Pilot operated hydraulic valve, hydraulic control system and engineering machine

Abstract

This invention relates to the field of hydraulic control systems, and discloses a pilot-operated hydraulic valve, a hydraulic control system, and engineering machinery. The pilot-operated hydraulic valve includes a valve body (1), a valve core (2), and a spring cavity (3) disposed at the end of the valve core. A limiting screw (4) adjustable in the direction toward or away from the valve core is provided at the end of the spring cavity away from the valve core. A first spring seat (5) is connected to the end of the limiting screw facing the valve core. A pilot spring (7) with one end abutting against the first spring seat is provided inside the spring cavity, so that the limit sliding position of the valve core can be determined by the adjustment position of the limiting screw when the valve core is driven to slide against the elastic force of the pilot spring. This invention can maintain the same or substantially the same maximum pilot control pressure when the limiting screw is adjusted to different maximum output flow rates, thereby maintaining a stable pilot control pressure utilization rate and being applicable to hydraulic control systems with different flow requirements.

Description

Technical Field

[0001] This invention relates to hydraulic control systems, and more specifically to a pilot-operated hydraulic valve. Furthermore, this invention also relates to a hydraulic control system including the pilot-operated hydraulic valve and engineering machinery incorporating the hydraulic control system. Background Technology

[0002] Pressure and flow rate are key performance parameters in hydraulic control systems. Pressure determines the load capacity of the actuator, while flow rate affects the speed of its movement. In a hydraulic control system, the pilot-operated hydraulic valve, as a hydraulic control element, is driven by a pilot control pressure (pilot pressure). The stroke of this valve spool affects the flow rate output through the valve. To limit the valve spool's stroke range, a limit screw is typically installed at the end of the valve spool to restrict the maximum flow rate output through the hydraulic valve.

[0003] Figure 1 The diagram shown is a cross-sectional view of a pilot-operated directional valve in the prior art, which has a first working port A and a second working port B for outputting hydraulic oil. The pilot-operated directional valve has a valve body 1 and a valve core 2 (valve stem) slidably mounted within the valve body 1. The valve core 2 can slide to different reversing positions to control the flow rate of hydraulic oil output through the first working port A and the second working port B.

[0004] The valve core 2 is driven by a pilot control pressure generated by the pressure oil acting on its end. Its limit sliding position is determined by the limit screw 4 located at the end of the valve core 2. Specifically, when pressure oil is introduced into the spring chamber 3 on the right side of the directional valve, a leftward pilot control pressure is applied to the valve core 2, causing the valve core 2 to overcome the elastic force of the pilot spring 7 in the left spring chamber 3 and slide to the left until the left end of the valve core 2 contacts the limit screw 4, reaching its limit sliding position to the left. At this time, the output flow rate of the first working port A reaches its maximum value.

[0005] In this process, the magnitude of the pilot control pressure corresponds to the compression length of the pilot spring 7, and thus to the output flow rate through the working port. Generally, the maximum and minimum pilot control pressures provided to the hydraulic valve in the hydraulic control system are fixed values, corresponding to the spring force of the pilot spring 7 in the initial state (normal state) and in the extreme sliding position where the valve core 2 abuts against the limit screw 4, respectively. Figure 2 As shown, the stroke of valve core 2 and the output flow of the hydraulic valve are directly proportional to the magnitude of the pilot pressure.

[0006] In this situation, if the maximum output flow rate needs to be increased, the maximum pilot pressure must be increased accordingly. However, the designed pilot pressure cannot meet the pressure requirement corresponding to the increased maximum output flow rate, making it impossible to increase the maximum flow rate by adjusting the limit screw 4. Figure 3 As shown; conversely, if it is necessary to reduce the maximum output flow rate, the limit screw 4 can be adjusted so that only a small pilot pressure is required to achieve the adjusted maximum flow rate. However, at this time, the pilot pressure has not yet reached the designed maximum pilot pressure, resulting in a waste of pilot pressure in some sections, such as... Figure 4 As shown. This limits the versatility of hydraulic valves. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem of poor versatility of existing pilot-operated hydraulic valves and to provide a pilot-operated hydraulic valve that can simultaneously change the compression amount of the pilot spring corresponding to the limit compression state of the maximum output flow when the maximum output flow is adjusted by the limit screw, so as to maintain a stable pilot control pressure utilization rate and effectively improve the versatility in hydraulic control systems with different flow requirements.

[0008] To achieve the above objectives, the present invention provides a pilot-operated hydraulic valve, comprising a valve body, a valve core slidably mounted within the valve body, and a spring cavity disposed at the end of the valve core. The end of the spring cavity away from the valve core is provided with a limiting screw adjustable in a direction toward or away from the valve core. The end of the limiting screw facing the valve core is connected to a first spring seat. A pilot spring, with one end abutting against the first spring seat, is disposed within the spring cavity, so that the limit sliding position of the valve core can be determined by the adjustment position of the limiting screw when the valve core is driven to slide against the elastic force of the pilot spring.

[0009] Preferably, a control end cap is connected to the end of the valve body, and the spring cavity is formed within the control end cap.

[0010] Preferably, the spring cavity is provided with a second spring seat that is spaced apart from the first spring seat. The end of the pilot spring facing the valve core abuts against the second spring seat. During at least a portion of the sliding stroke of the valve core, the valve core can be driven to slide towards the limit sliding position by overcoming the elastic force of the pilot spring through the second spring seat.

[0011] Preferably, a retaining ring is installed on the inner peripheral wall of the control end cover. The retaining ring is located on the side of the second spring seat facing the valve core to stop the second spring seat from moving toward the valve core. Under normal conditions, the valve core and the opposite ends of the second spring seat are spaced apart from each other.

[0012] Preferably, a return spring is connected to the end of the valve core. The return spring is configured such that the valve core is in the neutral position under normal conditions, and the valve core can be driven to slide back and forth against the elastic force of the return spring. The stiffness K of the pilot spring is greater than the stiffness Ka of the return spring.

[0013] Preferably, the spring cavity is provided with a third spring seat, a fourth spring seat, and a connecting bolt that passes through the third spring seat and the fourth spring seat in sequence and connects to the valve core. A stepped portion is formed in the control end cover. The side of the third spring seat away from the valve core can abut against the stepped portion. The two ends of the return spring abut against the third spring seat and the fourth spring seat respectively.

[0014] Preferably, the stiffness K of the pilot spring is greater than twice the stiffness Ka of the return spring.

[0015] Preferably, the valve core is provided with a spring cavity, a pilot spring and a limiting screw symmetrically arranged at both ends, so that the limit sliding position of the valve core to slide to both sides can be determined by adjusting the limiting screw, and / or the pilot-operated hydraulic valve is a directional valve.

[0016] A second aspect of the present invention provides a hydraulic control system including the above-described pilot-operated hydraulic valve.

[0017] A third aspect of the present invention provides an engineering machine having the above-described hydraulic control system.

[0018] Through the above technical solution, when the limit sliding position of the valve core and the maximum output flow of the hydraulic valve are changed by adjusting the position of the limit screw, the first spring seat moves synchronously with the limit screw toward or away from the valve core, thereby changing the initial compression of the pilot spring in the initial state. This makes the compression of the pilot spring in the limit compression state before and after the corresponding adjustment of the maximum output flow constant, corresponding to the same or basically the same maximum pilot control pressure, maintaining a stable pilot control pressure utilization rate, and effectively improving the versatility of the pilot-operated hydraulic valve in hydraulic control systems with different flow requirements. Attached Figure Description

[0019] Figure 1 This is a cross-sectional structural diagram of a pilot-operated directional valve in the prior art;

[0020] Figure 2 yes Figure 1 Diagram showing the matching relationship between pilot pressure, output flow rate, and valve stem stroke in the design of a pilot-operated directional valve;

[0021] Figure 3 yes Figure 1 A diagram showing the matching relationship between pilot pressure, output flow rate, and valve stem stroke after increasing the maximum flow rate of a pilot-operated directional valve.

[0022] Figure 4 yes Figure 1 A diagram showing the matching relationship between pilot pressure, output flow rate, and valve stem stroke after reducing the maximum flow rate of a pilot-operated directional valve.

[0023] Figure 5 This is a cross-sectional structural schematic diagram of a pilot-operated hydraulic valve according to a preferred embodiment of the present invention.

[0024] Figure 6 yes Figure 5 A partial enlarged view of a pilot-operated hydraulic valve, in which the valve core is in the initial position;

[0025] Figure 7 yes Figure 6 A schematic diagram showing the valve core being driven to the end of the low flow range.

[0026] Figure 8 yes Figure 6 A schematic diagram showing the valve core being driven to its maximum flow rate.

[0027] Figure 9 yes Figure 5 The diagram shows the matching relationship between the pilot pressure, output flow rate, and valve stem stroke of a pilot-operated hydraulic valve.

[0028] Explanation of reference numerals in the attached figures

[0029] 1-Valve body; 2-Valve core; 3-Spring cavity; 4-Limit screw; 5-First spring seat; 6-Second spring seat; 7-Pilot spring; 8-Control end cover; 8a-Step portion; 9-Snap ring; 10-Reset spring; 11-Third spring seat; 12-Fourth spring seat; 13-Connecting bolt. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0031] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "left," and "right" generally refer to the upper, lower, left, and right as shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0032] Reference Figure 5As shown, according to a preferred embodiment of the present invention, a pilot-operated hydraulic valve can be, for example, a directional valve, and has symmetrical pilot control structures at both ends. For example, it can have symmetrical spring cavities 3, pilot springs 7, and limiting screws 4, so that the limit sliding position of the valve core 2 can be determined by adjusting the limiting screws 4. The pilot-operated hydraulic valve includes a valve body 1, a valve core 2 slidably mounted within the valve body 1, and a spring cavity 3 disposed at the end of the valve core 2. A limiting screw 4, adjustable in a direction toward or away from the valve core 2, is provided at the end of the spring cavity 3 away from the valve core 2. A first spring seat 5 is connected to the end of the limiting screw 4 facing the valve core 2. A pilot spring 7, with one end abutting against the first spring seat 5, is provided within the spring cavity 3, so that the limit sliding position of the valve core 2 can be determined by the adjustment position of the limiting screw 4 when the valve core 2 is driven to slide against the elastic force of the pilot spring 7.

[0033] For ease of understanding, the connecting bolt 13, return spring 10, and third spring seat 11 and fourth spring seat 12, which are connected to the end of the valve core 2 in the preferred embodiment shown in the figure, can be regarded as part of the valve core 2. Thus, the limit sliding position of the valve core 2 towards the limiting screw 4, i.e., the position where the valve core 2 (i.e., the connecting bolt 13) pushes the second spring seat 6 to contact the first spring seat 5 (e.g., ...). Figure 8 (As shown). Based on this, when the limit sliding position of the valve core 2 and the maximum output flow of the hydraulic valve are changed by adjusting the position of the limit screw 4, the first spring seat 5 moves synchronously with the limit screw 4 in the direction toward or away from the valve core 2, thereby changing the initial compression of the pilot spring 7 in the initial state, so that the compression of the pilot spring 7 in the limit compression state before and after the corresponding adjustment of the maximum output flow is constant, corresponding to the same or basically the same maximum pilot control pressure.

[0034] Taking increasing the maximum output flow rate as an example, before adjustment, the compression of the pilot spring 7 corresponding to the maximum output flow rate is determined by the spring length when the first spring seat 5 and the second spring seat 6 are in contact. That is, the length of the pilot spring 7 in the ultimate compression state is the length when the first spring seat 5 and the second spring seat 6 are in contact. Adjusting the limit screw 4 to move it away from the valve core 2, thus, in the initial state, the initial compression of the pilot spring 7 decreases (the initial length of the pilot spring 7 increases). However, since the length of the pilot spring 7 in the adjusted ultimate compression state is still the length when the first spring seat 5 and the second spring seat 6 are in contact, the required maximum pilot control pressure remains basically the same as before. Therefore, the pilot-operated hydraulic valve of the present invention can maintain a stable pilot control pressure utilization rate, effectively improving the versatility of the pilot-operated hydraulic valve in hydraulic control systems with different flow requirements. The above description of the advantages of the present invention can be better understood through the subsequent analysis of the preferred embodiments of the present invention.

[0035] It is understandable that, although the above description analyzes the maximum pilot control pressure required before and after adjustment based on the relative positional change of the second spring seat 6 and the first spring seat 5 for better understanding, the second spring seat 6 is not necessary to achieve a stable pilot control pressure utilization rate. For example, the end of the valve core 2 can be directly abutted against the pilot spring 7.

[0036] Continue to refer to Figure 5 As shown, the spring cavity 3 can typically be formed within the control end cover 8, thereby allowing for convenient installation of relevant components within the spring cavity 3 via the control end cover 8, which is detachably connected to the valve body 1.

[0037] The pilot-operated hydraulic valve of the preferred embodiment shown in the figure includes a first spring seat 5 and a second spring seat 6 disposed at a distance from each other within a spring cavity 3, with both ends of a pilot spring 7 abutting against the first spring seat 5 and the second spring seat 6, respectively. Thus, when... Figure 7 The position shown is towards Figure 8 Within the sliding stroke at the position shown, the valve core 2 is driven to slide to its limit position by overcoming the elastic force of the pilot spring 7 through the second spring seat 6. Figure 8 Slide at the position shown.

[0038] It should be understood that, in an alternative embodiment, the pilot-operated hydraulic valve of the present invention may not have the structure such as the return spring 10 described later, but instead has the valve core 2 (such as...) Figure 1 As shown, the valve core 2 directly abuts against the second spring seat 6, thus requiring the valve core 2 to overcome the spring force of the pilot spring 7 throughout its entire sliding stroke from the initial position to the limit sliding position.

[0039] As previously described, the present invention adjusts the maximum output flow rate by adjusting the position of the limit screw 4, and maintains the same or substantially the same maximum pilot control pressure before and after adjustment by causing the first spring seat 5 to move accordingly. However, the movement of the first spring seat 5 may cause a change in the initial compression of the pilot spring 7, which in turn causes a change in the minimum pilot control pressure required to drive the valve core 2. Therefore, in the illustrated preferred embodiment, the second spring seat 6 is normally spaced apart from the valve core 2 (connecting bolt 13), thereby allowing it to be divided into a small flow range and a large flow range including different maximum output flow rates by the return spring 10 described later. For this purpose, a retaining ring 9 can be installed on the inner peripheral wall of the control end cover 8, such that the retaining ring 9 is engaged with the side of the second spring seat 6 facing the valve core 2 to prevent it from moving toward the valve core 2. In normal conditions, the valve core 2 does not experience any force from the pilot spring 7 and can be held in the neutral position, as corresponding to the closed state, only by the action of the return spring 10 connected to the end of the valve core 2.

[0040] Furthermore, since the valve core 2 must constantly overcome the spring force of the return spring 10 during its operation, in order to reduce its impact on the maximum pilot control pressure corresponding to the maximum output flow before and after adjustment, the stiffness Ka of the return spring 10 needs to be much smaller than the stiffness K of the pilot spring 7. For example, the stiffness K of the pilot spring 7 can be more than twice the stiffness Ka of the return spring 10. As will be explained later, the difference in their stiffness has a significant impact on whether the maximum pilot control pressure can remain essentially the same.

[0041] Combination Figure 6 As shown, in order to connect the return spring 10 to the end of the valve core 2 and ensure that the valve core 2 is in the neutral position under its action, the third spring seat 11 and the fourth spring seat 12 can be connected to the end of the valve core 2 by connecting bolts 13. The two ends of the return spring 10 abut against the third spring seat 11 and the fourth spring seat 12, respectively; a stepped portion 8a is formed inside the control end cover 8, and the end of the return spring 10 facing away from the valve core 2 can abut against this stepped portion 8a; the fourth spring seat 12 can abut against the end face of the valve body 1 under the action of the return spring 10.

[0042] The following is combined with Figure 6 The valve core shown is in its initial position to Figure 8 The sliding process of the valve core being driven to maximum flow illustrates the change in pilot pressure required before and after regulation. Here, the effective area of ​​the valve core under which the pilot pressure acts is denoted as A, and the pilot pressure itself is denoted as P.

[0043] from Figure 6 Slide to the initial position Figure 7 At the end of the low flow range shown, the stroke of valve core 2 is Sa, and the force balance relationship during this process is as follows:

[0044] A*P=Ka*(H0a-H1-S) (1)

[0045] In the formula, H0a is the free length of the return spring 10, H1 is the length of the return spring 10 in the initial state, and S is the stroke of the valve core 2.

[0046] from Figure 7 The indicated end position of the low flow range is slid to... Figure 8 At the maximum flow position shown, the stroke of valve core 2 is Sb, and the force balance relationship during this process is as follows:

[0047] A*P=Ka*(H0a-H1-S)+K*(H0b-H2-(S-Sa)) (2)

[0048] In the formula, H0b is the free length of the pilot spring 7, and H2 is the length of the pilot spring 7 in the initial state.

[0049] According to equation (1), the pilot pressure P2 corresponding to the end position of the low flow range is:

[0050] P2=(Ka*(H0a-H3)) / A (3)

[0051] Where: H3 = H1 - Sa, which means the length of the reset spring 10 at the end of the low flow interval.

[0052] According to equation (2), the pilot pressure P3 corresponding to the maximum flow rate is:

[0053] P3=(Ka*(H0a-H5)+K*(H0b-H6)) / A (4)

[0054] Where: H5 = H1 - Sa - Sb, which means the length of the return spring 10 at maximum flow rate; H6 = H2 - Sb, which means the length of the pilot spring 7 at maximum flow rate.

[0055] If the maximum flow rate is increased, the limit screw 4 needs to be adjusted so that the stroke Sb of the valve core 2 sliding from the end position of the small flow rate range to the maximum flow rate position increases, denoted as Sb' = Sb + X, where X is the stroke increment.

[0056] According to equation (3), the pilot pressure P2' corresponding to the end position of the adjusted low flow range is:

[0057] P2'=(Ka*(H0a-H3')) / A (5)

[0058] Where: H3' = H1 - Sa, which is equal to the length of the reset spring 10 at the end position of the small flow range before adjustment, so P2' = P2. Within the small flow range, the pilot pressure required before and after adjustment remains unchanged, thus the minimum pilot control pressure required to drive the valve core 2 remains unchanged.

[0059] According to equation (4), the pilot pressure P3' corresponding to the adjusted maximum flow rate is:

[0060] P3'=(Ka*(H0a-H5')+K*(H0b-H6')) / A (6)

[0061] Where: H5' = H1 - Sa - (Sb + X) = H5 - X; H6' = (H2 + X - (Sb + X) = H6, which is equal to the length of the pilot spring 7 at the maximum flow rate before adjustment. Therefore:

[0062] P3'=(Ka*(H0a-H5+X)+K*(H0b-H6)) / A=P3+(Ka*X) / A (7)

[0063] Since Ka << K, the pressure change caused by flow regulation mainly lies in the pilot spring 7, and the additional force of the return spring 10 can be neglected; therefore, P3' = P3, and the maximum pilot pressure corresponding to the maximum flow rate remains basically unchanged.

[0064] Similarly, when reducing the maximum flow rate by adjusting the limit screw 4, the pilot pressure required in the small flow rate range remains unchanged before and after adjustment, and the maximum pilot pressure corresponding to the maximum flow rate before and after adjustment also remains basically unchanged. As Figure 9 shown is the matching relationship diagram of the pilot pressure, output flow rate, and valve stem stroke of the pilot-operated hydraulic valve in the preferred embodiment of the present invention before and after flow adjustment. Thus, the pilot-operated hydraulic valve of the present invention has better versatility. Since the maximum and minimum pilot pressures and the flow rate can correspond one by one throughout the stroke, it can be used in hydraulic control systems with different maximum flow rate requirements.

[0065] On this basis, the present invention also provides a hydraulic control system including the above-mentioned pilot-operated hydraulic valve and a construction machinery having the hydraulic control system.

[0066] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any suitable combination of each specific technical feature. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A pilot-operated hydraulic valve, comprising a valve body (1), a valve core (2) slidably mounted within the valve body (1), and a spring cavity (3) disposed at the end of the valve core (2), characterized in that, The end of the spring cavity (3) away from the valve core (2) is provided with a limiting screw (4) that can be adjusted in the direction toward or away from the valve core (2). The end of the limiting screw (4) facing the valve core (2) is connected to a first spring seat (5). The spring cavity (3) is provided with a pilot spring (7) with one end abutting against the first spring seat (5) so that the limit sliding position of the valve core (2) can be determined by the adjustment position of the limiting screw (4) when the valve core (2) is driven to slide against the elastic force of the pilot spring (7). The valve body (1) is connected to a control end cap (8) at one end. The spring cavity (3) is formed in the control end cap (8). The spring cavity (3) is provided with a second spring seat (6) that is spaced apart from the first spring seat (5). The end of the pilot spring (7) facing the valve core (2) abuts against the second spring seat (6). During at least a part of the sliding stroke of the valve core (2), the valve core (2) can be driven to slide towards the limit sliding position by overcoming the elastic force of the pilot spring (7) through the second spring seat (6). The valve core (2) is connected to a return spring (10) at its end. The return spring (10) is configured to make the valve core (2) in the neutral position under normal conditions. The valve core (2) can be driven to slide back and forth against the elastic force of the return spring (10). The stiffness K of the pilot spring (7) is greater than the stiffness Ka of the return spring (10). The spring cavity (3) is provided with a third spring seat (11), a fourth spring seat (12) and a connecting bolt (13) that passes through the third spring seat (11) and the fourth spring seat (12) and connects to the valve core (2). The control end cover (8) has a stepped portion (8a) formed inside. The side of the third spring seat (11) away from the valve core (2) can abut against the stepped portion (8a). The two ends of the return spring (10) abut against the third spring seat (11) and the fourth spring seat (12) respectively.

2. The pilot-operated hydraulic valve according to claim 1, characterized in that, A retaining ring (9) is installed on the inner peripheral wall of the control end cover (8). The retaining ring (9) is located on the side of the second spring seat (6) facing the valve core (2) to stop the second spring seat (6) from moving toward the valve core (2). Under normal conditions, the valve core (2) and the second spring seat (6) are spaced apart from each other at their opposite ends.

3. The pilot-operated hydraulic valve according to claim 1, characterized in that, The stiffness K of the pilot spring (7) is more than twice the stiffness Ka of the return spring (10).

4. The pilot-operated hydraulic valve according to claim 1, characterized in that, The valve core (2) is provided with a spring cavity (3), a pilot spring (7) and a limiting screw (4) symmetrically arranged at both ends, so that the limit sliding position of the valve core (2) can be determined by adjusting the limiting screw (4), and / or the pilot hydraulic valve is a directional valve.

5. A hydraulic control system, characterized in that, The hydraulic control system includes a pilot-operated hydraulic valve according to any one of claims 1 to 4.

6. An engineering machinery, characterized in that, The construction machinery has a hydraulic control system as described in claim 5.

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