Abstract: A developer includes a toner containing toner particles and a carrier containing carrier particles. The toner particles each include a toner mother particle and external additive particles attached to a surface of the toner mother particle. The external additive particles include first silica particles and spacer particles. The first silica particles have a number average primary particle diameter of at least 10 nm and no greater than 30 nm. The spacer particles have a number average primary particle diameter of at least 32 nm and no greater than 145 nm. The spacer particles in the toner particles have a coverage ratio of at least 2.0% by area and no greater than 40.0% by area. The carrier particles each include a carrier mother particle and strontium titanate particles attached to a surface of the carrier mother particle.

Abstract: Toner particles in a developer include first strontium titanate particles attached to the surface of each toner mother particle thereof. The first strontium titanate particles have a content ratio of 0.3 to 0.9 parts by mass to 100.0 parts by mass of the toner mother particles. In the developer, coat layers of carrier mother particles of first carrier particles contain barium titanate particles and a coating resin including silicone resin. The barium titanate particles have a content ratio of 2 to 47 parts by mass to 100 parts by mass of the coating resin. Second strontium titanate particles attached to the surfaces of the carrier mother particles have a diameter of 15 to 85 nm.

Abstract: A pump has a boost-retarding device which comprises a cylinder communicating between the suction side and the discharge side of the pump. A plunger slidably and reciprocatingly fits into the cylinder and a lead passage communicates between the suction side and the discharge sides which are divided by the plunger. An adjustable spring biases the plunger toward the discharge side, and a valve mechanism cuts off the outflow of a liquid, from the discharge side to the suction side, which outflow occurs responsive to a movement of the plunger toward the suction side.