JP2959333B2 - Fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine, for example.

[0002]

2. Description of the Related Art This type of fuel injection pump is generally
It has a plunger that reciprocates along the axis while rotating around the axis in the cylinder, and when the volume of the pressure chamber formed by the plunger tip and the cylinder increases, fuel is sucked from the pump chamber into the pressure chamber, When the volume of the pressure chamber is reduced, the fuel in the pressure chamber is pumped to the fuel injection valve of each cylinder via a fuel supply passage formed inside the plunger and a delivery passage formed in the cylinder wall. The pumping of the fuel is performed only when the spill passage connecting the fuel supply passage and the outer wall surface of the plunger in the pump chamber is closed in the pump chamber by a spill ring fitted to the outer wall surface of the plunger. By moving the ring in the axial direction, the amount of fuel pumped can be varied.

Since a gap of a predetermined size is provided between the outer wall surface of the plunger and the inner wall surfaces of the cylinder and the spill ring to enable sliding, a small amount of fuel is supplied during fuel feeding. Leaks occur. Accordingly, the position control of the spill ring for determining the fuel pumping amount is performed in consideration of the occurrence of a predetermined amount of internal leakage. However, since the viscosity of the fuel decreases as the temperature increases, the internal leakage amount of the fuel passing through a gap of a predetermined size considerably increases at a high engine temperature, and a desired amount of fuel is pumped for each engine operating state. However, it is necessary to consider the fuel temperature when controlling the position of the spill ring, and there is a problem that the control is complicated.

In order to solve this problem, Japanese Utility Model Application Laid-Open No. 1-9
No. 3,364, describes a distributed fuel injection pump in which the plunger is formed from a material having a coefficient of linear expansion greater than that of the cylinder and spill ring. This is because at the time of high temperature of the engine, by reducing the gap between the two due to the difference in linear expansion coefficient, the internal leakage of the fuel whose viscosity decreases is maintained at a predetermined amount, without complicating the position control of the spill ring. It is intended to achieve a desired fuel pumping amount according to each engine operating state.

[0005]

When the temperature of the engine is high and the fuel temperature rises, not only does its viscosity decrease, but also
The bulk modulus is reduced, and the amount of fuel compression during pumping is increased, resulting in a substantial decrease in fuel pumping. In the above-described conventional technology, it is impossible to prevent the decrease in the fuel pumping amount at the time of high engine temperature.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fuel injection pump capable of preventing a decrease in fuel pumping amount due to a decrease in bulk modulus of fuel at a high engine temperature without complicating position control of a spill ring. To provide.

[0007]

SUMMARY OF THE INVENTION A fuel injection pump according to the present invention includes a cylinder, a plunger, and the plunger for pressurizing and pumping fuel in a pressure chamber formed by the cylinder and the plunger into a combustion chamber. Plunger reciprocating means for at least reciprocating with respect to the cylinder, a spill ring for closing a spill passage of the plunger and changing a fuel pumping amount according to its position, and a required fuel pumping amount according to each engine operating state A spill ring position changing means for changing the position of the spill ring so as to obtain a fuel injection pump,
The housing of the fuel injection pump supporting the spill ring position changing means is formed of a second material having a larger linear expansion coefficient than the first material forming the plunger, and compresses the fuel in the pressure chamber when the engine temperature is high. When the amount increases, the increase in the fuel pumping amount caused by the displacement of the spill ring via the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time is the amount of compression of the fuel. The diameter of the plunger and the supporting position of the spill ring position changing means on the housing are determined so as to offset the increase in the pressure.

[0008]

In the above-described fuel injection pump, the housing of the fuel injection pump supporting the spill ring position changing means is formed of a second material having a larger linear expansion coefficient than the first material forming the plunger. The supporting position of the diameter and spill ring position changing means on the housing is
When the compression amount of the fuel in the pressure chamber increases when the engine temperature is high, the fuel pumping amount caused by the displacement of the spill ring via the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time. Is determined so as to offset the increase in the amount of fuel compression in the pressure chamber.

[0009]

FIG. 1 shows a fuel injection pump to which the present invention is applied. Reference numeral 11 denotes a feed pump (developed by 90 degrees), which is driven to rotate by a drive shaft 12 and supplies fuel to a pump chamber 13 through a fuel filter as indicated by an arrow A. Reference numeral 14 denotes a plunger, which is a cylinder 16 formed in a housing 15.
In the bore 16a. The plunger 14 is also rotationally driven by the drive shaft 12

A face cam 21 is mounted on the plunger 14, and a cam surface of the face cam 21 and a roller 21 provided on the housing 15 are connected to the face cam 2 by a roller.
A compression spring 23 provided between the opposite surface of the housing 1 and the inner wall of the housing 15 always makes contact. Thereby, the plunger 14 reciprocates right and left while rotating.

With the reciprocation of the plunger 14, the pressure chamber 17 formed by the tip of the plunger 14 and the cylinder bore 16a expands and contracts. Plunger 14
A notch 14a corresponding to the number of cylinders is provided at the tip of the cylinder. When the pressure chamber 17 is expanded, one notch 14a communicates with the suction passage 18 communicating with the pump chamber 13 as the plunger 14 rotates. As a result, fuel is sucked into the pressure chamber 17. When the pressure chamber 17 is contracted, the notch 14a and the suction passage 18 do not communicate with each other due to the rotation of the plunger 14, and the fuel supply passage 14b formed in the plunger 14, the side wall of the cylinder 16 and the housing 15 are formed. The delivery passage 19 communicates with the selected delivery passage 19, and pressure delivery of fuel to the combustion chamber via the delivery valve 20 is realized. The delivery valve 20 is opened when a predetermined pressure is reached, and this pressure is the pressure for feeding the fuel. The Delvari passage 19 and the delivery valve 20 are formed around the plunger 14 by the number of cylinders, and enable fuel supply to each cylinder.

A spill passage 24 is formed in a portion of the plunger 14 which does not enter the cylinder 16 and extends in the diametrical direction. The spill passage 24 communicates with the fuel supply passage 14b. . A cylindrical spill ring 25 is fitted to the plunger 14 so that the spill passage 24 can be opened and closed. When the pressure chamber 17 is contracted by the plunger 14, the fuel is pumped only when the spill passage 24 is closed by the spill ring 25, and the spill passage 24 is moved with the movement of the plunger 14.
Is released from the spill ring 25 and the pressure chamber 1
The pumping of the fuel is stopped because the fuel in 7 escapes to the pump chamber 13 through the spill passage 24.

Therefore, by changing the position of the spill ring 25, the amount of fuel pumped into each combustion chamber can be controlled. The spill ring 25 is connected to the control lever 2
6 is engaged with a projection 27 fixed to a lower portion of the control lever 6, and the position of the control lever 26 is changed by rotating the control lever 26 around the pin 28. The control lever 26 is
When the tension lever 30 is rotationally displaced by being pressed by a governor sleeve 41 described later, the tension lever 30 is pressed by a leaf spring 29 to be rotated.

That is, the control lever 26 stops at a position where the forces received from the governor sleeve 41 and the tension lever 30 are balanced. The tension lever 30 is connected to an adjusting lever 32 via a control spring 31, and is rotationally displaced according to the rotational position of the adjusting lever 32. The governor sleeve 41 moves left and right while being guided by the governor shaft 42. The governor shaft 42 is rotatably supported around the axis by the housing 15, and is driven to rotate by a gear 43 fixed to the shaft 42 meshing with a gear 44 fixed to the drive shaft 12 and rotating. In a holder 45 provided on the governor shaft 42, a fly weight 46 that spreads outward due to centrifugal force generated by rotation of the shaft 42 is accommodated, and the governor sleeve 41 is engaged with the fly weight 46. When the governor shaft 42 rotates and the fly weight 46 spreads, the governor sleeve 41 is displaced with this, and the control lever 26 is pressed.

In this way, the position of the spill ring 25 is changed to control the fuel pumping amount, that is, the fuel injection amount, while the timer piston 61 is displaced in accordance with the pressure in the pump chamber 13 to change the fuel pumping timing, That is, the fuel injection timing is controlled. The timer piston 61 is slidably housed in a bore 62 formed below the housing 15. The pressure receiving chamber 63 formed between the right end face of the timer piston 61 and the bore 62 is always in communication with the pump chamber 13 through a passage 64, and is provided between the left end face of the timer piston 61 and the end face of the bore 62. A timer spring 65 is provided. The timer piston 61 is connected to the roller 22 via a lever 66, and stops at a position where the pressure in the pressure receiving chamber 63 and the elastic force of the timer spring 65 are balanced to determine the position of the roller 22. That is, the timer piston 61 is displaced in accordance with the pressure in the pump chamber 13. For example, when the pressure in the pump chamber 13 becomes low, the timer piston 65 is urged by the timer spring 65 to be displaced toward the pressure receiving chamber 63, thereby causing the roller 22 to inject fuel. Displaced in a direction that delays the timing. The pressure in the pump chamber 13 is controlled by a governor sleeve 41.

Incidentally, as the temperature of the fuel increases, the viscosity decreases and the bulk modulus K decreases. The decrease in viscosity increases the amount of internal leakage of fuel through a gap formed around the plunger 14 with respect to the cylinder 16 and the spill ring 25, and reduces the amount of fuel pumped. Further, as shown in the graph of FIG. 2, the bulk modulus K decreases as the pressure P acting on the fuel decreases and the fuel temperature increases, and the fuel compression amount V in the pressure chamber 17 at the time of fuel pumping is expressed by the following equation ( 1)
Given by V = dP / K * V1 (1) Here, dP is a pressure change acting on the fuel, and specifically, the fuel pressure when the delivery valve 20 is opened and the pump chamber 13
It is the pressure difference with the fuel pressure inside. V1 is plunger 1
4 is the dead volume of the pressure chamber 17 at the rightmost position.

DP and V1 can be considered to be substantially constant with respect to temperature change, and the fuel compression amount dV is equal to the bulk modulus K
Is smaller, that is, as the fuel temperature is higher, it becomes larger and acts to reduce the fuel injection amount.

Since the material forming the plunger 14 has a larger linear expansion coefficient than the material forming the cylinder 16 and the spill ring 25, the gap around the plunger at high engine temperature is reduced, and the fuel whose viscosity decreases is used. Can be maintained at a predetermined amount, and a decrease in the amount of fuel pumped by this amount can be prevented. However, this alone cannot prevent a decrease in the amount of fuel pumped due to a decrease in the bulk modulus.

In the fuel injection pump shown in FIG. 1, the housing 15 is made of an aluminum casting to reduce the manufacturing cost and reduce the weight, and the plunger 14 is made of steel to obtain a predetermined strength. When the engine temperature is high, both expand thermally. Thereby, the position of the pin 28 serving as the rotation axis of the control lever 26 and the spill passage 24 of the plunger 14 are
Is displaced away from the feed pump 11. The displacement of the pin 28 depends on the housing 15 to which it is mounted.
Is made of aluminum and has a larger linear expansion coefficient than the steel material forming the plunger 14, so that the displacement is larger than the displacement of the spill passage 24. This results in shifting the position of the spill ring 25 relative to the spill passage 24 determined by the required fuel pumping amount in the current engine operating state to the right, that is, to the side of increasing the fuel pumping amount.

Therefore, the increase in the amount of fuel pumped by the displacement of the spill ring 25 is compensated for by the pressure chamber 17 when the fuel temperature is high.
The desired fuel pumping amount can be maintained by offsetting the increase in the amount of fuel compression inside. Hereinafter, a specific description will be given using a calculation formula.

Assuming that the temperature at the normal temperature of the engine is t1, the temperature at the high temperature of the engine is t2, and the fuel temperature is equal to the engine temperature, the increase dV of the fuel compression amount in the pressure chamber 17 at the high temperature of the engine is as described above. It is given by the following equation (2) using the equation (1). dV = (1 / K2-1 / K1) * dPV1 (2) Here, K1 and K2 are the bulk modulus of the fuel at each temperature.

On the other hand, the increase dV 'of the fuel pumping amount due to the displacement of the spill ring 25 is given by the following equation (3). dV '= π / 4 * Dp 2 * (ε 2 -ε 1) * L · Δt ... (3) where, D _P is the diameter of the plunger 14, epsilon ₂ is the linear expansion coefficient in the material of the housing 15, epsilon ₁ Is plunger 1
4 is a coefficient of linear expansion, Δt is a temperature difference t2−t1.
It is. L is a distance between the pin 28 and the cover of the feed pump 11 which is a reference for the displacement of the spill passage 24.
Is the length up to the mounting position.

It suffices that both are made equal, and the following equation (4) is obtained. Dp ² · L = 4dP · V1 / πΔt (ε ₂ −ε ₁ ) * (1 / K2-1 / K1) (4) The diameter D _{P of the} plunger 14 and the feed pump are set so that the equation (4) holds. By determining the length L from the cover 11 to the mounting position of the pin 28, the engine high temperature t2
Thus, it is possible to prevent a decrease in the amount of fuel pumped due to a decrease in the bulk modulus of the fuel. Also, from the engine temperature t1 to t2
Also during this period, the temperature change of the bulk modulus K is not peculiar but gradually decreases, so that the desired fuel pumping amount is maintained.

In the fuel injection pump according to the present invention, no new parts are added as compared with general ones, only the dimensions of specific parts are set, and no cost increase is required.

[0025]

As described above, according to the fuel injection pump of the present invention, the housing of the fuel injection pump which supports the spill ring position changing means forms the first plunger.
When the diameter of the plunger and the supporting position of the spill ring position changing means on the housing are high when the engine is at a high temperature and the amount of compression of the fuel in the pressure chamber is large, the second material has a larger linear expansion coefficient than the material. At this time the first and second
Since the increase in the amount of fuel pumping caused by the displacement of the spill ring via the spill ring position changing means due to the difference in thermal expansion of the material is determined so as to offset the increase in the amount of compression of the fuel, the fuel temperature Thus, a decrease in the fuel pumping amount due to an increase in the amount of fuel compression is prevented without requiring complicated control for changing the spill ring position in accordance with the pressure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection pump according to the present invention.

FIG. 2 is a graph showing a change in bulk modulus of fuel with respect to fuel temperature and working pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Feed pump 13 ... Pump chamber 14 ... Plunger 15 ... Housing 16 ... Cylinder 17 ... Pressure chamber 24 ... Spill passage 25 ... Spill ring 26 ... Control lever 28 ... Pin

Claims (1)

(57) [Claims] 1. A plunger reciprocating motion that at least reciprocates the plunger with respect to the cylinder to pressurize and pressurize fuel in a pressure chamber formed by the cylinder, the plunger, and the cylinder and the plunger into a combustion chamber. Means, a spill ring for closing the spill passage of the plunger and changing the amount of fuel pumped according to its position, and changing the position of the spill ring so as to obtain the required amount of fuel pumped according to each engine operating state. Wherein the housing of the fuel injection pump supporting the spill ring position changing means is formed of a second material having a larger linear expansion coefficient than the first material forming the plunger. And
When the compression amount of the fuel in the pressure chamber becomes large at the time of the engine high temperature, the displacement of the spill ring via the spill ring position changing means due to the difference in thermal expansion between the first and second materials at this time causes. A fuel injection method comprising: determining a diameter of the plunger and a support position of the spill ring position changing means on the housing so that an increase in the fuel pumping amount offsets an increase in the compression amount of the fuel. pump.