BACKGROUND

This application claims the benefit of Japanese Patent Application Number 2019-173330 filed on Sep. 24, 2019, the entirety of which is incorporated by reference.

TECHNICAL FIELD

The disclosure relates to a tool cutting edge measuring device provided for a machine tool, such as a horizontal lathe, used to detect a cutting edge position of a tool and set a tool correction value, and the machine tool that includes the device.

RELATED ART

A machine tool, such as a horizontal lathe and a multitasking machine, performs a work that measures a cutting edge position of a tool mounted to a tool post or a spindle when the tool or a tip is exchanged and compares the cutting edge position with a preliminarily obtained cutting edge position of a reference tool. In a case where both the cutting edge positions differ, a tool correction value is calculated from the difference, and a machining program is corrected based on the calculated tool correction value.

As one of the conventional tool cutting edge measuring devices, JP-A-2011-31368 discloses the following structure. In a vertical lathe, a pair of touch sensors having detection surfaces are disposed on distal ends of a pair of respective arms such that the detection surfaces are opposed. One touch sensor is used for measurement of a tool for inner diameter machining (hereinafter referred to as “inner diameter tool” in this specification), and the other touch sensor is used for measurement of a tool for outer diameter machining (hereinafter referred to as “outer diameter tool” in this specification). Each arm is individually movable between an advance position where the arm advances to a machining chamber and holds the touch sensor at a detecting position of a cutting edge and a retracted position where the touch sensor is retracted from the inside of the machining chamber.

With the tool cutting edge measuring device of JP-A-2011-31368, since the arm is taken into and out from a space between a wall of the machining chamber and a workpiece, depending on a size of the space, a long tool possibly causes the ram to interfere with the wall or the workpiece. Accordingly, the length required for the tool possibly cannot be ensured.

The problem similarly occurs in the horizontal lathe as well.FIG. 4illustrates a tool cutting edge measuring device20disposed in a horizontal lathe1. The tool cutting edge measuring device20includes an arm21configured to turn between an advance position to an inside of a machining chamber2and a retracted position where the arm21stands up along a wall7of the machining chamber2. A touch sensor22is mounted to a distal end of the arm21extending in an X-axis positive direction.

When an inner diameter tool23disposed on a tool post5is measured by advancing the arm21in the tool cutting edge measuring device20, a distance D between the tool post5and a tailstock4in a Z-axis direction is short. Accordingly, when the inner diameter tool23is long, the tool post5moving in the Z-axis positive direction possibly interferes with the tailstock4, and after all, the required tool length cannot be ensured.

Therefore, an object of the disclosure is to provide a tool cutting edge measuring device and a machine tool that avoid an interference with a structure inside a machine regardless of a type of a tool, allow measurement of a cutting edge, and allow ensuring a required tool length.

SUMMARY

In order to achieve the above-described object, there is provided a tool cutting edge measuring device according to a first aspect of the disclosure. The tool cutting edge measuring device is mounted to a machine tool. The machine tool is capable of relatively positioning a tool post in a Z-axis direction as a spindle axial direction. It is also capable of relatively positioning a tool post in an X-axis direction as a moving direction for cutting a workpiece and the X-axis direction is orthogonal to the Z-axis direction. The tool cutting edge measuring device includes contact type sensors and an arm. The sensors are configured to measure cutting edge positions of tools in a machining chamber. The arm is movable between an advance position and a retracted position. The arm advances into the machining chamber at the advance position. The arm retracts from the machining chamber at the retracted position. The arm has distal ends provided with two branching units branched into the X-axis direction and the Z-axis direction at the advance position. The sensors are mounted to the respective branching units.

In a disclosure according to a second aspect of the disclosure, which is in the above-described configuration, one of the sensors is configured to measure an inner diameter machining tool of the workpiece, and another sensor is configured to measure an outer diameter machining tool of the workpiece.

In order to achieve the above-described object, there is provided a machine tool according to a third aspect of the disclosure. The machine tool is capable of relatively positioning a tool post in a Z-axis direction as a spindle axial direction. It is also capable of relatively positioning a tool post in an X-axis direction as a moving direction for cutting a workpiece and the X-axis direction is orthogonal to the Z-axis direction. The machine tool includes the tool cutting edge measuring device according to the first aspect or the second aspect.

With the embodiment, the one touch sensor can advance into the machining chamber, and even with the tool having the long protrusion, the tool can be easily brought into abutment with the sensor without the interference with the structure, such as the tailstock, and without the restriction on the stroke. Accordingly, the cutting edge can be measured while the interference with the structure inside the machine can be avoided regardless of the type of the tool, and the required tool length can be ensured.

