JPH0241320Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a pressure regulating valve for a distribution type fuel injection pump used in a diesel engine.

(Problems to be Solved by Prior Art and Ideas) In general, an advance device that is installed in a distribution type fuel injection pump of a diesel engine and changes the fuel injection timing in accordance with the engine rotational speed is The fuel oil pressure sent to the pump chamber from the feed pump driven by the engine rotates the roller holder that is linked to the timer piston, changing the phase of the reciprocating movement of the cam disc, and advancing or retracting the start timing of the plunger lift, thereby increasing the engine speed. It is configured to obtain an appropriate amount of advance angle corresponding to the rotational speed.

The amount of advance by such an advance device changes in proportion to the pump chamber pressure. Further, since the pump chamber pressure changes in proportion to the rotational speed of the feed pump that rotates in conjunction with the engine, the amount of advance changes in proportion to the engine rotational speed as a result. Therefore, the advance angle characteristic curve of the advance angle device in a typical distributed fuel injection pump is a straight line that has a constant slope with respect to the engine speed, as shown by the solid line in FIG.

However, depending on the performance of the engine, for example, the advance angle characteristic may be better if it is not a straight line as shown by the solid line in Figure 1, but a broken line that has multiple inflection points and changes in multiple stages. Good things happen.

In response to the above request, the applicant has previously requested
``Advance characteristic adjustment method and device for distributed fuel injection pump for internal combustion engine'' disclosed in Japanese Patent No. 62423 has been proposed. This invention provides a fuel injection pump that pressurizes and distributes fuel oil into the cylinders of an internal combustion engine using a plunger that rotates and reciprocates in relation to the engine rotational speed. The pressure in the pump chamber changes proportionally to the engine rotation speed, and this pressure becomes the input to the injection timing adjustment device that changes the advance characteristic, adjusting the injection timing in accordance with the engine rotation speed. By replacing the conventional overflow valve with a regulating valve that determines the amount of fuel oil flowing out from the pump chamber according to pressure changes, the amount of fuel oil flowing out from a predetermined pressure point changes. This makes it possible to obtain advance angle characteristics with multiple inflection points. As shown by the solid line in Figure 1, the advance angle characteristic has a steep slope in the engine's low-speed rotation range (the rotation range below the idle rotation speed), and a steep slope in the medium-speed rotation range (higher than the idle rotation speed, the maximum output rotation speed). In the low speed rotation range (lower speed range), the gradient is gentler than that in the low speed rotation range, and in the high speed rotation range (the rotation range above the maximum output speed), the gradient becomes steeper than that in the medium speed rotation range.

However, due to engine exhaust gas countermeasures, the advance angle characteristics are different from those described above, i.e., the slope is gentle in the low speed rotation range, the slope in the medium speed rotation range is more steep than that in the low speed rotation range, and the slope is medium again in the high speed rotation range. In some cases, an advance angle characteristic that is gentler than that in a high speed rotation range is required.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a pressure regulating valve for a distribution type fuel injection pump that can obtain advance angle characteristics effective in terms of exhaust gas countermeasures.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides an adjustment for a distribution type fuel injection pump that changes the advance angle characteristic of the advance angle device by controlling the pressure in the pump chamber of the distribution type fuel injection pump. The pressure valve includes a piston holder having an orifice connected to the suction side of a feed pump that pumps fuel oil into the pump chamber, and a piston holder that receives pump chamber pressure proportional to engine speed at one end and spring pressure at the other end. A piston orifice is slidably fitted in the holder and has an opening area set smaller than the opening area of the orifice to determine the amount of fuel oil flowing out from the orifice. The rate of increase in the amount of fuel oil pumped to the pump chamber is made larger than that in the rotation range other than the medium speed rotation range, so that the pump chamber pressure gradually increases at a higher rate of increase than in the rotation range other than the medium speed rotation range. The invention is characterized by comprising a piston for controlling.

(Function) Medium speed rotation range of the engine (higher than idle speed,
In the rotation range (lower than the maximum output rotation speed), the rate of increase in the amount of fuel oil pumped to the pump chamber is greater than that in the rotation range other than the medium speed rotation range, and the pump chamber pressure is lower than the rotation speed outside the medium speed rotation range. It will gradually rise at a higher rate of increase than that of the other regions.

(Embodiment) An embodiment of the pressure regulating valve of the distribution type fuel injection pump according to the present invention will be described below with reference to FIGS. 2 to 6.

FIG. 1 is a cross-sectional view of a distribution type fuel injection pump in which the pressure regulating valve of the present invention is installed. A plunger 3 is slidably fitted in the plunger 3, and a cam disk 5 is provided at one end of the plunger 3. A cam disk 5 is connected to a pump drive shaft 4 to transmit rotation.
On the other hand, a plurality of rollers 6a are arranged concentrically with the pump drive shaft 4.
The roller holder 6 supporting the pump housing 1
It is provided in a. Cam surface 5 of cam disk 5
Since the plunger 3 is pressed against the roller 6a of the roller holder 6 by the plunger spring 7, the plunger 3 rotates and reciprocates in the axial direction at the same time as the pump drive shaft 4 rotates, sucking in fuel oil in the pump chamber 8. The fuel oil is then distributed to each cylinder of the multi-cylinder fuel engine via the delivery valve 9.

Fuel oil is pumped from a fuel tank (not shown) by a fuel pump (not shown), is further pressurized by a feed pump 13 driven by a pump drive shaft 4, and is adjusted to a pressure related to the engine speed by a pressure regulating valve 22 of the present invention. The fuel oil is regulated and supplied to the pump chamber 8, and excess fuel oil is removed from the overflow valve 15.
The fuel is then returned to the fuel tank.

An advance angle device 16 is provided at the bottom of the pump housing 1a.
A pump chamber 8 is provided with a pressure regulated as described above.
The fuel oil pressure inside acts on the advance angle device 16. That is, the roller holder 6 is provided so as to be rotatable concentrically with the pump drive shaft 4, and the point of action at one end of the connecting lever 17 engages with the roller holder 6, and the point of action at the other end of the connecting lever 17 engages with the roller holder 6. is engaged with a piston 19 fitted in a cylinder 18 provided at the bottom of the pump housing 1a. The inner wall of the cylinder 18 and each end surface of the piston 19 cause the spring 20a to
The hydraulic pressure in the spring chamber 20 and the pump chamber 8, which accommodates the
A pressure oil chamber 21 is defined that acts on one end surface. Then, depending on the relationship between the spring force of the spring 20a and the fuel oil pressure in the pressure oil chamber 21, the piston 1
9 is determined, and accordingly, the circumferential position of the roller holder 6 is determined via the connecting lever 17.

Then, due to a change in the circumferential position of the roller holder 6, the circumferential phase of the pump drive shaft 4 and the contact position change, and therefore a relative change with the operating position of the plunger 3 occurs, and the pump drive shaft 4 changes. The advance angle changes with respect to the rotation angle of the shaft 4, and the injection timing changes accordingly. In Fig. 2, the feed pump 13 and the advance angle device 16 are shown for ease of understanding.
It is shown unfolded at 90°.

The pressure regulating valve 22 of the present invention has the above-mentioned pump chamber pressure control characteristic, and changes the rate of increase in the amount of fuel that is returned from the pressure regulating valve 22 to the suction side of the feed pump 13 so that the fuel oil is pumped to the pump chamber 8 under pressure. The rate of increase in the amount of fuel oil is changed in multiple steps as the engine speed increases, and as a result, the rate of increase in pump chamber pressure is changed in multiple steps. That is, in the first stage, which corresponds to the engine's low-speed rotation range (speed range below idling speed), the rate of increase in the amount of fuel oil returned is increased, and the rate of increase in the amount of oil sent to the pump chamber is decreased. In the second stage, which corresponds to the medium speed rotation range (higher than idle rotation speed and lower than maximum output rotation speed), the rate of increase in the amount of fuel returned is reduced to the low rotation speed range. , the rate of increase in the amount of oil sent to the pump chamber 8 is made larger than that in the low rotation range, and the rate of increase in the pump chamber pressure is made larger than that in the low rotation range so that it gradually increases; In the final stage corresponding to the high speed rotation range (the rotation range above the maximum output rotation speed), the rate of increase in the amount of fuel returned is made larger than that in the medium speed rotation range to moderate the rate of increase in the amount of oil sent to the pump chamber. The rate of increase in pump chamber pressure is made smaller than that in the high speed rotation range, and the rate of increase in pump chamber pressure is again made smaller than that in the medium speed rotation range, and accordingly,
The slope of the characteristic curve of the advance angle amount is also changed in the same manner as the rate of increase in the pump chamber pressure, and as a result, the advance angle characteristics as shown by the solid line in FIG. 3 are obtained.

As shown in FIG. 4, the pressure regulating valve 22 of the present invention has a piston holder 23.
3 is a housing 1a of the distribution type fuel injection pump 1;
is placed at a predetermined location. Piston holder 2
3, one end thereof communicates with the oil supply path from the feed pump 13 to the pump chamber 8, and the other end communicates with the plug 2.
6, and a piston 24 is fitted inside the piston 24 so as to be slidable and oil-tight. A spring 25 is disposed on the closed end side of the piston holder 23 to press one end surface of the piston 24, and the other end surface of the piston 24 is connected to the feed pump 13.
It receives the hydraulic pressure sent from the pump, that is, the pump chamber pressure.

A passage 27 is provided along the axis of the piston 24, and an annular groove 28 is provided on the outer periphery of the piston 24. Furthermore, a piston orifice 29 extending from the passage 27 to the annular groove 28 is drilled in the diametrical direction of the piston 24 . Furthermore, a first orifice 30 is provided in the piston holder 23 at a predetermined location for causing the fuel oil to flow out and return it to the suction side of the feed pump 13. A first orifice 30 is also provided below the first orifice 30 at a predetermined interval in parallel with the first orifice 30. Similarly, a second orifice 31 for fuel oil outflow is drilled therein. The piston holder 23 is provided with a discharge port 32 for discharging fuel oil leaking into the spring chamber 25a during operation of the pressure regulating valve 22 to the outside. A ring for preventing piston from coming off is attached to the lower opening of the piston holder 23.

In the pressure regulating valve 22 having the above configuration, the piston 24
The set load Fsp of the spring 25 is applied to the upper end surface of
However, the pump chamber pressure Pt is applied to the lower end surface, and the piston 24 is connected to the spring 25.
The force Fpi that tries to rise against the urging force of is as follows
It is expressed by equation (1).

Fpi=A×Pt...(1) However, in equation (1), A is the pressure receiving area of the piston 24. Therefore, the position of the piston 24 is determined by the balance between the set load Fsp of the spring 25 and the pressure received by the piston 24 due to the pump chamber pressure Pt.

On the other hand, the pump chamber pressure Pt is determined by the amount _QFp of fuel oil pumped by the feed pump 13 and the first and second orifices 3 of the piston holder 23 of the pressure regulating valve 22.
ΔQ (=Q _{F p−}
Q _OR ). Needless to say, this ΔQ is the amount of fuel oil sent to the pump chamber 8. Incidentally, since the Q _F p increases in proportion to the engine speed, by appropriately adjusting the Q _OR , the rate of increase of the ΔQ with respect to the engine speed, that is, the slope of the characteristic curve can be adjusted. In other words, when the rate of increase in Q _OR is smaller than that of Q _F p, the rate of increase in ΔQ increases, and the rate of increase in pump chamber pressure Pt also increases, so the slope of the advance characteristic curve also increases. Conversely, the Q _OR
If the rate of increase of is larger than that of Q _F p,
Since the rate of increase in ΔQ decreases and the rate of increase in pump chamber pressure Pt also decreases, the slope of the advance angle characteristic curve also decreases.

In this configuration, when the engine is stopped, the pressure Pt in the pump chamber 8 is 0, the piston 24 is pressed by the spring 25, and the first and second orifices 30 and 31 are both closed by the piston 24.

When the engine starts, the pump chamber pressure Pt increases as the engine speed increases, and as shown in FIG.
However, as the piston 24 moves upward, the edge 28a of the annular groove 28 of the piston 24 that was blocking the first orifice 30 passes over the lower end of the first orifice 30, and the fuel oil flows into the piston 24. It flows out from the first orifice 30 through the inner passage 27 and the piston orifice 29, and is returned to the suction side of the feed pump 13. In this case, the first orifice 3
The amount of fuel oil flowing out from 0 increases in proportion to the opening area of the first orifice 30, which increases as the edge 28a rises. Therefore, the first orifice 3
The rate of increase in the outflow amount Q _OR of fuel oil from 0 increases, and conversely, the rate of increase in the fuel oil pumped to the pump chamber 8 decreases, and accordingly, the rate of increase in the pump chamber pressure Pt decreases. Therefore, the advance angle characteristic becomes a control characteristic of the first stage corresponding to the low speed rotation range of the engine, that is, a straight line increasing with a gentle gradient as shown in the straight line section a of the solid line in FIG.

When the engine speed further increases and the piston 24 moves upward to a position where the edge 28a of the annular groove 28 matches the upper end of the first orifice 30 as shown in FIG. 5, the opening area of the piston orifice 29 becomes The opening area of the first orifice 30 is set to be smaller than the opening area of the first orifice 30, and the axial width of the annular groove 28 is set to be smaller than the opening area of the first orifice 30.
The annular groove 2 is larger than the diameter of the orifice 30.
Even if the edge 28a _of No. 8 rises, the amount Q _OR of fuel oil flowing out from the first orifice 30 is determined by the opening area of the piston orifice 29. It will be smaller than that of the step. Therefore, the rate of increase in the fuel oil pumped to the pump chamber 8 is greater than that in the first stage described above, and accordingly, the rate of increase in the pump chamber pressure Pt is greater than that in the first stage described above. gradually increases,
As a result, the advance angle characteristic becomes a second-stage piston characteristic corresponding to the medium speed rotation range, that is, a straight line with a steep slope as shown in the straight line section b of the solid line section in FIG.
Incidentally, the inflection point A in the figure is the point where the opening area of the piston orifice 29 and the opening area of the first orifice 30 become equal, as described above.

Then, as the engine speed increases further and the piston 24 moves upward as shown in FIG. Therefore, the amount of fuel oil flowing out Q _OR is the sum of the amounts of fuel oil flowing out from the first and second orifices 30 and 31. Therefore, the rate of increase in Q _OR is again the second
The increase rate of the fuel oil pumped into the pump chamber 8 becomes smaller than that in the second stage, and the pump chamber pressure increases accordingly.
The rate of increase in Pt is smaller than that in the second stage mentioned above, and as a result, the advance angle characteristic is the control characteristic of the third stage corresponding to the high speed rotation range, that is, the slope is as shown in the straight line part c of the solid line in Fig. 3. It becomes a gentle straight line. Further, an inflection point B in the figure is a point where the lower end of the piston 24 and the lower end of the second orifice 31 coincide. This third stage control characteristic, when the pump chamber pressure at the end of the second stage control characteristic is set high,
This is effective in preventing the maximum pressure value from exceeding the limit pressure of the distribution type fuel injection pump 1 due to various conditions.

(Effect of the invention) As explained above, according to the invention, in the pressure regulating valve of the distribution type fuel injection pump that controls the pressure in the pump chamber of the distribution type fuel injection pump to change the advance angle characteristic of the advance angle device. , a piston holder having an orifice connected to the suction side of a feed pump that pumps fuel oil into the pump chamber; and a piston holder that receives pump chamber pressure proportional to the engine speed at one end and spring pressure at the other end, and a The piston orifice is slidably fitted into the pump chamber and has an opening area set smaller than the opening area of the orifice to determine the amount of fuel oil flowing out from the orifice. The rate of increase in the amount of fuel oil pumped to the engine is controlled to be greater than that in the rotation range other than the medium speed rotation range, so that the pump chamber pressure gradually increases at a higher rate of increase than that in the rotation range other than the medium speed rotation range. It is characterized by comprising a piston.

Therefore, if the fuel injection timing required for exhaust gas countermeasures is optimized and engine performance is improved, and if the pump chamber pressure at the end of pump chamber pressure control in the medium speed rotation range is set high, the maximum This is extremely effective in preventing the pressure value from exceeding the limit pressure of the distribution type fuel injection pump.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the advance characteristics of a conventional pressure regulating valve, Fig. 2 is a longitudinal cross-sectional view of a main part of a distribution type fuel injection pump equipped with the pressure regulating valve of the present invention, and Fig. 3 is a diagram showing the advance characteristic of the pressure regulating valve of the present invention. 4 to 6 are cross-sectional views showing one embodiment of the pressure regulating valve according to the present invention. DESCRIPTION OF SYMBOLS 1... Distribution type fuel injection pump, 1a... Housing, 8... Pump chamber, 13... Feed pump, 22... Pressure regulating valve, 23... Piston holder,
24...Piston, 25...Spring, 29...
...Piston orifice, 30, 31...Orifice.

Claims (1)

[Scope of utility model registration request] In a pressure regulating valve of a distribution type fuel injection pump that controls the pressure in the pump chamber of the distribution type fuel injection pump to change the advance angle characteristic of the advance angle device, the pressure regulating valve is connected to the suction side of a feed pump that pressure-feeds fuel oil to the pump chamber. a piston holder having an orifice that receives pump chamber pressure proportional to engine speed at one end and spring pressure at the other end, is slidably fitted into the piston holder, and has an opening area equal to the opening area of the orifice. It has a piston orifice that is set smaller to determine the amount of fuel oil that flows out from the orifice. and a piston that controls the pump chamber pressure to gradually increase at a higher rate of increase than that in the rotation range other than the medium speed rotation range. Pressure regulating valve.