CN214662227U - Proportional valve for regeneration function - Google Patents

Abstract

A proportional valve for regeneration function comprising: the valve body is provided with an oil inlet, an oil return port, a first working oil port and a second working oil port; the valve core is arranged in the valve body, and a first oil return control section, a first oil groove section, an oil inlet control section, a second oil groove section and a second oil return control section are sequentially arranged on the valve core in the axial direction from the first side to the second side. An oil return opening is formed in the circumferential surface of the second oil return control section, and communication is established between the second working oil port and the oil return opening only through the oil return opening under the first valve position. The oil return opening defines a total cross-sectional area that decreases in an axial direction from the first side to the second side. Within the effective valve core displacement range limited by the axial length of the oil return opening, an oil return flow area amplification switching point exists, the oil return flow area at the position of 100% effective valve core displacement is at least 3 times of the oil return flow area at the switching point, and the switching point is located within 70% -90% effective valve core displacement.

Description

Proportional valve for regeneration function

Technical Field

The present application relates to a hydraulic control valve, and more particularly, to a proportional valve for regeneration function.

Background

Many working elements of mechanical equipment are hydraulically driven. The work load experienced by the work elements may vary widely when the machine is engaged in various tasks. For example, a bucket of an excavator is mainly engaged in a grading operation and an excavating operation. In grading operations, the bucket moves quickly over the ground and is subjected to less load. In a digging operation, where the bucket is digging into the ground, the speed of movement is much less than in a grading operation, and the loads experienced are much greater than in a grading operation.

The movement of the excavator bucket is mainly realized by driving a bucket rod through a bucket rod oil cylinder. The control valve of the arm cylinder is typically designed to provide a hydraulic regeneration function so that the bucket can move quickly when operating on level ground.

Similar situations exist for hydraulic systems of other mechanical devices. That is, the hydraulic system drives the working element to perform a low load operation and a high load operation. In low load operation, the control valve enables hydraulic regeneration to achieve rapid low load operation.

In the prior art, the hydraulic regeneration function of the control valve is usually realized by means of a complicated control valve structure or an auxiliary hydraulic circuit.

SUMMERY OF THE UTILITY MODEL

It is an object of the present application to provide a proportional valve for a hydraulic system which, by means of a spool design, achieves a hydraulic regeneration function in a simple manner.

To this end, the present application provides, in one aspect thereof, a proportional valve for regeneration function, comprising:

the valve body is provided with an oil inlet, an oil return port, a first working oil port and a second working oil port; and

the valve core is arranged in the valve body in an axial sliding mode, a first oil return control section, a first oil groove section, an oil inlet control section, a second oil groove section and a second oil return control section are sequentially arranged on the valve core from the first side to the second side in the axial direction, a first valve position of the proportional valve is achieved by moving the valve core in the axial direction along the direction from the first side to the second side, a first working oil port is communicated with the oil inlet at the first valve position, and a second working oil port is communicated with the oil return port;

the circumferential surface of the second oil return control section is provided with an oil return opening from a first side end surface facing the second oil groove section, communication is established between the second working oil port and the oil return opening only through the oil return opening under the first valve position, and the total cross-sectional area, which is defined by the oil return opening and is perpendicular to the axial direction, is reduced along the axial direction from the first side to the second side;

the shape and size of the oil return opening are set such that an oil return flow area amplification switching point exists within an effective valve core displacement range defined by the axial length of the oil return opening, the oil return flow area at the 100% effective valve core displacement position is at least 3 times of the oil return flow area at the switching point, and the switching point is located within 70% -90% effective valve core displacement.

In one embodiment, the oil return flow area at 100% effective spool displacement is more than 5 times the oil return flow area at the switching point.

In one embodiment, the switch point is about 85% effective spool displacement.

In one embodiment, the oil return opening comprises a plurality of oil return openings evenly distributed in a circumferential direction on a circumferential surface of the second oil return control section, a cross-sectional area of each oil return opening decreasing continuously or in stages in a direction from the first side to the second side.

In one embodiment, the plurality of oil return openings comprises at least two sets of oil return openings distributed in the circumferential direction, each set of oil return openings comprises at least one first type of oil return opening and at least one second type of oil return opening, the axial length of the first type of oil return opening is different from the second type of oil return opening, and, at each axial position, the circumferential dimension and/or the radial depth of the first type of oil return opening is the same as or different from the second type of oil return opening.

In one embodiment, each of the first-type oil return openings includes a circular arc-shaped opening portion and at least one additional opening portion extending from the circular arc-shaped opening portion to the second side and having a circumferential width smaller than the circular arc-shaped opening portion; the second type oil return openings in each group include two or more second type oil return openings, each second type oil return opening being formed by a circular arc-shaped opening portion.

In one embodiment, an oil inlet opening extending to the second side is formed on a circumferential surface of the oil inlet control section from a first side end surface facing the first oil sump section, the oil inlet opening is used for establishing communication between the first working oil port and the oil inlet at the first valve position, and an oil return flow area defined by the oil return opening is reduced along a direction from the first side to the second side.

In one embodiment, the oil inlet opening comprises a plurality of oil inlet openings circumferentially equispaced over a circumference of the oil inlet control section, the cross-sectional area of each oil inlet opening decreasing continuously or in stages in a direction from the first side to the second side.

In one embodiment, the plurality of oil inlet openings comprises at least two sets of oil inlet openings arranged alternately with each other, each set of oil inlet openings comprising at least one first type of oil inlet opening and at least one second type of oil inlet opening, the axial length of the first type of oil inlet opening being different from the second type of oil inlet opening, and the circumferential dimension and/or the radial depth of the first type of oil inlet opening being the same as or different from the second type of oil inlet opening at each axial position.

In one embodiment, the proportional valve further comprises a check valve, and the check valve connects the second working oil port with the first working oil port in the first valve position and allows the hydraulic oil to flow from the second working oil port to the first working oil port in a single direction.

The proportional valve of the present application is able to establish high back pressure and achieve hydraulic regeneration in low load operation through a simple spool design to achieve fast low load operation.

Drawings

The foregoing and other aspects of the present application will be more fully understood and appreciated by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

FIG. 1 is a fluid circuit diagram of a hydraulic system according to one embodiment of the present application;

FIG. 2 is a schematic illustration of the internal structure of a control valve in the hydraulic system of the present application;

FIG. 3 is a schematic illustration of a spool of the control valve of the present application;

fig. 4 and 5 are schematic views of the valve element operation of the control valve according to the present invention;

FIG. 6 is an expanded view of an oil feed control section of a spool of the control valve of the present application, illustrating openings in the oil feed control section;

FIG. 7 is an expanded view of an oil return control section of a spool of the control valve of the present application, illustrating an opening in the oil return control section;

fig. 8 is a schematic graph of the relationship between the spool displacement distance and the return flow area of the control valve of the present application.

Detailed Description

The present application relates generally to a control valve for a hydraulic system. Hydraulic systems are used to drive a certain working element (e.g., the stick of an excavator) in a machine tool, and the operation of an end working element (e.g., the bucket of the excavator) is primarily accomplished by the working element in work with different levels of load on the machine tool. The end working element has two work modes, a low load operation (e.g., excavator grading operation) and a high load operation (e.g., excavator digging operation).

A hydraulic system according to one embodiment of the present application is illustrated in fig. 1, and includes a hydraulic pump 1, a control valve 2, and a hydraulic actuator 3 for driving an actuating element of the hydraulic system (e.g., a stick of an excavator). The pump 1 is preferably a variable displacement pump, the displacement of which is adjustable by a controller, not shown. The pump 1 is used to supply high-pressure hydraulic oil to the actuator 3. The actuator 3 is shown as a hydraulic cylinder, but may be another type of actuator (such as a hydraulic motor).

The pump 1 is connected to the input and output ports of the actuator 3 through a hydraulic circuit. A control valve 2 is arranged in the hydraulic circuit for controlling the direction and speed of action of the actuator 3. The control valve 2 is a hydraulic control three-position five-way proportional reversing valve in the example shown in fig. 1, and a control oil path is connected to a control port on each side. The controller controls the control oil pressures (pilot pressures) of the two control oil passages to determine the valve position and the opening degree of the control valve 2.

The control valve 2 is a proportional valve having five oil ports, i.e., an oil inlet P, two oil return ports T1, T2, and a working oil port A, B. The oil inlet P is connected with the output port of the pump 1, the two oil return ports T1 and T2 are connected to the oil tank 4, and the working oil port A, B is connected with the input port and the output port of the actuator 3, respectively.

The intermediate valve position (home position) of the control valve 2 corresponds to the stop state of the actuator 3. In the middle valve position, all oil ports of the control valve 2 are not communicated with each other.

The first valve position (left valve position in the figure) of the control valve 2 corresponds to the forward state of the actuator 3. In the first valve position, the working oil port A is communicated with the oil inlet P, and the working oil port B is communicated with the oil return port T2. The output hydraulic oil of the pump 1 pushes the actuator 3 to do forward motion.

Note that, in order to increase the advancing speed of the actuator 3, in the first valve position of the control valve 2, the working port B communicates with the working port a through a check valve that allows hydraulic oil to flow from the working port B to the working port a and does not allow hydraulic oil to flow from the working port a to the working port B. The check valve is opened when the pressure of the working oil port B is higher than that of the working oil port A, so that part of hydraulic oil of the working oil port B directly enters the working oil port A, and hydraulic regeneration is realized.

The second valve position (right valve position in the drawing) of the control valve 2 corresponds to the reverse state of the actuator 3. In the second valve position, the working oil port B is communicated with the oil inlet P, and the working oil port A is communicated with the oil return port T1. The output hydraulic oil of the pump 1 pushes the actuator 3 to do a backward movement.

It will be appreciated that the two return ports T1, T2 of the control valve 2 may be in communication via an internal oil passage, so that the control valve 2 has only one return port. Thus, the control valve 2 is configured as a three-position, four-way proportional reversing valve.

The first and second valve positions may be referred to as the working valve positions of the control valve 2. Each working position is achieved by pilot pressure received at a respective control port on the control valve 2. At each operating valve position, the pilot pressure on the corresponding control port determines the spool position of the control valve 2, which determines the opening of the control valve 2, which determines the flow rate of the hydraulic oil output by the pump 1 to the actuator 3, thereby controlling the action (direction, speed, etc.) of the actuator 3.

Fig. 2 shows an exemplary configuration of the valve body 5 and the valve element 6 of the control valve 2.

The valve body 5 has a valve chamber formed therein in which the spool 6 is axially slidably disposed and is equipped with the above-described oil ports. Oil grooves (undercut grooves) 5T1, 5A, 5P, 5B, 5T2 are formed in the valve body 5 in this order facing the valve chamber in the axial direction from the first side (left side in fig. 2) to the second side (right side in fig. 2), and communicate with the oil ports T1, A, P, B, T2, respectively.

On the other hand, two oil grooves (undercut grooves) are formed in the valve element 6, and divide the valve element 6 into a first control section (oil return control section) 6a, a second control section (oil inlet control section) 6b, and a third control section (oil return control section) 6c that are sequentially distributed from the first side to the second side in the axial direction, wherein a first oil groove section 6d is formed between the first control section 6a and the second control section 6b, and a second oil groove section 6e is formed between the second control section 6b and the third control section 6 c.

In the intermediate valve position of the control valve 2, the first control section 6a, the second control section 6B, the third control section 6c face and close the oil grooves 5T1, 5P, 5T2, respectively, and the first oil groove section 6d, the second oil groove section 6e face the oil grooves 5A, 5B, respectively. At the moment, all the oil ports are not communicated with each other.

Although not shown in fig. 2, the check valve of the control valve 2 may be disposed within the valve body 5 of the control valve 2, or within the spool 6 of the control valve 2, or outside the valve body 5 of the control valve 2.

Referring to fig. 2 and 3, a plurality of oil inlet openings 7 are formed in the outer periphery of the second control section 6b from a first side end surface (an end surface facing the first oil groove section 6d) of the second control section 6 b. These openings 7 are distributed evenly over the circumference of the second control section 6b and extend a distance in the axial direction towards the second lateral end face of the second control section 6b (the end face facing away from the first sump section 6 d). The sum of the cross-sectional areas of the openings 7 decreases in the axial direction from the first side to the second side.

On the outer circumference of the third control section 6c, starting from the first side end face of the third control section 6c (the end face facing the second sump section 6e), a plurality of oil return openings 8 are provided. These openings 8 are distributed evenly over the circumference of the third control section 6c and extend a distance in the axial direction towards the second lateral end face of the third control section 6c (the end face facing away from the second sump section 6 e). The sum of the cross-sectional areas of the openings 8 decreases in the axial direction from the first side to the second side.

When the actuator 3 is required to advance, the control valve 2 needs to be placed in the first valve position. At this time, by applying pilot pressure to the first side control port of the control valve 2, the second side control port has no pilot pressure, and the spool 6 axially slides in the first side to second side direction in the valve body 5.

After the valve core 6 moves a distance toward the second side in the axial direction, as shown in fig. 4, the oil inlet opening and the oil return opening are simultaneously or sequentially communicated with the oil grooves 5P, 5T2, so as to communicate the oil groove 5A with the oil groove 5P (i.e., to communicate the oil port a with the oil port P), and the oil groove 5B with the oil groove 5T2 (i.e., to communicate the oil port B with the oil port T2). Thus, the hydraulic oil of the pump 1 starts to be supplied to the actuator 3 through the control valve 2, and the actuator 3 starts the forward movement.

Note that communication may be established between the oil grooves 5A and 5P and between the oil groove 5B and the oil groove 5T2 at the same time; it is also possible to have the communication between the oil groove 5B and the oil groove 5T2 established first and the communication between the oil groove 5A and the oil groove 5P established later, so that the order of establishing the communication may be advantageous for some applications. It will be appreciated that this order of establishing communication can be achieved by setting the axial positions and lengths of the oil and oil return openings.

As the spool 6 moves further axially toward the second side, as shown in fig. 5, the oil inlet opening defines an increased oil inlet flow area between the oil groove 5A and the oil groove 5P, and the oil return opening defines an increased oil return flow area between the oil groove 5B and the oil groove 5T 2. Due to the resistance effect of the return spring of the control valve 2 on the pilot pressure, the final axial position of the valve core 6 is determined by the pilot pressure on the first side of the control valve 2, and the oil inlet and return flow areas (opening degrees) of the control valve 2 are also determined.

For low load operation of the actuator 3, the pilot pressure on the first side of the control valve 2 may be set such that the spool 6 establishes communication between the oil sump 5B and the oil sump 5T2 only through the small oil return flow area defined by the oil return openings. In this case, the opening degree of the control valve 2 is small, a high back pressure can be established in the oil groove 5B, i.e., the oil port B, and a large part of the hydraulic oil is returned from the oil port B to the oil port a through the check valve, i.e., hydraulic regeneration is realized, so that the actuator 3 can advance quickly.

For high load operation of the actuator 3, the pilot pressure on the first side of the control valve 2 may be increased such that the larger return flow area defined by the spool 6 through each return opening establishes communication between the oil sump 5B and the oil sump 5T 2. In this case, the opening degree of the control valve 2 is abruptly increased with respect to the opening degree at the time of the low load operation, so that the actuator 3 can obtain a larger hydraulic oil supply, generate a high forward power, and realize the high load operation, in which the hydraulic pressure is not normally regenerated.

When the actuator 3 needs to be retracted, the control valve 2 needs to be placed in the second valve position. At this time, by applying pilot pressure to the second side control port of the control valve 2, the first side control port has no pilot pressure, and the spool 6 axially slides in the second side to first side direction in the valve body 5. Finally, the oil groove 5T1 is communicated with the oil groove 5A through the first oil groove section 6d, i.e. communication is established between the oil port a and the oil port T1, and the oil groove 5B is communicated with the oil groove 5P through the second oil groove section 6e, i.e. communication is established between the oil port B and the oil port P.

As mentioned above, the total cross-section of the oil inlet opening and the oil return opening in the valve element 6 decreases axially in the direction from the first side to the second side. There are a number of ways to achieve this.

For example, the oil inlet openings on the second control section 6b according to one possible embodiment are illustrated in a cylindrically expanded view in fig. 6, comprising two groups of oil inlet openings which are evenly distributed in the circumferential direction, each group comprising one first type of oil inlet opening 7a and one second type of oil inlet opening 7b, respectively.

Each opening 7a includes a semicircular first opening portion 7a1 facing the first side end surface of the second control section 6b, a second opening portion 7a2 axially engaged with the first opening portion 7a1 and having a circumferential dimension smaller than the diameter of the first opening portion 7a1, and a third opening portion 7a3 axially engaged with the second opening portion 7a2 and having a circumferential dimension smaller than the second opening portion 7a 2.

Each opening 7b includes a semicircular first opening portion 7b1 facing the first side end surface of the second control section 6b, and a second opening portion 7b2 axially engaged with the first opening portion 7b1 and having a circumferential dimension smaller than the diameter of the first opening portion 7b 1. The diameter and/or radial depth of the first opening portion 7b1 may be the same as or different from the first opening portion 7a1, and the circumferential width and/or radial depth and/or circumferential length of the second opening portion 7b2 may be the same as or different from the second opening portion 7a 2.

The number, shape, and position of the oil inlet openings are not limited to those shown in fig. 6, and may be appropriately designed according to specific needs.

The oil return openings in the third control section 6c according to a possible embodiment are shown in a cylindrical development in fig. 7, comprising two sets of oil return openings which are distributed alternately in the circumferential direction, each set comprising one oil return opening of the first type 8a and two oil return openings of the second type 8 b.

Each of the openings 8a includes a circular arc-shaped (minor arc-shaped) first opening portion 8a1 facing the first side end surface of the third control section 6c, a second opening portion 8a2 axially engaged with the first opening portion 8a1 and having a circumferential dimension smaller than the diameter of the first opening portion 8a1, a third opening portion 8a3 axially engaged with the second opening portion 8a2 and having a circumferential dimension smaller than the second opening portion 8a2, and a fourth opening portion 8a4 axially engaged with the third opening portion 8a3 and extending and gradually narrowing toward the second side.

Each opening 8b is a circular arc (minor arc) opening portion facing the first side end face of the third control section 6 c. The diameter and/or radial depth and/or circumferential dimension of the opening 8b may be the same as or different from the first opening portion 8a 1.

The number, shape and position of the oil return openings are not limited to those shown in fig. 7, and may be appropriately designed according to specific needs.

The parts of each oil return opening 8 are shaped and dimensioned such that there is a steep change in the oil return flow area defined by the oil return opening as the spool is displaced.

Specifically, as shown in fig. 7, it is assumed that the corresponding effective spool displacement at the second side farthest end of the oil return opening is 0%, and the corresponding effective spool displacement at the first side end of the oil return opening is 100%. The curve in fig. 8 schematically shows the relationship between the return flow area and the effective spool displacement. In fig. 8, the horizontal axis represents the effective spool displacement D, and the vertical axis represents the return flow area S. Due to the shape and size of each opening 8a, 8b, the return oil flow area increases slowly from 0% of the effective spool displacement up to the switching point (within 70-90% of the effective spool displacement, e.g. about 85%), which section may be referred to as the first displacement zone. From the switching point to 100% of the effective spool displacement, the return flow area increases rapidly, i.e. steeply, which section may be referred to as the second displacement zone.

The steep increase referred to herein may be defined as the return flow area formed at 100% effective spool displacement being at least 3 times, preferably 5 times or more, the return flow area formed at the switching point.

The return flow area defined by the return opening is small relative to the flow area established by the second sump section 6e between the sump 5B and the sump 5P throughout the effective spool displacement, thus enabling a high back pressure to be generated in the sump 5B, port B. Furthermore, in the first displacement zone, the oil return flow area defined by the oil return opening may be set to be always smaller than the oil inlet flow area defined by the oil inlet opening, so that in the first displacement zone, it is easier to establish a back pressure in the oil port B.

The first displacement region is used for low load operation of the actuator 3 and the second displacement region is used for high load operation of the actuator 3. The load of the actuator 3 can be detected by a force sensor provided for the actuator 3, an output oil pressure sensor of the pump 1, or the like, and the displacement of the spool 6 can be controlled by adjusting the pilot pressure of the control valve 2 based on the detected load of the actuator 3 or based on a command manually input by an operator through an input element, thereby placing the spool 6 in the first displacement region or the second displacement region. In this way, for low load operation, the control valve 2 may build up back pressure and enable hydraulic regeneration such that the actuator 3 is rapidly advanced. For high load operation, the control valve 2 may enable the supply of high hydraulic pressure to the actuator.

The oil return opening can be designed by the person skilled in the art such that the above-mentioned steep increase in displacement zone occurs.

Furthermore, although the spool positions of the control valves 2 described above are pilot-controlled, the spool positions of the control valves 2 may also be electrically controlled, i.e. the spool positions of the control valves 2 are controlled by the voltages supplied to the respective electromagnets. The control valve 2 can thus be either a pilot-controlled proportional valve, an electronically controlled proportional valve or an electro-hydraulically controlled proportional valve.

In summary, the present application discloses a proportional valve for a hydraulic system having a steep change in opening in a first valve position relative to a spool position, thereby accommodating different load levels. With a simple spool design, high back pressure can be established and hydraulic regeneration can be achieved during low load operation, thereby achieving rapid low load operation. Also, in the high load operation, high driving power can be provided.

Although the present application has been described herein with reference to specific exemplary embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims (10)

1. A proportional valve for regeneration function, comprising:

the valve body (5) is provided with an oil inlet (P), an oil return port (T), a first working oil port (A) and a second working oil port (B); and

the valve core (6) is axially slidably arranged in the valve body, a first oil return control section (6a), a first oil groove section (6d), an oil inlet control section (6B), a second oil groove section (6e) and a second oil return control section (6c) are sequentially arranged on the valve core from the first side to the second side in the axial direction, a first valve position of the proportional valve is realized by moving the valve core from the first side to the second side in the axial direction, a first working oil port (A) is communicated with the oil inlet (P) at the first valve position, and a second working oil port (B) is communicated with the oil return port (T);

the oil return control device is characterized in that an oil return opening is formed in the circumferential surface of the second oil return control section (6c) from the first side end surface facing the second oil groove section (6e), communication is established between the second working oil port (B) and the oil return port (T) only through the oil return opening at the first valve position, and the total cross-sectional area, which is defined by the oil return opening and is perpendicular to the axial direction, is reduced along the axial direction from the first side to the second side;

the shape and size of the oil return opening are set such that an oil return flow area amplification switching point exists within an effective valve core displacement range defined by the axial length of the oil return opening, the oil return flow area at the 100% effective valve core displacement position is at least 3 times of the oil return flow area at the switching point, and the switching point is located within 70% -90% effective valve core displacement.

2. The proportional valve for regeneration of claim 1, wherein an oil return flow area at 100% effective spool displacement is greater than 5 times an oil return flow area at the switching point.

3. The proportional valve for regeneration function of claim 1, wherein the switch point is about 85% effective spool displacement.

4. Proportional valve for regeneration functions according to claim 1, characterized in that the oil return opening comprises a plurality of oil return openings distributed evenly in the circumferential direction over the circumference of the second oil return control section (6c), the cross-sectional area of each oil return opening decreasing continuously or in stages in the direction from the first side to the second side.

5. Proportional valve for regenerative function, according to claim 4, characterized in that said plurality of oil return openings comprises at least two sets of oil return openings distributed in circumferential direction, each set of oil return openings comprising at least one oil return opening of a first type and at least one oil return opening of a second type, the first type of oil return opening having an axial length different from the second type of oil return opening and the first type of oil return opening having a circumferential dimension and/or a radial depth at each axial position which is the same or different from the second type of oil return opening.

6. The proportioning valve for regeneration function of claim 5 wherein each first type oil return opening includes a circular arc shaped opening portion and at least one additional opening portion extending from the circular arc shaped opening portion to the second side and having a circumferential width less than the circular arc shaped opening portion;

the second type oil return openings in each group include two or more second type oil return openings, each second type oil return opening being formed by a circular arc-shaped opening portion.

7. Proportional valve for regeneration function according to any of claims 1-6, characterized in that the peripheral surface of the oil inlet control section (6b) is formed with an oil inlet opening extending towards the second side from its first side end surface facing the first sump section (6d), which oil inlet opening is used for establishing communication between the first working oil port (A) and the oil inlet (P) in the first valve position, and the oil return flow area defined by the oil return opening decreases in the direction from the first side towards the second side.

8. Proportional valve for regenerative function according to claim 7, characterized in that the oil inlet openings comprise a plurality of oil inlet openings distributed evenly in circumferential direction over the circumference of the oil inlet control section (6b), the cross-sectional area of each oil inlet opening decreasing continuously or in stages in the direction from the first side to the second side.

9. The proportional valve for regeneration of a function of claim 8, wherein the plurality of oil inlet openings comprises at least two sets of oil inlet openings arranged alternately with each other, each set of oil inlet openings comprising at least one first type of oil inlet opening and at least one second type of oil inlet opening, the first type of oil inlet opening having an axial length different from the second type of oil inlet opening, and the first type of oil inlet opening having a circumferential dimension and/or a radial depth at each axial position that is the same as or different from the second type of oil inlet opening.

10. The proportional valve for regeneration function of any of claims 1-6, further comprising a check valve that communicates the second working port (B) with the first working port (A) in the first valve position, allowing one-way flow of hydraulic oil from the second working port (B) to the first working port (A).

Images