CN1011733B - Flow controlling valve with pressure compensation - Google Patents

Abstract

The invention relates to a flow control valve with pressure compensation function. It is characterized in that the valve is provided with two hydraulic chambers and an orifice connecting the two hydraulic chambers; when the pressure oil flows in from the first through hole (35a), a pressure difference is generated between the two hydraulic chambers, and the slide valve moves to the left. The opening and closing opening (44a) is opened, so that the first through hole communicates with the second through hole (36a); when the pressure oil flows in from the second through hole, the slide valve moves to the right, so that the opening area of the small control hole (45a) decreases. Small, so that the pressure oil flow can be kept constant. The flow control valve has a simple structure and reduces the cost.

Description

The invention relates to a flow control valve with pressure compensation function.

The flow control valve controls the passing flow by adjusting the opening size of the spool, so as to realize the speed control and adjustment of the working mechanism. The main requirement of the flow control valve is to obtain a stable flow, and the method of pressure compensation can achieve this goal.

For example, various construction machinery such as hydraulic excavators are equipped with hydraulic actuators, and these hydraulic actuators can be properly driven to make the construction machinery realize the required actions. The actions of the above-mentioned hydraulic actuators are controlled by their respective reversing valves, which are operated by operating rods. In recent years, the pre-control method of driving the reversing valve with the control pressure is generally adopted. In simple terms, this control method is to connect the two control chambers in the opposite direction of the reversing valve to the control through the control pipeline. The hydraulic control circuit formed in this way on the pilot valve controlled by the rod is composed.

The action of this conventional hydraulic control circuit device will be described below by taking the reversing valve driven by the travel motor of a hydraulic excavator as an example. When the operator pulls the control lever from the middle position to one direction, the pressure oil output from the control hydraulic pump connected to the pilot valve flows into the control pipeline on the corresponding side through the pilot valve, and flows to the corresponding side of the reversing valve. oil supply to the control chamber. In this way, the reversing valve is switched to the operating position, and the pressure oil output from the main hydraulic pump flows into the main pipeline on one side through the reversing valve to supply oil to the travel motor. In the travel motor, the pressure oil that has worked has passed through the other side The main line on the side flows back to the fuel tank through the travel reversing valve. In this way, the travel motor rotates, and the hydraulic excavator travels.

When the hydraulic excavator is to be stopped, the operator can pull the joystick back to the middle position. At this moment, the pilot valve cuts off the communication between the steering pump and the steering pipeline on the above-mentioned side, so that the steering pipeline communicates with the oil tank. In this way, the pressure oil in the control chamber on one side of the reversing valve flows back to the oil tank, and the reversing valve The valve returns to the neutral position, the supply of pressurized oil from the main pump to the travel motor is stopped, and the above-mentioned main line is closed. At this time, the travel motor does not stop immediately, but the motor continues to rotate due to inertia. As a result of this rotation, the pressure oil in the main pipeline on the one side is sucked in and output to the main pipeline on the other side. Like this, the oil pressure in the control pipeline of the other side that it closes rises sharply, and this raised pressure becomes brake pressure, and travel motor is stopped.

However, in the above-mentioned existing circuit device, when the joystick returns to the middle position from the manipulation position, the reversing speed of the reversing valve returning to the middle position is very fast, thereby, in the main pipeline on the other side above-mentioned The braking pressure of the hydraulic excavator also rises very violently, and the impact on the entire body of the hydraulic excavator is also very large when the walking is about to stop. Therefore, there are disadvantages in that the operability of the hydraulic shovel is lowered, the fatigue of the operator is increased, and in addition, the life of the machine is impaired. This shortcoming is not limited to the above-mentioned hydraulic excavator, but also occurs on the hydraulic actuators of other engineering machinery, especially, the greater the load inertia of the hydraulic actuators, the more obvious this shortcoming.

In order to overcome the above shortcomings, a flow control valve can be set between the pilot valve and the reversing valve to control the flow of pressure oil from the reversing valve to the pilot valve. However, the existing flow control valve appears to have a complex structure and high cost.

Therefore, the object of the present invention is to provide a flow control valve with pressure compensation function, which can eliminate the above-mentioned shortcomings of the prior art when installed in the hydraulic circuit, ease the impact of the hydraulic actuator when it stops, and improve the operating performance. The operator's fatigue is reduced and the service life is improved, and the valve has a simple structure, which can reduce the cost.

The following are specific device diagrams for implementing various examples of the present invention.

Fig. 1 is a side view of a hydraulic shovel, one of typical construction machines, using the hydraulic control circuit device of the flow control valve of the present invention.

Fig. 2 is a top view of the hydraulic excavator shown in Fig. 1 .

Fig. 3 is a hydraulic control circuit applying the flow control valve of the present invention, which is suitable for the reversing valve of the traveling motor of the hydraulic excavator shown in Fig. 1 .

FIG. 4 is an enlarged view of the flow control valve shown in FIG. 3 .

Fig. 5 (a), (b) and (c) are coordinate diagrams of the action of the hydraulic control circuit device shown in Fig. 3 with respect to time.

Fig. 6 is another embodiment of the present invention, which is a sectional view of a flow control valve.

Fig. 7 is a sectional view of a known flow control valve.

The best example of the present invention will now be described with regard to the situation of using on a hydraulic excavator as an example. Generally, a hydraulic excavator, as shown in Figure 1 and Figure 2, has an upper revolving part 1 and a lower traveling part 2, the upper revolving part 1 is rotated by a rotary hydraulic motor 3, and the lower traveling part 2 is driven by a traveling hydraulic motor 5, 7 respectively. The left and right crawlers 4 and 6 are driven to walk, the boom 8 is supported on the upper swivel part 1 freely rotatable, the boom 9 is rotatably supported on the boom 8 , and the boom 9 is rotatably supported on the boom 9 . Bucket 10, boom 8, boom 9 and bucket 10 are driven by boom hydraulic cylinder 12 and bucket hydraulic cylinder 13 respectively.

An example of using the flow control valve of the present invention on the driving reversing valve of the traveling motor 5 controlling this hydraulic excavator is shown in FIG. 3 . In Fig. 3, symbol 15 represents the hydraulic pump installed on the hydraulic excavator, and this hydraulic pump 15 is connected with travel motor 5 through reversing valve 16, and reversing valve 16 controls the pressure oil supply from hydraulic pump 15 to travel motor 5 . On the left and right sides of the reversing valve 16, a pair of operating chambers 16a, 16b are arranged symmetrically. Symbol 17 is fuel tank. The reversing valve 16 is connected to the travel motor 5 by a pair of main pipes 18a, 18b, and a safety valve 19 is straddled between these main pipes.

Symbol 21 is the steering pump, and the maximum output pressure of the steering pump 21 is regulated by the safety valve 22 . The steering pump 21 is connected to a pilot valve 24 actuated by a joystick 23 controlling the travel motor 5 . The pilot valve 24 belongs to the prior art, and if it is roughly explained, it has a valve Body 24a, and two valve cavities 25a, 25b made on this valve body 24a, spool valves 26a, 26b are installed in valve cavities 25a, 25b; rods 27a, 27b are connected with spool valves 26a, 26b, in valve body 24a There are passages 28, 29, 30a, 30b respectively connected to the valve chambers 25a, 25b. The passage 28 connects the steering pump 21 and each valve chamber 25a, 25b with the oil tank 17. The passages 30a, 30b pass through the control pipelines 31a, 32a And the control pipelines 31b, 32b are connected to the control chambers 16a, 16b of the reversing valve 16, respectively.

As shown in the figure, the flow control valves 33a, 33b with pressure compensation function of the present invention are connected to the control pipelines 31a, 32a and the control pipelines 31b, 32b.

The detailed structure of the flow control valves 33a and 33b is now described with reference to Fig. 4. Fig. 4 only shows the flow control valve 33a on one side, and the structure of the flow control valve 33b on the other side is exactly the same, so its figures and descriptions are omitted. .

The flow control valve 33a has a valve cavity 34a, a valve body 37a, the first through hole 35a is connected to the control pipeline 31a, the control pipeline 31a is connected to the channel 30a of the pilot valve 24, and the second through hole 36a is connected to the control pipeline 32a , the control line 32a is connected to the control cavity 16a of the reversing valve 16, the spool valve 38a can slide freely in the valve cavity 34a of the valve body 37a, and there are a first hydraulic cavity 40a and a second hydraulic cavity 42a on the spool valve 38a, The hydraulic chamber 40a communicates with the first through hole 35a through the radial hole 39a; the hydraulic chamber 42a communicates with the second through hole 36a through the radial hole 41a, and there is a throttle between the first and second hydraulic chambers 40a and 42a The hole 43a and the throttling hole 43a communicate with the two hydraulic chambers at the same time. When the pressure oil passes through the throttling hole 43a, a pressure difference is generated between the two hydraulic chambers, causing the slide valve to displace. When there is pressure oil flowing in from the first through hole 35a, the displacement of the slide valve 38a is generated due to the pressure difference, forming the opening and closing opening 44a that communicates the first through hole 35a and the second through hole 36a. There is pressure oil in hole 36a When it flows in, it adapts to the pressure difference caused by the displacement of the above-mentioned pressure difference generating spool valve 38a, so that the opening area is reduced, forming a flow from the second through hole 36a, through the second hydraulic chamber 42a, the orifice 43a, the first hydraulic pressure The cavity 40a is a small control hole 45a for maintaining a constant flow rate of the pressure oil flowing out from the first through hole 35a.

In the illustrated example, the orifice 43a is formed in the shape of a small hole. In the illustrated example, the opening and closing opening 44a consists of an annular groove 46a made on the outer circumference of the slide valve 38a and the inner portion of the valve cavity 34a that can only contact the shoulder 47a on the second through hole 36a side of the annular groove 46a. The hole part, that is, the first shoulder 48a, so that the annular groove 46a usually communicates with the first through hole 35a, and at the second through hole 36a, when no pressure oil flows into the first through hole 35a, due to the shoulder 47a Contact with the shoulder 48a, the communication is cut off, and only when the pressure difference caused by the pressure oil flowing into the first through hole 35a causes the slide valve 38a to displace, the shoulder 47a and the shoulder 48a are separated and become connected to each other. The small control hole 45a is composed of the first radial hole 39a and the inner hole portion which partially closes the valve cavity 34a of the radial hole 39a, that is, the second shoulder 49a.

Between the slide valve 38a and the end surface of the valve cavity 34a, first and second springs 50a, 51a are arranged oppositely. The elastic force of the first spring 50a is determined to be stronger, and the elastic force of the second spring 51a is weaker.

Next, the operation of this embodiment can be described with reference to the time charts shown in Figs. 5(a)-(c).

Now, when the operator pulls the joystick 23 to the left of the figure at time _t1 , the spool valve 26a of the pilot valve 24 moves, and the pressure oil output by the operating hydraulic pump 21 passes through the passage 28, the valve cavity 25a, the passage 30a, the control pipeline 31a supplies oil to the first through hole 35a of the flow control valve 33a, this pressure oil flows from the first through hole 35a, through the radial hole 39a, and the first hydraulic chambers 40a, 43a flow into the second hydraulic chamber 42a , and then flows out from the radial hole 41a to the second through hole 36a. At this time, a pressure difference is generated between the first and second hydraulic chambers 40a and 42a located on both sides of the orifice 43a. When the force of this pressure difference on the slide valve is greater than the spring force of the spring 51a, it is in the middle of the figure. Position spool 38a will move to the left in the figure. In this way, the shoulder 47a of the spool valve 38a is separated from the shoulder 48a, the annular groove 46a of the spool valve 38a communicates with the second through hole 36a, and the pressure oil flowing into the first through hole 35a passes through the annular groove 46a to the second through hole. 36a flows out. Because the elastic force of the spring 51a is selected weaker, the leftward movement of the above-mentioned slide valve 38a occurs in a short time after the pressure oil flows into the first through hole 35a, and the pressure oil flows from the first through hole 35a to the second through hole 36a. Mobility is free flow without any restrictions.

The pressure oil flowing to the second through hole 36a is supplied to the operation chamber 16a of the selector valve 16 through the operation line 32a. Thus, as shown in Figure 5(b), the reversing valve 16 starts to move at time _t3 and reaches the maximum displacement at time _t4 . The time _t4 lags behind the time in the case of the circuit device without the flow control valve, and the lag will be described later.

When the reversing valve 16 moves to the left from the middle position, the pressure oil of the hydraulic pump 15 supplies oil to the traveling motor 5 through the reversing valve 16 and the main pipeline 18b, as shown in Figure 5(c), the effective pressure of the traveling motor 5 Raise and start turning. And, after time _t4 , the normal rotation is continued to make the hydraulic excavator work. From the time _t3 to the time _t4 , the shape of the effective pressure increase curve is different from the curve shape of the circuit device without the flow control valve, and this point will be described later.

When the time t ₅ is reached, if the joystick 23 is in the middle position, the valve chamber 25a of the pilot valve 24 communicates with the working oil tank 17 . Therefore, the first through hole 35a, the radial hole 39a, and the first hydraulic chamber 40a communicate with the oil tank 17, and the pressure of the second hydraulic chamber 42a is higher than the pressure of the first hydraulic chamber 40a. In this way, the pressure oil supplied to the operation chamber 16a of the selector valve 16 flows from the second through hole 36a to the flow rate control valve 33a. This pressure oil flows from the radial hole 41a, the second hydraulic chamber 42a, through the orifice 43a, through the first hydraulic chamber 40a, the radial hole 39a, the first through hole 35a, the control pipeline 31a, and the pilot valve 24. to tank 17. At this time, the amount of oil passing through the orifice 43a increases. If the pressure difference between the first and second hydraulic chambers 40a and 42a on both sides of the orifice 43a acts on the slide valve, the force is greater than the spring force of the spring 50a. , the spool valve 38a moves to the right. In this way, the opening area A of the control small hole 45a formed by the radial hole 39a and the shoulder 49a becomes smaller, and the amount of pressure oil flowing out from the first hydraulic chamber 40a through this small hole is limited. In this way, the pressure difference between the first and second hydraulic chambers 40a and 42a is kept constant, and the pressure oil flowing out from the first hydraulic chamber 40a is also constant. In this case, when the oil pressure flowing into the second through hole 36a increases, the pressure difference remains constant due to the further reduction of the opening area A. On the contrary, when the oil pressure flowing into the second through hole 36a decreases, due to The above-mentioned opening area A becomes larger, while the pressure difference remains constant, that is to say, the flow of oil flowing out from the flow control valve 33a to the control pipeline 31a, the pilot valve 24, and the oil tank 17 through the control chamber 16a, the control pipeline 32a is constant. Yes for sure. Therefore, as shown in Figure 5(b), even if the joystick 23 returns to the middle position rapidly, the return speed of the reversing valve 16 will lag behind, and it will be possible at time _t8 much later than time _t7 . Return to middle position.

As mentioned above, when the return speed of the reversing valve 16 to its intermediate position is limited, the main pipes 18a, 18b will not be cut off abruptly, therefore, as shown in FIG. The increase in brake pressure has also become slower. In this way, the shock acting on the whole body of the hydraulic excavator at the time of parking is also greatly alleviated, the operability and mechanical life are improved, and the fatigue of the operator is also reduced.

有效压力升高的曲线形状进行说明。如上所述，当操纵杆23扳到左侧时，在时间t₃换向阀16才开始切换。这种情况下，在流量控制阀33a上几乎不产生压力损失。当换向阀16开始切换时，在换向阀16的操纵腔16b以及操纵管路32b中的压力油，经过流量控制阀33b，操纵管路31b，先导阀24向油箱17排出。这时，从流量控制阀33b的第2通孔36b（相当于流量控制阀33a的第2通孔36a）流向第1通孔35b（相当于流量控制阀33a的第1通孔35a）的压力油，如在流量控制阀33a中所述那样，也受到限制。这样，换向阀16达到最大位移量的时间t₄比不存在流量控制阀33b的情况下的时间也滞后。但是，这种情况下，在换向阀16的动作开始时间t₃，操纵腔16b已经处在与油箱17相连通的状态，即使由于换向阀16从此状态的移动使压力油被从操纵腔16b挤出，这股压力油被构成管路的高压软管的变形和油本身的压缩性所吸收，而通过流量控制阀33b的节流孔43b（相当于流量控制阀33a的节流孔43a）的流量很小，节流孔43b两侧的压力差也很小，因而压力油流动受限制的程度小。然而，虽说这种被限制的程度减小，但因为限制的本身仍然存在，所以换向阀16的切换速度滞后，这样，经过主管路18b，供给行走马达5的压力油的压力升高变得缓慢了，如图5（c）所示那样，行走马达5起动时的冲击也就缓和了。When the joystick 23 is manipulated from the middle position, the action lag time _t4 of the reversing valve 16 and the travel motor 5

The shape of the curve for effective pressure rise is illustrated. As mentioned above, when the joystick 23 is turned to the left, the reversing valve 16 starts switching at time _t3 . In this case, almost no pressure loss occurs in the flow rate control valve 33a. When the reversing valve 16 starts switching, the pressure oil in the control chamber 16b of the reversing valve 16 and the control pipeline 32b passes through the flow control valve 33b, the control pipeline 31b, and the pilot valve 24 is discharged to the oil tank 17. At this time, the pressure flowing from the second through hole 36b (corresponding to the second through hole 36a of the flow control valve 33a) of the flow control valve 33b to the first through hole 35b (corresponding to the first through hole 35a of the flow control valve 33a) Oil, as described in flow control valve 33a, is also restricted. In this way, the time _t4 at which the selector valve 16 reaches the maximum displacement is also later than the time when there is no flow control valve 33b. However, in this case, at the start time _t3 of the action of the reversing valve 16, the control chamber 16b is already in the state of communicating with the oil tank 17, even if the pressure oil is drawn from the control chamber due to the movement of the reversing valve 16 from this state. 16b, this pressure oil is absorbed by the deformation of the high-pressure hose forming the pipeline and the compressibility of the oil itself, and passes through the orifice 43b of the flow control valve 33b (equivalent to the orifice 43a of the flow control valve 33a ) is very small, and the pressure difference on both sides of the orifice 43b is also very small, so the flow of pressure oil is limited to a small extent. However, although the degree of this restriction is reduced, because the restriction itself still exists, the switching speed of the reversing valve 16 lags behind, and like this, the pressure of the pressure oil supplied to the traveling motor 5 increases through the main pipe 18b. Slowly, as shown in Figure 5 (c), the impact when the travel motor 5 starts is also eased.

In this way, in this example, since the flow control valve is placed on the two control pipelines connecting the pilot valve and the reversing valve, it can alleviate the impact of the travel motor when it stops and starts, thereby improving the operating performance and life, and can Reduce operator fatigue.

In addition, in this embodiment, because the flow control valve with pressure compensation function is connected, when the pressure oil flows into the second through hole, even if the pressure fluctuation of the pressure oil is caused by the fluctuation of the load of the hydraulic actuator, a certain pressure can still be obtained. flow, the travel motor can achieve more stable parking.

In addition, in the illustrated example, when the pressure oil flows into the second through hole, since the restriction on the flow of the pressure oil is realized by the throttling orifice and the control orifice that generate pressure difference, their opening area can be larger , so there is no concern about the clogging of small holes caused by dust in the pressure oil. Moreover, due to the existence of small holes, even if the viscosity of the oil increases at low temperatures, the pressure loss when passing through the small holes can also be reduced to maintain a certain level. pressure compensation function.

According to this embodiment, the opening and closing opening and the control hole of the flow control valve are formed by the inner hole of the valve cavity of the slide valve and the valve core, the structure is very simple, and the cost can be reduced.

Fig. 6 is a cross-sectional view of a flow control valve according to another embodiment of the present invention. In the figure, 50 represents a flow control valve. This flow control valve 50 replaces the flow control valves 33a, 33b with pressure compensation function in the previous example, and is connected between the control lines 31a and 32a and between 31b and 32b. 51 is the first through hole connected to the control pipelines 31a and 31b, and 52 is the second through hole connected to the control pipelines 32a and 32b. 53 is the spool, 54 is the spring that pushes the spool 53, 55a, 55b are the first and second hydraulic chambers, 56 is the orifice on the top of the spool 53 with an elongated small hole shape, 57 is the connecting The hole 58 on the spool 53 between the first and second hydraulic chambers 55a, 55b is a valve seat.

In the hydraulic circuit shown in Fig. 3, this kind of flow control valve 50 is set instead of the flow control valves 33a, 33b with pressure compensation function. When the control lever 23 is pulled to the left, the oil output by the control hydraulic pump 21 , through the pilot valve 24, the control pipeline 31a supplies oil to the first through hole 51 of the flow control valve 50. Because of this, the spool 53 overcomes the elastic force of the spring 54 and is pushed downward, and the pressure oil passes through the first through hole 51, the first hydraulic chamber 55b, the hole 57, the second hydraulic chamber 55a, the second through hole 52, and then passes through the control pipeline 32a to the The control chamber 16a of the reversing valve 16 is supplied with oil. At this time, almost no pressure loss occurs in the flow control valve 50 . When the reversing valve 16 starts to move, the oil in the pilot chamber 16b is discharged back to the oil tank through the pilot pipeline 32b, the flow control valve 50, the pilot pipeline 31b, and the pilot valve 24. At this time, in the flow control valve 50, since the pressure oil passes through the orifice 56, the switching speed of the reversing valve 16 will be slower, so that the impact when the travel motor 5 is started is relaxed.

When the joystick 23 is returned to the middle position and the travel motor 5 is stopped, the oil in the manipulation chamber 16a and the manipulation pipeline 32a flows to the second through hole 52 of the flow control valve 50, and the top of the valve core 53 is pressed against the valve seat. 58 on. Therefore, the pressurized oil flows only through the orifice 56 to the second through hole 51 , passes through the pilot line 31 a, and is discharged to the oil tank 17 by the pilot valve 24 . In this way, the oil return of pressure oil is restricted by the orifice 56, and the return speed of the reversing valve 16 becomes slow. In this way, the brake pressure of the main pipeline 18a rises slowly, and the impact of the traveling motor 5 when it stops can be greatly reduced. ease.

In this way, in this embodiment, since the flow control valve is installed on the two control pipelines connecting the pilot valve and the reversing valve, as in the previous example, the effect of mitigating the impact can also be achieved when starting and stopping, and, Due to the simple structure of the flow control valve, the cost can be further reduced.

Fig. 7 is a sectional view of a known flow control valve. Symbol 60 in the figure represents the known flow control valve with pressure compensation function, its structure is different from the flow control valve 33a with pressure compensation function shown in Figure 4, this flow control valve 60, in the hydraulic control circuit shown in Figure 3 On the device, instead of the flow control valves 33a and 33b, it is connected between the pilot lines 31b and 32b. The flow control valve 60 has first and second through holes 61 and 62, the first The through hole 61 is connected to the control lines 31a and 31b, and the second through hole 61 is connected to the control lines 32a and 32b. Between the 1st and the 2nd through-hole 61 and 62, the through-hole 63,64 that links to each other with these through-holes is respectively provided with, only allows pressure oil to flow to the 2nd through-hole 62 check valve 65 from the 1st through-hole 61 and A spool valve 66 arranged in parallel with the non-return valve and a pressure compensating section with an orifice 67 are connected. The spool valve 66 has a large-diameter portion 66a and a small-diameter portion 66b at both ends, which slide freely in the first and second hydraulic chambers 68a and 68b respectively, and form a connection with the first and second hydraulic chambers 68a and 68b. The intermediate chamber 70 communicated with the second through hole 62 is also communicated with the internal passage 69 . A spring 71 is attached to an outer portion of the first hydraulic chamber 68 a, and this portion communicates with the first through hole 61 through a passage 72 . The inner portion of the first hydraulic chamber 68a and the second hydraulic chamber 68b communicate with the internal passage 69 through passages 73 and 74, respectively. The small hole 67 is located at the junction of the internal passage 69 and the first through hole 61, and it is formed by a crescent-shaped groove on the manual lever 67a, and the position of the groove can be changed by turning the lever 67a, thereby adjusting the position of the small hole. Opening area.

In such a flow control valve 60 , when pressure oil flows into the first through hole 61 , the pressure oil passes through the check valve 65 and freely flows to the second through hole 62 . When the pressure oil flows into the second through hole 62, this pressure oil flows to the first through hole through the intermediate cavity 70, the internal channel 69, and the small hole 67. At this time, the pressure oil passes through the small hole 67 to generate a pressure difference between the internal passage 69 and the first through hole 61, and this pressure difference is transmitted to the first and second hydraulic chambers 68a and 68b. As the valve 66 moves to the right, the opening area of the small hole 75 formed between the small diameter portion 66b and the opening portion of the second through hole 62 of the intermediate chamber 70 decreases. Therefore, the flow rate of the pressure oil flowing into the first through hole 61 from the second through hole 62 is kept constant.

Therefore, in the hydraulic control circuit device shown in Figure 3, with this pressure compensation The compensation function of the flow control valve 60 can also achieve the same effect as that of the flow control valves 33a and 33b. However, this kind of flow control valve has a complicated structure and high cost.

In the above examples, the travel motor reversing valve of the hydraulic excavator is used as an example for illustration, but obviously, it is not limited thereto, and is also applicable to the reversing valves of various actuators of various engineering machinery. In addition, the above is an example in which flow control valves are installed on both control lines. However, according to changes in actuators or load conditions, it is also possible to install flow control valves on only one control line.

Above-mentioned each example is with the reversing valve that has two control chambers of symmetrical configuration as example explanation, but, also can be used in those only be provided with control chamber at one end, only have the reversing valve of spring independent action at the other end.

Claims (5)

1, a kind of flow control valve with pressure compensation, this valve include valve body (37a) and guiding valve (38a); Valve body (37a) has valve pocket (34a) and opening the 1st and the 2nd through hole (35a, 36a) at this valve pocket; Guiding valve 38a is inserted in the above-mentioned valve pocket of valve body sliding freely, it includes the 1st hydraulic pressure cavity (40a) that is communicated with above-mentioned the 1st through hole, the 2nd hydraulic pressure cavity (42a) that is communicated with above-mentioned the 2nd through hole and between the 1st and the 2nd hydraulic pressure cavity, be communicated with two hydraulic pressure cavity throttle orifices (43a) when pressure oil passes through, between two hydraulic pressure cavity, produce pressure difference, make guiding valve produce displacement;

It is characterized in that: be provided with and open and close opening (44a) and control aperture (45a), switching opening are made of the cylindrical of above-mentioned guiding valve and the inwall of above-mentioned valve pocket, have only when pressure oil when the 1st through hole flows into, the above-mentioned spool displacement that relies on above-mentioned pressure difference to produce just can be opened, and above-mentioned the 1st through hole and the 2nd through hole are communicated with; The control aperture is made of with above-mentioned valve pocket inwall above-mentioned the 1st hydraulic pressure cavity part of above-mentioned guiding valve, has only pressure oil when above-mentioned the 2nd through hole flows into, because the spool displacement that above-mentioned pressure difference produced, corresponding with this pressure difference, opening area is reduced, flow into and through the 2nd hydraulic pressure cavity, throttle orifice, the 1st hydraulic pressure cavity thereby make from the 2nd through hole, the flow of the pressure oil that flows out from the 1st through hole keeps certain.

2, by the described flow control valve of claim 1, it is characterized in that above-mentioned throttle orifice is aperture (43a).

3, by the described flow control valve of claim 1, it is characterized in that opening and closing opening (44a) have the circular groove (46a) on the cylindrical of guiding valve (38a), opened and with contacted the 1st shoulder of shoulder (47a) (48a) of the 2nd through hole (33a) side of this circular groove, circular groove often is communicated with the 1st through hole (35a), in the 2nd through hole, when not having pressure oil to flow into the 1st through hole, because shoulder contacts with the 1st shoulder, make to be communicated with and cut off, have only when pressure oil flows into the 1st through hole, the spool displacement that causes owing to pressure difference makes shoulder (47a) leave with the 1st shoulder (48a) to be communicated with.

4, by the described flow control valve of claim 1, it is characterized in that, the the 1st and the 2nd hydraulic pressure cavity (40a, 42a) the 1st and the 2nd radial hole (39a by opening respectively at guiding valve (38a), 41a) with the 1st and the 2nd through hole (35a, 36a) be connected, control aperture (45a) is made up of the 1st radial hole and the 2nd shoulder (49a), and this shoulder (49a) can partly be closed this radial hole.

5, by the described flow control valve of claim 1, it is characterized in that the 1st and the 2nd hydraulic pressure cavity (40a at guiding valve (38a), (50a, 51a), the elastic force of bigger the 2nd spring of the elastic force of the 1st spring is less to be separately installed with the spring of the 1st relative configuration with the 2nd 42a).

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