CN115479145A

CN115479145A - Proportional valve

Info

Publication number: CN115479145A
Application number: CN202110659356.6A
Authority: CN
Inventors: 蒋一夫; 奥拉夫埃克哈德·韦伯
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2022-12-16

Abstract

The invention relates to a proportional valve. The proportional valve comprises a hollow shell and a valve body installed in the shell, a valve cavity used for containing fluid is formed between the inner wall of the shell and the valve body, and the shell is provided with an inlet, a first outlet and a second outlet which are respectively communicated with the valve cavity. Wherein the first outlet and the second outlet are axially opposed, the valve body being axially movable between a first position closing the first outlet and a second position closing the second outlet, such that the flow of fluid out of the valve chamber is distributed between the first outlet and the second outlet depending on the axial position of the valve body. The proportional valve has a good proportional control effect.

Description

Proportional valve

Technical Field

The invention relates to the technical field of hydraulic control. In particular, the present invention relates to a proportional valve having two outlets.

Background

With the development of new energy vehicles, the market demand for efficient hybrid power systems is increasing. In this context, thermal management systems will become more important, both for conventional pure internal combustion engine power systems and for newer hybrid power systems. Currently, it is often necessary to provide a series of Thermal Management Modules (TMMs) with rotary ball valves in the engine's subsystems. A typical construction of a rotary ball valve used in existing thermal management modules can be found, for example, in patent documents CN 206816348U and the like.

However, various hydraulic valves of the prior art have been unable to meet the increasing demands on the performance of thermal management modules at present. First, prior art hydraulic valves typically only switch between a fixed open position and a closed position, and do not provide proportional control of flow. Secondly, hydraulic valves in the prior art often have no pilot function or only a one-way pilot function, which makes the valve body often in an unstable state when opened from the closed position. Further, these prior art hydraulic valves typically employ a solenoid as an actuating mechanism for the valve body, the solenoid being separate from contact with the valve body or piston in the valve chamber, and thus the position of the valve body cannot be determined by the solenoid.

Disclosure of Invention

Therefore, the technical problem to be solved by the present invention is to provide an improved proportional valve.

The above technical problem is solved by a proportional valve according to the present invention. The proportional valve comprises a hollow shell and a valve body installed in the shell, a valve cavity used for containing fluid is formed between the inner wall of the shell and the valve body, and the shell is provided with an inlet, a first outlet and a second outlet which are respectively communicated with the valve cavity. Wherein the first outlet and the second outlet are axially opposed, the valve body being axially movable between a first position closing the first outlet and a second position closing the second outlet, such that the flow of fluid out of the valve chamber is distributed between the first outlet and the second outlet depending on the axial position of the valve body. By axially moving the valve body between the two outlets, the flow of fluid from the two outlets out of the valve chamber can be proportionally distributed, thereby conveniently achieving a proportional control function. Meanwhile, the valve body is abutted against the outlets at two axial ends along the axial direction, so that the extrusion force for forming sealing contact between the valve body and the shell is basically vertical to the outlets, and a good sealing effect is ensured.

According to a preferred embodiment of the invention, the proportional valve may further comprise a connecting rod passing through the housing in the axial direction and an actuator for actuating the valve body, the valve body and the connecting rod may be relatively fixed at least in the axial direction, the actuator axially abuts against the connecting rod and is capable of driving the valve body to move in the axial direction via the connecting rod. The axial position of the valve body relative to the valve chamber can be controlled by an actuator to achieve a desired flow distribution ratio. The actuator may be, for example, a solenoid mechanism, but may be other possible actuating mechanisms, such as various known pneumatic, hydraulic, mechanical, or electromagnetic actuating mechanisms.

According to another preferred embodiment of the present invention, the proportional valve may further include an elastic member axially abutted between the valve body and the housing, the elastic member being capable of applying an elastic restoring force to the valve body axially opposite to the actuating force direction of the actuator. When the actuation force is provided by a solenoid or the like, the actuation force is typically applied to the valve body in only a single direction. In this case, the axial force for driving the valve body to move is provided by the resultant force of the actuating mechanism and the elastic restoring force of the elastic member, and the axial position of the valve body can be changed by controlling the magnitude of the actuating force of the actuating mechanism.

According to another preferred embodiment of the present invention, the proportional valve may further include a pilot chamber formed in the housing and a pilot piston axially movably installed in the pilot chamber, the pilot piston may be at least axially relatively fixed with the connecting rod, and the pilot piston may axially divide the pilot chamber into two opposite half chambers. Wherein the housing and the pilot piston may have a plurality of hydraulic passages, respectively, and the hydraulic passages of the housing and the pilot piston may be capable of respectively communicating or disconnecting each of the half chambers with one of the valve chamber, the first outlet, and the second outlet, based on an axial position of the pilot piston with respect to the pilot chamber. Wherein, when the valve body is located within a predetermined range from the first outlet and/or the second outlet in the axial direction, the housing and the pilot piston communicate one of the two half-chambers with the valve chamber and the other with the respective first outlet and/or the second outlet, so that the pilot piston is subjected to a hydraulic pressure difference in a direction opposite to that of the valve body. The valve body is at an axial position within a predetermined range, meaning that the valve body is close to, or even has contacted, the first outlet or the second outlet. At this point, the outlet port may be partially or completely closed by the valve body, and thus the liquid pressure inside the outlet port (including the flow passage extending from the outlet port) is significantly less than the liquid pressure in the valve chamber, thereby subjecting the valve body to a significant hydraulic pressure differential. Under the effect of such a hydraulic pressure difference, the axial movement of the valve body may enter an unstable state and be difficult to open from the closed state. By communicating the half chambers on both sides of the pilot piston with the valve chamber and the outlet close to the valve body, respectively, a corresponding hydraulic pressure difference can also be generated on the pilot piston. The axial relative positional relationship of the valve chamber and the half chamber communicated with the outlet port close to the valve body is opposite to the axial relative positional relationship of the valve chamber and the outlet port, so that the hydraulic pressure difference acting on the pilot piston is opposite to the hydraulic pressure difference acting on the valve body. Thus, the pilot piston connected to the connecting rod may at least partly counteract the hydraulic pressure difference acting on the valve body. This enables the valve body to remain stable in the region close to the outlet and to be easily opened from the closed state.

According to another preferred embodiment of the invention, the housing and the pilot piston may communicate both cavity halves simultaneously with the valve cavity when the valve body is located in a region outside the predetermined range between the first position and the second position. This means that no or no significant difference in hydraulic pressure is generated on both sides of the pilot piston when the valve body is located in the middle area remote from the outlet. At this time, the pilot action of the pilot piston is deactivated, and the valve body can be axially moved only by the actuating force of the actuator and possibly the elastic force of the elastic member.

According to a further preferred embodiment of the invention, the opening of the hydraulic passage of the housing to the valve chamber can be located in a region adjacent to the sealing surface for the respective first outlet and/or second outlet. When the valve body moves in a region near a certain outlet, the liquid pressure around the outlet tends to be in an unstable fluctuating state, and therefore, the hydraulic pressure difference to which the valve body is subjected may also fluctuate. By conducting the fluid from around the respective outlet opening into the half-chamber on the side of the pilot piston, the hydraulic pressure difference experienced by the pilot piston can be kept as synchronously as possible with the valve body, which contributes to a more stable pilot effect.

According to another preferred embodiment of the invention, the actuator, the pilot piston and the valve body may be distributed in axial direction. Preferably, the connecting rod may axially pass through the pilot piston and/or the valve body. The arrangement mode can conveniently realize the connection and fixation of the connecting rod, the pilot piston and the valve body.

According to another preferred embodiment of the invention, the connecting rod may cooperate with the housing to guide the axial movement of the valve body. Thereby, the positioning of the valve body in the radial direction with respect to the housing may also be defined by the connecting rod.

According to a further preferred embodiment of the invention, the end of the valve body for closing the first outlet and/or the end for closing the second outlet may have a radial dimension which decreases progressively in the axial direction towards the tip, and the inner wall of the housing may have a shape corresponding to the respective end of the valve body in the region around the first outlet and/or the second outlet. Thus, the end of the valve body may be formed, for example, as a cone or as a half of an oval, shuttle or olive shape or the like. This makes the valve body less resistant to the fluid in the valve chamber when moving axially inside the housing, thereby facilitating a stable movement of the valve body.

Drawings

The invention is further described below with reference to the accompanying drawings. Identical reference numbers in the figures denote functionally identical elements. Wherein:

FIG. 1a shows a cross-sectional view of a proportional valve according to an embodiment of the present invention in a first position;

FIG. 1b shows a cross-sectional view of a proportional valve according to an embodiment of the invention in an intermediate position;

FIG. 1c shows a cross-sectional view of a proportional valve according to an embodiment of the invention in a second position; and

FIG. 2 shows a flow control graph of a proportional valve according to an embodiment of the invention.

Detailed Description

Specific embodiments of a proportional valve according to the present invention will be described below with reference to the accompanying drawings. The following detailed description and drawings are included to illustrate the principles of the invention, which is not to be limited to the preferred embodiments described, but is to be defined by the appended claims.

According to an embodiment of the invention, a proportioning valve is provided having two outlets, which is capable of controlling the division of the outgoing flow between the two outlets. The proportional valve can be used in various hydraulic control devices requiring proportional control, and is particularly suitable for being applied to a thermal management module of a motor vehicle to replace a traditional rotary ball valve.

Fig. 1a to 1c show an exemplary embodiment of a proportional valve according to the present invention. As shown in fig. 1a to 1c, the proportional valve according to the present embodiment includes a housing 1, a valve body 2, and an actuator 4. The housing 1 has a hollow interior, and the valve body 2 is mounted in the interior of the housing 1. A valve chamber 3 for containing fluid is formed between the inner wall of the inner cavity of the housing 1 and the valve body 2. The housing 1 is formed with one inlet I and two outlets, a first outlet a and a second outlet B. The first outlet a and the second outlet B are distributed in the up-down direction in the drawing, which is defined as the axial direction of the proportional valve. Thus, in the housing 1, the first outlet a and the second outlet B are axially opposed at both ends of the valve chamber 3. In the present embodiment, the inlet I is formed at substantially the axial middle on the side wall of the inner cavity, and faces in a direction substantially perpendicular to the axial direction. The direction perpendicular to the axial direction is defined here as the radial direction of the proportional valve. The position and orientation of the inlet I is here only illustrative, and in different embodiments the inlet I may also have different positions and orientations.

Inside the housing 1, the valve body 2 is axially movable by an actuator 4 between a first position closing the first outlet a and a second position closing the second outlet B, and preferably the actuator 4 can control the positioning of the valve body 2 at any axial position between the first and second positions. The fluid flowing into the valve chamber 3 from the inlet I (e.g., the coolant in the thermal management module) is diverted at both axial ends under the guidance of the valve body 2 such that a portion of the fluid flows out of the first outlet a and another portion of the fluid flows out of the second outlet B. Since the axial position of the valve body 2 determines the size of the flow path leading from the inlet I to the two outlets, the flow of fluid out of the valve chamber 3 is divided between the two outlets according to the axial position of the valve body 2, thereby achieving proportional control of the outflow of each outlet. When the valve body 2 is in the first position or the second position, the end of the valve body 2 abuts against the inner wall of the housing around the corresponding outlet, thereby forming a sealing surface, so that fluid cannot flow out of the valve chamber 3 through the outlet, and all fluid can flow out of the valve chamber 3 only through the other outlet. Preferably, a seal 7 may be installed at the end of the valve body 2. The seal 7 may be, for example, an elastic sealing ring.

In the graph shown in fig. 2, the abscissa represents the axial position S of the valve body 2, and the ordinate represents the flow rate Q at a certain inlet or outlet. Defining the second position, which closes the second outlet B, as a zero position, as shown in fig. 2, in the case of a substantially constant flow rate at the inlet I, the valve body 2 gets closer to the first outlet a, the flow rate of which gradually decreases and the flow rate of which gradually increases as the axial position S increases.

In order to reduce the fluid resistance to which the valve body 2 is subjected when it is moved axially in the housing 1, one or both of the two axial ends of the valve body 2, which close the outlet, may have a radial dimension which decreases progressively in the axial direction towards the end, i.e. towards the respective outlet, for example formed as a cone or as halves of an oval, shuttle or olive or similar shape. When both ends of the valve body 2 are symmetrically formed in such a shape, the entire valve body 2 may be formed in a complete bicone shape, an oval shape, a shuttle shape, an olive shape, or the like. The inner wall of the housing 1 may have a shape corresponding to the respective end of the valve body 2 in the area around the respective outlet, so that the valve body 2 contacts the inner wall of the housing 1 with a form fit to close the respective outlet.

In practice, the actuator 4 may preferably be a solenoid mechanism. In addition, the actuator 4 may also be implemented by other possible means, such as pneumatic, hydraulic, mechanical or electromagnetic actuating mechanisms. For example, in the case of a solenoid mechanism, the driving force applied to the valve body 2 is generally unidirectional. In this case, the elastic member 6 may be provided in the proportional valve so as to enable the valve body 2 to move bidirectionally. The elastic member 6 may be, for example, a coil spring or any other suitable type of elastic member. The elastic member 6 is axially abutted between the housing 1 and the valve body 2, and its specific axial position may be set according to a required restoring force direction, so that the direction of the elastic restoring force applied to the valve body 2 by the elastic member 6 is axially opposite to the direction of the actuating force applied by the actuator 4. In this case, the axial movement of the valve body 2 can be controlled by merely changing the magnitude of the actuation force exerted by the actuator 4 without changing the direction of the actuation force. For example, in the illustrated example, the actuator 4 applies a unidirectional actuation force in the axial direction toward the second outlet B, and accordingly, the elastic member 6 abuts between the housing 1 and the valve body 2 at an end near the second outlet B, so that the elastic restoring force applied to the valve body 2 by the elastic member 6 is directed in the axial direction toward the first outlet a. In other embodiments, the resilient member 6 may also be omitted if the actuator 4 itself is capable of controlling the bi-directional movement of the valve body 2.

The proportional valve may also comprise a connecting rod 5 extending in axial direction. The actuator 4 abuts (for example by means of an actuating ram) in the axial direction against a connecting rod 5, which connecting rod 5 is connected relatively fixedly with the valve body 2 at least in the axial direction. The actuator 4 and the connecting rod 5 are constantly kept in stable mutual abutment in the normal operating state of the proportional valve, so that the actuator 4 can drive the valve body 2 via the connecting rod 4 to move in the axial direction and accurately control the axial position of the valve body 2. In other words, the exact axial position of the valve body 2 can be determined by the position of the actuator 4 itself. In this case, if the axial position of the valve body 2 is continuously adjustable under the control of the actuator 4, the flow ratio of the two outlets is also continuously adjustable. Preferably, an elastic member 6 in the form of a coil spring may be wound around the link 5.

In a preferred embodiment, the actuator 4 may be mounted at an axial end outside the housing 1 and may be arranged coaxially with the link 5. The connecting rod 5 may pass through the valve body 2 and the housing 1 to abut the actuator 4. The connecting rod 5 may also preferably be arranged coaxially with the two outlets A, B. Preferably, the connecting rod 5 can also cooperate with the housing 1 to guide the axial movement of the valve body 2. In particular, the valve body 2 and the connecting rod 5 may also be fixed relative to each other in the radial direction, and the connecting rod 5 may snugly pass through a guide hole in the housing 1. Further, the axial movement of the valve body 2 may be guided by the engagement of the valve body 2 with the housing 1.

In a preferred embodiment, the proportional valve according to the invention may also have a pilot function. The pilot function is provided by a pilot piston 8 mounted in a pilot chamber 9. The pilot chamber 9 is a straight cylindrical cavity extending axially in the housing 1, which is independent of the housing interior for mounting the valve body 2. The pilot piston 8 is axially movable in a pilot chamber 9. The pilot piston 8 divides the pilot chamber 9 in the axial direction into two opposite half-chambers. The inner wall of the pilot chamber 9 can be formed directly by the inner wall of another cavity inside the housing 1 or by an additional sleeve mounted in this cavity. The pilot piston 8 is at least axially relatively fixed with the connecting rod 5, preferably they are completely fixed together. Thus, the axial movement of the pilot piston 8 in the pilot chamber 9 is synchronized with the axial movement of the valve body 2 in the valve chamber 3.

A plurality of hydraulic passages are formed in the housing 1 and the pilot piston 8, respectively. The hydraulic passage in the housing 1 includes an inlet passage PI, a first outlet passage PA, and a second outlet passage PB that are independent of each other. The inlet channel PI extends from the valve chamber 3 to the pilot chamber 9. The first outlet passage PA extends from inside the first outlet a (e.g. from the inner wall of the outflow passage connecting the first outlet a) to the pilot chamber 9. The second outlet channel PB extends from inside the second outlet B (e.g. from the inner wall of the outflow channel connecting the second outlet B) to the pilot chamber 9.

Each hydraulic channel in the pilot piston 8 extends from the outer side wall of the pilot piston 8 to one of the two half-chambers, respectively. The openings of the hydraulic channel in the pilot piston 8 on the outer side wall have different axial and/or circumferential positions. Therefore, when the pilot piston 8 moves axially with the valve body 2, the inlet passage PI, the first outlet passage PA, and the second outlet passage PB may be respectively communicated with or disconnected from different hydraulic passages in the pilot piston 8 based on the axial position of the pilot piston 8. When one hydraulic passage in the housing 1 communicates with one hydraulic passage in the pilot piston 8, one half chamber can communicate with one of the valve chamber 3, the first outlet a, and the second outlet B.

When the valve body 2 is axially close to or even contacts one of the outlets a or B, i.e., when the valve body 2 is axially located within a predetermined range from the outlet, the inlet passage PI communicates with one of the hydraulic passages of the pilot piston 8, and at the same time, the outlet passage PA or PB communicating with the outlet communicates with the other hydraulic passage of the pilot piston 8. The two hydraulic passages in the pilot piston 8 communicate with different half-chambers, respectively, which makes the valve chamber 3 and the outlet close to the valve body 2 communicate with different half-chambers, respectively. The axial relative positional relationship between the valve chamber 3 and the two half-chambers with which the outlet communicates is opposite to the axial relative positional relationship between the valve chamber 3 and the outlet. For example, in fig. 1a, the valve body 2 is close to the first outlet a, and the valve chamber 3 is located below the first outlet a, the valve chamber 3 communicates with a half chamber above the pilot piston 8, and the first outlet a communicates with a half chamber below the pilot piston 8. Whereas in fig. 1c the valve body 2 is close to the second outlet B and the valve chamber 3 is located above the second outlet B, the valve chamber 3 communicates with the half chamber below the pilot piston 8 and the second outlet B communicates with the half chamber above the pilot piston 8.

When the valve body 2 is located near a certain outlet, a hydraulic pressure difference will be created between the valve chamber 3 and the inside of the outlet, since the flow of fluid from the valve chamber 3 to the outlet is obstructed. This difference in hydraulic pressure will exert an additional axial force on the valve body 3 towards the outlet, thereby affecting the control of the axial position of the valve body 2 by the actuator 4. However, at this time, a hydraulic pressure difference is also generated in the pilot piston 8, and the direction of the hydraulic pressure difference acting on the pilot piston 8 is axially opposite to the direction of the hydraulic pressure difference acting on the valve body 2. Since the pilot piston 8 and the valve body 2 are fixedly connected to each other in the axial direction via the connecting rod 5, the hydraulic pressure difference experienced by the two can at least partially cancel each other out. This makes the force to which the valve body 2 is subjected at an axial position close to the outlet more stable, in particular the valve body 2 is susceptible to opening from a closed state, the so-called pilot function.

Further, when the valve body 2 is located near a certain outlet, the fluid flow near the outlet tends to be unstable, thereby generating a fluctuating hydraulic pressure difference. To better compensate for this difference in liquid pressure, the opening of the inlet channel PI to the valve chamber 3 can be located in the region adjacent to the sealing surface for the outlet, i.e. on the inner wall around the outside of the outlet. This causes the liquid pressure in the half-chamber communicating with the valve chamber 3 to fluctuate as well, so that the dynamic hydraulic pressure difference to which the valve body 2 is subjected can be compensated for synchronously. In this case, in order to obtain the effect of dynamic compensation at both axial positions of the valve body 2, two separate inlet channels PI may preferably be provided. When the valve body 2 is located at one axial end, the respective half-chamber in the pilot chamber 9 communicates with the valve chamber 3 around the outlet opening only through one of the corresponding inlet passages PI. However, it is also possible, depending on requirements, to provide only one inlet passage PI which communicates the respective half-chamber with the valve chamber 3 at both end positions of the valve body 2.

In a preferred embodiment, as shown in fig. 1b, when the valve body 2 is located in an intermediate region axially remote from the two outlets, i.e. in a region between the first and second positions outside the above-mentioned predetermined range, the valve body 2 itself is not subjected to a significant hydraulic pressure difference, so that the pilot function of the pilot piston 8 can be deactivated. In particular, when the valve body 2 is located in an intermediate zone axially distant from the two outlets, the hydraulic passages communicating with each other in the housing 1 and the pilot piston 8 can communicate the two half-chambers with the same zone, for example both half-chambers communicate with the valve chamber 3 at the same time or with the inside of the same outlet, or the hydraulic passages in the housing 1 and the pilot piston 8 can also be completely interrupted. This results in substantially no hydraulic pressure difference across the pilot piston 8 and thus avoids hindering the normal axial movement of the valve body 2. Of these, simultaneous communication of the two half-chambers with the valve chamber 3 is a preferred design, since the respective volumes of the two half-chambers vary with the axial position of the pilot piston 8 in the pilot chamber 9, when fluid can flow freely between the half-chambers and the valve chamber 3, thus avoiding obstruction of the axial movement of the pilot piston 8.

Although in the above-described embodiment, the proportional valve is schematically described as having the pilot function at both end positions of the valve body 2, this is not restrictive. The proportional valve may also have a pilot function at only one end position. In this case, only one of the two outlet passages corresponding to the outlet of the end portion may be provided while the other outlet passage is omitted.

In a preferred embodiment, the pilot piston 8 can also be distributed axially with the valve body 2, the actuator 4, in particular also coaxially. The connecting rod 5 can pass, in particular coaxially, through the pilot piston 8 and the valve body 2, connecting them together, so that the pilot piston 8 and the valve body 2 can be kept in synchronous axial movement. In the illustrated embodiment, the pilot piston 8 is located axially between the valve chamber 3 and the actuator 4. This is only illustrative and the pilot piston 8 may have other positions, for example, the pilot piston 8 and the actuator 4 may be located at opposite ends of the valve chamber 3 in the axial direction.

A proportional valve according to an embodiment of the present invention is suitable, for example, for use in a thermal management system of a motor vehicle, where such a proportional valve may replace a conventional rotary ball valve in a thermal management system to control the flow of coolant. But this is not restrictive and the proportional valve can also be applied to other devices requiring proportional control of the fluid.

Although possible embodiments have been described by way of example in the above description, it should be understood that numerous embodiment variations still exist through all known and further combinations of technical features and embodiments that are easily imaginable to the skilled person. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. From the foregoing description, one of ordinary skill in the art will more particularly provide a technical guide to convert at least one exemplary embodiment, wherein various changes may be made, particularly in matters of function and structure of the components described, without departing from the scope of the following claims.

List of reference numerals

1. Shell body

2. Valve body

3. Valve cavity

4. Actuator

5. Connecting rod

6. Elastic piece

7. Sealing element

8. Pilot piston

9. Pilot cavity

A first outlet

B second outlet

I inlet

PA first outlet channel

PB second outlet channel

PI inlet channel

S axial position

Q flow

Claims

1. A proportional valve comprising a hollow housing (1) and a valve body (2) mounted in the housing (1), a valve chamber (3) for containing a fluid being formed between an inner wall of the housing (1) and the valve body (2), the housing (1) having an inlet (I), a first outlet (A) and a second outlet (B) communicating with the valve chamber (3), respectively,

it is characterized in that the preparation method is characterized in that,

the first outlet (A) and the second outlet (B) are axially opposite, the valve body (2) being axially movable between a first position closing the first outlet (A) and a second position closing the second outlet (B) such that the flow of fluid out of the valve chamber (3) is distributed between the first outlet (A) and the second outlet (B) depending on the axial position of the valve body (2).

2. Proportional valve according to claim 1, characterized in that it further comprises a connecting rod (5) passing through the housing (1) in the axial direction and an actuator (4) for actuating the valve body (2), the valve body (2) being relatively fixed with the connecting rod (5) at least in the axial direction, the actuator (4) axially abutting the connecting rod (5) and being able to drive the valve body (2) in the axial direction via the connecting rod (5).

3. Proportional valve according to claim 2, characterized in that it further comprises an elastic element (6) axially abutting between the valve body (2) and the housing (1), said elastic element (6) being able to exert an elastic return force on the valve body (2) axially opposite to the actuation force direction of the actuator (4).

4. Proportional valve according to claim 2, characterized in that it further comprises a pilot chamber (9) formed in the housing (1) and a pilot piston (8) mounted axially movably in the pilot chamber (9), the pilot piston (8) being at least axially relatively fixed with respect to the connecting rod (5), the pilot piston (8) axially dividing the pilot chamber (9) into two opposite half-chambers,

wherein the housing (1) and the pilot piston (8) each have a plurality of hydraulic channels, the hydraulic channels of the housing (1) and the pilot piston (8) being capable of connecting or disconnecting each half-chamber to one of the valve chamber (3), the first outlet (A) and the second outlet (B), respectively, based on the axial position of the pilot piston (8) relative to the pilot chamber (9),

wherein, when the valve body (2) is axially located within a predetermined range from the first outlet (A) and/or the second outlet (B), the housing (1) and the pilot piston (8) communicate one of the two half-chambers with the valve chamber (3) and the other with the respective first outlet (A) and/or second outlet (B) such that the pilot piston (8) is subjected to a hydraulic pressure difference in a direction opposite to that of the valve body (2).

5. The proportioning valve according to claim 4 wherein the housing (1) and the pilot piston (8) communicate the two half-chambers simultaneously with the valve chamber (3) when the valve body (2) is in a region outside the predetermined range between the first and second positions.

6. The proportioning valve according to claim 4 characterized in that the opening of the hydraulic passage of the housing (1) to the valve chamber (3) is located in a region adjacent to the sealing surface for the respective first outlet (A) and/or second outlet (B).

7. Proportional valve according to claim 4, characterized in that the actuator (4), the pilot piston (8) and the valve body (2) are distributed axially.

8. Proportional valve according to claim 7, characterized in that the connecting rod (5) passes axially through the pilot piston (8) and/or the valve body (2).

9. Proportional valve according to claim 2, characterized in that the connecting rod (5) cooperates with the housing (1) to guide the axial movement of the valve body (2).

10. The proportional valve according to any one of claims 1 to 9, wherein the end of the valve body (2) for closing the first outlet (a) and/or the end for closing the second outlet (B) has a radial dimension that progressively decreases in the axial direction towards the tip, the inner wall of the housing (1) having, in the region around the first outlet (a) and/or the second outlet (B), a shape corresponding to the respective end of the valve body (2).