JPH0241408Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a device for detecting the operating direction of a directional control valve used in construction machinery and the like.

[Conventional technology]

Hydraulic cranes, which are an example of construction machinery, control the winch at the tip of the boom and the elevating and retracting of the boom by operating a directional control valve.If the directional control valve is operated incorrectly, it can cause a dangerous situation such as the crane falling over. may cause. Therefore, the operating direction detection device for the directional valve notifies the safety device that the directional valve is being operated in a dangerous direction.
Alternatively, it is said to be necessary for indicating in which direction a predetermined directional switching valve is operated using an indicator lamp provided in the driver's seat.

FIG. 3 shows a directional control valve V equipped with a conventional operating direction detection device. In the same figure, the directional control valve V has a spool 2 connected to the operating lever 1.
The spool 2 is provided with a main body 3 into which the spool 2 is slidably fitted, and a neutral position setting device 4 for returning the spool 2 to a neutral position. Also,
The operation direction detection device includes a bracket 5 fixed to the main body 3, a limit switch LS attached to the bracket 5, and a limit switch LS attached to the bracket 5.
The rod 9 is provided with a cam groove 8 that comes into contact with the detection end 7 of the rod 9, and the rod 9 is connected to the spool 2.

In the above configuration, when the spool 2 is in the neutral position, the detection end 7 of the limit switch LS is engaged with the cam groove 8, and the limit switch LS outputs, for example, an ON signal. When the spool 2 is moved to the right or left in the figure by the operating lever 1, the detection end 7 of the limit switch LS comes off the cam groove 8, and an off signal is output from the limit switch LS. Further, when the limit switch LS outputs an off signal at the neutral position, when the spool 2 is moved to the right or left in the figure by the operating lever 1, an on signal is output from the limit switch LS. Therefore, according to the operating direction switching valve shown in Fig. 3, by detecting whether an on signal or an off signal is output from the limit switch LS, it is possible to determine whether the spool is in the neutral position or in the right or left direction. It can be determined whether the direction is being operated.

However, in the operation position detection device described above, the signal when the spool 2 is operated to the right is the same as when the spool 2 is operated to the left. It is not possible to distinguish between the direction in which the device is being operated.

This problem can be solved by installing a plurality of limit switches and combining the signals output from these limit switches to determine the direction in which the spool is operated.

However, devices using these limit switches have problems in that the shape of the rod needs to be changed and the mechanism becomes complicated.

Therefore, an operation direction detection device was proposed in which the limit switch was replaced with a potentiometer.

This device connects the plunger of a potentiometer to a spool, and outputs an analog signal from the potentiometer according to the amount of movement of the spool.
The output signal was converted into a digital signal by a comparator to detect the operating direction of the spool.

[Problem that the invention attempts to solve]

However, since the conventional operation position detection device using a potentiometer outputs an analog signal from the potentiometer according to the amount of spool movement over the entire range of the spool movement, it is necessary to install an operation direction detection device. There was a problem in that the directional control valve became longer in the axial direction and larger.
For example, if the spool travel is set to be 10mm left and right from the neutral position, the potentiometer plunger will need an operating range of 20mm.

The object of this invention is to provide an operating direction detection device for a directional control valve that uses a potentiometer but does not increase in size.

[Means for solving problems]

In order to solve the above problem, the operation position detection device of this invention is a directional control valve having a spool slidably fitted into the main body, in which the plunger of the potentiometer is spaced apart from the end of the spool. The plunger is opposed to the spool, and a telescoping mechanism is interposed between the plunger and the spool, and the plunger is constantly urged by a spring force in a direction to protrude from the case of the potentiometer.
The expansion/contraction mechanism is always biased in the direction of expansion by a spring force greater than the spring force biasing the plunger, and a first stopper restricts the expansion limit when the spool moves in one direction. further comprising a second spool that prevents the expansion and contraction mechanism from advancing at a predetermined position as the spool moves to the other side.
It is characterized by having a stopper.

[Effect]

When the spool is in the neutral position, if the tip of the extended telescoping mechanism contacts the plunger of the potentiometer and the plunger is retracted into the case by a predetermined amount, the spool will move the plunger into the case. When the plunger is moved in the retracting direction, the stopper prevents the telescoping mechanism from moving forward before the plunger reaches its retraction limit, and even if the spool moves further, the telescoping mechanism will only contract and the plunger will not retract. . Further, when the spool is moved in a direction away from the plunger, the telescopic mechanism moves away from the plunger when the spool moves by a predetermined amount.

〔Example〕

The structure and operation of an embodiment of this invention will be explained below.

Figure 1 shows a potentiometer 10 on the directional control valve V.
Shown is the attached state.

In the figure, a potentiometer 10 is attached to a main body 3 of a directional control valve V via a mounting base 11. The mounting base 11 is provided with a large diameter hole 12 and a small diameter hole 13 adjacent to each other in the axial direction, and the end of the spool 2 of the directional control valve V is inserted into the large diameter hole 12. It is inserted. And spool 2
A spring 17 for returning the spool 2 to the neutral position is provided between the washer 14 fitted on the end of the washer 14 and the washer 16 disposed on the stepped part 15 at the boundary between the two holes 12 and 13. is mediated.
Reference numeral 18 denotes a telescopic mechanism extending from the end of the spool 2. This telescopic mechanism 18 is connected to the spool 2
an outer cylinder 19 fixed concentrically to the end of the outer cylinder 19; a retractable rod 20 fitted into the outer cylinder 19 so as to be freely retractable; and a retractable rod 20 disposed inside the outer cylinder 19 so as to project the retractable rod It consists of a spring 21 that is always biased in the direction, and a retaining ring 22 that is provided on the outer cylinder 19 and prevents the retractable rod 20 from falling off. Here, the retaining ring 22 also has the function of a first stopper that restricts the extension limit of the telescopic mechanism 18.

Next, the potentiometer 10 includes a plunger 24 that is provided in a case 23 so as to be able to move in and out.When the plunger 24 moves in and out of the case 23 (towards the right in the figure), the output voltage increases; When the plunger 24 protrudes from the case 23 (towards the left in the figure), the output becomes smaller, and the magnitude of the output voltage is proportional to the width of the retraction of the plunger 24 into the case 23. This relationship is shown in Figure 2. Further, the plunger 24 is always urged in the direction of protruding from the case 23 by a spring 25 built into the case 23, and its detection end 24a protrudes into the small diameter hole 13 of the mounting base 11. and is provided opposite to the tip of the retractable rod 20 of the telescopic mechanism 18. Here, the spring force of the spring 21 of the telescopic mechanism 18 is set to be stronger than the spring force of the spring 25 of the potentiometer 10.

In the above, when the spool 2 is in the neutral position, the plunger 24a is applied to the case 23 by a predetermined amount l ₀ by the retractable rod 20 biased by the spring 21.
Assume that only one member has been withdrawn. Spool 2 is spring 1
When moved from the neutral position set by 7 to the right in FIG. and exit to case 23. Therefore, since the output voltage of the potentiometer 10 rises above the voltage V ₀ at the neutral position along the voltage curve Z in FIG. 2, it is detected that the spool 2 has been operated to the right. Further, when the retractable rod 20 hits the inner wall end surface 26 of the small diameter hole 13, the plunger 24 is stopped at that position due to the action of the inner wall end surface 26 as a second stopper. When spool 2 is further moved to the right,
While the plunger 24 remains stopped, the retractable rod 20 retracts relative to the outer cylinder 19 against the bias of the spring 21, and the telescopic mechanism 18 is contracted.

Conversely, when the spool 2 is moved from the neutral position to the left in FIG. 1, the plunger 24 protrudes from the case 23 due to the bias of the spring 25 as the extension rod 20 retreats. Therefore, the output voltage of the potentiometer 10 follows the voltage curve Z in FIG.
Since it falls below V ₀ , it is detected that the spool 2 has been operated to the left. In addition, the exit and exit rods are 20
When the plunger 24 protrudes by l ₂ from the position shown in the figure due to the retreat of the plunger 24, the plunger 24 does not protrude after that due to the stopper provided on the plunger 24, and only the retractable rod 20 separates from the plunger 24 and retreats.

Here, when the spool 2 is in the neutral position, the length from the tip position of the retractable rod 20 to the inner wall end surface 26 of the small diameter hole 13, that is, the rightward stroke of the spool 2 is l ₁ , and If l ₁ = l ₂ , then
The detection end 24a of the plunger 24 is l ₁ from the neutral position.
When the sensing end 24a of the plunger 24 protrudes from the neutral position by _l2 , the voltage across _the potentiometer 10 becomes _V2 . An analog signal corresponding to the amount of movement of the spool 2 is obtained in the range between V ₁ and V ₂ . Then, the output voltages V ₁ and V ₂ of the potentiometer 10
is converted into an on/off digital signal by a circuit such as a comparator (not shown), and this on/off signal is
The operating direction of the spool 2 is determined based on the off signal.

[Effect of idea]

As explained above, the operation direction detection device of this invention can detect the direction of movement of the spool while minimizing the amount of movement of the plunger of the potentiometer, so it is possible to downsize the directional control valve, and Another advantage is that the neutral position of the spool and the mounting position of the potentiometer can be adjusted extremely easily simply by changing the output voltage value (set value) of the potentiometer.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the mounting state of the potentiometer and the directional control valve in the operation direction detection device according to the embodiment of this invention, FIG. 2 is a diagram showing the voltage curve of the potentiometer, and FIG. The figure is a schematic partial sectional view showing a directional control valve to which a conventional operation position detection device is attached. V... Directional switching valve, l ₁ , l ₂ ... Spool travel amount, 1... Operation lever, 2... Spool, 3...
Main body, 10... Potentiometer, 18... Telescopic mechanism, 21... Spring, 22... Retaining ring (first stopper), 23... Potentiometer case,
24... Plunger, 25... Spring, 26... Inner wall end surface (second stopper).

Claims (1)

[Scope of utility model registration request] In a directional control valve having a spool slidably fitted into a main body, a plunger of a potentiometer is opposed to an end of the spool at a distance, and a telescopic mechanism is provided between the plunger and the spool. is interposed, the plunger is always biased in the direction of protruding from the case of the potentiometer by a spring force, and the expansion/contraction mechanism is extended in the direction of extension by a spring force greater than the spring force biasing the plunger. and a first stopper that is always energized and limits the extension limit when the spool moves to one side, and further prevents the expansion mechanism from moving forward at a predetermined position as the spool moves to the other side. 1. An operation direction detection device for a directional control valve, comprising a second stopper.