JPH077555Y2 - Advancement device for rotary fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an advancement device for a rotary fuel injection pump.

[Prior Art] The applicant previously proposed a fuel injection pump for supplying pressurized fuel to an injector (Japanese Patent Application No. 63-160393, etc.).
Such a rotary fuel injection pump is known.

By the way, in such a rotary fuel injection pump, due to the difference in the fuel flow rate between the high load operation and the low load operation, the stroke amount of the plunger that pressurizes the fuel differs depending on the load, and the injection timing varies. (The timing is delayed when the load is low, and it advances when the load is high). Therefore, conventionally, this rotary fuel injection pump is equipped with an advance device that operates proportionally according to the opening degree of the throttle lever, and it is corrected to always obtain a constant injection timing with respect to the load level. Was there.
Specifically, as shown in FIGS. 5 and 6, the rotation of the throttle lever b, which is rotatably supported by the pump casing a, causes the lever e to swing through the face cam d attached to the shaft c. , The urging force of the spring f that engages with the lever e is changed to reciprocate the timer piston g, and the rotation angle of the cam ring h that is interlocked with the timer piston g is adjusted to correct the injection timing. Kaisho
55-66629).

[Problems to be Solved by the Invention] However, when the injection timing is corrected by the conventional advance angle device, there is a problem that the injection timing becomes excessively retarded during low speed / high load operation.

This is because the above-described conventional advancement device adjusts the injection timing depending on the opening degree of the throttle lever b, but in reality, as shown in FIG. 7, the throttle lever b depends on the engine rotation speed. This is because the rate of increase or decrease in the fuel flow rate with respect to the opening degree is different, and it is desirable to change the degree of timing adjustment. That is, as shown in FIG.
During high-load operation, the fuel flow rate does not change,
If the timer piston g and the cam ring h are actuated in the retard direction with the same advance angle characteristics as at the time of high speed, the injection timing will be in the excessive retarded state.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and the purpose thereof is to provide a rotary fuel injection capable of normally adjusting the injection timing even when operating at a low speed and a high load, without making the injection timing excessively retarded. It is to provide a pump advancement device.

[Means for Solving the Problems] In order to achieve the above object, the present invention accommodates a timer piston for correcting the rotation angle of a cam ring in a retard angle advance direction in a cylinder so that the piston can reciprocate, and the piston Is divided into a retard side and an advance side, and an advance means is provided with an urging means for urging according to the opening degree of the throttle lever.
An inflow passage for introducing fuel according to the engine rotation speed is connected, and an excessive retardation preventing spring for urging the piston toward the advance side at low speed and high load is provided.

[Operation] According to the above configuration, during high-speed operation with a large fuel pressure on the retard side or low-speed / low-load operation with a small biasing force of the biasing means,
Without the timer piston engaging the over-retardation prevention spring,
The position of the timer piston is adjusted so that the urging force of the urging means and the fuel pressure are balanced, and the injection timing is normally corrected in synchronization with the opening of the throttle lever. On the other hand, during low-speed / low-load operation in which the fuel pressure is small and the biasing force of the biasing means is small, the fuel pressure and the biasing force of the excessive retardation preventing spring act on the timer piston against the biasing force of the biasing means. As a result, the injection timing is corrected normally without being in the retarded state.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

First, a rotary fuel injection pump to which the advance device is applied will be described with reference to FIG.

As shown in the drawing, a rotor shaft 11 driven by an engine is rotatably accommodated in the casing 10, and the rotor shaft 11 is
Transfer pump 12 driven by it at one end of 11
Is housed.

The transfer pump 12 pressurizes fuel from a fuel tank (not shown) to a pressure corresponding to the engine speed and discharges the fuel. The pressurized fuel passes through an inflow passage 13 formed in the casing 10. Be guided by. The inflow path 13 is opened at a predetermined angle along the radial direction of the rotor shaft 11.

A plunger hole 14 is formed through the rotor shaft 11 along its radial direction, and a pair of plungers 15, 15 are reciprocally housed in the plunger hole 14. A fuel pump chamber 16 is defined between the facing surfaces of the plungers 15, 15. Further, the rotor shaft 11 is formed with a port 17 that passes through the shaft center and communicates with the pump chamber 16, and a discharge port 18 and a charge port (not shown) that communicate with the port 17 in the radial direction. Are formed. The discharge port 18 is a fuel supply passage into the pump chamber 16 and is formed so as to sequentially coincide with the inflow passage 13. On the other hand, charging port (not shown)
Is a discharge path for discharging the fuel in the pump chamber 16 to each injector, and is formed so as to correspond to the outflow path 22 provided at every predetermined angle in the radial direction of the rotor shaft 11.

On the outside of the rotor shaft 11, the plunger 15 is
A cam ring 20 that engages with the protruding end of is rotatably supported. On the inner peripheral surface of the cam ring 20, a convex portion 21 corresponding to the number of injectors is formed in order to reciprocate the plunger 15 by its profile to pressurize the fuel in the pump chamber 16.

Therefore, when the rotor shaft 11 is driven to rotate, the fuel from the fuel tank (not shown) is constantly transferred to the transfer pump.
The pressure is increased by 12 to a pressure corresponding to the engine speed, and is guided through the inflow passage 13 in the casing 10. Then, when the discharge port 18 is coded in the inflow path 13, the fuel pressurized by the transfer pump 12 is supplied into the pump chamber 16 to discharge the fuel. When the rotor shaft 11 further rotates and the charging port (not shown) is coded in the outflow passage 22, the fuel discharged in this way is pushed by the convex portion 21 and is moved by the plungers 15, 15 to move to the pump chamber 16 It is further pressurized therein and is supplied to the corresponding injector through the outflow passage 22 to charge the fuel.

Now, in this rotary fuel injection pump, it is necessary to rotate the cam ring 20 so as to always obtain a certain injection timing for various engine speeds and load levels that change. Therefore, an advancement device as shown in FIG. 1 is attached to this pump.

As shown, the rotor shaft 11
The cylinder 23 is formed so as to penetrate in a direction perpendicular to
In the cylinder 23, a timer piston 24 that engages with the cam ring 20 and adjusts the rotation angle of the ring 20 is reciprocally guided.

On one end side (advance side) of the timer piston 24, a bottomed hole 25 is formed from the end surface of the piston 24. A valve body 26 is slidably inserted into the bottomed hole 25,
A valve chamber 27 is defined within 25. The inflow passage 13 is communicated with the valve chamber 27 so that the fuel pressurized by the transfer pump 12, that is, the fuel having a pressure proportional to the engine speed is supplied. Further, on the advance side of the timer piston 24, a biasing means 30 for biasing the timer piston 24 to the advance side in synchronization with the opening degree of the throttle lever 29 supported by the shaft 28 on the upper part of the casing 10. Is provided. The biasing means 30 is such that a face cam 31 fixed to the end of the shaft 28 and one end of the face cam 31 are engaged,
A lever 32 swingably supported around a fulcrum 32a, a spring bearing 33 that engages with the lever 32 and reciprocates in the axial direction of the cylinder 23, and a valve body 26 supported by the spring bearing 33 is always provided. The spring 34 biases the valve chamber 27 side. Thus, the valve element 26 is stopped at a position where the biasing force of the spring 34 and the fuel pressure in the valve chamber 27 are in equilibrium. The cam surface of the face cam 31 has flat portions 31a and 31b at both ends and an inclined portion 31c at an intermediate portion, as shown in FIG.

On the other hand, on the other end side (retard side) of the timer piston 24, a stopper 35 that closes the cylinder 23 is provided, and a piston chamber 36 is defined between the timer piston 24 and the stopper chamber 36.
The piston chamber 36 is communicated with the inside of the bottomed hole 25 by a through hole 37 formed in the timer piston 24. In this way, when the through hole 37 opens in the bottomed hole 25, the fuel in the piston chamber 36 flows in or out until the opening is closed by the valve body 26, and the timer piston 24 is moved and then stopped. It has become. In this embodiment, in particular, an excessive retardation preventing spring 38 for urging the timer piston 24 toward the advance side is arranged inside the piston chamber 36. The excessive retardation prevention spring 38 is composed of a compression coil spring, and is fixed to the stopper 35 so as to come into contact with the timer piston 24 when the timer piston 24 moves to the retard side by a predetermined amount. The spring constant of the over-retardation prevention spring 38 is set smaller than that of the spring 34, and when the timer piston 24 moves to the retard side by the urging force of the spring 34, the movement is not restricted. .

Next, the operation of this embodiment will be described.

(During high speed operation) Now, when the fuel pressure in the valve chamber 27 increases as the engine speed increases, the valve body 26 moves to the advance side (left side in the figure) against the biasing force of the spring 34. The opening of the through hole 37 is opened and the valve chamber 27 is opened.
The fuel inside is supplied into the piston chamber 36. Then the valve chamber
Fuel pressure in 27, fuel pressure in piston chamber 36 and spring 34
Until the urging forces of are balanced and close the opening of the through hole 37,
The timer piston 24 is moved to the advance side (left side in the figure).
Thus, during high-speed operation with a large engine speed,
The timer piston 24 is stopped at a position sufficiently separated from the excessive retardation preventing spring 38.

In this state, if the opening degree of the throttle lever 29 is increased according to the load change, the engagement position between the face cam 31 and the lever 32 changes, and the lever 32 is rotated counterclockwise in the figure to rotate the spring. The bias of 34 increases. Then, the valve body 26 is moved to the right in the figure, and passes through the opened through hole 37 to allow the piston chamber to move.
The fuel in 36 flows out, and the timer piston 24 is moved to the retard side (right in the figure) so as to close the opening again. As described above, during high-speed operation, the timer piston 24 is located at a position sufficiently separated from the over-retardation prevention spring 38, so that the timer piston 24 does not receive the biasing force of the over-retardation prevention spring 38 and The position of 24 is adjusted in synchronization only with the opening of the throttle lever 29 to obtain the advance characteristic as shown in FIG. 4A.

(During low speed operation) On the other hand, when the engine speed decreases, the fuel pressure in the valve chamber 27 decreases, and the urging force of the spring 34 moves the valve element 26 to the retard side (right side in the figure) to open the through hole. The opening of 37 is opened, and the fuel in the piston chamber 36 flows out through the through hole 37. Then, the timer piston 24 is moved to the retard side (right side in the figure) until the opening of the through hole 37 is closed by the valve body 26. Thus, during low speed operation with a low engine speed, the timer piston 24 is stopped at a position close to the excessive retardation prevention spring 38.

In this state, when the opening degree of the throttle lever 29 is increased according to the load change, the biasing force of the spring 34 is increased.
Then, in the range in which the biasing force of the spring 34 is small, the valve body 26 is moved to the right in the drawing, the fuel in the piston chamber 36 is discharged, and the timer piston 24 is further moved to the retard side, as described above. It As described above, at the time of low load with a small opening of the throttle lever 29, the amount of movement of the timer piston 24 to the retard side (right side in the figure) is also small, so the timer piston 24 prevents the excessive retardation prevention spring. The position of the timer piston 24 is adjusted in synchronization with only the opening degree of the throttle lever 29 without contacting with 38.

On the other hand, when the urging force of the spring 34 becomes a predetermined value or more, the outflow of fuel is promoted and the timer piston 24 is further moved to the retard side, and the over-retardation prevention spring 38 comes into contact with the timer piston 24 to advance the side. Energize (left in the figure). As a result, the timer piston 24 moves in the retard direction (moves to close the through hole 37).
Is suppressed by this biasing force. As described above, when the opening of the throttle lever 29 is large and the engine speed is low and the load is high, the biasing force of the spring 34 is supported by the biasing force of the excessive retardation prevention spring 38 in addition to the fuel pressure in the piston chamber 36. The outflow of fuel from the piston chamber 36 is suppressed, and the timer piston 24 is not adjusted to the excessively retarded state.

In this way, the advance characteristic is obtained as shown in FIG. 4B.

[Effect of Device] In short, according to this device, the following excellent effects are exhibited.

On the retard angle side divided by the timer piston housed in the cylinder, an over-delay prevention spring that urges the timer piston to the advance angle side at low speed and high load is provided, so the injection timing is maintained even at low speed and high load. It can be adjusted normally.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention, FIG. 2 is a partial sectional perspective view of a rotary fuel injection pump, FIG. 3 is a sectional view showing a profile of a face cam, and FIG. FIG. 5 is a side view showing a conventional advancing device attached to a rotary fuel injection pump, and FIG. 6 is a conventional advancing device. FIG. 7 is a partial cross-sectional view showing the fuel flow rate characteristic with respect to the throttle lever opening, and FIG. 8 is a view showing low-speed fuel flow rate characteristic and advance angle characteristic with respect to the throttle lever opening in the conventional example. In the figure, 11 is a rotor shaft, 13 is an inflow passage, 15 is a plunger, 16
Is a pump chamber, 20 is a cam ring, 23 is a cylinder, 24 is a timer piston, 29 is a throttle lever, 30 is a biasing means, 36
Is a piston chamber, and 38 is an excessive retardation preventing spring.

Claims (1)

[Scope of utility model registration request] Claims: 1. A timer piston for correcting the rotation angle of a cam ring in a retard angle advance direction is reciprocally housed in a cylinder, and a retard side and an advance side are defined in front of and behind the piston. The advance side is provided with an urging means for urging according to the opening degree of the throttle lever, the retard side is connected with an inflow passage for introducing fuel according to the engine rotation speed, and at the time of low speed and high load, An advancement device for a rotary fuel injection pump, which is provided with an excessive retardation prevention spring for urging the piston toward the advancement side.