Abstract: A construction machine includes a centrifugal fan, and a bell mouth arranged on the suction side of the centrifugal fan. The centrifugal fan has a rotatable hub, an annular shroud arranged so as to face the hub and having a suction port, and multiple blades provided between the hub and the shroud. An outlet of the bell mouth is arranged on the radially inner side of the suction port of the shroud. Each blade is formed such that: a leading edge has a convex shape protruding toward a suction surface relative to a line segment linking a connection of the leading edge with the hub and a connection of the leading edge with the shroud; and a vertex of the convex shape of the leading edge is positioned on a radially inner side of a wall surface of the outlet of the bell mouth when the suction side of the centrifugal fan is seen in an axis direction.

Abstract: A construction machine includes a centrifugal fan, and a bell mouth arranged on the suction side of the centrifugal fan. The centrifugal fan has a rotatable hub, an annular shroud arranged so as to face the hub and having a suction port, and multiple blades provided between the hub and the shroud. An outlet of the bell mouth is arranged on the radially inner side of the suction port of the shroud. Each blade is formed such that: a leading edge has a convex shape protruding toward a suction surface relative to a line segment linking a connection of the leading edge with the hub and a connection of the leading edge with the shroud; and a vertex of the convex shape of the leading edge is positioned on a radially inner side of a wall surface of the outlet of the bell mouth when the suction side of the centrifugal fan is seen in an axis direction.

Abstract: A surface acoustic wave resonator includes a quartz substrate with preselected Euler angles and an IDT on the quartz substrate. The IDT includes electrode fingers and excites a stop band upper end mode surface acoustic wave. Inter-electrode finger grooves are provided between the electrode fingers. Assuming a surface acoustic wave wavelength is ?, an electrode finger film thickness is H, an inter-electrode finger groove depth is G, a line occupation rate of convex portions of the substrate between the inter-electrode finger grooves is ?g, and a line occupation rate of the electrode fingers on the convex portions is ?e, 0.0407??G+H; and ?g>?e.

Abstract: A surface acoustic wave resonator includes a quartz crystal substrate with preselected Euler angles, and an IDT that is provided on the quartz crystal substrate, that includes a plurality of electrode fingers, and that excites a stop band upper end mode surface acoustic wave. Inter-electrode finger grooves are provided in the quartz crystal substrate between the electrode fingers in a plan view. When a wavelength of the surface acoustic wave is ?, a first film thickness of the electrode finger is H, and a first depth of the inter-electrode finger groove is G, and when a line occupation rate of convex portions of the quartz crystal substrate disposed between the inter-electrode finger grooves is ?g, and a line occupation rate of the electrode fingers disposed on the convex portions is ?e, the following relationships are satisfied 0.0407??G+H; and ?g>?e.

Abstract: A surface acoustic wave resonator includes a quartz crystal substrate with Euler angles (?1.5°???1.5°, 117°???142°, and 42.79°?|?|?49.57°), and an IDT provided on the quartz crystal substrate that includes a plurality of electrode fingers and excites a stop band upper end mode surface acoustic wave. Inter-electrode finger grooves are provided between the electrode fingers. If a line occupation rate of the convex portions of the quartz crystal substrate disposed between the inter-electrode finger grooves is ?g, and a line occupation rate of the electrode fingers disposed on the convex portions is ?e, ?g>?e and 0.59<?eff<0.73 are satisfied when an effective line occupation rate ?eff of the IDT is an arithmetic mean of the line occupation rate ?g and the line occupation rate ?e.

Abstract: A surface acoustic wave resonator which can realize favorable frequency-temperature characteristics and suppress frequency variations is provided. The surface acoustic wave resonator includes a quartz crystal substrate with Euler angles (?1.5°???1.5°, 117°???142°, and 42.79°?|?|?49.57°), and an IDT that is provided on the quartz crystal substrate, includes a plurality of electrode fingers, and excites a stop band upper end mode surface acoustic wave, wherein inter-electrode finger grooves are provided between the electrode fingers in a plan view, and wherein if a line occupation rate of convex portions of the quartz crystal substrate disposed between the inter-electrode finger grooves is ?g, and a line occupation rate of the electrode fingers disposed on the convex portions is ?e, ?g>?e and 0.59<?eff<0.73 are satisfied in a case where an effective line occupation rate ?eff of the IDT is an arithmetic mean of the line occupation rate ?g and the line occupation rate ?e.