JP2005113786A - Engine choke mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine choke mechanism capable of providing good startability in a wide temperature range by automatically opening and closing a choke valve at an appropriate timing corresponding to engine temperature. <P>SOLUTION: This choke mechanism is provided with a diaphragm actuator 10 actuating a choke valve 5 from a closed valve position to an open valve position by negative pressure transmitted to a negative pressure chamber 14 via a negative pressure passage 20 from an intake air passage 3. A negative pressure transmission amount control part 25 provided with a first negative pressure passage 26, a second negative pressure passage 27 of which effective section area of a passage is set smaller than that of the first negative pressure passage 26 and in parallel with the first negative pressure passage 26, and a negative pressure passage switching valve 28 constructed to selectively open the first negative pressure passage 26 and the second negative pressure passage 27 and opening the first negative pressure passage 26 when engine temperature detected by a temperature detection part 30 is high and opening the second negative pressure passage 27 when engine temperature detected by a temperature detection part 30 is low, is installed in a middle of the negative pressure passage 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine choke mechanism including a diaphragm actuator that opens and closes a choke valve by a negative pressure in an intake passage.

  Conventionally, carburetor-type engines have been widely used as prime movers for generators, work machines, off-road vehicles (golf cars and utility vehicles), and this type of carburetor-type engine. In an engine, generally, a good startability at a low temperature or in a cold state is ensured by opening and closing a choke valve provided in a carburetor or an air cleaner.

  As this type of engine choke mechanism, for example, Patent Document 1 discloses a technique for automatically opening a choke valve, which is manually operated to the fully closed position when starting the engine, to the fully open position by the biasing force of the choke spring. In addition, there is a technology for controlling the operation when the choke valve is opened from the fully closed position by the urging force of the choke spring with an oil damper using a damper oil whose viscosity increases as the temperature decreases. It is disclosed.

By the way, in an engine, it is desirable to fully open and close the choke valve in order to reduce the burden on the operator. Thus, as a technique for fully automating the opening and closing of the choke valve, for example, a choke mechanism (auto choke mechanism) shown in FIG. 7 has been proposed. In this choke mechanism, a connecting rod 101a of a diaphragm actuator 101 that is operated by a negative pressure transmitted from the intake passage 100 is connected to a choke lever 103a to form a main part. The diaphragm actuator 101 is a return spring when the engine is stopped. When the choke valve 103 is held in the closed position by the urging force of 101b and the engine is started and negative pressure is supplied to the negative pressure chamber 101c, the negative pressure stored in the negative pressure chamber 101c increases. Then, the diaphragm 101d is operated to gradually move the choke valve 103 to the valve open position, and then the choke valve 103 during engine operation is held at the valve open position.
JP 2003-201915 A

  However, the above-described auto choke mechanism has a configuration in which the choke valve is uniformly opened and closed, and thus is particularly difficult to apply to an engine of an off-road vehicle such as a golf car. That is, when the engine is started at a low temperature, the choke valve needs to be opened gradually in order to supply a rich mixture required for the stability of the operation after the start. When the engine is restarted, the choke valve needs to be opened quickly in order to prevent deterioration of operability due to over-rich of the air-fuel mixture. Therefore, when the above-described auto choke mechanism is used for an engine such as a golf car in which start / stop operations are frequently repeated, it is difficult to always achieve good startability.

  The present invention has been made in view of the above circumstances, and provides an engine choke mechanism that can automatically open and close a choke valve at an appropriate timing according to the engine temperature and obtain good startability in a wide temperature range. The purpose is to do.

  The present invention relates to an engine choke mechanism including a diaphragm actuator that operates a choke valve from a valve closing position to a valve opening position by a negative pressure transmitted from an intake passage to a negative pressure chamber through a negative pressure passage. Temperature detecting means for detecting, and negative pressure transmission amount control means that is interposed in the negative pressure passage and that reduces the amount of negative pressure transmitted to the negative pressure chamber when the engine temperature is low than when the engine temperature is low. It is characterized by that.

  In this case, the negative pressure transmission amount control means is disposed in parallel with the first negative pressure passage in the negative pressure passage, in parallel with the first negative pressure passage interposed in the negative pressure passage. A second negative pressure passage whose effective cross-sectional area is set smaller than that of the first negative pressure passage, and the first negative pressure passage and the second negative pressure passage are selectively opened. Desirably, there is provided passage switching means for opening the first negative pressure passage when the engine temperature is high and opening the second negative pressure passage when the engine temperature is low.

  Further, it is desirable to provide a check valve that prohibits the flow of gas from the intake passage side to the negative pressure chamber side in the middle of the first negative pressure passage, and further in the middle of the first negative pressure passage. It is desirable to provide a throttle hole in parallel with the check valve.

  According to the engine choke mechanism of the present invention, the choke valve can be automatically opened and closed at an appropriate timing according to the engine temperature, and good startability can be obtained in a wide temperature range.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of a choke mechanism, FIG. 2 is a diagram showing a relationship between an engine temperature and an open / close state of first and second negative pressure passages, FIG. 3 is a timing chart showing the relationship between the actuator operating pressure and the open / close state of the choke valve.

  In FIG. 1, the code | symbol 1 shows the carburetor of the general purpose engine used as prime movers, such as a generator, a working machine, and an off-road vehicle. The carburetor 1 includes a carburetor body 2. An air cleaner (not shown) communicates with an upstream side of an intake passage 3 provided in the carburetor body 2, and an intake air of an engine (not shown) is provided downstream. The port is in communication.

  A choke valve 5 that opens and closes the intake passage 3 and a throttle valve 6 that opens and closes the intake passage 3 on the downstream side of the choke valve 5 are pivotally supported in the intake passage 3. Further, in the intake passage 3, a venturi pipe 7 faces between the choke valve 5 and the throttle valve 6, and an intake negative pressure port 8 is opened near the downstream of the throttle valve 6.

  The vaporizer body 2 is also provided with a diaphragm actuator 10. The diaphragm actuator 10 has an actuator main body 11 that is internally partitioned into an atmospheric chamber 13 and a negative pressure chamber 14 by a diaphragm 12. And a communication port 16 communicating the negative pressure chamber 14 with the intake negative pressure port 8 is opened.

  In the atmospheric chamber 13, the base end portion of the connecting rod 17 is connected to the diaphragm 12 via a retainer 18. The distal end side of the connecting rod 17 extends outside the atmospheric chamber 13 through the atmospheric communication port 15, and the distal end portion is connected to a choke lever 5 b fixed to the shaft portion 5 a of the choke valve 5. .

  On the other hand, a return spring 19 is disposed in the negative pressure chamber 14, and the diaphragm 12 is biased toward the atmosphere chamber 13 by the biasing force of the return spring 19. Then, by urging the diaphragm 12 toward the atmosphere chamber 13 side, as shown by a solid line in FIG. 1, when the engine is stopped, the connecting rod 17 causes the choke lever 5b to fall down and bring the choke valve 5 to the closed position. It comes to hold.

  The communication port 16 communicates with the intake negative pressure port 8 via the negative pressure passage 20. In the middle of the negative pressure passage 20, the amount of negative pressure transmitted from the intake passage 3 to the negative pressure chamber 14 is reduced. A negative pressure transmission amount control unit 25 is interposed as a negative pressure transmission amount control means for variable control.

  The negative pressure transmission amount control unit 25 includes a first negative pressure passage 26 interposed in the negative pressure passage 20 and a second negative pressure passage 20 interposed in parallel with the first negative pressure passage 26 in the negative pressure passage 20. And a negative pressure passage switching valve 28 as a passage switching means for selectively opening the first and second negative pressure passages 26, 27 with respect to the negative pressure passage 20. Yes.

  More specifically, in the present embodiment, the first and second negative pressure passages 26 and 27 are constituted by pipes having the same diameter, and the second negative pressure passage 27 has an orifice 27a formed in the middle. Therefore, the effective sectional area is set smaller than that of the first negative pressure passage 26.

  One end of each of the first and second negative pressure passages 26 and 27 is connected to the negative pressure passage 20a on the negative pressure chamber 14 side via a three-way pipe 29, and the other end is connected to the negative pressure passage switching valve. 28 are connected to first and second connection ports 28a and 28b, respectively.

  Further, the negative pressure passage switching valve 28 is opened with a third connection port 28c connected to the negative pressure passage 20b on the intake passage 3 side, and the third connection port 28c is provided in the negative pressure passage switching valve 28. A valve body (not shown) arranged is selectively communicated with the first connection port 28a or the second connection port 28b.

  The negative pressure passage switching valve 28 is connected to a temperature measuring unit 30 as temperature measuring means for detecting the engine temperature. In the present embodiment, the temperature detection unit 30 includes a known bimetal member (not shown) configured by, for example, stacking metal plates having different thermal expansion coefficients, and the bimetal member is provided in the negative pressure passage switching valve 28. It is connected to the disc. Here, the temperature detection unit 30 is disposed adjacent to the carburetor main body 2, for example, and detects the engine temperature based on the ambient temperature of the engine by thermal deformation of the bimetal member. Note that the temperature detector may detect, for example, engine oil temperature, engine cooling water temperature, cylinder temperature, cylinder head temperature, or ambient temperature around the engine as the engine temperature. Then, the bimetal member operates the valve body in the negative pressure passage switching valve 28 according to the detected engine temperature (that is, the amount of thermal deformation of the bimetal member). In this case, the relationship between the amount of thermal deformation of the bimetal member and the operating state of the valve element is set as appropriate based on experiments or simulations in advance, whereby, as shown in FIG. When the engine temperature T is lower than T1, the first connection port 28a is closed to close the first negative pressure passage 26 having a large effective sectional area, and the second connection port 28b is replaced with the third connection port 28c. The second negative pressure passage 27 having a small effective sectional area is opened by communication. On the contrary, when the engine temperature T is higher than T1, the first connection port 28a is communicated with the third connection port 28c to open the first negative pressure passage 26 having a large effective cross-sectional area, and the second connection. The port 28b is closed to close the second negative pressure passage 27 having a small effective sectional area.

  In the choke mechanism having such a configuration, the negative pressure passage switching valve 28 communicates with the second connection port 28b and the third connection port 28c when the engine is at a low temperature. A low-temperature negative pressure transmission path that transmits negative pressure from the intake path 3 to the negative pressure chamber 14 via the second negative pressure path 27 is formed between the communication port 16 and the communication port 16.

  In this case, since the effective sectional area of the second negative pressure passage 27 is set to be smaller than that of the first negative pressure passage 26, the negative pressure of the diaphragm actuator 10 via the low temperature negative pressure transmission path during engine operation. The amount of negative pressure transmitted to the chamber 14 is small, and the negative pressure from the intake passage 3 is gradually stored in the negative pressure chamber 14. Therefore, when the engine is started at such a low temperature, the diaphragm 12 is gradually moved to the negative pressure chamber 14 side, and the choke valve 5 is gradually opened over a predetermined time as shown by a solid line in FIG. Works up to. In this way, the choke valve 5 gradually moves to the valve opening position over a predetermined time, so that a rich mixture is generated in the carburetor 1 for a predetermined time (idling time) after the engine is started at a low temperature. Thus, good engine startability can be realized.

  On the other hand, when the engine temperature is high, the negative pressure passage switching valve 28 communicates the first connection port 28a and the third connection port 28c, whereby the intake negative pressure port 8 and the communication port 16 are connected to each other. Constitutes a high temperature negative pressure transmission path for transmitting a negative pressure from the intake path 3 to the negative pressure chamber 14 via the first negative pressure path 26.

  In this case, since the effective area of the first negative pressure passage 26 is set larger than that of the second negative pressure passage 27, the negative pressure chamber of the diaphragm actuator 10 via the high temperature negative pressure transmission path during engine operation. The amount of negative pressure transmitted to 14 is large, and the negative pressure from the intake passage 3 is quickly stored in the negative pressure chamber 14. Therefore, when the engine is started at such a high temperature by restarting or the like, the diaphragm 12 is quickly moved to the negative pressure chamber 14 side, and the choke valve 5 is quickly opened as shown by a one-dot chain line in FIG. Move to position. Then, the choke valve 5 immediately moves to the valve open position in this manner, so that after the engine is started at a high temperature, the generation of the rich mixture in the carburetor 1 is immediately prohibited, and the over-rich of the mixture is prevented. Therefore, good engine startability can be realized.

  In the present embodiment, the negative pressure transmission amount control unit 25 includes the first and second negative pressure passages 26 and 27 and the negative pressure passage switching valve 28. Even if the negative pressure transmission amount control unit 25 is configured by a variable valve or the like that is interposed in the negative pressure passage 20 and variably controls the effective sectional area of the negative pressure passage 20 itself according to the engine temperature detected by the temperature detection unit 30. Good.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 4 is a schematic configuration diagram of the choke mechanism, FIG. 5 is a schematic configuration diagram of the choke mechanism showing a modification of FIG. 4, and FIG. 6 is a timing chart showing the relationship between the actuator operating pressure and the open / close state of the choke valve. In addition, in this form, the point which interposed the valve mechanism part 50 in the high temperature negative pressure transmission path differs from the above-mentioned 1st form. In addition, about the same structure, the code | symbol same as the 1st form is attached | subjected, and description is abbreviate | omitted.

  As shown in FIG. 4, the valve mechanism unit 50 includes a housing 51 interposed in the first negative pressure passage 26, and the inside of the housing 51 is on the negative pressure passage switching valve 28 side by a partition wall 52. Are partitioned into a first compartment 51a communicating with the second compartment 51b and a second compartment 51b communicating with the negative pressure chamber 14 side.

  In addition, a communication port 53 that communicates the first and second compartments 51a and 51b is opened in the partition wall 52, and the communication port 53 comes into contact with the partition wall 52 from the first partition chamber 51a side. Therefore, a check valve 54 for blocking communication between the first and second compartments 51a and 51b is provided.

  That is, the check valve 54 is swingably supported by the partition wall 52 in the housing 51, and negative pressure is supplied from the intake passage 3 to the negative pressure chamber 14 through the first negative pressure passage 26. Sometimes, the communication port 53 is opened by the action of the negative pressure to allow gas to flow from the negative pressure chamber 14 side to the intake passage 3 side, but when the negative pressure supply is stopped, the communication port 53 is closed. The flow of gas from the intake passage 3 side to the negative pressure chamber 14 side is prohibited.

  According to such a configuration, in addition to the effects obtained in the first embodiment, the pulsation negative pressure can be efficiently stored in the negative pressure chamber 14 by the action of the check valve 54 at a high temperature. By effectively utilizing the weak pulsation negative pressure immediately after the engine is started, there is an effect that the choke valve 5 can be operated to the valve opening position more promptly as shown by a one-dot chain line in FIG. Therefore, when the engine temperature is high, the generation of the rich air-fuel mixture in the carburetor 1 can be quickly prohibited, and better engine startability can be realized.

  Further, since the negative pressure once stored in the negative pressure chamber 14 is held by the action of the check valve 54, the choke valve 5 can be held in the open position even after the warmed-up engine is stopped. (Refer to the two-dot chain line in FIG. 6) The restartability at high engine temperature can be further improved. When the engine temperature decreases after the engine is stopped, the second negative pressure passage 27 is opened to the negative pressure passage 20 by the negative pressure passage switching valve 28. The pressure is released to the intake passage 3 and the choke valve 5 is operated to the closed position.

  Here, as shown in FIG. 5, the partition wall 52 of the valve mechanism unit 50 may be configured to include a throttle hole (orifice) 56 in parallel with the check valve 54 (that is, the communication port 53). By providing the throttle hole 56 in parallel with the check valve 54, the negative pressure stored in the negative pressure chamber 14 is gradually released after the engine that has been warmed up is stopped, as indicated by a one-dot chain line in FIG. 6. It is possible to hold the choke valve 5 on the open side after the engine stops for a limited time.

  In addition, this invention is not limited to the said 1st form and 2nd form, A various change is possible in the range which does not deviate from invention. For example, in each of the above-described embodiments, an example in which the temperature detection unit 30 is configured by a bimetal temperature detection unit has been described. However, the temperature detection unit 30 may be configured by a known thermowax type, and a battery is mounted. In the engine, the temperature detecting unit 30 may be configured by a known temperature sensor and an electric actuator, and the negative pressure passage switching valve 28 may be configured by an electromagnetic switching valve.

Schematic configuration diagram of a choke mechanism according to the first embodiment of the present invention. The same as above, the figure which shows the relationship between engine temperature and the opening-and-closing state of the 1st, 2nd negative pressure passage Same as above, timing chart showing relationship between actuator operating pressure and choke valve open / closed state Schematic configuration diagram of a choke mechanism according to a second embodiment of the present invention. Same as above, schematic configuration diagram of a choke mechanism showing a modification of FIG. Same as above, timing chart showing relationship between actuator operating pressure and choke valve open / closed state Schematic configuration diagram of a conventional choke mechanism

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vaporizer 2 ... Vaporizer main body 3 ... Intake passage 5 ... Choke valve 10 ... Diaphragm actuator 20 ... Negative pressure passage 25 ... Negative pressure transmission amount control part (negative pressure transmission amount control means)
26 ... First negative pressure passage 27 ... Second negative pressure passage 28 ... Negative pressure passage switching valve (passage switching means)
30 ... Temperature detector (temperature measuring means)
54 ... Check valve 56 ... Restriction hole
Agent Patent Attorney Susumu Ito

Claims (4)

In an engine choke mechanism including a diaphragm actuator that operates a choke valve from a valve closing position to a valve opening position by a negative pressure transmitted from an intake passage to a negative pressure chamber through a negative pressure passage.
A temperature detecting means for detecting the engine temperature;
And a negative pressure transmission amount control means which is interposed in the negative pressure passage and which reduces the transmission amount of the negative pressure transmitted to the negative pressure chamber when the engine temperature is low than when the engine temperature is high. Engine choke mechanism. The negative pressure transmission amount control means includes a first negative pressure passage interposed in the negative pressure passage,
A second negative pressure passage disposed in parallel with the first negative pressure passage in the negative pressure passage and having an effective cross-sectional area set smaller than that of the first negative pressure passage;
The first negative pressure passage and the second negative pressure passage are selectively opened, the first negative pressure passage is opened when the engine temperature is high, and the first negative pressure passage is opened when the engine temperature is low. 2. The engine choke mechanism according to claim 1, further comprising passage switching means for opening the second negative pressure passage.   3. The engine choke mechanism according to claim 2, further comprising a check valve for prohibiting a gas flow from the intake passage side to the negative pressure chamber side in the middle of the first negative pressure passage.   4. The choke mechanism for an engine according to claim 3, wherein a throttle hole is provided in the middle of the first negative pressure passage in parallel with the check valve.

Images