JPH0523389Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention is applicable to a hydraulic circuit for a traveling device such as a hydraulic excavator, as shown in FIG.

In FIG. 4, reference numeral 1 denotes a swash plate type hydraulic motor for driving a crawler such as a hydraulic excavator. The hydraulic motor 1 has a swash plate 2 controlled in two positions by a control cylinder 3 that controls the tilting position of the swash plate. When the swash plate 2 is controlled by the control cylinder 3 to one of these two positions (first position 2a), the output of the hydraulic motor 1 is set to a high speed, low torque, which is used for running on flat ground. becomes.
In addition, when the swash plate 2 is controlled by the control cylinder 3 in another position (second position 2b), the output of the hydraulic motor 1 is controlled at low speed and high torque, which is used for running uphill and at low speed during work. becomes. The control cylinder 3 that controls the tilt angle of the swash plate 2 into two positions is
The pilot valve 4 is connected to the tank T or the high pressure side of the supply/discharge circuits 5a, 5b to the hydraulic motor 1 via a high pressure selection valve 6 (formed by check valves 6a, 6b). When the control cylinder 3 is connected to the tank T, the swash plate 2 is in the second position 2b, and when the control cylinder 3 is connected to either the high pressure side of the supply/discharge circuits 5a, 5b, the swash plate 2 is in the second position 2b. This is the first position 2a. In addition, the brake valves 13a and 13b provided in the supply and discharge circuits 5a and 5b control the hydraulic pressure on the discharge side when the hydraulic motor 1 is pumped by an inertial load when the hydraulic motor 1 is stopped. 1 to apply a braking force.

The supply/discharge circuits 5a, 5b are connected to a main switching valve 9 via a counterbalance valve 7 and a swivel joint 8, and a hydraulic pump P is connected to the main switching valve 9. Further, the pilot valve 4 that controls the control cylinder 3 is a pilot operating valve 1.
0 via a swivel joint 8.

As can be seen from the above configuration, the traveling unit SU formed by the hydraulic motor 1, the counterbalance valve 7, the high pressure selection valve 6, and the brake valve 13,
The hydraulic pump P, the main switching valve 9, and the pilot operating valve 10 are provided on the crawler, and are provided on a driver's cab that is provided above the traveling device of the construction machine via a swivel base.

In the conventional technology having the above configuration, in order to drive the hydraulic motor 1 in the direction of arrow A at low speed and high torque, the pilot operating valve 10 is moved to the switching position 10.
a, and then operate the main switching valve 9 to the switching position 9b. Switch pilot operating valve 10 to position 10
When the control cylinder 3 is operated as shown in FIG.
, so that the swash plate 2 is controlled to the second position 2b shown by the solid line. Next, when the main switching valve 9 is operated from the neutral position 9a to the switching position 9b, the oil discharged from the pump P is transferred from the main circuit 11b to the hydraulic motor 1 via the switching position 7b of the counterbalance valve 7 and the supply/discharge circuit 5b. The hydraulic motor 1 is actuated in the direction of arrow A. The oil discharged from the hydraulic motor 1 is transferred to the supply/discharge circuit 5a and the switching position 7 of the counterbalance valve 7.
a. It is discharged from the main circuit 11a to the tank T via the main switching valve 9.

When the pilot operating valve 10 is operated to the switching position 10b while the hydraulic motor 1 is in operation, the discharge hydraulic pressure of the pump P acts on the pilot valve 4 via the pilot line 14, and the pilot valve 4 is moved to the switching position 4b. Therefore, the pressure oil from the supply/discharge circuit 5b flows into the pressure chamber 3a of the control cylinder 3 via the high pressure selection valve 6 and the pilot valve 4, and moves the swash plate 2 to the first position 2a shown by the broken line. . Therefore, the output of the hydraulic motor 1 is high speed and low torque. Note that the pilot operating valve 10 is set to the switching position 1.
When operated to 0a, the pressure chamber 3a of the control cylinder 3
pressure oil is discharged from the drain pipe 12 to the tank T, the swash plate 2 is moved to the second position 2b shown by the solid line.
becomes.

When the main switching valve 9 is returned to the neutral position 9a, both the main circuits 11a and 11b are connected to the tank, so the counterbalance valve 7 is switched to the neutral position 7a and the supply/discharge circuits 5a and 5b are cut off. . However, since the hydraulic motor 1 is driven in the direction of arrow A by the inertial force of the load, it sucks oil from the supply/discharge circuit 5b and discharges it to the supply/discharge circuit 5a. This supply/discharge circuit 5a
Since the pressure of the pressure oil discharged is controlled to the set value of the brake valve 13a, a braking force corresponding to the set value of the brake valve 13a acts on the hydraulic motor 1.

<Problems to be solved by the invention> As explained above, in the conventional technology, a main switching valve for supplying and discharging pressure oil to and from a hydraulic motor and a pilot operation valve for changing the output of the hydraulic motor are separately provided. Each had to be operated individually. Therefore, if the main switching valve is operated (erroneously) with the pilot operating valve being operated to the switching position 10b and the swash plate 2 being operated to the second position 2a shown by the broken line, the hydraulic motor 1 will , the engine is in a state where high-speed, low-torque output is obtained, so the torque at startup is insufficient and the engine stalls, or if the engine does not stall, the engine starts suddenly, which may be unexpected by the operator. It was dangerous.

<Means for solving the problems> The means of the present invention to solve the problems of the prior art described above is to move the discharge side of the hydraulic pump to the main switching valve, the swivel joint, and the main switching valve to the neutral position. At some point, the hydraulic motor is connected to the hydraulic motor via the supply and discharge circuit, and a closing valve that closes the supply and discharge circuit to the hydraulic motor is connected. A swash plate type hydraulic motor is used, and in a traveling hydraulic circuit in which a control cylinder of the swash plate type hydraulic motor is connected to the supply/discharge circuit via a pilot valve and a high pressure selection valve, the main switching valve is a hydraulic pilot operated type, An operating valve for supplying and discharging pilot pressure oil to the hydraulic pilot section of this main switching valve is provided in the driver's cab, a high pressure selection valve is provided at the output port of this operating valve, and the output side of this high pressure selection valve is connected to the swivel joint. The switching pressure of the pilot valve is set to be higher than the pressure at which switching of the main switching valve ends.

<Operation> The present invention having the above-mentioned means connects the pilot valve of the control cylinder to the high pressure side of the operating valve that operates the main switching valve, and the timing of switching is determined by the switching timing of the main switching valve. Since the pilot valve is switched after switching, there is no possibility of erroneous operation in the relationship between the switching operation of the output of the hydraulic motor and the operation of the main switching valve.

<Example> Hereinafter, FIG. 1 showing an example of the present invention will be described. Note that the same reference numerals are used for parts that are the same as those in the prior art.

In FIG. 1, reference numeral 1 denotes a swash plate type hydraulic motor having a swash plate 2 whose tilt angle is controlled by a control cylinder 3. As shown in FIG. 4 is a pilot valve provided between the supply/discharge circuits 5a and 5b, and has two switching positions 4a, 5b.
4b, an operating section 4c, and a return spring 4d. The setting of the hydraulic pressure for switching the pilot valve 4 from the switching position 4a to 4b is determined by the pressing force of the return spring 4d, and is set higher than the pressure at which switching of the main switching valve 20 ends. Furthermore, when the pilot valve 4 is in the switching position 4a, the pressure chamber 3a of the control cylinder 3 is connected to the drain pipe 12, so that the swash plate 2 of the hydraulic motor 1 is moved to the second position indicated by the solid line.
is controlled to position 2b. (At this time, the output of the hydraulic motor 1 is low rotation and high torque.)
When the pilot valve 4 is in the switching position 4b, either the high pressure side of the supply/discharge circuits 5a, 5b or the pilot hydraulic pressure acts on the pressure chamber 3a of the control cylinder 3, and the swash plate of the hydraulic motor 1 2 is controlled to the first position 2a shown by the broken line. (At this time,
The output of the hydraulic motor 1 is high speed and low torque. ) Reference numerals 13a and 13b are brake valves, and the brake valve 13a is used to prevent the hydraulic motor from being subjected to an inertial load when supply and discharge of pressure oil from the hydraulic pump is stopped while the hydraulic motor 1 is operating in the direction of arrow A. A brake force is applied to the hydraulic motor 1 by controlling the pressure of the pressure oil which is driven by the hydraulic motor 1, performs a pump action, sucks oil from the supply/discharge circuit 5b, and discharges it to the supply/discharge circuit 5a. This brake valve 13a has a pressure increase buffer section 13a2 and a pressure change section 13a1 of this pressure increase buffer section 13a2. This pressure changing part 13a
Reference numeral 1 is connected to the pilot line 14, and the boost buffer pressure is changed almost simultaneously with the pressure at which the pilot valve 4 starts switching.

The brake valve 13a having the above structure has the characteristics shown in characteristic curves a and b in FIG. 3b. In FIG. 3b, the characteristic shown by characteristic curve B is when the swash plate 2 of the hydraulic motor 1 is at the position indicated by the solid line 2b. At this time, since the hydraulic pressure acting on the pressure changing part 13a1 of the brake valve 13a is a low value, the pressure increase of the brake valve 13a is not changed, and at this time, the output of the hydraulic motor 1 is also low speed, It has high torque. Therefore, when the hydraulic motor 1 is driven by an inertial load when supplying and discharging pressure oil to the hydraulic motor 1 is stopped, a high oil pressure is generated because the tilting angle of the swash plate 2 is large. At this time, as shown in the characteristic curve B, the pressure increase buffer 13a2 is operated from the time t0 when the supply and discharge of pressure oil to the hydraulic motor 1 is stopped to the time t1, and the supply and discharge circuit 5b
The hydraulic pressure of the hydraulic motor 1 is controlled to P2, and the inertial force acting on the hydraulic motor 1 is absorbed during this time t2.

Thereafter, by maintaining the oil pressure of the supply/discharge circuit 5a at the value of Pmax, a parking brake is applied to the hydraulic motor 1. This is shown by characteristic curve A in FIG. 3b. The characteristics are when the swash plate 2 of the hydraulic motor 1 is at the position indicated by the broken line 2a. At this time, the brake valve 13a is changed to its pressure changing brake valve 13a1.
Since the hydraulic pressure acting on the brake valve 13a is high, the pressure increase of the brake valve 13a is changed, and at this time, the output of the hydraulic motor 1 is also high speed and low torque. Therefore, when the hydraulic motor 1 is driven by an inertial load when the pressure oil supply to the hydraulic motor 1 is stopped, the tilting angle of the swash plate 2 is kept small (the position of the swash plate 2 is (The position will be maintained even if the pilot pressure is lost due to throttling, etc.)
Low oil pressure occurs. At this time, the boost buffer section 13a
2, as shown in characteristic curve A, from time t0 when the supply and discharge of pressure oil to the hydraulic motor 1 is stopped to time t1.
At time t2, the hydraulic pressure of the supply/discharge circuit 5b is controlled to P2, and during this time t2, the inertial force acting on the hydraulic motor 1 is absorbed. After time t1, the oil pressure of the supply/discharge circuit 5a is maintained at the value of Pmax. As described above, the brake valve 13a is configured to change the pressure in the pressure boosting buffer according to the magnitude of the hydraulic pressure generated by the inertial force that acts when the hydraulic motor 1 is stopped. Note that the brake valve 13b is the brake valve 13b.
It has the same characteristics as a, and the characteristics shown in FIG. 3b. Therefore, when the hydraulic motor 1 rotates in the direction of arrow B, the hydraulic pressure of the supply/discharge circuit 5b is controlled.

20 is a main switching valve, which has a neutral position 20a, switching positions 20b, 20c, and a hydraulic pilot part 20d,
20e. The hydraulic pilot portions 20d and 20e of the main switching valve 20 include an operating valve 3.
0 output ports 30d and 30e. Further, a high pressure selection valve 25 to which the pilot line 14 is connected is provided between the output ports 30d and 30e. This pilot line 14 is connected to the pilot valve 4.
It is connected to the operating section 4c and pressure changing sections 13a1 and 13b1 of the brake valves 13a and 13b. The operation valve 30 has an input port 30a connected to a hydraulic pressure source, and output ports 30d and 30e.
A pressure reducing valve is provided between the two, and the neutral setting of this pressure reducing valve is controlled in accordance with the operating angle of the handle 30c. The relationship between the angle θ of the handle 30c of the operating valve 30 and the output oil pressure of the output ports 30d and 30e is as shown in FIG. 3a.
The main switching valve 20 is switched from the neutral position 20a when the handle 30c of the operating valve 30 is operated in the direction of arrow H by θ1 from the neutral position in FIG. position 20b
When the handle 30c reaches θ2 (position I in Fig. 1), the oil pressure at the output port 30d reaches PL, and with this oil pressure, the main switching valve 20 moves to the neutral position 20a.
to the switching position 20b. This hydraulic pressure PL is transmitted through the high pressure selection valve 25 and the pilot pipe 14.
The operation part 4c of the pilot valve 4 and the part valve 1 are connected via
It acts on both the pressure changing parts 13a1 and 13b1 of 3a and 13b, but both are set so that they do not operate unless the pressure PV is higher than the pressure PL.

Therefore, while the handle 30 of the operation valve 30 is operated from the neutral position to θ2, the main switching valve 20 is switched from the neutral position 20a to the switching position 20b according to the amount of operation. Main circuit 11a, 11b
is connected to the pump and tank, and the main circuit 11a is supplied with an amount of oil according to the operating angle of the handle 30c of the operating valve 30. When the main circuits 11a and 11b are connected to the pump and tank, the counterbalance valve 7 switches from the neutral position 7a to 7b, and connects the pilot circuit 16 of the mechanical brake 1a of the hydraulic motor 1 and the supply/discharge circuit 5b to the main circuit. 11b, and the supply/discharge circuit 5a is connected to the main circuit 11b. Therefore, the hydraulic motor 1 begins to rotate in the direction of the arrow A, and the speed thereof becomes a value corresponding to the operating angle of the handle 30c of the operating valve 30. Then, when the handle 30c is operated beyond θ2 to θ2',
Since the oil pressure at the output port 30d exceeds the value of PV and reaches PH, the pilot valve 4 switches to the switching position 4b, applies pressure oil to the pressure chamber 3a of the control cylinder 3, and increases the pressure of the brake valves 13a and 13b. Low buffer pressure (as shown in characteristic curve A in Figure 3b)
will be changed to Therefore, although the amount of oil supplied to the hydraulic motor 1 does not change, the angle of the swash plate 2 (angle with the output shaft) becomes close to 90°, so the output becomes high speed and low torque.

When the handle 30c of the operation valve 30 is suddenly returned to the neutral position from the position of the operation angle θ3 (the position shown in FIG. 1), the main switching valve 20 returns to the neutral position 20a, and the main circuits 11a and 11b are Connect to T. Therefore, the counterbalance valve 7 also returns to the neutral position 7a, shutting off the supply/discharge circuits 5a and 5b,
The pilot circuit 16 is connected to the tank T and the pilot valve 4 is switched to the switching position 4a.

Even if the oil in the pilot pipe 14 drops rapidly, the boosted buffer pressure of the brake valves 13a, 13b is designed to fall with a little delay after the control cylinder 3 of the swash plate 2 returns, and during this delay time In addition, it absorbs the inertial force acting on the hydraulic motor 1 and smoothly stops the hydraulic motor 1. Note that when the handle 30c of the operation valve 30 is slowly returned to the neutral position, the main valve 20 is also moved to the switching position 20b.
Since the hydraulic motor 1 slowly returns to the neutral position 20a, the hydraulic motor 1 is also gradually stopped.

Furthermore, when the handle 30c is suddenly stopped from the operating angle θ2 (position I in FIG. 1), the brake valves 13a and 13b operate as described above.
A hydraulic motor can be stopped without impact.

In the above-mentioned operation, according to this embodiment, pressure oil is supplied and discharged from the hydraulic motor 1 and the swash plate 2 is controlled by simply operating the operating handle 30 of the operating valve, so that no erroneous operation occurs. .

The above description has been made only regarding the running unit SU1, but the same applies to the running unit SU2, so the explanation thereof will be omitted.

Next, FIG. 2 showing a second embodiment of the present invention will be described. Regarding the control, only the differences from the first embodiment will be explained, and other explanations will be omitted.

The difference between the second embodiment and the first embodiment is that a closing valve 40 is used instead of the counterbalance valve 7 of the first embodiment.
, the main circuits 11a, 11b and the supply/discharge circuits 5a, 5b
By configuring the closing valve 40 to be operated by the operation valve 30, the brake valves 13a',
The boost buffer function of 13b' is omitted. By adjusting the switching speed of the closing valve 40, the supply/discharge circuits 5a, 5b and the main circuits 11a, 11b are controlled.
By narrowing the gap between the brake valves 13a and 13b', a pressure increase buffering function is performed and the flow rate passing through the brake valves 13a' and 13b' is reduced, thereby reducing the size of the brake valves 13a and 13b'.

In FIG. 2, the closing valve 40 includes an operating portion 40a.
, and switching positions 40b and 40c. The operating portion 40a is connected to a pilot conduit 14 connected to the operating valve 30 via a speed control valve 40d of the closing valve 40. This closing valve 40
The handle 30c of the operating valve 30 is attached to the operating section 40a.
is operated, and its output oil pressure is applied to pilot line 1.
4, from switching position 40c to 4
0d, and the handle 30c of the operating valve 30
When the pilot line 14 is connected to the tank by means of the operating valve 30, the switching position 40b is switched to the switching position 40b. At this time, due to the action of the speed control valve 40d, the switching is gradually performed, and the supply/discharge pipes 5a, 5b and the main circuit 11a,
This is to form a position 40e (not shown) that narrows the space between the two parts 11b. The circuit 45 is an anti-cavitation circuit connected to the tank T via the residual pressure valve 46. As mentioned above, when the closing valve 40 is in the throttle position 40e, the tank T is connected to the supply/discharge circuit 5a or 5b. This is to replenish oil from the T and prevent cavitation from occurring.

Note that the pilot pipe line 14 is connected to a high pressure selection valve 25.
It is connected to the output port 30e or 30d of the operation valve 30 through the swivel joint 8, and is connected to the travel unit SU1 via the swivel joint 8, and is connected to the operation section 4c of the pilot valve 4 and the pressure change section 1 of the brake valves 13a' and 13b'.
Connected to 3a' and 13b'. Further, a pilot circuit 16' that controls the negative brake 1a of the hydraulic motor 1 is connected to the main circuits 11a and 11b via a high pressure selection valve 16a, and as in the first embodiment, the pilot circuit 16' controls the negative brake 1a of the hydraulic motor 1. Main circuit 1 at startup
It is loosened by hydraulic pressure on the high pressure side of either 1a or 11b.

In the second embodiment having the above configuration, when the handle 30c of the operating brake 30 is operated by θ1 in the direction of arrow H, pressure oil of pressure Pmin is supplied to the output port 30d, as shown in FIG. 3a. Exhale.

This pressure oil causes the main switching valve 20 to begin switching from the neutral position 20a to the switching position 20b.
At this time, the closing valve 40 is switched from the switching position 40c to the switching position 40c.
0b to connect supply/discharge circuits 5a, 5b and main circuits 11a, 11b. Therefore, the hydraulic motor 1 operates in the direction of arrow A, and then the operating valve 3
When the operating angle of the 0 handle 30c is increased, the supply and discharge of pressure oil to and from the hydraulic motor 1 is increased accordingly, so that the speed of the hydraulic motor is increased. When the handle 30c of the operating valve 30 is further operated and its operating angle exceeds θ2', the oil pressure at the output port 30d becomes PH and exceeds the switching pressure PV of the pilot valve 4, so that the swash plate 2 of the hydraulic motor 1 However, control cylinder 3
is controlled to the first position 2a shown by the broken line. Therefore, the output of the hydraulic motor 1 is further increased in speed.

From the above operating state, the handle 3 of the operating valve 30
0c is suddenly returned to the neutral position, the main switching valve 20 switches to the neutral position 20a, and the main circuits 11a and 11b switch to the tank T via the residual pressure valve 46.
The pilot line 14 is also connected to the tank T via an operating valve 30. When the hydraulic pressure command from the pilot line 14 disappears, the closing valve 40
moves from the switching position 40b to the aperture position 40e. Although the supply of pressure oil from the pump is stopped, the hydraulic motor 1 is rotated in the direction of arrow A by inertia, sucks oil from the supply/discharge circuit 5a, and
Discharge to. The pressure oil in this supply/discharge circuit 5b is throttled at the throttle position 40e of the closing valve 40, and the pressure oil in the main circuit 11a is
is released. Therefore, the inertial force acting on the hydraulic motor 1 is absorbed at the throttle position 40e of the closing valve 40. However, the aperture position 40e is located at the main circuit 11a.
Since the pressure oil is maintained between the circuit 45 and the supply/discharge circuit 5b, pressure oil is supplied from the circuit 45 to the supply/discharge circuit 5b.

As described above, according to this embodiment, the closing valve 4
0 and absorbs the inertial load when the hydraulic motor 1 is stopped, so the capacity of the brake valves 13a' and 13b' can be reduced, and the increase/deceleration of the hydraulic motor 1 and the swash plate 2 can be reduced. Since all control is performed by the operating angle of the handle 30c of the operating valve 30, erroneous operations can be prevented as in the first embodiment.

<Effects of the invention> As explained above, according to the invention, the main switching valve that supplies and discharges pressure oil to the hydraulic motor is of a hydraulic pilot type, and the operating valve that operates this main switching valve is It is installed in the driver's cab, and the output side of this control valve is connected to the pilot valve of the control cylinder via a high-pressure selection valve, so it is possible to operate the main switching valve and the control cylinder that controls the swash plate of the hydraulic motor. and can be sequentially operated. For this reason, the hydraulic motor supplies the entire hydraulic displacement amount in a low speed, high torque state, and then switches the swash plate to a high speed, low torque position. Therefore,
This prevents erroneous operation (starting with the swash plate switched to the high-speed/low-torque position), and the speed of the hydraulic motor can be controlled with a single control valve handle. This has effects such as improved operability.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of the first embodiment of the present invention;
The figure is a circuit diagram of the second embodiment, FIG. 3a is a characteristic curve diagram of the operating valve, and FIG. 3b is a brake valve 13a,
13b, and FIG. 4 is a circuit diagram of the prior art. DESCRIPTION OF SYMBOLS 1... Hydraulic motor, 2... Swash plate, 3... Control cylinder, 4... Pilot valve, 4c... Control unit,
5a, 5b... Supply and exhaust circuit, 6... High pressure selection valve, 7
... Counter balance valve (closing valve), 8 ... Swivel joint, 9 ... Main switching valve, 11a, 11
b...Main circuit, 13a, 13b...Brake valve,
20... Main switching valve, 20a... Neutral position, 20
b, c...Switching position, 20d, e...Hydraulic pilot section, 30...Operation valve, 30c...Handle,
30d, e... Output port.

Claims (1)

[Scope of utility model registration request] The discharge side of the hydraulic pump is connected to the hydraulic motor via the main switching valve, a swivel joint, a closing valve that closes the supply/discharge circuit to the hydraulic motor when the main switching valve is in the neutral position, and the supply/discharge circuit. , this hydraulic motor is a swash plate type hydraulic motor having a configuration including a swash plate that controls the tilting angle with a control cylinder, and the control cylinder of this swash plate type hydraulic motor is connected to the supply and exhaust through a pilot valve and a high pressure selection valve. In the traveling hydraulic circuit connected to the circuit, the main switching valve is of the hydraulic pilot operated type, and an operating valve for supplying and discharging pilot pressure oil to the hydraulic pilot section of the main switching valve is provided in the driver's cab, and the output of this operating valve is A high pressure selection valve is provided at the port, and the output side of the high pressure selection valve is connected to the control section of the pilot valve of the control cylinder via the swivel joint, and the switching pressure of the pilot valve is applied to the main switching valve. A hydraulic circuit for traveling, characterized in that the pressure is set higher than the pressure at which switching ends.