Electronic unit pump

Abstract

A valve body of the electronic unit pump is provided with a first drainage channel and a second drainage channel which are communicated with a main oil channel, and a first electromagnetic valve used for controlling the first drainage channel to be connected and disconnected and a second electromagnetic valve used for controlling the second drainage channel to be connected and disconnected are installed on the valve body. The second electromagnetic valve is closed in a power-off state, and the second drainage channel is disconnected; and when the fuel pressure is higher than the set value, the second electromagnetic valve is opened in the power-off state, the second drainage channel is communicated for drainage, the second electromagnetic valve is closed in the power-on state, and the second drainage channel is disconnected. By controlling the opening and closing moments of the first electromagnetic valve and the second electromagnetic valve, the three-section fuel injection requirement of the engine in the diesel engine state of'pilot injection, main injection and post injection 'can be met, the fuel supply requirement of the micro-injection gas engine can also be met, and the engine can be restored to the full-power diesel engine state to operate after gas fuel is used up.

Description

Technical Field

[0001] The invention relates to the technical field of engine fuel supply systems, and in particular to an electronically controlled unit pump. Background Art

[0002] When the diesel engine fuel supply system is performing fuel injection, it is hoped that the three stages of pre-injection (or boot-shaped injection), main injection, and post-injection can be achieved to improve engine performance and reduce emissions. The high-pressure common rail fuel supply system has a stable fuel pressure in the rail pipe, and controls the injection amount by the opening time of the solenoid valve. The control accuracy is high and can meet the requirements of the three stages of engine pre-injection, main injection, and post-injection.

[0003] The micro-injection pilot dual-fuel engine with a diesel engine as the main body refers to a micro amount of diesel (1% to 5% of the full load fuel volume) as the pilot fuel, which is injected into the cylinder for compression ignition and then ignites the main gas fuel to do work. Since the fuel is the ignition energy of the gas fuel, the amount of fuel injection per cycle directly determines the combustion characteristics of the gas fuel, thereby affecting the performance of the engine. Therefore, the supply control accuracy of the small amount of fuel injected is very high. The high-pressure common rail fuel supply system has a stable fuel pressure in the rail pipe, and the fuel injection amount is controlled by the opening time of the solenoid valve. The control accuracy is high and can meet the micro-injection pilot fuel supply requirements.

[0004] However, the traditional fuel supply system based on electronically controlled unit pump cannot meet the three-stage injection requirements of diesel engines and the small oil injection requirements of micro-injection ignition dual-fuel engines.

[0005] The traditional electronically controlled single pump fuel supply system usually includes a cam, an oil pumping system, a solenoid valve, a high-pressure oil pipe, and a fuel injector. The cam drives the roller to drive the plunger to reciprocate and pressurize the diesel to the high-pressure chamber. When the electromagnet is not energized, the sealing cone surface is not in contact, and the diesel in the high-pressure chamber leaks through the gap of the sealing cone surface. The diesel in the high-pressure oil pipe does not build up high pressure and cannot drive the fuel injector to open, so the fuel injector does not spray fuel. When the solenoid valve is energized, the sealing cone surface is in contact, the diesel pressure in the high-pressure chamber increases, and enters the fuel injector through the high-pressure oil pipe. After the diesel pressure reaches the opening pressure of the injector, the injector opens to spray the diesel into the cylinder. When the solenoid valve is de-energized again, the sealing cone surface opens to release pressure under the action of the spring force, and the fuel injector stops spraying fuel.

[0006] During the cam oil pumping process, the time from the closing to the opening of the solenoid valve can be controlled to control the amount of oil supplied per cycle of the single pump. Under certain speed conditions, the time t from the closing to the opening of the solenoid valve corresponds to the cam angle α. If the system meets the requirements of the micro-injection engine and the injection amount is to reach 1% to 5% of the full load oil amount, the corresponding cam angle β must be quite small when running in the micro-injection state. For example, at a certain engine speed, the time from the closing to the opening of the corresponding solenoid valve is 2 milliseconds, and the corresponding time requirement for micro-injection is less than 0.2 milliseconds, which far exceeds the response time requirement of the solenoid valve.

[0007] High-pressure common rail fuel supply systems have been widely used in diesel engines with power below 500KW. For large engines with power greater than 1000KW, the cost of the matching high-pressure common rail fuel supply system has soared significantly due to changes in process and structure, and the price has increased by more than ten times, which has limited its application. Therefore, most large diesel engines still use electronically controlled single pump fuel supply systems.

[0008] Some manufacturers' micro-injection engines adopt the solution of matching with a small high-pressure common rail fuel system. For example, for a 1000KW engine, the matching high-pressure common rail system can only meet the diesel supply demand of 300KW. This solution solves the problem of fuel supply system cost (small high-pressure common rail system has low cost) and control accuracy in the micro-injection state. However, when the gas fuel is used up, it cannot be restored to the full-power diesel engine state (it can only be restored to the 300Kw diesel engine state), which limits its application. Summary of the invention

[0009] In view of this, the present invention provides an electronically controlled single pump, which can realize the three-stage fuel injection requirements of "pre-injection, main injection, and post-injection" of the engine in the diesel engine state, and can also meet the fuel supply needs of the micro-injection gas engine, and can restore the engine to the full-power diesel engine state after the gas fuel is used up.

[0010] In order to solve the above-mentioned first technical problem, the technical solution adopted by the present invention is:

[0011] An electronically controlled single pump comprises: a pump body, on which a valve body is fixedly mounted and a push rod is slidably mounted, a main spring is clamped between the valve body and the push rod, the push rod is mounted with a roller extending out of the pump body, and the roller is controlled by an oil pumping cam of a camshaft; the pump body is provided with an oil inlet hole, the valve body is provided with an oil inlet passage, a main oil passage, a high-pressure chamber and an oil outlet hole, the oil inlet hole is communicated with the oil inlet passage, one end of the main oil passage is communicated with the oil outlet hole, and the other end is communicated with the high-pressure chamber, a plunger is slidably mounted in the valve body and abuts against the push rod, the oil pumping cam drives the roller to drive the plunger to reciprocate, and the fuel from the oil inlet hole is pressurized to the high-pressure chamber; the valve body is provided with a first leakage flow passage and a second leakage flow passage respectively communicated with the main oil passage, A first solenoid valve for controlling the on and off of the first leakage channel and a second solenoid valve for controlling the on and off of the second leakage channel are installed on the body, the first solenoid valve is a normally open solenoid switch valve, and the second solenoid valve is a normally closed solenoid switch valve; when the first solenoid valve is opened in a power-off state, the first leakage channel is connected to discharge flow, and when the first solenoid valve is closed in a power-on state, the first leakage channel is disconnected; under the condition that the fuel pressure in the high-pressure chamber is lower than a set value, the second solenoid valve is closed in a power-off state, and the second leakage channel is disconnected; under the condition that the fuel pressure in the high-pressure chamber is higher than the set value, the second solenoid valve is opened in a power-off state, the second leakage channel is connected to discharge flow, the second solenoid valve is closed in a power-on state, and the second leakage channel is disconnected.

[0012] The first solenoid valve comprises a first electromagnet, a first valve core and a first positioning seat, the first leakage passage comprises a first valve core hole, a first oil return chamber and a first oil return passage which are opened on the valve body and are sequentially connected, the first valve core hole is connected to the main oil passage, the first oil return passage is connected to the oil tank, the first valve core is slidably arranged in the first valve core hole and is sleeved with a first control spring and a spring seat, the spring seat is pressed against the shaft shoulder of the first valve core, a magnetic isolation pad is arranged between the first electromagnet and the valve body, a first spring stopper is constrained between the magnetic isolation pad and the valve body, the first control spring is clamped between the spring seat and the first spring stopper, a first valve core sealing surface is arranged at the head of the first valve core, a first valve body sealing surface is arranged at the first valve core hole, a distance for determining the opening lift of the first valve core is provided between the end surface of the first valve core head and the end surface of the first positioning seat, and under the action of the first electromagnet and the first control spring, the first valve core sealing surface is fitted or separated from the first valve body sealing surface to control the on-off of the first leakage passage.

[0013] The second solenoid valve comprises a second electromagnet, a second valve core and a second positioning seat, the second leakage passage comprises a second valve core hole, a second oil return chamber and a second oil return passage which are sequentially connected and opened on the valve body, the second valve core hole is connected to the main oil passage, the second oil return passage is connected to the oil tank, or the second oil return passage is not provided, the second oil return chamber is connected to the first oil return chamber through a connecting passage, the second valve core hole is a stepped hole, the stepped hole comprises a large hole and a small hole, the second valve core is slidably arranged in the small hole and is sleeved with a second control spring, the second valve core is fixed with a second spring baffle, the second control spring is clamped and pressed on the second Between the spring stopper and the valve body, the head of the second valve core is provided with a second valve core sealing surface, and the large hole is provided with a second valve body sealing surface. The end surface of the head of the second valve core and the end surface of the second positioning seat have a distance that determines the opening lift of the second valve core. Under the joint action of the second electromagnet, the second control spring and the fuel pressure in the high-pressure chamber, the second valve core sealing surface and the second valve body sealing surface are fitted or disengaged to control the opening and closing of the second leakage channel. The combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the second control spring is greater than the pressure difference on the second valve core caused by the maximum fuel pressure. Or

[0014] The second solenoid valve includes a second electromagnet, a second valve core and a second positioning seat, the second leakage channel includes a second valve core hole, a second oil return chamber and a second oil return passage which are sequentially connected to each other and are opened on the valve body, the second valve core hole is connected to the main oil passage, the second oil return passage is connected to the oil tank, or the second oil return passage is not provided, the second oil return chamber is connected to the first oil return chamber through a connecting passage, the second valve core hole is a stepped hole, the stepped hole includes a large hole and a small hole, the second valve core is slidably arranged in the small hole, the second positioning seat is provided with a countersunk hole, a third control spring is arranged in the countersunk hole, and the third control spring is axially pressed against The head of the second valve core is provided with a second valve core sealing surface, and the large hole is provided with a second valve body sealing surface. There is a distance between the end surface of the second valve core head and the end surface of the second positioning seat to determine the opening lift of the second valve core. Under the joint action of the second electromagnet, the third control spring and the fuel pressure in the high-pressure chamber, the second valve core sealing surface and the second valve body sealing surface are fitted or disengaged to control the opening and closing of the second leakage channel. The combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the third control spring is greater than the pressure difference generated on the second valve core by the maximum fuel pressure.

[0015] After adopting the above technical solution, the technical effects achieved by the present invention are:

[0016] Since the valve body is provided with a first leakage channel and a second leakage channel respectively connected with the main oil channel, a first solenoid valve for controlling the on and off of the first leakage channel and a second solenoid valve for controlling the on and off of the second leakage channel are installed on the valve body, the first solenoid valve is a normally open solenoid switch valve, and the second solenoid valve is a normally closed solenoid switch valve; when the first solenoid valve is opened in a power-off state, the first leakage channel is connected to the leakage flow, and when the first solenoid valve is closed in a power-on state, the first leakage channel is disconnected; when the fuel pressure in the high-pressure chamber is lower than the set value, under the action of the spring force of the second control spring, the sealing surface of the second valve core fits with the sealing surface of the second valve body, the second solenoid valve is closed, and the second leakage channel is disconnected; when the fuel pressure in the high-pressure chamber is lower than the set value, under the action of the spring force of the second control spring, the sealing surface of the second valve core fits with the sealing surface of the second valve body, the second solenoid valve is closed, and the second leakage channel is disconnected; When the fuel pressure in the high-pressure chamber is higher than the set value, when the second electromagnet is powered off, the fuel pressure generates a pressure difference on the second valve core to overcome the spring force of the second control spring, and the second valve core sealing surface is separated from the second valve body sealing surface, and the second solenoid valve is opened to connect the second leakage channel to discharge. When the second electromagnet is powered on, the second solenoid valve is closed under the action of electromagnetic force to disconnect the second leakage channel. By controlling the opening and closing times of the two solenoid valves, the three-stage fuel injection requirements of "pre-injection, main injection, and post-injection" of the engine in the diesel engine state can be achieved, and the fuel supply requirements of the micro-injection gas engine can also be met, and the engine can be restored to the full-power diesel engine state after the gas fuel is used up.

[0017] In the present invention, by setting the second valve core hole as a stepped hole, the fuel pressure produces a pressure difference on the second valve core, and the second solenoid valve has an overflow function, thereby controlling the injection pressure of the fuel. By adjusting the opening lift of the second valve core, the second solenoid valve has a throttling function, thereby controlling the injection flow rate of the fuel. The combination of the two can improve the control accuracy.

[0018] In the present invention, the combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the second control spring or the third control spring is greater than the pressure difference on the second valve core caused by the maximum fuel pressure, which can ensure that the second valve core is closed after the second solenoid valve is energized. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a longitudinal sectional view of Example 1 of the electronically controlled monomer pump of the present invention;

[0020] Figure 2 yes Figure 1 A partial enlarged view of point Ⅰ in the middle;

[0021] Figure 3 yes Figure 1 A partial enlarged view of the middle II;

[0022] Figure 4 yes Figure 3 A partial enlarged view of the middle part III;

[0023] Figure 5 yes Figure 1 The illustrated embodiment 1 realizes the fuel injection pressure waveform diagram of the three stages of boot injection, main injection and post injection;

[0024] Figure 6 yes Figure 1 The diagram shows a comparison of the injection pressure waveform of the embodiment 1 when implemented on a micro-injection dual-fuel gas engine and a single injection pump of a conventional structure;

[0025] Figure 7 This is a partial enlarged view of the electronically controlled monomer pump embodiment 2 of the present invention, which is equivalent to the embodiment 1 at position II;

[0026] In the figure, 10, oil pump cam; 21, pump body; 211, oil inlet hole; 22, push rod; 23, roller; 24, main spring; 25, plunger; 26, valve body; 261, oil inlet passage; 262, high pressure chamber; 263, main oil passage; 264, first oil return chamber; 265, second oil return chamber; 266, first oil return passage; 267, connecting passage; 268, first valve body sealing surface; 269, second valve body sealing surface; 31, first electromagnet; 32. First valve core; 321. First valve core sealing surface; 33. First control spring; 34. First positioning seat; 35. Spring seat; 36. First spring retaining plate; 37. Magnetic isolation pad; 41. Second electromagnet; 42. Second valve core; 421. Second valve core sealing surface; 43. Second control spring; 44. Second positioning seat; 45. Second spring retaining plate; 46. Magnetic isolation pad; 47. Third control spring; 50. High-pressure oil pipe; 60. Fuel injector;

[0027] S1, the opening lift of the first valve core; S2, the opening lift of the second valve core; D, the diameter of the large hole; d, the diameter of the small hole;

[0028] t1, the time from closing to opening of the solenoid valve of the conventional structure single pump; tx, the time from closing to opening of the first solenoid valve of the embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0030] Example 1

[0031] like Figure 1As shown, an electrically controlled single pump, a pump body 21 is fixedly mounted with a valve body 26 and a push rod 22 is slidably mounted, a main spring 24 is clamped between the valve body 26 and the push rod 22, and the push rod 22 is mounted with a roller 23 extending out of the pump body 21, and the roller 23 is controlled by the oil pump cam 10 of the camshaft. For a large-cylinder engine, the camshaft is separate and is installed separately from the pump body 21; for a small-cylinder engine, the camshaft is integrated into the pump body 21 and is rotatably mounted with the pump body 21.

[0032] The pump body 21 is provided with an oil inlet hole 211, and the valve body 26 is provided with an oil inlet passage 261, a main oil passage 263, a high pressure chamber 262 and an oil outlet hole. The oil inlet hole 211 is connected with the oil inlet passage 261, one end of the main oil passage 263 is connected with the oil outlet hole, and the other end is connected with the high pressure chamber 262. The oil outlet hole is connected with a high pressure oil pipe, and the high pressure oil pipe 50 is connected with the injector 60. A plunger 25 is slidably mounted in the valve body 26 to abut against the push rod 22. The oil pump cam 10 drives the roller to drive the plunger to reciprocate, and the fuel from the oil inlet hole is pressurized to the high pressure chamber 262, and is ejected from the main oil passage 263 through the high pressure oil pipe 50 by the injector 60.

[0033] The valve body 26 is provided with a first leakage channel and a second leakage channel respectively connected to the main oil channel 263, and a first solenoid valve for controlling the on and off of the first leakage channel and a second solenoid valve for controlling the on and off of the second leakage channel are respectively installed on the valve body 26. The opening lift of the valve core of the first solenoid valve is S1, and the opening lift of the valve core of the second solenoid valve is S2. It is set that S1>>S2, for example, it is designed that S1=0.15 mm, S2=0.015 mm, and this value can be adjusted as needed, and does not constitute a limitation on the protection scope of the present invention.

[0034] like Figure 1 and Figure 2As shown together, the first solenoid valve is a normally open solenoid switch valve. When the first solenoid valve is opened in the power-off state, the first leakage channel is connected to the leakage flow. When the first solenoid valve is closed in the power-on state, the first leakage channel is disconnected. The first solenoid valve includes a first electromagnet 31, a first valve core 32 and a first positioning seat 34. The first leakage channel includes a first valve core hole, a first oil return chamber 264 and a first oil return channel 266 which are opened on the valve body 26 and are sequentially connected. The first valve core hole is connected to the main oil channel 263, and the first oil return channel 266 is connected to the oil tank (not shown in the figure). The first valve core 32 is slidably arranged in the first valve core hole and is sleeved with a first control spring 33 and a spring seat 35. The spring seat 35 is against the shaft shoulder of the first valve core 32. A magnetic isolation pad 37 is arranged between the first electromagnet 31 and the valve body 26. A first spring stopper 36 is constrained between 37 and the valve body 26, and a first control spring 33 is clamped between the spring seat 35 and the first spring stopper 36. A first valve core sealing surface 321 is provided at the head of the first valve core 32, and a first valve body sealing surface 268 is provided at the first valve core hole. A distance between the end surface of the head of the first valve core 32 and the end surface of the first positioning seat 34 determines the opening lift S1 of the first valve core. Under the action of the first electromagnet 31 and the first control spring 33, the first valve core sealing surface 321 is fitted or disengaged from the first valve body sealing surface 268 to control the on-off of the first leakage channel.

[0035] like Figure 1 , Figure 3 and Figure 4As shown together, the second solenoid valve is a normally closed solenoid switch valve. When the fuel pressure in the high-pressure chamber is lower than the set value, the second solenoid valve is closed in the power-off state, and the second leakage channel is disconnected; when the fuel pressure in the high-pressure chamber is higher than the set value, the second solenoid valve is opened in the power-off state, and the second leakage channel is connected to the leakage flow. The second solenoid valve is closed in the power-on state, and the second leakage channel is disconnected. The second solenoid valve includes a second electromagnet 41, a second valve core 42, and a second positioning seat 44. The second leakage channel includes a second valve core hole and a second oil return chamber 265 that are connected to each other and opened on the valve body 26. The second valve core hole is connected to the main oil channel 263, and the second oil return chamber 265 is connected to the first oil return chamber 264 through a connecting channel 267. The second valve core hole is a stepped hole, and the stepped hole includes a large hole (the diameter of the large hole is marked as D) and a small hole (the diameter of the small hole is marked as d). The second valve core 42 is slidably disposed in the small hole and is sleeved with a second control spring 43. The second valve core 42 is fixed There is a second spring stopper 45, and a second control spring 43 is clamped between the second spring stopper 45 and the valve body 26. The head of the second valve core 42 is provided with a second valve core sealing surface 421, and the large hole is provided with a second valve body sealing surface 269. There is a distance between the end surface of the head of the second valve core 42 and the end surface of the second positioning seat 44 for determining the opening lift S2 of the second valve core. Under the action of the second electromagnet 41, the second control spring 43 and the fuel pressure in the high-pressure chamber, the second valve core sealing surface 421 is fitted or disengaged from the second valve body sealing surface 269 to control the opening and closing of the second leakage channel.

[0036] As another embodiment, the second leakage channel is independently arranged, that is, no connecting channel is arranged between the first oil return chamber 264 and the second oil return chamber 265, but a second oil return channel (not shown in the figure) connected to the second oil return chamber 265 is arranged, and the second oil return chamber 265 is directly connected to the oil tank through the second oil return channel.

[0037] The working principle of the second solenoid valve is as follows:

[0038] 1) The direction of the spring force and the electromagnetic force is the direction of the valve core closing; (upward in the figure).

[0039] 2) If Figure 3 As shown, the direction of the force exerted by the high-pressure chamber fuel on the second valve core 42 is the opening direction of the second valve core 42 (downward direction in the figure), and the force area is: π / 4 (D 2 -d 2 ), assuming that the hydraulic oil pressure in the high-pressure chamber is P, the magnitude of the force is π / 4(D 2 -d 2 )P.

[0040] 3) Setting the size of the second valve core opening lift S2 can play a throttling role.

[0041] 4) The elastic force of the second control spring 43 is set to control the opening pressure of the second solenoid valve. For example, if the opening pressure of the second solenoid valve is required to be 20 MPa, d=10 mm, D=10.05 mm, then the elastic force of the second control spring 43 is designed to be: π / 4(10.052-102)*20=15.7N; when the second electromagnet 41 is not energized to generate electromagnetic force, when the fuel pressure reaches 20 MPa, the second valve core 42 can be opened to discharge.

[0042] 5) In order to ensure that the second valve core is closed after the second solenoid valve is energized, the combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the second control spring 43 is greater than the pressure difference on the second valve core 42 caused by the maximum fuel pressure. For example, if the maximum fuel pressure is 180MPa, the force acting on the second valve core 42 is π / 4(10.052-102)*180=141.7N. The electromagnetic force of the second solenoid valve is designed to be greater than 141.7-15.7=126N, which can ensure that the valve core is closed after the solenoid valve is energized.

[0043] 6) When the fuel pressure in the high-pressure chamber is lower than 20 MPa, the second valve core 42 is closed under the spring force of the second control spring 43.

[0044] 7) When the fuel pressure in the high-pressure chamber is 20 MPa, when the second electromagnet 41 is powered off, the second valve core 42 is opened, and when the second electromagnet 41 is powered on, the second valve core 42 is closed.

[0045] In the present invention, by setting the second valve core hole as a stepped hole, the fuel pressure produces a pressure difference on the second valve core 42, and the second solenoid valve has an overflow function, thereby controlling the injection pressure of the fuel. By adjusting the opening lift of the second valve core 42, the second solenoid valve has a throttling function, thereby controlling the injection flow rate of the fuel. The combination of the two can improve the control accuracy.

[0046] In this embodiment, the first oil return chamber 264 surrounds the outer circumference of the first positioning seat 34 , and the second oil return chamber 265 surrounds the outer circumference of the second positioning seat 44 .

[0047] In this embodiment, the first valve core sealing surface 321 and the first valve body sealing surface 268 are respectively matched sealing conical surfaces; the second valve core sealing surface 421 and the second valve body sealing surface 269 are respectively matched sealing conical surfaces. Figure 4 As shown, the second valve core sealing surface 421 and the second valve body sealing surface 269 have different cone angles, and the angle θ is greater than zero. When the two are close together, a sealing belt is formed, which improves the sealing effect compared to surface sealing. The first valve core sealing surface 321 and the first valve body sealing surface 268 also have similar structures and effects.

[0048] By controlling the opening and closing timings of the first solenoid valve and the second solenoid valve, a variety of injection pressure waveforms can be formed.

[0049] like Figure 5 As shown, the electronic control unit (ECU) controls the first solenoid valve 32 to be powered on and closed. After the fuel pressure in the high-pressure chamber rises to 20 MPa, the second solenoid valve 42 is opened. After a certain period of time, the second solenoid valve 42 is powered on and closed, and the pressure begins to rise rapidly, forming a boot-shaped injection; after a certain period of time, the first solenoid valve 32 and the second solenoid valve 42 are simultaneously powered off and opened, generating a main injection waveform; subsequently, the first solenoid 31 is controlled to be powered on / off to open / close the first solenoid valve, and the second solenoid 41 is not powered on. Under the action of the fuel pressure, the second solenoid valve remains open, generating a post-injection waveform.

[0050] Regarding the post-injection control, it is quite necessary to keep the second solenoid valve open after reaching a certain pressure. Figure 5 The double-dotted line part is the post-injection waveform when the second solenoid valve is not set, and the solid line is the waveform of the second solenoid valve being opened. Figure 5 It can be seen that for the same amount of post-injection fuel, the solid line waveform corresponds to a longer duration. It can be seen that by setting the second solenoid valve, the requirements for the solenoid valve are reduced. The fuel supply control method can realize the three-stage fuel injection of "boot-shaped injection, main injection, and post-injection". Similarly, the effect of the three-stage fuel injection of "pre-injection, main injection, and post-injection" can also be expected.

[0051] like Figure 6 As shown, in the micro-injection dual-fuel gas engine, the second solenoid valve is kept in a non-energized state, and the time tx from the closing to the opening of the first solenoid valve is controlled, tx>>t1, so that a fuel injection amount with high precision and small injection amount can be obtained. It can be seen that the fuel supply control method can meet the fuel supply demand of the micro-injection gas engine, and can restore the engine to a full-power diesel engine state after the gas fuel is used up.

[0052] Example 2

[0053] The structure of embodiment 2 is basically the same as that of embodiment 1, except that the control spring is set differently. Figure 7 As shown, the second positioning seat 44 is provided with a counterbore, and a third control spring 47 is provided in the counterbore, and the third control spring 47 axially presses against the head of the second valve core 42. Under the action of the second electromagnet 41, the third control spring 47 and the fuel pressure of the high-pressure chamber, the second valve core sealing surface 421 is in contact with or out of contact with the second valve body sealing surface 269 to control the opening and closing of the second leakage channel.

[0054] The present invention is not limited to the above-mentioned embodiments. For example, a combination of three or more solenoid valves may be used. By setting different valve core lifts, more injection waveforms may be generated. All improvements based on the concept, principle, structure and method of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An electronically controlled monomer pump, comprising: A pump body, wherein a valve body is fixedly mounted on the pump body and a push rod is slidably mounted on the pump body, a main spring is clamped between the valve body and the push rod, the push rod is mounted with a roller extending out of the pump body, and the roller is controlled by an oil pumping cam of a camshaft; the pump body is provided with an oil inlet hole, the valve body is provided with an oil inlet passage, a main oil passage, a high-pressure chamber and an oil outlet hole, the oil inlet hole is communicated with the oil inlet passage, one end of the main oil passage is communicated with the oil outlet hole, and the other end is communicated with the high-pressure chamber, a plunger is slidably mounted in the valve body and abuts against the push rod, the oil pumping cam drives the roller to drive the plunger to reciprocate, and the fuel from the oil inlet hole is pressurized to the high-pressure chamber; it is characterized in that The valve body is provided with a first leakage channel and a second leakage channel respectively connected with the main oil channel, and a first solenoid valve for controlling the on and off of the first leakage channel and a second solenoid valve for controlling the on and off of the second leakage channel are installed on the valve body, the first solenoid valve is a normally open solenoid switch valve, and the second solenoid valve is a normally closed solenoid switch valve; when the first solenoid valve is opened in a power-off state, the first leakage channel is connected to the leakage flow, and when the first solenoid valve is closed in a power-on state, the first leakage channel is disconnected; under the condition that the fuel pressure of the high-pressure chamber is lower than the set value, the second solenoid valve is closed in a power-off state, and the second leakage channel is disconnected; under the condition that the fuel pressure of the high-pressure chamber is higher than the set value, the second solenoid valve is opened in a power-off state, the second leakage channel is connected to the leakage flow, the second solenoid valve is closed in a power-on state, and the second leakage channel is disconnected.

2. The electronically controlled unit pump according to claim 1, characterized in that: The first solenoid valve comprises a first electromagnet, a first valve core and a first positioning seat, the first leakage passage comprises a first valve core hole, a first oil return chamber and a first oil return passage which are opened on the valve body and are sequentially connected, the first valve core hole is connected to the main oil passage, the first oil return passage is connected to the oil tank, the first valve core is slidably arranged in the first valve core hole and is sleeved with a first control spring and a spring seat, the spring seat is pressed against the shaft shoulder of the first valve core, a magnetic isolation pad is arranged between the first electromagnet and the valve body, a first spring stopper is constrained between the magnetic isolation pad and the valve body, the first control spring is clamped between the spring seat and the first spring stopper, a first valve core sealing surface is arranged at the head of the first valve core, a first valve body sealing surface is arranged at the first valve core hole, a distance for determining the opening lift of the first valve core is provided between the end surface of the first valve core head and the end surface of the first positioning seat, and under the action of the first electromagnet and the first control spring, the first valve core sealing surface is fitted or separated from the first valve body sealing surface to control the on-off of the first leakage passage.

3. The electronically controlled unit pump according to claim 2, characterized in that: The second solenoid valve comprises a second electromagnet, a second valve core and a second positioning seat. The second leakage passage comprises a second valve core hole, a second oil return chamber and a second oil return passage which are sequentially connected and opened on the valve body. The second valve core hole is connected to the main oil passage, and the second oil return passage is connected to the oil tank, or the second oil return passage is not provided. The second oil return chamber is connected to the first oil return chamber through a connecting passage. The second valve core hole is a stepped hole, and the stepped hole comprises a large hole and a small hole. The second valve core is slidably arranged in the small hole and sleeved with a second control spring. The second valve core is fixed with a second spring retaining plate, and the second control spring is clamped between the second spring retaining plate and the valve body. The head of the second valve core is provided with a second valve core sealing surface, and the large hole is provided with a second valve body sealing surface. There is a distance between the end surface of the head of the second valve core and the end surface of the second positioning seat to determine the opening lift of the second valve core. Under the joint action of the second electromagnet, the second control spring and the fuel pressure of the high-pressure chamber, the sealing surface of the second valve core is fitted or separated from the sealing surface of the second valve body to control the opening and closing of the second leakage passage.

4. The electronically controlled unit pump according to claim 3, characterized in that: The combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the second control spring is greater than the pressure difference generated on the second valve core by the maximum fuel pressure.

5. The electronically controlled unit pump according to claim 2, characterized in that: The second solenoid valve comprises a second electromagnet, a second valve core and a second positioning seat. The second leakage passage comprises a second valve core hole, a second oil return chamber and a second oil return passage which are sequentially connected to each other and are opened on the valve body. The second valve core hole is connected to the main oil passage, and the second oil return passage is connected to the oil tank, or the second oil return passage is not provided. The second oil return chamber is connected to the first oil return chamber through a connecting passage. The second valve core hole is a stepped hole, and the stepped hole comprises a large hole and a small hole. The second valve core is slidably arranged in the small hole. The second positioning seat is provided with a counterbore, and a third control spring is arranged in the counterbore. The third control spring axially abuts against the head of the second valve core. The head of the second valve core is provided with a second valve core sealing surface, and the large hole is provided with a second valve body sealing surface. There is a distance between the end surface of the second valve core head and the end surface of the second positioning seat to determine the opening lift of the second valve core. Under the joint action of the second electromagnet, the third control spring and the fuel pressure of the high-pressure chamber, the sealing surface of the second valve core is fitted or separated from the sealing surface of the second valve body to control the opening and closing of the second leakage passage.

6. The electronically controlled unit pump according to claim 5, characterized in that: The combined force of the electromagnetic force set by the second solenoid valve and the spring force set by the third control spring is greater than the pressure difference generated on the second valve core by the maximum fuel pressure.

7. The electronically controlled unit pump according to claim 3 or 5, characterized in that: The first oil return chamber surrounds the outer circumference of the first positioning seat, and the second oil return chamber surrounds the outer circumference of the second positioning seat.

8. The electronically controlled unit pump according to claim 3 or 5, characterized in that: The first valve core sealing surface and the first valve body sealing surface are respectively matched sealing conical surfaces, and the cone angles of the first valve core sealing surface and the first valve body sealing surface are different; the second valve core sealing surface and the second valve body sealing surface are respectively matched sealing conical surfaces, and the cone angles of the second valve core sealing surface and the second valve body sealing surface are different.

9. The electronically controlled unit pump according to claim 1, characterized in that: The camshaft is rotatably mounted on the pump body, or the camshaft and the pump body are installed separately.

10. The electronically controlled unit pump according to claim 1, characterized in that: The oil outlet is connected to a high-pressure oil pipe, and the high-pressure oil pipe is connected to a fuel injector.

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