JPS6311491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit that prioritizes turning of a hydraulic excavator.

Conventionally, the hydraulic circuit of a hydraulic excavator has generally been a double pump circuit in which the oil discharged from two hydraulic pumps is controlled by two main control valves. The hydraulic pump is used for speed, bucket, and arm 2nd speed, and the oil discharged from the other hydraulic pump is used for right travel, turning, arm 1st speed, and boom 2nd speed.

According to the conventional hydraulic circuit described above, during turning acceleration,
The pressure in the swing circuit is determined by the main relief valve connected to the hydraulic pump, and because the relief valve is set at a constant high pressure, the pressure increases rapidly when the swing accelerates, causing a shock in the swing structure. I was afraid.

In addition, during simultaneous operations such as swinging and pulling the arm (arm cylinder is extended), swinging and raising the boom, the oil discharged from the hydraulic pump is supplied to the swing circuit, and the excess oil is supplied to the downstream arm circuit or boom circuit. However, in this conventional circuit, the swing circuit, arm circuit, and boom circuit are simply connected in parallel, so when the above-mentioned simultaneous operations are performed,
The pressure in the swing circuit was affected by the downstream arm circuit or boom circuit, and when the pressure in the arm circuit or boom circuit was low, the pressure in the swing was also low, and depending on the work, the swing could not be performed smoothly. . In order to compensate for these shortcomings, conventionally, the operator controlled the amount of oil supplied to each circuit by controlling the opening degree of each directional control valve, and manipulated it to match the movements of both. However, this operation is extremely difficult, and it is extremely difficult to operate the machine according to the operator's expectations.

In view of the above points, the present invention alleviates the shock during swing acceleration and deceleration, and enables smooth swing acceleration and deceleration. The system enables work to be performed properly with priority given to turning without being affected by circuit pressure, and also prevents deflection during driving.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In FIG. 1, the hydraulic pump P ₁ includes a main relief valve 10 and directional control valves 11, 12 for left travel, for boom 1st speed, for bucket and for arm 2nd speed, as in the conventional circuit. Motor for left travel via control valve V ₁ with 13, 14
M ₁ , boom cylinder C ₁ , bucket cylinder C ₃ ,
Arm cylinder C ₂ is connected.

On the other hand, a swing motor M ₃ , a right travel motor M ₂ , an arm cylinder C ₂ , and a boom cylinder C ₁ are connected to the hydraulic pump P ₂ via a control valve V ₂ that is different from a conventional control valve.
That is, the control valve V ₂ includes a main relief valve 20 and directional control valves 21, 22, 2 for turning, right travel, arm 1st speed, and boom 2nd speed.
3 and 24, and a variable sequence valve 40.

The turning direction control valve 21 is a turning remote control valve 5.
0, and the remote control valve 5
0, the secondary pressure led out to the secondary side pipes 53 and 54 is controlled with respect to the primary side pressure introduced from the hydraulic source 52 according to the operating angle of the lever 51 in the direction of arrow A or B. A pair of variable pressure reducing valves (not shown)
The secondary pressure led out to the pipes 53 and 54 is guided to pilot chambers on both sides of the turning directional control valve 21 to switch the valve 21.

In addition, each direction control valve 12, 1 other than travel
Similarly to the turning direction control valve 22, the valves 3, 14, 23, and 24 can be switched by secondary pressure from respective remote control valves (not shown).

The variable sequence valve 40 has an external pilot type balanced piston type relief valve structure as shown in FIG. 2, for example. That is, in FIG. 2, 41 is the valve body, 42 is the balance piston, 42a is the pilot chamber on the back of the piston, 43 is the spring, 44 is the pilot valve seat, 4
5 is a pilot valve, 45a is a pilot chamber on the back side, 46 is a pilot adjustment spring, 47 is a push rod, 47a is a pilot chamber on the back side, 40a is an inlet port, 40b is an outlet port, and 40c is a set pressure control. 40d is an external pilot port, and 40e is a drain passage.

Inlet port 40a of this variable sequence valve 40
is the inlet side passage 31 of the turning directional control valve 21.
A parallel passage 32 branched from is connected to the outlet port 40b, and an unload passage 35 and parallel passages 34, 36, 37 of each directional control valve 22, 23, 24 on the downstream side of the swing are connected to the outlet port 40b via a passage 33. Then, the oil bleed off by the variable sequence valve 40 is transferred to each downstream direction control valve 22, 23, 24.
The pressure on the high pressure side of the secondary pressure led out to the secondary side pipes 53 and 54 of the remote control valve for turning 50 is set pressure controlled via the shuttle valve 55 and the pipe 56. By introducing the pilot port 40c into the pilot port 40c, the set pressure of the variable sequence valve 40 can be controlled.Furthermore, the pressure on the high pressure side of the pipes 61 and 62 on both sides of the swirl circuit can be controlled via the shuttle valve 63 and the passage 64. By introducing this into the external pilot port 40d, it is possible to prevent running deflection due to the external drain of the variable sequence valve 40.

Both side pipes of the swing motor _M3 and the pipes 61, 6
A brake valve including a counterbalance valve 65 and overload relief valves 66 and 67 is provided between the two.

In the above circuit, the secondary pressure of the remote control valve 50 is controlled according to the operating angle θ of the lever 51 in the A or B direction, and the set pressure of the variable sequence valve 40 is controlled by the secondary pressure of the remote control valve 50. The set pressure of the variable sequence valve 40 is always lower than the set pressure of the overload relief valves 66 and 67, and the maximum set pressure of the variable sequence valve 40 is lower than the set pressure of the main relief valve 20. controlled to be small.

More specifically, the set pressure of the main relief valve 20 is 250 Kg/cm ² , the set pressure of the overload relief valves 66 and 67 is 220 Kg/cm ² , and the secondary pressure of the remote control valve 50 is set to A of the lever 51 or 4 as shown in Figure 3 depending on the operating angle in the B direction.
This remote control valve can be controlled in the range of ~30Kg/ ^cm2 .
The set pressure of the variable sequence valve 40 is controlled in the range of 0 to 210 Kg/cm ² as shown in FIG. 4 in accordance with the secondary pressure.

Next, the operation of the above circuit will be explained.

First, when the lever 51 of the remote control valve 50 for swinging is tilted in the direction of arrow A, pressure is generated in the secondary pipe line 53 of the remote control valve 50, and this secondary pressure is guided in the direction of arrow _A1 , and the direction for swinging is The control valve 21 is switched to the upper position, and the discharge oil of the hydraulic pump P ₂ is guided in the direction of the arrow A ₂ , forming a passage that flows into the swing motor M ₃ via the counterbalance valve 65.
The secondary pressure of the remote control valve 50 is also guided in _{the three} directions of arrow A via the shuttle valve 55, and is then introduced into the variable sequence valve 4.
The set pressure of 0 increases, and the hydraulic pump
The discharge pressure of _P2 increases, and this pressure accelerates the rotation.

In this case, the secondary pressure of the remote control valve 50 is controlled according to the operating angle of the lever 51 in the direction of arrow A, and the set pressure of the variable sequence valve 40 is controlled by this secondary pressure, and furthermore, the set pressure of the variable sequence valve 40 is controlled by this secondary pressure. The discharge pressure of the hydraulic pump _P2 is controlled by.
Therefore, when the operating angle of the lever 51 in the direction of arrow A is small, the discharge pressure of the hydraulic pump P ₂ becomes low, and the rotation is accelerated with the low pressure, and when the operating angle is increased, the discharge pressure of the hydraulic pump P ₂ becomes low. becomes high pressure,
Turning can be accelerated with high pressure, and by gradually increasing the operating angle from neutral, turning can be gradually accelerated, resulting in smooth acceleration with less shock, and turning can be accelerated by operating the lever 51. Torque control can be performed at the time.

By the way, during the turning acceleration mentioned above, the lever 5
1, the secondary pressure of the remote control valve 50 goes out of the control range and becomes the same as the primary pressure _P a a little before the maximum value θmax of the operating angle θ. This is remote control valve 5
This is to eliminate the amount of drain at the end of the lever stroke. However, the secondary pressure, that is, the primary pressure P _a at this time is influenced by the engine speed and fluctuates.

Therefore, if a direct-acting sequence valve is used and its set pressure is controlled by the secondary pressure of the remote control valve 50, the control characteristics shown in FIG. 6 will be shown, and the maximum value of the lever operation angle will be Due to the unstable secondary pressure of the remote control valve derived nearby, the maximum value of the set pressure of this sequence valve also becomes unstable, and the maximum pressure during turning acceleration also becomes unstable, making accurate control impossible.

However, in the present invention, a balanced piston type relief valve structure is used for the variable sequence 40,
As shown in FIG. 4, when the secondary pressure of the remote control valve 50 exceeds 30 kg/cm ² , the set pressure of the variable sequence valve 40 is not affected by the secondary pressure, and the maximum value of the set pressure is is specified to 210 kg/cm ² , so that the set pressure of the variable sequence valve 40 can be accurately controlled, that is, the pressure during turning acceleration can be controlled accurately. In addition, the maximum value of the set pressure of the variable sequence valve 40 in this case is determined by the maximum stroke l of the pilot adjustment spring 46 as shown in FIG.
This can be easily determined by adjusting the stroke regulated by the stopper of the push rod 47.

Next, during the swing acceleration, out of the oil discharged from the hydraulic pump P ₂ , the flow rate of oil corresponding to the rotational speed of the swing motor M ₃ flows preferentially into the swing motor M _{3, and the excess oil flows into the swing motor M 3} with priority. Bleed-off is performed at the set pressure by the variable sequence valve 40, and the passage 33
It flows into the parallel passages 34, 36, 37 and the unload passage 35 through the passageway.

At this time, if the downstream directional control valve 23 for arm 1 speed, for example, is switched to the upper position, the excess oil bleed off by the valve 40 is guided in the direction of arrow _A4 and flows into the arm cylinder _C2 , It can be used to push the arm, and the oil discharged from the hydraulic pump _P2 can be used effectively, eliminating energy loss. Furthermore, in this case, the variable sequence valve 40
Due to the presence of the hydraulic pump _P2 , the oil discharged from the hydraulic pump P2 is not affected by the pressure in the downstream arm circuit, and preferentially flows into the swing circuit at a pressure corresponding to the set pressure of the variable sequence valve 40, thereby properly accelerating the swing. This makes it possible to efficiently perform rotational acceleration and arm pulling simultaneously.

Also, when simultaneously accelerating the swing and raising the boom,
Even if the boom 2nd speed directional control valve 24 is operated, the variable sequence valve 40 causes the discharge oil of the hydraulic pump P ₂ to preferentially flow into the swing circuit, as in the case of simultaneous swing acceleration and arm pull. , and the surplus oil bled off by the valve 40 flows into the boom circuit, allowing the oil discharged from the pump P ₂ to be used effectively, and making the swing circuit independent without being affected by the boom circuit pressure. Thus, the rotation can be accelerated at a pressure corresponding to the set pressure of the valve 40.

Note that during the above-mentioned turning acceleration, if downstream right travel, arm 1st speed, and boom 2nd speed are not used, the excess oil bleed off by the variable sequence valve 40 will flow from the passage 33 to the unloading passage 35 to the tank T. It is circulated to.

Next, when stopping the swing, the secondary pressure becomes 0 by returning the lever 51 to the neutral position, the swing direction control valve 21 is returned to the neutral position, and the swing motor M is switched from the hydraulic pump _P2 to the swing motor M. The supply of pressure oil to _{M 3} is stopped, and the swing motor M ₃ is braked by the counter balance valve 65 and the overload relief valve 66.

Next, if the lever 51 is held in the neutral position, the secondary pressure of the remote control valve 50 is 0, the swing direction control valve 21 is in the neutral position, and the set pressure of the variable sequence valve 40 is 0. . Therefore, the oil discharged from the hydraulic pump _P2 does not flow into the swing circuit, but flows into the variable sequence valve 40, and the entire amount is bled off and flows into the passage 33 or 35, so that the oil discharged from the hydraulic pump P2 does not flow into the swing circuit, but flows into the variable sequence valve 40.
Arm 1st speed and boom 2nd speed can be used in the same way as the conventional circuit. Moreover, in this case, the variable sequence valve 40
Since an externally piloted balance piston type is used for this purpose, there is no risk of running deflection.

That is, if the pilot port 40d of the variable sequence valve 40 is an internal pilot type in which pilot pressure is introduced from the inlet side, that is, the passage 32 on the pump side, an external drain will always occur when the pump pressure increases. Especially when driving, for example, the circuit flow rate is 100/min and the external drain is 1/min.
/min, the running flow rate on the side where the sequence valve is located is 99/min, and the running flow rate on the other side is 100/min.
/min, resulting in an additional 1% travel deflection and poor straight-line performance.

However, in the present invention, the variable sequence valve 4
Since the pilot port 40d of 0 is an external pilot type in which the pressure on the high pressure side of the pipes 61 and 62 on both sides of the swirl circuit is selected and introduced by the shuttle valve 63, the external drain is used when the swirl is not in use. It is small and is not affected by the pump pressure, so running deflection can be prevented.

FIG. 5 shows another embodiment of the present invention,
Overload relief valve 66' with variable set pressure;
67', the secondary pressure of the remote control valve for rotation 50 is connected to the pilot ports 66'a, 67'a for controlling the set pressure of the valves 66', 67' through the pipes 53, 5.
4 through pipes 57 and 58, and the variable sequence valve 4
At the same time as controlling the set pressure of 0, the set pressures of the overload relief valves 66' and 67' are also controlled. However, in this case, as the secondary pressure of the remote control valve 50 is controlled in the range of 0 to 30 kg/cm ² , the set pressure of the variable sequence valve 40 is controlled in direct proportion in the range of 0 to 210 kg/cm ² . On the other hand, overload relief valves 66', 6
The set pressure of 7' is controlled inversely proportionally within the range of 220 to 30 kg/cm ² .

According to this embodiment, the set pressure of the overload relief valves 66', 67' is controlled to be a low pressure (minimum 30 kg/cm ² ) when the swing is accelerated, and when the swing is decelerated, the set pressure of the overload relief valves 66', 67' is controlled to be low pressure. The set pressure is controlled to be high, and at this pressure the swing motor _M3
will apply the brakes. In addition, the valve 6
The set pressure of 6' and 67', that is, the brake pressure, is
Since it is controlled by the secondary pressure, the lever 5
1 to the neutral position and gradually reduce the secondary pressure, the turning can be gradually decelerated, and the turning can be smoothly decelerated with less shock. Torque control can also be performed.

In the above example, the main control valve
Although the directional control valves 21, 22, and 23 in _V2 are parallel circuits, and the turning is set to the most upstream side, a tandem circuit is used for running, and the other circuits are parallel circuits.

Further, in the above embodiment, a two-pump type hydraulic circuit has been described, but it goes without saying that the present invention can also be applied to a three-pump type hydraulic circuit.

As explained above, according to the present invention, when the swing and the arm and boom are simultaneously worked, the swing circuit can be prioritized over the arm circuit and the boom circuit, so that the swing can always be performed properly, and the above simultaneous operations can be performed properly. Able to work efficiently. In addition, torque can be freely controlled during corner acceleration, reducing shock and allowing smooth acceleration. In particular, since an external pilot balanced piston type variable sequence valve is used, the maximum value of the set pressure of this variable sequence valve, that is, the maximum value of the swirling pressure, can be easily stabilized.
The above-mentioned turning control can always be performed appropriately. Furthermore, running deflection can be prevented and straight-line performance can be improved.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of an external pilot type balanced piston type variable sequence valve, Fig. 3 is a control characteristic diagram of a remote control valve for swinging, and Fig. 3 is a diagram showing control characteristics of a remote control valve for swinging. Fig. 4 is a control characteristic diagram of the variable sequence valve, Fig. 5 is a hydraulic circuit diagram of the main part showing another embodiment of the present invention, and Fig. 6 is a control characteristic when a direct acting type variable sequence valve is used. It is a diagram. P ₁ , P ₂ ... Hydraulic pump, M ₁ , M ₂ ... Travel motor, M ₃ ... Swing motor, C ₁ ... Boom cylinder,
C ₂ ... Arm cylinder, C ₃ ... Bucket cylinder, T ... Oil tank, 10 ... Main relief valve, 11 ... Directional control valve for left running, 12 ... Directional control valve for boom 1st speed, 13 ... Directional control valve for bucket, 14 ... Directional control valve for arm 2nd speed, 20...
... Main relief valve, 21 ... Directional control valve for swinging, 22 ... Directional control valve for right travel, 23 ... Directional control valve for arm 1st speed, 24 ... Directional control valve for boom 2nd speed, 31 ... Input Side passage, 32, 34, 3
6, 37...Parallel passage, 33...Bleed-off passage, 35...Unload passage, 40...External pilot type balanced piston type variable sequence valve, 40a...Inlet side port, 40b...Outlet side port, 40c...Pilot port for controlling set pressure, 40d...External pilot port, 42
... Balance piston, 45 ... Pilot valve,
47...Push rod, 50...Swivel remote control valve, 51...Lever, 52...Hydraulic power source, 53,
54... Secondary pipe line, 55... Shuttle valve, 56
...Pipe line, 61, 62...Pipe line on both sides of the turning circuit,
63... Shuttle valve, 65... Counter balance valve, 66, 67, 66', 67'... Overload relief valve.

Claims (1)

[Claims] 1. In the hydraulic circuit of a hydraulic excavator, a variable sequence valve consisting of an external pilot-type balance piston type relief valve is connected to a parallel passage branched from the input side passage of a swing direction control valve connected to a hydraulic pump, and the variable sequence valve is The oil bleed off by the valve is configured to be guided to the directional control valve for the actuator such as the boom cylinder or arm cylinder provided downstream of the swing, and on the other hand, the secondary pressure of the remote control valve for the swing that switches the directional control valve for the swing is The pressure on the high pressure side is guided through a shuttle valve to a pilot port on the back of the push rod of the variable sequence valve to control the set pressure of the variable sequence valve, and the pressure on the high pressure side of the pipes on both sides of the swirl circuit is 1. A hydraulic circuit for a hydraulic excavator, characterized in that the hydraulic circuit is configured to guide side pressure to an external pilot port on the back surface of a balance piston of the variable sequence valve through a shuttle valve.