JP2007192052A - Purge buffer device for internal combustion engine and evaporated fuel processing device using the same - Google Patents

Abstract

A purge buffer device capable of mitigating an increase in the concentration of purge gas introduced to an intake system at the start of a purge process.
SOLUTION: A purge gas discharged from an adsorption layer in a canister is arranged in a purge path for guiding the purge gas to an intake system of an internal combustion engine, and a fuel component in the purge gas is temporarily adsorbed by an adsorption layer 31 arranged in a case 30. In the purge buffer device 3, at the initial stage when the introduction of the purge gas into the case 30 is started, a passage characteristic is generated in the case 30 such that a part of the fuel component in the purge gas passes through the case 30 ahead of others. A flow adjustment structure is provided. The flow adjustment structure is realized, for example, by providing a step portion 31c on the outlet side end face 31b of the adsorption layer 31 and setting the path length of the adsorption layer 31 non-uniformly.
[Selection] Figure 2

Description

  The present invention relates to a purge buffer device that temporarily adsorbs a fuel component in a purge gas led from a canister to an intake system of an internal combustion engine to alleviate a change in the purge gas concentration at the start of the purge process, and an evaporative fuel process using the purge buffer apparatus Relates to the device.

2. Description of the Related Art As an evaporative fuel processing apparatus for preventing release of fuel vapor generated in a fuel tank of an internal combustion engine to the atmosphere, an apparatus for connecting a canister containing an adsorbent such as activated carbon to the fuel tank is known. When such a canister is used, there is a limit to the adsorption capacity of the adsorbent, so a purge process is required to release the fuel component from the adsorbent before the adsorbent is saturated. The purge process is generally performed by taking the atmosphere into the canister, releasing the fuel component from the adsorbent, and introducing the purge gas containing the released fuel component into the intake system of the internal combustion engine. However, when the purge process is executed, if the purge gas concentration changes abruptly at the start of the process, the air-fuel ratio control of the internal combustion engine is adversely affected. Therefore, a secondary canister is installed as a purge buffer device on the purge path for introducing the purge gas from the primary canister to the intake system of the internal combustion engine, and the fuel component in the purge gas is temporarily adsorbed to the adsorbent in the secondary canister. Thus, there has been proposed an evaporative fuel processing device that suppresses a change in the purge gas concentration introduced to the intake system (see, for example, Patent Document 1).
JP 2002-349367 A

  In the conventional purge buffer apparatus described above, the adsorption layer inside the secondary canister is configured uniformly in both the purge gas passage direction and the direction orthogonal thereto. Therefore, compared with the case where the secondary canister is not provided, the purge gas concentration is increased after the fuel component is started to be discharged from the secondary canister, even though the time when the fuel component is introduced into the intake system can be delayed. It rises rapidly, and its concentration change cannot be mitigated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a purge buffer device capable of mitigating an increase in the concentration of purge gas introduced to the intake system at the start of the purge processing, and an evaporative fuel processing device using the purge buffer device.

  The purge buffer device of the present invention is disposed in a purge path that guides the purge gas discharged from the adsorption layer in the canister to the intake system of the internal combustion engine, and temporarily absorbs the fuel component in the purge gas by the adsorption layer disposed in the case. A purge buffer device that adsorbs to the case and has a passage characteristic such that a part of the fuel component in the purge gas passes through the case in advance at the initial stage when introduction of the purge gas into the case is started. The above-described problem is solved by providing a flow adjustment structure that is generated in the case (Claim 1).

  According to the purge buffer device of the present invention, when the introduction of the purge gas into the case is started, a part of the fuel component contained in the introduced purge gas passes through the case in advance by the action of the flow adjusting structure. . For this reason, the concentration of the purge gas discharged from the case with respect to the concentration of the purge gas introduced into the case decreases in the initial stage, and then the purge gas concentration gradually increases with the progress of the purge process. Thereby, the rise in the concentration of the purge gas guided from the purge buffer device to the intake system can be mitigated.

  In one form of the purge buffer device of the present invention, the flow adjustment structure may be realized by giving a non-uniform configuration to the adsorption layer in the case (Claim 2). By making the structure of the adsorption layer itself in the case of the purge buffer device non-uniformly, a non-uniform flow is generated in the fuel component of the purge gas flowing into the adsorption layer, and a part of it is adsorbed ahead of others. Can be drained from the bed.

  There are various examples of forms in which the adsorption layer is configured non-uniformly. For example, the path length of the adsorption layer in the case with respect to the passage direction of the purge gas in the case may be set non-uniformly in a direction orthogonal to the passage direction (Claim 3). By setting the path length non-uniformly, the fuel component quickly passes through the adsorption layer in a portion where the path length is short, and the passage of the fuel component is delayed in a portion where the path length is long. In order to set the path length non-uniformly, for example, an end surface on the exit side of the adsorption layer in the case may be provided with a slope that is inclined obliquely with respect to the stepped portion or the passing direction (Claim 4). .

  Alternatively, the path length may be set non-uniformly by providing a recess in the end face of the adsorption layer in the case on the inlet side of the case (Claim 5). When such a recess is provided, not only the path length changes, but also part of the purge gas that has flowed into the recess flows into the adsorption layer along a direction different from the purge gas passage direction in the case. Thereby, a part of the fuel component in the purge gas flowing into the concave portion diffuses in a direction different from the purge gas passage direction with respect to the adsorption layer, and it takes a longer time for the diffused fuel component to pass through the adsorption layer. As a result, the initial purge gas concentration at which the purge gas is discharged from the purge buffer device further decreases. Further, the path lengths may be set non-uniformly by forming each end face of the adsorption layer in the case so as to protrude or sink toward the center of each end face. ). By giving such a shape to both end faces, the inflow direction of the purge gas into the adsorption layer and the outflow direction of the purge gas from the adsorption layer are somewhat deflected with respect to the purge gas passage direction in the case, thereby partially The fuel component can be discharged from the adsorption layer in advance.

  As another example of giving a non-uniform configuration to the adsorption layer, the configuration of the adsorption layer in the case is made non-uniform so that the passage characteristic of the fuel component changes in the direction intersecting the purge gas passage direction in the case. It may be set (claim 7). By setting the passage characteristics of the adsorption layer non-uniformly, the fuel component passes through early in some regions in the direction orthogonal to the purge gas passage direction, and the passage of fuel components in other regions is delayed. In order to set the passage characteristics of the fuel component non-uniformly, for example, a plurality of layers having different passage characteristics of the fuel component may be stacked in a direction orthogonal to the passage direction (Claim 8). Alternatively, a plurality of layers having different fuel component passage characteristics may be arranged such that their boundary surfaces are inclined with respect to the passage direction. When the boundary surface is inclined with respect to the passage direction, the ratio of each layer in the purge gas passage direction changes according to the position in the direction orthogonal to the passage direction, and the change is used to The passage characteristic from the end face on the inlet side to the end face on the outlet side can be continuously changed. The passing characteristics of the adsorption layer can be differentiated by setting at least one of the kind, particle size, and packing density of the adsorbents constituting each of the plurality of layers to be different from each other (claims). 10).

  As yet another example of giving an uneven structure to the adsorption layer, the cross-sectional area of the adsorption layer in the case in a direction orthogonal to the purge gas passage direction in the case is more downstream than the upstream side in the passage direction. The cross-sectional area of the adsorption layer may be set non-uniformly so as to expand (claim 11). When the cross-sectional area is changed in this way, the fuel component is adsorbed while diffusing to the outer peripheral side of the adsorption layer toward the downstream side in the purge gas passage direction, so that the fuel component in the purge gas discharged from the adsorption layer is absorbed. Some are discharged from the adsorbent layer ahead of others.

  In another embodiment of the purge buffer device of the present invention, the flow adjusting means may be realized by arranging a plurality of adsorption layers at intervals along the purge gas passage direction in the case. (Claim 12). Even when the adsorption layer is configured uniformly, some deviation may occur in the discharge timing of the fuel component between the central portion and the outer peripheral portion of the case. In this embodiment, the fuel component discharged in advance from the upstream adsorption layer flows into the adsorption layer on the downstream side while diffusing in the gap between the adsorption layers, and further, the fuel component is discharged at the downstream adsorption layer at the timing of discharging the fuel component. By causing the deviation, the concentration of the purge gas discharged from the case can be reduced in the initial stage.

  In still another embodiment of the purge buffer device of the present invention, the flow adjustment structure is realized by setting the purge gas passage resistance non-uniformly in a cross section orthogonal to the purge gas passage direction in the case. (Claim 13). According to this embodiment, the passage resistance is set non-uniformly, thereby causing a difference in the time required for the fuel component in the purge gas to pass through the case, thereby purging a part of the fuel component ahead of others. It can be drained from the buffer device.

  There are various examples of forms in which the purge gas passage resistance is set non-uniformly. For example, the passage resistance may be set non-uniformly by changing the configuration of the adsorption layer in the case in a direction intersecting with the passage direction of the purge gas in the case. More specifically, the passage resistance can be set non-uniformly by changing at least one of the kind, particle size, and packing density of the adsorbent constituting the adsorbing layer. Alternatively, the passage resistance may be set non-uniformly by providing a filter that contacts the adsorption layer in the case in a partial range in a direction orthogonal to the passage direction (Claim 16).

  Alternatively, the passage resistance may be set non-uniformly by providing a bypass path in the case that bypasses the adsorption layer in the case and guides part of the purge gas. When the bypass path is provided, a part of the purge gas containing the fuel component can be quickly discharged from the purge buffer device without being influenced by the adsorption action or the passage resistance of the adsorption layer. The remaining purge gas passes through the purge buffer device with a delay while receiving the adsorption action by the adsorption layer. Accordingly, the rise of the concentration can be accelerated while alleviating the rise in the purge gas concentration in the intake system. Thereby, it is possible to improve control responsiveness when performing air-fuel ratio control or the like based on the detected value or estimated value of the purge gas concentration.

  In the case of providing a bypass passage, the adsorbent of the adsorption layer is further exposed on at least a part of the wall surface of the bypass passage so that the fuel component can flow between the bypass passage and the adsorption layer in the case. (Claim 18). In this case, the purge gas passing through the bypass passage can be brought into contact with the adsorbent so that at least a part of the fuel component is adsorbed on the adsorption layer. Thereby, it is possible to quickly and surely introduce an appropriate amount of the fuel component into the intake system while keeping the concentration of the purge gas in the initial stage lower.

  When the adsorbent of the adsorbing layer is exposed to the bypass passage, the bypass passage may penetrate the adsorbing layer while meandering in a direction intersecting with the passage direction of the purge gas in the case. Alternatively, the bypass passage may penetrate the adsorption layer in an oblique direction with respect to the passage direction of the purge gas in the case (claim 20). According to these examples, the length of the bypass path can be increased. Accordingly, the contact area between the purge gas passing through the bypass and the adsorbent can be increased, thereby increasing the adsorption amount of the fuel component and further reducing the concentration of the purge gas discharged from the purge buffer device. Further, in the case where the adsorbent of the adsorption layer is exposed to the bypass path, a constricted portion may be provided in the bypass path (claim 21). By providing the constricted portion, a venturi effect is generated in the bypass passage, and the purge gas flow is stagnant on the upstream side of the constricted portion and the fuel component is adsorbed from the purge gas to the adsorption layer, while the pressure drop is downstream of the constricted portion. The fuel component is sucked into the bypass passage from the adsorption layer around the bypass passage. As a result, an appropriate amount of the fuel component can be quickly and reliably discharged from the purge buffer device while suppressing an increase in the purge gas concentration.

  In still another embodiment of the purge buffer device of the present invention, by restricting the flow of purge gas to a part of the end face on the inlet side of the adsorption layer in the case as compared with the other part of the end face, The flow adjustment structure may be realized (claim 22). According to this embodiment, since the inflow of the purge gas to a part of the end face on the inlet side of the adsorption layer is restricted, the flow rate or flow rate of the purge gas flowing into the end face on the inlet side becomes non-uniform. As a result, the time required for the fuel component in the purge gas to pass through the adsorption layer causes a shift corresponding to the difference in flow rate or flow rate. Therefore, a part of the fuel component can be discharged from the purge buffer device ahead of others.

  There are various examples of forms for limiting the inflow of purge gas. For example, the flow of the purge gas into a part of the end surface may be limited by bringing a part of the end surface on the inlet side into close contact with the inner surface of the case (claim 23). Alternatively, the inlet of the purge gas may be restricted to a part of the end face by providing the case with an inlet projecting into the case and having a smaller diameter than the end face on the inflow side (claim 24).

  A fuel vapor processing apparatus according to the present invention includes a canister having an adsorption layer that adsorbs a fuel component in fuel vapor, and a purge that opens and closes a purge path that connects a purge gas discharged from the adsorption layer of the canister and an intake system of an internal combustion engine. And any one of the purge buffer devices described above is connected to a purge path between the adsorption layer of the canister and the purge valve (claim 25). According to this fuel vapor treatment apparatus, in the initial stage of starting the introduction of the purge gas from the canister to the purge buffer apparatus, the concentration of the purge gas guided to the intake system is decreased by the purge buffer apparatus, and the increase in the concentration can be mitigated. it can.

  As described above, according to the present invention, at the initial stage when the purge gas is introduced into the case of the purge buffer device, the concentration of the purge gas discharged from the case is reduced with respect to the concentration of the purge gas introduced into the case. Therefore, the increase in the concentration of the purge gas introduced to the intake system at the start of the purge process can be mitigated.

(Overall configuration of evaporative fuel treatment device)
FIG. 1 shows a fuel vapor processing apparatus for an internal combustion engine according to an embodiment of the present invention. The evaporative fuel processing device 1 includes a canister 2 and a purge buffer device 3. The canister 2 has a known configuration in which an adsorption layer 5 is provided inside a case 4 formed of resin or the like as a material. The adsorption layer 5 is configured by substantially uniformly filling an adsorbent such as activated carbon. The canister 2 has a vapor port 2a that takes fuel vapor guided from the fuel tank 6 through the vapor path 7 into one end of the adsorption layer 5 in the flow direction, and the atmosphere guided from the atmospheric path 8 through the filter 9 to the adsorption layer 5. An atmospheric port 2b for taking in the other end in the flow direction and a purge port 2c for sending the purge gas released from the adsorption layer 5 to the purge path 11 are provided. The purge buffer device 3 is also provided with an adsorption layer 31 inside the case 30, details of which will be described later.

  The purge path 11 is provided to guide the purge gas delivered from the purge port 2 c to the intake system of the internal combustion engine (hereinafter abbreviated as “engine”) 12. The downstream end of the purge path 11 is connected between a throttle valve 14 provided in the intake passage 13 of the engine 1200 and the intake manifold 15. A purge valve 16 is provided in the middle of the purge path 11, and the purge buffer device 3 is disposed between the purge port 2 c and the purge valve 16.

  When the purge valve 16 is closed, the fuel vapor generated in the fuel tank 6 is guided to the canister 2 through the vapor path 7 and the fuel component contained in the fuel vapor is adsorbed by the adsorption layer 5. On the other hand, when the purge valve 16 is opened while the engine 1200 is operating, the negative pressure generated downstream of the throttle valve 14 acts on the inside of the canister 2. As a result, the atmosphere is taken into the canister 2 from the atmosphere port 2b, and the purge gas in which the atmosphere and the fuel component released from the adsorption layer 5 are mixed passes through the purge buffer device 3 and the purge valve 16 from the purge port 2c. To the intake passage 13. The purge gas guided to the intake passage 13 is sent to the branch pipe 18 through the intake manifold 15 together with the intake air filtered by the air filter 17. A fuel injection valve 19 is provided in the branch pipe 18, and fuel is pumped to the fuel injection valve 19 from a pump unit 20 in the fuel tank 6 through a fuel path 21.

  The fuel component of the purge gas sent into the intake passage 13 is sucked into the cylinder (not shown) of the engine 1200 together with the fuel injected from the fuel injection valve 19 and used for combustion. For this reason, if the concentration of the purge gas (the value obtained by dividing the mass of the fuel component contained in the purge gas by the mass of air contained in the purge gas) changes, the air-fuel ratio of the engine 12 also changes. In particular, when the purge process is started, that is, when the purge valve 16 is opened and the introduction of the purge gas into the intake passage 13 is started, a large amount of fuel component is adsorbed in the adsorption layer 5 of the canister 2, There is a possibility that the concentration rapidly increases and the stability of the air-fuel ratio control is impaired. The purge buffer device 3 is provided in order to suppress a rapid increase in the concentration of the purge gas at the start of the purge process. In order to achieve this object, the purge buffer device 3 has a passage characteristic such that a part of the fuel component contained in the purge gas passes through the case in the early stage when the introduction of the purge gas into the case 30 is started. It has a flow adjustment structure that is generated in the case. Hereinafter, various forms of the purge buffer device 3 will be described.

(First form of purge buffer device)
The purge buffer device according to the first embodiment is an example in which a flow adjustment structure is realized by giving a non-uniform configuration to the adsorption layer 31, and more specifically, the path length of the adsorption layer 31 is changed. It is. FIG. 2 shows an example of the purge buffer device 3 according to the first embodiment. As described above, the purge buffer device 3 includes the case 30 and the adsorption layer 31 disposed inside the case 30. The case 30 is made of, for example, resin, and is formed in a cylindrical shape having a constant cross-sectional area in the axial direction. For example, a cylindrical shape such as a cylindrical shape or a rectangular tube shape can be given to the case 30. At both ends of the case 30, there are provided an inlet port 32 through which purge gas flows and an outlet port 33 through which purge gas flows out. The ports 32 and 33 are formed in a tubular shape coaxial with the center line of the case 30. The direction connecting these ports 32 and 33 corresponds to the passage direction of the purge gas. The end portions of the ports 32 and 33 on the inner surface side of the case are substantially flush with the inner surface of the case 30. That is, the ports 32 and 33 do not protrude into the case 30. The inlet port 32 is connected to the purge port 2 c of the canister 2, and the outlet port 33 is connected to the purge valve 16.

  The adsorption layer 31 is configured by filling a granular adsorbent (for example, activated carbon) so as to fill the inside of the case 30 in the radial direction. The packing density of the adsorbent is substantially uniform over the entire area of the adsorbing layer 31, and the adsorbing capacity at each part of the adsorbing layer 31 is also substantially constant. That is, when an arbitrary region is taken out from the adsorption layer 31, the amount of the fuel component that can be adsorbed by the region is substantially constant. An end surface (end surface on the inlet side) 31a on the inlet port 32 side and an end surface (end surface on the outlet side) 31b on the outlet port 33 side of the adsorption layer 31 are each formed in a planar shape orthogonal to the purge gas passage direction. . A gap is provided between the end surface 31a and the inlet port 32 so that the purge gas flowing from the inlet port 32 spreads over the entire end surface 31a. In addition, a gap is provided between the end face 31 b and the outlet port 33 so that the purge gas can flow out from the entire end face 31 b and be guided to the outlet port 33. Furthermore, in order to change the path length of the adsorption layer 31, a step portion 31 c that recedes toward the inlet port 32 along the center line of the case 30 is formed on the end surface 31 b on the outlet port 33 side.

  According to the purge buffer device 3 described above, the path length of the adsorption layer 31 is long in the portion where the step portion 31c is not provided, that is, in the region located outside the step portion 31c in the radial direction of the case 30, and the step portion 31c is The path length is shortened at the provided portion. Therefore, in the initial stage where the introduction of the purge gas from the inlet port 32 is started, that is, when the introduction of the purge gas is started from the state where the adsorption layer 31 is not adsorbing the fuel component, the vicinity of the center line (center portion) of the adsorption layer 31. The time required for the fuel component to pass through is shorter than the time required for the fuel component to pass through the outer peripheral portion of the adsorption layer 31. That is, since the fuel component from the adsorption layer 31 moves toward the outlet port 33 while being adsorbed by the adsorption layer 31, the time for the fuel component to pass through the outer peripheral portion is shorter than the central portion where the length of the adsorption layer 31 is short. become longer. The arrows in the figure are illustrated by replacing the length of time that the fuel component passes through the adsorption layer 31 with the length of the arrows. Due to the difference in the time required for the fuel component to pass through the adsorption layer 31, a part of the fuel component in the purge gas introduced from the inlet port 32 passes through the inside of the apparatus ahead of the others, and the outlet port 33. Spill from. Therefore, at the initial stage where the introduction of the purge gas is started, the concentration of the purge gas discharged from the outlet port 33 is suppressed to be lower than the concentration of the purge gas introduced from the inlet port 32, that is, the purge gas discharged from the canister 2. The concentration of the purge gas discharged from the outlet port 33 gradually increases, and if the adsorption layer 31 is saturated, the concentration becomes equal to the concentration of the purge gas discharged from the canister 2.

  FIG. 3 exemplifies the change in the concentration of the purge gas discharged from the purge buffer device 3 of the present embodiment. The solid line A indicates the concentration change in the purge buffer device 3 of the present embodiment, and the dotted line B indicates the purge buffer device 3. In other words, changes in the concentration of the purge gas discharged from the purge port 2c of the canister 2 are shown. The origin in the figure corresponds to the start time of the purge process, that is, the time when the purge valve 16 is opened and the discharge of the purge gas from the adsorption layer 5 of the canister 2 is started. Further, when the step portion 31c is omitted and the end surface 31b of the adsorption layer 31 on the outlet port 33 side is formed on a plane perpendicular to the purge gas passage direction over the entire surface, the change in the concentration of the purge gas discharged from the purge buffer device Is shown by a one-dot chain line C. As is apparent from this figure, when the purge buffer device 3 is not present, the purge gas concentration rapidly rises in a short time from the start of the purge process, whereas when the purge buffer device 3 of this embodiment is interposed. Increases the purge gas concentration slowly.

  The step 31c is not limited to the center line of the case 30 and may be provided at an appropriate position. For example, as shown in FIG. 4, the step portion 31 c may be disposed on a part of the outer peripheral portion of the adsorption layer 31. A plurality of step portions 31c may be provided. Alternatively, as shown in FIG. 5, even if the path length in the passing direction of the adsorption layer 31 is set non-uniformly by giving the end surface 31b of the adsorption layer 31 a gradient inclined obliquely with respect to the passing direction of the purge gas. Good. You may combine the step part 31c and the gradient of the end surface 31b.

(Second form of purge buffer device)
The purge buffer device according to the second embodiment is another example in which a flow adjustment structure is realized by providing a non-uniform configuration to the adsorption layer 31. More specifically, the passage characteristic of the fuel component is the passage of the purge gas. The structure of the adsorption layer 31 is set non-uniformly so as to change in a direction crossing the direction. FIG. 6 shows an example of the purge buffer device 3 according to the second embodiment. In the purge buffer device 3 of FIG. 6, the adsorption layer 31 is formed in a two-layer structure in which a first layer 31A and a second layer 31B are combined in a direction perpendicular to the purge gas passage direction. The first layer 31A and the second layer 31B have different fuel component passage characteristics. For example, the type of adsorbent constituting each layer is selected so that the second layer 31B has a larger amount of fuel component adsorbed per unit volume than the first layer 31A, thereby allowing each layer 31A, 31B to pass. Differences in characteristics are given. Alternatively, instead of the amount of adsorption, the type of adsorbent of each layer 31A, 31B may be selected so that the purge gas passage resistance is greater in the second layer 31B than in the first layer 31A. The end faces 31a and 31b of the adsorption layer 31 are formed in a uniform plane orthogonal to the purge gas passage direction, and the path lengths in the passage direction of the first layer 31A and the second layer 31B are equal to each other.

  According to the purge buffer device 3 of the present embodiment, the time required for the fuel component in the purge gas to pass through the adsorption layer 31 in the initial stage where the introduction of the purge gas from the inlet port 32 is started is greater in the first layer 31A. It becomes shorter than the second layer 31B (see the arrow in the figure). Accordingly, a part of the fuel component of the purge gas introduced from the inlet port 32 passes through the inside of the apparatus and flows out from the outlet port 33 in advance. As a result, the concentration of the purge gas flowing out from the outlet port 33 at the initial stage where the introduction of the purge gas is started can be gradually increased as shown by the solid line A in FIG. Note that the difference in the passage characteristics of the fuel component between the first layer 31A and the second layer 31B can be realized by other than the type of adsorbent. For example, even when the same type of adsorbent is used, by changing the particle size or packing density, the adsorption amount of the fuel component per unit volume in each layer 31A, 31B or the passage resistance of the purge gas is changed. Thereby, a difference can be given to the time for the fuel components to pass through them. That is, the purge buffer device 3 of the present embodiment is an embodiment in which the flow adjustment structure is realized by changing the configuration of the adsorption layer 31 in a direction intersecting the purge gas passage direction to set the purge gas passage resistance non-uniformly. It corresponds to. The adsorbing layer 31 is not limited to a two-layer structure, and may have a laminated structure of three or more layers. The passage characteristic of the adsorption layer 31 may be continuously changed in a direction orthogonal to the purge gas passage direction.

(Third embodiment of purge buffer device)
The purge buffer device according to the third embodiment is an example in which the flow adjustment structure is realized by setting the passage resistance of the purge gas non-uniformly in a cross section perpendicular to the passage direction of the purge gas, and more specifically, The passage resistance is set non-uniformly using a filter that contacts the adsorption layer 31 in a part of the range. FIG. 7 shows an example of the purge buffer device 3 according to the third embodiment. In the purge buffer device 3 of FIG. 7, a filter 34 that provides ventilation resistance to the purge gas is superimposed on a part of the end surface 31a on the inlet port 32 side of the adsorption layer 31 so that the adsorption layer 31 is in the passage direction. The first layer 31A and the second layer 31B are substantially divided with respect to the orthogonal direction. However, the kind, particle size, and packing density of the adsorbent used for the adsorption layer 31 may be the same as those in the first embodiment. The ventilation resistance of the filter 34 may be set as appropriate.

  According to the purge buffer device 3 of the present embodiment, the flow rate of the purge gas per unit area flowing into the first layer 31A is larger than the flow rate per unit area of the purge gas flowing into the second layer 31B. That is, there is a difference in the flow rate of the purge gas that passes through the adsorption layer 31 in the direction orthogonal to the purge gas passage direction. A similar difference occurs in the flow rate of the purge gas flowing into the adsorption layer 31. Therefore, even if the kind, particle size, and density of the adsorbent in the first layer 31A and the second layer 31B are the same, the adsorption of the fuel component in the first layer 31A proceeds earlier than the adsorption in the second layer 31B. As a result, the time required for the fuel component to pass through the first layer 31A is shorter than that of the second layer 31B, and a part of the fuel component of the purge gas introduced from the inlet port 32 precedes the others. It flows out of the outlet port 33 through the inside of the apparatus. As a result, the concentration of the purge gas flowing out from the outlet port 33 at the initial stage where the introduction of the purge gas is started can be gradually increased as shown by the solid line A in FIG. Note that the filter 34 is omitted, and as described in the second embodiment, each layer 31A, the first layer 31A and the second layer 31B are provided with a difference in the particle size, packing density, and the like of the adsorbent. Even when a difference occurs in the passage resistance of the purge gas at 31B, a difference also occurs in the flow rate or flow rate of the purge gas. Further, the filter 34 of the purge buffer device 3 of the present embodiment restricts the flow of the purge gas into a part of the end surface 31a on the inlet side of the adsorption layer 31 as compared with other parts of the end surface 31a, thereby adjusting the flow adjustment structure. It also functions as a means for realizing. The filter 34 may be any filter that can resist the passage of the purge gas and limit the amount of the inflow, and may be configured of a material having fine through holes such as a non-woven fabric that is not visible. Alternatively, it may be a member having a large number of visible through holes having a visible inner diameter such as punching metal.

(Fourth Embodiment of Purge Buffer Device)
The purge buffer device of the fourth embodiment is an example in which the flow adjustment structure is realized by setting the passage resistance of the purge gas non-uniformly within a cross section orthogonal to the passage direction of the purge gas. The inside of the case is configured such that a part of the purge gas flows around the adsorption layer. FIG. 8 shows an example of the purge buffer device 3 according to the fourth embodiment. In the purge buffer device 3 of FIG. 8, a bypass path 35 that penetrates the adsorption layer 31 is provided inside the case 30. The adsorbent of the adsorption layer 31 may be exposed on at least a part of the wall surface of the bypass path 35 so that the fuel component can flow between the bypass path 35 and the adsorption layer 31. For example, by arranging a tube having a large number of through holes with an inner diameter through which the adsorbent cannot pass so as to penetrate the adsorbing layer 31, the adsorbent can be exposed on the wall surface while forming the bypass path 35. Alternatively, the bypass path 35 and the adsorbent of the adsorption layer 31 may be completely partitioned by a partition wall or the like so that the purge gas cannot flow. The end surfaces 31a and 31b of the adsorption layer 31 are formed in a plane perpendicular to the purge gas passage direction, and a single kind of adsorbent is filled between the end surfaces 31a and 31b at a substantially constant density. ing. Accordingly, the passage characteristics of the fuel component in each part of the adsorption layer 31 are substantially constant.

  According to the purge buffer device 3 of the present embodiment, at the initial stage when the introduction of the purge gas from the inlet port 32 is started, a part of the purge gas flows out of the adsorption layer 31 and flows out from the bypass path 35 to the outlet port 33, and the rest Gas flows into the adsorption layer 31. Since the fuel component of the purge gas that has flowed into the adsorption layer 31 travels to the outlet port 33 while being adsorbed by the adsorbent, the time required for the fuel component to pass through the adsorption layer 31 is the time required for the fuel component to pass through the bypass path 35. Longer than. For this reason, a part of the fuel component of the purge gas introduced from the inlet port 32 passes through the inside of the apparatus prior to others and flows out from the outlet port 33. Therefore, the concentration of the purge gas flowing out from the outlet port 33 in the initial stage of introduction of the purge gas can be gradually increased as shown by the solid line A in FIG.

  In addition, since at least a part of the fuel component passing through the bypass passage 35 passes through the case 30 without being adsorbed by the adsorption layer 31, the fuel at the outlet port 33 starts from the time when introduction of the purge gas is started at the inlet port 32. The time lag until the outflow of components is reduced compared to the first to third embodiments described above. Therefore, as shown by the solid line A ′ in FIG. 9, the rising timing of the purge gas concentration immediately after the start of the purge process can be advanced compared to the broken line A indicating the increase in the purge gas concentration in the first embodiment or the like ( (See part D in the figure). Therefore, when the purge gas concentration is learned and the air-fuel ratio of the engine 1200 is feedback controlled, the learning effect appears earlier and the stability of the air-fuel ratio control of the engine 1200 is improved. The bypass path 35 may be provided at an appropriate position, and the number thereof may be two or more. The bypass path 35 is not limited to a shape extending linearly in the purge gas passage direction, and may be formed in an appropriate shape. The cross-sectional area of the bypass passage 35 may be changed as appropriate. By adjusting the cross-sectional area, passage resistance, and the like of the bypass passage 35, the change in the purge gas concentration can be adjusted as appropriate.

(Fifth embodiment of purge buffer device)
The purge buffer device according to the fifth embodiment is still another example in which a flow adjustment structure is realized by giving a non-uniform configuration to the adsorption layer 31. More specifically, the cross-sectional area of the adsorption layer is equal to that of the purge gas. The cross-sectional area is set non-uniformly so as to expand on the downstream side rather than the upstream side in the passing direction. FIG. 10 shows an example of the purge buffer device 3 according to the fifth embodiment. In the purge buffer device 3 of FIG. 10, the case 30 is formed in a shape in which the cross-sectional area gradually increases as it goes from the inlet port 32 to the outlet port 33. The outer periphery of the adsorption layer 31 is in close contact with the inner surface of the case 30 over the entire periphery. The end surfaces 31a and 31b of the adsorption layer 31 have a planar shape perpendicular to the purge gas passage direction (in this case, the direction connecting the inlet port 32 and the outlet port 33), and the packing density of the adsorbent on the end surfaces 31a and 31b is as follows. It is almost constant. The adsorption capacity in each part of the adsorption layer 31 is also substantially constant. Similar to the first embodiment, gaps are provided between the end faces 31a and 31b and the inlet port 32 and the outlet port 33.

  According to the purge buffer device 3 of the present embodiment, the cross-sectional area of the adsorption layer 31 gradually increases from the inlet port 32 toward the outlet port 33. Therefore, in the initial stage where the introduction of the purge gas from the inlet port 32 is started, The purge gas moves to the outlet port 33 while diffusing to the outer peripheral side in the adsorption layer 31. For this reason, the amount of fuel component adsorbed by the adsorption layer 31 increases toward the outlet port 33 and the purge gas concentration gradually decreases, and the concentration of the purge gas flowing out from the outlet port 33 at the initial stage of introducing the purge gas becomes the inlet port 32. This is lower than that of the purge gas flowing in. That is, a part of the fuel component of the purge gas introduced from the inlet port 32 passes through the adsorption layer 31 and flows out from the outlet port 33 ahead of others. Therefore, at the initial stage where the introduction of the purge gas is started, the concentration of the purge gas flowing out from the outlet port 33 can be gradually increased as shown by the solid line A in FIG.

(Sixth embodiment of purge buffer device)
The purge buffer device according to the sixth embodiment is an example in which the flow adjustment structure is realized by setting the path length and the cross-sectional area of the adsorption layer 31 non-uniformly. FIG. 11 shows an example of the purge buffer device 3 according to the sixth embodiment. In the purge buffer device 3 of FIG. 11, the case 30 is formed in a cylindrical shape having a constant cross-sectional area, as in the first embodiment. The adsorption layer 31 is provided so that the outer peripheral portion of the end surface 31a on the inlet port 32 side is in close contact with the end surface on the inlet port 32 side of the case 30, and the purge gas from the inlet port 32 is provided at the center of the end surface 31a. A recess 31 d is provided for guiding the water to the adsorption layer 31. The path length of the adsorption layer 31 is changed by the recess 31d, and the cross-sectional area of the adsorption layer 31 is expanded downstream from the upstream side in the purge gas passage direction.

  According to the example of FIG. 11, as indicated by an arrow in the drawing, the purge gas flowing in from the inlet port 32 not only flows from the recess 31d into the adsorption layer 31 along the purge gas passage direction, but also from the recess 31d. Also flows toward the outer periphery of 31. As a result, some of the fuel components of the purge gas pass through the adsorption layer 31 almost straight from the inlet port 32 toward the outlet port 33, while some of the other fuel components diffuse toward the outer periphery of the adsorption layer 31. To do. Moreover, the outer periphery of the adsorption layer 31 has no recess 31d, and the path length in the purge gas passage direction is long. For this reason, the fuel component passes through the central portion of the adsorption layer 31 at an early stage, while the fuel component passes through the outer peripheral portion of the adsorption layer 31 slowly. Therefore, at the initial stage where the introduction of the purge gas is started, the concentration of the purge gas flowing out from the outlet port 33 can be reduced and the purge gas concentration can be gradually increased.

  Note that the purge buffer device 3 of FIG. 11 is an example of an embodiment in which a flow adjustment structure is realized by restricting the inflow of purge gas by bringing a part of the end surface 31a on the inlet side of the adsorption layer 31 into close contact with the inner surface of the case 30. It corresponds to. However, as shown in FIG. 11, if the recess 31d is provided in the end surface 31a to obtain a mitigating action for increasing the concentration based on the difference in path length or cross-sectional area, the end surface 31a and the inlet port 32 of the case 30 are not connected. A gap may be provided so that the purge gas is guided to the entire end surface 31a.

(Seventh Embodiment of Purge Buffer Device)
The purge buffer device according to the seventh embodiment is still another example in which a flow adjustment structure is realized by giving a non-uniform configuration to the adsorption layer 31, and more specifically, an end surface on the inlet side of the adsorption layer and The shape of the end face on the outlet side is changed from the first form, and the path length is set non-uniformly. 12 and 13 show an example of the purge buffer device 3 according to the seventh embodiment. The purge buffer device 3 of FIG. 12 is formed in a cone shape (for example, a cone shape or a pyramid shape) in which the end faces 31a and 31b in the passing direction of the adsorption layer 31 protrude toward the center of the end faces 31a and 31b. It is a thing. On the other hand, the purge buffer device 3 of FIG. 13 is formed so that the end faces 31a and 31b in the passing direction of the adsorption layer 31 are recessed in a conical shape toward the center of the end faces 31a and 31b. Since the path length of the adsorption layer 31 also changes according to these examples, a part of the fuel component can be discharged from the adsorption layer 31 ahead of others similarly to the first embodiment.

  Further, the purge gas flowing in from the inlet port 32 is deflected in a direction different from the passage direction of the purge gas connecting the inlet port 32 and the outlet port 33 due to the protrusion or depression of the end surface 31 a, and thereby the fuel taken into the adsorption layer 31. A part of the component travels toward the outlet port 33 while diffusing in a direction different from the purge gas passage direction. Furthermore, a part of the purge gas that has passed through the adsorption layer 31 due to the protrusion or depression of the end face 31b on the outlet port 33 side also flows out in a direction different from the passing direction. Due to these effects, a diffusion action of the fuel component in a direction different from the purge gas passage direction occurs, and the increase in the purge gas concentration can be mitigated in combination with the above-described difference in path length.

(Eighth embodiment of purge buffer device)
In the purge buffer device according to the eighth embodiment, the flow adjustment structure is realized by restricting the inflow of purge gas by bringing a part of the end surface 31a on the inlet side of the adsorption layer 31 into close contact with the inner surface of the case 30. It is an example. FIG. 14 shows an example of the purge buffer device 3 according to the eighth embodiment. In the purge buffer device 3 of FIG. 14, an enlarged portion 30a is formed in a portion of the case 30 in which the adsorption layer 31 is accommodated, and the adsorption layer 31 is provided so as to fill the enlarged portion 30a. The end surfaces 31 a and 31 b of the adsorption layer 31 are planes orthogonal to the purge gas passage direction, and there are gaps between the end surfaces 31 a and 31 b and the ports 32 and 33. However, these gaps are reduced in a direction orthogonal to the purge gas passage direction as compared with the end faces 31 a and 31 b of the adsorption layer 31. That is, the outer peripheral portions of the end surfaces 31 a and 31 b are covered with the inner surface of the case 30 so that the purge gas cannot flow in.

  According to the purge buffer device 3 of the present embodiment, the purge gas flows only into the central portion of the end face 31a, that is, the portion not blocked by the case 30, so the flow rate of the purge gas per unit area in the central portion of the adsorption layer 31. Is large and the flow rate is small on the outer peripheral side of the adsorption layer 31. That is, a difference occurs in the flow rate of the purge gas passing through the adsorption layer 31 in the direction orthogonal to the purge gas passage direction. Moreover, the fuel component in the purge gas that has flowed into the central portion moves in the adsorption layer 31 while diffusing to the outer peripheral side of the adsorption layer 31. As a result, the fuel component passes through the central portion of the adsorption layer 31 earlier than the outer peripheral side of the adsorption layer 31, and the concentration of the purge gas passing through the central portion is also reduced by the diffusion action. Thereby, the concentration of the purge gas flowing out from the outlet port 33 at the initial stage where the introduction of the purge gas is started can be gradually increased as shown by the solid line A in FIG. In the purge buffer device 3 of the sixth to eighth embodiments, the fuel component is diffused in a direction different from the purge gas passage direction, so that a part of the fuel component is preceded by others at the initial stage when the introduction of the purge gas is started. And is common in that it is discharged from the adsorption layer 31.

(Ninth Embodiment of Purge Buffer Device)
The purge buffer device according to the ninth embodiment is an example in which a flow adjustment structure is realized by giving a non-uniform configuration to the adsorption layer 31. More specifically, the passage characteristics of the fuel component are the same as the passage direction of the purge gas. It is the further example which set the structure of the adsorption layer 31 unevenly so that it might change in the direction which cross | intersects. FIG. 15 shows an example of the purge buffer device 3 according to the ninth embodiment. In the purge buffer device 3 of FIG. 15, the adsorption layer 31 is formed in a two-layer structure in which a first layer 31A and a second layer 31B are combined. The boundary surface 31e between the first layer 31A and the second layer 31B is inclined obliquely with respect to the purge gas passage direction. The first layer 31A and the second layer 31B have different fuel component passage characteristics. For example, the type of adsorbent constituting each layer is selected so that the second layer 31B has a larger amount of fuel component adsorbed per unit volume than the first layer 31A, thereby allowing each layer 31A, 31B to pass. Differences in characteristics are given. Alternatively, instead of the adsorption amount, the type of adsorbent for each layer 31A, 31B may be selected so that the purge gas passage resistance is smaller in the second layer 31B than in the first layer 31A. While using the same type of adsorbent for each layer 31A, 31B, changing the particle size or packing density changes the amount of fuel component adsorbed per unit volume or the purge gas passage resistance in each layer 31A, 31B. You may let them. The end surfaces 31a and 31b of the adsorption layer 31 are formed in a uniform plane orthogonal to the passage direction of the purge gas, and the path length in the passage direction of the adsorption layer 31 is constant.

  According to the purge buffer device 3 of the present embodiment, the passage characteristics of the fuel component in the adsorption layer 31 continuously change in accordance with the proportions occupied by the first layer 31A and the second layer 31B in the purge gas passage direction. That is, since the first layer 31A occupies substantially the entire adsorption layer 31 at the upper end of the adsorption layer 31, the fuel component passes through the latest, and the proportion of the second layer 31B increases toward the lower end of the adsorption layer 31. The passage of fuel components is gradually accelerated. For this reason, a part of the fuel component of the purge gas introduced from the inlet port 32 passes through the inside of the apparatus prior to others and flows out from the outlet port 33. Therefore, the concentration of the purge gas flowing out from the outlet port 33 can be gradually increased at the initial stage of introduction of the purge gas. The purge buffer device 3 of the present embodiment is an embodiment in which a flow adjustment structure is realized by changing the configuration of the adsorption layer 31 in a direction intersecting the purge gas passage direction to set the purge gas passage resistance non-uniformly. It corresponds to. The boundary surface 31e only needs to have an inclination in an oblique direction with respect to the purge gas passage direction, and may be curved or stepped.

(10th form of purge buffer apparatus)
The purge buffer device according to the tenth embodiment realizes a flow adjustment structure by restricting the inflow of purge gas to a part of the end surface 31a on the inlet side of the adsorption layer 31 as compared with other parts of the end surface 31a. Another example. FIG. 16 shows an example of the purge buffer device 3 according to the tenth embodiment. In the purge buffer device 3 of FIG. 16, a protrusion 32 a to the inside of the case 30 is provided at the tip of the inlet port 32. The protruding portion 32a is tubular, and its diameter is smaller than that of the end surface 31a on the inlet side of the adsorption layer 31. By providing such a protrusion 32a, a part of the purge gas flowing into the case 30 from the inlet port 32 moves linearly toward the outlet port 33 along the center line of the inlet port 32, while The other part wraps around from the projecting portion 32a to the outer peripheral side, and stagnation occurs in the flow. As a result, the flow rate or flow rate of the purge gas flowing into the adsorption layer 31 is large at the central portion and small at the outer peripheral portion. As a result, even if the adsorption layer 31 has a substantially constant adsorption capacity over the entire area, the fuel component in the purge gas is shorter in the central portion than in the outer peripheral portion of the adsorption layer 31 in a shorter time. Go through. Therefore, in the initial stage of introduction of the purge gas, a part of the fuel component of the purge gas introduced from the inlet port 32 passes through the inside of the apparatus and flows out from the outlet port 33, and as a result, in the initial stage of introduction of the purge gas. The concentration of the purge gas flowing out from the outlet port 33 gradually increases as shown by the solid line A in FIG.

  As a means for restricting the inflow of the purge gas to a part of the inlet side end face 31 a of the adsorption layer 31, any appropriate means other than the protruding portion 32 a of the inlet port 32 can be adopted. For example, for example, the inlet port 32 is configured in the same manner as in the first embodiment (FIG. 2), and a ring-shaped deflecting plate is disposed around the opening to deflect part of the purge gas to the outer peripheral side. May be.

(Eleventh form of purge buffer device)
The purge buffer device of the eleventh embodiment is common to the fourth embodiment (FIG. 8) in that a flow adjustment structure is realized by providing a bypass passage that penetrates the adsorption layer, but at least a part of the bypass passage is provided. The difference is that it is directed in a direction that intersects the direction of passage of the purge gas. FIG. 17 shows an example of the purge buffer device 3 according to the eleventh embodiment. In the purge buffer device 3 of FIG. 17, a bypass path 36 that penetrates the adsorption layer 31 between both end faces 31 a and 31 b is provided. The bypass passage 36 extends from the end face 31a on the inlet port 32 side to the end face 31b on the outlet port 33 side while repeating meandering in a direction orthogonal to the purge gas passage direction. At the position where the bypass passage 36 penetrates the adsorption layer 31 in the purge gas passage direction, the purge gas passage resistance is non-uniform in the direction orthogonal to the passage direction. On the wall surface of the bypass path 36, the adsorbent constituting the adsorption layer 31 is exposed over the entire length of the bypass path 36.

  According to the purge buffer device 3 of the present embodiment, a part of the fuel component in the purge gas flowing from the inlet port 32 passes through the bypass path 36 without reaching the adsorption layer 31 and reaches the outlet port 33, and other purge gases Is directed toward the outlet port 33 while being adsorbed by the adsorption layer 31. Accordingly, at the initial stage when the introduction of the purge gas is started, a part of the fuel component in the purge gas flows out from the outlet port 33 ahead of others, and the purge gas concentration gradually rises as in the fourth embodiment. . Furthermore, since the flow path length of the bypass path 36 is longer than that of the fourth embodiment, the contact area between the bypass path 36 and the purge gas passing therethrough is increased to reduce the amount of adsorption of the fuel component to the adsorption layer 31. Thus, the concentration of the purge gas in the initial stage can be further reduced.

  Note that the bypass path 36 of the present embodiment is not limited to meandering, and the shape thereof can be changed as appropriate. For example, as shown in FIG. 18, the bypass path 36 may be provided so as to penetrate the adsorption layer 31 obliquely with respect to the purge gas passage direction. In the example of FIG. 18, the bypass path 36 is not limited to linearly extending in an oblique direction, and at least a part thereof may be a curved section or a section that bends in a staircase shape. In addition, the bypass path 36 may be extended in various directions with respect to the purge gas passage direction.

(Twelfth form of purge buffer device)
In the purge buffer device according to the twelfth embodiment, a plurality of adsorption layers 31 are arranged at intervals from each other along the purge gas passage direction. FIG. 19 shows an example of the purge buffer device 3 according to the twelfth embodiment. In the purge buffer device 3 of FIG. 19, two adsorption layers 31 are provided inside the case 30 with respect to the purge gas passage direction. Moreover, a diffusion chamber 37 from which the adsorbent is excluded is provided between the adsorption layers 31. In addition, both end surfaces 31a and 31b of each layer 31 are formed in the plane orthogonal to the passage direction of purge gas. In each adsorption layer 31, the adsorbents are of the same type, and the packing density is substantially uniform over the entire area of the adsorption layer 31.

  In the purge buffer device 3 of the present embodiment, the flow rate of the purge gas is affected by the viscous resistance of the wall surface of the case 30 at the outer periphery even when the same type of adsorbent is filled in the upstream adsorption layer 31. As a result, the moving speed of the fuel component in the purge gas increases as it goes from the outer periphery to the center of the adsorption layer 31 as indicated by the one-dot chain line in the figure. Accordingly, in the initial stage of introduction of the purge gas, the fuel component is discharged earlier from the central portion of the end surface 31b of the upstream adsorption layer 31. And the fuel component discharged | emitted from the center part of the end surface 31b diffuses in the diffusion chamber 37, and flows in into the whole region of the end surface 31a of the adsorption layer 31 of a downstream side. Then, the fuel component similarly moves in the downstream adsorption layer 31, so that a smaller amount of the fuel component is discharged from the central portion of the end surface 31 b of the downstream adsorption layer 31 ahead of the outer peripheral portion. Accordingly, the purge gas concentration flowing out from the outlet port 33 in the initial stage of introduction of the purge gas can be greatly reduced, and the purge gas concentration can be gradually increased. Note that the adsorption layer is not limited to two layers, and three or more adsorption layers may be provided.

(Thirteenth form of purge buffer device)
The purge buffer device of the thirteenth embodiment is different from the fourth embodiment (FIG. 8) and the ninth embodiment (FIGS. 17 and 18) in that the flow adjustment structure is realized by providing a bypass passage that penetrates the adsorption layer. Although it is common, it is different in the point which provided the constriction part in the bypass. FIG. 20 shows an example of the purge buffer device 3 according to the thirteenth embodiment. In the purge buffer device 3 of FIG. 20, a bypass path 38 extending in the purge gas passage direction is provided on the center line of the adsorption layer 31. The wall surface of the bypass path 38 is in contact with the adsorbent constituting the adsorption layer 31 so that the fuel component can flow between the adsorption layer 31 and the bypass path 38. A constricted portion 38a is formed in the downstream portion of the bypass passage 38 by narrowing the diameter.

  According to the purge buffer device 3 of the present embodiment, in the initial stage of introduction of the purge gas, a part of the fuel component in the purge gas that has flowed from the inlet port 32 passes through the bypass path 38 without being adsorbed by the adsorption layer 31, and exit port. Since the other purge gas is directed to the outlet port 33 side while being adsorbed by the adsorption layer 31, a part of the fuel component in the purge gas flows out from the outlet port 33 ahead of the other in the initial stage of introduction of the purge gas. As in the fourth embodiment, the purge gas concentration gradually increases. In addition, a venturi effect is produced in the constricted portion 38a, whereby the purge gas flow is stagnated upstream of the constricted portion 38a and the fuel component is adsorbed to the adsorption layer 31, while a pressure drop occurs downstream of the constricted portion 38a. As shown by the arrows in the figure, a suction force acts from the adsorption layer 31 to the bypass passage 38, and a part of the fuel component adsorbed around the constricted portion 31a precedes the other fuel component to the bypass passage 38. And is carried to the exit port 33. Therefore, the purge gas concentration flowing out from the outlet port 33 in the initial stage of introduction of the purge gas can be reduced and the purge gas concentration can be gradually increased. The constricted portion 38a may be provided at a plurality of locations. The position of the bypass path 38 is not limited to the center line of the adsorption layer 31 and may be provided at an appropriate position. The number of bypass paths 38 is not limited to one and may be two or more.

  The present invention is not limited to the above form, and can be carried out in an appropriate form. For example, you may combine each form suitably, such as adding a bypass path further to the structure of FIG. In the above embodiment, the purge buffer device is provided as a separate part from the canister, but the purge buffer device may be incorporated in the canister. 21 and 22 show an example thereof. In this example, a purge buffer chamber 50 is provided in front of the purge port 2 c of the canister 2, and the purge buffer device 3 is incorporated in the canister 2 by providing the adsorption layer 31 in the purge buffer chamber 50. . The purge buffer chamber 50 is divided by a head space 2d in the canister 2 and a partition plate 51. The partition plate 51 is provided with an appropriate number of through holes (not shown) for allowing the purge gas to uniformly flow into the adsorption layer 31. ing. Of course, a gap may be provided between the partition plate 51 and the adsorption layer 31, and the inlet port 32 may be provided in the partition plate 51. In this example, the purge port 2c from the head space 2d functions as a part of the purge path. The purge port 2 c functions as an outlet port of the purge buffer device 3, and the case 4 of the canister 2 is also used as the case of the purge buffer device 3. 21 and 22, the adsorption layer 31 is configured as shown in FIG. 4, but the purge buffer device 3 having various configurations described above can be incorporated in the purge buffer chamber 50.

The figure which shows the evaporative fuel processing apparatus for internal combustion engines which concerns on one form of this invention. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 1st form. The figure which shows the mode of the density | concentration change of the purge gas discharged | emitted from a purge buffer apparatus with a comparative example. Sectional drawing which shows the other example of the purge buffer apparatus which concerns on a 1st form. Sectional drawing which shows the further another example of the purge buffer apparatus which concerns on a 1st form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 2nd form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 3rd form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 4th form. The figure which shows the mode of the density | concentration change of the purge gas discharged | emitted from the purge buffer apparatus which concerns on a 4th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 5th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 6th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 7th form. Sectional drawing which shows the other example of the purge buffer apparatus which concerns on a 7th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on an 8th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 9th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 10th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 11th form. Sectional drawing which shows the other example of the purge buffer apparatus which concerns on an 11th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 12th form. Sectional drawing which shows an example of the purge buffer apparatus which concerns on a 13th form. Sectional drawing which shows the structure which incorporated the purge buffer apparatus in the case of the canister. The figure which expands and shows the XXII part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Evaporative fuel processing apparatus 2 Canister 2a Vapor port 2b Atmospheric port 2c Purge port 3 Purge buffer apparatus 4 Canister case 5 Canister adsorption layer 11 Purge path 12 Internal combustion engine 16 Purge valve 30 Purge buffer apparatus case 30a Case expansion part 31 Purge Buffer layer adsorption layer 31a Inlet side end face 31b Outlet side end face 31c Stepped part 31d Recessed part 31e Interface 32 Inlet port 32a Inlet port protruding part 33 Outlet port 34 Filters 35, 36, 38 Bypass path 37 Diffusion chamber 38a Constricted part

Claims (25)

The purge buffer device is disposed in a purge path that guides the purge gas discharged from the adsorption layer in the canister to the intake system of the internal combustion engine, and temporarily adsorbs the fuel component in the purge gas by the adsorption layer arranged in the case. And
A flow adjusting structure for generating a passage characteristic in the case such that a part of the fuel component in the purge gas passes through the case in advance at the initial stage when introduction of the purge gas into the case is started; A purge buffer device for an internal combustion engine, comprising:   The purge buffer device according to claim 1, wherein the flow adjustment structure is realized by providing a non-uniform configuration to the adsorption layer in the case.   The purge buffer device according to claim 2, wherein a path length of the adsorption layer in the case with respect to a passage direction of the purge gas in the case is set non-uniformly in a direction orthogonal to the passage direction.   The path length is set non-uniformly by providing a slope that is inclined obliquely with respect to a stepped portion or the passing direction on an end surface on the outlet side of the adsorption layer in the case. 4. The purge buffer device according to 3.   4. The purge buffer device according to claim 3, wherein the path length is set non-uniformly by providing a recess in an end face of the adsorption layer in the case on the inlet side of the case. 5.   The path length is set to be non-uniform by forming each of both end faces of the adsorption layer in the case so as to protrude toward the center of each end face or to be depressed. 4. The purge buffer device according to 3.   The configuration of the adsorption layer in the case is set to be non-uniform so that a passage characteristic of the fuel component changes in a direction intersecting a passage direction of the purge gas in the case. Purge buffer device.   The purge buffer device according to claim 7, wherein a configuration of the adsorption layer is set non-uniformly by stacking a plurality of layers having different fuel component passage characteristics in a direction orthogonal to the passage direction.   8. The adsorption layer according to claim 7, wherein a plurality of layers having different fuel component passage characteristics are inclined so that their boundary surfaces are inclined with respect to the passage direction. The purge buffer device as described.   The difference in the adsorption characteristics of the plurality of layers is provided by at least one of the kind, particle size, and packing density of the adsorbent constituting each of the plurality of layers being different from each other. Or the purge buffer device according to any one of 9;   The cross-sectional area of the adsorption layer is set non-uniformly so that the cross-sectional area of the adsorption layer in the case in a direction orthogonal to the passage direction of the purge gas in the case is larger on the downstream side than the upstream side in the passage direction. The purge buffer device according to claim 2, wherein the purge buffer device is provided.   2. The purge buffer device according to claim 1, wherein the flow adjusting means is realized by arranging a plurality of adsorption layers at intervals along the passage direction of the purge gas in the case. 3.   2. The purge buffer according to claim 1, wherein the flow adjusting structure is realized by setting the passage resistance of the purge gas non-uniformly in a cross section orthogonal to the passage direction of the purge gas in the case. apparatus.   The purge buffer according to claim 13, wherein the passage resistance is set non-uniformly by changing the configuration of the adsorption layer in the case in a direction intersecting with the passage direction of the purge gas in the case. apparatus.   15. The passage resistance is set non-uniformly by changing at least one of a kind, a particle size, and a packing density of an adsorbent constituting the adsorbing layer in the case. The purge buffer device as described.   14. The passage resistance is set non-uniformly by providing a filter that contacts the adsorption layer in the case in a part of a range orthogonal to the passage direction. The purge buffer device as described.   14. The purge buffer according to claim 13, wherein the passage resistance is set non-uniformly by providing a bypass path in the case that bypasses the adsorption layer in the case and guides part of the purge gas. apparatus.   18. The adsorbent of the adsorption layer is exposed on at least a part of a wall surface of the bypass path so that a fuel component can flow between the bypass path and the adsorption layer in the case. A purge buffer device according to claim 1.   19. The purge buffer device according to claim 18, wherein the bypass passage penetrates the adsorption layer while meandering in a direction intersecting with a passage direction of the purge gas in the case.   The purge buffer device according to claim 18, wherein the bypass passage penetrates the adsorption layer in an oblique direction with respect to a passage direction of the purge gas in the case.   The purge buffer device according to claim 18, wherein a constricted portion is provided in the bypass path.   The flow adjustment structure is realized by restricting inflow of purge gas into a part of the end face on the inlet side of the adsorption layer in the case as compared with other parts of the end face. Item 2. The purge buffer device according to Item 1.   23. The purge buffer device according to claim 22, wherein a part of an end surface on the inlet side is brought into close contact with an inner surface of the case, thereby restricting an inflow of purge gas to a part of the end surface.   The inlet of the purge gas to a part of the end surface is limited by providing the inlet of the case in a tubular shape projecting into the case and having a smaller diameter than the end surface on the inflow side. Purge buffer device. A canister having an adsorption layer for adsorbing a fuel component in fuel vapor, and a purge valve for opening and closing a purge path connecting a purge gas discharged from the adsorption layer of the canister and an intake system of an internal combustion engine, and adsorbing the canister An evaporative fuel processing apparatus, wherein the purge buffer device according to any one of claims 1 to 24 is connected on a purge path between a layer and the purge valve.

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