when the sequence determination unit determines that the first and second hydraulic cylinders are not operating in the predetermined sequence. The second detection means is an encoder that detects an operation amount of the second hydraulic cylinder by detecting the movement of the inner mast with respect to the outer mast,
When the operation amount of the second hydraulic cylinder that exceeds a predetermined threshold is detected by the second detection means before the operation amount of the first hydraulic cylinder reaches the upper limit, the control unit performs the second operation. The hydraulic system according to claim 1, wherein a flow rate of the hydraulic oil is regulated so that an operation amount of the hydraulic cylinder is equal to or less than the threshold value.   A forklift comprising the hydraulic system according to claim 1.

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