JPH01133899A - Controller for lift - Google Patents

Abstract

PURPOSE: To perform lifting work of a load always with an optimal speed characteristic, by detecting front and rear pressure of a throttle part of an oil passage to a hydraulic cylinder, and outputting control signals to a switching valve and a solenoid relief valve according to the operation of a control lever. CONSTITUTION: When a control lever 12 is operated upward, a proportional output signal is sent to a switching device 3-1 of a switching valve 3 through a control box 11, and flow of pressure oil from a hydraulic source 1 is proportionally fed to a cylinder 6 to raise a load 7. When the weight of the load 7 changes, this is detected as pressure change by a pressure sensor 9 on the switching valve 3 side of a restriction part 5, and a solenoid relief valve 4 is controlled so that pressure difference between the sensor 9 and an upstream pressure sensor 10. When the lever 12 is operated downward, a switching device 3-2 of the switching valve 3 is controlled by pressure difference between the sensors 8, 9 to make flow, or lowering speed of the load 7 constant. Thus, lifting work of a load always with an optimal speed characteristic can be always performed regardless of size of the load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-hydraulic control applied to a fortlift lifting device.

[Conventional technology]

As shown in Fig. 4, the conventional 7-tooth control system has a hydraulic power source l,
A control lever 12 that is a control device for the switching valve 3 with a flow rate control function, the hydraulic cylinder 6 for lift, and the switching valve 3
．． It is composed of an electric control box 11 that outputs an output for operating the switching valve in proportion to the amount of operation of the lever 12, and a fixed relief valve 23 is installed in the oil passage 20 upstream of the switching valve between the switching valve and the hydraulic cylinder. The oil passages 21 are provided with 7c1-regulator valves 22, respectively. Switching valve 3 raised,
It has the function of switching the oil path during lowering work and controlling the flow rate to control the speed of the hydraulic cylinder. Furthermore, when lowering the flow regulator valve 22, even if the switching valve is casually opened wide, the flow regulator valve 22 always controls the lowering speed to a constant level. The cylinder lowering speed is compensated for variations.

[Problem that the invention seeks to solve]

(1) Conventional lifting speed control of a forklift is performed by controlling the flow rate from the hydraulic pressure source 1 to the hydraulic cylinder 6 by changing the opening amount of the switching valve 3. However, since the opening area characteristics of this valve are fixed, the flow rate control characteristics vary greatly depending on the magnitude of the load 7.

In other words, the same speed characteristics cannot be achieved unless the opening degree is widened when the load is large and the opening degree is made small when the load is small. This change in raising speed characteristics depending on the magnitude of the load places a burden on the operator.

(2) Flow regulation control is pressure compensation, but there is a significant speed difference between the characteristics at no load and at maximum load. The lowering of the tab is slow when the load is empty, so if you adjust it to a faster speed, the next problem will occur, such as the lowering speed being too fast when the load is at maximum. Furthermore, it is unavoidable that the response time required to stabilize at the 70-regular rate adjustment value is relatively long in the prior art, which is a hydraulic pressure compensation mechanism.

[Means for Solving the Problems] (1) The flow rate passing through the flow control section (graining section) of the switching valve is proportional to the square root of the pressure difference between the upstream and downstream of the graining section. Therefore, if this pressure difference ΔP1 is constant, a constant flow rate can be controlled even if the load fluctuates. That is, by controlling the pressure P1t on the upstream side of the graining portion to the pressure P2 on the downstream side of the graining portion, which often occurs due to the load, - P1=P2+ΔP1, it becomes possible to control the flow rate with pressure compensation. This device uses the pressure sensor 9 to input the P2, and the P1ffi to the pressure sensor 9.
0 and 0 respectively as electrical signals and input into the control box 11. By applying an output signal such as p1=pz+ΔP1 to the electromagnetic relief valve 4 that controls P1, a foot 9 back circuit is constructed and the above control becomes possible.

(2) The flow rate Q passing through the fixed grain 5 installed in series in the circuit in place of the 70-regulator valve 22 is the pressure difference ΔPo upstream and downstream of the grain part, q=c, f9 There is a relationship between (C is a coefficient) Therefore, for flow regulation control that keeps the upper limit of the cylinder descending speed constant even if the load fluctuates, it is sufficient to control this ΔPo so that it does not always exceed a certain value. This device uses the pressure sensor 8.9 to
The control unit 3- of the switching valve 3 detects the PO and controls the control to prevent it from always exceeding a certain value through the control box 11.
2. Now, since the pressure drop of the wrinkled portion 5 is sensed by the pressure sensor, it is possible to detect even a very small value and obtain a signal. The absolute value of the pressure drop value can be made extremely small. For this reason, the pressure loss can be made extremely small, and the problem of the conventional problem of affecting the flow rate characteristics and causing a large speed difference between empty load and heavy load does not occur. Further, since ΔPo can of course be changed and adjusted as desired, it can be easily matched to the work and operator's preferences, resulting in improved lift work efficiency.

〔Example〕

In Figures 1 to 3, l is a hydraulic source, 2 is a hydraulic tank, 3 is a switching valve for elevation control with a flow rate control function, 3-1 is an auxiliary device for switching upwards, and 3-2 is an auxiliary device for switching downwards. 4 is an electromagnetic relief valve, 5 is a wrinkle part, and 6 is a glue 7 for lifting and lowering a load 7.
8 is a pressure sensor provided on the cylinder side with respect to the grained portion 5, 9 is a pressure sensor also provided on the switching valve side, and 10 is a pressure sensor provided on the hydraulic pressure source side with respect to the switching valve 3. Pressure oil from the hydraulic source 1 is connected to the switching valve 3 through an oil path 20, and
1 to a hydraulic cylinder 6.

The electric signal type control lever 12 and the electric control box 11 are connected by a signal line, and the signals of the pressure sensors 8.9 and 10 are input to the control box IIK through signal lines 14, 15, and 18, respectively, and the controlled output signal is connected to the switching device 3-1 via a signal line 16, to the switching device 3-2 via a signal line 17, and further to the electromagnetic valve 4 via a signal line 19.

Figure 1 shows the neutral state. Since the control lever 12 is neutral and therefore the switching valve 3 is also neutral, the pressure oil trapped in the hydraulic cylinder 6 is blocked by the switching valve 3 and the load 7 does not move. On the other hand, pressure oil from the hydraulic source 1 passes through the switching valve 3 and is transferred to the tank 2.

Figure 2 shows the rise. When the control lever 12 is operated to the upward side, an output signal proportional to this operation amount is sent to the switching device 3-1 of the switching valve 3 via the control box 11, and the spool of the switching valve is proportionally controlled, that is, the hydraulic pressure is The flow rate of pressure oil from the source to the cylinder 6 is controlled in proportion to the amount of operation of the control lever 12, and the load 7 is lifted. If the weight of the load 7 changes at this time, the pressure sensor 9 quickly detects the change in the load as a pressure change and sends it to the control box 11.

On the other hand, the pressure value converted into an electric signal is always sent from the upstream pressure sensor io of the switching valve 3 to the control box 11, and the control box keeps the pressure difference between the pressure sensors 9 and 10 at a constant value ΔP1. The output is sent to the electromagnetic relief valve 4 so that The electromagnetic relief valve 4 is configured to be controlled so that the pressure difference is always 8P1 in response to a change in the pressure value of the pressure sensor 9 when the load on the knob changes. Therefore, the pressure difference ΔP1 before and after the flow control section of the switching valve 3 always remains constant, so that the flow rate characteristics of the spool of the switching valve 3 remain constant without being influenced by load fluctuations. Here, a pressure compensation mechanism is established during meter-in flow rate control.

Figure 3 shows the descent. When the control lever 12 is operated to the lower side, the control box 1
1 to the control device section 3-2 of the switching valve 30, and when the switch is made, the pressure oil from the hydraulic source 1 is drained to the tank 2, while the oil trapped in the cylinder is transferred to the wrinkle section 5 and the flow rate control section of the switching valve 3. is drained to the p-tank and the load is lowered.

Signals from the pressure sensors 8.9 installed before and after the graining section 5 are sent to the control box 11, and the pressure sensors 8.9 are sent to the control box 11.
When the pressure difference of 9 exceeds ΔPoi, the output signal value decreases in the control box 1 in order to return the switching valve spool to the neutral side.
Controlled within 1. Therefore, regardless of the size of the load 70, the flow rate passing through the wrinkled portion 5, that is, the descending speed of the load is:
Controlled without exceeding a certain set point. A flow regulation mechanism is established here.

〔Effect of the invention〕

(1) Regardless of the size of the load, lifting and lowering of the load can always be done with the optimum speed control characteristics.

(2) Improving the responsiveness of flow regulating action and pressure compensation accuracy, and making adjustment easier, making lifting work more efficient.

(3) It is economical because the hydraulic flow regulator knob can be removed from the conventional circuit.

(4) Pressure loss in the circuit is reduced, resulting in energy savings.

[Brief explanation of the drawing]

1 to 3 are hydraulic circuit diagrams according to an embodiment of the present invention, in which FIG. 1 shows the state in neutral, FIG. 2 shows the state in the raising operation, and FIG. 3 shows the state in the lowering operation. FIG. 4 is a hydraulic circuit diagram of a conventional device. l...Hydraulic power source, 3...Switching valve, 4...
・Electromagnetic relief valve, 5... Grain 9 part, 6... Hydraulic cylinder, 8.9.10... Pressure sensor, 11...
・Control box,

Claims (1)

[Claims] An oil passage connecting the switching valve (3) and the hydraulic cylinder (6)
A pressure sensor (9) is placed on the valve (3) side of the throttle part (5) arranged in series with the cylinder (6), and a pressure sensor (8) is placed on the cylinder (6) side.
), a pressure sensor (10) is provided on the hydraulic pressure source (1) side of the valve (3), and each sensor electric signal is inputted, and the switching valve operating device (3-1), (3-2) and the switching valve A control box (11) that outputs a controlled output signal to the electromagnetic relief valve (4) installed upstream of (3), and an electric signal type lifting control that outputs to the switching valve (3) via the control box (11). An electro-hydraulic control type lift control device consisting of a lever (12).