A pressure-lubricated tappet for a common rail pump

Abstract

The application provides a pressure lubrication tappet of a common rail pump, which comprises a tappet body, a roller and a roller pin; the roller pin is inserted into a pin hole of the tappet body, and the roller is supported on the roller pin. The outer diameter of the tappet body has an axial guide groove in the vertical direction of the roller pin, a guide pin installed on a pump body is inserted into the guide groove to limit the circumferential direction of the tappet, and the upper part of the outer diameter of the tappet body has a ring groove; an oil guide groove is connected between the ring groove and the pin hole, and the ring groove is isolated from the guide groove. The lubrication mode is divided into three sections, i.e. upper, middle and lower sections, according to the lift of the tappet; the ball head of the roller pin is connected to a cam cavity in the lower section of the lift of the tappet, is connected to the cam cavity and an oil inlet at the same time in the middle section, and is connected to the oil inlet in the upper section. The design can control the oil flow to be proportional to the heat generated by the friction of the oil pump, can prevent particles from entering the gap between the roller pin and the tappet to block the roller pin, and can improve the reliability and durability.

Description

Technical Field

[0001] This application relates to the field of diesel engine common rail system technology, specifically a pressure lubrication tappet for a common rail pump. Background Technology

[0002] The load borne by the tappet of a diesel engine oil pump is the product of the area of ​​the plunger diameter and the oil supply pressure. The oil supply pressure of a common rail pump can reach 200 MPa or even higher, and the tappet load accounts for 50% or even longer of the time. In contrast, the oil supply pressure of a mechanical injection pump is only about 100 MPa, and the tappet load accounts for only about 15% of the time. Therefore, the friction power of the two pairs of friction pairs of tappet roller pin to pin hole and roller in a common rail pump is more than ten times that of a mechanical injection pump. More effective lubrication and friction reduction and removal of heat converted from friction power are required. The common lubrication method is to use the reciprocating motion of the tappet to open and close the oil inlet, allowing the oil to enter the cam chamber intermittently. The rotation of the cam splashes the oil onto the roller and roller pin to achieve lubrication. Existing patents disclose forced lubrication tappets that directly direct engine oil to the two pairs of friction pairs. These tappets come in two structures: one with no oil pressure in the friction pair's clearance, and the other with oil pressure. Examples include CN103047063A, CN203035419U, and CN203098114U. In these tappets, the engine oil is simultaneously connected to the pressure-free areas above and below the friction pairs and the tappet itself. Therefore, the oil in the friction pair area has no pressure and cannot penetrate the clearance. Another example is CN201025197Y and CN206468471U. In these tappets, the engine oil is connected to the friction pairs but isolated from the pressure-free areas, maintaining the pressure provided by the oil pump. Under pressure, the oil passes through the clearance of the friction pairs and flows to the pressure-free cam cavity below the tappet, resulting in better lubrication than the former. To distinguish between the two, the latter is referred to as a pressure-lubricated tappet.

[0003] Whether it's the existing diesel engine oil pump tappets or the forced lubrication tappets provided in the aforementioned patent documents, the proportion of time the tappet is connected to the oil flow is fixed. The tappet connects to the oil during a certain lift or throughout the entire lift. Therefore, the oil flow rate is independent of the tappet's up-and-down movement frequency, and thus independent of the engine speed. It depends on the oil pressure, the proportion of time the oil is connected, and the oil passage resistance. The oil pressure depends on the diesel engine's oil pump and varies little across the entire speed range from idle to high speed. The design measure to control the oil flow rate is a reasonable balance between the oil passage resistance and the proportion of the lift when the oil is connected, ensuring that the oil flow rate meets the requirements of the oil pump at its maximum speed. However, the frictional work of the tappet and the total frictional work of the oil pump are both proportional to the tappet's up-and-down movement frequency, leading to excessive oil flow at low and medium speeds, wasting energy.

[0004] All of the above patented structures share a common drawback: the engine oil is guided to directly contact the outer diameter of the roller pin. If there are particles in the engine oil, they may be drawn into the mating gap by the rotating outer diameter of the roller pin, causing the roller pin to seize and damaging the friction pair. Therefore, none of the above patents have been seen in mass production. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a pressure lubrication tappet for a common rail pump, thereby resolving the issues present in the background art.

[0006] A pressure lubrication tappet for a common rail pump includes a tappet body, a roller, and a roller pin. The roller pin is inserted into a pin hole in the tappet body, and the roller is supported on the roller pin. The outer diameter of the tappet has an axial guide groove in the direction perpendicular to the roller pin. A guide pin, screwed into the pump body, has a cylindrical head inserted into the guide groove. The upper part of the outer diameter of the tappet has a ring groove, and an oil guide notch between the ring groove and the pin hole connects the ring groove to the ball head of the roller pin.

[0007] The ring groove is isolated from the guide groove, so when the oil enters the ring groove, it will not release the pressure through the guide groove.

[0008] The external volume of the roller pin ball head leads only to the cam cavity in the lower section of the tappet's lift, to both the cam cavity and the oil inlet in the middle section of the tappet's lift, and to the oil inlet in the upper section of the tappet's lift.

[0009] The beneficial effects of this application are as follows:

[0010] (1) The oil flow rate is directly proportional to the oil pump speed. The trend of the total oil flow rate increasing with the increase of the speed is exactly matched with the trend of the total friction power and heat generation of the oil pump increasing with the increase of the speed, thus achieving the effect of saving energy.

[0011] (2) If there are particulate matter in the engine oil, since the particulate matter can only contact the spherical surface and cannot contact the outer diameter of the roller pin, it is impossible for the particulate matter to be drawn into the mating clearance by the linear velocity of the outer diameter. When the tappet body descends to the ball head and is exposed in the cam cavity, the particulate matter falls into the cam cavity and flows back to the diesel engine oil pan, and is finally intercepted by the oil filter. This setting can prevent particulate matter from entering the mating clearance of the roller pin and jamming the roller pin, thus improving reliability and durability. Attached Figure Description

[0012] Figure 1 This refers to the position of the tappet at the lower end of its lift stroke.

[0013] Figure 2 for Figure 1 AA section view;

[0014] Figure 3 The tappet is positioned in the middle of its lifting stroke;

[0015] Figure 4This refers to the position of the tappet at the upper stop point of the upper stage of its lift stroke;

[0016] Figure 5 The curve showing the change in external oil pressure at the roller pin ball head as a function of tappet lift.

[0017] Figure 6 This is a curve showing the change in oil flow rate with engine speed. Detailed Implementation

[0018] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments.

[0019] Reference Figure 1 and Figure 2 A pressure lubrication tappet for a common rail pump includes a tappet body 1, a roller 2, and a roller pin 3. The roller pin 3 is inserted into the pin hole 1.1 of the tappet body, and the roller 2 is supported on the roller pin 3. The outer diameter of the tappet has a vertical guide groove 1.3 radially to the roller pin. A guide pin 5 is screwed into the pump body 4, with its cylindrical head inserted into the guide groove 1.3 to position the tappet circumferentially. Above the guide groove 1.3, there is an outer diameter groove 1.2 of the tappet body 1, which is not connected to the guide groove 1.3. An oil guide notch 1.4 connects the groove 1.2 to the ball head 3.1 of the roller pin between the groove 1.2 and the pin hole 1.1. Driven by a cam 6, the tappet reciprocates up and down in the guide hole 4.1 of the pump body, reaching the... Figure 2 Near the bottom dead center position shown, the acceleration is upward and the inertial force is downward. The oil flow direction is as shown by the arrow in the figure. The oil that previously filled the external volume of the roller pin ball head 3.1 falls into the cam cavity 4.3 under the action of inertial force and gravity.

[0020] Reference Figure 3 As the tappet moves upward to the middle section, the groove 1.2 connects to the oil inlet 4.2. There is a narrow opening between the pin hole 1.1 and the lower end of the pump body guide hole 4.1. The oil flow direction is shown by the arrow in the figure: the oil reaches and fills the external volume of the roller pin ball head 3.1 through the groove 1.2 and the oil guide notch 1.4. Due to the throttling effect of the narrow opening, the oil pressure outside the roller pin ball head 3.1 is between zero and the oil inlet pressure. Part of the oil enters the cam cavity 4.3 through the narrow opening, and part of the oil enters the fit gap between the roller pin 3 and the pin hole 1.1 under pressure, and then flows out from the axial gap between the tappet body 1 and the roller 2, falling into the cam cavity 4.3. At the same time, a small amount seeps into the fit gap between the roller 2 and the roller pin 3.

[0021] Reference Figure 4As the tappet moves upward to the upper section, the groove 1.2 continues to connect to the oil inlet 4.2. The narrow opening between the pin hole 1.1 and the lower end of the pump body guide hole 4.1 disappears. The oil flow direction is shown by the arrow in the figure: the oil passes through the groove 1.2 and the oil guide notch 1.4 to reach the external volume of the roller pin ball head 3.1. The oil pressure outside the roller pin ball head 3.1 is basically equal to the oil inlet pressure. Under the action of pressure, the oil enters the fitting gap between the roller pin 3 and the pin hole 1.1, and then flows out from the axial gap between the tappet body 1 and the roller 2, falling into the cam cavity 4.3. At the same time, a small amount also seeps into the fitting gap between the roller 2 and the roller pin 3. This stroke ends at the top dead center.

[0022] Figure 3 and Figure 4 Oil enters the mating gap between roller pin 3 and pin hole 1.1 from outside the ball head 3.1 of the roller pin. If there are particles in the oil, since the particles can only contact the ball surface and cannot contact the outer diameter of the roller pin 3, they cannot be drawn into the mating gap by the linear velocity of the outer diameter. When the tappet descends to the point where the ball head 3.1 of the roller pin is exposed into the cam cavity 4.3, the particles fall into the cam cavity 4.3 and flow back to the diesel engine oil pan, and are eventually intercepted by the oil filter.

[0023] After the tappet reaches its upper limit, it returns downward, its position from... Figures 4 to 3 Then Figure 2 The direction of oil flow is also shown by the arrow in the figure.

[0024] Figure 5 This describes the changes in external oil pressure at the roller pin ball head 3.1 during the tappet's upward stroke. At the lower section, the pressure is zero, and the oil outside the roller pin ball head 3.1 falls into the cam cavity 4.3 under the influence of inertia and its own weight, generating a flow rate Q1. In the middle section, the pressure rises from zero to the pressure at the oil inlet 4.2, and the oil flow rate falling into the cam cavity 4.3 is Q2. At the upper section, the pressure remains at the oil inlet 4.2, and the oil flow rate falling into the cam cavity 4.3 is Q3.

[0025] Reference Figure 6 The total oil flow rate Q consists of three parts: Q1 + Q2 + Q3, where Q1 is... Figure 2 The oil flow rate indicated by the middle arrow is the product of the external volume of the roller pin ball head 3.1 and the tappet's movement frequency, and is directly proportional to the rotational speed. The slope of the flow rate curve is directly proportional to the external volume of the roller pin ball head 3.1, and this volume can be changed to meet the demand; Q2 is... Figure 3 The oil flow rate indicated by the arrow pointing to camshaft cavity 4.3 is proportional to the mid-lift, and can be adjusted by changing the mid-lift. If the flow rate is too high, the mid-lift can be reduced until it reaches zero; Q3 is... Figure 4The arrow pointing from the middle to the cam chamber 4.3 indicates the oil flow rate generated. The flow time ratios of Q2 and Q3 are constant and independent of engine speed, resulting in a constant flow rate. The trend of the total oil flow rate Q increasing with engine speed matches the trend of the total frictional power and heat generation of the oil pump increasing with engine speed, achieving energy saving.

Claims

1. A pressure lubrication tappet for a common rail pump, comprising a tappet body (1), a roller (2), and a roller pin (3); the roller pin (3) is inserted into a pin hole (1.1) in the tappet body, and the roller (2) is supported on the roller pin (3); the outer diameter of the tappet body (1) has an axial guide groove (1.3) in the direction perpendicular to the roller pin, and the cylindrical head of a guide pin (5) screwed into the pump body (4) is inserted into the guide groove (1.3); the upper part of the outer diameter of the tappet body (1) has a ring groove (1.2), characterized in that... The outer diameter of the tappet (1) has an oil guide notch (1.4) between the ring groove (1.2) and the pin hole (1.1) to connect the ring groove (1.2) and the roller pin ball head (3.1); The ring groove (1.2) is isolated from the guide groove (1.3); The external volume of the roller pin ball head (3.1) only leads to the cam cavity (4.3) in the lower section of the tappet lift. The oil that filled the external volume of the roller pin ball head (3.1) last time fell into the cam cavity (4.3) under the action of inertia and gravity. The external volume of the roller pin ball head (3.1) is simultaneously connected to the cam cavity (4.3) and the oil inlet (4.2) in the middle of the tappet's stroke. The ring groove (1.2) is connected to the oil inlet (4.2). There is a narrow opening between the pin hole (1.1) and the lower end of the pump body guide hole (4.1). The oil reaches and fills the external volume of the roller pin ball head (3.1) through the ring groove (1.2) and the oil guide notch (1.4). Due to the throttling effect of the narrow opening, the oil pressure outside the roller pin ball head (3.1) is between zero and the oil inlet pressure. Part of the oil enters the cam cavity (4.3) through the narrow opening, and part of the oil enters the fitting gap between the roller pin (3) and the pin hole (1.1) under pressure. Then it flows out from the axial gap between the tappet body (1) and the roller (2) and falls into the cam cavity (4.3). At the same time, a small amount seeps into the fitting gap between the roller (2) and the roller pin (3). The external volume of the roller pin ball head (3.1) only leads to the oil inlet (4.2) in the upper section of the tappet lift. The narrow opening between the pin hole (1.1) and the lower end of the pump body guide hole (4.1) disappears. The oil reaches the external volume of the roller pin ball head (3.1) through the ring groove (1.2) and the oil guide notch (1.4). The oil pressure outside the roller pin ball head (3.1) is equal to the oil inlet pressure. Under the action of pressure, the oil enters the fitting gap between the roller pin (3) and the pin hole (1.1), and then flows out from the axial gap between the tappet body (1) and the roller (2), falling into the cam cavity (4.3). At the same time, a small amount seeps into the fitting gap between the roller (2) and the roller pin (3).

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