WO2016062805A1

WO2016062805A1 - Diesel engine system

Info

Publication number: WO2016062805A1
Application number: PCT/EP2015/074473
Authority: WO
Inventors: Yasutoshi Nanyoshi
Original assignee: Caterpillar Sarl
Priority date: 2014-10-23
Filing date: 2015-10-22
Publication date: 2016-04-28
Also published as: JP2016084715A

Abstract

Object of the Invention: This invention relates to a diesel engine system. The object of this invention is to provide a diesel engine system which can cool a DEF injector even after the engine is stopped. Outline of the Invention: With reference to Fig. 1, the diesel engine system has the following features: The diesel engine system (1) includes a diesel engine (2), a cooling water pump (2a) which is driven by the engine (2), a DEF injector (4) which has an injector cooling line (4a), a shunt tank (6) and a cooling water line (24) which connects the injector cooling line (4a) to the shunt tank (6). An auxiliary tank (26) is disposed in the cooling water line (24), and the auxiliary tank (26) is in a higher position than the shunt tank (6). The cooling water line (24) has a first part (24a) which connects the bottom of the auxiliary tank (26) to the injector cooling line (4a), and has a second part (24b) which connects the top of the auxiliary tank (26) to the shunt tank (6).

Description

DESCRIPTION

DIESEL ENGINE SYSTEM TECHNICAL FIELD

[0001] The present invention relates to a diesel engine system that has a diesel engine and injection means for injecting a reducer into an exhaust passage of the engine.

BACKGROUND ART

[0002] Diesel engines are widely used as the driving sources of vehicles such as construction vehicles, busses and trucks. The exhaust gases of diesel engines contain nitrogen oxides (NOx) and the like in large amounts, due to which a large number of vehicles equipped with diesel engines are subject to emission regulations. The vehicles equipped with diesel engines, therefore, are required to reduce the nitrogen oxides contained in the exhaust gases.

[0003] The urea SCR (Selective Catalytic Reduction) system has been known as a technique for reducing the nitrogen oxide contained in exhaust gas . The urea SCR system reduces the nitrogen oxide of exhaust gas by a reduction reaction of the nitrogen oxide and urea water contained in the exhaust gas. The urea water used as a reducer is stored in a urea water tank equipped in a vehicle, suctioned by a urea water suction pump, and injected into an exhaust passage by injection means connected to the exhaust passage of the engine (see Patent Document 1, for example) .

[0004] Patent Document 1: Japanese Patent Application Laid- open No. 2013-241809

DISCLOSURE OF THE INVENTION

[0005] Because the urea water injection means is connected to the exhaust passage of the engine, there is a possibility that the heat from the exhaust gas might increase the temperature of the injection means to above the heat resistance temperature thereof. In view of this possibility, the injection means is provided with a coolant passage. Some of the coolant of the engine is supplied to this coolant passage, to cool the injection means. The coolant is circulated by a coolant pump that is driven by the engine. Therefore, when the engine is stopped, the coolant pump is also stopped, and consequently the circulation of the coolant is stopped. However, after the engine is stopped, the injection means is no longer cooled by the coolant and is affected by the remaining heat of the exhaust passage that has become hot due to the heat from the exhaust gas, resulting in an increase of the temperature of the injection means to above the heat resistance temperature thereof.

[0006] The present invention was contrived in view of the foregoing circumstances, and a main technical object thereof is to provide a diesel engine system in which reducer injection means can be cooled not only while the engine is running but also after the engine is stopped.

[0007] As a diesel engine system for accomplishing the technical object described above, a first aspect of the present invention provides a diesel engine system that has: a diesel engine provided with an engine coolant passage; a coolant pump driven by the engine; injection means provided with an injection means coolant passage and injecting a reducer into an exhaust passage of the engine; a storage tank for storing a coolant; a first passage connecting the pump to the engine coolant passage; a second passage connecting the engine coolant passage to the storage tank; a third passage connecting the pump to the injection means coolant passage; a fourth passage connecting the injection means coolant passage to the storage tank; and a fifth passage connecting the storage tank to the pump, wherein in the fourth passage an auxiliary tank is disposed at a position higher than that of the storage tank, and the fourth passage has a first portion connecting the injection means coolant passage to a lower end of the auxiliary tank and a second portion connecting an upper end of the auxiliary tank to the storage tank.

[0008] It is preferred that the first portion of the fourth passage be provided with a throttle. It is also preferred that the first portion of the fourth passage be provided with a flow regulating valve. It is favorable that the storage tank and the auxiliary tank are defined by a common tank outer wall. It is preferred that the second portion of the fourth passage be connected to the top of the auxiliary tank and to a position that is located at an upper end side of the storage tank and that is always above the surface of the coolant stored in the storage tank.

[0009] As a diesel engine system for accomplishing the technical object described above, a second aspect of the present invention provides a diesel engine system that has: a diesel engine provided with an engine coolant passage; a coolant pump driven by the engine; injection means provided with an injection means coolant passage and injecting a reducer into an exhaust passage of the engine; a storage tank for storing a coolant; a first passage connecting the pump to the engine coolant passage; a second passage connecting the engine coolant passage to the storage tank; a third passage connecting the pump to the injection means coolant passage; a fourth passage connecting the injection means coolant passage to the storage tank; and a fifth passage connecting the storage tank to the pump, wherein the second passage and the fourth passage merge together and are connected to the storage tank, a junction between the second and fourth passages has an auxiliary tank, which is disposed at a position higher than that of the storage tank, the junction has an upstream portion that connects the engine coolant passage and the injection means coolant passage to an upper end of the auxiliary tank, and a downstream portion that connects the upper end of the auxiliary tank to the storage tank, the diesel engine system further includes an additional passage that connects an upstream side of the injection means coolant passage to a lower end of the auxiliary tank, and an interconnected portion among the third passage, the additional passage and the injection means coolant passage is provided with a shuttle valve that connects the third passage or the additional passage, whichever is a high-pressure passage, to the injection means coolant passage.

[0010] It is preferred that the fourth passage be provided with a throttle. It is also preferred that the fourth passage be provided with a flow regulating valve. It is favorable that the storage tank and the auxiliary tank are defined by a common tank outer wall.

[0011] In the diesel engine system provided by the first aspect of the present invention, while the engine is running, the coolant is discharged from the coolant pump and flows through the first passage and the engine coolant passage to cool the engine, and at the same time this coolant flows through the third passage and the injection means coolant passage to cool the injection means.

[0012] The coolant flowing through the injection means coolant passage is sent to the auxiliary tank through the first portion of the fourth passage. After the coolant is sent to the auxiliary tank, a predetermined amount thereof is stored in the auxiliary tank, while the coolant exceeding the predetermined amount is sent from the upper end of the auxiliary tank to the storage tank through the second portion of the fourth passage. Therefore, while the engine is running, a predetermined amount of coolant is kept in the auxiliary tank .

[0013] Because the auxiliary tank is disposed at a position higher than that of the storage tank, the coolant stored in the auxiliary tank flows from the lower end of the auxiliary tank through the first portion of the fourth passage and the injection means coolant passage to cool the injection means after the engine is stopped. In the diesel engine system according to the first aspect of the present invention, therefore, the reducer injection means is cooled not only while the engine is running but also after the engine is stopped.

[0014] In the diesel engine system provided by the second aspect of the present invention, while the engine is running, the coolant is discharged from the coolant pump and flows through the first passage and the engine coolant passage to cool the engine. Regarding the coolant that is discharged from the coolant pump and flows through the third passage, on the other hand, the water pressure generated by the coolant pump acts within the third passage while the engine is running, making the water pressure within the third passage higher than the water pressure within the additional passage, and, because the third passage and the injection means coolant passage are connected to each other by the shuttle valve, this coolant flows through the injection means coolant passage to cool the injection means.

[0015] The coolant flowing through the engine coolant passage is sent to the auxiliary tank through the second passage and the upstream portion of the junction between the second passage and the fourth passage. The coolant flowing through the injection means coolant passage, on the other hand, is sent to the auxiliary tank through the fourth passage and the upstream portion of the junction between the second passage and the fourth passage. After the coolant is sent to the auxiliary tank, a predetermined amount thereof is stored in the auxiliary tank, while the coolant exceeding the predetermined amount is sent from the upper end of the auxiliary tank to the storage tank through the downstream portion of the junction between the second passage and the fourth passage. Therefore, while the engine is running, a predetermined amount of coolant is kept in the auxiliary tank.

[0016] Because the water pressure generated by the coolant pump no longer acts within the third passage after the engine is stopped and the auxiliary tank is disposed at a position higher than that of the storage tank, the water pressure within the additional passage becomes higher than the water pressure within the third passage, connecting the additional passage and the injection means coolant passage to each other by means of the shuttle valve. As a result, the coolant stored in the auxiliary tank flows through the additional passage and the injection means coolant passage from the lower end of the auxiliary tank, to cool the injection means. In the diesel engine system according to the second aspect of the present invention, therefore, the reducer injection means is cooled not only while the engine is running but also after the engine is stopped.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 is a coolant circuit diagram of a diesel engine system according to a first embodiment of the present invention;

Fig. 2 is a perspective view showing a storage tank and an auxiliary tank according to the first embodiment of the present invention;

Fig. 3(a) is a plan view of the storage tank and the auxiliary tank according to the first embodiment of the present invention, Fig. 3(b) is a front view of the storage tank and the auxiliary tank according to the first embodiment of the present invention, and Fig. 3(c) is a side view of the storage tank and the auxiliary tank according to the first embodiment of the present invention;

Fig. 4(a) is a cross-sectional diagram showing the storage tank and the auxiliary tank that are separated from each other in the horizontal direction on a flat ground, Fig. 4 (b) is a cross-sectional diagram showing the storage tank and the auxiliary tank that are separated from each other in the horizontal direction on a slope, and Fig. 4(c) is a cross- sectional diagram showing the storage tank and the auxiliary tank of Fig. 2 that are placed on a slope;

Fig. 5 is a coolant circuit diagram in which a second passage shown in Fig. 1 is connected to the auxiliary tank;

Fig. 6 is a coolant circuit diagram in which a second portion of a fourth passage shown in Fig. 1 is connected to the top of the auxiliary tank; and

Fig. 7 is a coolant circuit diagram of a diesel engine system according to a second embodiment of the present invention .

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] First and second embodiments of diesel engine systems according to the present invention are now described hereinafter in detail with reference to the accompanying drawings .

[0019] The first embodiment of the diesel engine system according to the present invention is described with reference to Fig. 1. The diesel engine system, the whole of which is denoted with reference numeral 1, has a diesel engine 2 functioning as a driving source, injection means 4 for injecting urea water used as a reducer into an exhaust passage (not shown) of the engine 2, a storage tank 6 for storing a coolant, and a heat exchanger 8 for cooling the coolant.

[0020] A coolant pump 2a for circulating the coolant is disposed in the engine 2. The coolant pump 2a is driven by the engine 2. In addition, an engine coolant passage 2b for cooling the engine 2 is disposed in the engine 2. The engine coolant passage 2b contains coolant passages (not shown) such as an engine jacket for cooling the cylinder block or cylinder head, an engine oil cooler for cooling the engine oil, an EGR (Exhaust Gas Recirculation) cooler for cooling the EGR gas, and a turbocharger coolant passage for cooling the turbocharger .

[0021] The injection means 4 is connected to the exhaust passage of the engine 2 and has an injection means coolant passage 4a that cools the injection means 4 so that the temperature thereof does not exceed the heat resistance temperature thereof by the heat from the exhaust gas or the remaining heat of the exhaust passage.

[0022] The storage tank 6 not only stores the coolant but also separates the air bubbles generated in the coolant or the air trapped in the coolant passage when filling the storage tank with the coolant, from the coolant. The storage tank 6 has a capacity enough to be able to store the amount of coolant to be stored therein while the engine 2 is running and the after-mentioned amount of coolant to be stored in an auxiliary tank 26 while the engine 2 is running.

[0023] The heat exchanger 8 has a top tank 8a into which a hot coolant flows and a heat exchanging component 8b that is connected to a lower portion of the top tank 8a and cools the coolant. The heat exchanging component 8b is configured by a narrow tube, and an outer surface thereof is provided with a plurality of radiation fins (not shown).

[0024] The upstream of the engine coolant passage 2b is connected to the coolant pump 2a by a first passage 10 in the engine 2. One side of the downstream of the engine coolant passage 2b is connected, by a second passage (engine vent passage) 12, to a position that is located at the upper end side of the storage tank 6 and always above the surface of the coolant stored in the storage tank 6. The second passage 12 is provided with a throttle 14. The other side of the downstream of the engine coolant passage 2b is connected to the upstream of the heat exchanger 8 (the top tank 8a) by a heat exchanger inflow passage 16. The second passage 12 is connected to a part of the engine coolant passage 2b that is higher than the position of the heat exchanger inflow passage 16. At the downstream side of the heat exchanger 8, the heat exchanging component 8b is connected to the coolant pump 2a by a pump inflow passage 18 and the top tank 8a is connected, by a heat exchanger vent passage 20, to a position that is located at the upper end side of the storage tank 6 and always above the surface of the coolant stored in the storage tank 6. The heat exchanger vent passage 20 is connected to a part of the heat exchanger 8 that is higher than the pump inflow passage 18.

[0025] The upstream of the injection means coolant passage 4a is connected to the coolant pump 2a by a third passage 22, while the downstream of the injection means coolant passage 4a is connected to the storage tank 6 by a fourth passage 24. The auxiliary tank 26, disposed at a position higher than that of the storage tank 6, is interposed in the fourth passage 24. The fourth passage 24 is provided with a first portion 24a connecting the injection means coolant passage 4a to the lower end of the auxiliary tank 26, and a second portion 24b connecting the upper end of the auxiliary tank 26 to the upper end of the storage tank 6. The first portion 24a is provided with a throttle 28. The lower end of the storage tank 6 is connected to the coolant pump 2a by a fifth passage 30. Furthermore, a ventilation passage 32 is disposed between the upper end of the storage tank 6 and the upper end of the auxiliary tank 26.

[0026] The storage tank 6 and the auxiliary tank 26 are described with reference to Figs. 2 and 3. The storage tank 6 and the auxiliary tank 26 are defined by a common tank outer wall 34, in which the auxiliary tank 26 is formed on the storage tank 6. In other words, the front, rear, left and right side surfaces of the storage tank 6 and the auxiliary tank 26 are covered with the common tank outer wall 34. The upper surface is covered with an upper surface outer wall 36 connected to the upper end of the common tank outer wall 34. The bottom surface is covered with a bottom surface outer wall 38 connected to the lower end of the common tank outer wall 34 The auxiliary tank 26 is also divided by a front inner wall 40 provided at a predetermined distance from an inner surface of a front portion 34a of the common tank outer wall 34, a pair of right and left side inner walls 42 that are each disposed between each end portion of the front inner wall 40 and the inner surface of the front portion 34a of the common tank outer wall 34, a lower end of the front inner wall 40, and a bottom inner wall 44 disposed between the lower end of each of the side inner walls 42 and the inner surface of the common tank outer wall 34.

[0027] Next are described the effects of the first embodiment of the diesel engine system according to the present invention shown in Figs. 1 to 3 described above. In the diesel engine system 1, while the engine 2 is running, the coolant discharged from the coolant pump 2a flows through the first passage 10 and the engine coolant passage 2b to cool the engine 2, and at the same time this coolant flows through the third passage 22 and the injection means coolant passage 4a to cool the injection means 4.

[0028] Most of the coolant flowing through the engine coolant passage 2b flows through the heat exchanger inflow passage 16, is then sent to the heat exchanger 8 and cooled in the heat exchanger 8. Some of the coolant flowing through the engine coolant passage 2b flows through the second passage 12 along with the air bubbles generated in the passages such as the engine coolant passage 2b, and is then sent to the storage tank 6 where the air bubbles are separated from coolant. These coolants flow from the heat exchanger 8 to the pump inflow passage 18 and from the storage tank 6 to the fifth passage 30 and then are suctioned by the coolant pump 2a. Note that some of the coolant sent to the heat exchanger 8 is sent to the storage tank 6 through the heat exchanger vent passage 20.

[0029] The coolant flowing through the injection means coolant passage 4a is sent to the auxiliary tank 26 through the first portion 24a of the fourth passage 24. A predetermined amount of the coolant sent to the auxiliary tank 26 is stored in the auxiliary tank 26, while the coolant exceeding the predetermined amount is sent from the upper end of the auxiliary tank 26 to the storage tank 6 through the second portion 24b of the fourth passage 24. Therefore, a predetermined amount of coolant is kept in the auxiliary tank 26 while the engine 2 is running.

[0030] Since the auxiliary tank 26 is disposed at a position higher than that of the storage tank 6, after the engine 2 is stopped the coolant stored in the auxiliary tank 26 flows from the lower end of the auxiliary tank 26 through the first portion 24a of the fourth passage 24 and the injection means coolant passage 4a, to cool the injection means 4. Therefore, in the diesel engine system 1, the injection means 4 is cooled not only while the engine 2 is running but also after the engine 2 is stopped. The coolant flowing through the injection means coolant passage 4a is sent to the storage tank 6 through the third passage 22, the coolant pump 2a, the fifth passage 30 and the like.

[0031] In the diesel engine system 1, because the first portion 24a of the fourth passage 24 is provided with the throttle 28, the amount of the coolant that flows from the auxiliary tank 26 through the injection means coolant passage 4a can be adjusted after the engine 2 is stopped. Therefore, by adjusting the cross-sectional area of the first portion 24a by means of the throttle 28, the coolant is supplied to the injection means coolant passage 4a for, for example, five minutes after the engine 2 is stopped, during which the temperature of the injection means 4 is not likely to exceed the heat resistance temperature thereof due to the remaining heat of the exhaust passage of the engine 2.

[0032] In considering the case in which the storage tank 6 and the auxiliary tank 26 are separated from each other in the horizontal direction as shown in Fig. 4, when a vehicle or the like equipped with the diesel engine system 1 stops on a flat ground, the water level hi of the auxiliary tank 26 becomes higher than the water level h2 of the storage tank 6 because the auxiliary tank 26 is located higher than the storage tank 6 (Fig. 4a), but when the vehicle or the like stops on a slope, the water level hi of the auxiliary tank 26 becomes lower than the water level h2 of the storage tank 6 (Fig. 4b) . This creates a situation in which the coolant is not supplied from the auxiliary tank 26 to the injection means coolant passage 4a after the engine 2 is stopped.

[0033] However, in the diesel engine system 1, the storage tank 6 and the auxiliary tank 26 are defined by the common tank outer wall 34. Thus, even when the vehicle or the like equipped with the diesel engine system 1 stops on a slope, the water level hi of the auxiliary tank 26 becomes higher than the water level h2 of the storage tank 6 (Fig. 4c) without being affected by this stopping of the vehicle, supplying the coolant from the auxiliary tank 26 to the injection means coolant passage 4a after the engine 2 is stopped.

[0034] The first portion 24a of the fourth passage 24 may be provided with a flow regulating valve in place of the throttle 28. The provision of a flow regulating valve makes the amount of the coolant to be supplied from the auxiliary tank 26 to the injection means coolant passage 4a constant without dropping with a decrease in the water level of the auxiliary tank 26 and until the auxiliary tank 26 becomes empty of the coolant. Moreover, as shown in Fig. 5, the second passage 12 may be disposed in such a manner as to connect the engine coolant passage 2b and the storage tank 6 to each other, with the auxiliary tank 26 and the second portion 24b of the fourth passage 24 therebetween. In so doing, the second passage 12 is connected to a part of the auxiliary tank 26 that is higher than the second portion 24b of the fourth passage 24. Also, in a case where the second portion 24b of the fourth passage 24 is connected to the top of the auxiliary tank 26 and to a position that is located at the upper end side of the storage tank 6 and is always above the surface of the coolant in the storage tank 6, as shown in Fig. 6, the ventilation passage 32 can be omitted.

[0035] The second embodiment of the diesel engine system according to the present invention is now described with reference to Fig. 7. In the second embodiment, the same reference numerals are used to describe the same components as those of the first embodiment described above; thus, the overlapping descriptions are omitted accordingly.

[0036] In the diesel engine system, the whole of which is denoted with reference numeral 100, a second passage (engine vent passage) 102 leading to the storage tank 6 is connected to one side of the downstream of the engine coolant passage 2b The second passage 102 is connected at a part of the engine coolant passage 2b that is higher than the heat exchanger inflow passage 16. The upstream side of the injection means coolant passage 4a is connected to the coolant pump 2a by a third passage 104, and a fourth passage 106 leading to the storage tank 6 is connected to the downstream of the injection means coolant passage 4a. The fourth passage 106 is provided with a throttle 108.

[0037] The second passage 102 and the fourth passage 106 merge together and are connected to the storage tank 6. An auxiliary tank 112, which is disposed at a position higher than that of the storage tank 6, is interposed at a junction 110 between the second passage 102 and the fourth passage 106. The junction 110 has an upstream portion 110a that connects the second and fourth passages 102 and 106 to the upper end of the auxiliary tank 112, and a downstream portion 110b that connects the upper end of the auxiliary tank 112 to the upper end of the storage tank 6. The upstream portion 110a is provided with a throttle 114. The upstream portion 110a is connected to a part of the auxiliary tank 112 that is higher than the downstream portion 110b.

[0038] The upstream side of the injection means coolant passage 4a is connected to the lower end of the auxiliary tank 112, not only by the third passage 104 but also by an additional passage 116. The interconnected portion among the third passage 104, the additional passage 116 and the injection means coolant passage 4a is provided with a shuttle valve 118 that selects the third passage 104 or the additional passage 116, whichever is a high-pressure passage, and connects the high-pressure passage to the injection means coolant passage 4a.

[0039] Next are described the effects of the second embodiment of the diesel engine system according to the present invention shown in Fig. 7 described above. In the diesel engine system 100, while the engine 2 is running, the coolant discharged from the coolant pump 2a flows through the first passage 10 and the engine coolant passage 2b to cool the engine 2. Regarding the coolant that is discharged from the coolant pump 2a and flows through the third passage 104, on the other hand, the water pressure generated by the coolant pump 2a acts within the third passage 104 while the engine 2 is running, making the water pressure within the third passage 104 higher than the water pressure within the additional passage 116, and, because the third passage 104 and the injection means coolant passage 4a are connected to each other by the shuttle valve 118, this coolant flows through the injection means coolant passage 4a to cool the injection means 4.

[0040] Most of the coolant flowing through the engine coolant passage 2b flows through the heat exchanger inflow passage 16, is then sent to the heat exchanger 8 and cooled in the heat exchanger 8. Some of this coolant flows through the second passage 102 and the upstream portion 110a of the junction 110 and is sent to the auxiliary tank 112. The coolant flowing through the injection means coolant passage 4a, on the other hand, is sent to the auxiliary tank 112 through the fourth passage 106 and the upstream portion 110a of the junction 110. A predetermined amount of the coolant sent to the auxiliary tank 112 is stored in the auxiliary tank 112, while the coolant exceeding the predetermined amount is sent from the upper end of the auxiliary tank 112 to the storage tank 6 through the downstream portion 110b of the junction 110. Therefore, while the engine 2 is running, a predetermined amount of coolant is kept in the auxiliary tank 112.

[0041] Because the water pressure generated by the coolant pump 2a no longer acts within the third passage 104 after the engine 2 is stopped and the auxiliary tank 112 is disposed at a position higher than that of the storage tank 6, the water pressure within the additional passage 116 becomes higher than the water pressure within the third passage 104, connecting the additional passage 116 and the injection means coolant passage 4a to each other by means of the shuttle valve 118. As a result, the coolant stored in the auxiliary tank 112 flows through the additional passage 116 and the injection means coolant passage 4a from the lower end of the auxiliary tank 112, to cool the injection means 4. In the diesel engine system 100, therefore, the injection means 4 is cooled not only while the engine 2 is running but also after the engine 2 is stopped.

[0042] The fourth passage 106 may be provided with a flow regulating valve in place of the throttle 108. The provision of a flow regulating valve makes the amount of the coolant to be supplied from the auxiliary tank 112 to the injection means coolant passage 4a constant without dropping with a decrease in the water level of the auxiliary tank 112 and until the auxiliary tank 112 becomes empty of the coolant. Moreover, it is preferred that the storage tank 6 and the auxiliary tank 112 be defined by the common tank outer wall 34, as in the configuration described in the first embodiment. EXPLANATION OF REFERENCE NUMERALS

[0043] 1: Diesel engine system (first embodiment) : Diesel engine

a: Coolant pump

b: Engine coolant passage

: Injection means

a: Injection means coolant passage

: Storage tank

0: First passage

2: Second passage

2: Third passage

4: Fourth passage

24a: First portion

24b: Second portion

26: Auxiliary tank

28: Throttle

30: Fifth passage

32 : Ventilation passage

34: Common tank outer wall

100: Diesel engine system (second embodiment)

102: Second passage

104: Third passage

106: Fourth passage

108: Throttle

110: Junction 110a: Upstream portion

110b: Downstream portion

112: Auxiliary tank

114: Throttle

116: Additional passage

118: Shuttle valve

Claims

1. A diesel engine system, comprising:

a diesel engine provided with an engine coolant passage; a coolant pump driven by the engine;

injection means provided with an injection means coolant passage and injecting a reducer into an exhaust passage of the engine ;

a storage tank for storing a coolant;

a first passage connecting the pump to the engine coolant passage ;

a second passage connecting the engine coolant passage to the storage tank;

a third passage connecting the pump to the injection means coolant passage;

a fourth passage connecting the injection means coolant passage to the storage tank; and

a fifth passage connecting the storage tank to the pump, wherein in the fourth passage, an auxiliary tank is disposed at a position higher than that of the storage tank, and

the fourth passage has a first portion connecting the injection means coolant passage to a lower end of the auxiliary tank and a second portion connecting an upper end of the auxiliary tank to the storage tank.

2. The diesel engine system according to claim 1, wherein the first portion of the fourth passage is provided with a throttle .

3. The diesel engine system according to claim 1, wherein the first portion of the fourth passage is provided with a flow regulating valve.

4. The diesel engine system according to any one of claims 1 to 3, wherein the storage tank and the auxiliary tank are defined by a common tank outer wall.

5. The diesel engine system according to any one of claims 1 to 4, wherein the second portion of the fourth passage is connected to a top of the auxiliary tank and to a position that is located at an upper end side of the storage tank and that is always above a surface of the coolant stored in the storage tank.

6. A diesel engine system, comprising:

a storage tank for storing a coolant;

a first passage connecting the pump to the engine coolant passage;

a second passage connecting the engine coolant passage to the storage tank;

a third passage connecting the pump to the injection means coolant passage; a fourth passage connecting the injection means coolant passage to the storage tank; and

a fifth passage connecting the storage tank to the pump, wherein the second passage and the fourth passage merge together and are connected to the storage tank, a junction between the second and fourth passages has an auxiliary tank, which is disposed at a position higher than that of the storage tank,

the junction has an upstream portion that connects the engine coolant passage and the injection means coolant passage to an upper end of the auxiliary tank, and a downstream portion that connects the upper end of the auxiliary tank to the storage tank,

the diesel engine system further includes an additional passage that connects an upstream side of the injection means coolant passage to a lower end of the auxiliary tank, and

an interconnected portion among the third passage, the additional passage and the injection means coolant passage is provided with a shuttle valve that connects the third passage or the additional passage, whichever is a high-pressure passage, to the injection means coolant passage.

7. The diesel engine system according to claim 6, wherein the fourth passage is provided with a throttle.

8. The diesel engine system according to claim 6, wherein the fourth passage is provided with a flow regulating valve.

9. The diesel engine system according to any one of claims 6 to 8, wherein the storage tank and the auxiliary tank are defined by a common tank outer wall.