Mounting structure for EGR valve or EGR tube

Abstract: A mounting structure is provided for an EGR valve or an EGR tube. The EGR valve or the EGR tube is made of stainless steel or cast iron which is high in the physical strength at a high temperature. The EGR valve or the EGR tube is mounted to an intake manifold made of aluminum by means of bolts or stud bolts. The EGR valve or the EGR tube has female threads provided therein into which the bolts or stud bolts are screwed. The intake manifold has through holes provided therein through which the bolts or stud bolts extend.

Description: Background of the Invention Field of the Invention The present invention relates to a mounting structure in which an EGR valve or an EGR tube is mounted to an intake manifold made of aluminum. Description of the Related Art A known EGR (exhaust gas re-circulating system) for decreasing NOx and improving the fuel consumption in an internal engine is shown in Fig. 4. In this system, an exhaust gas introduced from an exhaust manifold 1 to an EGR tube 2 is flow controlled by an EGR valve 3 and is then returned back via an intake manifold 4 to a combustion chamber. The problem is that while the EGR valve 3 is mounted by tightening nuts 6 onto stud bolts 5 implanted to the intake manifold 4, increase in temperature by the exhaust gas at the female threads in the intake manifold 4 into which the stud bolts 5 are screwed may decline the physical strength. Particularly, when the intake manifold 4 is made of aluminum, its physical strength may be declined even to a half by a temperature of almost 250°C hence failing to maintain the axial force of holding the stud bolts 5 and causing leakage of the exhaust gas. For compensation, as shown in an enlarged primary part view of Fig. 5, a cooling water passage 4b is provided adjacent to the female threads 4a in the intake manifold 4 and is connected to water hoses 7 at the outside for supplying a cooling water to cool down the female threads 4a. This will however increase the number of relevant components, the overall weight, and thus the manufacturing cost. In addition, as shown in Fig. 6, a mounting portion 10a of an EGR tube 10 may be joined to the intake manifold 4 made of aluminum with the use of stud bolts 5 and nuts 6. This structure also requires cooling of the female threads for the stud bolts 5 in the intake manifold 4 with cooling water. Summary of the Invention It is an object of the present invention, in view of the above problems, to provide an arrangement comprising an EGR valve or EGR tube, which does not require cooling water passages or water hoses, while rigid mounting can be made without declining the axial force for holding bolts. According to the present invention, there is provided an arrangement comprising an EGR valve or an EGR tube mounted to an intake manifold, wherein the EGR valve or tube is made of a material such as stainless steel or cast iron that is high in physical strength at a high temperature and the intake manifold is made of aluminium or a material relatively low in physical strength at high temperature, and includes bolts; characterized in that the EGR valve or tube has female threads, the intake manifold having through-holes arranged such that said bolt can extend through said through-holes to screw into said female threads. In a preferred embodiment the manifold has the same number of through-holes as there are bolts. The bolt should preferably be a stud bolt. The invention also provides an internal combustion engine including such an arrangement. Accordingly, the bolts or stud bolts may be inserted into the through holes in the aluminum intake manifold and may be screwed into the female threads in the EGR valve or EGR tube. Therefore, the EGR valve or the EGR tube can be fixedly joined to the intake manifold. Because the EGR valve or EGR tube is made of stainless steel or cast iron which is high in the physical strength in a high temperature, the female threads of the EGR valve or the EGR tube maintain the axial force of the bolts or stud bolts not to be declined even when they are exposed to a higher temperature caused by heat of the exhaust gas. Therefore, no leakage of the exhaust gas may be caused. Also, the need of cooling passages or water hoses for cooling the female threads in a conventional manner can be eliminated and both the overall weight and the cost can thus be reduced. Moreover, the space required for the passage or the water hoses is not needed thus making the overall structure compact in size. Brief Description of the Drawings Fig. 1 is an enlarged primary part view showing an EGR valve mounted by bolts to an intake manifold according to a first embodiment of the present invention; Fig. 2 is an exploded view showing an EGR tube mounted to an intake manifold according to a second embodiment of the present invention; Fig. 3 is an exploded view showing the EGR tube mounted by stud bolts to the intake manifold; Fig. 4 is an exploded view showing a conventional mounting structure for mounting an EGR valve to an intake manifold; Fig. 5 is an enlarged view of a mounting area shown in Fig. 4; and Fig. 6 is an exploded view showing a conventional mounting structure for mounting an EGR tube to an intake manifold. Detailed Description of the Preferred Embodiments Embodiments of the present invention will be described referring to the accompanying drawings. Fig. 1 is an enlarged primary part view of a region where an EGR valve 3 is mounted to an equivalent of the intake manifold shown in Fig. 5. More particularly, the EGR valve 3 made of stainless steel or cast iron which is high in the physical strength at a high temperature is mounted to the intake manifold 4 made of aluminum with the use of bolts 8. Thus, the bolts 8 are inserted into through holes 4c formed in the aluminum intake manifold 4 at positions in alignment with female threads 3a provided in the stainless steel or cast iron EGR valve 3. The bolts 8 are then screwed into their corresponding female threads 3a in the EGR valve 3 for tightening the EGR valve 3 to the intake manifold 4. This allows the female threads 3a in the EGR valve 3 to remain high in the physical strength when it is heated up to a higher temperature by the heat of an exhaust gas, so that the bolts 8 can securely be held in the female threads 8 without being loosened or without causing leakage of the exhaust gas. Because the EGR valve 3 is rigidly tightened to the intake manifold 4 with the axial force of the bolts 8 being maintained even at the higher temperature, it is unnecessary to form a cooling water passage in the intake manifold 4 as in the conventional structure. Also, the use of water hoses for supplying cooling water is not needed, thus contributing to decrease the overall weight and to minimize the production cost. Moreover, the space required for connection with the water hoses is not needed, hence making the structure compact in size. Fig. 2 is an exploded view showing the installation of an EGR tube to an intake manifold made of aluminum. As shown in Fig. 2, a mounting portion 10a of the EGR tube 10 is made of stainless steel or cast iron which is high in the physical strength at a high temperature. The mounting portion 10a has female threads provided therein for engaging threaded bolts 8. On the other hand, the aluminum intake manifold 4 has through holes 4c provided therein for receiving the bolts 8. By screwing the bolts 8 into the female threads in the mounting portion 10a of the EGR tube 10, the EGR tube 10 can be fixedly joined to the intake manifold 4, hence eliminating the use of water hoses or the like for cooling. Fig. 3 illustrates a modification where the bolts 8 shown in Fig. 2 are replaced by stud bolts 5 and nuts 6. In this case, the mounting portion 10a of the EGR tube 10 has female threads provided therein, while the intake manifold 4 has through holes 4c provided therein through which the stud bolts 5 can extend. Thus, the stud bolts 5 are inserted into the through holes 4c, screwed at one end into the female threads in the mounting portion 10a of the EGR tube 10, and tightened at the other end with their corresponding nuts 6. As a result, the EGR tube 10 can be fixedly joined to the intake manifold 4.

Claims: An arrangement comprising an EGR valve or an EGR tube (10) mounted to an intake manifold (4), wherein the EGR valve or tube (10) is made of a material such as stainless steel or cast iron that is high in physical strength at a high temperature and the intake manifold (4) is made of aluminium or a material relatively low in physical strength at high temperature, and includes bolts (8); characterized in that the EGR valve or EGR tube (10) has female threads (3a), the intake manifold having through-holes (4c) arranged such that said bolts (8) can extend through said through-holes (4c) to screw into said female threads (3a). An arrangement according to claim 1, wherein the manifold (4) has the same number of through-holes (4c) as there are bolts (8). An arrangement according to either claim 1 or claim 2 wherein the bolt (8) is a stud bolt. An internal combustion engine including an arrangement according to any one of claims 1 to 3.

Inventors: SAGATA MUNEHIRO, SUNAGA YASUO, SAGATA, MUNEHIRO, SUNAGA, YASUO, Sagata, Munehiro, c/o Aichi Kikai Kogyo K.K., Sunaga, Yasuo, c/o Sanoh Kogyo K.K.
Applicants: AICHI MACHINE IND, SAN O IND CO, AICHI KIKAI KOGYO KABUSHIKI KAISHA, SANOH KOGYO KABUSHIKI KAISHA
Application year: 1999
Main classification: F02M25
IPC codes: F02M25, F02M35