An electro-hydraulic proportional valve and a variable displacement oil pump

Abstract

The present invention provides an electro-hydraulic proportional valve, which is controlled by PWM. When the PWM duty ratio of the proportional valve is at any ratio between 0% and 100%, the opening of the proportional valve depends on the hydraulic pressure entering the proportional valve, and the magnitude of the PWM duty ratio is inversely proportional to the magnitude of the hydraulic pressure. The present invention also provides a variable displacement oil pump, including a pump body, a variable slider, a variable spring and a pressure feedback chamber. The on-off of the oil inlet oil circuit of the pressure feedback chamber is controlled by the electro-hydraulic proportional valve provided by the present invention, and the opening pressure of the electro-hydraulic proportional valve is greater than the pressure corresponding to the maximum compression of the variable spring. Since the electro-hydraulic proportional valve can control the output pressure, the pumping pressure of the oil pump after the variable value is always at a fixed pressure value under the premise that the PWM value remains unchanged, and there is no need to require the ECU to adjust the PWM.

Description

Technical Field

[0001] The present invention relates to the field of mechanical technology, and particularly to an electro-hydraulic proportional valve and a variable displacement oil pump using the above electro-hydraulic proportional valve. Background Art

[0002] In the prior art, an electro-hydraulic proportional valve is a component in which a proportional electro-magnet inside the valve generates corresponding actions according to the input voltage signal, causing the spool of the working valve to generate displacement, changing the size of the valve port, and thus completing the output of pressure and flow rate proportional to the input voltage. The valve port can be opened to any opening degree as needed, thereby controlling the magnitude of the flow rate passing through.

[0003] For a variable displacement oil pump, it generally includes a pump body, a variable slider, a variable spring, and a pressure feedback chamber. The pressure oil from the main oil passage or the pump outlet enters the pressure feedback chamber through an oil passage, and an electro-hydraulic proportional valve is provided to control the on-off of the oil passage and the opening degree of the valve port, so that the pressure oil enters the pressure feedback chamber through the electro-hydraulic proportional valve and acts on the variable slider. When the pressure of the pressure oil reaches the set pressure value, it can push the variable slider to move eccentrically against the pre-tightening force of the variable spring, thereby reducing the displacement output of the oil pump.

[0004] Figure 1 It is the rotational speed characteristic diagram of an oil pump using a traditional electro-hydraulic proportional valve. In the diagram, the pressure curves of 10 different PWM ratios are plotted. After the oil pump reaches variable displacement, as the rotational speed of the oil pump increases, the PWM pressure curves, especially those close to 100% PWM, will also gradually increase. At this time, it is required that the ECU adjusts the PWM, and the adjustment requires time to respond. Microscopically, the pressure does not meet the current demand.

[0005] The reason for this upward trend of the pressure curve is as follows:

[0006] 1) When the duty ratio of the traditional electro-hydraulic proportional valve is 100% PWM or close to 100% PWM, the P port and the A port of the proportional valve are completely connected, and the output pressure is not controlled. The curve is completely determined by the variable spring.

[0007] 2) Considering the suppression of pressure fluctuations, the stiffness range of the variable spring is 6 - 10 N / mm. The spring is more difficult to compress towards the back and requires a greater pressure. Therefore, an upward trend will occur.

[0008] And the more ideal rotational speed characteristic diagram should be as Figure 2 shown, and the pressure curves of different PWM ratios should be flat, indicating that the pressure output is relatively stable. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an electro-hydraulic proportional valve capable of controlling output pressure, and a variable displacement oil pump using the electro-hydraulic proportional valve.

[0010] In order to solve the above technical problems, the technical solution of the proportional valve of the present invention is: an electro-hydraulic proportional valve, which is controlled by PWM. When the PWM duty cycle of the proportional valve is at any ratio between 0% and 100%, the opening of the proportional valve depends on the hydraulic pressure entering the proportional valve, and the size of the PWM duty cycle is inversely proportional to the size of the hydraulic pressure.

[0011] In one embodiment, the proportional valve comprises a valve body (1), a valve core, a spring and a plug, and a proportional solenoid installed at one end of the valve body, wherein the valve body is provided with a P port and an A port, and when the PWM duty cycle of the proportional valve is greater than 0% and less than or equal to 100%, the electromagnetic force and the hydraulic pressure of the proportional valve can jointly push the valve core to move to a specific position, so that the P port and the A port are in a connected state; when the PWM duty cycle of the proportional valve is 0%, the hydraulic pressure reaching the set pressure value can independently push the valve core to move to a specific position, so that the P port and the A port are in a connected state.

[0012] In one embodiment, the proportional electromagnet includes a shell, a coil, an armature push rod, and an armature limit block. The armature push rod includes a small diameter section and a large diameter section, and the connection between the small diameter section and the large diameter section forms an annular step surface; the valve body is provided with an axial stepped through hole and radial P port and A port, and a valve core, a spring and a plug are installed in the stepped through hole from right to left in sequence, and the plug is provided with an axial through hole as a T port. The cross-section of the valve core is I-shaped, including a small disc, a rod-shaped portion and a large disc, and the diameter φ1 of the large disc is greater than the diameter φ2 of the small disc, wherein a transfer chamber is formed between the rod-shaped portion and the side wall of the stepped through hole; the spring acts on the large disc of the valve core Disc, under the action of the preload force of the spring, the large disc of the valve core is located between port P and port A so that the two are in a separated state. At this time, the transfer chamber is only connected to port P; the small diameter section of the armature push rod is inserted into the stepped through hole from the right end of the valve body and contacts and cooperates with the small disc of the valve core. Under the action of electromagnetic force, the armature push rod can push the valve core to move leftward in the valve body to overcome the preload force of the spring, but the maximum distance that the armature push rod pushes the valve core to move leftward is not enough to connect port P and port A; when the oil pressure entering the transfer chamber from port P reaches the set pressure value, the oil pressure will act on the large disc and push the valve core to continue to move leftward until port P and port A are connected.

[0013] In one embodiment, a limiting surface is provided at the right end of the valve body, and the maximum distance between the step surface of the armature push rod and the limiting surface of the valve body is the maximum displacement of the armature push rod, and the maximum displacement of the armature push rod is smaller than the maximum displacement of the valve core in the valve body; when the step surface of the armature push rod contacts the limiting surface at the right end of the valve body, the PWM duty cycle of the proportional valve is 100%.

[0014] The technical solution of the present invention regarding the oil pump is as follows: A variable displacement oil pump, comprising a pump body, a variable slider, a variable spring, and a pressure feedback chamber. The on-off of the oil inlet passage of the pressure feedback chamber is controlled by the electro-hydraulic proportional valve provided by the present invention, and the opening pressure of the electro-hydraulic proportional valve is greater than the pressure corresponding to the maximum compression amount of the variable spring.

[0015] Preferably, the electro-hydraulic proportional valve is arranged on the pump body.

[0016] Preferably, the oil pump is a vane pump.

[0017] Compared with the traditional electro-hydraulic proportional valve, the electro-hydraulic proportional valve provided by the present invention no longer determines the opening and closing of the valve and the opening degree of the valve port by the ECU, but determines the opening and closing of the valve and the opening degree of the valve port by the magnitude of the hydraulic pressure entering the proportional valve. The PWM duty cycle is equivalent to providing different degrees of auxiliary force to the hydraulic pressure. Because even when the PWM duty cycle is 100%, if there is no participation of the hydraulic pressure, the P port and the A port still cannot be connected.

[0018] After combining the electro-hydraulic proportional valve provided by the present invention with the variable displacement oil pump, the control strategy and speed characteristics of the oil pump will inevitably change. Since the traditional electro-hydraulic proportional valve controls the opening and closing of the valve and the opening degree of the valve port through the ECU, it cannot limit the magnitude of the oil pressure entering the pressure feedback chamber. After the pressure oil enters the pressure feedback chamber, it only needs to overcome the pre-tightening force of the variable spring to be able to push the variable slider to move. The stiffness range of the variable spring is 6 - 10 N / mm, and the initial compression force required is relatively small. It becomes more difficult to compress later and requires a greater pressure. Therefore, the pump-out pressure of the oil pump will increase with the increase in speed. However, the electro-hydraulic proportional valve provided by the present invention needs to be opened by the hydraulic pressure. In this way, the minimum opening pressure of the electro-hydraulic proportional valve can be set to be greater than the pressure corresponding to the maximum compression amount of the variable spring, ensuring that the pressure oil entering the pressure feedback chamber always has sufficient pressure to push the variable slider to move, and will not cause the pressure to rise due to the difficulty of compressing the variable spring later. Thus, the pump-out pressure after the oil pump varies can always be at a fixed pressure value under the premise that the PWM value remains unchanged, without requiring the ECU to adjust the PWM. Description of the Drawings

[0019] Figure 1 It is the speed characteristic diagram of the oil pump using the traditional electro-hydraulic proportional valve;

[0020] Figure 2 It is the relatively ideal speed characteristic diagram of the oil pump;

[0021] Figure 3 It is the structural schematic diagram of the electro-hydraulic proportional valve in Embodiment 1 of the present invention;

[0022] Figure 4 is Figure 3 a schematic structural diagram when the PWM duty ratio of the electro-hydraulic proportional valve in

[0023] Figure 5 a schematic connection structure diagram of the oil pump and the electro-hydraulic proportional valve in Embodiment 2 of the present invention;

[0024] Figure 6 a comparative diagram of pressure curves in Embodiment 2 of the present invention;

[0025] The reference numerals are as follows:

[0026] 1 - valve body 2 - spool 3 - spring

[0027] 4 - plug 5 - housing 6 - coil

[0028] 7 - armature push rod 8 - armature limit block

[0029] 10 - pump body 20 - variable slider 30 - variable spring

[0030] 40 - pressure feedback chamber 50 - electro-hydraulic proportional valve. Detailed implementation manners

[0031] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The content mentioned in the implementation manners does not limit the present invention.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0033] In the description of the present invention, it should be noted that unless otherwise specified and defined, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0034] Embodiment 1

[0035] As Figure 3 、 4An electro-hydraulic proportional valve shown is controlled by PWM. When the PWM duty ratio of the proportional valve is at any ratio between 0% and 100%, the opening of the proportional valve depends on the hydraulic pressure entering the proportional valve, and the size of the PWM duty ratio is inversely proportional to the size of the hydraulic pressure.

[0036] Specifically, the electro-hydraulic proportional valve provided in this embodiment includes a valve body 1, a valve core 2, a spring 3 and a plug 4, and a proportional electromagnet installed at one end of the valve body 1, the proportional electromagnet includes a housing 5, a coil 6, an armature push rod 7, and an armature limit block 8, the armature push rod 7 includes a small diameter section and a large diameter section, and the connection between the small diameter section and the large diameter section forms an annular step surface; 1 The valve body is provided with an axial stepped through hole and a radial P port and an A port, the valve core 2, the spring 3 and the plug 4 are installed in the stepped through hole from right to left in sequence, the plug 4 is provided with an axial through hole as a T port, the cross section of the valve core 2 is I-shaped, including a small disc, a rod-shaped portion and a large disc, the diameter φ2 of the large disc is greater than the diameter φ1 of the small disc, wherein a transfer chamber is formed between the rod-shaped portion and the side wall of the stepped through hole; the spring 3 acts on the large disc of the valve core 2, and under the preload of the spring 3, the large disc of the valve core 2 is located between the P port and the A port so that the two are in a separated state. , at this time, the transfer chamber is only connected to the P port; the small diameter section of the armature push rod 7 is inserted from the right end of the valve body 1 into the stepped through hole and contacts and cooperates with the small disc of the valve core 2. The armature push rod 7 can push the valve core 2 to move to the left in the valve body 1 under the action of the electromagnetic force, overcoming the preload force of the spring 3, but the maximum distance that the armature push rod 7 pushes the valve core 2 to move to the left is not enough to connect the P port and the A port; when the oil pressure entering the transfer chamber from the P port reaches the set pressure value, the oil pressure will act on the large disc and push the valve core 2 to continue to move to the left until the P port and the A port are connected; when the PWM duty cycle of the proportional valve is greater than 0% and less than or equal to 100%, the electromagnetic force and hydraulic pressure of the proportional valve can jointly push the valve core 2 to move to a specific position, so that the P port and the A port are in a connected state; when the PWM duty cycle of the proportional valve is 0%, the hydraulic pressure that reaches the set pressure value can alone push the valve core 2 to move to a specific position, so that the P port and the A port are in a connected state.

[0037] like Figure 3 As shown, the right end of the valve body 1 is provided with a limit surface, and the maximum distance △a between the step surface of the armature push rod 7 and the limit surface of the valve body 1 is the maximum displacement of the armature push rod, and the maximum displacement of the armature push rod 7 is less than the maximum displacement of the valve core 2 in the valve body 1; Figure 4 As shown, when the step surface of the armature push rod 7 contacts the limit surface at the right end of the valve body 1, the PWM duty cycle of the proportional valve is 100%.

[0038] Compared with the traditional electro-hydraulic proportional valve, the electro-hydraulic proportional valve provided in this embodiment no longer has the ECU determine the opening and closing of the valve and the opening degree of the valve port. Instead, the opening and closing of the valve and the opening degree of the valve port are determined by the magnitude of the hydraulic pressure entering the proportional valve. The PWM duty cycle is equivalent to providing different degrees of auxiliary force to the hydraulic pressure. Because even when the PWM duty cycle is 100%, if there is no participation of the hydraulic pressure, the P port and the A port still cannot be connected.

[0039] Embodiment 2

[0040] As Figure 5 shown, a vane-type variable displacement oil pump includes a pump body 10, a variable slider 20, a variable spring 30, and a pressure feedback chamber 40. The on-off of the oil inlet passage of the pressure feedback chamber 40 is controlled by the electro-hydraulic proportional valve 50 provided in Embodiment 1. The opening pressure of the electro-hydraulic proportional valve 50 is greater than the pressure corresponding to the maximum compression of the variable spring 30. The electro-hydraulic proportional valve 50 is arranged on the pump body 10. For the specific structure of the electro-hydraulic proportional valve 50, refer to Embodiment 1 and will not be elaborated here. The P port of the electro-hydraulic proportional valve 50 is connected to the main oil passage or the pump outlet, the A port is connected to the pressure feedback chamber 40, and the T port is connected to the oil sump. When the oil pump is not variable, the electro-hydraulic proportional valve 50 is in the closed state. At this time, the A port and the T port are connected, and the pressure oil in the pressure feedback chamber 40 flows into the oil sump through the electro-hydraulic proportional valve 50. As the rotational speed increases, the oil pressure from the main oil passage or the pump outlet reaches the set pressure value, and the oil pressure will push the spool towards the spring end until the P port is connected to the A port. At this time, the electro-hydraulic proportional valve 50 is in the open state, and the oil pressure from the main oil passage or the pump outlet flows into the pressure feedback chamber 40 through the electro-hydraulic proportional valve 50, pushing the variable slider 20 to perform an eccentric movement, thereby reducing the output displacement of the oil pump.

[0041] After combining the electro-hydraulic proportional valve 50 provided in Embodiment 1 with the variable displacement oil pump, the control strategy and speed characteristics of the oil pump will inevitably change. Figure 6Shows two comparisons, one is the pressure curve A of a traditional electro-hydraulic proportional valve and the other is the pressure curve B of the electro-hydraulic proportional valve provided in Embodiment 1. The pressure curve B is significantly very flat. Since the traditional electro-hydraulic proportional valve controls the opening and closing of the valve and the opening of the valve port through the ECU, it cannot limit the magnitude of the oil pressure entering the pressure feedback chamber. After the pressure oil enters the pressure feedback chamber, it only needs to overcome the pre-tightening force of the variable spring to be able to push the variable slider to move. The stiffness range of the variable spring is 6-10 N / mm. Initially, the required compression force is relatively small, and it becomes more difficult to compress later, requiring a greater pressure. Therefore, the pumping pressure of the oil pump increases as the rotational speed increases. However, the electro-hydraulic proportional valve 50 provided in Embodiment 1 needs to be opened by hydraulic pressure. In this way, the minimum opening pressure of the electro-hydraulic proportional valve 50 can be set to be greater than the pressure corresponding to the maximum compression of the variable spring 30, ensuring that the pressure oil entering the pressure feedback chamber 40 always has sufficient pressure to push the variable slider 20 to move, and preventing the pressure from rising due to the difficulty of compressing the variable spring 30 later. Thus, the pumping pressure after the oil pump is variable can always be maintained at a fixed pressure value under the premise that the PWM value remains unchanged, without requiring the ECU to adjust the PWM.

[0042] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

[0043] In order to make it more convenient for those of ordinary skill in the art to understand the improvements of the present invention over the prior art, some of the drawings and descriptions of the present invention have been simplified. And for the sake of clarity, some other elements have also been omitted in this application document. Those of ordinary skill in the art should be aware that these omitted elements can also constitute the content of the present invention.

Claims

1. An electro-hydraulic proportional valve, controlled by PWM, Features: The proportional valve comprises a valve body (1), a valve core (2), a spring (3) and a plug (4), and a proportional solenoid installed at one end of the valve body (1); the valve body (1) is provided with a P port and an A port; when the PWM duty cycle of the proportional valve is at any ratio between 0% and 100%, the opening of the proportional valve depends on the hydraulic pressure entering the proportional valve, and the magnitude of the PWM duty cycle is inversely proportional to the magnitude of the hydraulic pressure; when the PWM duty cycle of the proportional valve is greater than 0% and less than or equal to 100%, the electromagnetic force and the hydraulic pressure of the proportional valve can jointly push the valve core (2) to move to a specific position , so that the P port and the A port are in a connected state; when the PWM duty cycle of the proportional valve is 0%, the hydraulic pressure reaching the set pressure value can independently push the valve core (2) to move to a specific position, so that the P port and the A port are in a connected state; the proportional electromagnet comprises a housing (5), a coil (6), an armature push rod (7), and an armature limit block (8); the armature push rod (7) comprises a small diameter section and a large diameter section, and the connection between the small diameter section and the large diameter section forms an annular step surface; the valve body (1) is provided with an axial stepped through hole and a radial P port and an A port, and the stepped through hole is provided with a plurality of holes from right to left. The valve core (2), spring (3) and plug (4) are sequentially installed on the left side. The plug (4) is provided with an axial through hole as a T port. The cross section of the valve core (2) is I-shaped, including a small disc, a rod-shaped portion and a large disc. The diameter φ1 of the large disc is greater than the diameter φ2 of the small disc. A transfer chamber is formed between the rod-shaped portion and the side wall of the stepped through hole. The spring (3) acts on the large disc of the valve core (2). Under the preload force of the spring (3), the large disc of the valve core (2) is located between the P port and the A port so that the two are in a separated state. At this time, the transfer chamber is only connected to the P port. The small diameter section of the iron push rod (7) is inserted from the right end of the valve body (1) into the stepped through hole and contacts and cooperates with the small disc of the valve core (2). Under the action of electromagnetic force, the armature push rod (7) can push the valve core (2) to move leftward in the valve body (1) to overcome the preload force of the spring (3). However, the maximum distance that the armature push rod (7) pushes the valve core (2) to move leftward is not enough to connect the P port and the A port. When the oil pressure entering the transfer chamber from the P port reaches a set pressure value, the oil pressure will act on the large disc and push the valve core (2) to continue to move leftward until the P port and the A port are connected.

2. The electro-hydraulic proportional valve according to claim 1, Features: A limit surface is provided at the right end of the valve body (1); the maximum distance between the step surface of the armature push rod (7) and the limit surface of the valve body (1) is the maximum displacement of the armature push rod (7); the maximum displacement of the armature push rod (7) is less than the maximum displacement of the valve core (2) in the valve body (1); when the step surface of the armature push rod (7) contacts the limit surface at the right end of the valve body (1), the PWM duty cycle of the proportional valve is 100%.

3. A variable displacement oil pump, comprising a pump body (10), a variable slider (20), a variable spring (30) and a pressure feedback chamber (40), wherein the on-off of the oil inlet oil path of the pressure feedback chamber (40) is controlled by an electro-hydraulic proportional valve (50). Characterized in that: The electro-hydraulic proportional valve (50) is the electro-hydraulic proportional valve described in claim 1 or 2, and the opening pressure of the electro-hydraulic proportional valve (50) is greater than the pressure corresponding to the maximum compression amount of the variable spring (30).

4. The variable displacement oil pump according to claim 3, Characterized in that: The electro-hydraulic proportional valve (50) is arranged on the pump body.

5. The variable displacement oil pump according to claim 3 or 4, Characterized in that: The oil pump is a vane pump.

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