JPH04191501A - Hydromechanical actuator for construction machinery - Google Patents

Abstract

PURPOSE:To suppress excessive oil and prevent it from circulating into a tank by forming a passage in a valve chamber arranged oppositely to a driving part of a pilot valve for introducing a negative load pressure of an actuator thereto, providing a first throttle on the passage, and providing a second throttle on a passage which communicates the valve chamber with the tank. CONSTITUTION:A passage 32 is formed in a valve chamber 30 arranged oppositely to a driving part of a pilot valve 6 for introducing a negative load pressure Pa of a hydraulic motor 2 thereto. A first throttle 20 is provided on the passage 31, while a second throttle 21 is provided on a passage which communicates the valve chamber 30 with a tank. When the pilot valve 6 is operated abruptly and pressure pulses are generated, displacement of the pilot valve 6 is restricted through applying of a large pressure to the valve chamber 30 of the pilot valve 6. An opening rate of a proportional seat valve 4 is restricted accordingly, and controlling is carried out so as to decrease an amount of oil to be supplied to the hydraulic motor. Generation of oscillations is thus suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic drive system for a construction machine having a large inertial body, such as a hydraulic excavator.

[Prior Art] FIG. 5 is a circuit diagram showing an example of this type of hydraulic drive device. This conventional example includes a hydraulic source, that is, a variable displacement hydraulic pump 3, an actuator, such as a hydraulic motor 2, which is driven by pressure oil supplied from the hydraulic pump 3 and operates an inertial body 1, and a hydraulic motor 2 from the hydraulic pump 3. The proportional seat valve 4 has a slit 5 on the circumferential side, and a pilot valve 6 controls the drive of the proportional seat valve 4. In addition, in this conventional example, the adjusting means 3 that keeps the differential pressure across the proportional seat valve 4 constant
It has A. Also, if an external force is applied to the driving part of the pilot valve 6 and it is moved against the force of the spring 9 to open it,
Pressure oil flows from the back pressure chamber of the proportional seat valve 4 to the opening of the pilot valve 6 via the conduit 7, and further this pressure oil flows downstream of the proportional seat valve 4 via the conduit 8. The proportional seat valve 4 opens by an amount proportional to the opening amount of the pilot valve 6. Accordingly, pressure oil from the hydraulic pump 3 is supplied to the hydraulic motor 2 via the proportional seat valve 4. Further, the upper and lower ends of the pilot valve 6 are connected by an oil passage 10, thereby maintaining hydraulic balance. As mentioned above, proportional seat valves 4 which are actuated in response to pilot valves 6 are known.

When the pilot valve 6 is suddenly operated in a hydraulic drive system having the above-mentioned inertial body 1, pressure pulsations occur due to the compressibility of oil, and the rotational speed of the hydraulic motor 2 accordingly causes a slight change. Repeated vibrations may occur. In order to suppress such vibrations, as shown in Figure 5,
A pipe line 11 connecting the pipe line connected to the hydraulic motor 2 to the tank and a pipe line 12 connecting the hydraulic motor 2 to the tank are provided, and a relief valve or the like is provided in these pipe lines 11 and 12 to reduce the circuit pressure. It is known that it leaks when it becomes large. For example, regarding this situation [hydraulic design] (
Publisher: Nikkan Kogyo Shimbun, Publication date: 1965, Volume 4, No. 8, P, 33-p) 38).

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, the vibration that occurs when the inertial body 1 is suddenly operated is suppressed by returning excess flow to the tank via a relief valve or the like. This causes energy loss corresponding to the surplus flow, which is not economical.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to suppress vibrations that occur during sudden operation of an inertial body without causing excess flow to flow back into the tank. The purpose of the present invention is to provide a driving device.

[Means for Solving the Problems] In order to achieve this object, the present invention provides a hydraulic source, an actuator that is driven by pressure oil supplied from the hydraulic source and operates an inertial body, and an actuator that operates from the hydraulic source. In a hydraulic drive system for construction machinery, which is equipped with a proportional seat valve that controls the flow rate of pressure oil supplied to the valve, and a pilot valve that controls the drive of the proportional seat valve, the valve is located on the opposite side from the drive section of the pilot valve. A passage is provided in the valve chamber for introducing the load pressure of the actuator, a first restriction is provided in the passage, and a second restriction is provided in the passage connecting the valve chamber and the tank. be.

[Function] Since the present invention has the above configuration, when the load pressure of the actuator increases due to sudden operation of the inertial body, the load pressure is opposed to the drive part of the pilot valve via the first throttle. is applied to a valve chamber located on the side, and the opening amount of this pilot valve is limited so that it becomes small according to the magnitude of the load pressure, and the opening amount of the proportional seat valve is accordingly limited so that it becomes small, The flow rate supplied to the actuator is limited to less. That is, the relationship between the load pressure introduced into the valve chamber and the flow rate characteristics can be made to depend on the ratio of the opening areas of the first throttle and the second throttle, which are provided so as to be continuous with the valve chamber, and these throttles By appropriately setting the ratio of the opening areas, it is possible to limit the flow rate supplied to the actuator, suppress pressure pulsations, and suppress vibrations caused by the pressure pulsations.

[Embodiment] Hereinafter, one embodiment of the hydraulic drive device for construction machinery of the present invention will be described based on the drawings.

□W FIG. 1 is a circuit diagram showing one embodiment of the present invention, and is drawn in correspondence with FIG. 5 described above. That is, this embodiment also includes a hydraulic power source, that is, a variable displacement hydraulic pump 3, similar to that shown in FIG. The valve 4, the pilot valve 6, the adjusting means 3A for keeping the differential pressure across the proportional seat valve 4 constant, the pipe line 7 that connects the back pressure chamber of the proportional seat valve 4 with the upstream side of the pilot valve 6, and the pilot valve 4. It includes a pipe line that connects the downstream side of the valve 6 and the downstream side of the proportional seat valve 4, and an oil passage 10 that connects the upper and lower ends of the pilot valve 6.

In particular, in this embodiment, the load pressure P of the hydraulic motor 2 is applied to the valve chamber 30 located on the opposite side from the driving part of the pilot valve 6.
In addition to providing a passage 31 for guiding the air, a first throttle 20 is provided in this passage 31, and a second throttle 21 is provided in a passage connecting the valve chamber 30 and the tank.

In this embodiment, since the opening amount of the proportional seat valve 4 is controlled according to the displacement of the pilot valve 6 due to the external force F, the hydraulic motor 2 is connected to the valve chamber 30 of the pilot valve 6 via the passage 31.
A driving pressure, that is, a load pressure Pa is introduced, and this load pressure Pa
When the displacement of the pilot valve 6 is reduced in accordance with the reduced displacement of the pilot valve 6, the amount of oil passing through the proportional seat valve 4 is also reduced in accordance with the reduced displacement of the pilot valve 6.

In addition, in addition to the configuration described above, based on the concept of applying load pressure Pa to the pilot valve 6 to reduce its displacement, a simpler configuration is adopted in which the lower end of the pilot valve 6 is stepped as shown in FIG. The step is determined by the area difference (d,
"-d2") ・If we consider whether it is possible to utilize π/4 to control the pilot valve 6, we will find the following.

Now, suppose d1=4 [mm], and the external force F is 20 [K
g/cm2] reaches its maximum value when a hydraulic pressure equivalent to
Assuming that the pilot valve 6 is fully stroked, Fmax=(π/4) X0142X20=2.51
[Kg]. Then, the load pressure Pa is 100 [Kg
/cm2], if the flow rate is intended to decrease to 90% of the no-load state, then 2,51X0.1=0.251 [Kg] is the load pressure Pa
It is a good thing if it occurs because of this.

That is, (π/4) X − (0,42Xd2”) X100=
0.251 [Kg], and from this, d2= 0.42-0.251/ (π/4) X1
00=0.396. Therefore, for d1=4 [mm], d
2 = 3.96 [mm], and the diameter difference is 40
[μ] becomes.

In reality, it is quite difficult to manufacture and manage this 40 [μ] step by taking into account the tolerances of dl and d2, and therefore, although such a step is simple in configuration, it is impractical. Become.

Taking this into consideration, in this embodiment, the first diaphragm 20 and the second diaphragm 21 are provided as described above, and the signal pressure between them is utilized, but the effect is as follows. That's right.

Now, the upstream pressure (load pressure) of the first throttle 20 is Pa, the downstream pressure (pressure inside the valve chamber 30) is Pc, and the pressure of the first throttle 20 is Pc.
'The opening area is al, the downstream pressure of the second throttle 21 is Pt,
If the opening area of the second diaphragm 21 is a2, the flow rate passing through the first diaphragm 20 and the second diaphragm 21 is q = C+
'at' FSaeA-Y Fh:People=c2Ha2m
There is a relationship of F77f■:■, and if the flow coefficient Cl #C2, then a, z
(Pa-Pc)=a2''(Pc-Pt)(at2
+a22) PC=a+2Pa+a22Pt holds true. If we calculate this for Pc, Pc=Pa/ (1+
(a2/a+) 2), +(a2/at)2・Pt/
(1+(a2/a+)2), (1).

Here, if the pressure receiving area of the pilot valve 6 is ap, then
It is sufficient if the force [a, .Pc -a, .Pt] becomes a force that opposes the external force F, for example, the aforementioned f, = 0.251 [Kg].

From the above equation (1), a, ・Pc −a, ・Pt = a, ・Pa/ (1+(a2/a+)2)+a, ・P
t [(az/a+)2/ (1+(a2/a+)2)
−1]=a, ・(Pa−Pt) /1+ (a2+
a+)2=f. Rearranging this formula further, 1- (1+(a2/a+)2) = f/a, ・
(Pa-Pt)1+(a2/a+)2=ap・(Pa
-Pt)/fa2/a+= a,・Pa -Pt
f-1(2)f=a, ・(Pa-Pt)/(1+(a
2/a+)2) (3). That is, the load pressure P
Instead of a itself, (Pa-Pt) acts on the pilot valve 6.

Substituting each of the above numerical values as pt=o in the above equation (2), a2/a+= (71:/4) Xo, 42Kari001
0.251-1=7.0. Moreover, when we substitute each of the above-mentioned numerical values into the above equation (2) with Pt=10, we get a2/a! -(77:/4) Xo, 42X(100-
10) 10.251-1=6.64. That is, f =0.251 [Kg], P
When a2/a1 is calculated under the condition of a=100 [Kg/cm2], it is 7°0 when pt=○ and 6.64 when Pt=10. In other words, the aperture area a1 of the first aperture 20 and the aperture area a2 of the second aperture 21 are adjusted so that a2/a is approximately 7.
The desired function described above can be obtained by setting the ratio of
0. Providing the second diaphragm 21 is easy.

In the embodiment configured in this way, the pilot valve 6
When a pressure pulsation occurs due to sudden operation of the valve, the large pressure acts on the valve chamber 30 of the pilot valve 6 as described above, which limits the displacement of the pilot valve 6, thereby reducing the opening amount of the proportional seat valve 4. As a result, the amount of oil supplied to the hydraulic motor 2 is controlled to be small, thereby suppressing the occurrence of vibrations and causing almost no energy loss, which is highly economical.

Also, the relationship between the load pressure Pa and the flow rate characteristics is
．． Since it can be made to depend on the ratio a2/a+ of the aperture area of the second diaphragm 21, desired characteristics can be easily changed by appropriately changing the ratio a2/a1.

3 and 4 are diagrams showing other examples of the first throttle, and the example shown in FIG. 3 has a first throttle 20A inside the pilot valve 6.
In the example shown in FIG. 4, the sliding clearance of the pilot valve 6 is set as the first throttle 20B, and these first throttles 20A and 120B provide a passage for introducing the load pressure Pa into the valve chamber 30. Also serves as. In addition to achieving the same effects as in the first embodiment described above, the first throttle provided in this manner can be realized without changing the structure of the conventional pilot valve 6, and is easier to manufacture. , production costs are low.

[Effects of the Invention] Since the hydraulic drive system for construction machinery of the present invention is configured as described above, vibrations generated when the inertial body is suddenly operated can be suppressed.
Surplus flow can be suppressed without being returned to the tank, reducing energy loss and being highly economical compared to conventional methods. Furthermore, since the relationship between the load pressure and the flow rate characteristics depends on the ratio of the opening areas of the first throttle and the second throttle, desired characteristics can be easily changed by appropriately changing this ratio. .

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the hydraulic drive system for construction machinery of the present invention, Fig. 2 is a diagram illustrating a technology considered as a preliminary stage of the present invention, and Figs. FIG. 5 is a circuit diagram showing an example of a conventional hydraulic drive device for construction machinery. 1... Inertia body, 2... Hydraulic motor (actuator), 3... Variable displacement hydraulic pump (hydraulic source), 3A...
- Adjustment means, 4... Proportional seat valve, 5... Slit, 6... Pilot valve, 7.8... Pipe line, 9...
Spring, 10...Oil passage, 11.12...Pipe line, 20
．． 20A120B...first throttle, 30...valve chamber,
31...Aisle. Figure 4

Claims (1)

[Claims] (1) A hydraulic source, an actuator that is driven by pressure oil supplied from the hydraulic source and operates an inertial body, a proportional seat valve that controls the flow rate of the pressure oil supplied from the hydraulic source to the actuator, and a proportional seat valve that controls the flow rate of the pressure oil supplied from the hydraulic source to the actuator. In a hydraulic and drive device for construction machinery that is equipped with a pilot valve that controls the drive of a seat valve, a passage is provided for guiding the load pressure of the actuator to a valve chamber located on the opposite side of the drive section of the pilot valve, and A hydraulic drive device for construction machinery, characterized in that a first throttle is provided in the passage, and a second throttle is provided in the passage communicating the valve chamber and the tank.