JP3858737B2 - Cylinder speed control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder speed control device suitable for a cylinder in which a load is always applied in one direction.
[0002]
[Prior art]
In the crawler crane shown in FIG. 4, the lattice boom 51 provided in the upper swing body 50 cannot be expanded and contracted, so that it is disassembled during transportation.
[0003]
When the lattice boom 51 is assembled at the work site and attached to the upper swing body 50, the gantry 52 provided at the rear portion of the upper swing body 50 is set up. The gantry 52 is provided with two hydraulic cylinders 54a and 54b, and the gantry 52 is raised in the direction of arrow A by extending each cylinder in conjunction with each other.
[0004]
FIG. 5 shows a hydraulic control circuit for raising and lowering the gantry 52.
[0005]
When the gantry 52 is raised (raised), the control valve 55 is switched from the neutral position a to the b position by an operation signal, and the pressure oil from the hydraulic pump 56 is supplied to the head side 54 a of the hydraulic cylinder 54 through the check valve 57.
[0006]
On the other hand, when the gantry 52 is lowered (lowered), the control valve 55 is switched from the neutral position a to the c position, and pressure oil is supplied to the rod side 54 b through the conduit 58. However, in this gantry lowering operation, a fixed restrictor 59 corresponding to the weight of the gantry 52 is set so that the gantry 52 does not drop suddenly due to its own weight drop, and a relief valve is provided for excess oil generated in the pipe 58. It is trying to escape from 60 to the tank.
[0007]
[Problems to be solved by the invention]
By the way, since the gantry 52 that is erected is held in a predetermined posture by the gantry support portion 53 (see FIG. 4), the hydraulic cylinders 54a and 54b are no longer operated. Nevertheless, if the rod of the hydraulic cylinder 54 is left extended, the rod 54c may rust.
[0008]
Therefore, when the gantry 52 is not moved, the connecting pin that connects the rod 54c and the gantry 52 may be removed to reduce the rod 54c. At this time, no load (force in the reduction direction) is applied to the head side 54a, but the setting of the diaphragm 59 does not change, so the reduction operation of the rod 54c becomes extremely slow, and it takes time until it is completely stored in the tube. It will take.
[0009]
Although it is conceivable to make the hydraulic pump 56 a variable displacement type as a method for increasing the reduction speed, it is impractical to use a high cost for the undulating operation of the gantry 52 that is rarely used.
[0010]
The present invention has been made in consideration of the problems in the conventional hydraulic control circuit for gantry undulation as described above, and it is possible to reduce the difference in cylinder speed that occurs between when a load is applied and when it is not. The present invention provides a cylinder speed control device that can be used.
[0011]
[Means for Solving the Problems]
The present invention controls a cylinder that moves up and down while supporting a load, a pump that supplies pressure oil to the cylinder, and a direction and flow rate of the pressure oil that is interposed between the pump and the cylinder. Of the switching valve that connects the pump and the cylinder, provided in the load side pipeline where the load pressure acts, and in the non-load side pipeline where the load pressure does not act. And a relief valve for setting the pressure of the pipeline, and a cylinder speed control device for guiding the pressure of the load side pipeline and the pressure of the non-load side pipeline to the pressure port of the relief valve It is.
[0012]
According to the present invention, for example, when the cylinder is contracted while the load pressure is acting in the contracting direction, the pressure in the load side conduit is introduced into the pressure port of the relief valve. Since the pressure of the non-load side pipe line is also led to this pressure port, the relief pressure of the relief valve is eventually set low by the sum of both pressures. Thereby, when the load pressure is applied, the speed gradient of the cylinder becomes slow.
[0013]
Also, as the load pressure increases, the relief pressure gradually decreases as the load pressure increases, and the cylinder speed is controlled according to the load pressure.
[0014]
On the other hand, when no load is applied, no load pressure is established in the load-side pipeline, so the relief pressure of the relief valve is set only by the pressure of the non-load-side pipeline, and the relief pressure can be set high. As a result, the pipe pressure of the non-load side pipe becomes high, and the cylinder can be reduced by the pushing pressure that overcomes the throttle resistance.
[0015]
In the present invention, as a specific example of the cylinder, a cylinder supporting a gantry constituting a boom hoisting device for a crane is shown.
[0016]
If the present invention is applied to a hydraulic control circuit that raises and lowers a gantry, when the gantry is released and then the connection with the gantry is released to reduce the cylinder, the load pressure does not rise in the load side pipeline. It is possible to reduce the cylinder at a cylinder speed close to when the is acting.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
[0018]
FIG. 1 shows a cylinder speed control device according to the present invention applied to a gantry hoisting device.
[0019]
In the figure, reference numeral 1 denotes a gantry which is arranged behind the upper swing body of a crawler crane (not shown) and constitutes a boom hoisting device, and stands up by rotating in the direction of arrow A around a fulcrum 1a during operation.
[0020]
The gantry 1 is supported by a pair of hydraulic cylinders 2 provided in the vehicle width direction. The gantry 1 stands up by extending the rod 2a of the hydraulic cylinder 2, and the gantry 1 is contracted by reducing the rod 2a. 1 has been turned down. In the figure, only the front hydraulic cylinder 2 is shown.
[0021]
Next, the control circuit of the hydraulic cylinder 2 will be described.
[0022]
A fixed displacement hydraulic pump 4 is driven using the engine 3 as a drive source, and the direction and flow rate of the pressure oil discharged from the hydraulic pump 4 is controlled by a control valve 5.
[0023]
A remote control valve 6 for raising and lowering the gantry is connected to the pilot ports 5a and 5b of the control valve 5.
[0024]
When the remote control valve 6 is raised, the hydraulic signal acts on the pilot port 5a, and the control valve 5 switches from the neutral position a to the b position. On the other hand, when lowered, the hydraulic signal acts on the pilot port 5b, and the neutral position The position is switched from a to c.
[0025]
The pressure oil whose direction and flow rate are controlled by the control valve 5 is supplied to the hydraulic cylinder 2 through the supply / discharge passage 7.
[0026]
The supply / discharge passage 7 has a pipe line 7a that communicates with the rod-side oil chamber 2b of the hydraulic cylinder 2 and a pipe line 7b that communicates with the head-side oil chamber 2c. Since the hydraulic cylinder 2 supports the gantry 1 and the load pressure always acts in one direction (on the head side), the pipe line 7a is referred to as a non-load side pipe line in the following description. The pipe line 7b is called a load side pipe line.
[0027]
The load side pipe line 7b is provided with a slow return circuit 10 including a fixed throttle 8 as a throttle part and a check valve 9, and prevents the weight drop by the gantry 1 when the hydraulic cylinder 2 is reduced. Yes.
[0028]
On the other hand, the non-load side pipe line 7a is provided with a relief valve 11 for setting the pressure of the pipe line.
[0029]
The relief valve 11 includes two pressure ports 11a and 11b. One pressure port 11a is connected to a branch pipe 7b 'branched from the load side pipe 7b, and the other pressure port 11b is connected to the non-load side. It is connected to a branch pipeline 7a 'branched from the pipeline 7a. That is, both pressures of the load side pipe line 7b and the non-load side pipe line 7a are introduced into the pressure port of the relief valve 11.
[0030]
Here, the balance of pressure when the load W is acting is:
W = P _H · S _H −P _r · S _r (1)
It becomes. However, P _H : head side pressure, S _H : head side area, P _r : rod side pressure, S _r : rod side area.
[0031]
From the equation (1), the rod side pressure P _r is,
P _r = P _H (S _H / S _r ) − (1 / S _r ) W (2)
More demanded.
[0032]
Here, the head side area relative to the rod side area, that is, S _H / S _r = k,
P _r = kP _H − (1 / S _r ) W (3)
Is obtained.
[0033]
On the other hand, since the relief pressure is determined by the pressure receiving portion of the relief valve 11 and the spring pressure (pressure conversion value), the relief pressure P _k is
m · P _H + P _r = P _k (4)
It becomes. However, m: Area ratio of the branch path (head side) 11a and the branch path (rod side) 11b in the pressure port
(4) When determining the P _H by substituting (3) into equation
m · P _H + kP _H − (1 / S _r ) W = P _k
P _H = (P _k / (m + k)) + (1 / (S _r (m + k))) W (5)
Next, the head side pressure P _H is a linear function of the load W.
[0034]
Here, assuming k = 2 assuming a general hydraulic cylinder,
(5) P _H of the equation,
P _H = (P _k / (m + 2)) + (1 / (S _r (m + 2))) W (6)
It becomes.
[0035]
In the conventional hydraulic circuit, there is no branch path 7b for guiding the load side pipe pressure to the pressure port 11a.
P _H = P _k / 2 + (1 / (2S _r )) W (7)
It becomes.
[0036]
On the other hand, in this embodiment, if m = 1 (the area of the branch path (head side) 11a and the branch path (rod side) 11b in the pressure port is the same),
P _H = P _k / 3 + (1 / (3S _r )) W (8)
It becomes.
[0037]
FIG. 2 is a graph showing the relationship between the equations (7) and (8).
[0038]
As shown in the figure, when the load W increases from zero to W ₁ , for example, when the gantry 1 stands up in a nearly vertical state, the load W is close to zero, but the hydraulic cylinder 2 is gradually reduced. When the gantry 1 is turned down, the weight of the gantry 1 is applied to the hydraulic cylinder 2 and the load W increases.
[0039]
Thus, when the load increases, according to the head side pressure P _H characteristic L2 of the hydraulic control circuit of the present embodiment, compared to the head side pressure increase [Delta] P _H in the conventional head side pressure P _H characteristic L1, the head side pressure increase ΔP _H ′ can be suppressed to 66% (= 2/3).
[0040]
Thereby, the flow rate of the pressure oil passing through the throttle 8 (see FIG. 1) can also be reduced, and as a result, the speed difference of the hydraulic cylinder 2 caused by the presence or absence of a load can be reduced.
[0041]
The load W if the want the equivalent conventional head side pressure P _H of the head side pressure P _H in the case of zero, the relief pressure P _k, specifically Pk / 2 the spring pressure of the relief valve 11 in ÷ Pk / 3 = What is necessary is just to make it 3/2 times. Figure in the head side pressure P _H characteristic in this case is shown in L3.
[0042]
The case where the hydraulic cylinder 2 is reduced when the load W is zero means, for example, that the rod 2a is disconnected from the gantry 1 and the rod 2a is stored in the tube in order to prevent the rod 2a from rusting after the gantry 1 is stood. This is the case.
[0043]
Even when there is no load, adjusting the spring pressure of the relief valve 11 makes it possible to reduce the cylinder at a cylinder speed close to that when the load is applied.
[0044]
FIG. 3 shows a case where the area ratio m = 3 of the branch path (head side) 11a and the branch path (rod side) 11b in the pressure port (when k = 2).
[0045]
Head side P _H in this case,
P _H = P _k / 5 + (1 / (5S _r )) W (9)
Accordingly, the head side pressure increase amount ΔP _H ″ can be further reduced by the amount that the gradient of the head side pressure P _H characteristic L4 can be made sufficiently gentle, and the speed difference of the hydraulic cylinder 2 can be reduced.
[0046]
Also, L5 shows the head side pressure P _H characteristic when raised to 5/2 the relief pressure (spring pressure) from the characteristic L4. According to this characteristic L5, it is possible to reduce the indentation pressure at the time of load while ensuring the cylinder speed at the time of no load.
[0047]
In addition, although the said embodiment demonstrated the structure which a load acts on a cylinder reduction | decrease direction, this invention is applicable not only to this but the structure on which a load acts on a cylinder expansion | extension direction.
[0048]
【The invention's effect】
As is apparent from the above description, according to the present invention of claim 1, the pressure of the load side line and the pressure of the no load side line are introduced into the pressure port of the relief valve of the no load side line. For example, if the cylinder is contracted while the load is acting in the cylinder contraction direction, the relief pressure is set by the sum of both pressures, so that the cylinder speed gradient becomes slow. When no load is applied, no load pressure is generated in the load side pipeline. Therefore, the relief pressure of the relief valve is set only by the pressure of the non-load side pipeline, and the pipeline pressure of the non-load side pipeline increases, and the throttle resistance The cylinder can be reduced by the pushing pressure that overcomes the above.
[0049]
Thereby, the speed difference between the cylinders when the load is applied and when the load is not applied can be reduced.
[0050]
According to the present invention of claim 2, when the cylinder is contracted by releasing the connection with the gantry after the gantry is raised, the load pressure is applied even if the load pressure does not stand in the load side pipeline. Sometimes the cylinder can be reduced at near cylinder speeds.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a cylinder speed control apparatus according to the present invention.
FIG. 2 is a graph showing a head side pressure characteristic controlled by the hydraulic circuit of FIG.
FIG. 3 is a graph showing another head side pressure characteristic controlled by the hydraulic circuit of FIG. 1;
FIG. 4 is an external view of a conventional crawler crane with a gantry.
FIG. 5 is a hydraulic circuit diagram for raising and lowering the gantry of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gantry 2 Hydraulic cylinder 3 Engine 4 Hydraulic pump 5 Control valve 6 Remote control valve 7 Supply / discharge path 7a Non-load side pipe line 7b Load side pipe line 8 Restriction 9 Check valve 10 Slow return circuit 11 Relief valve 11a Pressure port 11b Pressure port

Claims (2)

A cylinder that moves up and down while supporting a load, a pump that supplies pressure oil to the cylinder, and a switch that is interposed between the pump and the cylinder and controls the direction and flow rate of the pressure oil that is supplied to the cylinder Among the pipes connecting the valve and the pump and the cylinder, provided in the load side pipe line where the load pressure acts and provided in the non-load side pipe line where the load pressure does not act. And a relief valve for setting the pressure of the pipe line, and a hydraulic control circuit comprising:
A cylinder speed control device, wherein the pressure of the load side pipe and the pressure of the non-load side pipe are led to a pressure port of the relief valve. 2. The cylinder speed control device according to claim 1, wherein the cylinder supports a gantry constituting a boom raising / lowering device of a crane.

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