JPH044358A - Hydraulic closed circuit with neutral communication valve - Google Patents

Abstract

PURPOSE:To prevent a vehicle from coasting as well as to keep cargoes from falling down, and protect a driver from feeling unpleasant to a great extent by constituting a neutral communication valve to be switched so as to be held at a communication position only when an actuating lever continuously remains at a neutral position beyond the specified period of time. CONSTITUTION:A neutral communication valve 5 is switched over by a switch control means 20 to a communication position (a) only when an actuating lever 4 continuously remains at a neutral position N beyond the specified period of time. When the actuating lever 4 is therefore, switched over, for example from a normal rotation position F to the neutral position N, and is then switched over to a reverse rotation position R before the specified time elapses, the neutral communication valve 5 is held at an interruption position (b). As a result, main lines 11 and 12 are not mutually communicated, a hydraulic motor 2 will never thereby be rotated by inertia.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a hydraulic closed circuit used in, for example, a wheel loader or a forklift, which is equipped with a neutral communication valve.

B. Prior Art FIG. 4 shows an example of a hydraulic closed circuit for a conventional wheel loader.

In FIG. 4, the double tilting type variable displacement hydraulic pump 1 is as follows:
A pair of main pipes 11. ．． The hydraulic motor 2 is connected to the hydraulic motor 2 via the hydraulic pump 12, and the hydraulic motor 2 is rotated by the oil discharged from the hydraulic pump 1. Reference numeral 3 denotes a pump regulator that controls the tilt angle of the hydraulic pump 1, and controls the pressure oil discharge direction by operating a forward/reverse switching lever (operation lever) 4. The operating lever 4 is in the forward position (F position: forward rotation w) and the reverse position (N
It is possible to switch between three positions: reverse position) and neutral position (N position).

In addition, an electromagnetic neutral communication valve 5 is provided in the pipe line 3 connecting the main pipe lines 11 and 12, and the neutral communication valve 5 is at position a (communication position) where the main pipe lines 11 and 12 are connected. and a position b (blocking position M) that blocks both. This switching operation of the neutral communication valve 5 is performed by operating the forward/reverse switching lever 4.

When the operating lever 4 is in the N position, the pump regulator 3 makes the tilting angle of the hydraulic pump 1 zero, so that no pressure oil is discharged from the hydraulic pump 1.

When the operating lever 4 is switched to the F position in this state, the pump regulator 3 controls the tilt angle of the hydraulic pump 1 to discharge pressure oil to the main pipe line 11 side. Further, by switching the lever 4 to the F position, the contact 4a at the base end of the lever comes into contact with the contact 6b, and the solenoid part 5a of the neutral communication valve 5 is excited by the voltage of the power supply 7, and as a result, the neutral communication valve 5 moves from the a position to the contact 6b. It is switched to position b and the main lines 11, 12 are cut off. Therefore, the oil discharged from the hydraulic pump 1 is guided to the hydraulic motor 2 through the conduit 11, and the hydraulic motor 2 is rotated in the normal direction, and the rotation rotates the wheels via a reduction gear (not shown), etc., and the vehicle moves forward. Further, the oil discharged from the hydraulic motor 2 returns to the hydraulic pump through a conduit 12.

Also, when the lever 4 is switched from the N position to the N position,
The pump regulator 3 controls the tilting angle of the hydraulic pump 1 to discharge pressure oil to the main pipe 12 side, while the lever 4
The contact point 4a contacts the contact point 6a, and the neutral communication valve 5 is switched from the a position to the off position as described above, and the hydraulic motor 2 is reversed by the pressure oil discharged into the main pipe line 12, and the vehicle moves backward.

On the other hand, when the forward/reverse switching lever 4 is switched from, for example, the F position to the N position, the tilt angle of the hydraulic pump 1 becomes zero and the discharge of hydraulic pressure is cut off, and the contact 4a of the lever 4 changes to the contact 6.
Since the solenoid part 5a is demagnetized and the neutral communication valve 5 is switched to the position a, the main pipes 11 and 12 are communicated with each other. As a result, the oil discharged from the hydraulic motor 2 is transferred to the pipe line 12.
, 13° 11 and returns to the hydraulic motor 2, so that the vehicle can coast when the lever is in the neutral position.

Problems to be Solved by the C0 Invention However, the conventional hydraulic closed circuit described above has the following problems.

In other words, in wheel loaders, forklifts 1, etc.,
For example, switching from forward to reverse or from reverse to forward at once, such as when moving backward after excavating earth and sand using the front, and then moving forward to load earth and sand into a dump truck (in the case of a wheel loader). is frequent. In such a case, the forward/reverse switching lever 4 is set to N.
The position is switched from the N position to the F position, but while passing through the N position, the neutral communication valve 5 is switched to the communication position a, and as a result, the hydraulic motor 4 temporarily rotates by inertia, and the vehicle coasts. . After that, when the lever 4 reaches the F position, the neutral communication valve 5 switches to the B position again to exit the coasting run, but when entering and exiting the coasting run, the pressure is applied to the hydraulic motor 2. If the supply of pressurized oil is suddenly cut off or suddenly supplied, a shock may occur to the vehicle.
This may cause the cargo to spill or cause discomfort to the driver.

A technical object of the present invention is to prevent the hydraulic motor from rotating due to inertia even when the operating lever is switched from the normal rotation position (reverse rotation position) to the reverse rotation position W (normal rotation position).

To explain this in conjunction with FIG. 1 showing an embodiment of means for solving the problem, the present invention includes a double tilting type variable displacement hydraulic pump 1, and a pair of main pipes 11. ．． The hydraulic motor 2 is connected in a closed circuit through the hydraulic pump 1 and is driven by the oil discharged from the hydraulic pump 1. There is an operating lever 4 that can be switched to a neutral position N for commanding a stop, and when the operating lever 4 is switched to a forward rotation position F or a reverse rotation position R, it is switched to a blocking position that blocks the pair of main pipes 11 and 12. , when switched to neutral position N, both pipes 1
Neutral communication valve 5 switched to communication position a that communicates 1 and 12
Applicable to hydraulic closed circuits with Further, a switching control means 20 is provided which switches the neutral communication valve 5 to the communication position a only when the operating lever 4 is continuously in the neutral position N for a predetermined period of time, thereby achieving the above technical problem.

80 action switching control means 20 switches the neutral communication valve 5 to the communication position a only when the operating lever 4 is in the neutral position N for a predetermined period of time or more. According to this, when the operating lever 4 is switched from, for example, the forward rotation position F to the neutral position N, and then switched to the reverse rotation position R before the predetermined time period elapses, the neutral communication valve 5 maintains the cutoff position. . Therefore, the main pipes 11 and 12 are not communicated with each other, and the hydraulic motor 2 does not rotate due to inertia.

In the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Embodiment An embodiment in which the present invention is applied to a running hydraulic closed circuit of a wheel loader will be described with reference to FIGS. 1 and 2. FIG.

FIG. 1 shows a hydraulic closed circuit according to the present invention, and the same parts as in FIG. 4 are given the same reference numerals, and the explanation will focus on the differences.

In FIG. 1, the contacts 6a and 6b are connected to one input terminal 21a of a comparator 21 via a line Q, to which a capacitor 22 and a resistor 23 are connected in parallel. Also, the other input terminal 21b of the comparator 21
The reference voltage Vref from the reference power supply 24 is input to
The output terminal 21c of the comparator 21 is an NPN transistor 25.
connected to the base of.

Here, the reference voltage Vref is set lower than the voltage (2) of the power supply 7, and the comparator 21 is connected to the input terminal 2.
It is configured to output a high level signal from the output terminal 21c only when the potential of 1a is higher than the reference voltage V.sub.ref. Further, the collector of the transistor 25 is connected to the power source 7, and the emitter is connected to the solenoid section 5a of the neutral communication valve 5. Here, the comparator 2
1. Capacitor 22. Resistance 23. A reference power supply 24 and a transistor 25 constitute a switching control circuit 20 .

Next, the operation of the embodiment will be explained with reference also to time chart 1 in FIG.

The forward/reverse switching lever 4 is in the N position for a predetermined time (capacitor 2
2) When it is held,
The transistor 25 is off, the solenoid portion 5a of the neutral communication valve 5 is demagnetized, and the neutral communication valve 5 is in the illustrated position a (communication position), so that the main pipes 11 and 12 are in communication. Further, at this time, the tilt angle of the hydraulic pump 1 is zero, the hydraulic motor 2 is not driven, and the vehicle is stopped. When the forward/reverse switching lever 4 is switched from the N position to the F position, the pump regulator 3 controls the tilting direction of the variable displacement cedar hydraulic pump 1, and thereby the hydraulic pump 1
discharges pressure oil into the pipe line 11.

Note that the amount of tilting is made proportional to the engine speed by a mechanism not shown.

Here, FIG. 2 shows the comparator 2 when the operating lever 4 is switched.
1 is a time chart showing changes in the potential of the input terminal 21a of the neutral communication valve 5 and the potential of the solenoid portion 5a of the neutral communication valve 5, respectively. F position switching of forward/backward switching lever 4 (time T
1), the contact 4a contacts the contact 6b and the capacitor 22 is charged, so that the voltage at the input terminal 21a of the comparator 21 increases at time T1 as shown in FIG. 2(b).
At time T2, which is slightly delayed from the reference voltage Vref, the reference voltage Vref becomes higher than the reference voltage Vref inputted manually to the input terminal 21b. As a result, the comparator 21 outputs a high level signal to its output terminal 21c, and the transistor 25 is turned on. As the transistor 25 is turned on, the power supply voltage V is applied to the solenoid portion 5a of the neutral communication valve 5 at time T2 as shown in FIG. 11
°12 is cut off. Therefore, the hydraulic motor 2 is rotated by the pressure oil discharged into the main pipe 11, and the vehicle moves forward. Here, the time from time T1 to T2 is sufficiently short and does not affect the drive of the hydraulic motor 2.

When the forward/reverse switching lever 4 is thus switched from the N position to the F position, the neutral communication valve 5 is immediately switched to the blocking position. Further, when the lever 4 is switched from the N position to the R position, the neutral communication valve 5 is immediately switched to the cutoff position by a similar operation.

Next, the operation when the forward/reverse switching lever 4 is temporarily returned from the F position to the N position and then switched to the R position before the predetermined time X1 has elapsed will be described.

In this case, when the operating lever 4 is returned to the N position at time T3 in FIG. It is gradually discharged through 23. Therefore, the voltage at the input terminal 21a does not become zero immediately, but gradually decreases as the capacitor 22 discharges, as shown in FIG. 2(b). And that voltage is the reference voltage Vr
When the lever 4 is switched to the R position at time T4 before reaching ef, the contact 4a comes into contact with the contact 6a, so that the voltage at the input terminal 21a becomes the power supply voltage V again.

Between this time point T3 and T4 (time X), the input terminal 21
Since the voltage of a is maintained above the reference voltage V r e f , the comparator 21 continues to output a high level signal, and 1 to
Even when the transistor 25 is kept in the on state and the operating lever 4 is in the neutral position, the neutral communication valve 5 is kept in the b position.

Therefore, the vehicle does not coast, and no impact is generated on the vehicle. Then, by switching the lever 4 to the R position, the hydraulic pump 1 discharges pressure oil to the pipe line 12 side, the hydraulic motor 4 reverses, and the vehicle moves backward.

Thereafter, when the operating lever 4 is switched to the neutral position at time 1.5, the contact 4a separates from the contact 6a, and the voltage at the input terminal 21a gradually decreases due to the charge stored in the capacitor 22 as described above. Then, for a predetermined time Xi (Xi)
X), the voltage becomes the reference voltage V r e f
becomes lower (time T6), so that the comparator 21 outputs a low level signal. Therefore, the 1-transistor 25 is turned off and the power source 7 is cut off from the solenoid section 5a, so the solenoid section 5a is demagnetized and the neutral communication valve is turned off.
The main line 11.12 is then switched into position.

This allows the vehicle to coast in the same way as before.

Here, the predetermined time X1 during which the neutral communication valve 5 is held at the b position can be adjusted by changing the capacitance of the capacitor 22 and the size of the resistor 23, but is usually between 0.8 seconds and 1 second. Approximately .0 seconds is desirable.

In the configuration of the above embodiment, the forward/reverse switching lever 4 serves as an operating lever, and the switching control circuit 20 serves as switching control means.

Further, FIG. 3 shows another embodiment, in which only the connection relationship between the operating lever 4 and the neutral communication valve 51 is illustrated.

In FIG. 3, the neutral communication valve 51 of this embodiment is of a hydraulic pilot type, and is switched between position a (communication position) and position b (blocking position) by the pressure acting on its pilot port 51a. Pressure oil from a hydraulic source 52 is supplied to the pilot port 51a through an electromagnetic switching valve (hereinafter referred to as an electromagnetic valve) 53.
This solenoid valve 53 is switched between the "a" position, which communicates the pilot port 51a with the tank 57, and the "mouth" position, which communicates with the hydraulic power source 52. It is considered possible. A check valve 54 is provided in the pipeline connecting the solenoid valve 53 and the pylon 1 to the port 51a.
A diaphragm 55 and an accumulator 56 are provided in parallel. Further, the solenoid portion 53a of the electromagnetic valve 53 is connected to the contacts 6a and 6b.

When the forward/reverse switching lever 4 is held at the N position for a predetermined time (the time required for the accumulated pressure in the accumulator 56 to be discharged), one end of the lever is connected to the contacts 6a, 6.
B, and the electromagnetic button t53 is not switched to the "A" position. Therefore, the pressure of the pilot ports 1 to 51a is the tank pressure, and the neutral communication valve 5 is in the illustrated position a (communication position).

That is, the main conduits 11, 12 are in communication. When the forward/reverse switching lever 4 is switched from the N position to the F position, the contact 4a comes into contact with the contact 6b, the solenoid part 53a is energized, the solenoid valve 53 is switched to the "r" position, and discharge from the hydraulic source 52 is performed. Oil flows through the solenoid valve 53 to the pilot port 51
guided by a.

Therefore, the pilot port 51. The pressure acting on the main pipe 11.a becomes higher than the spring force of the spring 51b, and the neutral communication valve 51 is switched to the position b. ．． 12 is shut off, and the hydraulic motor 2 is rotated by the oil discharged from the hydraulic pump 1 guided to the main pipe 11, and the vehicle moves forward. Also, the hydraulic source 5
Pressure is accumulated in the accumulator 56 via the check valve 54 by the discharged oil of No. 2.

Next, if the forward/reverse switching lever 4 is returned from the F position to the N position and then switched to the N position before a predetermined period of time has elapsed, the solenoid valve 53 will close because the contact 4a separates from the contact 6b at the N position. The pilot port 5 ], a communicates with the tank 57. As a result, the pressure accumulated in the accumulator 56 is reduced to
5 to the tank 57, the pressure at the pilot port 51a also gradually decreases, and therefore the neutral communication valve 5 does not switch to the a position immediately. When the lever 4 is switched to the N position before the pressure of the pilot port 51a becomes equal to or less than the spring force of the spring 51b, the contact 4a contacts the contact 6a, and the discharge pressure of the hydraulic source 52 is applied to the port 51a of the electric rod 1. It operates again, and the neutral communication valve 51 maintains the b position.

Therefore, the vehicle does not coast at the neutral position, and no impact is generated on the vehicle.

Thereafter, when the lever 4 is switched to the N position, the contact 4a separates from the contact 6a, and the pressure stored in the accumulator 56 gradually returns to the tank 57 via the throttle 55, as described above, and the pressure in the pylon 1 to port 51a gradually decreases. After a predetermined period of time, when the pressure becomes less than the spring force of the springs 5], b, the neutral communication valve 51 is switched to the position a, and the main pipes 11 and 12 are communicated.

Here, the predetermined time period during which the neutral communication valve 5 is held at position b can be adjusted by changing the capacity of the accumulator 56 and the opening degree of the throttle 55.

Note that the configuration of the switching control mechanism is not limited to the above two examples,
For example, if a microcomputer is used and the operating lever 4 is
When switching from position or N position to N position, a timer is activated to start counting a predetermined time, and when timing ends, the neutral communication valve is switched, and before timing ends, it is switched to F position or N position. Even if the time measurement is stopped when the timer is switched to , the same effect can be obtained.

Further, although the above description has been made with reference to the running hydraulic closed circuit of a wheel loader, the present invention is not limited to this, and the present invention can also be applied to a hydraulic closed circuit of a forklift or other vehicle, for example, as long as it has a neutral communication valve. can be applied. Further, the present invention is not limited to a traveling circuit, and can be similarly applied to a hydraulic closed circuit for rotating an upper revolving structure of a working machine.

G0 Effects of the Invention According to the present invention, the neutral communication valve is switched and held in the communication position only when the operating lever (for example, the forward/reverse switching lever) is in the neutral position for a predetermined period of time or more. In wheel loaders and forklifts that frequently switch forward and backward, when the forward/reverse switching lever is suddenly switched from the reverse position to the forward position, the neutral communication valve remains in the cutoff position even if the vehicle passes through the neutral position. The vehicle will not coast and will not cause any impact to the vehicle.

Therefore, it is possible to significantly reduce spillage of cargo and discomfort to the driver.

Furthermore, if the forward/reverse switching lever is held in the neutral position for a predetermined period of time or longer, the neutral communication valve does not switch to the communication position, so the neutral communication valve does not lose its original role as described in the prior art.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a diagram showing a hydraulic closed circuit according to the present invention, and FIG. A time chart showing changes in the potential and the potential of the solenoid part of the neutral communication valve, FIG. 3 is a diagram showing the main parts of a hydraulic circuit according to another embodiment, and FIG. 4 is a conventional hydraulic circuit diagram. . 1: Hydraulic pump 2: Hydraulic motor 3: Pump regulator 4: Forward/forward switching lever 5, 51: Neutral communication valve 14.
1.2: Main pipeline 20: Switching control circuit 21: Comparator 22: Capacitor 23: Resistor 2
4: Reference power source 25: Transistor 52: Hydraulic power source 53: Solenoid valve 55: Throttle 56: Accumulator

Claims (1)

[Scope of Claims] A double tilting variable displacement hydraulic pump; a hydraulic motor connected to the hydraulic pump in a closed circuit via a pair of main pipes and driven by oil discharged from the hydraulic pump; an operating lever that can be switched to a forward rotation position for commanding forward rotation, a reverse rotation position for commanding reverse rotation, and a neutral position for commanding stop of the hydraulic motor, and when the operation lever is switched to the forward rotation position or the reverse rotation position; In the hydraulic closed circuit, the hydraulic closed circuit includes a neutral communication valve that is switched to a blocking position that blocks the pair of main pipelines, and a neutral communication valve that is switched to a communication position that communicates both pipelines when switched to the neutral position. 1. A hydraulic closed circuit having a neutral communication valve, comprising a switching control means for switching the neutral communication valve to the communication position only when the neutral communication valve is in the neutral position for a predetermined period of time or more.