JP2892734B2 - Hydraulic drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic drive device provided in a hydraulic machine such as a hydraulic shovel, a crane, etc., for controlling the drive of an actuator.

[Conventional technology]

FIG. 3 is a diagram showing a conventional hydraulic circuit including a pressure compensating valve, and is a variable displacement hydraulic pump 9 (hereinafter referred to as a hydraulic pump).
Further, actuators 10 and 20 for driving a load (not shown) by the hydraulic oil discharged from the hydraulic pump 9 are connected to the hydraulic pump 9. Further, a regulator 13 for changing the displacement of the hydraulic pump 9 is provided.

Further, the discharge pressure P ₁ of the hydraulic pump 9 is pressure compensating valve 12, 22
The pressure compensating valves 12 and 22 have directional control valves 11 and
The pressure compensating valves 12 and 22 control the pressure difference between upstream and downstream of the direction switching valves 11 and 21, which is the pressure difference between upstream and downstream.

FIG. 4 is a sectional view of the above-mentioned conventional pressure compensating valve. The pressure compensating valves 12 and 22 are connected to the spool chamber 3a of the sleeve 1 and the spool chamber 3a.
27 are formed, and the spool 3 is slidably accommodated in the spool chamber 3a. A wide-diameter spring receiving portion 4 is integrally formed at the end of the spool 3, and the spring receiving portion 4 is slidably disposed in the pressure chamber 27.
A spring 2 is provided between the end faces of the spring.

The spool chamber 3a inlet port 7 and outlet port 8 is formed, the discharge pressure P ₁ of the hydraulic pump 9 is directed to the inlet port 7, an outlet port 8 is connected to the upstream side of the directional control valve 11, 21 (upstream pressure of the directional control valve 11, 21 is P _2, P ₂ ').

The pressure chamber 27 is connected to the downstream side of the directional control valves 11 and 21 (the downstream pressures of the directional control valves 11 and 21 are P ₃ and P ₃ ′).
Actuator 1 is connected downstream of check valves 16 and 26 via check valves 16 and 26.
Connected to 0,20.

In addition, the load pressure is guided to the downstream side of the direction switching valves 11 and 21,
The load pressure is further led to a regulator 13.

The operation of the conventional hydraulic circuit having such a configuration will be described focusing on the operation of the actuator 10.

By operating the directional control valve 11, the actuator
10 is driven. Then, the load pressure of the load driven by the actuator 10 is guided to the regulator 13 through the pilot circuit 14, and the discharge pressure P ₁ of the hydraulic pump 9 is maintained such that the difference from the self-pressure of the hydraulic pump 9 is kept constant. Changes.

Here, the combined operation in the hydraulic circuit, ie, the directional control valve
A case in which 11, 21 are operated simultaneously will be described.

FIG. 2 is a flow characteristic diagram of the pressure compensating valve, in which I is a flow characteristic curve of the pressure compensating valve 12, and II is a flow characteristic curve of the pressure compensating valve 22. The discharge pressure P ₁ of the slave connexion hydraulic pump 9 is increased to the load pressure rises. When the discharge pressure P ₁ of the hydraulic pump 9 is P _S2, if the pressure compensating valve 12 is not temporarily provided with a pressure compensation function should flow supply is performed in Lee point of the second view.

However, even if an attempt is made to supply the flow rate at the point a, the discharge flow rate of the hydraulic pump 9 is actually restricted to a predetermined flow rate.
Side, the oil does not flow to the high load side, and the actuator 10 cannot be operated.

Therefore, as shown in FIG. 3, pressure compensating valves 12 and 22 having a pressure compensating function are mounted. In this way, the spools 3 of the pressure compensating valves 12 and 22 are displaced so that the differential pressure between the upstream side and the downstream side of the directional control valves 11 and 21 is kept constant, and the fluctuations of other load pressures are mutually changed. A constant flow rate is passed through the respective pressure compensating valves 12 and 22 without being affected, and the flow rate characteristics as shown in FIG. 2C are obtained.

[Problems to be solved by the invention]

In a hydraulic circuit equipped with the above-described conventional pressure compensating valve, for example, when driving a working machine of a hydraulic shovel as a load, when trying to raise the boom while giving a predetermined swing,
The ascending speed may be abnormally reduced.

Explaining with reference to FIG. 2, if I indicates the flow characteristic of the boom rise and II indicates the flow characteristic of the turning in the same figure, if the flow constant characteristic is as shown in FIG. The flow rate for a certain boom raising operation cannot be increased, and the driving speed of the actuator for driving the boom cannot be increased.

Further, depending on the shape of the spool or the like of the pressure compensating valve, there may be a case where a constant flow characteristic cannot be ensured because the rightward downward characteristic shown in FIG. To cope with these, it is conceivable to change the shape of the spool or the sleeve, but this changing operation is generally not easy.

The present invention has been made in view of the current situation of such a hydraulic drive device as described above, and has an object to change the flow rate in proportion to the increase in the discharge pressure of the hydraulic pump without changing the shape of the spool or the sleeve. It is another object of the present invention to provide a hydraulic drive device capable of obtaining an upper right characteristic that increases as a result.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a hydraulic source, a hydraulic actuator driven by hydraulic oil discharged from the hydraulic source, and a flow of hydraulic oil supplied from the hydraulic source to the hydraulic actuator. A directional control valve to be controlled, one end of which is disposed in a pressure chamber provided with a spring, one end of which is provided with a downstream pressure of the directional control valve, and the other end of which is provided with an upstream pressure of the directional control valve. A spool provided, and a variable throttle interposed between an inlet port communicating with the hydraulic pressure source and an outlet port communicating with the upstream side of the direction switching valve, and the upstream side and the downstream side of the direction switching valve. A pressure compensating valve for controlling the pressure difference before and after the pressure difference,
In the hydraulic drive device for controlling the drive speed of the actuator, a fixed throttle for connecting the inlet port and the outlet port is provided on a spool of the pressure compensating valve.

[Action]

According to the present invention, in addition to the variable throttle, the spool of the pressure compensating valve is provided with a fixed throttle that connects the inlet port communicating with the hydraulic pressure source and the outlet port communicating with the upstream side of the direction switching valve. If the differential pressure before and after the compensating valve increases compared to when there is no fixed throttle, control can be performed with the flow rate to the corresponding actuator increased, and therefore, if the pressure compensating valve is arranged on the high load side, In addition, it is possible to stably drive the high-load side at a sufficient driving speed during the combined operation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a pressure compensating valve according to an embodiment, and the same parts as those in FIG.

As shown in the figure, in the embodiment, as in the conventional case, the pressure chamber 27 and the spool chamber 3a formed in the sleeve 1
A spool 3 having an end integrally formed with a spring receiving portion 4 is slidably accommodated.

As in the prior art, the spring 2 is provided between the spring receiving portion 4 and the end face of the pressure chamber 27, and the inlet port 7 is formed on the peripheral surface of the sleeve 1.

In the embodiment, a fixed throttle 6 having an opening area az is formed in the spool 3, and an outlet port 8 is provided at an end of the spool 3. Further, a variable throttle 5 formed on the spool 3 sets a throttle amount according to the position of the spool 3. That is, the spool 3 of the pressure compensating valve has, in addition to the variable throttle 5 that connects the inlet port 7 communicating with the hydraulic pump 9 and the outlet port 8 communicating with the upstream side of the direction switching valve 11, the inlet port 7 A fixed throttle 6 is provided to connect the outlet port 8 with the fixed throttle 6.

In the embodiment, the pressure compensating valve having such a structure is used as the pressure compensating valve on the high load side (the pressure compensating valve 12 in FIG. 3).

Actuator 10,20, check valve 16,26, directional control valve 11,2
1. The hydraulic pump 9 and the check valves 15 and 25 are the same as those of the conventional hydraulic drive shown in FIG. 3, and their mutual connection and connection of the pressure compensating valve to them have already been described. This is performed in the same manner as in FIG.

In the pressure compensating valve shown in FIG. ₁ , the flow rate flowing from the inlet port 7 through the fixed throttle 6 and the variable throttle 5 is W ₁ , the flow rate flowing through the directional control valve 11 is Q ₂ , the flow coefficient is C, and the spool is 3 yen. The peripheral wall width is W _X , the amount of contraction of the spring 2 is xs, the amount of movement of the spool 3 is x, the opening area of the fixed throttle 6 is az, the opening area of the directional control valve 11 is A _P , the spring constant of the spring 2 is K, The pressure receiving area at the outlet port 8 of the spool 3 is A _X , the acceleration of gravity is g, the specific weight is γ, the oil inflow angle into the variable throttle 5 is θ, the hydraulic pump 9
The discharge pressure of P ₁ , the upstream pressure of the directional control valve 11 to P ₂ , and the directional control valve
The downstream pressure of 11 as P _3, the following equation is established.

K (xs−x) = Ax (P ₂ −P ₃ ) + 2C · W _X · x (P ₁ −P ₂ ) co
sθ (3) By rewriting the equations (1) to (3) in consideration of the relationship of Q ₁ = Q ₂ , the following equation is obtained.

In the equation (4), when the fixed stop 6 is not provided on the spool 3, az = 0, and therefore the equation (4) is as follows.

From equations (4) and (5), it is apparent that P ₂ −P ₃ > P ₂ ′ −P ₃ ′
Therefore, by providing the fixed throttle 6, the direction switching valve
The flow rate of 11 has increased.

With the hydraulic drive device of such an embodiment, the actuator
10, for example, the lifting drive of the boom on the high load side is performed,
When the actuator 20 is used to drive the boom on the low load side to rotate, the flow characteristic of the pressure compensating valve 12 provided with the fixed throttle 6 has an upper right characteristic as shown in FIG.

As a result, the load pressure increases, and the hydraulic pump 9
Discharge the pressure P ₁ increases, the discharge pressure P ₁ switching valve 11 in proportion to the
, The boom can be driven upward without lowering the lifting speed.

Thus, according to the embodiment, the above-described compensation term obtained by providing the fixed stop 6 Accordingly, the same effect can be obtained by overcompensating the fluid force in the compensation region, the flow rate passing through the directional control valve 11 is increased, and the damping capacity without hunting is enhanced,
It is possible to control the load accurately and stably.

Just by providing the fixed throttle 6 on the spool 3, the sleeve 1
There is no need to change the shape of the spool 3 and the hydraulic drive device that can easily increase the flow rate on the high load side and perform the load control with high accuracy at low manufacturing cost.

〔The invention's effect〕

As described in detail above, according to the present invention, in addition to the variable throttle normally provided on the spool of the pressure compensating valve, the inlet port communicating with the hydraulic pressure source and the outlet port communicating with the upstream side of the direction switching valve are provided. With a simple configuration that only requires a fixed throttle to be connected, a right-upper characteristic in which the flow rate increases in proportion to the increase in the discharge pressure of the hydraulic power source is obtained.Therefore, this pressure compensating valve is provided on the high load side. For example, it is possible to increase the flow rate on the high load side as compared with the conventional case, and to control stably with high accuracy without lowering the speed of the actuator on the high load side.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a pressure compensating valve according to an embodiment of the present invention, FIG. 2 is a flow characteristic diagram of the pressure compensating valve, FIG. 3 is a diagram showing a hydraulic circuit including a conventional pressure compensating valve, FIG. 4 is a sectional view showing the structure of a conventional pressure compensating valve. 1 ... sleeve, 2 ... spring, 3 ... spool, 3a ...
Spool chamber, 4 ... Spring receiving part, 5 ... Variable throttle, 6 ...
... fixed throttle, 7 ... inlet port, 8 ... outlet port, 9
…… Hydraulic pump, 10,20 …… Actuator, 11, 21…
… Directional switching valve, 12,22… Pressure compensating valve, 13 …… Regulator, 14 …… Pilot circuit, 15,25 …… Check valve, 16,26
……Check valve.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-321201 (JP, A) JP-A-63-47503 (JP, A) JP-A-54-160976 (JP, A) JP-A-58-58 54206 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F15B 11/00-11/22

Claims (1)

(57) [Claims] 1. A hydraulic source, a hydraulic actuator driven by hydraulic oil discharged from the hydraulic source, and a direction switching valve for controlling a flow of hydraulic oil supplied from the hydraulic source to the hydraulic actuator. A spool having one end arranged in a pressure chamber provided with a spring, one end of which is provided with a downstream pressure of the directional control valve, and the other end of which is provided with an upstream pressure of the directional control valve, and A variable throttle interposed between an inlet port communicating with the hydraulic pressure source and an outlet port communicating with the upstream side of the direction switching valve, and a differential pressure between upstream and downstream of the direction switching valve; A pressure compensating valve for controlling a differential pressure, wherein the hydraulic drive device controls a driving speed of the actuator, wherein a fixed throttle for connecting the inlet port and the outlet port to a spool of the pressure compensating valve. Hydraulic drive system is characterized by providing.