JP2014148935A - Fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply device capable of stabilizing an amount for supplying fuel to a cam chamber even during rotating a pump at a low velocity.SOLUTION: A fuel supply device 1 is provided with a first flow passage 21 and a second flow passage 22 for supplying some of fuel emitted from a low-pressure pump 3 to a cam chamber 12, and a pressure valve 24 is provided to the first flow passage 21, and a second throttle 25 with a smaller flow passage cross sectional area than that of the first throttle 23 provided to the first flow passage 21 is provided to the second flow passage 22. During rotating the pump at a low velocity, the first flow passage 21 is closed, and the required minimum amount of fuel is stably supplied to the cam chamber 12 through the second flow passage 22. During rotating the pump at a high velocity, the fuel is supplied to the cam chamber 12 from the second flow passage 22 and the first flow passage 21, so that a large amount of fuel supplied to the cam chamber 12 can be secured. Accordingly, a large amount of the fuel supplied to the cam chamber 12 can be secured during rotating the pump at the high velocity, and feed pressure can be quickly increased during rotating the pump at the low velocity. Additionally, the amount of the fuel supplied to the cam chamber 12 can be made stable during rotating the pump at the low velocity.

Description

  The present invention relates to a fuel supply device for an internal combustion engine.

As shown in FIG. 8, the conventional fuel supply apparatus 100 includes a low pressure pump 102 that pumps fuel from a fuel tank 101, and a pressurization chamber 103 to which fuel from the low pressure pump 102 is supplied. And a high-pressure pump 104 that pressurizes the fuel, and a cam chamber 105 that houses a cam that drives the high-pressure pump 104 is provided with a flow path 106 that supplies a part of the fuel discharged from the low-pressure pump 102. .
The flow path 106 is provided with a throttle 107, which is metered by the throttle 107, and the fuel supplied to the cam chamber 105 is used for lubrication or cooling of the cam or the components inside the cam chamber 105 for driving the cam. Used for.

  By the way, when the high-pressure pump 104 and the low-pressure pump 102 rotate at a high speed (especially in an operating state that exceeds the idle operation range, hereinafter referred to as a high speed), a large amount of fuel is supplied to the cam chamber 105. There is a need to. On the other hand, there is a demand to quickly increase the feed pressure of the low-pressure pump during low-speed rotation of the pump (hereinafter referred to as low speed).

  In the fuel supply device 100 shown in FIG. 8, if the flow passage cross-sectional area of the throttle 107 is small, the feed pressure of the low-pressure pump 102 increases quickly and the engine startability is improved. However, the amount of fuel supplied to the cam chamber 105 at high speed Becomes smaller. Also, if the flow passage cross-sectional area of the throttle 107 is large, a large amount of fuel can be secured to the cam chamber 105, but the increase in the feed pressure of the low-pressure pump 102 at low speed is delayed and engine startability is deteriorated. That is, as shown in FIG. 9, when it is attempted to secure the fuel supply amount to the cam chamber 105 required at high speed (hereinafter referred to as the required cam chamber fuel supply amount Qh at high speed), the feed pressure required to start the engine at the time of engine start. (Hereinafter, the engine start necessary feed pressure Ps) cannot be secured.

  Therefore, in Patent Document 1, a check valve 108 is provided downstream of the throttle 107 as shown in FIG. According to this, since the check valve 108 is closed and the flow path 106 is closed at a low speed, the feed pressure increases quickly. On the other hand, at a high speed, the check valve 108 is opened and a necessary amount of fuel is supplied to the cam chamber 105 through the throttle 107.

JP 2002-322968 A

In the technique of Patent Document 1, the fuel supply to the cam chamber 105 is stopped when the check valve 108 is closed at low speed, or the fuel is supplied while allowing leakage when the check valve 108 is closed. That is, as shown in FIG. 11, the fuel supply amount at low speed varies and is not stable.
However, fuel supply to the cam chamber 105 is necessary even at low speeds, and it is preferable to stabilize the fuel supply amount to the cam chamber 105 from the viewpoint of the reliability of the fuel supply device.

  Therefore, the present invention secures a large amount of fuel supply to the cam chamber at high speed, and stabilizes the fuel supply amount to the cam chamber at low speed in addition to increasing the feed pressure of the low-pressure pump quickly at low speed. For the purpose.

The fuel supply device of the present invention has a low-pressure pump that pumps fuel from a fuel tank, and a pressurization chamber to which fuel is supplied from the low-pressure pump, pressurizes the fuel in the pressurization chamber, and supplies the fuel to the internal combustion engine A high pressure pump.
The high-pressure pump includes a camshaft, a cam that converts the rotational motion of the camshaft into a reciprocating motion, a plunger that is driven by the cam to pressurize fuel in the pressurizing chamber, and a cam chamber that houses the cam.

  The fuel supply device is provided in parallel with the first flow path for supplying a part of the fuel discharged from the low pressure pump or the high pressure pump to the cam chamber, and is discharged from the low pressure pump or the high pressure pump. A second flow path for supplying a part of the fuel to the cam chamber, a first throttle provided in the first flow path, a pressure valve that opens and closes according to the pressure of the fuel provided in the first flow path, And a second diaphragm having a smaller channel cross-sectional area than the first diaphragm provided in the second channel.

  According to this, if the valve opening pressure is set so that the pressure valve is closed at a low speed, there is no fuel supply from the first flow path to the cam chamber at the low speed, and the second flow path from the second flow path. Fuel is supplied to the cam chamber through the throttle. The second throttle has a smaller channel cross-sectional area than the first throttle, and can ensure only the minimum amount of fuel supply required at low speeds without interfering with an increase in feed pressure at low speeds.

  At high pump speed with high feed pressure, in addition to the second flow path, fuel is supplied from the first flow path to the cam chamber via the first throttle by opening the pressure valve. Even if the size of the first throttle is set so that a large amount of fuel is supplied to the cam chamber at high speed, the pressure valve is closed at low speed, so that the increase in feed pressure at low speed is not hindered.

  Therefore, it is possible to secure a large amount of fuel supply to the cam chamber at high speeds and to quickly increase the feed pressure of the low-pressure pump at low speeds, and to stabilize the fuel supply amount to the cam chambers at low speeds.

It is a schematic diagram which shows the structure of a fuel supply apparatus (Example 1). (Example 1) which is a characteristic view which shows the relationship between a pump rotational speed and feed pressure, and the relationship between a pump rotational speed and a cam chamber fuel supply amount. (Example 2) which is a schematic diagram which shows the structure of a fuel supply apparatus. (Example 2) which is a schematic diagram of a pressure regulating valve. (Example 2) which is a characteristic view which shows the relationship between a pump rotational speed and feed pressure, and the relationship between a pump rotational speed and a cam chamber fuel supply amount. (Example 3) which is a schematic diagram which shows the structure of a fuel supply apparatus. (Example 3) which is a characteristic view which shows the relationship between a pump rotational speed and feed pressure, and the relationship between a pump rotational speed and a cam chamber fuel supply amount. It is a schematic diagram which shows the structure of the conventional fuel supply apparatus. FIG. 9 is a characteristic diagram illustrating a relationship between a pump rotation speed and a feed pressure and a relationship between a pump rotation speed and a cam chamber fuel supply amount in the fuel supply device of FIG. 8. It is a schematic diagram which shows the structure of the conventional fuel supply apparatus. FIG. 11 is a characteristic diagram illustrating a relationship between a pump rotation speed and a feed pressure and a relationship between a pump rotation speed and a cam chamber fuel supply amount in the fuel supply device of FIG. 10.

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
[Configuration of Example 1]
The configuration of the fuel supply device 1 according to the first embodiment will be described with reference to FIGS. 1 and 2.
The fuel supply device 1 is used, for example, in an accumulator fuel injection system for a diesel engine, and pressurizes fuel to supply it to a common rail (not shown). The fuel accumulated in the common rail is injected into the combustion chamber of the engine by the injector.

  The fuel supply device 1 includes a low pressure pump 3 that sucks fuel from a fuel tank 2, a high pressure pump 4 that pressurizes and pumps fuel sucked by the low pressure pump 3, and a housing.

  The low-pressure pump 3 is constituted by, for example, a well-known trochoid pump, and discharges the fuel pumped up from the fuel tank 2 and supplies it to the high-pressure pump 4. The discharge pressure of the low pressure pump 3 is referred to as feed pressure.

  The high-pressure pump 4 includes a camshaft (not shown) that is rotated by an internal combustion engine, a cam (not shown) that converts the rotational motion of the camshaft into a reciprocating motion, and a plunger 8 to which the reciprocating motion is transmitted. .

  The housing has a housing main body that houses the camshaft and the low-pressure pump 3, and a cylinder body 11 that houses the plunger 8 in a reciprocable manner.

The housing body has a cam chamber 12 for accommodating a cam, and a shaft insertion hole through which the camshaft is inserted is opened.
The cylinder body 11 has a cylinder hole in which the plunger 8 is accommodated, and a pressurizing chamber 13 in which fuel is supplied to one end portion of the cylinder hole and the internal fuel is compressed by the reciprocating movement of the plunger 8 is formed. Has been.

The fuel discharged from the low pressure pump 3 is supplied to the pressurizing chamber 13 through the metering valve 26, pressurized by the plunger 8 in the pressurizing chamber 13, and pumped to the common rail through the check valve 30. .
The metering valve 26 can control the opening and closing of the valve element 29 by the electromagnetic coil 27 and the spring 28. When the plunger 8 is lowered, the valve element 29 is opened and fuel is supplied to the pressurizing chamber 13. The fuel is pressurized in the pressurizing chamber 13 by closing the valve body 29 when the plunger 8 moves up. By adjusting the valve closing timing of the valve body 28, the fuel pressure-fed to the common rail can be metered.

  The fuel supply device 1 also includes a flow path serving as a path for pressure-feeding fuel from the fuel tank 2 to the common rail, a flow path serving as a path for returning low-pressure fuel to the fuel tank 2, and the like.

  That is, a fuel suction passage 14 connecting the fuel tank 2 and the upstream of the low pressure pump 3, a fuel supply passage 15 connecting the low pressure pump 3 and the pressurization chamber 13 of the high pressure pump 4, and the pressurization chamber 13 to the common rail. And a fuel supply passage 16 for supplying fuel, a return passage 18 for connecting the downstream of the low-pressure pump 3 and the upstream of the low-pressure pump 3 via a pressure regulating valve 17 and the like.

[Features of this embodiment]
The fuel supply device 1 of the present embodiment includes a first flow path 21 and a second flow path 22 that supply a part of fuel discharged from the low pressure pump 3 or the high pressure pump 4 to the cam chamber 12, and a first flow path 21. A first throttle 23 provided in the first flow path 21, a pressure valve 24 provided in the first flow path 21, and a second throttle 25 provided in the second flow path 22.
The first flow path 21 and the second flow path 22 are flow paths for supplying fuel to the cam chamber 12, and the supplied fuel is used for lubrication or cooling of the cam, the cam shaft, the cam shaft bearing, and the like. It is done.

The first flow path 21 is branched from the fuel supply flow path 15 and connects the cam chamber 12 and the downstream of the low pressure pump 3.
The second flow path 22 is branched from the fuel supply flow path 15 separately from the first flow path 21, and connects the cam chamber 12 and the downstream of the low pressure pump 3. That is, it is provided in parallel with the first flow path 21.

The first flow path 21 is provided with a first throttle 23 that restricts the cross-sectional area of the flow path, and a pressure valve 24 that opens and closes according to the fuel pressure downstream of the first throttle 23. The pressure valve 24 is a check valve, and the valve opening pressure P1 is set so that the valve is opened at a feed pressure higher than the necessary feed pressure Ps when starting the engine.
The second flow path 22 is provided with a second throttle 25 having a smaller channel cross-sectional area than the first throttle 23.

[Operation of fuel supply device 1]
The operation of the fuel supply device 1 will be described.
By driving the low-pressure pump 3, fuel is introduced from the fuel tank 2 into the fuel intake passage 14 and sucked into the suction side of the low-pressure pump 3. The low-pressure pump 3 pressurizes the sucked fuel to a predetermined pressure and discharges the fuel to the fuel supply passage 15. The fuel supplied to the pressurizing chamber 13 through the fuel supply flow path 15 is pressurized by the pressure feed stroke of the plunger 8. The fuel pressurized in the pressurizing chamber 13 is supplied to the common rail through the fuel supply channel 16.

A part of the fuel in the fuel supply channel 15 is supplied to the first channel 21 and the second channel 22.
When the pump pressure is lower than the valve opening pressure of the pressure valve 24, the first flow path 21 is closed by closing the pressure valve 24, and the fuel is cammed from the second flow path 22 through the second throttle 25. It is supplied to the chamber 12.
When the rotational speed of the pump increases and the feed pressure becomes higher than the valve opening pressure P1 of the pressure valve 24, the pressure valve 24 opens, and in addition to the second flow path 22, the first throttling from the first flow path 21 is performed. Through 23, fuel is supplied to the cam chamber 12.

[Effects of this embodiment]
The effect of the present embodiment will be described with reference to FIG.
According to the present embodiment, at low speed, the first flow path 21 is closed until the feed pressure reaches the valve opening pressure P1 of the pressure valve 24, but fuel is supplied from the second flow path 22 to the cam chamber 12. The For this reason, fuel can be stably supplied to the cam chamber 12 from the second flow path 22 even at a low speed. Further, the second throttle 25 has a flow passage cross-sectional area smaller than that of the first throttle 23, and is set so as to ensure a minimum fuel supply amount to the cam chamber. For this reason, even if fuel is supplied from the second flow path 22 to the cam chamber 12, the feed pressure can be increased quickly. That is, it is possible to ensure the necessary feed pressure Ps when starting the engine when starting the engine.

  Further, when the pump rotation speed increases and the feed pressure exceeds the valve opening pressure P1, the pressure valve 24 opens, and the fuel flows from the first flow path 21 through the first throttle 23 in addition to the second flow path 22. It is supplied to the cam chamber 12. For this reason, the amount of fuel supplied to the cam chamber 12 increases. For this reason, it becomes possible to secure the required cam chamber fuel supply amount Qh at high speed.

According to this, when the feed pressure is low, the minimum amount of fuel supply to the cam chamber 12 required at the low speed can be stably secured without hindering the feed pressure increase by the second flow path 22.
At high speed when the feed pressure is high, fuel is supplied from the first flow path 21 to the cam chamber 12 in addition to the second flow path 22, and a necessary fuel supply amount to the cam chamber 12 at high speed can be secured.

  Accordingly, it is possible to secure a large amount of fuel supply to the cam chamber 12 at high speed, and to stabilize the fuel supply amount to the cam chamber 12 at low speed in addition to increasing the feed pressure quickly at low speed.

[Example 2]
The configuration of the second embodiment will be described with reference to FIGS. 3 to 5 with a focus on differences from the first embodiment.
In addition, the same code | symbol as Example 1 shows the same structure, Comprising: The previous description is referred.
In the present embodiment, the pressure valve 24 is a pressure regulating valve 28 that opens and closes according to the pressure of the fuel and changes the cross-sectional area of the flow path.

As shown in FIG. 4, the pressure regulating valve 28 includes a valve body 29, a valve body 30 that houses the valve body 29 and forms a flow path, and a spring 31 that biases the valve body 29 in the closing direction.
The valve body 30 includes a guide hole 30a through which the valve body 29 reciprocates, an inlet 30b that opens into the guide hole 30a and receives the feed pressure from the valve body 29, and opens into the guide hole 30a so that fuel flows out when the valve is opened. And an outlet 30c. It opens to the peripheral wall of the outlet 30c guide hole 30a, and the opening area increases as the valve element 29 moves in the valve opening direction. That is, in the pressure regulating valve 28, the fuel supply amount to the cam chamber 12 gradually increases after the valve is opened.

When the check valve is used, the amount of fuel supplied to the cam chamber 12 suddenly increases due to the opening of the valve, so that the feed pressure may temporarily drop abruptly. However, since the fuel supply amount to the cam chamber 12 gradually increases after the pressure adjustment valve 28 is opened, the feed pressure does not change rapidly (see FIG. 5).
That is, according to the present embodiment, in addition to the same operation and effect as in the first embodiment, there is an operation and effect that a sudden change in the feed pressure accompanying the opening of the pressure valve 24 can be avoided.

Example 3
The configuration of the third embodiment will be described with reference to FIGS. 6 and 7 focusing on differences from the first embodiment.
In addition, the same code | symbol as Example 1 shows the same structure, Comprising: The previous description is referred.
The fuel supply apparatus 1 according to the present embodiment includes an addition flow path 36 that supplies a part of the fuel discharged from the low pressure pump 3 or the high pressure pump 4 to a fuel addition valve 35 that adds the fuel to the exhaust passage of the internal combustion engine.
The fuel addition valve 35 is for adding fuel upstream of the catalyst in order to maintain the activity of the catalyst that purifies the exhaust gas in the exhaust passage.

In the present embodiment, the addition flow path 36 is provided to be branched from the upstream side of the fuel supply flow path 15 from the position where the first flow path 21 and the second flow path 22 are branched. The addition channel 36 may be branched from any channel as long as the feed pressure is applied.
Since the fuel addition valve 35 is required to inject fuel at a high pressure during idle operation, it is necessary to ensure a feed pressure of a predetermined value or more in the idle operation region. This feed pressure is referred to as idle region required feed pressure Pa.

  According to the present embodiment, the valve opening pressure P1 is set to be larger than the idle region necessary feed pressure Pa, so that the feed pressure reaches the cam chamber 12 from the first flow path 21 until the idle region necessary feed pressure Pa is reached. Therefore, it is possible to ensure the required feed pressure Pa in the idling region in the idling operation region. Therefore, in the present embodiment, in addition to the operational effects of the first embodiment, there is an operational effect that the fuel pressure necessary for fuel addition can be secured in the idle operation region.

[Modification]
The first flow path 21 and the second flow path 22 may connect the upstream side of the pressurizing chamber 13 and the cam chamber 12, or may connect the downstream side of the pressurizing chamber 13 and the cam chamber 12. For example, both the first flow path 21 and the second flow path 22 may be provided so as to connect the downstream of the cam chamber 12 and the pressurization chamber 13. In the first embodiment, only the second flow path 22 may be provided so as to connect the downstream side of the pressurizing chamber 13 and the cam chamber 12.

  In the third embodiment, the first throttle 23 may not be provided, and the pressure regulating valve 28 may have a function as the first throttle.

DESCRIPTION OF SYMBOLS 1 Fuel supply apparatus, 2 Fuel tank, 3 Low pressure pump, 4 High pressure pump, 8 Plunger, 13 Pressurization chamber, 12 Cam chamber, 21 1st flow path, 22 2nd flow path, 23 1st aperture, 24 Pressure valve, 25 Second aperture

Claims (5)

A low pressure pump (3) for pumping fuel from the fuel tank (2);
A high pressure pump (4) having a pressurizing chamber (13) to which fuel is supplied from the low pressure pump (3), pressurizing the fuel in the pressurizing chamber (13), and supplying the fuel to the internal combustion engine; Prepared,
The high-pressure pump (4) includes a camshaft, a cam that converts the rotational motion of the camshaft into a reciprocating motion, and a plunger (8) that is driven by the cam to pressurize the fuel in the pressurizing chamber (13). And a fuel supply device comprising a cam chamber (12) for accommodating the cam,
A first flow path (21) for supplying a part of fuel discharged from the low pressure pump (3) or the high pressure pump (4) to the cam chamber (12);
A second flow path (in parallel with the first flow path (21)) for supplying a part of fuel discharged from the low pressure pump (3) or the high pressure pump (4) to the cam chamber (12) ( 22)
Provided in the first flow path (21), a first throttle (23);
A pressure valve (24) provided in the first flow path (21), which opens and closes according to the pressure of the fuel;
A fuel supply apparatus comprising: a second throttle (25) provided in the second flow path (22) and having a flow path cross-sectional area smaller than that of the first throttle (23). The fuel supply device according to claim 1,
The second flow path (22) is connected to the downstream side of the pressurizing chamber (13), and supplies fuel from the pressurizing chamber (13) to the cam chamber (12). Feeding device. The fuel supply device according to claim 1 or 2,
The fuel supply device according to claim 1, wherein the pressure valve (24) is a pressure regulating valve (28) that opens and closes according to the pressure of the fuel and changes a cross-sectional area of the flow path. The fuel supply device according to claim 1 or 2,
The fuel supply device according to claim 1, wherein the first throttle (23) and the pressure valve (24) are pressure adjusting valves (28) that open and close in accordance with the pressure of the fuel and change a cross-sectional area of the flow path. In the fuel supply device according to any one of claims 1 to 4,
An addition flow path (36) for supplying a part of fuel discharged from the low-pressure pump (3) or the high-pressure pump (4) to a fuel addition valve (35) that adds to the exhaust passage of the internal combustion engine is provided. The fuel supply apparatus characterized by the above-mentioned.

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